- Tetradentate N^N°N^N-type luminophores for Pt(II) complexes: Synthesis, photophysical and quantum-chemical investigation
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Herein we report on dianionic tetradentate, pyridin-azole-based ligands for luminescent Pt(II) complexes. To improve their solubility in common organic solvents, a hexyl-chain was inserted in the periphery of the luminophoric ligand and different substituents were introduced at the 1H-pyrazole moieties including 4-hexylphenyl- (L1), adamantyl- (L2) and 3,5-dimethoxyphenyl (L3) substituents. For the new ligand precursors L1 and L2, the corresponding Pt(II) complexes Pt1 and Pt2 were synthesized and characterized by exact mass spectrometry as well as by 1H NMR. L3 was also successfully synthesized and isolated, but due to the limited solubility of the resulting coordination compound, the purification and structural characterization of the corresponding Pt(II) complex Pt3 was not achieved. The absorption and steady-state as well as time-resolved photoluminescence spectra of Pt1 and Pt2 were investigated and interpreted employing TD–DFT. We found that the S1 states for Pt1 and Pt2 can be described mainly as single electron HOMO→LUMO excitations with a 1MP-ILCT character comprising the diazole units and the pyridine rings. At room temperature, Pt1 and Pt2 show phosphorescence in the green region of the electromagnetic spectrum peaking at 506 nm and 497 nm with photoluminescence quantum yields reaching 17% and 25%, respectively. DFT calculations show that the T1 states of Pt1 and Pt2 can be mainly described as monoelectronic HOMO→LUMO excitations with predominant 3MP-ILCT character.
- Cnudde, Marvin,Brünink, Dana,Doltsinis, Nikos L.,Strassert, Cristian A.
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- Iridium(III) Complexes Bearing a Formal Tetradentate Coordination Chelate: Structural Properties and Phosphorescence Fine-Tuned by Ancillaries
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Synthesis of the multidentate coordinated chelate N3C-H2, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation of Ir(III) metal complexes bearing a N3C chelate in the tridentate (κ3), tetradentate (κ4), and pentadentate (κ5) modes was executed en route from two nonemissive dimer intermediates [Ir(κ3-N3CH)Cl2]2 (1) and [Ir(κ4-N3C)Cl]2 (2). Next, a series of mononuclear Ir(III) complexes with the formulas [Ir(κ4-N3C)Cl(py)] (3), [Ir(κ4-N3C)Cl(dmap)] (4), [Ir(κ4-N3C)Cl(mpzH)] (5), and [Ir(κ4-N3C)Cl(dmpzH)] (6), as well as diiridium complexes [Ir2(κ5-N3C)(mpz)2(CO)(H)2] (7) and [Ir2(κ5-N3C)(dmpz)2(CO)(H)2] (8), were obtained upon treatment of dimer 2 with pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3, 5, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations. Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the development of highly efficient iridium complexes for OLED applications.
- Yuan, Yi,Gnanasekaran, Premkumar,Chen, Yu-Wen,Lee, Gene-Hsiang,Ni, Shao-Fei,Lee, Chun-Sing,Chi, Yun
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p. 523 - 532
(2019/12/30)
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- Bis(pyrazolato) Bridged Diiron Complexes: Ferromagnetic Coupling in a Mixed-Valent HS-FeII/LS-FeIII Dinuclear Complex
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Using a new bis(tridentate) compartmental pyrazolate-centered ligand HL, the bis(pyrazolato)-bridged diiron complex [L2FeII2][OTf]2 (1) and its singly oxidized mixed-valent congener [L2FeIIFeIII][OTf]3 (2) have been synthesized and structurally characterized. While 1 features two HS-FeII ions coordinated to two cis-axial pyridine moieties in a highly distorted octahedral environment, the metal ions in 2 are coordinated by the ligand strand in a trans-axial configuration. Very different Fe–N bond lengths and distinctly different coordination polyhedra are associated with pronounced valence localization in the case of 2. The electronic structures and magnetic properties of 1 and 2 have been further investigated by M?ssbauer spectroscopy and variable temperature magnetic susceptibility measurements. In the case of 1, weak antiferromagnetic coupling is observed between the two HS-FeII ions (J = –0.6 cm–1), while the HS-FeII and LS-FeIII ions in 2 are ferromagnetically coupled (J = +5.2 cm–1) to give an ST = 5/2 ground state with significant zero-field splitting (DFe(II) = 2.3 cm–1). The findings are rationalized with the help of DFT computations.
