Tunable Photoswitching in Norbornadiene (NBD)/Quadricyclane (QC) – Fullerene Hybrids

Abstract

With respect to molecular switches, initializing the quadricyclane (QC) to norbornadiene (NBD) back‐reaction by light is highly desirable. Our previous publication provided a unique solution for this purpose by utilizing covalently bound C60. In this work, the fundamental processes within these hybrids has been investigated. Variation of the linker unit connecting the NBD/QC moiety with the fullerene core is used as a tool to tune the properties of the resulting hybrids. Utilizing the Prato reaction, two unprecedented NBD/QC – fullerene hybrids having a long‐rigid and a short‐rigid linker were synthesized. Molecular dynamics simulations revealed that this results in an average QC–C60 distance of up to 14.2 Å. By comparing the NBD–QC switching of these derivatives with the already established one having a flexible linker, valuable mechanistic insights were gained. Most importantly, spatial convergence of the QC moiety and the fullerene core is inevitable for an efficient back‐reaction.

Aza-bicyclooctadiene/tetracyclooctane couples as promising photoswitches for molecular solar thermal energy storage applications

“…4,[27][28][29] Hitherto, a variety of photochromic couples have been explored including azobenzenes, anthracene dimers, dihydroazulene/ vinylheptafulvene couples, tetracarbonyl-fulvalenediruthenium complexes, norbornadiene/quadricyclane (NBD/ QC) couples, etc. 1,2,5,10,11,17,18,27,28,[30][31][32][33][34][35][36][37][38][39][40][41] Among them, NBD/QC is the most studied photochromic couple for MOST application owing to its comparatively higher storage energy density. 1,6,29,[42][43][44][45][46] Moth-Poulsen and co-workers have made significant efforts to tailor the properties of photoswitching couples for MOST application.…”

Aza-bicyclodiene based photoswitches for molecular solar thermal energy storage

“…, are known. 5,21,29,32,33,36–55 Among all, the NBD/QC couple, which involves the [2+2]-cycloaddition of bridged bicyclodiene molecule to give a strained metastable photoadduct is extensively investigated for MOST applications due to its high energy storage density. 5,22,31,41,54–56 However, the low thermal back-reaction barrier and optical absorption in the UV region hinders its practical applicability as an effective MOST systems.…”

“…5,[17][18][19]21,22,[27][28][29][30][31][32][33][34][35] Hitherto, a variety of molecular photoswitches, including the tetracarbonyl-fulvalene-diruthenium complexes, anthracenes, norbornadiene/quadricyclane (NBD/ QC), dihydroazulene/vinylheptafulvene, azobenzenes, etc., are known. 5,21,29,32,33,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Among all, the NBD/QC couple, which involves the [2+2]-cycloaddition of bridged bicyclodiene molecule to give a strained metastable photoadduct is extensively investigated for MOST applications due to its high energy storage density. 5,22,31,41,[54][55][56] However, the low thermal backreaction barrier and optical absorption in the UV region hinders its pra...…”

“…5,21,29,32,33,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Among all, the NBD/QC couple, which involves the [2+2]-cycloaddition of bridged bicyclodiene molecule to give a strained metastable photoadduct is extensively investigated for MOST applications due to its high energy storage density. 5,22,31,41,[54][55][56] However, the low thermal backreaction barrier and optical absorption in the UV region hinders its practical applicability as an effective MOST systems. [16][17][18] En route to make NBD/QC couple relevant for the practical real-life application, research has also been conducted to tune their thermochemical and photophysical properties via different substitutions.…”

Optimizing the performance of phase-change azobenzene: from trial and error to machine learning

“…1 illustrates the energy storage mechanisms of various common molecular photoswitches. Norbornadiene (NBD)/quadricyclane (QC), [19][20][21][22] anthracene, [23][24][25] FvRu 2 (CO) 4 , 26,27 and dihydroazulene (DHA)/vinylheptafulvene (VHF) [28][29][30][31] store energy via molecular structure alterations, differing from the energy storage mechanism of azobenzene (Azo). 32,33 Azo comprises two benzene rings linked by an Azo bond and exists in both cis and trans configurations.…”