COMPUTATIONAL STUDY OF MN(II)-SALICYLALDEHYDE DINITROPHENYLHYDRAZINE AND MN(II)-VANILIN DINITROPHENYLHIDRAZINE STRUCTURES USING DFT METHOD

• Main Author: Zia Salma, Amalia
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/52145
• Institution: Institut Teknologi Bandung

Two Schiff base ligands have been synthesized in this study, namely salicylaldehyde 2,4-dinitrophenylhydrazine (SDPH) and vanillin 2,4-dinitrophenyl hydrazine (VDPH). The two compounds were obtained from the condensation reaction between the aldehyde and hydrazine derivatives. SDPH compounds was formed from the condensation reaction between salicylaldehyde (2-hydroxy benzaldehyde) and 2,4-dinitrophenylhydrazine, while VDPH compounds was formed from the condensation reaction between o-vanillin (2-hydroxy-3-methoxybenzaldehyde) and 2,4-dinitrophenylhydrazine. SDPH and VDPH compounds have been characterized by measuring the FTIR, 1H-NMR and 13C-NMR spectra. The formation of the Mn (II) complex with those ligands was studied computationally using the DFT (Density Functional Theory) method. The computational studies that have been carried out include: (i) optimisation of the tetrahedral complex [Mn(L)2] (L = SDPH or VDPH) structures, (ii) optimisation of the octahedral complex [Mn(L)2(H2O)2] structures with donor atoms O, N for each of these ligands in the trans- and cis- positions, with high spin and low spin states respectively, (iii) analysis of the stability of complex compounds based on data on changes in Gibbs free energy, (iv) analysis of coordination bonds between ions Mn(II) with ligands, and (v) analysis of ligand properties based on the natural charge of O and N donor atoms on the ligand through NPA (Natural Population Analysis) data and electron transfer between Mn (II) ions and ligands via NBO (Natural Bonding Orbital data) ). The complex structures of Mn (II) were optimized using the DFT computation method with the B3LYP functional and the 6-31G (D, P) basis set. The results of the calculation of Gibbs free energy change show that the most thermodynamically stable complex was the octahedral complex [Mn(L)2(H2O)2] with an O, N donor atom for each of these ligands in the trans-position in a high spin state. The coordination bond between the Mn (II) ion and the ligands is indicated by a shift in the wave number of the functional group ?C=N- in the infrared spectrum of the complex, which was compared to the infrared spectrum of the ligands. The results of the NPA analysis showed that the electron transfer occurred from the donor atom to the Mn(II) metal ion in the octahedral [Mn(L)2(H2O)2]. Then the NBO data showed that the SDPH and VDPH ligands had ?-donor and ?-acceptor characters. Furthermore, based on the electron transfer stabilization energy data (E(2)), the octahedral complex of [Mn(L)2(H2O)2] in the low spin state show a better electron transfer process than those in the high spin state.