A complete active space self-consistent field (CASSCF) ab initio study of phenol–N2: the properties of a weak hydrogen-bonded system in its S1 excited state

Resonance-enhanced multiphoton ionization (REMPI) spectroscopy of the 35Cl and 37Cl isotopomers of p-chloroanisole

“…The similarity of the calculated E 1 s is consistent with that of the experimental results. Table 4 lists the origins of the S 1 S 0 electronic transition energies (E 0 1 s) of phenol [27][28][29], anisole [30][31][32], aniline [33][34][35] and their para-halogen substituted derivatives [16,20,22,33,36]. The band origins of the S 1 S 0 vibrationless transitions of p-fluoroanisole and p-chloroanisole are 35 146 and 34 859 cm À1 , which are red-shifted by 1234 and 1524 cm À1 , respectively, relative to that of anisole.…”

The structure and binding energies of the van der Waals complexes of Ar and N2 with phenol and its cation, studied by high level ab initio and density functional theory calculations

“…Density functional theory ͑DFT͒ methods present an attractive way of treating these interactions, but most commonly used functionals fail to be sufficiently accurate for this purpose. These four complexes have been studied previously 9-27 by both theoretical 10,11,14,[16][17][18][19][20]22,23,[25][26][27] and experimental techniques [9][10][11][12][13][14][15][18][19][20][21][24][25][26] which have focused on the existence or otherwise of two possible minima, with Ar or N 2 bound either to the system of phenol or to its acidic ͑-OH͒ hydrogen atom giving a complex. 8 A class of van der Waals molecules which have been quite extensively studied spectroscopically, and given their small size provide a suitable target for theoretical study, are those between phenol and argon, or a range of simple diatomic molecules such as N 2 or CO. [9][10][11][12][13] In this paper, we choose to study four such complexes, the two neutral species between phenol and argon or molecular nitrogen, and the corresponding complexes involving the phenol cation.…”

An experimental and ab initio investigation of the low-frequency vibrations of coumaran

“…CI-singles gives a highly improbable equilibrium geometry, while CASSCF results show a poor comparison between the calculated and experimental values of ⌬E for the S 0 state. The nature of the S 1 state CASSCF electronic distribution has the effect of drawing electrons away from the -type bonding orbitals and populating the corresponding antibonding orbitals in a manner analogous to that found for phenol [37][38][39] ͑although this is consistent with that fact that the same active space is used for both molecules͒. The effect on aromatic bond order cannot be evaluated within the CASSCF model due to noninteger orbital occupancy, but it is to be expected that occupation of antibonding orbitals will result in a decrease in bond order compared to that in the S 0 state.…”

“…Harmonic frequency analyses were in somewhat better agreement with In an attempt to improve upon the poor CIS results, the S 1 geometry was further modeled using the CASSCF methodology with the cc-pVDZ basis set, and an ͑8, 7͒ active space consisting of the six , *-type and p orbital of the oxygen, i.e., analogous to that chosen for previous work on phenol. [37][38][39] This active space was expected to best represent the most important molecular orbital contributions to the S 0 , S 1 , and D 0 state geometries. The S 1 -S 0 transition energy, determined as the difference in energy between the optimized neutral ground-and excited-state geometries, was calculated as 37 915.4 cm Ϫ1 ͑C 1 symmetry͒, while the zeropoint corrected transition energy was found as 36 846.9 cm Ϫ1 ͑C 1 symmetry͒.…”

“…In the case of CASSCF calculations, an active space analogous to that used in previous phenol studies was chosen. [37][38][39] For consistency, neutral and ionic ground-state data were also computed within the CASSCF model chemistry.…”