- Strongly Luminescent Cyclometalated Gold(III) Complexes Supported by Bidentate Ligands Displaying Intermolecular Interactions and Tunable Emission Energy
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A series of charge-neutral AuIII complexes, which comprise a dicarbanionic C-deprotonated biphenyl ligand and bidentate ancillary ligands ([Au(C^C)(L^X)]; L^X=β-diketonate and relatives (O^O), quinolinolate and relatives (N^O), and diphosphino (P^P) ligands), were prepared. All the complexes are emissive in degassed CH2Cl2 solutions and in thin-film samples with Φem up to 18 and 35 %, respectively, except for 5 and 6, which bear (N^O)-type ancillary ligands. Variation of the electronic characteristics of the β-diketonate ancillary ligand was demonstrated to be a viable route for tuning the emission color from blue-green (peak λem at ca. 466 nm for 1 and 2; 501 nm for 4 a and 4 b) to orange (peak λem at 585 nm for 3), in contrast to the common observations that the ancillary ligand has a negligible effect on the excited-state energy of the AuIII complexes reported in the literature. DFT/time-dependent (TD) DFT calculations revealed that the energies of the 3ππ*(C^C) and the 3ILCT(O^O) excited states (ILCT=intraligand charge transfer) switch in order on going from O^O=acetylacetonate (acac) to aryl-substituted β-diketonate ligands. Solution-processed and vacuum-deposited organic light-emitting diode (OLED) devices of selected complexes were prepared. The vacuum-deposited OLED fabricated with 2 displays a sky-blue emission with a maximum external quantum efficiency (EQE) of 6.71 % and CIE coordinates of (0.22, 0.40). The crystal structures of 7 and 9 reveal short intermolecular AuIII???AuIII contacts, with intermetal distances of 3.408 and 3.453 ?, respectively. DFT/TDDFT calculations were performed on 7 and 9 to account for the noncovalent interactions. Solid samples of 1, 3, and 9 exhibit excimeric emission at room temperature, which is rarely reported in AuIII complexes.
- Chan, Kaai Tung,Tong, Glenna So Ming,Wan, Qingyun,Cheng, Gang,Yang, Chen,Che, Chi-Ming
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- Spectroscopic investigations of nano-sized titanium(IV) complexes containing electron-rich oxygen-based ligands
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A convenient method has been explored to synthesize some nano-sized, mixed-ligand complexes of titanium(IV) with the general formula [Ti(acac)Cl 2-n(L)n(OOCC15H31)] (where Hacac = acetylacetone, HL = dibenzoylme
- Singh, Alok Kumar,Baranwal, Balram Prasad
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- Bioinspired models for an unusual 3-histidine motif of diketone dioxygenase enzyme
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Bioinspired models for contrasting the electronic nature of neutral tris-histidine with the anionic 2-histidine-1-carboxylate facial motif and their subsequent impact on catalysis are reported. Herewith, iron(ii) complexes [Fe(L)(CH3CN)3](SO3CF3)21-3 of tris(2-pyridyl)-based ligands (L) have been synthesized and characterized as accurate structural models for the neutral 3-histidine triad of the enzyme diketone dioxygenase (DKDO). The molecular structure of one of the complexes exhibits octahedral coordination geometry and Fe-N11py bond lengths [1.952(4) to 1.959(4) ?] close to the Fe-NHis bond distances (1.98 ?) of the 3-His triad in the resting state of the enzyme, as obtained by EXAFS studies. The diketonate substrate-adduct complexes [Fe(L)(acacR)](SO3CF3) (R = Me, Ph) of 1-3 have been obtained using Na(acacR) in acetonitrile. The Fe2+/3+ redox potentials of the complexes (1.05 to 1.2 V vs. Fc/Fc+) and their substrate adducts (1.02 to 1.19 V vs. Fc/Fc+) appeared at almost the same redox barrier. All diketonate adducts exhibit two Fe(ii) → acac MLCT bands around 338 to 348 and 430 to 490 nm. Exposure of these adducts to O2 results in the decay of both MLCT bands with a rate of (kO2) 5.37 to 9.41 × 10-3 M-1 s-1. The kO2 values were concomitantly accelerated 20 to 50 fold by the addition of H+ (acetic acid), which nicely models the rate enhancement in the enzyme kinetics by the glutamate residue (Glu98). The oxygenation of the phenyl-substituted adducts yielded benzoin and benzoic acid (40% to 71%) as cleavage products in the presence of H+ ions. Isotope-labeling experiments using 18O2 showed 47% incorporation of 18O in benzoic acid, which reveals that the oxygen originates from dioxygen. Thus, the present model complexes exhibit very similar chemical surroundings to the active site of DKDO and mimic its functions elegantly. On the basis of these results, the C-C bond cleavage reaction mechanism is discussed.
- Ramasubramanian, Ramamoorthy,Anandababu, Karunanithi,M?sch-Zanetti, Nadia C.,Belaj, Ferdinand,Mayilmurugan, Ramasamy
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p. 14326 - 14336
(2019/10/11)
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- Liquid crystal polymorphism of boron difluoride β-diketonates
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Boron difluoride 2-alkyl-β-diketonates possessing liquid crystal polymorphism and luminescence properties were first obtained. Influence of the ligand structure on the liquid crystal properties of the boron difluoride complexes was demonstrated. Pleiades Publishing, Ltd., 2010.
- Turanova,Garifzyanova,Turanov
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experimental part
p. 2317 - 2322
(2011/04/14)
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- RUTHENIUM ANTICANCER COMPLEXES
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Ruthenium (II) compounds of formula (I) are useful in the treatment and/or prevention of cancer, wherein formula (I) is :
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Page/Page column 22
(2010/02/06)
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