Direct synthesis and crystal structure of dehydrated state in vapochromic MMX-type quasi-one-dimensional iodide-bridged platinum complexes

The dehydrated vapochromic 1D coordination polymer, (H ₃NC ₄H ₈NH ₃) ₂[Pt ₂(pop) ₄I] (1) was synthesized directly from methanol solution. Although vapochromic 1·4H ₂ O has been synthesized, dehydrated high-temperature structure has never been determined because of lowering the quality of crystal by dehydration. The crystal structure of 1 was determined by X-ray crystal structure analysis, and we confirmed that it was identical to the dehydrated high-temperature structure of 1·4H ₂ O by comparing the powder X-ray diffraction (XRD) patterns. The Pt-I-Pt distance (d(Pt-I-Pt)) of compound 1·4H ₂ O was shortened for approximately 1.1 Å by desorption of water to form compound 1, accompanied with phase transition in electronic states. The other crystal including methanol molecule as lattice solvent, 1·2MeOH, was also obtained as by-product. The synthesis from various kinds of organic solvent has the great potential to develop the field of vapochromism accompanying phase transition of electronic state.