The synergistic cooperation of NH⋯O and CH⋯O hydrogen bonds in the structures of three new phosphoric triamides

<p>The supramolecular assemblies of three new phosphoric triamides, {(C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>)(CH<sub>3</sub>)N}<sub>2</sub>(4-CH<sub>3</sub>-C<sub>6</sub>H<sub>4</sub>C(O)NH)P(O) (<b>1</b>), {(C<sub>6</sub>H<sub>11</sub>)(CH<sub>3</sub>)N}<sub>2</sub>(4-CH<sub>3</sub>-C<sub>6</sub>H<sub>4</sub>C(O)NH)P(O) (<b>2</b>) and {(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>N}<sub>2</sub>(4-CH<sub>3</sub>-C<sub>6</sub>H<sub>4</sub>C(O)NH)P(O) (<b>3</b>) 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 <b>1, 2</b> and <b>3</b>, 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 <b>1, 2</b> and <b>3</b> are of the “resonance-assisted hydrogen bond” types and also the <i>anti</i>-cooperativity effect can be considered in the multi-acceptor sites P═O in <b>1</b> and <b>2</b> and C═O in <b>3</b>. 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.</p>