Syntheses and Characterizations of Coordination Polymers Constructed from 4-Pyridylacetic Acid

Assembly of 4-pyridylacetic acid hydrochloride (Hpya·HCl) and Zn(CH3COO)2·2H2O, 3CdSO4·8H2O,
or MnCl2·4H2O gave rise to five polymeric complexes {[Zn(C7H6NO2)2]·7H2O}n (1), [trans-M(C7H6NO2)2(H2O)2]n (M
= Zn, 2; Cd, 3; Mn, 5), and [cis-Cd(C7H6NO2)2(H2O)2]n (4), respectively. X-ray diffraction analyses reveal that complex
1 has a two-dimensional (2D) framework comprising rhombic grids of cavity dimensions 13.965 × 12.475 Å, and the
structure is extended into a three-dimensional network with large unique quasi-aperture by hydrogen bond and
π−π stacking interactions. Complexes 2, 3, and 5 possess a 2D structure consisting of alternate left and right helical
chains with rhombic grids of dimensions 15.933 × 5.692, 16.445 × 5.834, and 16.179 × 5.706 Å, respectively. Complex
4 has a 2D network constructed by right helical chains. Different crystallization conditions result in different
coordination geometries of metal centers in zinc (1 and 2) and cadmium complexes (3 and 4). Thermogravimetric
analyses of the complexes were performed.