Physico-Chemical nanomaterials science

Cyclic aromaticity in p-conjugated nanomaterials within quasi-correlated tight-binding model
Luzanov A.V.1
1 State Scientific Institution “Institute for Single Crystals”, Natl.Acad. of Sci. of Ukraine. 1, Nauky av 60.,UA-61001, Kharkiv, Ukraine.
E-mail: avluzanov@gmail.com

We discuss how to measure aromaticity in large polycyclic aromatic hydrocarbons and related nanographenes by unsophisticated molecular orbital techniques. The focus is placed on local aromaticity measures associated with individual benzenoid rings. In the latter, cyclic delocalization is the underlying feature, which serves as a principal characteristic of aromaticity at all. Unfortunately, many existing aromaticity scales, particularly, magnetic ones, can lead to results that are not consistent with chemical expectations. We revise the ring aromaticity index (RAI) from Ref. [1] and include net charge and electron unpairing effects into RAI. The previously introduced quasi-correlated tight-binding approximation [2] serves us as an easily available model for taking account of electron correlations which become essential in large conjugated systems. It allowed us to investigate large open-shell systems which are electronically of biradicaloid or polyradical nature The application are given for various classes of unsaturated nanosized carbon-containing structures (graphene nanoflakes, triangulene polyradicals and others).

1.	Cioslowski J., Matito E., Sola M. Properties of Aromaticity Indices Based on the One-Electron Density Matrix // J. Phys. Chem. A-2007.-111, N 28.-P. 6521-6525.
2.	Luzanov A. V. Effectively Unpaired Electrons for Singlet States: From Diatomics to Graphene Nanoclusters // in Practical Aspects of Comput. Chemistry IV (Springer US, Boston, MA, 2016), PP. 151–206.