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)]⋅2 H2O (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. Complex 1 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. Complexes 2 and 3 show similar three-dimensional frameworks, which feature a trinodal (2,3,5)-connected topology with the Schläfli symbol of (42⋅6⋅84⋅102⋅12)(42⋅6)(8). Complex 4 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. Complex 5 reveals a one-dimensional double-strand chain, whereas complexes 68 exhibit similar two-dimensional double-layer structures with (42⋅6)(43⋅6⋅84⋅102)(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 complexes 7 and 8, and the electrochemical and photocatalytic properties of complexes 16 have also been investigated in detail.