Fluorescent copper(I) complexes: correlation of structural and emission characteristics of [{Cul(quin)2}2] and [Cu4I4(quin)4](quin = quinoline)

Abstract

Copper(I) iodide forms complexes of stoicheiometry 1:1:2 and 1:1:1 with quinoline(quin). [{Cul(quin)₂}₂](1)[monoclinic, space group A2/a, a= 25.620(6), b= 7.495(2), c= 20.314(4)Å, β= 111.60(1)°, Z= 8, R= 0.082 for 1 828 observed reflections] crystallizes with isolated rhombohedra of Cu₂I₂, each copper bound to the nitrogen atoms of two quinoline groups. Complex (1) displays a broad-band emission spectrum (λ_max. 620 nm) which is independent of temperature. [Cu₄I₄(quin)₄](2)[triclinic, space group P, a= 12.161(8), b= 15.142(8), c= 12.162(6)Å, α= 103.75(4), β= 109.54(5), γ= 107.18(5)°, Z= 2, R= 0.095 for 2 802 observed reflections] displays a distorted parallelogram of four copper atoms, bridged on opposite edges by iodine atoms and with two additional iodine atoms face-bridging sets of three copper atoms on opposite sides of the parallelogram. The room temperature emission band (λ_max. 625 nm) is broad and featureless whereas the 15-K spectrum displays considerable fine structure (490–620 nm).