The first C(O)NHP(O)-based phosphoric triamide structure with an N‒H···π hydrogen bonding: A combination of X-ray crystallography and theoretical study to evaluate the strength of hydrogen bonds

Abstract

GRAPHICAL ABSTRACT ABSTRACT The hydrogen bond pattern of N-(4-methoxybenzoyl)-N′,N″-bis(4-methylbenzyl)-phosphoric triamide, C24H28N3O3P, (I), was investigated. In the crystal structure, the molecules are aggregated through NCP―H···O═P and NP―H···O═C hydrogen bonds in a one-dimensional arrangement parallel to the c axis (NCP is the nitrogen atom in the C(O)NHP(O) segment and NP stands for the two other nitrogen atoms bonded to the P atom). There is also a novel NP‒H···π hydrogen bond in the crystal which extends the aggregation of the molecules to a two-dimensional array parallel to the bc plane. A Cambridge Structural Database (CSD, version 5.37, Feb 2016) analysis shows that the N―H···π hydrogen bond was not observed in any of 156 [RC(O)NH]P(O)[NR1R2]2 (R1 ≠ H, R2 = H or ≠ H) phosphoric triamide structures reported so far. The theoretical calculations at the B3LYP/6-311G** level of theory (DFT, AIM, and NBO) were performed to evaluate the strengths of NCP―H···O═P, NP―H···O═C and NP―H···π hydrogen bonds, considering two-aggregate molecular assemblies containing these hydrogen bonds. The calculations on the title compound suggest that the intermolecular NCP―H···O═P hydrogen bond is stronger than NP―H···O═C and NP―H···π interactions. The hydrogen bond strength was investigated by NBO, topological analysis, geometry calculation, Hirshfeld surface analysis and experimental spectroscopic results, which are in agreement with each other.