A novel kind of coordination polymers employing 2,5-diamino-1,4-benzenedithiol as a bridging ligand: synthesis, structure, optical and magnetic properties

Abstract

A serials of organo-soluble transition metal–DABDT coordination polymers were successfully synthesized by the coordination of transition metal ions and DABDT. These coordination polymers were characterized by FTIR, TGA, XRD, UV-Vis spectroscopy, fluorescence spectroscopy, TEM, and vibrational sample magnetometry. Results showed that DABDT coordinated transition metal ions by its amino and sulfydryl groups. The coordination polymers of Co–DABDT, Ni–DABDT, Cu–DABDT and Zn–DABDT exhibited crystal or semi-crystal characteristics, while Fe–DABDT was almost amorphous. The synthesized coordination polymers were soluble in the mixed solvent of DMF and DMSO (volume ratio, 1 : 1). The main UV-Vis absorptions of the as-synthesized transition metal–DABDT coordination polymers were below 400 nm in the ultraviolet region. These coordination polymers emitted cyan light in the DMF and DMSO mixed solution, especially for Zn–DABDT, which emitted obviously stronger cyan light than the other coordination polymers. Fe–DABDT exhibited superparamagnetic character in the approximate range of −5000 G to +5000 G and simple paramagnetic character in the other fields. Co–DABDT and Ni–DABDT followed simple paramagnetic behavior. TEM analysis showed that Ni–DABDT were porous nanospheres with an average diameter of about 69 nm. The rigid molecules of Ni–DABDT arrayed in parallel in the coordination polymer sphere. And Co–DABDT also showed a lamellar structure. The rigid coordination polymer molecules arrayed in parallel due to the formation of hydrogen bond between the –SH and –NH₂ groups of adjacent molecular chains in the same plane. And the arrangement between different molecular layers was stacked layer upon layer on account of the π–π stacking of the coordination polymer chains. The solubility of the prepared coordination polymers enabled us to carry out a first-time study on their photophysical behavior. What's more, this is the first time to report the planar and lamellar structure of the transition metal-DABDT coordination polymers through TEM analysis.