Properties of the low-lying electronic states of phenanthrene: Exact PPP results

Abstract

mWe report properties of the exact low-lying states of phenanthrene, its anion and dianion within the Pariser-Parr-Pople (PPP) model. The experimentally known singlet states of the neutral molecule are well reproduced by the model. The intensities for one and two photon absorption to various singlet states are also in good agreement with experiment. From the bond orders of these states, we predict the equilibrium geometries. The relaxation energies of these states, computed from charge-charge correlations and bond orders, are presented. We also present results of ring current calculations in the singlet ground state of phenanthrene. We have also reported energies, spin densities, bond orders, and relaxation energies of several triplet states and compared them with experiments as well as with other calculations, where available. The fine structure constants D and E , computed in the lowest triplet state, compare well with those obtained from experiments. These properties are also presented for the anions and the dianions. The PPP model in these cases predicts a low-energy ( < 1 eV) dipole excitation.

Two-photon absorption spectroscopy of trans-stilbene, cis-stilbene, and phenanthrene: Theory and experiment

“…[28][29][30][31][32] Whereas trans-stilbene photoisomerizes to cis-stilbene, the reverse isomerization reaction competes with electrocyclization of cis-stilbene to 4a,4b-dihydrophenanthrene, which irreversibly oxidizes to phenanthrene. 25 Numerous excited-state calculations at various levels of theory have been reported for trans-stilbene, 26,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] cis-stilbene, 26,38,39,[41][42][43][44][45][46][47]49,50 and phenanthrene, [51][52][53] with some of the most comprehensive work by Merchan and coworkers using CASPT2 (complete active space self-consistent field with second-order perturbative correction). 48,50,53 However, there have been only a limited number of studies on the 2PA properties, and the reported cross sections vary by orders of magnitude.…”

Benchmarking Second Order Methods for the Calculation of Vertical Electronic Excitation Energies: Valence and Rydberg States in Polycyclic Aromatic Hydrocarbons

“…Phenanthrene like azulene has no center of symmetry. Possible resonance structures of phenanthrene have been discussed by Chakrabarti et al 137 The classification of biphenylene has been intensively discussed. 123,[138][139][140][141][142] Depending on how the electrons are counted, either as two benzene molecules with 6π electrons or collectively as 12π electrons, which equals 4n with n ) 3, biphenylene should be considered as an aromatic or as an antiaromatic molecule.…”

“…Phenanthrene like azulene has no center of symmetry. Possible resonance structures of phenanthrene have been discussed by Chakrabarti et al The classification of biphenylene has been intensively discussed. ,− Depending on how the electrons are counted, either as two benzene molecules with 6π electrons or collectively as 12π electrons, which equals 4 n with n = 3, biphenylene should be considered as an aromatic or as an antiaromatic molecule. In the work of Beck et al it was argued that the length of the bonds between the two ring systems is large enough to ensure that there is no interaction between the two ring systems and that biphenylene can be regarded as an aromatic molecule.…”