- Immobilization of bis(bipyridine) BINOL ligands and their use in chiral resolution
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An enantlomerlcally pure bls(blpyrldlne) BINOL ligand was synthesized which was functionalized with an Iodine substituent In Its periphery. Using this halogen function, the ligand was Immobilized on a commercially available polystyrene gel via Suzuki cross-coupling. The functlonallzed gel was found to be effective In the chiral resolution of similar bis(blpyrldlne) ligands based on a Troeger's base core.
- Bunzen, Jens,Kiehne, Ulf,Benkhaeuser-Schunk, Christian,Luetzen, Arne
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- The influence of different spacer lengths on the selectivity of self-assembly processes of bis(bipyridine)-BINOL helicates
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The synthesis and self-assembly behaviour of a series of en-antiomerically pure bis(chelating) ligands is reported. The li-gands differ in the spacer unit between a BINOL core and. two bipyridyl groups as the chelating entities and were found to undergo completely diastereoselective self-assembly to di-nuclear double-stranded helicates with silver(I) salts, as dem-onstrated by NMR and CD spectroscopy and ESI mass spec-trometry. Upon coordination to iron(II) or zinc(II) ions, however, a dramatic loss in the diastereoselectivity of the self-assembly of dinuclear triple-stranded helicates was observed, as a result: of increasing spacer length. In the case of zinc(II), the self-assembly processes were even found, to be nonselec-tive with regard to the composition of the helicates.
- Bunzen, Jens,Hapke, Marko,Luetzen, Arne
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- Cross-π-conjugated enediyne with multitopic metal binding sites
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The synthesis of an enediyne molecule functionlized with different metal coordination sites in a cross-π-conjugated fashion is reported. Using Pd-mediated cross-coupling reactions, 2,2′-bipyridine units were attached at the periphery of diazafluorenemethylidene to obtain a multitopic ligand. UV-vis spectrosopic investigations along with electrochemical analyses reveal electronic communication along the conjugated path reflected in red-shifted absorption spectra and shifts of reduction potentials. The properties of the ligand could be manipulated by coordinating [Ru(bpy)2]2+ fragments at all three coordination spheres of the molecule while the different complexing imine moieties serve as possible coordination sites for various metal centres. This journal is
- Nauroozi, Djawed,Wurster, Benjamin,Faust, Rüdiger
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- Self-assembly of heteroleptic dinuclear metallosupramolecular kites from multivalent ligands via social self-sorting
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A Tr?ger's base-derived racemic bis(1,10-phenanthroline) ligand (rac)-1 and a bis(2,2′-bipyridine) ligand with a central 1,3-diethynylbenzene unit 2 were synthesized. Each of these ligands acts as a multivalent entity for the binding of two copper(I) ions. Upon coordination to the metal ions these two ligands undergo selective self-assembly into heteroleptic dinuclear metallosupramolecular kites in a high-fidelity social self-sorting manner as evidenced by NMR spectroscopy and mass spectrometry.
- Benkh?user, Christian,Lützen, Arne
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- Lowering Electrocatalytic CO2Reduction Overpotential Using N-Annulated Perylene Diimide Rhenium Bipyridine Dyads with Variable Tether Length
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We report the design, synthesis, and characterization of four N-annulated perylene diimide (NPDI) functionalized rhenium bipyridine [Re(bpy)] supramolecular dyads. The Re(bpy) scaffold was connected to the NPDI chromophore either directly [Re(py-C0-NPDI)] or via an ethyl [Re(bpy-C2-NPDI)], butyl [Re(bpy-C4-NPDI)], or hexyl [Re(bpy-C6-NPDI)] alkyl-chain spacer. Upon electrochemical reduction in the presence of CO2 and a proton source, Re(bpy-C2/4/6-NPDI) all exhibited significant current enhancement effects, while Re(py-C0-NPDI) did not. During controlled potential electrolysis (CPE) experiments at Eappl = -1.8 V vs Fc+/0, Re(bpy-C2/4/6-NPDI) all achieved comparable activity (TONco ～25) and Faradaic efficiency (FEco ～94%). Under identical CPE conditions, the standard catalyst Re(dmbpy) was inactive for electrocatalytic CO2 reduction; only at Eappl = -2.1 V vs Fc+/0 could Re(dmbpy) achieve the same catalytic performance, representing a 300 mV lowering in overpotential for Re(bpy-C2/4/6-NPDI). At higher overpotentials, Re(bpy-C4/6-NPDI) both outperformed Re(bpy-C2-NPDI), indicating the possibility of coinciding electrocatalytic CO2 reduction mechanisms that are dictated by tether-length and overpotential. Using UV-vis-nearIR spectroelectrochemistry (SEC), FTIR SEC, and chemical reduction experiments, it was shown that the NPDI-moiety served as an electron-reservoir for Re(bpy), thereby allowing catalytic activity at lower overpotentials. Density functional theory studies probing the optimized geometries and frontier molecular orbitals of various catalytic intermediates revealed that the geometric configuration of NPDI relative to the Re(bpy)-moiety plays a critical role in accessing electrons from the electron-reservoir. The improved performance of Re(bpy-C2/4/6-NPDI)dyads at lower overpotentials, relative to Re(dmbpy), highlights the utility of chromophore electron-reservoirs as a method for lowering the overpotential for CO2 conversion.
