- Three thymine/adenine binding modes of the ruthenium complex Λ-[Ru(TAP)2(dppz)]2+ to the G-quadruplex forming sequence d(TAGGGTT) shown by X-ray crystallography
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Λ-[Ru(TAP)2(dppz)]2+ was crystallised with the G-quadruplex-forming heptamer d(TAGGGTT). Surprisingly, even though there are four unique binding sites, the complex is not in contact with any G-quartet surface. Two complexes stabilise cavities formed from terminal T·A and T·T mismatched pairs. A third shows kinking by a TAP ligand between T·T linkages, while the fourth shows sandwiching of a dppz ligand between a T·A/T·A quadruplex and a T·T mismatch, stabilised by an additional T·A base pair stacking interaction on a TAP surface. Overall, the structure shows an unexpected affinity for thymine, and suggests models for G-quadruplex loop binding.
- McQuaid, Kane,Hall, James P.,Baumgaertner, Lena,Cardin, David J.,Cardin, Christine J.
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- Detection of α-synuclein amyloidogenic aggregates in vitro and in cells using light-switching dipyridophenazine ruthenium(II) complexes
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Protein aggregation is the hallmark of a number of neurodegenerative diseases including Parkinson's and Huntington's diseases. There is a significant interest in understanding the molecular mechanisms involved in the self-association and fibrillization of monomeric soluble proteins into insoluble deposits in vivo and in vitro. Probes with novel properties, such as red-shifted emission, large Stokes shifts, and high photostability, are desirable for a variety of protein aggregation studies. To respond to the increasing need for aggregation-responsive compounds suitable to cellular studies, we present a ruthenium(II) dipyridophenazine derivative, [Ru(phen) 2dppz]2+ (phen =1,10-phenanthroline, dppz = dipyrido[3,2-a:2′.3′-c]phenazine), to study aggregation of α-synuclein (αS), which is associated with the development of Parkinson's disease. We demonstrated the use of [Ru(phen)2dppz] 2+ to monitor αS fibril formation in real-time and to detect and quantify αS aggregates in neuroglioma cells, thereby providing a novel molecular tool to study protein deposition diseases in vitro and in vivo.
- Cook, Nathan P.,Kilpatrick, Kiri,Segatori, Laura,Marti, Angel A.
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- Mitochondria specific highly cytoselective iridium(iii)-Cp* dipyridophenazine (dppz) complexes as cancer cell imaging agents
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Cancer is the most incurable pernicious disease to date after cardiovascular disease with an immeasurable rate of mortality. However, effective cancer medication and therapy are still castles in the sky to researchers. Therefore, in search of an appropriate strategy to annihilate cancer, we have designed a set of Ir(iii)-Cp* dipyridophenazine complexes as luminescent anticancer agents combining the cancer inhibiting potency of the planar dipyridophenazine (dppz) moiety through DNA interaction and mitochondrial dysfunction with the wonderful photoluminescence ability and target specificity of iridium metal. Hence, with the synergy of these dual aspects in the same system, we have aspired to emphasize the theranostic approach of cancer treatment in the present study by preparing effective, aqueous-soluble, mitochondria-targeting, highly cytoselective, luminescent, cancer cell-permeable scaffolds, enabling diagnosis as well as the healing of cancer cells in the body. Here, the presence of the cyclopentadienyl (Cp*) moiety in association with the fluorine group has boosted the lipophilic character of the complexes. Also, the cytotoxicity screening of the prepared Cp*Ir(iii)-dipyridophenazine complexes (IrL1-IrL7) against colorectal adenocarcinoma cells (Caco-2) and human epitheloid cervix carcinoma cells (HeLa) clearly identified them as potential anticancer agents and imaging studies unveiled their superb cellular imaging properties. Among them, the complex [(η5-Cp*)IrCl(11-fluorodipyrido[3,2-a:2′,3′-c]phenazine)] (IrL6) achieved the best cytoselectivity. However, the superiority of the anticancer potency of [(η5-Cp*)IrCl(benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine)] (IrL3) was also corroborated by its activity against the most aggressive colorectal carcinoma cell line (HT-29), whereas (η5-Cp*)IrCl(11-(trifluoromethyl)dipyrido[3,2-a:2′,3′-c]phenazine (IrL5) came into the limelight as the best theranostic agent as it showed remarkable cytoselectivity as well as significant cellular imaging properties, endowing it with the highest quantum yield value among all the complexes.
- Roy, Nilmadhab,Sen, Utsav,Ray Chaudhuri, Shreya,Muthukumar, Venkatesan,Moharana, Prithvi,Paira, Priyankar,Bose, Bipasha,Gauthaman, Ashna,Moorthy, Anbalagan
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- Formation of sequence-independent Z-DNA induced by a ruthenium complex at low salt concentrations
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Switched: The metal complex [Ru(dip)2dppz]2+ can induce the transition from B-DNA to Z-DNA and stabilize the Z conformation in aqueous low-salt solution (see scheme; dip=4,7-diphenyl-1,10-phenanthroline, dppz=dipyridophenazine). The transition is sequence-independent (including non-alternating pyrimidine-purine and AT-rich sequences) and was monitored by CD and 2D NMR spectroscopy, AFM, isothermal titration calorimetry, and gel electrophoresis. Copyright
- Wu, Zhiguo,Tian, Tian,Yu, Junping,Weng, Xiaocheng,Liu, Yi,Zhou, Xiang
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- Crystalline ruthenium polypyridine nanoparticles: A targeted treatment of bacterial infection with multifunctional antibacterial, adhesion and surface-anchoring photosensitizer properties
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Photodynamic antibacterial therapy employs nanocomposites as an alternative to traditional antibiotics for the treatment of bacterial infections. However, many of these antibacterial materials are less effective towards bacteria than traditional drugs, either due to poor specificity or antibacterial activity. This can result in needless and excessive drug use in treatments. This paper describes a multifunctional drug delivery nanoparticle (MDD-NP), Sph-Ru-MMT@PZ, based on the nanostructured-form of [Ru(bpy)2dppz] (PF6)2 (Sph-Ru), which has adhesive properties towards its microbial targets as well as surface-anchoring photosensitizer effects. The design and construction of MDD-NP is based on the adhesive properties of the outer layers of montmorillonite (MMT), which allows Sph-Ru-MMT@PZ to successfully reach its bacterial target; the outer layer of the E. coli. In addition, under 670 nm red irradiation therapy (R-IT), the surface-anchoring properties use the photosensitizer phthalocyanine zinc (PZ) to destroy the bacteria by producing reactive oxygen species (ROS) which causes cell lysis of E. coli. More importantly, Sph-Ru-MMT@PZ has no fluorescence response to live E. coli with intact cell membranes but selectively stained and demonstrated fluorescence during membrane damage of early-stage cells as well as exposure of nuclear materials at late-stage of cell lysis. Sph-Ru-MMT@PZ showed beneficial and synergistic anti-infective effects in vivo by inhibiting the E. coli infection-induced inflammatory response and eventually promoting wound healing in mice. This new strategy for high precision antibacterial therapy towards specific targets, provides an exciting opportunity for the application of multifunctional nanocomposites towards microbial infections.
