Metal(II)-Organic Coordination Polymers Modulated by Two Isomeric Semirigid Bis-Pyridyl-Bis-Amide Ligands: Structures, Fluorescent Sensing Behavior, and Selective Photocatalysis

A series of metal-organic coordination polymers based on two isomeric semirigid bis-pyridyl-bis-amide ligands and 5-methylisophthalic acid (5-H2MIP), namely, [Cu(3-bpah)(5-MIP)]2H(2)O (1), [Ni(3-bpah)(5-MIP)]H2O (2), [Co(3-bpah)(5-MIP)]H2O (3), [Cu(4-bpah)(5-MIP)(H2O)] (4), [Ni(4-bpah)(5-MIP)(H2O)]H2O (5), [Co(4-bpah)(5-MIP)] (6), [Zn(4-bpah)(5-MIP)] (7), and [Cd(4-bpah)(5-MIP)] (8) (3-bpah=N,N-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 4-bpah=N,N-bis(4-pyridinecarboxamide)-1,2-cyclohexane), have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, thermogravimetric analysis, and single-crystal X-ray diffraction analyses. The title coordination polymers display versatile structural features with one-, two-, and three-dimensional frameworks. Complex1 exhibits a two-dimensional (4,4) network named as type c, which is constructed from the arched 3-bpah and 5-MIP anions with alternating orientations. Complexes2 and 3 show similar three-dimensional frameworks, which feature a trinodal (2,3,5)-connected topology with the Schlafli symbol of (4(2)68(4)10(2)12)(4(2)6)(8). Complex4 exhibits an undulated two-dimensional (4,4) network of type b, in which the twist angles of the ligands are different from those of 1. Complex5 reveals a one-dimensional double-strand chain, whereas complexes6-8 exhibit similar two-dimensional double-layer structures with (4(2)6)(4(3)68(4)10(2))(4) topology. The influence of semirigid bis-pyridyl-bis-amide ligands and central metals on the structures of the title complexes has been reported. The fluorescent sensing behaviors of complexes7 and 8, and the electrochemical and photocatalytic properties of complexes1-6 have also been investigated in detail.