The Electron Distribution in the Nonlinear Optical Material 2-Amino-5-Nitropyridinium Dihydrogen Phosphate

The topological analysis of the 2-amino-5-nitropyridinium dihydrogen phosphate, 2A5NPDP, and the experimental electron density distribution determined from X-ray diffraction data interpreted in terms of the Hansen & Coppens pseudoatom formalism [1] is presented. The bond critical point properties of the total experimental electron density agree fairly well with ab initio Hartree-Fock calculations for the isolated ions. The analysis of the hydrogen-bond critical points shows the crystal H-bond framework to involve four anions and one cation. All the H-bond critical points show small positive ∇2ρ(r) values, consistent with ionic closed-shell interactions between the participant atoms.