- Yin, Chenyang,Wang, Zekun,Ding, Xiaoyuan,Chen, Xiaoqing,Wang, Jingyuan,Yang, Endong,Wang, Weiyun,Martin, Lisandra L.,Sun, Dongdong
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- A series of [Cu(N-N)(P-P)]BF4 complexes: Luminescence quenching caused by electron-configuration transformation in excited state
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In this paper, we report a series of [Cu(N-N)(P-P)]BF4 complexes based on two phosphorous ligands and three 1,10-phenanthrolin derived diimine ligands, including their syntheses, characterizations, crystal structures. Their photophysical properties were experimentally measured and theoretically analyzed by time-dependent density functional theory (TD-DFT). It is found that the introduction of too many fused phenyl rings into diimine ligand leads to luminescence absence of corresponding [Cu(N-N)(P-P)]+ complexes at room temperature. A detailed analysis suggests that the thermal activated electron-configuration transformation between the [Cu(N-N)(P-P)]+ triplet metal-to-ligand-charge-transfer (3MLCT) state and the lowest lying excited state of its diimine ligand (3LC) is responsible for the luminescence quenching.
- Zhang, Liming,Yue, Shumei,Li, Bin,Fan, Di
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- Synthesis, structures, DNA-binding, cytotoxicity and molecular docking of CuBr(PPh3)(diimine)
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The copper(I) coordination compounds of general formula [CuBr(PPh3)(N^N)] (N^N = 2,2′-bipyridine (1), 1,10-phenanthroline (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-dimethoxy-2,2′-bipyridine (4), 3-(2-pyridyl)-4,5-diphenyl-1,2,4-triazine (5),
- Abdellattif, Magda H.,Alzahrani, Khaled A.,Arshad, Muhammed N.,Asiri, Abdullah M.,Babgi, Bandar A.,Du, Jun,Humphrey, Mark G.,Hussien, Mostafa A.,Mashat, Khlood H.
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- On the development of a new approach to the design of lanthanide-based materials for solution-processed OLEDs
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The targeted design of lanthanide-based emitters for solution-processed organic light-emitting diodes (OLEDs) resulted in obtaining an NIR OLED with one of the highest efficiencies among ytterbium-based solution-processed OLEDs (30 μW W-1). The design was aimed at the combination of high luminescence efficiency with solubility and charge carrier mobility. The latter was achieved thanks to the introduction of the purposefully selected neutral ligands, which combine electron mobility and the ability to sensitize lanthanide luminescence. Besides, the HOMO and LUMO energies and charge carrier mobility of solution-processed thin films of coordination compounds were measured experimentally for the first time, and novel highly luminescent europium-based materials with PLQYs of up to 80% and purely NIR luminescent ytterbium complexes were obtained.
- Kozlov, Makarii I.,Aslandukov, Andrey N.,Vashchenko, Andrey A.,Medvedko, Alexey V.,Aleksandrov, Alexey E.,Grzibovskis, Raitis,Goloveshkin, Alexander S.,Lepnev, Leonid S.,Tameev, Alexey R.,Vembris, Aivars,Utochnikova, Valentina V.
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- Ru(ii) photosensitizers competent for hypoxic cancersviagreen light activation
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A family of five heteroleptic complexes [Ru(C^N)(N^N)2][PF6] (HC^N = methyl 1-butyl-2-arylbenzimidazolecarboxylate; N^N = polypyridine) has been synthesized to act as biologically-compatible green light photosensitizers (PSs) with phototherapeutic indexes (PIs) up to higher than 700 under hypoxia (2% O2) in HeLa cancer cells under short time of irradiation.
- Ballester, Francisco J.,Bautista, Delia,Ortega, Enrique,Ruiz, José,Santana, M. Dolores
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- A luminescent lyotropic liquid-crystalline gel of a water-soluble Ir(III) complex
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In the present study, the synthesis and properties of a novel water soluble Ir(III) complex of formula [(ppy)2Ir(dpq)]CH3CO2 is described, where ppy is the cyclometalated 2-phenylpyridine ligand and dpq the dipyrido[3,2-f:2′,3′-h]quinoxaline used as ancillary ligand. Own to its specific molecular structure, this complex forms highly ordered supramolecular gels in water on a wide range of concentration, from 3 to 14% w/w. The gel phase shows birefringence under cross polarisers that is completely loss when water is removed, evidence of the formation of a true lyotropic liquid-crystalline gel, without the need of an additional gelator. The gel is macroscopically formed of entangled microfibers that can be seen under optical microscope and that display luminescent properties as observed by confocal microscopy. X-Ray diffraction allowed to resolve the structure of the lyotropic mesophase that is formed by columns of complex cations organised in a tetrahedral manner which are in turn arranged in a larger oblique lattice, hence showing a high degree of order. The photophysical properties of the complex in its different state of matter (solid, gel phase and xerogel) are presented and discussed.
- Aiello, Iolinda,Brunelli, Elvira,Crispini, Alessandra,Ghedini, Mauro,Godbert, Nicolas,La Deda, Massimo,Ricciardi, Loredana,Scarpelli, Francesca
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- Ni(II) curcumin complexes for cellular imaging and photo-triggered in vitro anticancer activity
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Nickel(II) complexes [Ni(cur)(L)2](OAc) (1-3) where L is N,N-donor heterocyclic bases namely 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq in 2), dipyrido[3,2-a:2′,3′-c]phenazine (dppz in 3) and Hcur is curcumin were
- Banaspati, Atrayee,Raza, Md Kausar,Goswami, Tridib K.
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- Synthesis, characterization and DNA-binding and DNA-photocleavage studies of two Ru(II) complexes containing two main ligands and one ancillary ligand
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DNA-binding and DNA-photocleavage properties of two Ru(II) complexes, [Ru(L1)(dppz)2](PF6)4 (1) and [Ru(L2)(dppz)2](PF6)4 (2) (L 1 = 5,50′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L2 = 5,5′-di(1- (tributylammonio)methyl)-2,2′- dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine, have been investigated. Experimental results show that the DNA-binding affinity of complex 1 is greater than that of 2, both complexes emit luminescence in aqueous solution, either alone or in the presence of DNA, complex 1 can bind to DNA in an intercalative mode while 2 most likely interacts with DNA in a partial intercalation fashion, and complex 2 serves as a better candidate for enantioselective binding to CT-DNA compared with 1. Moreover, complex 1 reveals higher efficient DNA cleavage activity than 2, during which supercoiled DNA is converted to nicked DNA with both complexes. Theoretical calculations for the two complexes have been carried out applying the density functional theory (DFT) method at the level of the B3LYP/LanL2DZ basis set. The calculated results can reasonably explain the obtained experimental trends in the DNA-binding affinities and binding constants (Kb) of these complexes.
