Assembling an alkyl rotor to access abrupt and reversible crystalline deformation of a cobalt(II) complex

Abstract

Harnessing molecular motion to reversibly control macroscopic properties, such as shape and size, is a fascinating and challenging subject in materials science. Here we design a crystalline cobalt(II) complex with an n-butyl group on its ligands, which exhibits a reversible crystal deformation at a structural phase transition temperature. In the low-temperature phase, the molecular motion of the n-butyl group freezes. On heating, the n-butyl group rotates ca. 100° around the C–C bond resulting in 6–7% expansion of the crystal size along the molecular packing direction. Importantly, crystal deformation is repeatedly observed without breaking the single-crystal state even though the shape change is considerable. Detailed structural analysis allows us to elucidate the underlying mechanism of this deformation. This work may mark a step towards converting the alkyl rotation to the macroscopic deformation in crystalline solids.

Self‐Healing Behavior in a Thermo‐Mechanically Responsive Cocrystal during a Reversible Phase Transition

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The molecular-level motions of ac oronene-based supramolecular rotator are amplified into macroscopic changes of crystals by co-assembly of coronene and TCNB (1,2,4,5-tetracyanobenzene) into ac harge-transfer complex. [5][6][7][8][9][10][11] [ + + ]T hese authors contributed equally to this work.Supportinginformation for this article can be found under: http://dx.

The crystallographic studies show that the global similarity of the packing patterns of both phases with local differences,s uch as molecular stacking sequence and orientations,should be the origin of the self-healing behavior of these crystals.…”

“…[1][2][3][4] Among the above phenomena, the generation of advanced materials with self-healing capabilities,reversibility, and controllable performance is very attractive.Agood starting point for achieving such agoal and understanding the structure-property relationship is to investigate easily-characterized molecular single crystals because the connection between molecular movements and macroscopic properties can be easily established by carefully analyzing sufficient crystallographic information such as packing patterns,molecular geometries,a nd key intermolecular interactions. [5][6][7][8][9][10][11] However,s uch research is very challenging because it requires that molecular single crystals should retain their macroscopic integrity during the exposure to external stimuli. Moreover,the crystallinity of amaterial positively correlates with its brittleness.T hus,c rystalline molecular crystals lack efficient self-healing effects,which have been observed in soft materials and polymers.…”

Anisotropic Thermal Expansion as the Source of Macroscopic and Molecular Scale Motion in Phosphorescent Amphidynamic Crystals

“…We and others have addressed it by exploring the emergent properties of amphidynamic crystals, which are built with a combination of lattice forming elements and moving parts . To date, examples have been reported of amphidynamic crystals with the potential of controlling gas adsorption and desorption, electric, optic, shape memory, and luminescence, among other properties …”

Self‐Healing Behavior in a Thermo‐Mechanically Responsive Cocrystal during a Reversible Phase Transition

“…Among the above phenomena, the generation of advanced materials with self‐healing capabilities, reversibility, and controllable performance is very attractive. A good starting point for achieving such a goal and understanding the structure–property relationship is to investigate easily‐characterized molecular single crystals because the connection between molecular movements and macroscopic properties can be easily established by carefully analyzing sufficient crystallographic information such as packing patterns, molecular geometries, and key intermolecular interactions . However, such research is very challenging because it requires that molecular single crystals should retain their macroscopic integrity during the exposure to external stimuli.…”