A high enthalpy value in thermal isomerization of photosynthesized cis-9-styrylacridines

Caia, Vincenzo; Cum, G.; Gallo, Raffaele; Mancini, Vittorio; Pitoni, E.

doi:10.1016/s0040-4039(00)94308-9

Cited by 23 publications

(9 citation statements)

References 5 publications

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“…In these so-called molecular solar thermal (MOST) systems, the exposure of a low energy isomer to sunlight leads to its conversion into a high energy isomer. , The metastable high-energy isomer can be converted back to its low energy counterpart by heating or catalytic activation to release the stored energy. Several molecular and metal–organic systems have been explored in this context, notably stilbenes, , azobenzenes, − anthracenes, ruthenium fulvalene compounds, ,− and norbornadiene-quadricyclane (N-Q) systems. − Both experimental and theoretical aspects of this research field have been reviewed recently. ,,, …”

Section: Introductionmentioning

confidence: 99%

Comparative Ab-Initio Study of Substituted Norbornadiene-Quadricyclane Compounds for Solar Thermal Storage

et al. 2016

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Molecular photoswitches that are capable of storing solar energy, so-called molecular solar thermal storage systems, are interesting candidates for future renewable energy applications. In this context, substituted norbornadiene-quadricyclane systems have received renewed interest due to recent advances in their synthesis. The optical, thermodynamic, and kinetic properties of these systems can vary dramatically depending on the chosen substituents. The molecular design of optimal compounds therefore requires a detailed understanding of the effect of individual substituents as well as their interplay. Here, we model absorption spectra, potential energy storage, and thermal barriers for back-conversion of several substituted systems using both single-reference (density functional theory using PBE, B3LYP, CAM-B3LYP, M06, M06-2x, and M06-L functionals as well as MP2 calculations) and multireference methods (complete active space techniques). Already the diaryl substituted compound displays a strong red-shift compared to the unsubstituted system, which is shown to result from the extension of the conjugated π-system upon substitution. Using specific donor/acceptor groups gives rise to a further albeit relatively smaller red-shift. The calculated storage energy is found to be rather insensitive to the specific substituents, although solvent effects are likely to be important and require further study. The barrier for thermal back-conversion exhibits strong multireference character and as a result is noticeably correlated with the red-shift. Two possible reaction paths for the thermal back-conversion of diaryl substituted quadricyclane are identified and it is shown that among the compounds considered the path via the acceptor side is systematically favored. Finally, the present study establishes the basis for high-throughput screening of norbornadiene-quadricyclane compounds as it provides guidelines for the level of accuracy that can be expected for key properties from several different techniques.

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Section: Introductionmentioning

confidence: 99%

Comparative Ab-Initio Study of Substituted Norbornadiene-Quadricyclane Compounds for Solar Thermal Storage

et al. 2016

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“…In these materials, photon absorption converts a low‐ into a high‐energy isomer, where the back‐conversion is kinetically hindered but can be induced by a catalytic reaction or heating. Examples for these systems include stilbenes, azobenzenes, anthracenes, ruthenium fulvalene compounds, dihydroazulenevinylheptafulvene as well as norbornadiene–quadricyclane (N–Q) systems …”

Section: Introductionmentioning

confidence: 99%

Optimization of Norbornadiene Compounds for Solar Thermal Storage by First‐Principles Calculations

et al. 2016

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Molecular photoswitches capable of storing solar energy are interesting candidates for future renewable energy applications. Here, using quantum mechanical calculations, we carry out a systematic screening of crucial optical (solar spectrum match) and thermal (storage energy density) properties of 64 such compounds based on the norbornadiene-quadricyclane system. Whereas a substantial number of these molecules reach the theoretical maximum solar power conversion efficiency, this requires a strong red-shift of the absorption spectrum, which causes undesirable absorption by the photoisomer as well as reduced thermal stability. These compounds typically also have a large molecular mass, leading to low storage densities. By contrast, single-substituted systems achieve a good compromise between efficiency and storage density, while avoiding competing absorption by the photo-isomer. This establishes guiding principles for the future development of molecular solar thermal storage systems.

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“…Energy storage can also be accomplished through photoisomerization 8 . A considerable number of molecular solar thermal (MOST) systems incorporating organic compounds, including anthracene 9,10 , azobenzene [11][12][13] , dihydroazulene 14,15 , norbornadiene-quadricyclane [16][17][18] , stilbene 19,20 , and ruthenium fulvalene derivatives 21,22 , which can undergo light-induced isomerization to metastable isomers for storage of solar energy, have been proposed.…”

mentioning

confidence: 99%

A new approach exploiting thermally activated delayed fluorescence molecules to optimize solar thermal energy storage

et al. 2022

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We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular composites based on the TADF core phenoxazine–triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S1-T1 energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule’s triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.

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A high enthalpy value in thermal isomerization of photosynthesized cis-9-styrylacridines

Cited by 23 publications

References 5 publications

Comparative Ab-Initio Study of Substituted Norbornadiene-Quadricyclane Compounds for Solar Thermal Storage

Comparative Ab-Initio Study of Substituted Norbornadiene-Quadricyclane Compounds for Solar Thermal Storage

Optimization of Norbornadiene Compounds for Solar Thermal Storage by First‐Principles Calculations

A new approach exploiting thermally activated delayed fluorescence molecules to optimize solar thermal energy storage

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