Synthesis, Crystal Structure, and Electron Paramagnetic Resonance Investigations of Heteronuclear CoII/ZnII and CoII/CdII Coordination Polymers

The crystal structures of five new Co-II, Zn-II, and Cd-II coordination polymers based on pyridine-substituted triazolyl carboxylates are reported. The two isomorphous compounds (3)(infinity)[M(Me-3py-pba)(2)] (M = Zn, Co) possess {6(6)} topology (dia). In order to obtain heteronuclear compounds, we synthesized Co-II-substituted Zn-II and Co-II/Cd-II coordination polymers. At T=5 K, the powder samples of the diamagnetically diluted Co-II/Zn-II and Co-II/Cd-II systems [Co/(Zn,Cd) approximate to 0.01] show intense electron paramagnetic resonance spectra, which were analyzed with an effective spin of S' = 1/2. The g tensor as well as the Co-59 hyperfine tensor A(Co) are strongly anisotropic. The g tensor components are used to gain information about the symmetry of the Co-II coordination sphere and covalency effects. Differential thermal analysis/thermogravimetry-mass spectrometry and temperature-dependent powder X-ray diffraction studies reveal high thermal stability of the three-dimensional coordination polymers up to 390 degrees C.