Electronic properties and aromaticity of substituted diphenylfulvenes in the ground (S0) and excited (T1) states

Nina Sadlej-Sosnowska

doi:10.1007/s11224-017-0995-y

Abstract

In the present account, we investigate electronic properties of diphenylfulvene and its derivatives substituted in phenyl rings. The results were compared with the analogous properties of fulvene and its derivatives with the same substituents at the exocyclic carbon atom. All properties were evaluated and compared in the ground electronic S0 state and in the first excited T1 triplet state. These properties are dipole moments, charges, number of π electrons, and aromaticity of the fulvenic, five-membered ring in the two sets of compounds. The latter property was estimated by the harmonic oscillator model for aromaticity (HOMA) index and, for the fulvenes group, by the calculation of aromatic stabilization energy in both electronic states. It was also investigated whether Baird’s rule alone can account for the aromaticity differences in the two electronic states.

Highlights

Diphenylfulvene is a derivative of fulvene, a nonalternant hydrocarbon, which is an isomer of benzene
The starting point for our investigations was the calculation of dipole moments of eight diphenylfulvenes in the S0 and to 0.01 e (T1) states and their comparison with the analogous properties of fulvenes bearing the same substituents
The five-membered ring charges in both groups of compounds strongly depend on the electronic properties of substituents, both in the S0 and T1 states

Summary

Introduction

Diphenylfulvene is a derivative of fulvene, a nonalternant hydrocarbon, which is an isomer of benzene. Diphenylfulvenes, substituted at the para position in benzene ring, are shown in Scheme 1. The structures presently considered were as follows: diphenylfulvenes substituted at phenyl rings and, for comparison, fulvenes with exocyclic substituents. Scheme 1 Molecule of diphenylfulvene substituted in phenyl rings. In fulvenes, numbering of the atoms from C1 to C10 is the same. Struct Chem (2018) 29:23–31 the open-chain polyene which contains the same numbers of carbon atoms. This view has been shared in a few papers but none have estimated either the resonance energy for fulvenes or other indices usually applied for characterizing aromatic properties

Objectives

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Conclusion