Structural variations and spectroscopic properties of luminescent mono- and multinuclear silver(I) and copper(I) complexes bearing phosphine and cyanide ligands

Reaction of equimolar amounts of AgCN and PCy3 gave the polymer (Cy3P)Ag(NCAgCN)]infinity (1), whereas employment of excess PCy3 yielded the discrete compound (Cy3P)2Ag(NCAgCN)] (2). Reacting bis(dicyclohexylphosphino)methane (dcpm) with AgCN in 1:1 and 1:2 molar ratios gave two crystalline forms, namely Ag2(mu-dcpm)2]Ag(CN)2]2 x (CH3OH)2 (3a x (CH3OH)2) and Ag2(mu-dcpm)2]Ag(CN)2]2 (3b), respectively. The similar reaction of CuCN with PCy3 afforded the polymeric compound {(Cy3P)Cu(CN)}3]infinity (4), whereas treatment of CuCN with dcpm gave Cu2(mu-dcpm)2(CN)2] (5). Employment of diphosphine ligands with longer -(CH2)n- spacers, such as 1,2-bis(dicyclohexylphosphino)ethane (dcpe, n = 2) and 1,3-bis(diphenylphosphino)propane (dppp, n = 3), in reactions with Cu(CH3CN)4]PF6 and KCN afforded the macrocylic compounds {Cu(dcpe)}2(CN)(mu-dcpe)]PF6 (6(PF6)) and {Cu(dppp)}3(CN)2(mu-dppp)]PF6 (7(PF6)), respectively. The hexanuclear complex Cu(CN)(PCy3)]6 (8) was obtained by reacting CuCN with PCy3 in the presence of sodium pyridine-2-thiolate. The UV-vis absorption spectrum of 1 in acetonitrile displays a weak shoulder at 245 nm (epsilon = 350 dm3 mol(-1) cm(-1)). For 3a, 3b, and 5, the intense absorption bands at lambdamax = 257-276 nm with epsilon values of (1.73-1.80) x 10(4) dm3 mol(-1) cm(-1) are assigned to ndsigma --> (n + 1)psigma] transitions. Complexes 3a and 3b emit at lambdamax = 365 nm in CH3CN (quantum yield approximately 6 x10(-3), lifetime approximately 0.2 micros). The solid-state emission of 5 (lambdamax = 470 and 488 nm at 298 and 77 K) is red-shifted in energy from that of 4 (lambdamax = 401 and 405 nm at 298 and 77 K, respectively). In 77 K MeOH/EtOH (1:4) glassy solution, complexes 4-8 display intense emission with lambdamax at 382-416 nm, which is assigned to the 3d --> (4s, 4p)] triplet excited state.