Oxalyl halides

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part I: Reanalysis of the 3680Å and 4100Å absorption systems of oxalyl chloride

“…However, no data on the structure of the second conformers of oxalyl halides in excited electronic states are available. Earlier, only transitions of the trans-conformers were observed in the vibronic absorption spectra of oxalyl halides [14,16,[18][19][20], although according to vibrational spectroscopy and electron diffraction studies, the values of conformer energy (enthalpy) differences of oxalyl halides in the ground electronic state in the gas phase were relatively small, and the content of the second conformers was rather high [2,[4][5][6][9][10][11]22].…”

“…It was also found that upon electronic excitation to the lowest singlet and triplet electronic states, the trans-conformers of glyoxal [12,13] and oxalyl halides [14][15][16][17][18][19][20], as well as the cis-conformer of glyoxal (upon singlet-singlet excitation) [21], keep a planar structure. However, no data on the structure of the second conformers of oxalyl halides in excited electronic states are available.…”

“…Previously, the near-ultraviolet vapor-phase absorption spectrum of oxalyl chloride has been investigated in a number of publications [23][24][25][26], and in more detail in [18,19]. The 3680 Å and 4100 Å systems were assigned to singlet-singletà 1 A u X1 A g [18] and singlet-tripletã 3 A u X1 A g [19] electronic transitions of the trans-conformer, respectively.…”

“…The 3680 Å and 4100 Å systems were assigned to singlet-singletà 1 A u X1 A g [18] and singlet-tripletã 3 A u X1 A g [19] electronic transitions of the trans-conformer, respectively. Electronic transition origins (0 0 0 ), totally symmetric vibrations m 1 À m 5 (a g ) in the ground and excited electronic states, the tentative ''forbidden" vibrations m 0 8 (b g ), and some sequences were found.…”

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part V: Oxalyl chloridefluoride (COCl–COF)

“…In spite of the low symmetry, the orbital character in the singlet states (Ã 1 A 00 andB 1 A 00 ) is similar to that in molecules with equivalent CXO fragments (COCl) 2 and (COF) 2 [2,3] and approximately correspond to symmetric and antisymmetric combinations of bonding and antibonding p C=O and non-bonding n O orbitals localized on different fragments. The analyses of the vibronic absorption spectra of (COX) 2 (X = H, F, Cl, Br) [1,4,[32][33][34][35][36][37] established the equivalence of CXO fragments for the trans conformers, at least in the first excited singlet and triplet electronic states. For COCl-COF molecule, the excitation can be localized on one of the carbonyl fragments due to lower symmetry.…”