Synthesis and spectroscopic studies of Cu(I), Ag(I) and Au(I)-N-heterocyclic complexes

Abstract

Reaction of 2-Aminopyridine (L) and [Au(SMe2)Cl] in acetonitrile leads to the formation of three different Au(I) complexes: [AuL2]+, [LAuCl] and [AuCl2]-. The three Au(I) complexes co-crystallized to form trinuclear Au(I) unit, {[AuL2]+[LAuCl][AuCl2]-}, in the ratio 1:1:1. X-ray crystal analysis of the compound {[AuL2]+[LauCl][AuCl2]-} showed that the cation [AuL2]+, the neutral complex [LAuCl] and the anion [AuCl2]- are arranged in an unprecedentd pattern [+ neutral -]. Furthermore, the Au(I) complexes assemble to form two-dimensional networks in solid state, via cooperative action of so called "aurophilic" interactions and Na??Ha??a??a??Cl hydrogen bonding interactions. Reaction of 2,4,6-Tris-2-pyridyl-1,3,5-triazine (TPTZ) with stoichiometric quantities of [Cu(MeCN)2(PPh3)2]PF6 results in the complex of [Cu(PPh3)2(TPTZ)]PF6. Similarly, {[Cu(PPh3)2]2(TPTZ)}(PF6)2, {[Ag(PPh3)]2(TPTZ)}(PF6)2, and [Ag(PPh3)2(TPTZ)]PF6 have been synthesized and the crystal structures have been solved respectively. Detailed NMR investigation indicated fluxional properties of these compounds. Additionally, spectroscopic properties of these complexes have also been investigated. From the UV-visible spectrum, Cu(I) complexes of TPTZ exhibit a broad band around 450 nm which is assigned as the MLCT (Metal to Ligand Charge-Transfer) transition whereas the same absorption in Ag(I) complexes of TPTZ occurs at higher energy. The complexes show MLCT emission at 77 K.