Photodeactivation paths in norbornadiene

Abstract

The first high level ab initio quantum-chemical calculations of potential energy surfaces (PESs) for low-lying singlet excited states of norbornadiene in the gas phase are presented. The optimization of the stationary points (minima and conical intersections) and the recalculation of the energies were performed using the multireference configuration interaction with singles (MR-CIS) and the multiconfigurational second-order perturbation (CASPT2) methods, respectively. It was shown that the crossing between valence V2 and Rydberg R1 states close to the Franck-Condon (FC) point permits an easy population switch between these states. Also, a new deactivation path in which the doubly excited state with (π3)(2) configuration (DE) has a prominent role in photodeactivation from the R1 state due to the R1/DE and the DE/V1 conical intersections very close to the R1 and DE minima, respectively, was proposed. Subsequent deactivation from the V1 to the ground state goes through an Olivucci-Robb-type conical intersection that adopts a rhombic distorted geometry. The deactivation path has negligible barriers, thereby making ultrafast radiationless decay to the ground state possible.

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

“…Antol has established a possible explanation for the low quantum yield of the unsubstituted system using decay paths via Rydberg states and doubly excited states. 24 Rydberg states were not considered in this work but we point out that the S 2 as displayed in Figure 2 is a doubly excited state, and its position does not red-shift upon substitution with aryls.…”

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

“…One should in fact require ħω 1 ≥Δ E s +Δ E a +δ E , where ħω 1 is the energy difference between S 0 and S 1 in the norbornadiene configuration and δE denotes the energy variation between the norbornadiene and saddle point configurations on S 1 (Figure ). Based on calculations, δE typically ranges between 0.5 and 1.0 eV, where the latter value applies to the unsubstituted compound ( HH ). This constraint immediately rules out all compounds based on A7 and all double‐substituted compounds based on A6 .…”

Catalytically Triggered Energy Release from Strained Organic Molecules: The Surface Chemistry of Quadricyclane and Norbornadiene on Pt(111)

“…Such chemical energies can be released at will, which implies an intrinsic storagef unction. [19][20][21] The reactions of NBD and of its substituted derivatives proceed through the triplet state. One major challenge in the application of chemical-energy storages ystemsi st he complex catalytic reaction network that is typicallyr equired to transform the stable energy-lean molecule into its energy-rich counterpart and the other way round.…”

“…The photochemical conversion of the polycyclic nonsaturated NBD into its saturated, strained, and metastable valence isomer QC ( Figure 1) was described over half ac entury ago [6] and is still the most investigated candidate for energy storage in this class of compounds in experimental [7][8][9][10][11][12][13][14][15][16][17][18] and theoretical studies. [19][20][21] The reactions of NBD and of its substituted derivatives proceed through the triplet state. [22,23] Typically,t hese molecules are photosensitized, sometimes even with quantum yields approaching unity.…”

“…The prototypical example of such an energy‐carrier pair is norbornadiene (NBD) and its energy‐rich isomer quadricyclane (QC). The photochemical conversion of the polycyclic nonsaturated NBD into its saturated, strained, and metastable valence isomer QC (Figure ) was described over half a century ago and is still the most investigated candidate for energy storage in this class of compounds in experimental and theoretical studies . The reactions of NBD and of its substituted derivatives proceed through the triplet state .…”