Syntheses and luminescence behavior of tetranuclear copper(I) diynyl complexes: X-ray crystal structure of [Cu4(PPh3)4(μ3-η-CCCCPh)4]

A series of luminescent tetranuclear cuboidal copper(I) diynyl complexes, Cu₄(PAr₃)₄(μ₃-η¹-CCCCR′)₄] (Ar=Ph, R′=Ph, C₆H₄CH₃-p, C₆H₄OCH₃-p; Ar=C₆H₄CH₃-p, C₆H₄F-p, R′=Ph) has been synthesized and characterized. The X-ray crystal structure of Cu₄(PPh₃)₄(μ₃-η¹-CCCCPh)₄] has been determined. The origin of the low-energy emission in the complexes is assigned as derived from a metal-centered 3d⁹4s¹ state, mixed with LMCT diynyl→Cu₄] and IL π-π*(diynyl)] states.