Phosphorescent Acentric Cuprous Halide Coordination Polymers for Nolinear Optical Materials

Three phosphorescent acentric cuprous halide coordination polymers, namely, [Cu2(pyt)Cl] (1), [Cu2(pyt)Br] (2), and [Cu5(pytH)3Cl5] (3) have been synthesized through the treatment of copper halides with achiral ligand pyridine-4-thiol (pyHt) by the hydro(solvo)thermal method. Complexes 1 and 2 are isostructural and exhibit three-dimensional (3-D) pillar-layered structures constructed by [Cu2SCl]∞/[Cu2SBr]∞ layers and pyridine pillars. The [Cu2SCl]∞ layer can be viewed as a fusion of zigzag [CuS]∞ and [CuCl]∞ chains. Alternately, the [Cu2SCl]∞ layers can be viewed as a fusion of six-membered Cu3S2Cl and Cu3Cl2S rings. Complex 3 shows a [Cu5S3Cl]∞ chain decorated by terminal chlorides and pyridine rings, in which the six Cu(I) atoms are linked by three μ3-S atoms and one μ3-Cl into a Cu6S3Cl cage, and a fusion of Cu6S3Cl cages via sharing Cu sites results in a one-dimensional [Cu5S3Cl]∞ chain. At ambient temperature, 1, 2, and 3 show a strong yellow or red emission assigned from ligand-to-metal charge transfer (LMCT) and/or metal-to-ligand charge-transfer (MLCT) character and a weak higher energy blue emission band assigned from halide to pyridine π* charge transfer. Their noncentrosymmetric structures are confirmed by measurement of second harmonic generation efficiency.