Evaluation of N–H···O hydrogen bond interactions in two new phosphoric triamides with a P(O)[NHCH(CH3)2]2 segment by means of topological (AIM) calculations, Hirshfeld surface analysis and 3D energy framework approach

Abstract

Abstract Two new phosphoric triamides having a common part XP(O)[NHCH(CH3)2]2, with X =[2,3,6-F3–C6H2C(O)NH] (1) and [C6H11(CH3)N] (2), were prepared and characterized by spectroscopic techniques (FT-IR and 1H-, 13C-, 31P-NMR) and single crystal X-ray diffraction. The asymmetric unit of 1 is composed of one molecule, whereas for 2 it consists of six symmetry independent molecules. In all molecules, the P atoms are in a distorted tetrahedral environment of one oxygen and three nitrogen atoms. The latter have mainly sp 2 character and a nearly planar environment. The crystal structures are stabilized via N–H · · · O hydrogen bond interactions, forming a linear arrangement for 1 and three independent parallel linear chains for 2, along the b and a axis, respectively. The intermolecular interactions in the molecular packing were analyzed using the Hirshfeld surface methodology, two-dimensional (2D) fingerprint plots and enrichment ratios (E). The prevalent interactions revealed by Hirshfeld surfaces are O · · · H type interactions for both structures 1 and 2, additionally C · · · O for 1 and H · · · H interactions for 2. The most favored contacts responsible for the molecular packing are C · · · F, N · · · H and O · · · H for 1 confirmed by E values greater than 1.30, whereas for 2, O · · · H and N · · · H intermolecular interactions with E values about 1.04 representing the favored contacts. Thus, the N–H · · · O hydrogen bond interactions are the dominant interactions in both compounds. For more details, a topological AIM analysis of N–H · · · O hydrogen bond interactions was performed: NCP–H · · · O=C hydrogen bond (the NCP is referred to the nitrogen atom within the C(O)NHP(O) segment) interactions in 1 are stronger than N–H · · · O=P interactions in both 1 and 2. Furthermore, a 3D topology of the molecular packing via the energy framework approach showed that the N–H · · · O hydrogen bond interactions in C(O)NHP(O)-based phosphoric triamide are predominantly electrostatic based, while they are electrostatic-dispersion based for other phosphoric triamides with a [N]P(O)[NH]2 skeleton.