d10 Metal complexes assembled from isomeric benzenedicarboxylates and 3-(2-pyridyl)pyrazole showing 1D chain structures: syntheses, structures and luminescent properties

Abstract

Seven new d¹⁰ metal coordination polymers with isomeric benzenedicarboxylates and 3-(2-pyridyl)pyrazole ligands, [Zn₂L₂(1,2-BDC)(H₂O)]_n (1), {[Cd₂(HL)₂(1,2-BDC)₂]·H₂O}_n (2), [Cd(HL)(1,2-BDC)(H₂O)]_n (3), [Zn(HL)(1,3-BDC)(H₂O)·3H₂O]_n (4), [Cd₂L₂(1,3-BDC)(H₂O)]_n (5), [Zn(HL)₂(1,4-BDC)]_n (6) and [Cd(HL)₂(1,4-BDC)]_n (7) (BDC = benzenedicarboxylate, HL = 3-(2-pyridyl)pyrazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that each complex takes a different one-dimensional (1D) chain structure. In 1–7, the BDCs act as bridging ligands, exhibiting rich coordination modes to link metal ions. The three BDC isomers exhibit different coordination modes: µ₁-η¹:η¹/µ₃-η²:η¹, µ₃-η¹:η²/µ₃-η²:η¹, µ₂-η¹:η¹/µ₁-η¹:η⁰ and µ₁-η¹:η¹/µ₁-η¹:η⁰ for 1,2-BDC, µ₁-η¹:η¹/µ₁-η¹:η⁰ and µ₁-η¹:η⁰/µ₂-η²:η¹ for 1,3-BDC, and µ₁-η¹:η⁰/µ₁-η⁰:η¹, µ₁-η¹:η⁰/µ₁-η¹:η⁰ and µ₁-η¹:η¹/µ₁-η¹:η¹ for 1,4-BDC, respectively. In these complexes, HL acts as a simple bidentate chelate ligand (in 2, 3, 4, 6 and 7), similar to 2,2′-bipyridine, or as a tridentate chelate-bridging ligand (in 1 and 5) via deprotonation of the pyrazolyl NH group and coordination of the pyrazolyl N atom to a second metal ion. The structural differences indicate that the backbone of such dicarboxylate ligands plays an important role in governing the structures of such metal–organic coordination architectures, and the chelating bipyridyl-like ligand HL leads to the formation of these coordination polymers with one-dimensional structures by occupying the coordination sites of metal ions. Moreover, the photoluminescent properties of complexes 1–7 were also studied in the solid-state at room temperature.