Study of Vibronic Spectra of Tetrabenzoporphin Based on Normal-Coordinate Analysis

Fermi-type resonance in quasi-linear fluorescence excitation spectra of triazatetrabenzoporphine

“…Furthermore, the conclusion that vibrations of H 2 TBP with frequencies near 1600 cm -1 belong to methine bridges (νC m C a ) was based on the lack of such frequencies in fluorescence QLS of H 2 Pc and tetraazaporphine (H 2 TAP) whereas they are observed for porphine. This is confirmed by calculations of normal vibrations for H 2 TBP [14,15] and ZnPc [16]. Because quasi-lines corresponding to frequencies below 1550 cm -1 for H 2 Pc and H 2 TAP are rather strong, the frequency 1583 cm -1 of H 2 TrATBP can rather confidently be assigned to a vibration with a large contribution from νCC of the methine bridge.…”

“…Furthermore, second components of Fermi doublets, designated by us F 2 (1) and F 2 (2) , appeared at 1023 and 1022 cm -1 . In order to explain this, we return to H 2 TBP [14,15] and H 2 Pc [6]. We repeat that, as the calculation showed, the agreement was not good for the PED between the three vibrations of H 2 TBP that were sensitive to N-deuteration and the corresponding frequencies of D 2 TBP.…”

“…For example, both the experi-* The transition intensity into this state from the ground state is borrowed by the weak transition through resonance interaction. ment and the calculations of normal vibrations for H 2 TBP indicate that three vibrational frequencies of the S 0 state are sensitive to N-deuteration: 907, 1020, and 1228 cm -1 , which for D 2 TBP correspond to 804, 1053, and 993 cm -1 [14,15]. Moreover, the shapes of vibrations that can be compared to each other are quite different.…”

“…Moreover, the shapes of vibrations that can be compared to each other are quite different. It is also noteworthy that the calculation [14,15] gives a finite contribution of δNH to the PED of the vibration with frequency 1347 cm -1 (theoretical value). Analogous frequencies for H 2 Pc were seen in data for the S 1 state: 905, 1110, and 1205 cm -1 , which for D 2 Pc correspond to 869, 1006, and 988 cm -1 .…”

“…We repeat that, as the calculation showed, the agreement was not good for the PED between the three vibrations of H 2 TBP that were sensitive to N-deuteration and the corresponding frequencies of D 2 TBP. Preference was given to the correlation 907 (H) -864 (D), 1020 (H) -1053 (D), and 1228 (H) -993 (D) cm -1 based on a thorough analysis [14,15]. The frequency increased upon deuteration of porphine and its derivatives and was explained by a change of the shape of normal vibrations [2].…”