1,2,5-Chalcogenadiazole-Annulated Tripyrazinoporphyrazines: Synthesis, Spectral Characteristics, and Influence of the Heavy Atom Effect on Their Photophysical Properties
Abstract
A series of low-symmetry Zn-II, Mg-II, and metal-free porphyrazine derivatives with one 1,2,5-chalcogenadiazole ring (with S, Se or Te) and three pyrazines bearing tert-butylsulfanyls were synthesized. The absorption maxima of Zn-II complexes lay at 660, 674, and 707 nm for S, Se, and Te, respectively, indicating increasing contribution of the 1,2,5-chalcogenadiazole rings to the p-electronic system.
Photophysical studies revealed that introduction of Se as a chalcogen and Zn-II as a central metal causes an increase in the singlet oxygen quantum yield, reaching a value of 0.81, whereas the combination of S and Mg-II gives only 0.39. This takes place on the account of the fluorescence quantum yields that differ significantly from 0.072 (Zn-II+Se) to 0.51 (Mg-II+S).
These results demonstrated the two-dimensional heavy atom effect combining the role of the chalcogen (first dimension) as well as the central metal (second dimension). Attempts to prepare oxygen-containing isologues led to the formation of an unexpected side product.