Electrochemical and Photochemical Cyclization and Cycloreversion of Diarylethenes and Diarylethene-Capped Sexithiophene Wires

Abstract

A combined theoretical and experimental study was performed on diarylethenes and diarylethene-capped sexithiophenes aiming at an improved understanding of the electrochemical and photochemical ring-opening and ring-closing mechanisms. Theoretical calculations, based on DFT and TDDFT, suggested that the spatial distribution and the occupancy of the frontier orbitals determine and control the diarylethenes’ ring-opening and ring-closing upon photoirradiation and electrochemical oxidation. Optimized geometries, potential energy surfaces, and activation energies between the open-ring and closed-ring forms were calculated for diarylethenes in the neutral ground state, excited states, and mono- and dicationic states. Analysis of the frontier orbitals was employed to understand the cyclization and cycloreversion of diarylethenes and to predict and explain the switching properties of diarylethene-capped sexithiophene molecular wires. The TDDFT data were verified with experimentally measured UV/vis spectra. The DFT calculations estimated open-shell ground states of diarylethene-capped sexithiophene dications, which were verified with EPR spectroscopy, and the broadening of the peaks in the EPR spectra were explained with the calculated singlet−triplet splitting. The good agreement of experiment and theory allows for the understanding of switching behavior of diarylethenes in solutions, in metal break junctions, in monolayers on metal surfaces, and as a part of complex organic molecular wires.

Light penetration-coupled photoisomerization modeling for photodeformation of diarylethene single crystal: upscaling isomerization to macroscopic deformation

“…2) with other first principle studies 11, 19, 30–32 strengthen its reliability, such as huge ground energy barrier, activation energy on first excited PES during ring-opening, barrierless first excited PES during ring-closing, and no-crossing between first and second excited PESs. These no-crossing PESs are also demonstrated in Figure S2 by equation of motion coupled-cluster singles and doubles (EOM-CCSD) method 33 which involves double excitation operator.…”

Theoretical investigation on remote-control photocycloreversion of dithienylethene driven by azobenzene chromophores

“…And the PEC of the first-excited state (S 1 ) and second-excited state (S 2 ) were calculated as vertical excitations for the ground-state geometries with TD-PBE0 method. Although the TD-DFT method is not the best choice for PEC simulation, many theoretical researchers [2,[34][35][36][37] also prefer to employ it, because in simulation of large molecules it costs low computing resource but can well describe the reaction process. Fig.…”

“…Photochromic dithienylethene (DTE) derivatives, which can undergo reversible photoisomerization by appropriate irradiation, have attracted more and more attention due to their wide applications in optical switches and memories, molecular machines, and nano-devices [1][2][3][4][5][6][7][8]. Usually the irradiation light on DTE must properly match the absorption band of its isomers, according to the Grotthuss-Draper law (also called the principle of photochemical activation), which states that only that light which is absorbed by a system can bring about a photochemical change [9].…”

Photoswitching of Conductance through Salicylidene Methylamine

“…25−29 Furthermore, the photoswitching and electrochemical switching mechanisms of diarylethenes were understood and unified on the basis of molecular orbital analysis. 28 Besides diarylethenes, molecular photoswitching devices were based on fulgide derivatives, spiro-oxazines, cis− trans isomerization of azobenzene, and stilbenes. The necessary condition for a molecular photochemical switch is that the molecule can exist in two stable ground state isomer forms with sufficient activation barrier between them to prevent the thermal isomerization.…”