The ground and ionic states of cyclohepta-1,3,5-triene and their relationship to norcaradiene states: New 1H and 13C NMR spectra and analysis of a new experimental photoelectron spectrum by ab initio methods

Abstract

data (left) with spectra simulated using the values in Table II (right) SM4: 60 Mz simulation of H2-H5 signals using values in Table II (left) compared with experimental spectrum reproduced from Ref. 19 (right) SM5. The singly occupied molecular orbital of the 1 2 A / state, which is much more compact than the ground state, with higher bow and stern angles. SM6. The transition state for thermal interconversion of CHT to NCD. SM7. The HOMO for the transition state for thermal interconversion of CHT to NCD. SM8. MP3 and MP4SDQ harmonic vibrational frequencies for CHT compared with anharmonic values at the MP2 level, including rotational constants for the vibrationally excited states, some of which are present in the microwave spectrum. SM9. The singly occupied molecular orbital of the 1 2 A / state, which is much more compact than the ground state, with higher bow and stern angles. SM10. MP4SDQ harmonic vibrational frequencies for 1 2 A / state of CHT. SM11. The X 2 A // surface as a function of the two dihedral angles chosen. See main Paper. SM12. A 2-dimensional representation of SM11, showing the regular pattern generated as the G-16 'scan' process occurs. See main text for details. SM13. The avoided crossing under C 1 symmetry of the 2 A / and 2 A // states in C S symmetry.

The vacuum ultraviolet absorption spectrum of norbornadiene: Vibrational analysis of the singlet and triplet valence states of norbornadiene by configuration interaction and density functional calculations

“…One of these broad peaks is best seen by the logarithmic plot in SM1 as Figure SM1a. As in our recent studies of NBD, 1 cycloheptatriene (CHT) 2,3 and cyclooctatetraene (COT), 18,19 we use several computational chemistry suites since no single suite can offer us a complete analysis. These include two Gaussian versions (G-09 and G-16), 34 as discussed further in the supplementary material under SM2.…”

“…This corresponding triple combination series has maximum intensity for 5 1 12 19 39 1 . In addition to modes 12, 39 and 5, shown in Table III, other binary modes participating in the HT calculations for the 1 A2 state, in conjunction with 12 n , are: 10 1 , 10 3 , 10 5 , 10 7 (all b2), 19 1 , 18 1 ,17 1 (all a2), 38 1 , 38 3 , 37 1 , 34 1 , 33 1 (all b2), 28 1 , 26 1 , 25 1 , 24 1 , 23 1 (all b1), where the quanta are given in superscripts.…”

“…We note that mode 11 is almost exactly double the frequency of mode 12. As a consequence 12 3 is almost degenerate with the binary combination 11 1 12 1 ; both have much lower intensities than other members of their sequences. Other accidental near-degeneracies at the harmonic level are mode 9 with modes 11 + 12, and mode 7 with modes 10 + 11.…”

“…Both are isoelectronic with cycloheptatriene (CHT) which we also studied recently, but lack conjugated double bonds. 2,3 Our theoretical approaches will be similar to those which were successful with CHT.…”

“…10 The reverse reaction, where QC regenerates NBD with release of heat can occur via thermal or catalytic interaction, or even fluorescence. 7 When triplet sensitized using acetophenone, the NBD process appears to involve the two triplets, 3 NBD and 3 QC, followed by relaxation to QC, 10 but not all sensitizers behave similarly. 11 Since the nature of the triplet states involved in these processes are obscure; this has led us to include study the electron impact (EI) spectra of NBD.…”