Molecules in Motion: From Sub‐Nanoscale to Macroscale

Abstract

Ruthenium polypyridine complexes comprising sulfoxide ligands show dramatic photochromic behavior based on phototriggered S→O and O→S isomerization. Quantum yields of isomerization can be large, indicating that the excited‐state bond‐breaking and bond‐making reactions are efficient. Ultrafast transient absorption spectroscopy reveals both adiabatic and non‐adiabatic isomerization mechanisms. Incorporation of these complexes within polymer matrices leads to macroscopic bending of the polymer in an example of a direct transduction of photonic energy to mechanical energy.

Unravelling the S → O Linkage Photoisomerization Mechanisms in cis- and trans-[Ru(bpy)2(DMSO)2]2+ Using Density Functional Theory

“…Among these compounds, those which feature significantly different absorption properties following their photoswitching are said to be photochromic. Such compounds have been used in molecular computing − (logic gates), in photomechanical or opto-mechanical materials − and for biological applications. , Phototriggered linkage isomerization reactions are of particular interest for photochromism because they can imply drastic changes in the electronic structure and consequently, dramatic changes in the absorption properties. − In this latter case, there has been a growing interest over the past decade in designing photochromic polypyridyl sulfoxide ruthenium complexes − since the report of a phototriggered S → O linkage isomerization in cis -[Ru(bpy) 2 (DMSO) 2 ] 2+ (where bpy = 2,2′-bipyridine and DMSO = dimethyl sulfoxide) . These complexes are particularly valuable for photochromism since they combine the well-known absorption properties of ruthenium polypyridyl complexes (low energy singlet metal-to-ligand charge transfer excitations) together with the linkage isomerization capability of the ambidentate sulfoxide ligands.…”

Generating Photonastic Work from Irradiated Dyes in Electrospun Nanofibrous Polymer Mats

“…This report specifically addresses the fate of heat generation in photonastic materials and demonstrates how heat can perform work following excitation of a nonisomerizing dye. We previously published results illustrating light-induced macroscopic bending in a co-polymer of norbornene that was ascribed to isomerization of a pendant photochromic ruthenium sulfoxide unit. − We noticed a nontrivial role for photothermal bending in that study. Since then, we have noted literature reports on photosoftening, etc., which appear to imply a significant role for a photothermal or photoinduced heating effect in macroscopic bending of polymer or crystalline materials. ,, Here, we preform the critical bilayer or bimorph structure for bending by creating nanofibrous mats from electrospinning techniques.…”

Calibrating Reaction Enthalpies: Use of Density Functional Theory and the Correlation Consistent Composite Approach in the Design of Photochromic Materials

“…Also, the bistability of these organometallic photochromes requires an adequate free energy of activation (Δ G ⧧ > ∼30 kcal mol –1 ) for rearrangement such that the complex will not thermally isomerize between chelates at room temperature. Hence, the ground-state bond dissociation enthalpy (BDE) required to cleave a metal–ligand bond is of particular interest to researchers to aid in the rational design of new organometallic photochromes. ,,− Our lab and others have used photoacoustic calorimetry (PAC) to study the BDEs of various ligands in transition-metal (TM) complexes. − ,,,− …”