SCHEDULED MAINTENANCE
Four linear CuII3 subunit-based coordination polymers with various inter-subunit connections, spin ground-states and intra-/inter-subunit magnetic couplings†
Abstract
Four new 4-amino-1,2,4-triazole (atr)-based coordination polymers, {[Cu2(atr)(H2O)(μ-OH)2(pa)]·H2O}n (1), {[Cu3(atr)2(H2O)2(μ-OH)2(npa)2]·2H2O}n (2), {[Cu3(atr)5(dca)(μ-OH)(ClO4)2](ClO4)2}n (3) and {[Cu3(atr)2(H2O)(μ3-OH)(μ-OH)2(spa)]·1.5H2O}n (4) (pa2− = phthalate, npa2− = 3-nitrophthalate, dca− = dicyanamide and spa3− = 4-sulfophthalate), were successfully obtained by varying the carboxylate- and cyanide-modified magnetic bridges. Structural determinations reveal that the former three samples are bent one-dimensional chains constructed from linear CuII3 subunits and different inter-subunit connections. In 1, linear {Cu3(μ-N1,N2-atr)2(μ-OH)2}4+ and {Cu3(μ-COO)2(μ-OH)2}4+ subunits are alternately connected in a sharing-vertex manner to give a ferrimagnetic S = 1/2 spin ground-state. The linear {Cu3(μ-N1,N2-atr)2(μ-OH)2}4+ building block of 2 is repeatedly bridged by pairs of single-atom bridging carboxylate groups of the npa2− ligand leading to a paramagnetic S = 1/2 spin ground-state. By contrast, each linear {Cu3(μ-N1,N2-atr)4}6+ core in 3 is periodically propagated by four-fold heterobridges (μ-OH−, μ-ClO4−, μ-N1,N2-atr and μ-dca−) to generate an overall diamagnetic S = 0 spin ground-state. Complex 4 is a three-dimensional pillared-layer framework composed of linear {Cu3(μ-N1,N2-atr)2(μ-OH)2}4+-based layers and ditopic spa3− connectors, which exhibits a ferrimagnetic S = 1/2 spin ground-state and a metamagnetic transition resulting from the competition between the weak interchain/interlayer antiferromagnetic interaction and the enhanced external magnetic field. In addition, different intra- and inter-subunit magnetic strengths are observed in 1–4 with the coupling constants 182 < −Jintra < 43 and −127 < Jinter < 51.2 cm−1. These interesting magnetostructural results are significant and helpful for the cyclic polyazolate-based magnetic materials.
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