Structural, electronic and energetic effects in heterocyclic fluorene derivatives fused with a fulvene unit

Publication date: Available online 22 April 2019Source: Computational and Theoretical ChemistryAuthor(s): Małgorzata Leszczyńska, Krzysztof EjsmontAbstractA set of 36 heterocyclic (B, N and O) fluorene (C) derivatives fused in nine ways with fulvene ring have been analyzed by means of different local aromaticity criteria. Molecular geometry of analyzed compounds were optimized at B3LYP/6-311++G(2d,2p) level of theory. The evaluation of the local aromaticity has been carried out through the use of the geometry-based harmonic oscillator model of aromaticity (HOMA) and the magnetism-based zz‐component of the nucleus independent chemical shifts calculated 1 Å above the ring center (NICS1zz) indices as well as one aromaticity index derived from the Quantum Theory Atoms in Molecules (QTAIM), i.e. the para-delocalization index (PDI). Additionally, the sum (H) of the kinetic (G) and potential (V) electron density energy in the ring critical points (RCPs) have been taken into consideration. These studies indicated that in 12 studied compounds the benzene ring fused with the fulvene loses its aromatic character. The fusion of heterocyclic fluorine derivatives with a fulvene ring significantly increases the energy of HOMOs and decreases the energy of LUMOs, which results in the energy gap reduction between the orbitals.Graphical abstract

Source: Computational and Theoretical Chemistry - April 23, 2019 Category: Chemistry Source Type: research