2024-08-22 米国国立再生可能エネルギー研究所(NREL)
＜関連情報＞
- https://www.nrel.gov/news/program/2024/nrel-research-synthesizes-molecular-aggregates-for-solar-energy-applications.html
- https://pubs.acs.org/doi/10.1021/jacs.4c02058
エネルギーの流れを三重項ペアに向けるテトラセン二酸集合体 Tetracene Diacid Aggregates for Directing Energy Flow toward Triplet Pairs
Nicholas F. Pompetti,Kori E. Smyser,Benjamin Feingold,Raythe Owens,Bimala Lama,Sandeep Sharma,Niels H. Damrauer,Justin C. Johnson
Journal of the American Chemical Society Published: April 12, 2024
DOI:https://doi.org/10.1021/jacs.4c02058
Abstract
A comprehensive investigation of the solution-phase photophysics of tetracene bis-carboxylic acid [5,12-tetracenepropiolic acid (Tc-DA)] and its related methyl ester [5,12-tetracenepropynoate (Tc-DE)], a non-hydrogen-bonding counterpart, reveals the role of the carboxylic acid moiety in driving molecular aggregation and concomitant excited-state behavior. Low-concentration solutions of Tc-DA exhibit similar properties to the popular 5,12-bis((triisopropylsilyl)ethynl)tetracene, but as the concentration increases, evidence for aggregates that form excimers and a new mixed-state species with charge-transfer (CT) and correlated triplet pair (TT) character is revealed by transient absorption and fluorescence experiments. Aggregates of Tc-DA evolve further with concentration toward an additional phase that is dominated by the mixed CT/TT state which is the only state present in Tc-DE aggregates and can be modulated with the solvent polarity. Computational modeling finds that cofacial arrangement of Tc-DA and Tc-DE subunits is the most stable aggregate structure and this agrees with results from 1H NMR spectroscopy. The calculated spectra of these cofacial dimers replicate the observed broadening in ground-state absorption as well as accurately predict the formation of a near-UV transition associated with a CT between molecular subunits that is unique to the specific aggregate structure. Taken together, the results suggest that the hydrogen bonding between Tc-DA molecules and the associated disruption of hydrogen bonding with solvent produce a regime of dimer-like behavior, absent in Tc-DE, that favors excimers rather than CT/TT mixed states. The control of aggregate size and structure using distinct functional groups, solute concentration, and solvent in tetracene promises new avenues for its use in light-harvesting schemes.
