Transient absorption spectra of tetraazaporphine and substituted derivatives of tetraazachlorin and tetraazabacteriochlorin were obtained upon picosecond excitation with various probe pulse delay times in order to resolve the open question about the reasons for fluorescence quenching in tetraazaporphine hydrogenated derivatives. The quantum yield of triplet state T 1 formation has been estimated. It has been shown that in all investigated cases radiationless de-excitation of the fluorescent level S 1 occurs by two channels: S 1 ‫ב‬ T 1 and S 1 ‫ב‬ S 0 , the latter being predominant. As the S 1 level becomes lower, the transition rate for this channel increases. For tetraazaporphine and its derivatives, a quasi-photochemical mechanism is proposed that accounts for the anomalous efficiency of the S 1 ‫ב‬ S 0 channel in the dissipation of the electronic excitation energy.Introduction. Bridging tetraaza-substitution in the tetrapyrrole macrocycle and hydrogenation of the pyrrole rings is one of the factors capable of causing fundamental changes in the electronic spectra of porphine derivatives. Combination of these factors deserves consideration as a method for creating compounds with controlled properties. Spectral and luminescence characteristics of hydrogenated tetraazaporphine derivatives (also called porphyrazine) have been well studied [1][2][3][4][5][6][7][8].Studies showed that hydrogenation of one or two opposed pyrrole rings in tetraazaporphine (H 2 TAP) causes significant fluorescence quenching [1,3,5,8]. This quenching may be due to an increase of the probabilities for the two radiationless intramolecular processes of intersystem crossing S 1 ‫ב‬ T 1 , k ST , and internal conversion S 1 ‫ב‬ S 0 , i.e., energy exchange of the S 1 electronic state onto vibrations of the molecule in the ground state S 0 , the probability of which increases with lowering of the S 1 level. Preference has been given to the first de-excitation channel [1, 3, 5] on the basis of indirect literature data, in particular, a comparison with fluorescence of bacteriochlorin [9] and 2,3-naphthalocyanine [10] derivatives. In these instances, lowering of the S 1 level was also accompanied by fluorescence quenching although the quenching was weaker. Both pathways were mentioned in another study [8].The kinetics of absorption spectra upon picosecond excitation of H 2 TAP, dibenzobarrelene-substituted tetraazachlorin (H 2 TAC t ), and dibenzobarrelene-substituted tetraazabacteriochlorin (H 2 TABC

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