- Sun, Jing,Wu, Shuo,Chen, Huo-Yan,Gao, Feng,Liu, Jie,Ji, Liang-Nian,Mao, Zong-Wan
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- Synthesis, characterization, photophysical and oxygen-sensing properties of a copper(I) complex
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In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(TBT)(POP)]BF4, where TBT and POP stand for 4, 5, 9, 14-tetraaza-benzo[b]-triphenylene and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(TBT)(POP)]BF4 renders a red phosphorescence peaking at 622 nm, with a long excited-state lifetime of 13.2 μs. Density functional calculation reveals that the emission comes from a triplet metal-to- ligandcharge-transfer excited state. We electrospun composite nanofibers of [Cu(TBT)(POP)]BF4 and polystyrene, hoping to explore the possibility of replacing precious-metal-based oxygen sensors with cheap Cu-based ones. The finally obtained samples with average diameter of ~700 nm exhibit a maximum sensitivity of 5.8 toward molecular oxygen with short response/recovery time (5/13 s) due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples. All these results suggest that phosphorescent Cu(I) complexes doped nanofibrous membranes are promising candidates for low-cost and quick-response oxygen-sensing materials. Springer Science+Business Media B.V. 2010.
- Zhou, Chuanqi,Wang, Qingshuang
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- Tuning the electronic properties of dppz-ligands and their palladium(ii) complexes
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New organometallic palladium complexes of the general type [(RR′dppz)Pd(Me)L]n+ (RR′dppz = derivatives of dipyrido[3,2-a:2′,3′-c]phenazine with RR′ = 11-Cl, 11,12-Cl2, 11-CF3, 11-NO2, 11-NH2; L = Cl, 1-methyluracilate (n = 0), pyridine, cytosine, caffeine, or 1-methylcytosine, (all n = 1) were characterised and studied in detail by electrochemical and spectroscopic (NMR, UV/Vis- absorption and emission) methods. EPR spectroscopy and density functional calculations reveal markedly tuneable lowest unoccupied molecular orbitals (LUMO) located at the dppz ligands. Cytotoxicity experiments on HT-29 colon carcinoma and MCF-7 breast cancer cell lines show promising activities for selected compounds.
- Butsch, Katharina,Gust, Ronald,Klein, Axel,Ott, Ingo,Romanski, Marco
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- A gadolinium(III) complex based dual-modal probe for MRI and fluorescence sensing of fluoride ions in aqueous medium and: In vivo
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A novel Gd(iii) complex, Gd(TTA)3-DPPZ, was designed and assembled as a dual-modal probe for the simultaneous fluorescence and magnetic resonance imaging (MRI) detection of fluoride ions in aqueous media and in vivo. In this system, the Gd(iii) center is not only serving as a MRI signal output unit, but also as a binding site for fluoride ions. When appropriate equivalents of fluoride ions were added into the solution of Gd(TTA)3-DPPZ, the replacement of the coordination water led to a decrease of the longitudinal relaxivity (r1) as well as distinct spectroscopic changes, by which MRI/fluorescence dual-modal fluoride ion sensing was achieved. In the presence of fluoride ions, a 2-fold fluorescence emission enhancement of Gd(TTA)3-DPPZ, and a notable decrease of the UV-vis absorption spectrum were observed. The fluorescence detection limit for fluoride ions was established at 70 nM. Gd(TTA)3-DPPZ also exhibits about 75% decrease of the longitudinal relaxivity (r1) upon addition of fluoride ions in aqueous medium. The appropriate blood circulation time of Gd(TTA)3-DPPZ allows its potential application in MRI in vivo. The results demonstrated that Gd(TTA)3-DPPZ could serve as a potential MRI/fluorescence bimodal imaging agent for the specific and high-sensitive sensing of fluoride ions in vivo.
- Wang, Yue,Song, Renfeng,Guo, Ke,Meng, Qingtao,Zhang, Run,Kong, Xiangfeng,Zhang, Zhiqiang
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- Electrocatalytic reduction of CO2 using rhenium complexes with dipyrido[3,2-a:2′,3′-c]phenazine ligands
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A series of rhenium(I) complexes (1–4) with substituted dipyrido[3,2-a:2′,3′-c]phenazine (dppz) ligands were synthesized and analyzed as electrocatalysts for CO2 reduction. Cyclic voltammetry study shows that complexes 1–4 exhibit dppz ligand-based and metal center-based quasi-reversible reductions under N2. Under a CO2 atmosphere, complexes 1–4 exhibit electrocatalytic response consistent with CO2?→?CO reduction with the presence of the gaseous phase product CO confirmed by gas chromatography (GC). Re(2,2′-bpy)(CO)3Br (Lehn catalyst), a benchmark for electrocatalytic reduction of CO2 to CO, was also prepared and tested for electrocatalytic properties for comparison. The results suggest that chemical modification on the dppz ligand leads to interesting electrocatalytic properties and the large conjugation of the dppz ligand can help store multiple electrons and lower the energy barrier for CO2 reduction.
- Liang, Yawei,Nguyen, Minh T.,Holliday, Bradley J.,Jones, Richard A.
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- Minor groove intercalation of Δ-[Ru(Me2phen)2dppz]2+ to the hexanucleotide d(GTCGAC)2
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The metal complex Δ-[Ru(Me2phen)2dppz]2+ (Me2phen = 2,9-dimethyl-1,10-phenanthroline; dppz = dipyrido-[3,2-a:2′,3′-c]phenazine) has been synthesised and its binding to the hexanucleotide d(GTCGAC)2 studied by 1H NMR spectroscopy. The crystal structure of rac-[Ru(Me2phen)2dppz](PF6)2 ·2H2O has been determined. Addition of Δ-[Ru(Me2phen)2dppz]2+ to d(GTCGAC)2 induced significant broadening of the Me2phen and dppz resonances and large upfield shifts of the dppz resonances, consistent with the metal complex binding through intercalation of the dppz ligand. Also indicative of intercalation are the observed upfield shifts of the T2 and G4 imino protons and the 173°C increase in the melting temperature of the hexanucleotide upon addition of the metal complex. NOE cross-peaks from the Me2phen protons were only observed to hexanucleotide minor groove H1′ and H4′/H5′/H5″ protons in NOESY spectra of the hexanucleotide with added metal complex. In addition, NOEs were also observed between the H13/14 protons of the dppz ligand and the hexanucleotide major groove T2methyl and sugar H2′/H2″ protons. From the combined NMR data it is concluded that the dppz-based ruthenium(II) complex Δ-[Ru(Me2phen)2dppz]2+ intercalates from the minor groove of the hexanucleotide mini-duplex d(GTCGAC)2.
