A series of multi-responsive viologen-based alkaline-earth metal coordination complexes: Thermochromism, photochromism, and vapochromism

Abstract

Due to their external stimuli responsive properties, chromic materials have attracted considerable interest in various fields. In this work, a series of alkaline-earth metal based coordination complexes constructed from viologen derivative, [Mg(H2O)6·(bdpbpy)·H2O] (1), [Ca(bdpbpy)(H2O)4] (2), [Sr(bdpbpy)(H2O)4] (3), [Ba(bdpbpy)(H2O)4] (4), (H4bdpbpy·2Cl = 1,1-bis(3,5-dicarboxyphenyl)-4,4-bipyridinium chloride) have been synthesized and characterized by elemental analyses, FT-IR spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis. Because of electron transfer between the oxygen atom of carboxylate and bipyridinium moieties, compounds 1–4 exhibit reversible thermochromic and photochromic properties upon thermo treatment or Uv-vis irradiation. Due to presence of electron-deficient bipyridinium moieties (Lewis acidic sites), these compounds can be used as potential colorimetric sensor for ethanediamine vapor detection. The multi-responsive performances of compounds 1–4 can widen their applications in some particular systems that call for color changing properties of external stimuli.