Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene

Patrycja Piękoś,Aneta Jezierska,Aleksander Filarowski,Alexander S Antonov,Eugene A Goremychkin,Jarosław J Panek,Peter M Tolstoy,Alexander F Pozharskii

doi:10.3390/sym12111924

Abstract

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

Highlights

In the last few years, considerable attention has been devoted to the symmetry of hydrogen bonding [1,2,3,4,5,6,7,8,9,10]
The first one refers to the Coulombic interaction between the nuclei and electronic densities of the monomers DMANH+
HSO4 −, with the assumption that these monomers are in their original electronic states, that is, DMANH+ is not perturbed by HSO4 − and vice versa

Summary

Introduction

In the last few years, considerable attention has been devoted to the symmetry of hydrogen bonding [1,2,3,4,5,6,7,8,9,10]. Hydrogen phthalate anions, and proton sponges have been studied intensively due to their physicochemical features that are derived from the presence of an intramolecular hydrogen bond [2,4,5,7,8,11,12,13,14]. The significance of proton sponges, the main object of the current study, is demonstrated by their high presence in the literature (e.g., [15,16,17,18,19,20,21]). The X-ray, neutron diffraction, incoherent inelastic neutron scattering (IINS), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR) methods of Limbach et al [22,23,24,25]

Objectives

Methods

Results

Conclusion