Between red and yellow: evidence of intermediates in a vapochromic Pt(ii) salt

Abstract
[Pt(tpy)Cl]ClO4·H2O (1·H2O) changes from red to yellow upon dehydration due to increased PtPt distances. Spectroscopic, diffraction, gravimetric and calorimetric data demonstrate the presence of intermediates during hydration and dehydration which signifies surprising mechanistic complexity in the vapochromic response.