Theoretical and experimental study of nitrogen-rich compounds of biurea and 1-amino-biurea

The single crystal of 1-amino-biurea was obtained by slow evaporation method in solvent and its structure was determined using X-ray single crystal diffraction analysis. Based on the single crystal data of biurea and 1-amino-biurea, their charge distribution, natural bond orbit and molecular electrostatic potential were calculated to study their electronic structures and properties by DTF-B3LYP method with the cc-pVTZ basis set. Mulliken charge distribution data exhibits that O atoms have the most Mulliken charge of -0.3470e, followed by N(2A) and N(2) atoms (-0.2371e) in biurea, and O(1) atom (-0.3700e) has the most Mulliken charge, secondly O(2) atom (-0.3449e) and thirdly N(5) atom (-0.2399e) in 1-amino-biurea. Furthermore, the datas of NBO charge distribution and the molecular electrostatic potential show the same trend with that of Mulliken charge distribution. All the calculated results show that the O, N(2) and N(2A) atoms of biurea and O(1), O(2) and N(5) atoms of 1-amino-biurea are the most probable coordination site.