Calculation of Proton and Electron Affinity, Gas Phase Basicity and Ionization En ergy of N-Aminophethalimide

Proton affinity (PA) and ionization energy (IE) of molecules are important quantities in chemical andbiochemical studies. PA is calculated as the negative of the enthalpy change and Gas phase basicity(GPB) is defined as the negative of the Gibbs free energy change of the proton transfer reaction. Theionization energy and electron affinity can refer to vertical and adiabatic quantities. Vertical ionizationenergy (VIE) and vertical electron affinity (VEA) are calculated as electronic energy difference betweenthe ground state of the neutral molecule and its cation and anion at the equilibrium geometry of neutralmolecule, respectably. Adiabatic ionization energy (AIE) and adiabatic electron affinity (AEA) aredefined as the energy difference between neutral molecules and referred ions in their relaxed geometry [1].N-aminophthalimide (NAP), C8H6N2O2, is a useful intermediate for synthesizing organic compoundswhich have pharmaceutical activities. Also, it is employed in the aziridination of chiral N-enoyl sultams.It is also used in the synthesis of n-phthalimidoaziridines [2]. This substance is a precursor for synthesis ofother chemical compounds such as saccharin and anthranilic acid (2-aminobenzoic acid) and thalidomide[3]. In the present work we calculate the PA, GPB, VIE, AIE, VEA and AEA of N-aminophthalimide atthe B3LYP/6-311++G** level of theory with GAUSSIAN 09 computational package. NAP have severalsites to accept proton, so topical PA and topical GPB were reported. The geometry of the neutral anddifferent protonated NAP were optimized. The topical proton affinity (TPA) of NAP were calculated forprotonation of nitrogen, oxygen and carbons sites at 298 K. PA of this molecule changed from 701.42 to871.42 (kJ/mol) when it was protonated from C and O sites, respectively. In the most of the molecules,nitrogen atom is preferential site for protonation. In the case of NAP, oxygen atom accepts a proton easierthan nitrogen site. Also the GPB of NAP, changed from 671.21 to 837.91 (kJ/mol) when protontransferred to C and O sites. AEA and VEA of the molecule were obtained -1.22 and -0.86 (eV),respectively at B3LYP computational method. The values of AIE was calculated 8.04 (eV) and VIE wasobtained 9.49 eV.

Calculation of Proton and Electron Affinity, Gas Phase Basicity and Ionization En ergy of N-Aminophethalimide Keywords:

N-aminophthalimide , Proton Affinity , Gas Phase Basicity , Ionization Energy , Electron Affinity