Quantum-Chemical Calculations for the Electronic Absorption Spectra of Certain Anthocyanidins

Semi-empirical PM3 calculations are made for the electronic absorption spectra of colored forms nonmethylated anthocyanidins (aurantinidin, pelargonidin, cyanidin, and delphinidin). The position band peak is shown to depend on orientation hydroxyl groups in aglycone structure. observed tendency toward a bathochromic shift after ОН added ring generally corresponds experimental data. results uncharged quinonoid pelargonidin (a hypsochromic bands) do not this case agree with prevailing opinion specialists about shift. While confirmed by DFT calculations, there still no reliable data their validity. formation single-charged (negatively) structures clearly reason bands, which consistent When charge multiplicity increases (to −2), bands experimentally yellow color anthocyanins alkaline solutions again predicted.