Quantifying Crystallographically Independent Optical Switching Dynamics in Ru SO₂ Photoisomers via Lock-and-Key Crystalline Environment

Abstract

The photophysical properties associated with solid-state Ru-based SO 2 linkage photoisomerism are shown to differ with single-molecule recognition; this stands to afford superior optical resolution for data storage applications. Two compounds, [Ru(NH 3 ) 4 SO 2 X]tosylate 2 (X = isonicotinamide (1) and isonicotinic acid (2)), yield crystal structures, each with two chemically identical but crystallographically distinct Ru-based complexes (Ru01 and Ru02) and thus two different photoisomerizable SO 2 environments. It was found that the SO 2 photoconversion fraction in each crystallographically independent complex differed by over 20% (for 1: 51.0(12) % in Ru01 and 28.6(9) % in Ru02). These photophysical differences between neighboring molecules were attributed to the larger free volume around the groundstate SO 2 in Ru01, allowing for higher photoconversion, i.e., a "lock-and-key" environment controls the photochemistry. Furthermore, the η 2 -side-S,O-bound (MS2) metastable photoisomer in Ru01 was 20 K more thermally stable in both 1 and 2; photoinduced intermolecular interactions are shown to dictate this thermal stability.

Rationalizing the photophysical properties of BODIPY laser dyes via aromaticity and electron-donor-based structural perturbations

“…4), one of these chains exhibits antiperiplanar relationships between all CeC bonds while the other presents a twisted conformation, brought about by the gauche relationship between C18-C19 and C20-C21 (C18-C19-C20-C21 ¼ 65.9(2) ); however, both n-butyl chains in 4 b adopt the linear conformation. The presence of these different molecular conformations in the crystal structures of 3 and 4 will likely affect their photophysical properties [45,46]. As such, this structural variation is an important consideration when discerning the lowest energy conformer for use in quantum-chemical calculations.…”

“…state conformation on optical properties [45,46]. Our future work will focus on quantifying the effect of the varying levels of planarity of the chromophores in the crystal structures of these BODIPY dyes by measuring the absorption and fluorescence in the solid state.…”

Understanding solid-state photoswitching in [Re(OMe2-bpy)(CO)3(η1-NO2)] crystals via in situ photocrystallography

“…19 Among the earliest systems to be studied are solid state linkage isomers, in which a long lived, metastable photoexcited isomer is produced at low temperature. 20 Building on seminal work by Coppens on metal-nitrosyl compounds, 21 a variety of linkage isomer systems have been studied including nitrosyl, [22][23][24][25] sulfur dioxide, [26][27][28][29] dinitrogen 30 and nitrite species. 20,[31][32][33][34][35][36][37][38] In particular, nitro → nitrito isomerism is well studied by photocrystallographic methods, with the first 100% conversion in a single crystal reported in 2009 for [NiIJdppe)IJCl)IJη 1 -NO 2 )].…”

Solid-state photochemistry of molecular photo-switchable species: the role of photocrystallographic techniques

“…The compounds [Ru(NH 3 ) 4 (SO 2 )X](tosylate) 2 , where X is either isonicotinamide or isonicotinic acid, are found to crystallize with two chemically identical, though crystallographically distinct, molecules in the asymmetric unit, which are shown to undergo different levels of photoconversion on activation. The difference in their photoisomerism behaviour is attributed to changes in intermolecular contacts between the two different crystalline environments, highlighting the important influence that steric interactions can have on the progress of a solidstate photoreaction (Sylvester & Cole, 2013b). Most recently, a transduction effect induced by sulfur dioxide isomerism has been reported to cause rotational movement further along the molecule, which it is suggested could behave as a molecular machine (Sylvester & Cole, 2013a).…”