- Greguric, Antun,Greguric, Ivan D.,Hambley, Trevor W.,Aldrich-Wright, Janice R.,Collins, J. Grant
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- Excitation Energy Transfer Supported Amplified Charge-Transfer Emission in an Anthracenedicarboxylate- and Bipyridophenazine-Based Coordination Complex
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A highly luminescent tetrameric zinc(II) complex, {[Zn4(adc)3(bpz)6(HCOO)2]·2H2O} (1; adc = 9,10-anthracenedicarboxylate and bpz = bipyridophenazine), was synthesized by a solvothermal technique and characterized by single-crystal X-ray diffraction. The linear tetrameric units extend into three dimensions via π stacking of adc/bpz and bpz/bpz and multiple CH-π interactions. The compound shows strong red emission at 597 nm (λex = 480 nm), which is attributed to charge-transfer (CT) emission within an adc/bpz donor-acceptor pair. This is also supported by density functional theory computations. Interestingly, the CT emission is amplified by energy transfer from another adc linker that is not involved in the CT interaction.
- Prasad, Komal,Samanta, Debabrata,Haldar, Ritesh,Maji, Tapas Kumar
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- Studies on synthesis, characterization, and G-quadruplex binding of Ru(II) complexes containing two dppz ligands
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In this work, the interaction between the guanine-rich single-strand oligomer AG3(T2AG3)3 quadruplex and two Ru(II) complexes, [Ru(L1)(dppz)2](PF6) 4 (1) and [Ru(L2)(dppz)2](PF6) 4 (2) (L1 = 5,5′-di(1-(trimethylammonio)methyl)-2, 2′-dipyridyl cation, L2 = 5,5′-di(1-(triethylammonio) methyl)-2,2′-dipyridyl cation, dppz = dipyrido[3,2-a:2′,3′-c] phenazine), has been studied by UV-Visible, fluorescence, DNA melting, and circular dichroism in K+ buffer. The two complexes after binding to G-quadruplex have shown different DNA stability and fluorescence enhancement. The results show that both complexes can induce the stabilization of quadruplex DNA. ΔTm values of complexes 1 and 2 at [Ru]/[DNA] ratio of 1:1 were 9.4 and 7.0, respectively. Binding stoichiometry along with the quadruplex was investigated through a luminescence-based Job plot. The major inflection points for complexes 1 and 2 were 0.49 and 0.46, respectively. The data were consistent with the binding mode at a [quadruplex]/[complex] ratio of 1:1. In addition, the conformation of G-quadruplex was not changed by the complexes at the high ionic strength of K+ buffer.
- Sun, Jing,An, Yan,Zhang, Li,Chen, Huo-Yan,Han, Yan,Wang, Yu-Jia,Mao, Zong-Wan,Ji, Liang-Nian
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- Synthesis, characterisation and antimicrobial studies of organotin(IV) complexes with 1,10-phenanthroline derivatives
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The synthesis of several diorganotin(IV) dicarboxylate compounds, including acetates and nicotinates as well as diorganotin(IV) dichloride complexes of the ligands phen, dione and dppz were undertaken. Several difficulties in either the syntheses or compl
- Dolan, Niamh,McGinley, John,Stephens, John C.,Kavanagh, Kevin,Hurley, Daniel,Maher, Niall J.
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- Synthesis, characterization and luminescence property of ternary rare earth complexes with azatriphenylenes as highly efficient sensitizers
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A series of novel ternary rare earth complexes showing attractive luminescence properties were prepared with both neutral and anion ligands. Three azatriphenylene neutral ligands, 1,10-phenanthroline (phen), dipyrido [3,2-a: 2′,3′-c] quinoxaline (dpq) and dipyrido [3,2-a: 2′,3′-c] phenazine (dppz) were investigated systematically as sensitizers in the ternary rare earth complexes. Benzoate ions (BA-) and phenoxyacetate ions (POA-) were chosen as anion ligands. The compositions of these complexes were characterized by elemental analysis, rare earth coordination titration, molar conductivity measurement, IR spectroscopy, UV-vis absorption spectroscopy, 1H NMR spectroscopy and TGA-DTA. The luminescence spectra, luminescence decay time and quantum efficiency of the complexes were also studied. The very strong luminescence intensities and rather long luminescence lifetimes (typically > 1.0 ms) were achieved for both Eu 3+ and Tb3+ ternary complexes with phen and dpq as neutral ligands. Moreover, high quantum efficiencies (40-60%) were also obtained for Eu3+ ternary complexes with phen and dpq as neutral ligands.
- Sun, Hui-Juan,Fu, Xiao-Tao,Chu, Hai-Bin,Du, Yan,Lin, Xue-Mei,Li, Xin,Zhao, Yong-Liang
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- Copper phenanthrene oxidative chemical nucleases
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Here we report the synthesis and isolation of a series of bis-chelate Cu2+ phenanthroline-phenazine cationic complexes of [Cu(DPQ)(Phen)]2+, [Cu(DPPZ)(Phen)]2+, and [Cu(DPPN)(Phen)]2+ (where Phen = 1,10-phenanthroline, DPQ = dipyridoquinoxaline, DPPZ = dipyridophenazine, and DPPN = benzo[i] dipyridophenazine). These compounds have enhanced DNA recognition relative to the well-studied chemical nuclease, [Cu(Phen)2]2+ (bis-Phen), with calf thymus DNA binding constants of DPQ and DPPZ agents (~107 M(bp)-1) being the highest currently known for Cu2+ phenanthrene compounds. Complex DNA binding follows DPQ ≈ DPPZ > DPPN > bis-Phen, with fluorescence quenching and thermal melting experiments on poly[d(A-T)2] and poly[d(G-C)2] supporting intercalation at both the minor and major groove. Phenazine complexes, however, show enhanced targeting and oxidative cleavage on cytosine-phosphate-guanine- rich DNA and have comparable in vitro cytotoxicity toward the cisplatin-resistant ovarian cancer line, SKOV3, as the clinical oxidative DNA-damaging drug doxorubicin (Adriamycin). In this study we also describe how a novel "on-chip" method devised for the Bioanalyser 2100 was employed to quantify double-stranded DNA damage, with high precision, by the complex series on pUC19 DNA (49% A-T, 51% G-C). Both DPQ and bis-Phen complexes are highly efficient oxidizers of pUC19, with DPQ being the most active of the overall series. It is apparent, therefore, that oxidative chemical nuclease activity on homogeneous canonical DNA is not entirely dependent on dynamic nucleotide binding affinity or intercalation, and this observation is corroborated through catalytic interactions with the superoxide anion radical and Fenton breakdown of hydrogen peroxide.
- Molphy, Zara,Prisecaru, Andreea,Slator, Creina,Barron, Niall,McCann, Malachy,Colleran, John,Chandran, Deepak,Gathergood, Nicholas,Kellett, Andrew
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- Hydrothermal syntheses of some derivatives of tetraazatriphenylene
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Some derivatives of tetraazatriphenylene can be synthesized readily by a hydrothermal synthetic method. Compared with the traditional technique, this method is effective and simple process, and much high yields of products with higher purity can be harvested. Copyright Taylor & Francis Group, LLC.
