This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016 New J. Chem. Cite this: DOI: 10.1039/c5nj03573b On the role of heteroatoms in aromatic rings. Insights from 10p main group elements heterorings [(EH) 2 S 2 N 4 ] q (E = C, P, B, Si, Al and q = 0, À2)† Anastasios G. Papadopoulos, a Nickolas D. Charistos* a and Alvaro Mun ˜ oz-Castro* b Inclusion of heteroatoms into a ring skeleton obtained unique electronic features, which differ from the respective isoelectronic organic counterparts, increasing the versatility of aromatic molecules. Herein, we evaluate the role of heteroatoms on the electronic and magnetic properties in a number of inorganic 10p-electron eight-member aromatic rings involving the isoelectronic [(EH) 2 S 2 N 4 ] q (E = C, P, B, Si, Al) series using density functional methods. The inclusion of different heteroatoms with increasing electronegativity increased the aromatic behavior in relation to the representative 10p-electron [C 8 H 8 ] 2À organic ring. A deeper analysis on the magnetic response to an applied magnetic field, in terms of individual p-orbitals contributions, revealed that the differentiation in aromaticity originates from orbitals with major contributions from p z of heteroatom E, whereas the diatropic contributions that arise from the S 2 N 4 core remained similar throughout the series. Therefore, the effect of including a certain type of heteroatom can be addressed in terms of the variation and contribution of each individual p-orbital, starting from the respective organic counterpart, which appears to be a convenient approach. The similar p-aromatic character observed suggests the proposed hypothetical rings are feasible structures to explore synthetically. The less aromatic counterpart given by the Al counterpart should lead to a less stable ring in this series. 1. Introduction Because the Kekule ´’s seminal study on the rationalization of benzene structure involving conjugated single and double bonds within the ring, 1 aromatic molecules continue to attract the interest of the scientific community. An indubitable char- acteristic behavior of such systems is the capacity to exhibit a free p-electron precession under an external applied magnetic field, leading to ring current effects. 2 Heterocyclic rings isoelectronic to benzene have been known for many years, wherein a vast variety of fully conjugated heterocycles has been widely recognized. 3–13 The inclusion of main-group elements into the ring skeleton provides interesting modifications in comparison to regular hydrocarbon structures, improving their stability towards oxidation and the possibility to control intermolecular aggregation, among other properties, 6–13 which are of particular interest towards the development of novel functional materials. A recent review on structure, bonding and aromatic properties of heterocyclic rings is available in the literature. 14 In particular, the synthesis of heterocycles involving sulphur and nitrogen atoms has continued to play an important and often pioneering role in molecular materials, which is encouraged by the initial discovery of the metallic and superconducting properties of polysulphur nitrides (SN) x . 15–18 The conducting behavior arises as a consequence of its polymeric nature, with extensive p-delocalization of electrons along each SN chain. Attempts to include a carbon atom into the structural skeleton in pursuit of interesting electron-rich C/N/S based rings 19–24 to synthesize, for example, 1,5,2,4,6,8-dithiatetrazocine, which has been recently reported 22 and described as a ‘‘hybrid’’ aromatic molecule. In heterocyclic chemistry, aromaticity assumes fundamental importance not only as a qualitative concept, but also for its quantitative aspects, wherein electron count schemes allow for a Aristotle University of Thessaloniki, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54 124, Greece. E-mail: nicharis@chem.auth.gr b Grupo de Quı ´mica Inorga ´nica y Materiales Moleculares, Universidad Autonoma de Chile, El Llano Subercaseaux 2801, Santiago, Chile. E-mail: alvaro.munoz@uautonoma.cl † Electronic supplementary information (ESI) available: Analysis of the contributions from core-, s- and p-subsets of electrons to the overall magnetic response. Analysis based on the GIAO components contributions. Choice of origin for magnetic response properties. A deeper analysis of the 1 H chemical shift tensor. See DOI: 10.1039/c5nj03573b Received (in Victoria, Australia) 18th December 2015, Accepted 29th March 2016 DOI: 10.1039/c5nj03573b www.rsc.org/njc NJC PAPER Published on 29 March 2016. Downloaded by University of California - San Diego on 12/04/2016 10:35:41. View Article Online View Journal