Multifunctional sensing ability of a new Pt/Zn-based luminescent coordination polymer

Abstract

We synthesized a new Pt/Zn-based coordination polymer, {Zn[Pt(CN)₂(5,5′-dcbpy)]·4H₂O}_n, (5,5′-H₂dcbpy = 5,5′-dicarboxy-2,2′-bipyridine), which exhibits reversible colour changes in response to temperature change or exposure to chemical vapours and liquids. Such chromic behaviour shows promise for sensing not only changes in temperature but also for detecting chemical solvents and vapours. The single crystal X-ray structure indicates that one-dimensional coordination polymeric chains formed by an alternating arrangement of [Zn(H₂O)₃]²⁺ and [Pt(CN)₂(5,5′-dcbpy)]²⁻ stacked to produce moderate metallophilic interactions between the Pt(II) ions. Thermogravimetric analysis and water vapour adsorption measurements show that both the crystal water and water coordinated to Zn(II) ions can be removed and re-adsorbed reversibly by heating or under vacuum. Emission spectra at various temperatures and/or in the presence of vapours or liquids reveal that the complex exhibits thermochromic and solvatochromic-like behaviours, with the emission band shifting between 616 and 671 nm. IR spectroscopy and powder X-ray diffraction measurements suggest that this multichromic behaviour is a result of the cooperative phenomena of water adsorption/desorption around the Zn(II) ions and the modification of the metallophilic interaction.