- Che, Guangbo,Li, Wenlian,Kong, Zhiguo,Su, Zisheng,Chu, Bei,Li, Bin,Zhang, Zhiqiang,Hu, Zhizhi,Chi, Haijun
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- Dna-binding and cytotoxicity of copper(I) complexes containing functionalized dipyridylphenazine ligands
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A set of copper(I) coordination compounds with general formula [CuBr(PPh3 )(dppz-R)] (dppz-R = dipyrido[3,2-a:2’,3’-c]phenazine (Cu-1), 11-nitrodipyrido[3,2-a:2’,3’-c]phenazine (Cu-2), 11-cyanodipyrido[3,2-a:2’,3’-c]phenazine (Cu-3), dipyrido[3,2-a:2’,3’-c]phenazine-11-phenone (Cu-4), 11,12-dimethyldipyrido[3,2-a:2’,3’-c]phenazine (Cu-5)) have been prepared and characterized by elemental analysis,1H-NMR and31P-NMR spectroscopies as well as mass spectrometry. The structure of Cu-1 was confirmed by X-ray crystallography. The effect of incorporating different functional groups on the dppz ligand on the binding into CT-DNA was evaluated by absorption spectroscopy, fluorescence quenching of EtBr-DNA adducts, and viscosity measurements. The functional groups affected the binding modes and hence the strength of binding affinities, as suggested by the changes in the relative viscosity. The differences in the quenching constants (Ksv) obtained from the fluorescence quenching assay highlight the importance of the functional groups in altering the binding sites on the DNA. The molecular docking data support the DNA-binding studies, with the sites and mode of interactions against B-DNA changing with the different functional groups. Evaluation of the anticancer activities of the five copper compounds against two different cancer cell lines (M-14 and MCF-7) indicated the importance of the functional groups on the dppz ligand on the anticancer activities. Among the five copper complexes, the cyano-containing complex (Cu-3) has the best anticancer activities.
- Alsaedi, Sammar,Babgi, Bandar A.,Abdellattif, Magda H.,Arshad, Muhammad N.,Emwas, Abdul-Hamid M.,Jaremko, Mariusz,Humphrey, Mark G.,Asiri, Abdullah M.,Hussien, Mostafa A.
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- Constructing triplet trap in Eu(III) complexes and corresponding application for halogen fluorescent optical sensing
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In this paper, a series of Eu(III) complexes was designed using 2-thenoyltrifluoroacetone (TTA) as the first ligand, and phenanthroline derivatives as the second ligand. Their molecular structure was analyzed via their single crystals. Detailed photophysical analysis on these Eu(III) complexes suggested that ligand TTA was the major energy transfer antenna for emissive Eu(III). The phenanthroline-derived ligands showed low triplet levels (T1), leading to a reverse energy transfer (triplet trap) from Eu(III) 5D0 to T1 of diamine ligands. This procedure actually compromised emission performance of these Eu(III) complexes. It was found that halogen anions, especially fluorine ion, interacted with these diamine ligands, which heightened triplet level of these diamine ligands. With the elimination of such triplet trap in these Eu(III) complexes, their Eu(III) emission was greatly improved, showing emission turn-on effect. Detailed sensing performance was discussed carefully. Eu(TTA)3Phen showed a down-bending working curve following a two-site model Stern-Volmer equation. Eu(TTA)3DPPZ and Eu(TTA)3DPOX showed linear working curves with good selectivity. In addition to its emission turn-on sensing, Eu(TTA)3DPOX still showed ratiometric sensing. Detailed sensing mechanism was discussed and confirmed.
- Zhao, Yuqing
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- Improving oxygen sensing performance via inner-molecular π-π stacking in a series of phosphorescent Cu(I) complexes
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In this paper, six phosphorescent Cu(I) complexes with three diamine ligands and two phosphorous ligands were prepared. Detailed discussion was performed on these complexes, including single crystals, quantum mechanics theoretical calculation, absorption spectra, emission spectra, emission quantum yields and excited state decay dynamics. Large conjugation planes and π-π stacking were found in these complexes. Their emission was originated from MLCT excited state. Long-lived emissive center was observed due to this MLCT-based decay and the help from π-π stacking. Such long-lived emissive state and the large conjugation planes in these complexes offered enough collision probability with O2 molecules, making themselves potential oxygen sensing probes. These six complexes were then doped into silica supporting matrix MCM-41 spheres. The resulting composite samples and their emission sensing response towards O2 were discussed in detail. The optimal sample showed sensitivity as high as 7.80 with response time of 14 s. A careful discussion between Cu(I) complex molecular structure and sensing performance was performed. It was concluded that both a long lifetime and a large conjugation plane lead to improved sensing sensitivity since they increased the collision probability with O2 molecules. On the other hand, it was found that both sensing response and recovery times were mainly controlled by O2 diffusion in supporting matrix.
- Cheng, Baohai
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- Increased Lipophilicity of Halogenated Ruthenium(II) Polypyridyl Complexes Leads to Decreased Phototoxicity in vitro when Used as Photosensitizers for Photodynamic Therapy
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In the fight against cancer, photodynamic therapy is generating great interest thanks to its ability to selectively kill cancer cells without harming healthy tissues. In this field, ruthenium(II) polypyridyl complexes, and more specifically, complexes with dipyrido[3,2-a:2’,3’-c]phenazine (dppz) as a ligand are of particular interest due to their DNA-binding and photocleaving properties. However, ruthenium(II) polypyridyl complexes can sometimes suffer from low lipophilicity, which hampers cellular internalisation through passive diffusion. In this study, four new [Ru(dppz-X2)3]2+ complexes (X=H, F, Cl, Br, I) were synthesized and their lipophilicity (logP), cytotoxicity and phototoxicity on cancerous and noncancerous cell lines were assessed. This study shows that, counterintuitively, the phototoxicity of these complexes decreases as their lipophilicity increases; this could be due solely to the atomic radius of the halogen substituents.
- Roy, Saonli,Colombo, Elisa,Vinck, Robin,Mari, Cristina,Rubbiani, Riccardo,Patra, Malay,Gasser, Gilles
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p. 2966 - 2973
(2020/07/13)
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- A series of blue-green-yellow-red emitting Cu(I) complexes: Molecular structure and photophysical performance
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In this work, we designed a series of [Cu(N–N)(PPh3)2]BF4 complexes with different optical edge values and emission colors from blue to red, where N–N and PPh3 denoted a diamine ligand and triphenylphosphine, respectively. Six N–N ligands with various conjugation chains (short π chain, modest π chain and long π chain) were selected. A systematical comparison between these Cu(I) complexes was performed, so that the correlation between N–N structure and [Cu(N–N)(PPh3)2] photophysical performance was tentatively discussed. Their single crystal structure was found consistent with literature ones, forming a typical tetrahedral coordination geometry. Density functional theory calculation indicated that their onset electronic transition showed a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Detailed analysis on photophysical parameters suggested that the absorption edge of [Cu(N–N)(PPh3)2]BF4 complex was controlled by conjugation length in diamine ligand. A wide absorption edge needed a short conjugation chain in diamine ligand. Similar tendency was found for their emission spectra. In addition, a long conjugation chain in diamine ligand widened emission spectra obviously. Emission dynamics showed slim correlation with diamine ligand conjugation length since the excited state was controlled mainly by dynamic procedure and steric factor of diamine ligands.
