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

Abstract

Reaction of equimolar amounts of AgCN and PCy 3 gave the polymer [(Cy 3P)Ag(NCAgCN)]∞ (1), whereas employment of excess PCy 3 yielded the discrete compound [(Cy 3P) 2Ag(NCAgCN)] (2). Reacting bis(dicyclohexylphosphino)-methane (dcpm) with AgCN in 1:1 and 1:2 molar ratios gave two crystalline forms, namely [Ag 2(μ-dcpm) 2][Ag-(CN) 2] 2· (CH 3OH) 2 (3a·(CH 3OH) 2) and [Ag 2(μ-dcpm) 2][Ag(CN) 2] 2 (3b), respectively. The similar reaction of CuCN with PCy 3 afforded the polymeric compound [{(Cy 3P)Cu(CN)} 3]∞ (4), whereas treatment of CuCN with dcpm gave [Cu 2(μ-dcpm) 2(CN) 2] (5). Employment of diphosphine ligands with longer -(CH 2) 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(CH 3CN) 4]PF 6 and KCN afforded the macrocylic compounds [{Cu(dcpe)} 2(CN)(μ-dcpe)]PF 6 (6(PF 6)) and [{Cu(dppp)} 3(CN) 2(μ-dppp)] PF 6 (7(PF 6)), respectively. The hexanuclear complex [Cu(CN)(PCy 3)] 6 (8) was obtained by reacting CuCN with PCy 3 in the presence of sodium pyridine-2-thiolate. The UV-vis absorption spectrum of 1 in acetonitrile displays a weak shoulder at 245 nm (ε = 350 dm 3 mol -1 cm -1). For 3a, 3b, and 5, the intense absorption bands at λ max = 257-276 nm with ε values of (1.73-1.80) × 10 4 dm 3 mol -1 cm -1 are assigned to [ndσ* → (n + 1)pσ] transitions. Complexes 3a and 3b emit at λ max = 365 nm in CH 3CN (quantum yield ∼6 × 10 -3, lifetime ∼0.2 μs). The solid-state emission of 5 (λ max = 470 and 488 nm at 298 and 77 K) is red-shifted in energy from that of 4 (λ max = 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 λ max at 382-416 nm, which is assigned to the [3d → (4s, 4p)] triplet excited state. © 2005 American Chemical Society.