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)]∞ (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(μ-dcpm)2][Ag(CN)2]2·(CH3OH)2 (3a·(CH3OH)2) and [Ag2(μ-dcpm)2][Ag(CN)2]2 (3b), respectively. The similar reaction of CuCN
with PCy3 afforded the polymeric compound [{(Cy3P)Cu(CN)}3]∞ (4), whereas treatment of CuCN with dcpm gave
[Cu2(μ-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)(μ-dcpe)]PF6 (6(PF6)) and
[{Cu(dppp)}3(CN)2(μ-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 (ε = 350 dm3 mol-1 cm-1). For 3a, 3b, and 5, the intense
absorption bands at λmax = 257−276 nm with ε values of (1.73−1.80) × 104 dm3 mol-1 cm-1 are assigned to
[ndσ* → (n + 1)pσ] transitions. Complexes 3a and 3b emit at λmax = 365 nm in CH3CN (quantum yield ∼6 ×
10-3, lifetime ∼0.2 μs). The solid-state emission of 5 (λmax = 470 and 488 nm at 298 and 77 K) is red-shifted in
energy from that of 4 (λmax = 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 λmax at 382−416 nm, which is assigned to the [3d → (4s,
4p)] triplet excited state.