- Zhang, Liming,Zuo, Qinghui
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- Hybrid Organic-Inorganic Coordination Complexes as Tunable Optical Response Materials
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Novel lead and bismuth dipyrido complexes have been synthesized and characterized by single-crystal X-ray diffraction, which shows their structures to be directed by highly oriented π-stacking of planar fully conjugated organic ligands. Optical band gaps are influenced by the identity of both the organic and inorganic component. Density functional theory calculations show optical excitation leads to exciton separation between inorganic and organic components. Using UV-vis, photoluminescence, and X-ray photoemission spectroscopies, we have determined the materials' frontier energy levels and show their suitability for photovoltaic device fabrication by use of electron- and hole-transport materials such as TiO2 and spiro-OMeTAD respectively. Such organic/inorganic hybrid materials promise greater electronic tunability than the inflexible methylammonium lead iodide structure through variation of both the metal and organic components.
- Travis, Will,Knapp, Caroline E.,Savory, Christopher N.,Ganose, Alex M.,Kafourou, Panagiota,Song, Xingchi,Sharif, Zainab,Cockcroft, Jeremy K.,Scanlon, David O.,Bronstein, Hugo,Palgrave, Robert G.
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p. 3393 - 3400
(2016/05/02)
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- A ring metal ruthenium oxide complex and its preparation method and application
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The invention aims at developing a novel DNA (deoxyribonucleic acid) inserting reagent with good antitumor activity. A cyclometalated single-core ruthenium (II) complex is synthetized. The complex is stable in structure; the water-solubility is better than that of a common organic small molecular reagent at present; good DNA transcription inhibitory activity is represented. A cytotoxicity test indicates that the cyclometalated ruthenium (II) complex has significant growth inhibition effects on cancer cells of 11 different tissue parts of a human body; the inhibitory activity is much better than that of cis-platinum.
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- Fe3O4@SiO2-imid-PMAn magnetic porous nanosphere as recyclable catalyst for the green synthesis of quinoxaline derivatives at room temperature and study of their antifungal activities
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An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives catalyzed by Fe3O4@SiO2-imid-PMAn nanoparticles at room temperature is described. This environmentally benign method provides several advantages such as mild reaction conditions, good to excellent yields, short reaction times, simple work-up and catalyst stability, easy preparation, heterogeneous nature and easy separation of the catalyst. Also, nanocatalyst can be easily recovered by a magnetic field and reused for the next reactions for at least 6 times without distinct deterioration in catalytic activity. SEM, BET, DLS and leaching of catalyst after each reaction cycle were investigated. Furthermore, antifungal activity of various derivatives against three phytopathogenic fungi (Alternaria alternata, Pyricularia oryzae, and Alternaria brassicae) was investigated.
- Javidi, Jaber,Esmaeilpour, Mohsen
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p. 409 - 422
(2015/10/28)
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- Mechanochemical Synthesis, Photophysical Properties, and X-ray Structures of N-Heteroacenes
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The described mechanochemical methodology is an example of a proof-of-concept in which solution-based tedious, poor yielding, and difficult syntheses of pyrazaacenes are achieved under solvent-free ball-milling conditions; the method is easy, high yieldin
- Sahoo, Prasit Kumar,Giri, Chandan,Haldar, Tuhin Subhra,Puttreddy, Rakesh,Rissanen, Kari,Mal, Prasenjit
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p. 1283 - 1291
(2016/03/19)
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- Structural and optical properties of new cyclometalated Ru(II) derived compounds
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The electronic spectra of 4 cyclometalated ruthenium compounds built up from cycloruthenated 2-phenylpyridine with monodentate and bidentate ligands, namely 1 [Ru(MeCN)2(phen)(PhPy)]1+ (RDC11), 2 [Ru(phen)2(PhPy)]1+ (RDC34), 3 [Ru(MeCN) 2(PhPy)(dppz)]1+ (RDC11Z), 4 [Ru(bpy)(PhPy)(dppz)] 1+ (RDCbpZ), the last two being newly synthesized, have been recorded and calculated together with that of 5 [Ru(bpy)2(dppz)]2+ (RDNbpZ). Recently synthesized variants of RDC34 where the phenylpyridine ligand is substituted with an electro-attractor or an electro-donor group, 6 [Ru(phen)2(NO2PhPy)]1+ RDC40 and 7 [Ru(phen)2(NH2PhPy)]1+ RDC41 respectively, and the dicationic reference complex [Ru (phen)2(bpy)]2+ (RDN34) have been investigated as well for comparison. The global structures of RDC34 and RDN34 are very similar despite of the substitution of one N atom by one C atom. As expected a shortening of the Ru-C bond as compared to the Ru-N bond is observed. The calculated structures of the investigated complexes point to a rather rigid structure whatever their environment. The introduction of a strong Ru-C bond has a minor effect on the coordination sphere around the metal atom keeping the other Ru-N bonds and bond angles similar, the only noticeable alteration being an increase of the Ru-N bond trans to the Ru-C bond. The experimental spectra are characterized by an intense band in the UV domain centered at 270 nm and corresponding to a strong intra-ligand (IL) absorption. Low-lying MLCT states contribute to a weak shoulder around 370 nm and to a large band between 550 nm and 400 nm. The tail of this band, towards 650 nm, is a characteristic of the cyclometalated complexes. This series of molecules, as other polypyridyl complexes, are characterized by a high density of excited states in the vis/UV energy domain, a large mixing between MLCT/IL and LLCT states in the upper part of the spectrum, and a significant sensitivity to the environment of the IL state localized on the dppz ligands.
- Finck, Sidonie,Issenhuth, Jean-Thomas,Despax, Stéphane,Sirlin, Claude,Pfeffer, Michel,Poidevin, Corentin,Gourlaouen, Christophe,Boeglin, Alex,Daniel, Chantal
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supporting information
p. 248 - 259
(2014/05/06)
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- Study on the synthesis, characterization, photophysical performance and oxygen-sensing behavior of a luminescent Cu(I) complex with large conjugation plane
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In this paper, a diamine ligand of dipyrido[3,2-a:2′,3′-c] phenazine (DPPZ) and its corresponding Cu(I) complex with triphenylphosphine (PPh3) as the phosphorous ligand are synthesized. Full characterization on [Cu(DPPZ)(PPh3)2
- Yang, Wensheng,Yang, Wan,Liu, Weisheng,Qin, Wenwu
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- Syntheses and photoluminescence properties of rhenium(I) complexes based on dipyrido[3,2-a:2',3'-c]phenazine derivatives with carbazole moiety
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Four rhenium(I) complexes ReL1-ReL4 based on dipyrido[3,2-a:2',3'-c]phenazine (L1) and derivatives L 2-L4 ligands (L2: 10,13-dibromodipyrido[3,2-a:2',3'-c] phenazine, L3: 10-bromo-13-carbazolyl-dipyrido[3,2-a:2',3'-c] phenazine, L4: 10,13-dicarbazolyldipyrido[3,2-a:2',3'-c]phenazine) were synthesized and characterized. The Re(I) complexes ReL1-ReL4 show photoluminescent emissions at 556, 582, 637 and 662 nm, respectively, assigned to dp (Re)→p/ (diimine) MLCT phosphorescence in CH2CL 2 solution. The carbazole containing complexes ReL3 and ReL4, as compared to ReL1, exhibit higher luminescence. These observations imply that modification of diimine rhenium(I) carbonyl complexes with carbazole moiety would lead to efficient phosphorescent properties.