- Dubrawski, Zachary S.,Gelfand, Benjamin S.,Koenig, Josh D. B.,Piers, Warren E.,Rao, Keerthan R.,Risko, Chad,Welch, Gregory C.,Willkomm, Janina
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supporting information
p. 16849 - 16864
(2021/10/20)
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- A Paramagnetic NMR Spectroscopy Toolbox for the Characterisation of Paramagnetic/Spin-Crossover Coordination Complexes and Metal–Organic Cages
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The large paramagnetic shifts and short relaxation times resulting from the presence of a paramagnetic centre complicate NMR data acquisition and interpretation in solution. As a result, NMR analysis of paramagnetic complexes is limited in comparison to diamagnetic compounds and often relies on theoretical models. We report a toolbox of 1D (1H, proton-coupled 13C, selective 1H-decoupling 13C, steady-state NOE) and 2D (COSY, NOESY, HMQC) paramagnetic NMR methods that enables unprecedented structural characterisation and in some cases, provides more structural information than would be observable for a diamagnetic analogue. We demonstrate the toolbox's broad versatility for fields from coordination chemistry and spin-crossover complexes to supramolecular chemistry through the characterisation of CoII and high-spin FeII mononuclear complexes as well as a Co4L6 cage.
- Lehr, Marc,McConnell, Anna J.,N?ther, Christian,Paschelke, Tobias,S?nnichsen, Frank D.,Trumpf, Eicke,Vogt, Anna-Marlene
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supporting information
p. 19344 - 19351
(2020/09/01)
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- Metallosupramolecular Architectures Formed with Ferrocene-Linked Bis-Bidentate Ligands: Synthesis, Structures, and Electrochemical Studies
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The self-assembly of ligands of different geometries with metal ions gives rise to metallosupramolecular architectures of differing structural types. The rotational flexibility of ferrocene allows for conformational diversity, and, as such, self-assembly processes with 1,1′-disubstituted ferrocene ligands could lead to a variety of interesting architectures. Herein, we report a small family of three bis-bidentate 1,1′-disubstituted ferrocene ligands, functionalized with either 2,2′-bipyridine or 2-pyridyl-1,2,3-triazole chelating units. The self-assembly of these ligands with the (usually) four-coordinate, diamagnetic metal ions Cu(I), Ag(I), and Pd(II) was examined using a range of techniques including 1H and DOSY NMR spectroscopies, high-resolution electrospray ionization mass spectrometry, X-ray crystallography, and density functional theory calculations. Additionally, the electrochemical properties of these redox-active metallosupramolecular assemblies were examined using cyclic voltammetry and differential pulse voltammetry. The copper(I) complexes of the 1,1′-disubstituted ferrocene ligands were found to be coordination polymers, while the silver(I) and palladium(II) complexes formed discrete [1 + 1] or [2 + 2] metallomacrocyclic architectures.
- Findlay, James A.,McAdam, C. John,Sutton, Joshua J.,Preston, Dan,Gordon, Keith C.,Crowley, James D.
