Synthesis and application of carbodithioate-terminated aryleneethynylenes.

摘要

The (trimethylsilyl)ethyl (TMSE) protecting group makes possible the straightforward synthesis of TMSE-protected carbodithioate-terminated oligo(phenyleneethynylene)s and meso-to-meso ethyne-bridged (porphinato)zinc(II) arrays via palladium-catalyzed cross coupling reactions; this protecting group also allows the facile elaboration of organocarbodithioate-functionalized metal complexes and gold nanoparticles (AuNPs) that, as model systems, will eventually provide a better understanding of the effect of molecular properties and interfacial electronic coupling values on charge transport across molecular junctions. X-ray crystallographic, spectroscopic, and theoretical studies on the bis[4-(arylethynyl)benzodithioato]metal complexes reveal a significant degree of metal--ligand electronic interactions that facilitate pi-conjugation along the long molecular axis and charger transfer between the metal and the ligands. More interestingly, 4-[(porphinato)zinc(II)ethyn-5'-yl]dithiobenzoate-functionalized AuNPs display unique absorption and emission signatures, and Raman mode enhancements, congruent with [(phenylethynyl)porphinato]zinc(II)--(gold surface) interfacial charge resonance; these features are absent in analogous 4-[(porphinato)zinc(II)ethyn-5'-yl]benzenethiol-functionalized AuNPs. These data are indicative of augmented metal---or metal surface---pi-conjugated chromophore electronic coupling, which is facilitated by the unsaturated carbodithioate linkers, and suggest that monocarbodithioate- and alpha,o-bis(carbodithioate)-terminated aryleneethynylene species are promising surface-functionalization reagents and potential molecular wires that could possibly replace classic thiol species.