- Zhou, Yong-Hui,Wang, Zheng-Mei,Chen, Min-Dong,Guo, Sheng-Li,Zheng, You-Xuan
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p. 958 - 965
(2013/07/28)
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- The importance of cellular localisation of probes: Synthesis, photophysical properties, DNA interactions and cellular imaging properties of rhenium dppz complexes with known cellular localisation vectors
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The synthesis, photophysical properties, DNA binding, DNA cleavage and cellular imaging behaviour of a range of complexes of the type [Re(CO) 3(dppz)(PyR)]+ are reported, where PyR represents a range of substituted pyridines which have previously been studied for cellular localisation of related complexes. Confocal imaging experiments confirm that the complexes retain the variety of cellular localisation behaviour associated with the PyR units in other complexes, and suggest applications as probes for oligonucleotides in specific cellular compartments (e.g. mitochondrial DNA). This study illustrates the importance of considering cellular localisation as a prime consideration in the design of probes for in vivo application. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Thorp-Greenwood, Flora L.,Coogan, Michael P.,Mishra, Lallan,Kumari, Niraj,Rai, Geeta,Saripella, Srikrishna
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scheme or table
p. 64 - 72
(2012/02/06)
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- Luminescent properties of ruthenium(II) complexes with sterically expansive ligands bound to DNA defects
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A new family of ruthenium(II) complexes with sterically expansive ligands for targeting DNA defects was prepared, and their luminescent responses to base pair mismatches and/or abasic sites were investigated. Design of the complexes sought to combine the
- McConnell, Anna J.,Lim, Mi Hee,Olmon, Eric D.,Song, Hang,Dervan, Elizabeth E.,Barton, Jacqueline K.
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p. 12511 - 12520
(2013/01/15)
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- Solvent free synthesis of quinoxalines, dipyridophenazines and chalcones under microwave irradiation with sulfated Degussa titania as a novel solid acid catalyst
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Sulfated TiO2-P25 (Degussa titania) has been prepared by sol-gel method using H2SO4 and characterized by FT-IR, XRD, FE-SEM, EDS, HR-TEM, XPS, DRS and BET surface area measurements. Sulfate loading by H2SO4 increases the Lewis acidity of Degussa tiatania. This catalyst gives an excellent yield with less reaction time and is an inexpensive and easily recyclable solid acid catalyst for the synthesis of quinaxalines, dipyridophenazines and chalcones under microwave irradiation.
- Krishnakumar,Swaminathan
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experimental part
p. 16 - 25
(2011/12/14)
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- A recyclable solid acid catalyst sulfated titania for easy synthesis of quinoxaline and dipyridophenazine derivatives under microwave irradiation
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TiO2SO42, prepared by solgel method has been used for the synthesis of quinoxaline and dipyridophenizine derivatives under microwave irradiation. High-resolution transmission electron microscope (HR-TEM) and atomic force m
- Krishnakumar, Balu,Swaminathan, Meenakshisundaram
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experimental part
p. 1261 - 1266
(2012/01/31)
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- Polyethylene glycol in water: A simple, efficient and green protocol for the synthesis of quinoxalines
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A variety of biologically important quinoxaline derivatives has been efficiently synthesized in excellent yields under extremely mild conditions using PEG-600 and water. This inexpensive, non-toxic, ecofriendly and readily available system efficiently condensed several aromatic as well as aliphatic 1,2-diketones with aromatic and aliphatic 1,2-diamines to afford the products in excellent yield. Polyethylene glycol (PEG) can be recovered and recycled. Indian Academy of Sciences.
- Chavan, Hemant V.,Adsul, Laxman K.,Bandgar, Babasaheb P.
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experimental part
p. 477 - 483
(2012/03/26)
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- Zn2+-K10-clay (clayzic) as an efficient water-tolerant, solid acid catalyst for the synthesis of benzimidazoles and quinoxalines at room temperature
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A very simple, green and efficient protocol is developed in which zinc chloride-exchanged K10-montmorillonite (clayzic) is employed as a Lewis acid catalyst in aqueous media at room temperature for the synthesis of various benzimidazoles and quinoxalines from carbonyl compounds and o-phenylenediamine. Among the various catalysts (including claycop and Zn2+-Y) studied, clayzic produces benzimidazoles and quinoxalines in higher yield, and with a flexible diamine such as ethylenediamine only the bis-Schiff base is formed. Other salient features of this protocol include milder conditions, atom-economy, absence of coupling agents, and no wastes.
- Dhakshinamoorthy, Amarajothi,Kanagaraj, Kuppusamy,Pitchumani, Kasi
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supporting information; experimental part
p. 69 - 73
(2011/02/25)
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- BINUCLEAR RUTHENIUM COMPLEX DYE, RUTHENIUM-OSMIUM COMPLEX DYE, PHOTOELECTRIC CONVERSION ELEMENT USING ANY ONE OF THE COMPLEX DYES, AND PHOTOCHEMICAL CELL
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The present invention relates to a binuclear ruthenium complex dye represented by the following general formula (1-1): wherein R01 represents a linear or branched alkyl group having 2 to 18 carbon atoms; X represents a counter ion; and n repres
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Page/Page column 23
(2011/05/05)
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- An efficient protocol for the green synthesis of quinoxaline and dipyridophenazine derivatives at room temperature using sulfated titania
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Biologically active quinoxalines and dipyridophenazines were efficiently synthesized in excellent yield and less reaction time using inexpensive, easily recyclable sulfated titania (TiO2-SO42-). TiO2-SO42-
- Krishnakumar,Velmurugan,Jothivel,Swaminathan
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experimental part
p. 997 - 1002
(2010/10/03)
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- A recyclable and highly effective sulfated TiO2-P25 for the synthesis of quinoxaline and dipyridophenazine derivatives at room temperature
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Sulfated TiO2-P25 has been prepared using H2SO 4 and used for the synthesis of quinoxaline and dipyridophenazine derivatives. Sulfate loading by H2SO4 increases the Lewis acidity of TiO2-P2
- Krishnakumar,Swaminathan
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experimental part
p. 2572 - 2577
(2010/11/18)
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- PHENAZINE AND QUINOXALINE SUBSTITUTED AMINO ACIDS AND POLYPEPTIDES
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Disclosed herein are non-natural amino acids and polypeptides that include at least one non-natural amino acid, and methods for making such non-natural amino acids and polypeptides. The non-natural amino acids, by themselves or as a part of a polypeptide, can include a phenazine or quinoxaline substituent. Also disclosed herein are non-natural amino acid polypeptides that are further modified post-translationally, methods for effecting such modifications, and methods for purifying such polypeptides.
