The nature of intramolecular hydrogen bond in Naphthazarin

• Published in: Chemical physics 2020-10, Vol.538, p.110907, Article 110907
• Main Authors: Afshar Ghahremani, Fatemeh, Zahedi-Tabrizi, Mansoureh, Faramarz Tayyari, Sayyed
• Format: Article
• Language: English
• Subjects: Barrier height; Naphthazarin; Proton tunneling frequency; Two-dimensional double- minimum potential
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2020.110907

[Display omitted] •We have introduced a 2D potential function for calculation the proton tunneling in Naphthazarin (NZ).•The reported potential function applied to calculate the vibrational frequencies of NZ by DFT method.•The nature of IHB illustrated by proton tunneling.•The barrier heights in the stepwise and concerted transfers were 65.3 and 127.3 kJ/mol at MP2/6-31G**-level, respectively. In this work, a feasible method has been introduced for investigating the proton tunneling frequency in Naphthazarin (NZ). A two-dimensional potential energy surface which couples OH stretching with in-plane bending modes has been computed for a firmed skeleton geometry, at the B3LYP/6-31G**, B3LYP/6-311G**, B3LYP/6-311++G** and MP2/6-31G** levels. This potential energy function is used to calculate the tunneling frequency, OH stretching, and in-plane bending frequencies. By calculations at the MP2/6-31G** level, the tunneling frequency of 15.3 and 0.9 cm−1 and the barrier height of 65.3 kJ/mol was obtained for light and deuterated NZ for the stepwise proton transfer, respectively. Also, the tunneling frequency of 0.8 and 0.0 cm−1 and the barrier height of 127.3 kJ/mol were obtained for the light and deuterated NZ for the concerted pathway, respectively. The obtained results indicate that both stepwise and concerted proton transfers pathways are probable.