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Excitation Localization/Delocalization Isomerism in a Strongly Coupled Covalent Dimer of 1,3-Diphenylisobenzofuran

Schrauben, Joel N.
Akdağ, Akın
Wen, Jin
Havlas, Zdenek
Ryerson, Joseph L.
Smith, Millie B.
Michl, Josef
Johnson, Justin C.
Two isomers of both the lowest excited singlet (S-1) and triplet (T-1) states of the directly para, para'-connected covalent dimer of the singlet-fission chromophore 1,3-diphenylisobenzofuran have been observed. In one isomer, excitation is delocalized over both halves of the dimer, and in the other, it is localized on one or the other half. For a covalent dimer in solution, such "excitation isomerism" is extremely rare. The vibrationally relaxed isomers do not interconvert, and their photophysical properties, including singlet fission, differ significantly.