From Simple to Complex: Topological Evolution and Luminescence Variation in a Copper(I) Pyridylpyrazolate System Tuned via Second Ligating Spacers

By systematically varying the geometric length and electronic properties of the second ligating ligands of halogen (Cl–, Br–, and I–) and pseudohalogen (CN–, SCN–, and N3–) anions, we synthesized 11 isomeric/isostructural copper(I) complexes: [Cu2(L3-3)I]n (1), [Cu2(L4-4)Br]n (2-Br), [Cu2(L4-4)Cl]n (2-Cl), [Cu2(L3-4)(CN)]n (3), [Cu2(L3-3)(CN)]n (4), [Cu3(L4-4)(CN)2]n (5), {[Cu2(L4-4)Br]2·CuBr}n (6-Br), {[Cu2(L4-4)Cl]2·CuCl}n (6-Cl), [Cu2(L4-4)(SCN)]n (7α-SCN), [Cu2(L4-4)(SCN)]n (7β-SCN), and [Cu2(L4-4)(N3)]n (7α-N3). These structures are based on a series of isomeric pyridylpyrazole ligands, namely, 3,5-bis(3-pyridyl)-1H-pyrazole (HL3-3), 3-(3-pyridyl)-5-(4-pyridyl)-1H-pyrazole (HL3-4), and 3,5-bis(4-pyridyl)-1H-pyrazole (HL4-4), and their structural features range from 1-D (1), 2-D (2), and 3-D noninterpenetration (3), to 3-D 2-fold interpenetration (4 and 5), to 3-D self-catenation (6 and 7), exhibiting a trend from simple to complex with dimension expansion and an interpenetrating degree increase. The five most complex structures (6 and 7) with self-catenated networks are based on 2-fold interpenetrated networks linked via appropriate second ligating spacers (Cl–, Br–, SCN–, and N3–), representing a strategy to construct self-catenated coordination polymers through cross-linking interpenetrated frameworks. Moreover, these complexes exhibit strong photoluminescence, which is mainly ascribed to CuI-related charge transfers (MLCT, MC, and MMLCT) regulated by the electronic properties of halogen or pseudohalogen. The topological evolution and luminescence variation presented in this work open an avenue to understanding the luminescence origin and the structure–property relationship of luminescent coordination polymers.