Synthesis of new α-amino-1H indazolyl-phosphonate derivatives: Crystal structure, Hirshfeld surface analysis and DFT studies

Abstract

A new α-amino-1H Indazolyl-phosphonates derivative 3a–e were synthesized and subjected to solid state characterization by single-crystal X-ray diffraction analysis, and to study their NMR and Hirshfeld surface analysis. The P atom exhibits tetrahedral geometry involving two O-ethyl groups, a C atom and a double-bonded O atom. The P–C bond has an approximately staggered conformation, with the aniline and substituted groups in gauche positions with respect to the PO double bond. The molecules are arranged as centrosymmetric or pseudocentrosymmetric dimers connected by two N–H⋯OP hydrogen bonds and also by C–H … π interaction in the case of structures 3a–e, which are responsible for the formation and stability of the molecular assemblies. Hirshfeld surface analysis (dnorm surface and two-dimensional (2D) fingerprint plots) revealed the nature of intermolecular contacts. The most important contributions for the crystal packing are from H⋯H, H⋯C/C⋯H, O⋯H/H⋯O, and H⋯N/N⋯H interactions. In addition, frontier molecular orbitals and Molecular Electrostatic Potential map of the compounds was produced by using the optimized structures.