Luminescent Triphosphine Cyanide d¹⁰ Metal Complexes

Coinage metal cyanides efficiently react with a triphosphine. PPh₂C₆H₄-PPh-C₆H₄PPh₂ (P³). to give the complexes M(P³)CN, where M = Cu (1), Ag (2), and Au (3), which can further interact with coordinatively unsaturated metal centers [M(P³)]⁺ to give the homobimetallic [(P³)M-CN-M(P³)]⁺X^- [M = Cu (4a with X^- = CF₃SO₃ ^- and 4b with X^- = BF₄ ^-), Ag (5)] or heterometallic [(P³)Au-CN-Ag(P³)]⁺ (6) species. Extension of this approach also provided the trinuclear complex [(P³)Cu-NC-Au-CN-Cu(P³)]⁺ (7). Compounds 1-5 were characterized in the solid state by X-ray crystallography. The NMR spectroscopic studies revealed that all of the complexes except 6 retain their structures in solution. The title compounds are luminescent in the solid state, with quantum yields ranging from 8 to 87%. The observed photoemission originates mainly from the metal-to-ligand charge-transfer states according to time-dependent density functional theory computational studies. The crystalline bimetallic Cu complexes 4a/4b demonstrate extremely high sensitivity of the emission intensity to molecular O₂ (K_SV1 = 639 atm^-1 and LOD = 0.010% for 3 times the signal-to-noise ratio).