New luminescent copper(I) halide complexes containing Rb+ complexes of 18-crown-6 as counter ions prepared from zerovalent copper

Abstract

Treatment of zerovalent copper with NH4X (X = I, Br or SCN) in the presence of RbI and 18-crown-6 (18c6), in acetonitrile, in air, afforded a diversity of crystalline products in which halogeno- or pseudo-halogeno-cuprate(I) anions co-precipitate with the geometrically rigid crown ether cation [Rb(18c6)]+. Four complexes [{Rb(18c6)}2MeCN][Cu4I6] 1, [Rb(18c6)][Rb(18c6)(MeCN)3]2[{Rb(18c6)}6Cu4I7][Cu7I10]22, {[Rb(18c6)][Cu3I3Br]}∞3 and {[Rb(18c6)][Cu2(SCN)3]}∞4 have been isolated and characterised. Formation of the copper(I) species here is believed to be an autocatalytic process catalysed by the formation of copper(II) compounds in situ. The anions present in the initial mixture have a profound effect upon metal–halogen framework formation. There is a competition between the strongly co-ordinating anions that leads to the partial or complete replacement of iodine by bromine or thiocyanate in 3 and 4, respectively. Complex 1 contains a discrete disordered [Cu4I6]2− species sandwiched between the [Rb(18c6)]+ cations. The structural motif of 2 consists of ensembles of two [Rb(18c6)(MeCN)3]+ and one [Rb(18c6)]+ cation, the bulky supramolecular cation [{Cs(18c6)}6Cu4I7]3+ and crown-like [Cu7I10]3− clusters in which seven copper atoms describe a hexagonal pyramid. In the mixed halogenocuprate(I) anion [Cu3I3Br]−∞ characterised in 3 all the copper atoms of the polymeric chain lie in the same plane; the halides bridge the alternate sides of the polymer. The Br atoms form bridges between [Cu3I3]n chains and the [Rb(18c6)]+ cations. The ability of the SCN group to act as a bridge gives rise to a one-dimensional structure for 4 which contains two copper(I) atoms each with a different stereochemistry. Complexes 1, 2 and 3 display a change in emission spectrum with temperature in the solid state.