Low-energy optical switching of SO₂ linkage isomerisation in single crystals of a ruthenium-based coordination complex

Abstract

Single crystals that behave as optical switches are desirable for a wide range of applications, from optical sensors to read–write memory media.

Structural Capture of η1-OSO to η2-(OS)O Coordination Isomerism in a New Ruthenium-Based SO2-Linkage Photoisomer That Exhibits Single-Crystal Optical Actuation

“…While this photoconversion fraction is not unusual in the wider set of [RuSO 2 ] complexes, it contrasts markedly to the situation with its bromo and iodo analogues, which exhibit 100% photoconversion. 44 , 46 It should be noted that this particular comparison was not extended to the chloro analogue, as its photocrystallography results were produced using a different (white) light source, 38 cf. a 505 nm LED source was used to study the other 3-halopyridine-based complexes.…”

“…Only a small extent of arene rotation was observed in 1 within the tosylate anions that are engaged in nano-optomechanical transduction in the light-induced crystal structures of trans -3-halopyridine-based [RuSO 2 ] complexes. The SO 2 -linkage photoisomerization process caused this arene ring to rotate by 39(4), 68(3), and 77(3)° in the chloro, 38 bromo, 44 and iodo-based 46 complexes, respectively; in contrast, this rotation is too small to be quantified in the light-induced crystal structure of 1 ; it is observable by comparing the ADPs of the carbon atoms in this ring, especially C21, C22, C24, and C25, either between those of the dark-state and light-induced crystal structures or comparing these ADPs against those of the other anion in the light-induced crystal structure (i.e., C11, C12, C14, and C15). For example, the ADPs of carbon atoms in the nonrotor ring of 1 (anion 2) are pretty isotropic when viewed edge-on in its light-induced crystal structure ( Figure 1 , top right) while the carbon atoms in the rotor ring of 1 (anion 1) can be seen to be distinctly anisotropic along the direction of the crystallographic a axis, as shown in Figure 1 (bottom).…”

“…This finding 34 led to the subsequent discovery of several more [RuSO 2 ] complexes that display nano-optomechanical transduction, 39 , 40 , 43 − 46 including trans -[Ru(SO 2 )(NH 3 ) 4 (3-bromopyridine)]tosylate 2 and trans -[Ru(SO 2 )(NH 3 ) 4 (3-iodopyridine)]tosylate 2 . Both of these complexes were found to exhibit nano-optomechanical transduction with 100% η 1 -OSO photoisomer formation.…”

“…Both of these complexes were found to exhibit nano-optomechanical transduction with 100% η 1 -OSO photoisomer formation. 44 , 46 This 100% SO 2 photoconversion is important because it opens up real-world opportunities for these materials in solid-state device technologies, where clean photoswitching is a prerequisite for many photonic applications; only fractional SO 2 photoconversion levels have been realized in all other [RuSO 2 ] complexes, as well as many other linkage photoisomers in other types of compounds that have been reported to date.…”

Molecular engineering of single-crystal optical actuators

“…One possible material option is a series of compounds based on the generic formula, [Ru(SO2)(NH3)4X]Y, whose SO2 group manifests solid-state linkage photo-isomerization (X is the trans-ligand to SO2; Y is a counterion). This light-induced phenomenon causes these materials to act as photo-induced molecular switches [6][7][8][9][10][11][12] or molecular transducers [13][14][15][16][17]. This talk will present the development of this family of materials towards such applications, via a range of advanced in situ light-induced x-ray diffraction (now known as photo-crystallography) [18][19][20] and in-situ light-induced single-crystal optical absorption spectroscopy microscopy experiments [11] that capture the phenomenon in their light-induced state [13][14][15].…”