The interaction strength of intermolecular systems formed by NaH•••2(HF) and NaH•••4(HF): Hydrogen bonds, dihydrogen bonds and halogen-hydride bonds

In this paper, a theoretical study of the molecular properties of NaH center dot center dot center dot 2(HF) and NaH center dot center dot center dot 4(HF) complexes is reported. Based on MP2/6-311++G(d,p) calculations, the dihydrogen bonds (H center dot center dot center dot H), hydrogen bonds (F center dot center dot center dot H) and halogen-hydride bonds (F center dot center dot center dot Na) of these intermolecular systems were fully characterized. The characterization involved the following procedures: the examination of structural parameters, analysis of vibration modes such as frequencies shifted to red or blue in the infrared spectrum, modeling of the electronic topology, quantification of the cooperative energy followed by charge transfer and, finally, natural bond orbital analysis. The results show short intermolecular distances with high electronic density, while the stretch frequencies of the proton donors and acceptors are unusually shifted, and some values reach 1000 cm(-1). When all subunits of the complexes are taken into account, in this case the NaH and HF molecules, the high value for the strength of the H center dot center dot center dot H dihydrogen bond in NaH center dot center dot center dot 2(HF) suggests the formation of an additional subpart, i.e., the H-2 molecule. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.