Adduct effects on structure and luminescence in a series of new dithiocarbamatogold(I) complexes

Reaction of [AuCl(SMe₂)] with NaL•H₂O (L = ethyl(pyridine-4-yl methyl)dithiocarbamate (epdtc) or methyl(2-(pyridin-2-yl) ethyl)dithiocarbamate (mpdtc)) affords a series of neutral dinuclear gold(I) complexes bridged by each dithiocarbamate ligand, [Au(L)]₂. The successive reaction of [Au(L)]₂ with organic acids such as isophthalic acid (m-pa) and maleic acid (ma) produces 1:1 adducts, [Au(L)] ₂•(organic acid). The crystal structure of [Au(L)] ₂•(m-pa) is a 1D polymer formed via hydrogen bonds between the free pyridyl and the carboxylic acid moiety. For the dinuclear moiety, strong intradinuclear aurophilic interactions (Au(I)-Au(I) = 2.7783(8) Å and 2.7525(7) Å) exist, but interdinuclear interactions are weak (3.2551(8)-3.2733(8) Å). The dinuclear gold(I) complexes, [Au(epdtc)] ₂ and [Au(mpdtc)]₂, show a bright luminescence at 562.5 and 552.0 nm in solid state, respectively, but their organic acid adducts, [Au(L)]₂•(organic acid), have no luminescent properties. This dramatic difference in properties between the gold(I) complexes and their adducts may be ascribed to the weakness of the internuclear Au(I)-Au(I) interaction including crystal packing.