Dataset Information

Electronic communication across diamagnetic metal bridges: a homoleptic gallium(III) complex of a redox-active diarylamido-based ligand and its oxidized derivatives.

ABSTRACT: Complexes with cations of the type [Ga(L)(2)](n+) where L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido and n = 1, 2, 3 have been prepared and structurally characterized. The electronic properties of each were probed by electrochemical and spectroscopic means and were interpreted with the aid of density functional theory (DFT) calculations. The dication, best described as [Ga(L(-))(L(0))](2+), is a Robin-Day class II mixed-valence species. As such, a broad, weak, solvent-dependent intervalence charge transfer (IVCT) band was found in the NIR spectrum in the range 6390-6925 cm(-1), depending on the solvent. Band shape analyses and the use of Hush and Marcus relations revealed a modest electronic coupling, H(ab) of about 200 cm(-1), and a large rate constant for electron transfer, k(et), on the order of 10(10) s(-1) between redox active ligands. The dioxidized complex [Ga(L(0))(2)](3+) shows a half-field ?M(s) = 2 transition in its solid-state X-band electron paramagnetic resonance (EPR) spectrum at 5 K, which indicates that the triplet state is thermally populated. DFT calculations (M06/Def2-SV(P)) suggest that the singlet state is 21.7 cm(-1) lower in energy than the triplet state.

SUBMITTER: Liddle BJ

PROVIDER: S-EPMC3601749 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Electronic communication across diamagnetic metal bridges: a homoleptic gallium(III) complex of a redox-active diarylamido-based ligand and its oxidized derivatives.

Liddle Brendan J BJ Wanniarachchi Sarath S Hewage Jeewantha S JS Lindeman Sergey V SV Bennett Brian B Gardinier James R JR

Inorganic chemistry 20121119 23

Complexes with cations of the type [Ga(L)(2)](n+) where L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido and n = 1, 2, 3 have been prepared and structurally characterized. The electronic properties of each were probed by electrochemical and spectroscopic means and were interpreted with the aid of density functional theory (DFT) calculations. The dication, best described as [Ga(L(-))(L(0))](2+), is a Robin-Day class II mixed-valence species. As such, a broad, weak, solvent-dependent intervalence ...[more]

PMID: 23163736

Similar Datasets

Project description:Different synthetic methods have been developed to prepare eight new redox-active pincer-type ligands, H(X,Y), that have pyrazol-1-yl flanking donors attached to an ortho-position of each ring of a diarylamine anchor and that have different groups, X and Y, at the para-aryl positions. Together with four previously known H(X,Y) ligands, a series of 12 Ni(X,Y)2 complexes were prepared in high yields by a simple one-pot reaction. Six of the 12 derivatives were characterized by single-crystal X-ray diffraction, which showed tetragonally distorted hexacoordinate nickel(II) centers. The nickel(II) complexes exhibit two quasi-reversible one-electron oxidation waves in their cyclic voltammograms, with half-wave potentials that varied over a remarkable 700 mV range with the average of the Hammett ?(p) parameters of the para-aryl X, Y groups. The one- and two-electron oxidized derivatives [Ni(Me,Me)2](BF4)n (n = 1, 2) were prepared synthetically, were characterized by X-band EPR, electronic spectroscopy, and single-crystal X-ray diffraction (for n = 2), and were studied computationally by DFT methods. The dioxidized complex, [Ni(Me,Me)2](BF4)2, is an S = 2 species, with nickel(II) bound to two ligand radicals. The mono-oxidized complex [Ni(Me,Me)2](BF4), prepared by comproportionation, is best described as nickel(II) with one ligand centered radical. Neither the mono- nor the dioxidized derivative shows any substantial electronic coupling between the metal and their bound ligand radicals because of the orthogonal nature of their magnetic orbitals. On the other hand, weak electronic communication occurs between ligands in the mono-oxidized complex as evident from the intervalence charge transfer (IVCT) transition found in the near-IR absorption spectrum. Band shape analysis of the IVCT transition allowed comparisons of the strength of the electronic interaction with that in the related, previously known, Robin-Day class II mixed valence complex, [Ga(Me,Me)2](2+).

Project description:Meso tetraarylporphyrinato gold(iii) cations bearing different substituents at the aryl substituents (COOMe, COOH, NO2, NH2, NHAc, H, O n Bu, CF3) were prepared and characterised. Their reversible one-electron reductions were studied by (spectro)electrochemical means as well as by selective chemical one-electron reduction using cobaltocene. The preferred location of the spin density, namely gold centred or porphyrin centred, was probed by electron paramagnetic resonance spectroscopy (g values, 197Au hyperfine coupling) as well as by density functional theory calculations (spin densities). In all cases studied experimentally and theoretically, the gold(ii) valence isomer (5d9 electron configuration) is preferred over the porphyrin π radical anion. In the hexafluorophosphate salt of the nitro derivative a further nitro π radical anion valence isomeric species is significantly populated. In the presence of chloride ions this nitro π radical anion/AuII valence isomeric equilibrium evolves towards the porphyrin π radical anion. The electronic structures of the nitro π radical and the AuII σ radical valence isomers (5d x2-y2 orbital) could be calculated by DFT methods. The electron transfer pathway between the nitro π radical anion and the AuII valence isomer is well described by the location of the hexfluorophosphate counterion, the Au-N distances (corresponding to the totally symmetric stretching vibration), the symmetric stretching mode of the NO2 substituent and a meso-nitrophenyl rotation. The specific geometric and electronic properties of the favoured gold(ii) σ radical valence isomer, namely counterion dislocation and σ symmetry of the redox orbital, might stabilise charge-shifted states [(gold(ii) porphyrin)-donor˙+] by retarding the back electron transfer to give the ground state (gold(iii) porphyrin)-donor. This will guide the design of (photo-induced) electron transfer pathways with tetraarylporphyrinato gold(iii) complexes as electron acceptors.

Dataset Information

Electronic communication across diamagnetic metal bridges: a homoleptic gallium(III) complex of a redox-active diarylamido-based ligand and its oxidized derivatives.

Publications

Electronic communication across diamagnetic metal bridges: a homoleptic gallium(III) complex of a redox-active diarylamido-based ligand and its oxidized derivatives.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets