Five new isomorphic coordination polymers with large conjugated ligands: Synthesis, crystal structures and performances

Five new coordination compounds with isomorphic frameworks, {[M(cpp)2(H2O)2].3H2O}n [M = Co (1), Cd (2), Mn (3), Ni (4), Zn (5)], were successfully synthesized through the reactions of 1-(4-carboxyphenyl)-3-(pyrazin-2yl)pyrazole (Hcpp) and a series of transition metal salts under the solvo-thermal conditions. Compounds 1-5 were characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectra and thermogravimetric analysis. Isomorphic compounds 1-5 display an abnormal two-dimensional helical layer containing a M4(cpp)4 cavity with the dimension of 26.21 x 8.39 angstrom 2. Variable-temperature magnetic susceptibility measurements indicate weak antiferromagnetic interactions with Curie constant (2.08 cm3 K mol-1) and Weiss constant (-6.90 K) in compound 1. Compounds 2 and 5 show apparently blue light emission, wherein the sensing responses to small molecules, inorganic anions and metal cations indicate compound 5 can be used as a multifunctional fluorescence probe to detect aniline, Fe3+, CrO42- and Cr2O72- through fluorescence quenching and the corresponding quenching mechanisms are proposed.

Automated summary

In this study, five new coordination compounds with isomorphic frameworks were successfully synthesized and characterized. One of the compounds was found to be a multifunctional fluorescence probe.