Triazolate-based 3D frameworks and a 2D layer with centrosymmetric Cu7II, Cu5II, Cu4II clusters and tunable interlayer/interchain compactness: hydrothermal syntheses, crystal structures and magnetic properties

Four 1,2,3-triazolate-based coordination polymers (CPs) with varied dimensionality, different nuclearity numbers and core topologies, [Cu-4(mu-OH)(mu(3)-OH)(ta)(2)(btec)](n) (1), {[Cu-6(mu(3)-OH)(2)(ta)(8)(tp)]center dot 2.5H(2)O}(n) (2), {[Cu-5(mu(3)-OH)(2)(ta)(4)(ip)(2)]center dot 2H(2)O}(n) (3) and {[Cu-5(mu-OH)(2)(mu(3)-OH)(2)(ta)(2)(pa)(2)]center dot 2H(2)O}(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 centro-symmetric Cu-7(II) clusters, square-planar Cu-1(II) cores and tetratopic btec(4-) linkers for 1, a pillared-layered structure consisting of Cu-5(II) + Cu-1(II)-based coplanar layers and ditopic tp(2-) pillars for 2 as well as a micro-porous architecture derived from Cu-5(II) clusters and directional ip(2-) connectors for 3. In contrast, complex 4 exhibits an undulated two-dimensional (2D) layer with alternating Cu-4(II) + Cu-1(II) chains interconnected by anionic pa(2-) connectors. Crystallographically, the increment of the local nuclearity from Cu-4(II) up to Cu-7(II) 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 mu(3)-ta(-) mediator, these complexes 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.