Electronic states of azabenzenes and azanaphthalenes: A revised and extended critical review

Vibrational Spectra of the Azabenzenes Revisited: Anharmonic Force Fields

“…Moreover, by using scaled HF frequencies, Wiberg [58] has suggested that the assignment for ν 10 might also be incorrect. The IRM [29] assignments for modes 5, 6, 13 and 21 appear more plausible than from Ref. [52].…”

“…It would be interesting to reanalyze their data based on the present anharmonic force fields, although this still would not resolve the problems associated with the C-H stretches, for which large basis set coupled cluster frequencies would be desirable. The experimental IR/Raman data of Daunt et al [62] and Lancaster et al [63] are very similar to those of IRM [29] and are not listed in Table VIII. With the exception of the first e ′′ ν 12 and the C-H stretches, which are again underestimated, all computed values are within 11 cm −1 of experiment Again, the errors are similar to the other azabenzenes; including the C-H stretches, the mean absolute error is 7.6 cm −1 and the RMS error 11 cm −1 . Excluding the stretches (and ν 12 ), these numbers reduce to 5.1 (3.4) and 7.5 (5.0) cm −1 , respectively.…”

“…If we combine the CCSD(T)/ANO4321 harmonic frequencies with the B97-1/TZ2P anharmonic corrections, the picture brightens somewhat. Compared to the assignment of IRM [29], the RMS deviation amounts to 9.8 cm −1 if the symmetric C-H stretch is excluded.…”

Dynamics of radiationless transitions in large molecular systems: A Franck–Condon-based method accounting for displacements and rotations of all the normal coordinates

“…Indeed, that problem has attracted considerable interest over the past years and therefore experimental and theoretical data are abundant in the literature. [37][38][39][40][41][42][43][44][45][46][47] The absorption spectrum of pyrazine exhibits a well structured band for the S 0 → S 1 (π, π * ) transition and a broad, less structured band for the S 0 → S 2 (n, π * ) one. 37,38 The most significant feature of the S 1 absorption band is the presence of an anharmonic progression of the b 1g mode (ν 10a ); since the molecular symmetry (D 2h ) is retained upon transition to S 1 , 43,46,48 odd transitions of that progression are not allowed in the Franck-Condon approximation (strong frequency variation could be responsible for even transitions), so that other mechanisms must be invoked.…”

Efficient on-the-fly ab initio semiclassical method for computing time-resolved nonadiabatic electronic spectra with surface hopping or Ehrenfest dynamics

“…The pyrazine molecule exhibits a conical intersection between the first (S 1 ) and second (S 2 ) bright excited states, which influences the dynamics after excitation and the resulting vibronic spectra. Because the pyrazine molecule provides an almost ideal benchmark, its vibronic spectra have been extensively studied both experimentally [37][38][39][40][41][42][43][44][45][46] and theoretically, 6,25,26,31,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] giving us an opportunity not only to assess the accuracy of the MSDR in relation to experiment but also to compare it with exact quantum calculations on simplified models developed by others. In addition, due to efficiency of the MSDR, we were able to go beyond simplified model systems and to compute the absorption spectrum using the ab initio electronic structure computed on the fly in all 24 dimensions.…”