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supporting information
p. 3602 - 3614
(2018/04/06)
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- Synthesis and photophysical properties of ruthenium(ii) polyimine complexes decorated with flavin
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A bipyridine ruthenium(ii) complex (Ru-1) with a flavin moiety connected to one of the bipyridine ligands via an acetylene bond was designed and synthesized, and its photophysical properties were investigated. Compared with the tris(bipyridine) Ru(ii) com
- Guo, Huimin,Zhu, Lijuan,Dang, Can,Zhao, Jianzhang,Dick, Bernhard
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p. 17504 - 17516
(2018/07/06)
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- Reversible Self-Assembly of Water-Soluble Gold(I) Complexes
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The reaction of the gold polymers containing bipyridyl and terpyridyl units, [Au(C≡CC15H10N3)]n and [Au(C≡CC10H7N2)]n, with the water-soluble phosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane gives rise to the formation of four gold(I) alkynyl complexes that self-assemble in water (H2O) and dimethyl sulfoxide (DMSO), through different intermolecular interactions, with an impact on the observed luminescence displayed by the supramolecular assemblies. A detailed analysis carried out by NMR studies performed in different DMSO/deuterated H2O mixtures indicates the presence of two different assembly modes in the aggregates: (i) chain assemblies, which are based mainly on aurophilic interactions, and (ii) stacked assemblies, which are based on Au···π and π···π interactions. These different supramolecular environments can also be detected by their intrinsic optical properties (differences in absorption and emission spectra) and are predicted by the changes in the relative binding energy from density functional theory calculations carried out in DMSO and H2O. Small-angle X-ray scattering (SAXS) experiments performed in the same mixture of solvents are in agreement with the formation of aggregates in all cases. The aromatic units chosen, bipyridine and terpyridine, allow the use of external stimuli to reversibly change the aggregation state of the supramolecular assemblies. Interaction with the Zn2+ cation is observed to disassemble the aggregates, while encapsulating agents competing for Zn2+ complexation revert the process to the aggregation stage, as verified by SAXS and NMR. The adaptive nature of the supramolecular assemblies to the metal-ion content is accompanied by significant changes in the absorption and emission spectra, signaling the aggregation state and also the content on Zn2+.
- Aguiló, Elisabet,Moro, Artur J.,Gavara, Raquel,Alfonso, Ignacio,Pérez, Yolanda,Zaccaria, Francesco,Guerra, Célia Fonseca,Malfois, Marc,Baucells, Clara,Ferrer, Montserrat,Lima, Jo?o Carlos,Rodríguez, Laura
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supporting information
p. 1017 - 1028
(2018/02/14)
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- Catalysis of Michael Additions by Covalently Modified G-Quadruplex DNA
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Enantioselective catalysis utilizing G-quadruplex DNA-based artificial metalloenzymes has emerged as a new approach in the field of aqueous-phase homogeneous catalysis. Recently, a catalytic asymmetric Michael addition employing a covalently modified G-quadruplex in combination with CuII ions has been reported. Here we assess, by systematic chemical variation and using various spectrometric techniques, a variety of parameters that govern rate acceleration and stereoselectivity of the reaction, such as the position of modification, the topology of the quadruplex, the nature of the ligand, the length of the linker between ligand and DNA, the chemical identity of monovalent ions and transition metal complexes. The DNA quadruplex modified at position 10 (dU10) with hexynyl-linked bpy ligand showed twice the initial reaction rate as compared with the DNA strand derivatized at position 12 (dU12). The strikingly different dependence of the stereoselectivity on the linker length, and their different spectroscopic properties indicate large differences in the architecture of the catalytic centers between the dU10-derivatized and the dU12-modified quadruplexes. Upon addition of CuII, both types of bpy-derivatized DNA strands form defined 1:1 Cu–DNA complexes stable enough for mass spectrometric analysis, while the underivatized strands exhibit weak and unspecific binding, correlated with much lower catalytic rate acceleration. Both dU10- and dU12-derivatized quadruplexes could be reused ten times without reduction of stereoselectivity.
