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)]⋅4H 2 O} n , (5,5'-H 2 dcbpy = 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 10 chemical solvents and vapours. The single crystal X-ray structure indicates that one-dimensional coordination polymeric chains formed by an alternating arrangement of [Zn(H 2 O) 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 15 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 20 of the metallophilic interaction.

Vapochromic Platinum(II) Complexes: Crystal Engineering toward Intelligent Sensing Devices

“…We reported the structures and chromic behaviors of coordination polymers composed of a Pt II metalloligand, [Pt(CN) 2 (5,5′‐H 2 dcbpy)] ( 10 ), an isomer of 6 , and various divalent metal ions, {M[Pt(CN) 2 (5,5′‐dcbpy)] · n H 2 O} ( 10 ‐M; M = Zn 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ; 5,5′‐H 2 dcbpy = 5,5′‐dicarboxy‐2,2′‐bipyridine) 38. X‐ray diffraction studies of the tetrahydrate Zn complex 10 ‐Zn · 4H 2 O clearly indicate that the planar‐shaped Pt II chromophore 10 2– stacked along the b axis with 3.309(1) Å between adjacent Pt II ions, thereby suggesting the effective Pt ··· Pt interaction in the column as shown in Figure 11 (a).…”

“… (a) Perspective view of the unit cell of 10 ‐Zn · 4H 2 O along the b axis. (b) Linear coordination polymeric structure of 10 ‐Zn · 4H 2 O. Reprinted with permission from the literature 38. Copyright 2010 The Royal Society of Chemistry.…”

“… Bright‐field images of 10 ‐Zn · 4H 2 O in air, soaked in water, CHCl 3 , and MeOH, respectively (top), and emission spectra of 10 ‐Zn · 4H 2 O soaked in various liquid media at room temperature (bottom); λ ex = 519 nm. Reprinted with permission from the literature 38. Copyright 2010 The Royal Society of Chemistry.…”

Vapour-adsorption and chromic behaviours of luminescent coordination polymers composed of a Pt(ii)-diimine metalloligand and alkaline-earth metal ions

“…In the case of ZnPt4H 2 O, the Zn 2+ ion in the structure acted as the water adsorption site and the coordination geometry of Zn 2+ ion changed by desorption of the all water 35 molecules from 5-coordinated trigonal-bipyramid to 4-coordinated tetrahedron accompanied by the change of coordination mode of the carboxyl group from the monodentate to bidentate fashion. 9 Because the four MPt4H 2 O CPs are thought to be isomorphous with ZnPt4H 2 O, the bridging 40 alkaline-earth metal ions should also act as the vapour-adsorption sites. All anhydrous MPt CPs can adsorb MeOH vapour in contrast to the lack of adsorption ability of ZnPt to MeOH vapour.…”

“…The thermochromic behaviours as well as the observed red shifts of 35 As mentioned in the Introduction, ZnPt can adsorb only water vapour. 9 The vapour adsorption isotherms of MPt were measured in order to evaluate the substitution effect of the bridging metal ions on the vapour-adsorption properties. Prior to these measurements, the samples were dried at 373 K under vacuum.…”