Influence of O−H···OP Hydrogen Bonding on the Supramolecular Architectures of Phosphorus-Based Hydrazones: Alternate Right- and Left-Handed Fused Helical Chains Based on O−H···OP Hydrogen Bonds in the Crystal Structure of C₆H₅P(O)[N(CH₃)NCHC₆H₄-<i>p</i>-OH]₂

The acyclic phosphorus dihydrazone C6H5P(O)[N(CH3)NCHC6H4-p-OH]2 (1) forms an alternate right- and left-handed fused helical chain supramolecular structure in the solid state. The supramolecular architecture of 1 is formed as a result of intermolecular O−H···OP interactions. Variation in the position of the hydroxy group in C6H5P(O)[N(CH3)NCHC6H4-m-OH]2 (2) leads to the formation of a ladder structure, also mediated by O−H···OP interactions. In contrast to 1 and 2, C6H5[N(CH3)NCHC6H4-o-OH]2 (3), which contains an o-hydroxy group on the phenyl substituents, only shows C−H···O interactions. The absence of O−H···OP interactions in the latter is attributed to the involvement of the O−H unit in intramolecular O−H···N hydrogen bonding.