The synergistic cooperation of NH⋯O and CH⋯O hydrogen bonds in the structures of three new phosphoric triamides
The supramolecular assemblies of three new phosphoric triamides, {(C6H5CH2)(CH3)N}2(4-CH3-C6H4C(O)NH)P(O) (1), {(C6H11)(CH3)N}2(4-CH3-C6H4C(O)NH)P(O) (2) and {(C2H5)2N}2(4-CH3-C6H4C(O)NH)P(O) (3) were studied by single crystal X-ray diffraction as well as by Hirshfeld surface analysis. It was found that a synergistic cooperation of NH⋯O and CH⋯O hydrogen bonds occurs in all three structures, but forming unique supramolecular architectures individually. Along with the presence of centrosymmetric dimers in 1, 2 and 3, based on a classical NH⋯O hydrogen bond, the presence of weak CH⋯O interactions play an additional and vital role in crystal architecture and construction of the final assemblies, collectively identified as a centrosymmetric dimer (0D), a 1-D array and a 3-D network, respectively. These differences in superstructures are related to the effect of aromatic, bulk and flexible groups used in the molecules designed, with a similar C(O)NHP(O) backbone. The NH⋯O contacts in 1, 2 and 3 are of the “resonance-assisted hydrogen bond” types and also the anti-cooperativity effect can be considered in the multi-acceptor sites P═O in 1 and 2 and C═O in 3. All three compounds were further studied by 1D NMR experiments, 2D NMR techniques (HMQC and HMBC (H–C correlation)), high resolution ESI–MS, EI–MS spectrometry and IR spectroscopy methods.
