Competition between intramolecular hydrogen and pnictogen bonds in protonated systems

The online version of this article (doi:10.1007/s00214-016-1895-8) contains supplementary material, which is available to authorized users.A theoretical study of the competition between hydrogen (HB) and pnictogen bonds (ZB) in three different families of compounds, (Z)-1,2-disubstituted ethenes (Eth), 1,2-disubstituted benzenes (Phe) and 1,8-disubstituted naphthalenes (Naph), with a charged group, ZH and a neutral one, Z′H (Z, Z′ = N, P, As) as interacting moieties, has been carried out. In those structures with a NH motif, intramolecular hydrogen bond structures are minima while pnictogen interactions are transition states. The opposite is true for PH and AsH moieties. An analysis of isodesmic energies (E), interaction energies (E) and deformation energies (E) shows that in Eth derivatives, the most stable compound corresponds to P–N ZB while in the Phe and Naph ones, the N–N HB interaction presents the largest negative isodesmic energy. Also, Eth and Phe derivatives show negative E values for all the compounds under study; however, in some cases of Naph derivatives positive isodesmic energies have been found. The Atoms in Molecules (AIM) analysis of the electron density, natural bond orbital (NBO) second-order orbital energies and electron density shift maps (EDS) have been used to better understand these intramolecular interactions.We thank the Ministerio de Ciencia e Innovación (Project No. CTQ2015-63997-C2-2-P) and the Comunidad Autónoma de Madrid (Project FOTOCARBON, ref S2013/MIT-2841) for continuous support. Thanks are given to the CTI (CSIC), Irish Centre for High-End Computing (ICHEC) and the Trinity Center for High- Performance Computing (TCHPC) for the provision of computational facilities. G.S.-S. wants to thank to Human Frontier Science Program (Project Reference: LT001022/2013-C) for the supportPeer Reviewe