Stepwise stress-induced transformations of metal-organic polyhedral cluster-based assemblies: Where conformational and supramolecular features meet.

Abstract

The understanding of factors governing the formation of supramolecular structures and phase transitions between various forms of molecular crystals is pivotal for developing dynamic, stimuli-responsive materials and polymorph-controlled syntheses. Here, we investigate the pressure-induced dynamic of both the intrinsic molecular structure and the supramolecular network of a predesigned polyhedral oxo-centered zinc cluster incorporating monoanionic N,N -diphenylformamidinate and featuring the N-bonded phenyl groups in close proximity of the primary coordination sphere. We demonstrate that the model oxo cluster is prone to undergo pressure-induced conformational transformations of the secondary coordination sphere and simultaneous stepwise (initially every second polyhedral molecule undergoes the conformational transformations) and reversible transitions from an ambient phase α to high-pressure phases β and γ, as single crystal-to-single crystal events. The observed phase transitions nicely illustrate the key role of an interplay between low-energy conformational perturbations and cooperative intra- and intermolecular noncovalent interactions.