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Published on: December 27, 2018
Excitonic coupling of electronic transitions in oligomeric phthalocyanine zinc(II) complexes
Sergey G Makarov1, Sergey Yu Ketkov1, Dieter Wöhrle2
1G.A. Razuvaev Institute of Organometallic Chemistry of RAS, Tropinin str. 49, 603950 Nizhniy Novgorod, Russia. makar@iomc.ras.ru.
Abstract:
The excitonic coupling of the electronic transitions in a series of zinc(II) phthalocyanine (ZnPc) dimers has been studied using TD-DFT with the range-separated hybrid functional LC-BLYP. This method correctly reproduces the experimental excitonic Q-band shifts for structurally rigid, non-conjugated binuclear phthalocyanines. The observed significant differences in the experimental UV/vis spectra for "edge-to-edge", "slipped-stacked" and "face-to-face" arrangements have been explained. The long-range coulombic contribution to the excitonic coupling has been evaluated using transition electrostatic potential (TrESP) atomic charges, revealing how the classical Kasha point-dipole model interfaces with short-range excitonic interactions determined by π-MO overlap. The excitonic splitting of the Q-band has been extrapolated from Pc oligomers to an infinite 1D-stack using the tight-binding model, and the main spectral features of α- and β-modifications of ZnPc have been correctly reproduced.
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