Single crystal structure, hydrogen bonding interaction, charge transfer and thermal properties of a new guanidine derivative crystal: Phosphate bis-guanidinoacetate

In order to understand deeply the interaction between guanidine and phosphate groups in crystal, phosphate bis-guanidinoacetate (PBGA) crystal was synthesized and grown by aqueous solvent evaporation method, which belongs to the triclinic crystallographic system, space group P-1, with unit cell parameters: a = 7.776 Å, b = 8.113 Å, c = 12.459 Å, α = 89.591°, β = 89.146°, γ = 61.370°, Z = 1. The crystal structure studies and vibrational spectral analysis showed that the special shift of C-N stretching vibration is caused by the hydrogen bonding interaction between phosphate and guanidine groups in crystal. Through quantum chemical calculation, we investigated the Independent Gradient Model, hydrogen bond energy (EHB) from Quantum Theory of Atoms in Molecules method, the atom dipole moment corrected Hirshfeld population, the electron density difference and electron localization function difference for PBGA dimer model, which provide deeper insight into the position, type, strength and charge transfer for the interaction between phosphate and guanidine groups. Thermal stability of the title crystal was evaluated by thermogravimetric and differential scanning calorimetry. Our results indicate that the rich electrostatic interaction between phosphate and guanidine groups has great impact on the structure, charge distribution and thermal stability of PBGA.