Luminescent complexes of silver(i) with pyridylbis(3-hexamethyleneiminyl thiosemicarbazone): effect of the counterion on the nuclearity

Abstract

The reaction of pyridylbis(3-hexamethyleneiminyl thiosemicarbazone) (H₂Plhexim) with various silver(I) salts and metal–ligand ratios led to the isolation of different complexes of the formulae [Ag(NO₃)(H₂Plhexim)]·H₂O (1), [Ag₂(NO₃)(H₂Plhexim)(CH₃OH)](NO₃) (2), [Ag₂(ClO₄)₂(H₂Plhexim)] (3), [Ag(HPlhexim)]·xH₂O (4), [Ag(HPlhexim)] (4a), [Ag₂(Plhexim)(PPh₃)₄]·2MeOH (5) and [Ag₄(Plhexim)₂]·DMF (6). The complexes were fully characterized by elemental analysis, ESI mass spectrometry, IR and NMR (¹H, ³¹P) spectroscopy. The structures of 4a, 5 and 6 were also identified by single crystal X-ray structure determination. The concentration dependence on the absorption spectra of the methanolic solutions indicates polymerization equilibria in the ground state in both the ligand and the complexes. While H₂Plhexim is essentially non-fluorescent, complexes 1–5 fluoresce more strongly by comparison. This fluorescent behavior is consistent with the monomeric or dimeric nature of the complexes.