• Dutta, Basudeb
• Khan, Samim
• Guerin, Sarah
• Naaz, Sanobar
• Mir, Mohammad Hedayetullah
• Cazade, Pierre-Andre
• Kiely, Emma

Abstract

<jats:title>Abstract</jats:title><jats:p>Dynamic photoactuating crystals have become a sensation due to their potential applications in developing smart medical devices, molecular machines, artificial muscles, flexible electronics actuators, probes and microrobots. Here we report the synthesis of two iso-structural metal-organic crystals, [Zn(4-ohbz)<jats:sub>2</jats:sub>(4-nvp)<jats:sub>2</jats:sub>] (<jats:bold>1</jats:bold>) and [Cd(4-ohbz)<jats:sub>2</jats:sub>(4-nvp)<jats:sub>2</jats:sub>] (<jats:bold>2</jats:bold>) {H4-ohbz = 4-hydroxy benzoic acid; 4-nvp = 4-(1-naphthylvinyl)pyridine} which undergo topochemical [2 + 2] cycloaddition under UV irradiation as well as sunlight to generate a dimerized product of discrete metal-complex [Zn(4-ohbz)<jats:sub>2</jats:sub>(<jats:italic>rctt</jats:italic>-4-pncb)] {<jats:italic>rctt</jats:italic>-4-pncb = 1,3-bis(4′-pyridyl)-2,4-bis(naphthyl)cyclobutane} (<jats:bold>1′</jats:bold>) and one-dimensional coordination polymer (1D CP) [Cd(4-ohbz)<jats:sub>2</jats:sub>(<jats:italic>rctt</jats:italic>-4-pncb)] (<jats:bold>2′</jats:bold>) respectively, in a single-crystal-to-single-crystal (SCSC) process. The Zn-based compound demonstrates photosalient behaviour, wherein crystals show jumping, splitting, rolling, and swelling upon UV irradiation. However, the Cd-based crystals do not show such behaviour maintaining the initial supramolecular packing and space group. Thus the photomechanical behaviour can be induced by choosing a suitable metal ion. The above findings are thoroughly validated by quantitative density functional theory (DFT) calculations which show that the Zn-based crystal shifts towards an orthorhombic structure to resolve the anisotropic UV-induced mechanical strain. Furthermore, the mechano-structure-property relationship has been established by complimentary nanoindentation measurements, which are in-line with the DFT-predicted single crystal values.</jats:p>

Topics

• density
• compound
• polymer
• single crystal
• theory
• anisotropic
• nanoindentation
• density functional theory
• one-dimensional
• space group