Structure and vibrational assignment of bis(4-amino-3-penten-2-onato)nickel(II). A density functional theoretical study

► Ni(APO)2 is a nearly planar compound, whose HCCN dihedral angle has deviated from planar structure. ► According to the calculations, in the gas phase, trans configuration of Ni(APO)2 is more stable than cis configuration. ► The energy difference between the cis and trans isomers in solution is less than in the gas phase. ► The NH stretching frequency in the solid phase and CHCl3 solution appears at 3287, 3246 cm−1, respectively.