- Dey, Surjendu,Rühl, Carmen L.,J?schke, Andres
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supporting information
p. 12162 - 12170
(2017/09/14)
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- Polypyridyl-functionalizated alkynyl gold(i) metallaligands supported by tri- and tetradentate phosphanes
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A series of alkynyl gold(i) tri and tetratopic metallaligands of the type [Au3(CC-R)3(μ3-triphosphane)] (R = 2,2′-bipyridin-5-yl or C10H7N2, 2,2′:6′,2′′-terpyridin-4-yl or C15H10N3; triphosphane = 1,1,1-tris(diphenylphosphanyl)ethane or triphos, 1,3,5-tris(diphenylphosphanyl)benzene or triphosph) and [Au4(CC-R)4(μ4-tetraphosphane)] (R = C10H7N2, C15H10N3; tetraphosphane = tetrakis(diphenylphosphanylmethyl)methane or tetraphos, 1,2,3,5-tetrakis(diphenylphosphanyl)benzene or tpbz, tetrakis(diphenylphosphaneylmethyl)-1,2-ethylenediamine or dppeda) were obtained in moderate to good yields. All complexes could be prepared by a reaction between the alkynyl gold(i) polymeric species [Au(CC-R)]n and the appropriate polyphosphane. An alternative strategy that required the previous synthesis of the appropriate acetylacetonate precursors [Aun(acac)n(μn-polyphosphane)] ("acac method") was assayed, nevertheless only the polyacac derivatives [Au3(acac)3(μ3-triphosphane)] (triphosphane = triphos and triphosph) and [Au4(acac)4(μ4-tetraphos)] could be isolated and characterized. All compounds were characterized by IR, multinuclear NMR spectroscopy and ESI(+) mass spectrometry. The X-ray crystal structure of complexes [Au4(CC-C10H7N2)4(μ4-tetraphos)] and [Au4(CC-C10H7N2)4(μ4-tpbz)] showed the involvement of all the gold atoms in close intramolecular Au?Au contact as well as intermolecular π stacking interactions between the aromatic rings of the polypyridyl ligands. The photophysical properties of the synthesized compounds were carefully studied and used as a probe of their possible use as multidentate ligands for Cu(i) and Zn(ii). The UV-Vis speciation studies of the complexation reactions were conducted via metal titration and, in most cases the dangling units of the ligand were found to behave in a fairy independent manner. While in the case of Cu(i) multiple equilibria exist in solution a single complex is detected for Zn(ii) under the conditions studied.
- Ferrer, Montserrat,Giménez, Leticia,Gutiérrez, Albert,Lima, Jo?o Carlos,Martínez, Manuel,Rodríguez, Laura,Martín, Avelino,Puttreddy, Rakesh,Rissanen, Kari
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p. 13920 - 13934
(2017/10/24)
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- Visible light-harvesting tricarbonyl Re(I) complex: Synthesis and application in intracellular photodynamic effect and luminescence imaging
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Re(I) tricarbonyl rhenium(I) complexes attracted much attention owing to the good cellular uptake ability and rich photophysical properties. However, normally Re(I) complexes show short triplet state lifetime and weak absorption in the visible spectra region, and the absorption wavelength usually is shorter than 450 nm. These features are detrimental to the applications of Re(I) complexes in the areas such as photodynamic therapy (PDT) and luminescence bioimaging. Herein, a novel tricarbonyl rhenium(I) complex Re-1 with strong visible light-absorbing ability (624 nm, ε=5.69×104 L/(mol cm)), long-lived triplet excited state (τ T=448.9 μs) and moderate fluorescence quantum yield (Φ F=41.6%) was prepared. The photophysical properties of Re-1 were studied with steady state UV-Vis absorption and luminescence spectroscopies, nanosecond transient absorption spectroscopy, as well as DFT/TDDFT calculations. Re-1 was used for intracellular PDT and luminescence imaging studies. The results indicate that Re-1 shows low dark toxicity, but it is able to kill cancer cells on illumination with 635 nm LED.
- Zhong, Fangfang,Yuan, Xiaolin,Zhao, Jianzhang,Wang, Quan
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- Chemically and electrochemically induced expansion and contraction of a ferrocene rotor
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A 2,2′-bipyridine-appended ferrocene rotor, 1,1′-di(5-yl-ethynyl-2,2′-bipyridine)ferrocene, can be switched from a folded/stacked (syn) conformation to an extended/unstacked (anti) conformation by the addition of [Cu(CH3CN)4](PF6) and 6,6′-dimesityl-2,2′-bipyridine. This extension and contraction process was completely reversible and could be triggered either chemically or electrochemically.
- Scottwell, Syn?ve ?.,Elliott, Anastasia B. S.,Shaffer, Karl J.,Nafady, Ayman,McAdam, C. John,Gordon, Keith C.,Crowley, James D.
