Quadrupolar CyclopentaHiAceanthrylene-Based Electron Donor-Acceptor-Donor Conjugates: Charge Transfer Versuscharge Separation

摘要

Cyclopenta[hi]aceanthrylene (CPA) has been functionalized at two of its positions with electronically-inert trimethylsilylethynyl (1), as well as electron donating 4-ethynyl-N,N-dimethylaniline (2), ethynyl Zn(II)phthalocyanine (3), and ethynyl Zn(II)porphyrin (4) units. Consistent with X-ray crystal structures of 2 and 4, analyses of absorption and fluorescence of 2-4 prompt to strong electronic communication between CPA and the peripheral units, affording quadrupolar electron donor-acceptor-donor charge transfer conjugates. By virtue of their quadrupolar/dipolar charge transfer characters in the excited state, 2-4 exhibit fluorosolvatochromism. Transient absorption spectroscopy confirmed delocalized quadrupolar ground states and formation of weakly solvent stabilized quadrupolar singlet excited states. The latter transform into strongly stabilized dipolar excited states before deactivating to the ground state in 2 and give rise to a fully charge separated state in 3 and 4.