Synthesis, structures and photophysical properties of Cu(I) phosphine complexes with various diimine ligands

A series of triphenylphosphine Cu(I) complexes with various diimine ligands, [Cu(N–N)(PPh₃)₂](ClO₄) [N–N = dmp (2); Ph₂Phen (3); Ph₂dmp (4); dpq (5); dppz (6); phenCN (7); phenOH (8)] are synthesized by the ligand substitution reactions of [Cu(MeCN)₄](ClO₄) with 2 mole equiv. of PPh₃ ligand and 1.2 mole equiv. of diimine ligand. {Cu(dpq)[P(XPh)₃]₂}(ClO₄) [X = Me (5a); OMe (5b); Cl (5c)] and {Cu(phenOH)[P(XPh)₃]₂}(ClO₄) [X = Me (8a); OMe (8b)] are also obtained by using various substituted phosphine ligands. These mixed-ligand complexes have been characterized using ¹H and ³¹P NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Three of these complexes have been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been studied. These complexes exhibit MLCT phosphorescence with emission energy, lifetimes and quantum yields showing strong dependence on the nature of diimine and phosphine ligands. In particular, both the electronic and steric effects of the substituting groups in phosphine ligands are also found to affect the emission properties of the complexes. Our study provides structural-properties information for the future design of luminescent Cu(I) complexes.