In this experiment, students will synthesize a cobalt Schiff base complex with varying axial ligands ([Co(acacen)L2]+). They will characterize the complex using various techniques, and may perform computational modeling to predict spectroscopic properties.
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Students will be able to:
Synthesize a series of cobalt(III) complexes containing acetylacetonatoethylenediimine and ammine and imidazole derivatives.
Calculate the percent yield of the complexes synthesized.
Determine the steric and electronic effects of the axial ligands on the complex using UV-Vis spectroscopy.
Analyze multinuclear NMR spectra to determine the effect of axial ligands on the equatorial ligand.
Analyze the IR spectra to confirm the expected structure
Create a diagram that illustrates the effect of the axial ligands on the protons of the equatorial ligand.
Discuss the binding ability of the complex to biological molecules based on the primary literature.
Use Electronic Structure calculations at a minimum of the B3LYP/6-31G(d) level of theory using the PCM model for water to calculate the HOMO, LUMO, vibrational modes, NMR spectra, and UV-Vis spectra.
Compare calculated values to experimental spectra.
- Communicate their findings in written and/or oral format.
Standard glassware: Round bottom flask, Stir bar, Vacuum filtration system
Instrumentation: NMR, IR, UV-Vis
A computational package such as Gamess or Gaussian™ capable of electronic structure calculations, and a visualization package such as WebMO, GaussView™, Chem3D™, or Avogadro to visualize input and output files.
This lab lends itself to many adaptations:
1) The inorganic chemistry instructor can collaborate with the organic laboratory instructor in the synthesis of the Schift base ligands. The organic chemistry students will characterize the ligand using proton and carbon-13 NMR.
2) Each student or pair of students will synthesize the ammine and an imidazole derivative complex. Students will share the data to investigate effects of the trans ligands on the proton of the acacen ligand.
3) Co-NMR can also be used to investigate the properties of the trans ligand.