- Dechert, Sebastian,Demeshko, Serhiy,Hua, Shao-An,Meyer, Franc,Wong, Joanne W. L.,Ye, Shengfa
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p. 4137 - 4145
(2020/11/23)
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- Chemo- and Stereoselective Synthesis of Fluorinated Amino Alcohols through One-pot Reactions using Alcohol Dehydrogenases and Amine Transaminases
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A series of amino alcohols have been prepared in a chemo-, diastereo- and enantioselective fashion starting from the corresponding (het)aryl diketones, avoiding tedious chemical protection and deprotection steps. Different alcohol dehydrogenases have been
- González-Martínez, Daniel,Gotor, Vicente,Gotor-Fernández, Vicente
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supporting information
p. 5398 - 5410
(2020/10/06)
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- Mono- And Dinuclear Coinage Metal Complexes Supported by an Imino-Pyridine-NHC Ligand: Structural and Photophysical Studies
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A new imino-pyridine-NHC (NHC = N-heterocyclic carbene) hybrid ligand was accessed through a multistep synthesis, and its coordination chemistry was examined among coinage metals. Mononuclear copper, silver, and gold complexes as well as dinuclear homo- and heterometallic complexes were isolated and fully characterized by spectroscopic methods as well as X-ray crystallography. A comparative study of the structural and photophysical properties of the complexes was performed to get more insight into structure-property relationships. The photoluminescence (PL) properties were investigated in the solid state at temperatures between 20 and 295 K, and systematically compared with those of related complexes bearing a bipyridine-NHC ligand and previously reported by our group. The PL properties can be finely "tuned" depending on the coordinated metals, and the weak emission of the complexes can be traced back to the structural flexibility of the imino-pyridine-NHC framework.
- Simler, Thomas,M?bius, Karen,Müller, Kerstin,Feuerstein, Thomas J.,Gamer, Michael T.,Lebedkin, Sergei,Kappes, Manfred M.,Roesky, Peter W.
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p. 3649 - 3661
(2019/11/13)
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- Vinylation of Aldehydes Using Mn/Cr Alloy and a N4-Ligand/NiII-Catalyst
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We report an efficient and practical protocol for the Cr/Ni-catalyzed vinylation of aldehydes, based on the use of Mn/Cr alloy (ca. 10% Cr) and TMSCl. No additional Cr salts need to be added. In the presence of NiCl2 (0.3 mol%) and a bis(ketimino)-2,2′-bipyridine as N4-chelating ligand (1 mol%), the vinylations proceed smoothly at room temperature. The presence of catalytic amounts of MeOH and LiOAc as additives was found to further promote the efficiency of the catalytic system, even in the absence of the ligand. Detailed reaction monitoring revealed that LiOAc accelerates the product alcohol silylation, thus increasing the turnover rate.
- Harnying, Wacharee,Berkessel, Albrecht
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supporting information
p. 6057 - 6061
(2015/04/14)
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- Linkage isomerism in transition-metal complexes of mixed (arylcarboxamido)(arylimino)pyridine ligands
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The synthesis of a series of asymmetric mixed 2,6-disubstituted (arylcarboxamido)(arylimino)pyridine ligands and their coordination chemistry toward a series of divalent first-row transition metals (Cu, Co, and Zn) have been explored. Complexes featuring both anionic N,N,N″-carboxamido and neutral O,N,N-carboxamide coordination have been prepared and characterized by X-ray crystallography, cyclic voltammetry, and UV-visible and EPR spectroscopy. Specifically, RLM(X) (M = Cu; X = Cl-, OAc-) and RL(H)MX2 (M = Cu, Co, Zn; X = Cl-, SbF 6-) complexes that feature N,N,N″- or O,N,N-coordination are presented. Base-induced linkage isomerization from O,N,N-carboxamide to N,N,N″-carboxamido coordination is also confirmed by multiple forms of spectroscopy.
- Boyce, David W.,Salmon, Debra J.,Tolman, William B.
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p. 5788 - 5796
(2014/06/23)
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- A family of immobilizable chiral bis(pinenebipyridine) ligands
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New enantiopure ligands containing two (-)-5,6-pinenebipyridine units connected by a bridge situated in position 6′ of the bipyridines have been prepared. The chemically addressable groups of the bridging (hydroxyl or keto) can be covalently bound to various supports in order to heterogenize the ligand. Georg Thieme Verlag Stuttgart · New York.
- P?llnitz, Alpár,Skupienski, Radek,Stoeckli-Evans, Helen,Crochet, Aurélien,Silvestru, Anca,Fromm, Katharina M.,Mamula, Olimpia
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p. 2555 - 2558
(2013/12/04)
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- AMINOTRIAZOLE DERIVATIVES AS ALX AGONISTS
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The invention relates to aminotriazole derivatives of formula (I), wherein A, E, R1 and R2 are as defined in the description, their preparation and their use as pharmaceutically active compounds. The compounds are useful for the prevention or treatment of diseases, which respond to the modulation of the ALX receptor such as inflammatory diseases.
