pH and Auxiliary Ligand Influence on the Structural Variations of 5­(2′-Carboxylphenyl) Nicotate Coordination Polymers

2016-02-20T20:09:41Z (GMT) by Jinzhong Gu Zhuqing Gao Yu Tang
A ligand 5-(2′-carboxylphenyl) nicotic acid (H2cpna) has been successfully applied to construct a series of coordination complexes {[Cd­(Hcpna)2(H2O)2]·3H2O}n (1), [Cd­(cpna)­(H2O)]n (2), [M­(cpna)­(2,2′-bipy)­(H2O)]n (M = Cd (3), Co (4), and Mn (5)), [Co­(cpna)­(phen)­(H2O)]n (6), [Mn­(cpna)­(phen)­(H2O)]n (7), {[Nd­(Hcpna)­(cpna)­(H2O)2]·3H2O}n (8), and {[Ln­(Hcpna)­(cpna)­(phen)]·2H2O}n (Ln = Pr (9), Nd (10), Eu (11), and Gd (12), 2,2′-bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline) under hydrothermal conditions. By adjusting the reaction pH, H2cpna ligand is partially deprotonated to form Hcpna in 1 and completely deprotonated to create cpna2– in 27, and both forms are observed in 812. Complexes 15 and 8 possess two-dimensional (2D) layered structures, which are further extended into 3D metal–organic supramolecular frameworks by C–H···O hydrogen bond and/or π–π stacking interactions. Complexes 6, 7, and 912 exhibit one-dimensional (1D) chain structures, which further build three-dimensional (3D) supramolecular architecture via C–H···O hydrogen-bonding and/or π–π stacking interactions. The results revealed that the pH value of the reaction system and auxiliary ligand play an important role in determining the structures of the complexes. Magnetic susceptibility measurements indicate that compounds 410 and 12 have dominating antiferromagnetic couplings between metal centers. Furthermore, thermal stabilities for 112 and luminescent properties for 13, and 11 are also discussed in detail.