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supporting information
p. 8161 - 8164
(2015/05/20)
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- Green light-excitable naphthalenediimide acetylide-containing cyclometalated Ir(iii) complex with long-lived triplet excited states as triplet photosensitizers for triplet-triplet annihilation upconversion
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Naphthalenediimide (NDI) was connected to the ligand of a cyclometalated Ir(iii) complex (Ir-1) via a CC triple bond to enhance the absorption in the visible region and to access long-lived triplet excited states. Ir(ppy) 2(bpy)[PF6] (Ir-2, ppy = 2-phenylpyridine and bpy = 2,2′-bipyridine) was used as a model complex. The photophysical properties of the complexes were studied with steady state and time-resolved spectroscopy. Ir-1 shows strong absorption in the visible region (ε = 11 000 M -1 cm-1 at 542 nm) and in comparison Ir-2 shows typically weak absorption in the visible region (ε -1 cm -1 above 400 nm). Room temperature near IR emission at 732 nm (ΦP = 0.1%) was observed for Ir-1, which is attributed to the NDI localized emissive triplet excited state, by transient absorption spectra and DFT calculations on the spin density surface. The lifetime of the NDI-localized triplet excited state is up to 130.0 μs, which is rarely reported for Ir(iii) complexes. In comparison, Ir-2 shows phosphorescence at 578 nm and the triplet state lifetime is a typical value of 0.3 μs. The complexes were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion and an upconversion quantum yield of 6.7% was observed with Ir-1. No upconversion was observed with Ir-2 as the triplet photosensitizer at the same experimental conditions.
- Ma, Lihua,Guo, Song,Sun, Jifu,Zhang, Caishun,Zhao, Jianzhang,Guo, Huimin
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p. 6478 - 6488
(2013/07/26)
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- Electrochemiluminescent dinuclear Ru(II) complexes assembled with 1,1′-(1,2-ethynediyl)- or dimethlyene-bridged bis(bipyridine) ligands: Synthesis and photophysical and electrochemical properties
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1,2-Di(2,2′-bipyridin-5-yl)ethane (BL1) and 1,2-di(2,2′- bipyridin-5-yl)ethyne (BL2) were synthesized as new bridging ligands and coordinated to (RuL2(acetone)2)(PF6) 2 for the preparation of various [Ru(L)2(BL)Ru(L) 2](PF6)4-type dinuclear ruthenium complexes (where BL = BL1, BL2 and L = bpy, o-phen, DTDP). The electrochemical redox potentials, spectroscopic properties, and relative electrochemiluminescence intensity of BL1 and BL2 were characterized and compared to those of well-known tris(1,10-phenanthroline)rutheniun(II) [Ru(o-phen)3](PF 6)2] complex as a reference. Dinuclear Ru(II) complexes containing the conjugated bridging ligand (BL2) showed much more intense electrochemiluminescent responses than dinuclear Ru(II) complexes with the non-conjugated bridging ligand (BL1). Among the complexes with conjugated bridging ligands, [(DTDP)2Ru(bpy-CC-bpy)Ru(DTDP)2](PF 6)4 exhibited enhanced ECL intensities as high as 3.6 times greater than that of the reference, [Ru(o-phen)3](PF 6)2.
