Annulated Dinuclear Metal-Free and Zn(II) Phthalocyanines: Photophysical Studies and Quantum Mechani
June 29th, 2008 | by admin |Annulated Dinuclear Metal-Free and Zn(II) Phthalocyanines: Photophysical Studies and Quantum Mechanical Calculations.
The results of steady-state and time-resolved absorption and fluorescence experiments as well as quantum mechanical density functional theory (DFT) calculations of metal-free and Zn(II) mononuclear and dinuclear (sharing a common benzene ring) phthalocyanines are presented. A detailed comparison between measured and calculated absorption spectra of all compounds is done, showing a good agreement between theory and experiment. The NH tautomerization for phthalocyanines with an extended pi-electron system was shown for the first time at room temperature. The photophysical properties of all possible NH tautomers of metal-free dinuclear Pc have been fully characterized. In the first tautomer, Pc ( parallel), both pairs of hydrogen atoms are parallel to the connection line of two Pc units. The maximum of the lowest-energy Q absorption band, lambda abs, in Pc ( parallel) is located at 832 nm, whereas the spectral position of the fluorescence maximum lies at lambda fl = 837 nm. The second NH tautomer, Pc ( perpendicular) (lambda abs = 853 nm, lambda fl = 860 nm), presents the two pairs of hydrogen atoms perpendicularly orientated to the covalent axis, and the third one, Pc (mix) (lambda abs = 864 nm, lambda fl = 872 nm), contributing in a minor extend to the absorption and fluorescence spectra of the metal-free dinuclear phthalocyanine, has one perpendicular and one parallel pair of hydrogen atoms. Obviously, only one configuration exists in the case of the Zn(II)-containing dinuclear phthalocyanine (lambda abs = 845 nm, lambda fl = 852 nm).
Litwinski C, Corral I, Ermilov EA, Tannert S, Fix D, Makarov S, Suvorova O, GonzaÌlez L, Wöhrle D, Röder B.
litwinsk@physik.hu-berlin.de, ines.corral@unijena.de, woehrle@chemie.unibremen.de.