(9-Isocyanoanthracene)gold(I) Complexes Exhibiting Two Modes of Crystal Jumps by Different Structure Change Mechanisms

Abstract

The first examples of single crystals exhibiting salient effects by different structure change mechanisms are reported. The crystals of newly prepared aryl­(9-isocyanoanthracene)­gold­(I) complexes jump in response to two different external stimuli: ultraviolet (UV) irradiation and cooling. The photosalient effect is triggered by photodimerization reaction of the anthracene moieties under photoirradiation. By contrast, the thermosalient effect is caused by anisotropic thermal contraction upon cooling without a chemical structure change. By taking advantage of the multiple-jump feature, we also show sequential jumps of crystals by cooling and then UV irradiation for demonstration of the programmed motion of molecular crystals.

Crystal actuation switching by crystal thickness and light wavelength

“…1,[6][7][8][9][10][11] Compared with polymers, molecular crystals are more advantageous in light-driven actuators and soft robots because of their higher elastic modulus and stronger output force. 9 Thus far, various light-fuelled (i.e., photomechanical) crystals that exhibit bending, [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] twisting, 23,29,30 bending with twisting, 31,32 curling, 33 rotation, 34,35 peeling, 36,37 and jumping 38,39 have been developed; these characteristics are mainly based on the photoisomerisation (sometimes photodimerisation) of molecules. Recently, we reported rapid bending of molecular crystals through the photothermal effect, in which thermal energy is produced by photoexcitation of a material; 40 we unveiled that the bending mechanism was driven by a non-steady temperature gradient in the thickness direction.…”

Photomechanical crystalline materials: new developments, property tuning and applications

“…Very recent progress from Ito's group discovered a multistimuli-responsive mode of (9-isocyanoanthracene)gold( i ) complexes. 147 The crystals jump in response to irradiation and cooling, which is attributed to different response mechanisms. The photosalient effect is triggered by the [4 + 4] photocycloaddition of the anthracene moieties in the crystal, and the thermosalient effect is caused by anisotropic thermal contraction (Fig.…”

Thermosalience coupled to abrupt spin crossover with dynamic ligand motion in an iron(ii) molecular crystal

“…25 As a very rare case, some crystals show salient effects by two different stimuli. [25][26][27] Since the first observation of such fascinating crystal motion in the thermally hopping Pd organometallic compound by Etter and Siedle in 1983, 28 and thorough studies of the Pd crystal 13 and other TS crystals 12 by Naumov and his co-workers in the early 2010s, reports of new TS crystals have increased and the understanding of TS properties has deepened in the last decade. 15,18,20,21 However, exhibiting TS effects at desired temperatures with sufficient reproducibility for material application is still a very challenging issue.…”

“…9 For example, recently reported crystals of 1-naphthyl(9-isocyanoanthracene)gold( i ) show jumping upon cooling with a slight and anisotropic lattice dimension change and a small change in the unit cell volume [Δ a = +0.003 Å (+0.0%); Δ b = −0.058 Å (−0.5%); Δ c = −0.210 Å (−1.5%); Δ V = −36.17 Å 3 (−1.9%); +20 °C → −140 °C] and without a space group transformation ( P 2 1 / n ). 27 The above-mentioned general crystallographic features imply a probable disadvantage of the existence of flexible and movable molecules as lattice components for exhibiting TS effects.…”