The influence of nanoparticles on the excitation energies of the photochromic dihydroazulene/vinylheptafulvene system.

This paper studies how nanoparticles affect photochromic systems, focusing on the influence of gold nanoparticles on the optical properties of the dihydroazulene/vinylheptafulvene (DHA/VHF) system. This investigation is done using a combined quantum mechanical/molecular mechanical approach treating the photochromic system quantum mechanically. The gold nanoparticle is described as gold atoms with atomic polarizabilities using molecular mechanics, thus leaving out excitations of the gold nanoparticle.

The influence of nanoparticles on the polarizabilities and hyperpolarizabilities of photochromic molecules.

We consider how nanoparticles affect molecular photoswitches and our focus is on how the polarizabilities and hyperpolarizabilities of the dihydroazulene/vinylheptafulvene system changes, when the compounds interact with gold nanoparticles. We have utilized a combined quantum mechanical/molecular mechanical approach, where the photochromic molecule is described by time-dependent density functional theory using the long-range-corrected CAM-B3LYP functional and the correlation consistent aug-cc-pVDZ basis-set. The nanoparticles are described by gold atoms having an atomic polarizability.

Density Functional Theory Study of the Solvent Effects on Systematically Substituted Dihydroazulene/Vinylheptafulvene Systems: Improving the Capability of Molecular Energy Storage.

Former work has improved the energy storage capacity of the dihydroazulene/vinylheptafulvene photo/thermoswitch by substitution with NH and NO in vacuum. This work extends the former by investigating the solvent effects systematically using cyclohexane, toluene, dichloromethane, ethanol, and acetonitrile and comparing them with the inclusion of vacuum calculations. The investigation includes more than 8000 calculations using density functional theory for comparison of energy storage capacities, activation energies for the thermal conversion of vinylheptafulvene to dihydroazulene, and UV-Vis absorption spectra.

Theoretical Investigation of Substituent Effects on the Dihydroazulene/Vinylheptafulvene Photoswitch: Increasing the Energy Storage Capacity.

We have investigated the effects of substituents on the properties of the dihydroazulene/vinylheptafulvene photoswitch. The focus is on the changes of the thermochemical properties by placing electron withdrawing and donating groups on the monocyano and dicyano structures of the parent dihydroazulene and vinylheptafulvene compounds. We wish to increase the energy storage capacity, that is, the energy difference between the dihydroazulene and vinylheptafulvene isomers, of the photoswitch by computational molecular design and have performed over 9000 electronic structure calculations using density functional theory.

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

The effect of adding electron donating and withdrawing groups on the dihydroazulene (DHA)/vinylheptafulvene (VHF) photochromic system has been investigated using Raman spectroscopy in CS2 solutions. The photoswitching between DHA and VHF is often characterised with UV-Vis spectroscopy. However, Raman spectroscopy can also be used for this purpose and give structural insight, as the light induced ring-opening from DHA to VHF causes changes in the CN-stretching frequencies.

Computational methodology study of the optical and thermochemical properties of a molecular photoswitch.

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.