- Kim, Minki,Kang, Chang Hoon,Hong, Subong,Lee, Won-Yong,Kim, Byeong Hyo
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p. 145 - 150
(2013/05/22)
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- Isolated facial and meridional tris(bipyridine)Ru(ii) for STM studies on Au(111)
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Tripodal facial and meridional Ru(ii) complexes comprising three conjugated legs with acetyl-protected thiol end groups are designed, synthesized and isolated for investigation on a gold surface. Preliminary ultrahigh vacuum scanning tunnelling microscopy
- Schramm, Alexandrina,Stroh, Christophe,D?ssel, Kerrin,Lukas, Maya,Fuhr, Olaf,L?hneysen, Hilbert V.,Mayor, Marcel
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supporting information
p. 1076 - 1078
(2013/02/25)
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- Visible light-absorbing rhenium(i) tricarbonyl complexes as triplet photosensitizers in photooxidation and triplet-triplet annihilation upconversion
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We prepared N^N Re(i) tricarbonyl chloride complexes (Re-1 and Re-2) that give very strong absorption of visible light. To this end, it is for the first time that boron dipyrimethane (Bodipy) was used to prepare Re(i) tricarbonyl chloride complexes. The π-conjugation linker between the π-conjugation framework of the antenna Bodipy and the Re(i) coordination centre ensures efficient intersystem crossing (ISC). Re-0 without visible light-harvesting ligand was prepared as a model complex in the photophysical studies. Re-1 (with Bodipy) and Re-2 (with carbazole-ethynyl Bodipy) show unprecedented strong absorption of visible light at 536 nm (ε = 91700 M-1 cm -1) and 574 nm (ε = 64600 M-1 cm-1), respectively. Interestingly, different from Re-0, Re-1 and Re-2 show fluorescence of the ligand, not the phosphorescence of the Re(i) coordination centre. However, long-lived triplet excited states were observed upon visible light excitation (τT = 104.0 μs for Re-1; τT = 127.2 μs for Re-2) vs. the short lifetime of Re-0 (τT = 26 ns). With nanosecond time-resolved transient absorption spectroscopy and DFT calculations, we proved that the triplet excited states of Re-1 and Re-2 are localized on the Bodipy ligands. The complexes were used as triplet photosensitizers for two triplet-triplet-energy-transfer (TTET) processes, i.e.1O2 mediated photooxidation and triplet-triplet annihilation (TTA) upconversion. With the strong visible light-harvesting ability, Re-1 proved to be a better 1O2 photosensitizer than the conventional triplet photosensitizer tetraphenylporphyrin (TPP). Significant upconversion was observed with Re-1 as the triplet photosensitizer. Our result is useful for preparation of Re(i) tricarbonyl chloride complexes that show strong absorption of visible light and long-lived triplet excited states and for the application of these complexes as triplet photosensitizers in photocatalysis, photodynamic therapy and TTA upconversion. The Royal Society of Chemistry 2013.
- Yi, Xiuyu,Zhao, Jianzhang,Sun, Jifu,Guo, Song,Zhang, Hongli
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supporting information
p. 2062 - 2074
(2013/02/26)
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- Observation of the room temperature phosphorescence of Bodipy in visible light-harvesting Ru(ii) polyimine complexes and application as triplet photosensitizers for triplet-triplet-annihilation upconversion and photocatalytic oxidation
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Two Ru(ii) polyimine complexes containing a boron-dipyrromethene (Bodipy) chromophore were prepared. The two complexes are different in the linker which connects the Bodipy part and the Ru(ii) coordination centre. The Bodipy core and the Ru(ii) centre are in π-conjugation in Ru-1, whereas in Ru-2 the Bodipy part is linked in a non-conjugated way to the Ru(ii) centre. Ru(bpy) 3[PF6]2 (Ru-3) was used as a reference complex. Both Ru-1 and Ru-2 show strong absorption in the visible region (ε = 65200 M-1 cm-1 at 528 nm for Ru-1 and ε = 76700 M -1 cm-1 at 499 nm for Ru-2). The fluorescence of the Bodipy ligands was almost completely quenched in Ru-1 and Ru-2. Ru-1 shows room temperature phosphorescence of the Bodipy chromophore, as well as the residual fluorescence of the Bodipy ligand. Ru-2 shows only the residual fluorescence of the Bodipy ligand. A long-lived Bodipy-localized triplet excited state was observed for both Ru-1 and Ru-2 upon visible light excitation (τT is up to 279.7 μs, the longest T1 state lifetime observed for the Bodipy moiety in the transition metal complex). Application of the complexes in triplet-triplet-annihilation upconversion and singlet oxygen ( 1O2)-mediated photo-oxidation proved that Ru-1 is more efficient (e.g. singlet oxygen quantum yield ΦΔ = 0.93) as a triplet photosensitizer than Ru-2 (ΦΔ = 0.64). Therefore, direct connection of the π-core of the Bodipy chromophore to the coordination centre, i.e. by establishing π-conjugation between the visible light-harvesting chromophore and the metal coordination centre is essential to enhance the effective visible light-harvesting of the Ru(ii) complexes. The Royal Society of Chemistry 2013.