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Page/Page column 76
(2009/07/18)
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- Polynuclear lanthanide complexes of a series of bridging ligands containing two tridentate N,N′,O-donor units: Structures and luminescence properties
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A set of three potentially bridging ligands containing two tridentate chelating N,N′,O-donor (pyrazole-pyridine-amide) donors separated by an o, m, or p-phenylene spacer has been prepared and their coordination chemistry with lanthanide(iii) ions investig
- Ronson, Tanya K.,Adams, Harry,Harding, Lindsay P.,Pope, Simon J. A.,Sykes, Daniel,Faulkner, Stephen,Ward, Michael D.
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p. 1006 - 1022
(2007/10/03)
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- Synthetic approaches to polypyridyl bridging ligands with proximal multidentate binding sites
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A series of 12 bridging ligands was prepared. These ligands include a central linker appended to two 1,8-naphthyrid-2-yl or two 1,10-phenanthrolin-2- yl units. The linkers include pyridazin-3,6-diyl, 1,8-naphthyrid-2,7-diyl, 2,2′-bipyrid-6,6′-diyl, 1,10-phenanthrolin-2,9-diyl, 1,2-di(2′-pyrid-6′-yl)ethyne, and 3,6-di(2′-pyrid-6′-yl) pyridazine. The ligands were synthesized from the diacetyl derivative of the central linker by a Friedlaender condensation with either 2-aminonicotinaldehyde or 8-amino-7-quinolinecarbaldehyde. The precursor diacetyl derivatives were, in turn, prepared by pathways involving Stille and Sonogashira couplings. Examination of the electronic absorption spectra of the bridging ligands shows the strongest correlation to be between pairs of ligands having the same central linker. Complexation studies will follow.
- Zong, Ruifa,Wang, Dong,Hammitt, Richard,Thummel, Randolph P.
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p. 167 - 175
(2007/10/03)
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- Use of Stille-type cross-coupling as a route to oligopyridylimines
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The new tin reagents, 2-(n-Bu3Sn)-6-{C(R)OCH2CH 2O}-C5H3N, (R=H a, Me b), have been employed in Stille-type cross-coupling reactions with a range of oligopyridylbromides generating, following a facile deprotection step, a series of formyl- and acetyl-functionalised oligopyridines. Condensation reactions with 2,6-diisopropylaniline has allowed access to families of novel sterically bulky multidentate N,N,N,N (tetradentate), N,N,N,N,N (pentadentate), N,N,N,N,N,N (sexidentate) and N,N,N,N,N,N,N (heptadentate) nitrogen donor ligands. This work represents a straightforward and rapid synthetic route for the preparation of oligopyridylimines, which are expected to act as useful components for the self-assembly of polymetallic complexes.
- Champouret, Yohan D.M.,Chaggar, Rajinder K.,Dadhiwala, Ishaq,Fawcett, John,Solan, Gregory A.
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- Preparation and antioxidant activity of α-pyridoin and its derivatives
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Focusing on α-pyridoin (1, 1,2-di(2-pyridyl)-1,2-ethenediol) as the lead compound of the novel antioxidative enediol, we synthesized 5,5′- or 6,6′-bis-substituted derivatives of 1 from disubstituted pyridines. The antioxidant activity of 1 and its synthetic derivatives 2-7 was evaluated by DPPH (1,1-diphenyl-2-picrylhydrazyl radical) scavenging assay and inhibition of lipid peroxidation. In the DPPH assay, 1 exhibited an activity stronger than that of ascorbic acid, and 5,5′-dimethyl-(5) or 5,5′-dimethoxy- substituted derivatives (6) exhibited more potent activity than 1. The DPPH scavenging activities of α-pyridoins were correlated with their oxidation potential and thus the electron density of enediol. 5 and 6 effectively inhibited lipid peroxidation in the rat liver microsome/tert-butyl hydroperoxide system. Therefore, 5 and 6 serve as good candidates for a pharmacologically useful enediol antioxidant.
- Hatanaka, Masashi,Takahashi, Kyoko,Nakamura, Shigeo,Mashino, Tadahiko
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p. 6763 - 6770
(2007/10/03)
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- Steric control of directional isomerism in dicopper(I) helicates of asymmetrically substituted 2,2':6',2':2,6'-quaterpyridine derivatives
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Derivatives of 2,2':6',2'':2'',6'''-quaterpyridine have been prepared which are asymmetrically substituted with alkyl groups in the 4- or 6- position and with various substituents in the 4'-position. These ligands form dicopper(I) double helicates which have been investigated by 1H and 13C NMR spectroscopic techniques. The formation of helical isomers is shown to depend on the intramolecular interactions between the constituent helicands of the double helicate; 4'-methyl substituents undergo steric interactions with the 4-substituent of the partner helicand, leading to a modest selectivity, although bulky 4-substituents decrease selectivity. In the absence of 4'-substituents, the smaller pitch permits steric interactions between like 4-substituents of the component helicands. In each case, formation of the head-to-head helicate isomer is preferred.
- Constable,Heirtzler,Neuburger,Zehnder
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p. 5606 - 5617
(2007/10/03)
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