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The focus of recent research on square planar Pt(II) diimine dithiolate complexes has been to understand molecular factors that influence their excited state properties and to develop diad and triad systems based on them for use in light-driven reactions. Regarding the former, two series of Pt(diimine)(dithiolate) complexes have been synthesized and studied. All of the compounds display solvatochromic absorption bands and solution luminescence attributable to metal/dithiolate-to-diimine charge transfer excited states of the same orbital parentage. The excited-state energies can be tuned by approximately 1 eV through ligand variation. Excited-state redox potentials have been estimated for all of the complexes from spectroscopic and electrochemical data, and electron transfer quenching rate constants show the expected driving force dependence. Analogous Au(III) systems have been synthesized and characterized including molecular structure determinations of a cationic diimine dithiolate system and a neutral C-deprotonated-2-phenylpyridine derivative. Striking differences exist in the electronic structures of these Au(III) complexes from those of the Pt(II) systems, underscoring the key role of the metal in the excited state structure of the latter. The creation of diads and triads is being undertaken with ligand bridges capable of connecting the Pt(diimine)(dithiolate) moiety with other metal centers. Toward that end, complexes of dipyridocatecholate (dpcat) have been synthesized and characterized. These complexes may serve as models for the linking of chromophore and quencher components of a possible photosynthetic system. The dpcat complexes have been characterized by absorption and steady-state emission spectroscopies. Luminescence and redox properties of these and a related system containing a tetrapyridophenazine (tppz) bridge are described.

The heterobimetallic sulfido cluster CpEt2Mo2Co2S4(CO)2 was oxidized to give a series of 58-VSE (valence shell electron) electron-deficient clusters of the type CpEt2Mo2Co2S4(X)2 (X = I, Br, Cl, SP...

A series of new bimetallic sulfido clusters, Cp#2M2M‘2S4(NO)2 (Cp# = C5Me2Et, C5Me5, C5H5; M = Mo, W; M‘ = Fe, Co) have been synthesized and characterized by X-ray diffraction. Two new tungsten carbonyl clusters, Cp*2W2Co2S4(CO)2 and CpEt2W2Co2S3(CO)5, were also synthesized and the structure of the latter determined. The structural systematics are related to the redox properties and to the electronic structure of the clusters.

Two Au(III) dithiolate complexes, [Au(dbbpy)(tdt)]PF(6) and Au(eta(2)-C,N-ppy)(tdt), (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine; tdt = 3,4-toluenedithiolate; ppy = C-deprotonated 2-phenylpyridine), have been prepared and structurally characterized by X-ray crystallography. The complexes have low-energy absorption bands that exhibit mild solvatochromism (lambda(max) = 444 nm (epsilon, 2310 M(-)(1) cm(-)(1)) in CH(2)Cl(2) and 406 nm (epsilon, 3170 M(-)(1) cm(-)(1)) in DMSO) and are tentatively assigned to a charge-transfer-to-diimine transition. This transition occurs at higher energy than the analogous charge-transfer transition in related Pt(II) complexes (e.g., Pt(dbbpy)(tdt), lambda(max) = 563 nm (epsilon, 7200 M(-)(1) cm(-)(1)). Whereas neither Au(III) complex is emissive, their respective dichloride precursors, [Au(dbbpy)Cl(2)]PF(6) and Au(eta(2)-C,N-ppy)Cl(2), luminesce in low-temperature glass matrixes from an excited state that is tentatively assigned as intraligand pi-pi. The neutral complex, Au(eta(2)-C,N-ppy)(tdt), is more easily oxidized (E(ox) = 0.925 V vs 1.589 V (vs NHE)) and less easily reduced (E(red) = -1.339 V vs -0.255 V (vs NHE)) than the cationic complex, [Au(dbbpy)(tdt)]PF(6). Both dithiolate complexes exhibit approximately square planar coordination. Yellow crystals of [Au(dbbpy)(tdt)]PF(6) (C(25)H(30)AuF(6)N(2)PS(2)) are triclinic, space group Ponemacr; (No. 2), with a = 7.1977(2) Å, b = 11.7292(1) Å, c = 17.5820(5) Å, alpha = 104.537(2) degrees, beta = 96.592(2) degrees, gamma = 102.455(2) degrees, V = 1380.41(6) Å(3), Z = 2, and final R = 0.050 (R(w) = 0.1062) for 3446 unique reflections. Orange crystals of Au(eta(2)-C,N-ppy)(tdt) (C(18)H(14)AuNS(2)) are monoclinic, space group P2(1)/c (No. 14), with a = 8.852(1) Å, b = 11.726(2) Å, c = 15.499(5) Å, beta = 101.34(2) degrees, V = 1577.5(6) Å(3), Z = 4, and final R = 0.0438 (R(w) = 0.0759) for 3685 unique reflections. A structural trans effect in Au(eta(2)-C,N-ppy)(tdt) results in a significantly longer Au-S distance (ca. 0.1 Å) trans to the Au-C bond than that trans to the Au-N bond. In the solid state, the [Au(dbbpy)(tdt)](+) cations are arranged in stacks with alternating intermolecular Au.Au separations of 3.60 and 3.75 Å while the Au(eta(2)-C,N-ppy)(tdt) molecules form stacks with an intermolecular Au.Au separation of 3.81 Å.