Triazolate-based 3D frameworks and a 2D layer with centrosymmetric Cu(II)7, Cu(II)5, Cu(II)4 clusters and tunable...

Four 1,2,3-triazolate-based coordination polymers (CPs) with varied dimensionality, different nuclearity numbers and core topologies, [Cu4(μ-OH)(μ3-OH)(ta)2(btec)]n (1), {[Cu6(μ3-OH)2(ta)8(tp)]·2.5H2O}n (2), {[Cu5(μ3-OH)2(ta)4(ip)2]·2H2O}n (3) and {[Cu5(μ-OH)2(μ3-OH)2(ta)2(pa)2]·2H2O}n (4) (ta = 1,2,3-triazolate, btec = 1,2,4,5-benzenetetracarboxylate, tp = terephthalate, ip = isophthalate and pa = phthalate), were hydrothermally synthesized by varying the numbers and positions of the carboxylate group appended on the phenyl tether, and structurally and magnetically characterized. The former three entities are three-dimensional (3D) robust frameworks with a (4(4)·6(2))(4(11)·6(5))2(4(13)·6(10)·8(5)) topological net containing centrosymmetric Cu(II)7 clusters, square-planar Cu(II)1 cores and tetratopic btec(4-) linkers for 1, a pillared-layered structure consisting of Cu(II)5 + Cu(II)1-based coplanar layers and ditopic tp(2-) pillars for 2 as well as a microporous architecture derived from Cu(II)5 clusters and directional ip(2-) connectors for 3. In contrast, complex exhibits an undulated two-dimensional (2D) layer with alternating Cu(II)4 + Cu(II)1 chains interconnected by anionic pa(2-) connectors. Crystallographically, the increment of the local nuclearity from Cu(II)4 up to Cu(II)7 in 1-4 benefits greatly from the synergistic co-coordination of the hydroxyl group and the coplanar ta(-) ligand towards the metal ion, and the interlayer/interchain compactness is significantly tuned by the position isomerism of the dicarboxylate moieties. Due to the antiferromagnetic coupling in the local clusters and the asymmetric superexchange by μ3-ta(-) mediator, these complexes 4 exhibit different spin ground states (paramagnetic S = 1 and 1/2, ferrimagnetic S = 1/2 as well as spin canting) at low temperatures, which are informative for polynuclear-based magnetic materials.