Luminescence Behavior of Cationic and Neutral Cu^I Complexes of Phosphine and Pyridine Embedded 1,2,3-Triazole

Synthesis of a potentially polydentate, phosphine and pyridine embedded 1,2,3-triazole, o-Ph₂P(C₆H₄)C(CH)-1,2,3-N₃(CH₂)(Py) (1) (here onward referred to as "P^∩N₃^∩N") and its copper complexes are described. Reactions of 1 with CuX yielded mononuclear [Cu{(P^∩N₃^∩N)₂-κ²-P,N}]X (2 - 4; X = I, CuBr₂ and CuCl₂) and dinuclear [Cu₂{(P^∩N₃^∩N)₂-κ⁴-P,N,N,N}]X (5 X = OTf, 6 X = BF₄) complexes. Interestingly, the cationic complex [Cu{(P^∩N₃^∩N)₂-κ²-P,N}]I (2) in acetonitrile changes into neutral complex [Cu₃(μ₂-I)₂(μ₃-I)(NCCH₃){(P^∩N₃^∩N)-κ⁴(μ₂-P,N)(μ₂-N,N)}](7), which on addition of dichloromethane reverts back to the cationic form. The photoluminescent characteristics of cationic complexes are significantly impacted by the nature of counteranions and hence the corresponding photoluminescence quantum yields. Cationic complex 2 showed an increase in quantum yield and lifetime on changing over to neutral complex 7. TD-DFT calculations also assisted in assessing the photophysical properties.