Computational Methodology Study of the Optical and Thermochemical Properties of a Molecular Photoswitch

Abstract

We assess how the utilization of different DFT functionals for obtaining the equilibrium geometries and vibrational frequencies affect the description of the thermochemistry and subsequent calculation of the optical properties of a dihydroazulene-vinylheptafulvene photoswitch. The assessment covers nine popular DFT functionals (BLYP, B3LYP, CAM-B3LYP, M06-L, M06, M06-2X, PBE, PBE0, and ωB97X-D) in conjugation with five different Pople style basis sets (6-31+G(d), 6-31++G(d,p), 6-311+G(d), 6-311++G(d,p), and 6-311++G(3df,3pd)). It is identified that only CAM-B3LYP, M06-2X, and PBE0 are able to quantitatively describe the correct trends in the thermochemical properties. The subsequent calculation of the optical properties using the CAM-B3LYP functional shows that there is little difference in whether the CAM-B3LYP, M06-2X, or PBE0 functionals have been used to calculate the equilibrium geometries. Utilizing the identified functionals, we investigate how the number of electron withdrawing cyano substituents influence the thermochemistry and optical properties of the molecular photoswitch.

Towards Solar Energy Storage in the Photochromic Dihydroazulene–Vinylheptafulvene System

“…To shed further light on the thermochemical properties and kinetics of the TBR of the 3‐phenyl derivatives and hence the applicability for use as molecular heat batteries, a computational study was conducted and the results compared to energies recently calculated for the 1 / 2 and 3 / 4 pairs 5. The storage Gibbs free energies and storage enthalpies, defined as the relative energies between the lowest‐energy VHF and DHA conformations for DHAs 1 , 3 , 15 , and 16 , were calculated by using the CAM‐B3LYP, M06‐2X, and PBE0 functionals with the 6‐311+G(d) basis set in vacuum, cyclohexane (CH), and MeCN (see the Supporting Information).…”

“…have estimated an upper limit for the energy density of photochromic molecules of 1 MJ kg −1 , which would be useful for real applications. Recent calculations show that the Gibbs free energy difference of the parent DHA/VHF 1 / 2 is 27.7 kJ mol −1 in vacuum, at the M06‐2X/6‐311+G(d) level, which corresponds to a Gibbs free energy density of only 0.11 MJ kg −1 (energy stored in VHF) 5. The parent system is thus far from optimum.…”

Evaluating Dihydroazulene/Vinylheptafulvene Photoswitches for Solar Energy Storage Applications

“…Based on theory,future improvement can be focused on the enhancement of the energy storage capacity of the DHA/VHF couple (DH stor ), which is only 0.14 MJ kg À1 (calculated for neat compound), [16] but, by struc- tural modifications such as removingo ne of the two cyano groups [10b] or by fusing ab enzene ring to the DHA, [10f,g] can be increased 2-4 times. Moreover,t he [Cu(CH 3 CN) 4 ]PF 6 -catalyzed conversion of VHF into DHA was demonstrated in af low reactor.W ea lso tested the solar energy storagei nal aboratory-scale device, as well as, for the first time, under realistico utdoor conditions.…”

“…[10b,16] From the point of view of molecular stability, toluene, or as imilar nonpolar solvent, seems to be the most attractive choice for device testing, because of its long VHF half-life, high quantum yield, high solubility,a nd DH stor values were used in the estimation of the solar energy storagee fficiency h MOST [as determinedb yE quations (1)-(3); see below].…”

Characterisation of dihydroazulene and vinylheptafulvene derivatives using Raman spectroscopy: The CN-stretching region

“…The DFT functional CAM-B3LYP was used in combination with the Pople style basis set 6-311+G(d) for the optimisation of the geometries. Further inclusion of polarisation and diffuse functions on hydrogen has previously been shown to have negligible effect on energies and frequencies [33]. The 6-311+G(d) basis set was applied on all the substituents except iodine, which is not implemented in the basis set.…”