Bifurcated hydrogen bonds in crystal structures of new phosphorochromone derivatives

The crystal and molecular structures of three new phosphorochromones determined by the X-ray diffraction method are presented. For all crystal structures, a similar pattern of centrosymmetric dimer is formed for which bifurcated hydrogen bonds exist with bifurcated acceptor 0...(H-N, H-C). For one of the crystal structures, there is additionally the intramolecular resonance-assisted H bond. The analysis of those interactions is performed in terms of their geometries and strengths. Additional calculations on simple model systems are performed to study the nature of bifurcated H bonds. The wave functions are applied for further analysis based on the Bader theory.