Solvent vapour-responsive structural transformations in molecular crystals composed of a luminescent mononuclear aluminium(iii) complex

Abstract

Investigations into the construction of functional molecular crystals and their external stimuli-induced structural transformations represent compelling research topics, particularly for the advancement of sensors and memory devices. However, reports on the development of molecular crystals constructed from discrete mononuclear complex units and exhibiting structural transformations via the adsorption/desorption of guest molecules are scarce. In this study, we synthesised three molecular crystals composed of [Al(sap)(acac)(H₂O)]·(solvent) (H₂sap = 2-salicylideneaminophenol, acac = acetylacetonate, solvent = Me₂CO (Al·Me₂CO), MeCN (Al·MeCN), or DMSO (Al·DMSO)), and demonstrated solvent vapour-responsive reversible crystal-to-crystal structural transformations in Al·Me₂CO and Al·MeCN. For Al·DMSO, exposure to DMSO vapour led to the formation of DMSO-coordinated compound [Al(sap)(acac)(DMSO)], indicating an irreversible structural transformation. This solvent vapour-responsive system incorporates a luminescent mononuclear aluminium(III) complex (λ_max = 539–552 nm, Φ_em = 0.07–0.27) as the molecular building unit for the porous-like framework. Therefore, we synthesised a new functional molecular material and a potential molecular building unit that facilitates guest fixation through hydrogen-bonding.