Relating Excited States to the Dynamics of Macroscopic Strain in Photoresponsive Crystals

Abstract

Exposure of a photoreactive single crystal to light with a wavelength offset from its absorption maximum can have two distinct effects. The first is the “direct” effect, wherein the excited state generated in individual chemical species is influenced. The second is the “indirect” effect, which describes the penetration of light into the crystal and hence the spatial propagation and completeness of transformation. We illustrate using the nitro–nitrito isomerization of [Co­(NH3)5NO2]­Cl­(NO3) as an example that the direct and indirect effects can be independently determined. This is achieved by comparing the dynamics of macroscopic crystal deformation (bending curvature and crystal elongation) induced by the photochemical reaction when irradiating a crystal at the absorption maximum and at different band edges (above or below the maximum) of the same band. Quantitative description of the macroscopic strain dynamics in comparison with experiments allowed us to suggest that irradiation at different tails of the same absorption band causes isomerization to proceed via different excited states and an additional photochemical reaction (presumably, reverse nitrito–nitro isomerization) can occur on irradiation at the ligand-field band edges.

An optically reversible room-temperature solid-state cobalt(iii) photoswitch based on nitro-to-nitrito linkage isomerism

“…The most thoroughly investigated nitro cobalt complex undergoing the isomerization reaction upon UV-vis light irradiation is nitropentaaminecobalt(III). 30,31 Hence for this study, we have selected [Co(Me-dpt)(NO 2 ) 3 ] (Me-dpt = 3,3 0diamino-N-methylpropanediamine) (Fig. 1), 32 which constitutes a cobalt(III) analogue of the previously studied, and proved photoswitchable, nickel(II) complex.…”

Photothermally induced natural vibration for versatile and high-speed actuation of crystals

“…We have successfully simulated photothermal-induced natural vibration based on FEA as shown in Simulation I and II. In the past decade, a few models have been proposed to reproduce photomechanical bending of crystals through photoisomerisation-chemical reactions of molecules-based on rigorous mathematical equations 29,30 . The aim of these mathematical models is to understand the photoreaction of molecules in the crystalline state from the perspective of solid-state photochemistry.…”

Exploring Photoswitchable Properties of Two Nitro Nickel(II) Complexes with (N,N,O)-Donor Ligands and Their Copper(II) Analogues

“…Examples of ambidentate ligands known to display solid-state linkage isomerism include NO, , NO 2 , ,,− SO 2 , − SCN, and N 2. Transition-metal complexes containing nickel, ,,, cobalt, − iron, ruthenium, , osmium, palladium, or platinum − , centers are the most representative examples of such systems. Light-induced structural changes in crystals can be investigated using photocrystallographic methods. ,− As far as copper complexes are concerned, to date, no multi-temperature X-ray diffraction or photocrystallographic studies of the ONO isomerization reaction have been reported; however, mixtures of various linkage isomers were observed in the solid state. , …”