A computational evidence of the intermolecular hydrogen bonding in leflunomide: Chemical shielding tensors

• Published in: Computational and theoretical chemistry 2023-03, Vol.1221, p.114027, Article 114027
• Main Authors: Ektefa, Fatemeh, Khodadadi, Zahra, Naderi, Fereshteh, Fathi, Fariba
• Format: Article
• Language: English
• Subjects: Chemical shielding tensors; CS tensor; Density functional theory; Hydrogen bonding; Intermolecular; Leflunomide
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2023.114027

[Display omitted] •The Shift of chemical shielding studied.•It alters for trimer.•It is stable for pentamer. A computational investigation has been performed without any symmetry constraints at the B3LYP/6-31++G** level for the evidencing of hydrogen bonding interactions in the real crystalline structure of Leflunomide (LFM) via chemical shielding (CS) tensors at the site of 14C, 17O, 15N, 1H nucleus. In this study, one molecule (monomer), three molecules (trimer), and five-molecules (cluster) of Leflunomide’s conformer have been modeled by accessible crystal coordinates. The CS tensors have been computed for 3 models of structure to indicate the effects of the hydrogen bonding interactions on the parameters of NMR. The evaluated NMR parameters of 14C, 17O, 15N, 1H nuclei of Leflunomide show specific tendencies from the monomer to the target molecule in the cluster as a result of the involvement in the intermolecular CO…HN type of hydrogen bonding interaction. Chemical shift of 14C, 17O, 15N, 1H nuclei significantly alter from monomer to the target molecule in trimer because of formation of inter-molecular CO…HN kind of the hydrogen bonding interaction whereas this alternation was insignificant via the target molecule in trimer to pentamer as a result of do not change numbers and types of the hydrogen bonding interactions.