- Wu, Wanhua,Sun, Jifu,Cui, Xiaoneng,Zhao, Jianzhang
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p. 4577 - 4589
(2013/09/23)
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- Design, synthesis, magnetic properties of a π-radical ligand with photo-excited high-spin state and its Fe(ii) complex. the first stage of a new strategy for LIESST materials
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A π-radical ligand (9-[4-(6-oxo-1,5-dimethylverdazyl)phenyl]-10-[5-(2, 2′-bipyridyl)ethynyl]anthracene, L1) with a photo-excited high-spin quartet state (S = 3/2) and its iron(ii) complex [Fe(L 1){H2B(Pz)2}2] (1) {H 2B(Pz)2- = dihydrobis(1-pyrazolyl)borate} were synthesized as a candidate for a new strategy for spin-crossover compounds exhibiting light-induced excited spin state trapping (LIESST), which is via the photo-excited high-spin state of the π-conjugated aromatic system. Control compounds, ligand L2 and [Fe(L2){H2B(Pz) 2}2] (2), in which the verdazyl radical moiety in L 1 was removed, were also synthesized. The photo-excited quartet state of the π-radical ligand L1 was confirmed by the time-resolved ESR technique. Temperature dependence of the magnetic behaviors of 1 and 2 were investigated from 5 K to 350 K, showing spin-crossover transition at T c = 222 K and at Tc = 162 K for complexes 1 and 2, respectively. The transition enthalpies and entropies were determined to be ΔH = 8.09 kJ mol-1 and ΔS = 36.4 J K-1 mol-1 for 1 and to be ΔH = 22.39 kJ mol-1 and ΔS = 138 J K-1 mol-1 for 2. LIESST phenomena were also observed below ca. 50 K for both complexes. The effects of the attachment of radical moiety are discussed based on the results.
- Katayama, Koichi,Hirotsu, Masakazu,Kinoshita, Isamu,Teki, Yoshio
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p. 13465 - 13473
(2013/01/15)
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- Hybrid charged heterometallic Pt-Ir complexes: Tailoring excited states by taking the best of both worlds
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The CC-linkage of Pt(PR3)2(CCAr)2 with (CN)2Ir(NN)+ (CN = 2-phenylpyridine; NN = bipyridyl) leads to hetero-bi- and trimetallic species exhibiting photophysical properties reminiscent of both [Pt]- and [Ir]-containing moieties through the generation of a [Pt] → [Ir] charge transfer excited state. The Royal Society of Chemistry 2012.
- Soliman, Ahmed M.,Fortin, Daniel,Harvey, Pierre D.,Zysman-Colman, Eli
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supporting information; experimental part
p. 1120 - 1122
(2012/03/10)
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- Surprising substituent effects on the self-assembly of helicates from bis(bipyridyl) BINOL ligands
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(Figure Presented) A number of different bis(bipyridyl) BINOL ligands were prepared using a convergent building block approach. These were studied with regard to their ability to undergo self-assembly to dinuclear helicates upon coordination to suitable late-transition-metal ions. Surprisingly, the substituents at the periphery of the ligand structure were found to have a marked influence on the outcome of the self-assembly processes with regard to the helicates composition, the stereoselectivity of the helicate formation, their redox reactivity, and their electronical properties as scrutinized by NMR- and CD-spectroscopic methods as well as ESI-mass spectrometric methods.
- Bunzen, Jens,Hovorka, Rainer,Luetzen, Arne
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supporting information; scheme or table
p. 5228 - 5236
(2009/12/04)
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- Synthesis and helicate formation of a new family of binol-based bis(bipyridine) ligands
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A new family of BINOL-based bis(bipyridine) ligands 1-3 (BINOL = 2,2 -dihydroxy-1,1 -binaphthyl) was prepared in enantiomerically pure form. Whereas the coordination of zinc(ll) ions to these ligands did not result in the selective formation of a specific metallosupramolecular aggregate,1 -3 were found to undergo highly diastereoselective self-assembly to D 2-symmetric dinuclear double-stranded helicates upon coordin ation to silver(l) and copper(l) ions and to D3-symmetric dinuclear triple-stranded helicates upon coordination to iron(ll) as demonstrated by mass spectrometry and by NMR and CD spectroscopy in combination with quantum chemical calculations.
- Bunzen, Jens,Bruhn, Torsten,Bringmann, Gerhard,Luetzen, Arne
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scheme or table
p. 3621 - 3630
(2009/08/14)
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- Preparation and properties of thienyl and 2,2'-substituted cobalt-bis(semiquinone) tautomers
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The synthesis and characterization of two new 2,2'-bipyridine ligands containing 3-ethynylthiophene and 3,3'-diethynyl-2,2'-bithiophene substituents is presented, along with the preparation, electronic, and magnetic properties of monoand bimetallic cobalt-semiquinone valence tautomers containing these ligands.
