Molecular Modeling Calculations

Abstract

Photochromic molecules provide a unique opportunity for the practical application of theoretical chemistry, molecular modeling, and molecular simulation, since their molecular properties directly determine the function of devices. 1 Recent remarkable developments of computer hardware and software have opened a new horizon in material design, namely, the combination of computational studies and experimental approaches to offer an understanding of function on a molecular level. 2 This does well for the future design of functional materials.The requirements for the design of photochromic compounds are, among others, the adjustment of absorption wavelength and intensity, the attainment of thermal stability, clarification of reaction mechanism, and enhancement of quantum yield. The purpose of this chapter is to review recent computational studies in consideration of these requirements. ABSORPTION WAVELENGTH AND INTENSITYThe first event of the photochromic reaction is light absorption. Therefore, how efficiently the molecules of a photochromic compound absorb a given wavelength of light is the first concern. Practical applications often require the use of a limited range of wavelengths of the light source, and, as a result, molecules must be adjusted to the light source. We will include some work on organic functional dyes in this section, since most important studies are on organic dyes. The pioneering work reported in this area has used the Pariser-Parr-Pople

Rotational Isomerization of Dithienylethenes: A Study on the Mechanism Determining Quantum Yield of Cyclization Reaction

“…We have previously reported theoretical studies on the molecular design of dithienylethenes, focusing on thermal stability, absorption properties, and the analysis of the QY for the cycloreversion reaction . The present investigation is intended to provide a detailed description of the ground-state potential energy profile of the 1,2-bis(3-methyl-2-thienyl)perfluorocyclopentene (molecule 1 , Scheme ); the study takes into account its relation to the cyclization QY.…”

Comments on photochromism of 3-(3-pyridyl)sydnone and 4-alkenylsydnones

“…This contention stands unchallenged in the literature and continues to be cited. 8,9,10 We wish to point out that calculations at the TD-B3LYP/6-31+G** level indicate that nitrosaminoketenes should not have absorptions in the 600 nm range. 11 The longest wavelengthmaximum for the ketene 2a derived from 3-(3-pyridyl)sydnone is a very weak transition at 405 nm (f = 0.0007) in accord with the expectation that this compound, like other nitrosamines, should be yellow, not blue.…”

Synthesis, Photochromism and Optical Recording of a New Diarylethene

“…Organic photochromic molecules have raised considerable interest due to their potential applications to optical memory and molecular switches [1]. Among the various photochromic compound, diarylethene, whose general form is shown below, is one of the most promising organic photochromic molecules because of its high fatigue resistance [2].…”