Jacob Schneider

Strong intra- and intermolecular aurophilic interactions in a new series of brilliantly luminescent dinuclear cationic and neutral au(I) benzimidazolethiolate complexes.

The structural and photophysical properties of a new series of cationic and neutral Au(I) dinuclear compounds (1 and 2, respectively) bridged by bis(diphenylphosphino)methane (dppm) and substituted benzimidazolethiolate (X-BIT) ligands, where X = H (a), Me (b), OMe (c), and Cl (d), have been studied. Monocationic complexes, [A(u2)(micro-X-BIT)(micro-dppm)](CF(3)CO(2)), were prepared by the reaction of [A(u2)(micro-dppm)](CF(3)CO(2))(2) with 1 equiv of X-BIT in excellent yields. The cations 1a-1d possess similar molecular structures, each with a linear coordination geometry around the Au(I) nuclei, as well as relatively short intramolecular Au(I)...Au(I) separations ranging between 2.88907(6) A for 1d and 2.90607(16) A for 1a indicative of strong aurophilic interactions. The cations are violet luminescent in CH(2)Cl(2) solution with a lambda(em)(max) of ca. 365 nm, assigned as ligand-based or metal-centered (MC) transitions. Three of the cationic complexes, 1a, 1b, and 1d, exhibit unusual luminescence tribochromism in the solid-state, in which the photoemission is shifted significantly to higher energy upon gentle grinding of microcrystalline samples with DeltaE = 1130 cm(-1) for 1a, 670 cm(-1) (1b), and 870 cm(-1) (1d). The neutral dinuclear complexes, [A(u2)(micro-X-BIT)(micro-dppm)] (2a-2d) were formed in good yields by the treatment of a CH(2)Cl(2) solution of cationic compounds (1) with NEt(3). 2a-2d aggregate to form dimers having substantial intra- and intermolecular aurophilic interactions with unsupported Au(I)...Au(I) intermolecular distances in the range of 2.8793(4)-2.9822(8) A, compared with intramolecular bridge-supported separations of 2.8597(3)-2.9162(3) A. 2a-2d exhibit brilliant luminescence in the solid-state and in DMSO solution with red-shifted lambda(em)(max) energies in the range of 485-545 nm that are dependent on X-BIT and assigned as ligand-to-metal-metal charge transfer (LMMCT) states based in part on the extended Au...Au...Au...Au interactions.

Synthesis, characterization, and photophysical properties of platinum(II) terpyridyl-based multi-component systems

Four new Pt(II) terpyridyl acetylide complexes are reported which possess either a viologen or nicotinamide unit attached as an electron acceptor via the benzylic carbon of the tolyl-terpyridine ligand. Specifically, the donor–chromophore–acceptor (D–C–A) triads prepared are [Pt(ttpy-MV)C≡C–C6H4–NH–CO–C6H2(OMe)3](PF6)3 [1], where ttpy-MV = 4′-([4-methyl-4,4′-bipyridin]-ylmethyl-phenyl)-[2,2′;6′,2″]terpyridine and C≡C–C6H4–NH–CO–C6H2(OMe)3 = N-(4-ethynylphenyl)-3,4,5-trimethoxybenzamide and [Pt(ttpy-Nd)C≡C–C6H4–NH–CO–C6H2(OMe)3](PF6)2 [2], where ttpy-Nd = 4′-([3-carboxamide-pyridin]-ylmethyl-phenyl)-[2,2′;6′,2″]terpyridine. The related chromophore–acceptor (C–A) dyads, [Pt(ttpy-MV)C≡CPh](PF6)3 [3], where C≡CPh = phenylacetylide and [Pt(ttpy-Nd)C≡CPh](PF6)2 [4], were also prepared. The syntheses of the above compounds are achieved by the reaction of a prepared cuprous phenylacetylide compound with the appropriate platinum terpyridyl chloride complex. This change from the CuI-catalyzed acetylide coordination, which requires basic conditions, results from the observed sensitivity of the pyridinium type acceptors to base. While the parent chromophore, [Pt(ttpy)C≡CPh]PF6 [5], where ttpy = 4′-p-tolyl-[2,2′;6′,2″]terpyridine, is brightly emissive in fluid solution, both of the aforementioned D–C–A triads 1 and 2 are nonemissive at room temperature. Of the related C–A dyads, 4 is emissive and 3 is very weakly emissive. Transient absorption studies reveal that the nicotinamide acceptor does not function as an oxidative quencher of the excited state. In contrast, the viologen acceptor appears to function as an oxidative quencher.