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Waricha Watthanapha and
Rodolfo Herrera
Spectral Analysis of Molybdenum (II) Complexes
Molybdenum (II) complexes have properties that are unique among transition metals. They can form high coordination number (>6) organometallic compounds (metal-carbon bonds). In addition, these complexes are relatively air and water stable, and they have numerous electronic transitions in the Ultraviolet-Visible (UV-Vis) region.
The objective of the current research is to study the UV-Vis spectra of seven-coordinate Molybdenum (II) complexes, MoL7 2+ and MoL6X+, where: L = CNC(CH3)3 and X = Cl-, Br-, or I-. This is an area of interest since all three types of possible electronic transitions for metal complexes (metal → ligand, ligand → metal, and metal
d → d transitions) occur in the UV-Vis region at the same time. Analyzing these transitions (intensity, solvent effects, and wavelengths) of high coordination number metal complexes will add to the understanding of orbital energies, bonding, and structure.
The absorption spectra of the Molybdenum (II) complexes were analyzed in acetonitrile and methanol solutions. Concentrations studied range from 10-3 to 10 -5 M. A variety of concentrations was needed since the extinctions coefficients can vary from 10-50 (d → d) up to approximately 50,000 (metal → ligand and/or ligand → metal) depending on the nature of the transition. Peak assignments were tentatively identified within the range of these transitions, which occurs between 200-450 nm.
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