Ionic Crystals of {[Ni(phen)₃]₂Ge₄S₁₀}·xSol, Showing Solid-State Solvatochromism and Rapid Solvent-Induced Recrystallization

Thiogermanates, {[Ni­(phen)₃]₂Ge₄S₁₀}·xSol (Sol = 4MeOH·12H₂O (1) and 24H₂O (2)) were prepared and characterized by single-crystal structure analysis. There are large quantities of the solvent molecules that cocrystallize with the anions and cations and form a strong hydrogen bonding network (O–H···S and O···H–O–H···O). Reversible yellow-pink color change with fast speed was found for these compounds, when the crystals were immersed in alcohol solvents and water alternately. The time of the solvent-induced color change relates to the molecular size and structure of the alcohols. The smaller the molecule is, the faster the color change will be. The fastest color change was found by using the methanol solvent that took only about one second. The color change also relates to the ratio of water/alcohol. The solvatochromism phenomenon is accompanied with a rapid solvent-induced recrystallization that is verified by the XRD patterns.