A reexamination of the oxygen parameters in the CNDO/S method. Application to UV and photoelectron spectra of p-benzoquinone

Complexation of Fluorenone and Xanthone to Cyclodextrins: Comparison of Theoretical and Experimental Studies

“…The calculated energies appear overestimated especially for the low-lying π,π* transitions, as frequently found with the present method for carbonyl compounds. 40,41 The relative intensities of the lowand high-energy bands are well reproduced by the calculations for the complex with -CD, whereas in the case of R-CD the intensity of the short-wavelength band is overestimated. The calculated spectra show a fairly high consistency with the signs of the bands around the most stable energy minima calculated.…”

An ab initio CI study of the ground and excited states of p-benzoquinone

“…Cowan et al [20] performed extended Hiickel calculations on PBQ and assigned the PES bands as n, ~r, n, ~r, which is also supported by the CNDO/2 calculation [11]. Downloaded by [Michigan State University] at 16:09 07 February 2015 Bigelow [21] assigned, using the CNDO/S method with empirical corrections, the ordering n, ~r, 7r, n and most recently Jacques et al [19] gave the ordering 7r, ~, n, n, after re-examining the oxygen parameter in the CNDO/S method. Dougherty and McGlynn [13] reported four vertical ionization energies for PBQ and some selected derivatives between 9.0 and 11-0 eV region.…”

“…Several ab initio [14][15][16][17][18] and semiempirical MO studies [11][12][13][19][20][21] are also available in the literature.…”

“…More recently, Martin and Wadt [17] critically examined the lower lying nrr* states of PBQ by carrying out an extensive CI calculation employing a minimal gaussian basis set and compared the CI result based on the MO method to the valence-bond description. Jacques et al [19] reported a semiempirical CNDO/S calculation on the nrr* and rrrr* singlet states and ionization potentials by improving the oxygen parameters in the CNDO/S method. These theoretical studies have dealt Downloaded by [Michigan State University] at 16:09 07 February 2015 T.K.…”

Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids

“…The lowest two singlet-singlet excitations are from n orbitals to the delocalized π * C O+CC orbital, the third and fourth excitations are from π CC and π CO + CC orbitals to π * C O+CC orbital, respectively. Several semiempirical [74][75][76] and ab-initio 77-79 studies on the excited states of p-benzoquinone show that the first two excitations have n → π * character followed by two π → π * excitations. These excitations survive in the field up to 30 MV/cm.…”