- O'Sullivan, Thomas J.,Djukic, Brandon,Dube, Paul A.,Lemaire, Martin T.
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scheme or table
p. 533 - 538
(2009/10/17)
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- Purines bearing phenanthroline or bipyridine ligands and their RuII complexes in position 8 as model compounds for electrochemical DNA labeling - Synthesis, crystal structure, electrochemistry, quantum chemical calculations, cytostatic and antiviral activity
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A series of ethynyl- or (4-boronophenyl)bipyridines and -phenanthrolines were prepared as versatile building blocks for attachment of bidentate N-ligands to other molecules via cross-coupling reactions. Their complexation with Ru(bpy)2-Cl2 gave the corresponding RuII complexes. 9-Benzyladenine derivatives bearing the bipyridine or phenanthroline complexes in position 8, attached via a conjugate acetylene or phenylene linker were prepared by cross-coupling reactions of the ethynyl- or 4-boronophenylbipyridines and -phenanthrolines with 9-benzyl-8-bromoadenine. Their complexation with Ru(bpy)2Cl2 afforded the corresponding Ru complexes as model compounds for electrochemical DNA labeling. The same compounds were also prepared directly by cross-coupling of 9-benzyl-8-bromoadenine with Ru complexes of the alkynes and boronic acids. Both approaches are compared in terms of potential applications for labeling of nucleic acids. The crystal structures of two Ru complexes were determined by X-ray diffraction. The electrochemistry of the model purines bearing the phenanthroline or bipyridine ligands and the Ru complexes was studied by means of cyclic or square-wave voltammetry with carbon paste and mercury electrodes. The experimental redox potentials of the title compounds were compared with quantum chemical calculations. A very good agreement between experiment and theory was obtained, with a standard deviation of 0.13 V. It was shown that theoretical calculations can be of a limited predictive power for new Ru II complexes, though it was difficult to reproduce differences smaller than 0.05 V. Several compounds of this series exhibited a considerable cytostatic effect and activity against the hepatitis C virus (HCV). Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Vrabel, Milan,Hocek, Michal,Havran, Ludek,Fojta, Miroslav,Votruba, Ivan,Klepetarova, Blanka,Pohl, Radek,Rulisek, Lubomir,Zendlova, Lucie,Hobza, Pavel,Shih, I.-Hung,Mabery, Eric,Mackman, Richard
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p. 1752 - 1769
(2008/02/06)
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- Synthesis and stereoselective self-assembly of double- and triple-stranded helicates
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Chiral cavities with inward-pointing functional groups are afforded by chiral bis(bipyridine) ligands. Upon coordination to suitable transition-metal ions, these self-assemble in a diastereoselective manner to form double- and triple-stranded helicates (left and right pictures, respectively).
- Luetzen, Arne,Hapke, Marko,Griep-Raming, Jens,Haase, Detlev,Saak, Wolfgang
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p. 2086 - 2089
(2007/10/03)
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- Functionalization of 2,2'-bipyridines in their 4 and 5 positions. Synthesis of 5-Ethynyl-2,2'-Bipyridine
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The synthesis of 5-ethynyl-2,2'-bipyridine (9) from 5methyl-2.2'- bipyridine (5) is reported. The conversion of the methyl derivative, which is the most common starting material to further substitution, involves the preparation of 2,2'-bipyridine-5-carbaldehyde (6). Corey-Fuchs olefination and subsequent hydrolysis yields the target compound 9. The multistep synthesis is discussed with respect to alternative routes and compared with those of related 4-substituted 2,2'-bipyridines.
- Polin, Johann,Schmohel, Erich,Balzani, Vincenzo
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p. 321 - 324
(2007/10/03)
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- Construction of Preorganized Polytopic Ligands via Palladium-Promoted Cross-Coupling Reactions
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Rigid preorganized multitopic ligands have been designed and synthesized. The Pd(0)-catalyzed cross-coupling reactions between ethynylated derivatives of bipyridine or terpyridine and the corresponding bipyridine or terpyridine halides or triflates provid
- Grosshenny, Vincent,Romero, Francisco M.,Ziessel, Raymond
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p. 1491 - 1500
(2007/10/03)
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