Photoswitching Materials

Abstract

Photoswitchable materials are mainly engineered from molecules that are capable of undergoing reversible changes in their intrinsic properties through the use of light as an external stimulus. As the absorption properties of most of these molecules change reversibly with photoexcitation, most of them are also photochromic materials. Many of these photoswitching processes operate through reversible chemical transformations, such as trans‐cis isomerization, ionization, pericyclic ring‐opening and ring‐closing reaction, and intramolecular group transfer reaction. Through systematic investigations and subsequent rational designs on the photochromic frameworks using the state‐of‐the‐art organic synthetic methodologies, the photochromic properties could be modified, tuned, and tailored for molecular switching. In this chapter, different photochromic families and selected recent works dealing with the functionalization of different families of photochromic molecules for the photoswitching of luminescent behavior, electronic communication, optical properties, molecular shuttling, and host‐guest interaction are described.

Predicting Site-Binding Modes of Ions and Water to Nucleic Acids Using Molecular Solvation Theory

“…In order to gain predictive insight into GQs, we sought to develop a 3D-RISM model with tuned nonbonded force field parameters that were specifically calibrated to reproduce Na + and K + structure and thermodynamic binding properties in complexes with bis-crown-ethers and then validated against macromolecular ion channels. Bis-crown-ethers contain two sandwiched crown-ether rings, similar to the oxygen rims composing the coordination sphere of cations in GQs (vide infra), and prefer to bind metal ions with sizes slightly larger than their cavity, as opposed to 1:1 complexes between crown ethers and cations, whose formation is favored by size matching. − For Na + we consider the bis - (12-crown-4)-sodium complex, whereas for K + we use the bis - (15-crown-5)-potassium complex, which has been reported to be selective for the corresponding cations and for which high-resolution crystal structures exist with the cations at full occupancy (see Methods). Using the preorganized crystal structures of the complexes of the bis-crown-ether scaffolds, we adjusted the pairwise Lennard-Jones (LJ) parameters based on three criteria: (i) maximize cation occupancy within the binding locus between the two crown-ether units, (ii) minimize the deviation from the experimental cation location in the complex, and (iii) maintain a unimodal binding mode as observed experimentally.…”

Synthesis, Rotational Dynamics, and Photophysical Characterization of a Crystalline Linearly Conjugated Phenyleneethynylene Molecular Dirotor

“…Recent advances in the fields of functional materials and artificial molecular machines have led to the development of crystalline molecular machinery, which is intended to take advantage of internal molecular motion, and/or chemical reactivity, to influence mechanical properties, electric, magnetic, and/or optical functions in a highly controlled and anisotropic manner. Over the past few years, our group has emulated the structures of macroscopic gyroscopes, as they are useful models for the design of molecules capable of forming amphidynamic crystals with static elements and rapidly moving parts .…”