Mechanistic Insights into Vapor-Induced Crystal Structural Changes of a Polymorphic Pt(II) Complex Involving Single...

Vapor-induced structural changes, coupled with modifications in electronic structure, have garnered significant attention owing to their potential application in sensor materials. However, the mechanisms driving the vapor-induced structural changes remain largely unexplored. Herein, we report mechanistic insights into the vapor-induced structural changes of a Pt(II) complex, [Pt(Cl₂BAn)(acac)] (=1; Cl₂BAn = 3-chlorobenzylidene-3-chloroaniline, acac = acetylacetonato), involving single crystal generation. A microcrystalline powder sample of 1 (1a) exhibited acetone vapor-induced structural changes to 1b (unsolvated polymorphs), accompanied by single crystal generation. Microscopic observations and solubility assessments revealed the process. Compound 1a was partially dissolved in the minimum required quantity of liquid acetone via the condensation of acetone vapor. Second, crystals of 1b were generated from the solution and subsequently grew owing to the lower solubility of 1b than 1a in acetone. The transformation ceased when nearly all 1a was consumed, leaving 1b single crystals with a minimal amount of liquid. 1a and 1b exhibit distinct vapor-condensation behaviors: thus, the reaction ceases when 1a is consumed. Consequently, achieving vapor-induced structural changes requires differences in solubilities and vapor condensation behavior between two polymorphs. These findings highlight one of the mechanisms for vapor-induced crystal structural changes and offer insights into tailoring vapor-response characteristics.