Vapour‐Induced Amorphous–Crystalline Transformation of a Luminescent Platinum(II)–Diimine Complex

Abstract

AbstractA novel luminescent platinum(II)–diimine complex, Na2[Pt(CN)2(dcbpy)]·nH2O (H2dcbpy = 4,4′‐dicarboxy‐2,2′‐bipyridine, n = 2 or 5) was synthesized and investigated by using X‐ray diffraction measurements and spectroscopy. Complex Na2[Pt(CN)2(dcbpy)]·2H2O was first obtained as a red amorphous solid (1A) that exhibits bright luminescence at 623 nm. After recrystallization, two crystalline forms, the dihydrate form, 1C, and the pentahydrate form, Na2[Pt(CN)2(dcbpy)]·5H2O (2), were obtained and analyzed by the single‐crystal X‐ray diffraction method. Upon exposure of the amorphous form 1A to hydrophilic vapours such as those of MeOH and acetone, 1A irreversibly changed to a yellow crystalline solid 1C that showed luminescence at 608 nm with a shoulder at 568 nm. This vapour‐induced amorphous–crystalline transformation has never been observed either by exposing 1A to hydrophobic vapours nor by increasing the temperature up to 410 K. IR spectroscopy revealed that the amorphous–crystalline transformation did not involve the adsorption of the vapour. This phenomenon of irreversible structural transformation accompanied by change of luminescence is possibly applicable to vapour history sensors.