Sb- and Bi-based coordination polymers with N-donor ligands with and without lone-pair effects and their photoluminescence properties
Fifteen new sublimable Sb- and Bi-based chlorido, bromido and iodido coordination polymers (CPs) with linear bispyridyl ligands are presented in this work and compared in terms of their crystal structures and photoluminescence properties. The Sb-CPs occur in two structural motifs: 1∞[Sb2X6(L)2] (X: Cl (a), Br (b), I (c); L: 1,2-bis(4-pyridyl)ethylene (bpe) (1), 1,2-bis(4-pyridyl)ethane (bpa) (2), 4,4’-bipyridine (bipy) (X: Br, I; 3)) with two polymorphs, both showing neglectable stereochemical demand of the lone-pair and 1∞[SbCl4(bipy)] (3a) featuring a stereochemically active lone pair with significant 5p-contribution at SbIII. This is accompanied by differences in the coordination polyhedra being octahedral for high s character, whereas a high p-character of the lone pair results in a square pyramid as coordination sphere. The Bi-CPs are constituted by the general formula 1∞[Bi2X6(L)2] (X: Cl (a), Br (b), I (c); L: 1,2-bis(4-pyridyl)ethylene (bpe) (4), 1,2-bis(4-pyridyl)ethane) (bpa) (5)) and thus show no significant 6p-character of the lone-pairs. For parallels and differences between the SbIII- and BiIII-CPs, both are compared in terms of structure and luminescence properties, as well as to related literature known CPs. Altogether, this comparison of structures and properties allows for new insights into the photoluminescence mechanisms of Sb and Bi-containing CPs. Intriguing hints on a participation of inter-valence charge transfer transitions in E3+-pairs (E: Sb, Bi) were observed in the Sb- and Bi-constituted coordination polymers.