Photophysical properties of homobimetallic Cu(i)–Cu(i) and heterobimetallic Cu(i)–Ag(i) complexes of 2-(6-bromo-2-pyridyl)-1H-imidazo[4,5-f][1,10]phenanthroline

Abstract

α-Diimine-Cu(I)–diphosphine complexes are good phosphorescence materials at room temperature; however, so far, most reported systems have been mononuclear and homonuclear Cu(I) complexes, and little attention has been paid to heteronuclear Cu(I) complexes. On the other hand, some of the heteronuclear Cu(I)–Ag(I) complexes have displayed enhanced luminescence properties compared to homonuclear analogues, and this inspires us to explore the synthesis and luminescence behaviour of hetronuclear α-diimine-Cu(I)–Ag(I)–diphosphine complexes. Herein, 2-(6-bromo-2-pyridyl)-1H-imidazo[4,5-f][1,10]phenanthroline (bpipH) and its four homobinuclear Cu(I)–Cu(I) complexes (1a, 2a, 1b and 2b) and two heterobinuclear Cu(I)–Ag(I) complexes (1c and 2c) were synthesized. All the Cu(I) and Ag(I) centers show typical distorted tetrahedral configurations. Both homobinuclear complexes (1b and 2b) and heterobinuclear analogues (1c and 2c) of deprotonated bpipH ligands show better luminescence than the corresponding homobinuclear complexes (1a and 2a) of the neutral bpipH. Most importantly, compared with the corresponding homobinuclear complexes, heteronuclear Cu(I)–Ag(I) complexes distinctly show further enhanced luminescence and dual emission bands (501 and 601 nm for complex 1c, and 506 and 603 nm for complex 2c), which probably result from ³(LL + ML + IL)CT transitions. Here, the better emission behaviour of heteronuclear α-diimine-Cu(I)–Ag(I)–diphosphine complexes proves that introducing Ag(I) ions to the α-diimine-Cu(I)–diphosphine systems is worth exploring to enhance the luminescence intensity and tune the luminescence colors.