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

Hansen, Anne S.; Mackeprang, Kasper; Broman, Søren Lindbæk; Hansen, Mia Harring; Gertsen, Anders S.; Kildgaard, Jens Vive; Nielsen, O. Faurskov; Mikkelsen, Kurt V.; Nielsen, Mogens Brøndsted; Kjaergaard, Henrik G.

doi:10.1016/j.saa.2016.02.017

Cited by 3 publications

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References 41 publications

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“…The photoswitching of DHA/VHF systems can be monitored using different spectroscopies with UV–vis being the most common. ,,, From the calculated UV–vis absorption spectra (MeCN in Figure , vacuum, CH, toluene, and H 2 O in Figures S11–S14), trends similar to those of the individual DHA/VHF and DTE/DHB chromophores are observed (cf. Figure S15), ,, but obviously the absorbance is red-shifted compared to the individual chromophores due to the enlargement of the π-system in the combined switch.…”

Section: Resultsmentioning

confidence: 99%

A DFT Study of Multimode Switching in a Combined DHA/VHF-DTE/DHB System for Use in Solar Heat Batteries

et al. 2016

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Development of photochromic molecules for solar energy storage has two major challenges: (i) to store a sufficient amount of energy in the metastable isomer and (ii) to control the energy-releasing step, i.e., setting it on hold until the energy is needed. Combining the dihydroazulene/vinylheptafulvene (DHA/VHF) photo-/thermoswitch with the dithienylethene/dihydrothienobenzothiophene (DTE/DHB) photoswitch could potentially meet these challenges. The combined multimode switch is studied by density functional theory in order to predict its energy storage properties and spectral behavior in various solvents before discussing its suitability for use in solar heat batteries. An energy storage capacity of 0.17 MJ/kg is calculated which corresponds to a specific energy of 46 Wh/kgslightly larger than that of a common lead–acid car battery (∼40 Wh/kg) but still only one-fourth of lithium-ion batteries (100–250 Wh/kg). The usual trend for 1,8a-dihydroazulene-1,1-dicarbonitrile and its derivatives is for their energy storage capacities to decrease dramatically as the solvent polarity is increased, but it is found that solvent effects are not as significant for the combined DHA–DTE system. Furthermore, the spectral data indeed imply a possibility of controlling the back-reaction from the energy-rich metastable isomer by light stimulus, thus enabling one to release the stored energy upon request. This work thereby represents important progress toward efficient long-time solar energy storage in photochromic closed-cycle molecular systems.

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Section: Resultsmentioning

confidence: 99%

A DFT Study of Multimode Switching in a Combined DHA/VHF-DTE/DHB System for Use in Solar Heat Batteries

et al. 2016

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“…18 It was shown that when azobenzene and DHA molecules are packed on Au{111} surface and compared for their conversion efficiencies under identical conditions, azobenzene molecules yielded an order of magnitude lower conversion efficiency compared to DHA molecules. 19 A number of experimental 14,15,[20][21][22][23] and computational 13,[24][25][26] efforts have focused on tuning the switching properties of DHA/s-trans-VHF system with the attachment of functional groups. Although the absorption properties of both of the isomers, the reverse activation energies of the metastable isomers and the photoswitching fatigue resistances have been studied experimentally, to our knowledge, there has been no effort to quantify their ∆H using experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

“…A number of experimental ,,− and computational ,− efforts have focused on tuning the switching properties of the DHA/ s-trans -VHF system with the attachment of functional groups. Although the absorption properties of both of the isomers, the reverse activation energies of the metastable isomers, and the photoswitching fatigue resistances have been studied experimentally, to our knowledge, there has been no effort to quantify their Δ H using experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

Accurate Isomerization Enthalpy and Investigation of the Errors in Density Functional Theory for Dihydroazulene/Vinylheptafulvene Photochromism Using Diffusion Monte Carlo

Saritas

Grossman

2017

J. Phys. Chem. C

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We investigate the isomerization enthalpy of the Dihydroazulene/Vinylheptafulvene (DHA/VHF) molecular photoswitch system derivatives using electronic structure calculation methods including Density Functional Theory (DFT), Quantum Monte Carlo (QMC) and Coupled Cluster (CCSD(T)). Recent efforts have focused on tuning the isomerization enthalpy of the photoswitch for solar thermal energy storage applications using substitutional functional groups on its five and seven membered carbon rings, predominantly using DFT for the energy predictions. However, using the higher accuracy QMC and CCSD(T) methods, we show that in many cases DFT incorrectly predicts the isomerization enthalpy and the errors depends on the functional groups substituted and the choice of the DFT functional. Isomerization of the DHA to VHF molecule is a ring-opening reaction on the five membered ring of the DHA isomer. We find that the DFT errors are correlated to the ring-opening reactions of cyclobutene and cyclo-1,3-hexadiene, such that the DFT error changes monotonically with the size of the carbon ring, although QMC and CCSD(T) results are in a good agreement irrespective of the ring size. Using the QMC and CCSD(T) isomerization enthalpies, we predict gravimetric energy densities of the DHA derivatives for solar thermal storage applications. Our results show that suitable substitutions on DHA can yield gravimentric storage densities as large as 732 kJ/kg. 1

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Simulation framework for screening of molecular solar thermal systems in the context of a hybrid device

2019

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

Cited by 3 publications

References 41 publications

A DFT Study of Multimode Switching in a Combined DHA/VHF-DTE/DHB System for Use in Solar Heat Batteries

A DFT Study of Multimode Switching in a Combined DHA/VHF-DTE/DHB System for Use in Solar Heat Batteries

Accurate Isomerization Enthalpy and Investigation of the Errors in Density Functional Theory for Dihydroazulene/Vinylheptafulvene Photochromism Using Diffusion Monte Carlo

Simulation framework for screening of molecular solar thermal systems in the context of a hybrid device

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