Structural diversity and properties of M(ii) phenyl substituted pyrazole carboxylate complexes with 0D-, 1D-, 2D- and 3D frameworks

Eight new metal complexes with two kinds of phenyl substituted pyrazole carboxylic acid, [Ni(HL1)2(H2O)2] (1), [Cu(HL1)2(H2O)2] (2), [Zn(HL1)2] (3), [Ni(HL2)2(H2O)2] (4), [Ni(HL2)2(HL3)2] (5), [Cu(HL2)2]·2H2O (6), [Zn(HL2)2] (7), [Zn2(HL2)2(L2)] (8) [H2L1 = 5-phenyl-1H-pyrazole-3-carboxylic acid; H2L2 = 3-phenyl-1H-pyrazole-4-carboxylic acid; HL3 = 3-phenyl-1H-pyrazole] were prepared by hydro/solvothermal reactions and structurally characterized. Complexes 1 and 2 have monomeric structures; 3 and 4 exhibit 1-D zig-zag chains; 5 and 6 possess 2D layer structures consisting of rhomboid grids; 7 features a 2-fold interpenetrated 3-D diamondoid framework; while complex 8 holds a 3-D NaCl-like framework. Hydrogen bonding and aromatic π–π stacking interactions link the eight complexes into 2-D (1–3) or 3-D (4–8) supramolecular networks, of which 5, 6 and 8 contain single, single and double-stranded helical chains, respectively. The thermal stabilities of complexes 1–8 and photophysical properties of complexes 3 and 7 were investigated.