Anion-Dominated Copper Salicyaldimine Complexes—Structures, Coordination Mode of Nitrate and Decolorization Properties toward Acid Orange 7 Dye

A salicyaldimine ligand, 3-tert-butyl-4-hydroxy-5-(((pyridin-2-ylmethyl)imino)methyl)benzoic acid (H(2)L(salpyca)) and two Cu(II)−salicylaldimine complexes, [Cu(HL(salpyca))Cl] (1) and [Cu(HL(salpyca))(NO(3))](n) (2), have been synthesized. Complex 1 has a discrete mononuclear structure, in which the Cu(II) center is in a distorted square-planar geometry made up of one HL(salpyca)(−) monoanion in an NNO tris-chelating mode and one Cl(−) anion. Complex 2 adopts a neutral one-dimensional zigzag chain structure propagating along the crystallographic [010] direction, where the Cu(II) center suits a distorted square pyramidal geometry with a τ value of 0.134, consisted of one HL(salpyca)(−) monoanion as an NNO tris-chelator and two NO(3)(−) anions. When the Cu∙∙∙O semi coordination is taken into consideration, the nitrato ligand bridges two Cu(II) centers in an unsymmetrical bridging-tridentate with a μ, κ(4)O,O′:O′,O″ coordination. Clearly, anion herein plays a critical role in dominating the formation of discrete and polymeric structures of copper salicyaldimine complexes. Noteworthy, complex 2 is insoluble but highly stable in H(2)O and various organic solvents (CH(3)OH, CH(3)CN, acetone, CH(2)Cl(2) and THF). Moreover, complex 2 shows good photocatalytic degradation activity and recyclability to accelerate the decolorization rate and enhance the decolorization performance of acid orange 7 (AO7) dye by hydrogen peroxide (H(2)O(2)) under daylight.