Extraordinary anisotropic thermal expansion in photosalient crystals

Abstract

Although a plethora of metal complexes have been characterized, those having multifunctional properties are very rare. This article reports three isotypical complexes, namely [Cu(benzoate)L 2], where L = 4-styrylpyridine (4spy) (1), 2′-fluoro-4-styrylpyridine (2F-4spy) (2) and 3′-fluoro-4-styrylpyridine (3F-4spy) (3), which show photosalient behavior (photoinduced crystal mobility) while they undergo [2+2] cycloaddition. These crystals also exhibit anisotropic thermal expansion when heated from room temperature to 200°C. The overall thermal expansion of the crystals is impressive, with the largest volumetric thermal expansion coefficients for 1, 2 and 3 of 241.8, 233.1 and 285.7 × 10−6 K−1, respectively, values that are comparable to only a handful of other reported materials known to undergo colossal thermal expansion. As a result of the expansion, their single crystals occasionally move by rolling. Altogether, these materials exhibit unusual and hitherto untapped solid-state properties.

Thermal expansion properties of organic crystals: a CSD study

“…The anisotropy of the thermal expansion could thus be considered as rare and large if -1<IAC<-0.46 or 0.34<IAC<1.00 and very rare and extraordinary large when -1<IAC<-0.86 or 0.74<IAC<1.00. In this light the extraordinary anisotropic thermal expansions recently reported for three photosalient crystals 57 with IACs of 0.248, 0.342, and -0.06, respectively, are rather normal. The three compounds are, however, metal-organic complexes whose structures could have a different IAC distribution.…”

Synthesis, characterization and thermal behaviour of solid phases in the quasi-ternary system Mg(SCN)2–H2O–THF

“…53 The research of ligand disorder and its impact on the parent material's chemistry or properties is very established in extended systems, such as metal-organic frameworks (MOFs), 54 but much rarer in crystalline solids with molecular coordination units. Like other coordination polymers, 55 Mg(SCN)2 • 2 THF exhibits a negative thermal expansion along the chains and a strong positive thermal expansion perpendicular to the chain axis.…”

Regioisomers of singly bridged calix[6]crown-6 and their heavy alkali metal complexes: a molecular baseball glove for caesium(I)

“…Since the pioneering works of Pedersen, Lehn and Cram, supramolecular chemistry of macrocycles is still significant in chemistry and biology because many of the roots and concepts came from the phenomena found in biological process such as molecular recognition, self-assembly, enzyme catalysis and ion transport (Pedersen, 1967;Izatt et al, 1995;Lindoy, 1990;Lehn, 1995). Supramolecular chemistry has been extended to various research areas such as metal-organic frameworks, metal-organic coordination cages, hydrogen-bonded organic frameworks, covalent organic frameworks,stacked frameworks, as well as applications of macrocyclic complexes and continuous studies being carried out (Zhou et al, 2012;Fujita et al, 2005;Cook et al, 2013;Chakraborty et al, 2021;Deng et al, 2020;Ouyang et al, 2017Ouyang et al, , 2018Li et al, 2014Li et al, , 2021Park et al, 2020;Britton et al, 2021;Boer et al, 2019;Braunecker et al, 2018;Hong et al, 2021;Yadava et al, 2020). The advances of experimental instruments for structural analyses including single-crystal X-ray diffraction and high-field NMR have also led such progress.…”