Low-spin, mononuclear, Fe(III) complexes with P,N donor hemilabile ligands: A combined experimental and theoretical study |
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Authors: | Pankaj Das Podma Pollov Sarmah Ashwini K Phukan |
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Institution: | a Department of Chemistry, Dibrugarh University, Dibrugarh 786 004, Assam, India b Department of Chemical Sciences, Tezpur University, Napaam, Assam, India |
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Abstract: | Two new mononuclear Fe(III) complexes, FeCl3{PPh2(p-C6H4NMe2)-P}3](1) (PPh2(p-C6H4NMe2): 4-(dimethylamino)phenyldiphenylphosphine) and FeCl3(PPh2py-P)(PPh2py-P,N)] (2) (PPh2py: diphenyl(2-pyridyl)phosphine) were synthesized by reacting anhydrous FeCl3 with respective ligand in acetonitrile solution under refluxing condition. Both the complexes were characterized by elemental analysis, FAB-Mass, FTIR, UV-Vis, ESR, Cyclic Voltammetry and magnetic measurement. The FAB mass spectra of complexes 1 and 2 show molecular ion peak at m/z 1078 M]+ and m/z 687 M−1]+, respectively, indicating mononuclear nature of the complexes. UV-Vis spectra of the complexes were consistent with low-spin, octahedral geometry. The variable temperature magnetic susceptibility measurement (73-323 K) of these complexes is also consistent with the paramagnetic nature of the complexes with a ground state spin S = ½. The Fe(III) centers of these two complexes remain low-spin, both at room temperature and liquid nitrogen temperature, was also indicated by the ESR analysis. Cyclic Voltammetry of both the complexes show an irreversible oxidation wave attributed to Fe3+ → Fe4+ + e− along with the peak for ligand oxidation. Theoretical calculations (B3LYP) of the complexes show that for complex 1, a trans geometry of the two phosphorous atoms and for complex 2, a mer,cis structures are the most favored geometrical isomer. TDDFT calculations were performed to interpret the observed bands in the UV-Visible spectra. |
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Keywords: | Fe(III) complexes Low-spin Hemilabile ligand Magnetic study DFT calculation |
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