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Page/Page column 174
(2008/12/07)
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- Spectroscopic and electrochemical properties of cyclopalladated complexes derived from 2,3-diphenylpyrazine
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A comparative study of complexes [Pd(dphpz)(N'N)]PF6 [dphpz - is the deprotonated form of 2,3-diphenylpyrazine; (N'N) is ethylenediamine (En), 2,2'-bipyridine (bpy), o-phenanthroline (phen), dipyrido[a,c]phenazine (dppz), 6,7-dicyanopyrido[f,h]quinoxaline (dicnq)] was made, using 1H NMR, electronic absorption, and emission spectroscopy, and also cyclic voltammetry. Steric interaction of the dphpz- phenyl rings leads to significant proton shielding in the carbanionic moiety of the cyclometallated ligand. Introduction of heterocyclic diimines instead of ethylenediamine decreases the desheilding of the dphpz- protons adjacent to the coordination center. Irrespective of the nature of the N'N ligands, the cyclopalladated complexes are characterized by specific parameters of photo-and electrostimulated electron transfer processes involving the Pd(dphpz) orbitals, namely, by the long-wave absorption band with λmax 395±6 nm and ε (2.2±1.2) × 103 1 mol-1 cm-1, the vibrationally structured low-temperature (77 K) luminescence resulting from the spinforbidden optical transfer from the excited to the ground state of the complex (energy E 00 19.27±0.07 kK, lifetime τ 160±30 μs), and the one-electron electroreduction wave with E 1-(2.0±0.1)V. For the [Pd(dphpz)?(N'N)]+ complexes containing diazine derivatives of phenanthroline (dppz, dicnq), the degradation of the photoexcitation energy from two electronically excited states can occur as isolated process with successive transfer of electrons to the π orbitals localized on the remote moieties: [Pd(dphpz)] and diazine fragments of the N'N ligands.
- Farus,Balashev
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p. 1410 - 1415
(2008/03/27)
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- Spectroscopic and electrochemical properties of dichlorodiimine complexes of Au(III) and Pt(II) with 1,4-diazine derivatives of o-phenanthroline
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A series of dichlorodiimine complexes [M(N∧N)Cl2] z of Au(III) and Pt(II) with 1,4-derivatives of o-phenanthroline [(N∧N) = o-phenanthroline (phen), dipyrido[f,h]quinoxaline (dpq), dipyrido[a,c]phenazine (dppz), 6,7-dicyanodipyrido[f,h]quinoxaline (dicnq)] were prepared and characterized by 1H NMR, electronic absorption, and emission spectroscopy and by cyclic voltammetry. In all the complexes, the 3(π-π*)-type transition is the spin-forbidden transition of the lowest energy, responsible for the luminescence. The longest wave bands in the absorption spectra of the Au(III) and Pd(II) complexes were assigned in accordance with the results of the electrochemical studies to the 1(d*)-and 1(d*)-type transitions, respectively. Pleiades Publishing, Inc., 2006.
- Ivanov,Puzyk,Balashev
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p. 843 - 848
(2008/02/02)
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- Dramatically enhanced fluorescence of heteroaromatic chromophores upon insertion as spacers into oligo(triacetylene)s
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In continuation of a previous study on the modulation of π-electron conjugation of oligo(triacetylene)s by insertion of central hetero-spacer fragments between two (E)-hex-3-ene-1,5-diyne ((E)-1,2-diethynylethene, DEE) moieties (Fig. 1), a new series of trimeric hybrid oligomers (14-18 and 22-24, Fig. 2) were prepared (Schemes 1-3). Spacers used were both electron-deficient (quinoxaline-based heterocycles, pyridazine) and electron-rich (2,2′-bithiophene, 9,9-dioctyl-9H-fluorene) chromophores. With 19-21 (Scheme 4), a series of transition metal complexes was synthesized as potential precursors for nanoscale scaffolding based on both covalent acetylenic coupling and supramolecular assembly. The UV/VIS spectra (Fig. 3) revealed that the majority of spacers provided heterotrimers featuring extended π-electron delocalization. The new hybrid chromophores show a dramatically enhanced fluorescence compared with the DEE dimer 13 and homo-trimer 12 (Fig. 5). This increase in emission intensity appears as a general feature of these systems: even if the spacer molecule is non-fluorescent, the corresponding hetero-trimer may show a strong emission (Table 2). The redox properties of the new hybrid chromophores were determined by cyclic voltammetry (CV) and rotating-disk voltammetry (RDV) (Table 3 and Fig. 5). In each case, the first one-electron reduction step in the hetero-trimers appeared anodically shifted compared with DEE dimer 13 and homo-trimer 12. With larger spacer chromophore extending into two dimensions (as in 14-18, Fig. 2), the anodic shift (by 240-490 mV, Table 3) seems to originate from inductive effects of the two strongly electron-accepting DEE substituents rather than from extended π-electron conjugation along the oligomeric backbone, as had previously been observed for DEE-substituted porphyrins.
- Edelmann, Michael J.,Raimundo, Jean-Manuel,Utesch, Nils F.,Diederich, Francois,Boudon, Corinne,Gisselbrecht, Jean-Paul,Gross, Maurice
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p. 2195 - 2213
(2007/10/03)
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- Spectroscopic and electrochemical studies of a series of copper(I) and rhenium(I) complexes with substituted dipyrido[3,2-a:2′,3′-c]-phenazine ligands
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Copper(I) and rhenium(I) complexes with the ligand dipyrido[3,2,-a:2′,3′-c]phenazine (dppz) and a number of substituted analogues have been synthesized. Their spectroscopic and electrochemical properties have been studied. It is found that the lowest-energy transition for the complexes is metal-to-ligand charge transfer (MLCT) in nature. This has a low ε value. The resonance Raman spectra for the complexes show groups of bands that shift with substitution at the ligand and groups that remain unchanged in wavenumber. Electrochemical reduction of the complexes resulted in the formation of the ligand radical anion species for all but one system. This was confirmed by UV/VIS spectroelectrochemistry. Using resonance Raman spectroelectrochemistry marker bands have been identified for the radical anion species. The excited states of the complexes were studied by excited-state electronic absorption and time-resolved resonance Raman techniques. The former spectra are ambiguous as to the nature of the lowest excited state; however, the latter spectra confirm that this state is ligand-centred for complexes of dppz and its 11-methyl derivative. Complexes with the 11-nitro derivative appear to form excited states that are MLCT in nature.
- Waterland, Mark R.,Gordon, Keith C.,McGarvey, John J.,Jayaweera, Pradeep M.
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p. 609 - 616
(2007/10/03)
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