Resonance Raman spectroscopy and theoretical study on the photodissociation dynamics of formanilide in S₃ state

Abstract

Resonance Raman spectra were obtained for formanilide (FA) in acetonitrile solution with 239.5-and 245.9-nm excitation wavelengths in resonance with the S 3 state, and density functional theory (DFT) was used to elucidate the electronic transitions and resonance Raman spectra of FA. The spectra indicate that, in the Franck-Condon region, photodissociation dynamics has a multidimensional character with the motions mainly along the C O stretching υ 8 , the ring C C stretch υ 9 , the NH wag and ring CCH in-plane bend υ 11 , the NH wag and ring CCH in-plane bend υ 12 , ring C C stretch and ring CCH in-plane bend υ 16 , the NH wag and ring CCH in-plane bend υ 17 , the ring CCH in-plane bend υ 18 , and the ring trigonal bend υ 24 . The excited-state dynamics of the S 3 state is discussed, and the results are compared with those previously reported for benzamide (BA) to examine the Nor C-terminal-substituted aromatic effect of the peptide bond.

Excited-State Structural Dynamics of Propanil in the S2 State: Resonance Raman and First-Principle Investigation

“…Figure only indicates the largest Raman band contributions to each Raman feature of the spectra since the intensity of some Raman bands in the spectrum may have contributions from several Raman bands which have very close Raman shifts due to the limited resolution of the solution-phase spectra. Vibrational spectra of formanilide, N -(2-methylphenyl)-2,2-dichloroacetamide (2MPA), and N -(4-methylphenyl)-2,2-dichloroacetamide (4MPA) were used as references to assign vibrational modes of propanil. , Most of the resonance Raman features can be assigned to the fundamentals, overtones, and combination bands of Franck–Condon active vibrational modes on the basis of the information presented in Table : CO stretch, ν 51 (1659 cm –1 ), ring CC stretch, ν 50 (1590 cm –1 ), NH wag/ring CC stretch, ν 49 (1534 cm –1 ), ring CCH in-plane bend/NH wag, ν 42 (1383 cm –1 ), NH wag/–CH 2 – rock, ν 41 (1353 cm –1 ), ring CC stretch/NH wag/–CH 2 – rock in-plane, ν 40 (1299 cm –1 ), Ph–NH stretch/ring CCH in-plane bend, ν 37 (1236 cm –1 ), ring CCH in-plane bend, ν 35 (1150 cm –1 ), −CH 2 CH 3 twist, ν 33 (1080 cm –1 ), ring trigonal bend, ν 31 (1029 cm –1 ), ring CCH bend out-of-plane, ν 27 (899 cm –1 ), whole skeleton deformation in-plane, ν 20 (688 cm –1 ). Figure clearly shows that the ring CC stretch vibration, ν 50 , ring CC stretch/NH wag/–CH 2 – rock in-plane, ν 40 , and Ph–NH stretch/ring CCH in-plane bend, ν 37 , dominate the S 2 excited-state structural dynamics of propanil.…”

“…Propanil is a derivative of formanilidel; therefore, comparison between them is performed in this work. Formanilide has a transition-allowed band at 240 nm, which belongs to the π[Ph–NHCOH] → π*[benzene ring] (S 0 →S 3 ) transition . Formanilide is the simplest N-terminal-substituted aromatic amide, and its excited-state charge transfer dynamics was noted to involve the whole molecule after ionization. − The transition-allowed band S 0 → S 2 of propanil at 251 nm has been assigned to the π[2Cl–Ph–NHCO] → π*[2Cl–Ph–NHCOCH 2 CH 3 ] transition, as Table and Figure show.…”

An adduct of Cl-substituted benzotriazole and hydroxy benzophenone as a novel UVA/UVB absorber: Theory-guided design, synthesis, and calculations

“…Quantum chemistry method TD DFT has been used to simulate the UV absorption spectra successfully [8][9][10]. Fig.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part VI

“…Pei et al . carried out resonance Raman scattering with 239.5‐ and 245.9‐nm excitation wavelengths and a DFT theoretical analysis of the photodissociation dynamics of formanilide in S 3 state . Tardioli and co‐workers elucidated the structure of fluorescent H1 antihistamines by ultraviolet resonance Raman spectroscopy to learn more about the solution structures of tripelennamine and mepyramine .…”