Instrumental lecture 6

Review Guidance for Research Papers

• Type of Paper:

  • Choose an actual research paper, not a review paper of research.

  • Aim for quality research that you can analyze and discuss.

• Canvas Notes:

  • Review guidance documents posted on Canvas for clarification and tips.

Exam Content Overview

• Exam Date:

  • Scheduled for next Thursday.

• Study Materials:

  • All content from the lectures leading up to the exam will be included.

  • Anything covered today will also be part of the exam material.

Topics of Study

• Organic Molecules:

  • Recap of previous discussions focused on the UV-Vis analysis of organic molecules.

• Metal Complexes:

  • Transition to discussion of metal complexes and organometallic chemistry.

  • Key Points:

    • Many metal complexes exhibit color due to electron transitions.

    • Focus on d orbitals where critical interactions occur.

Electron Transitions in Metal Complexes

• LMCT (Ligand to Metal Charge Transfer):

  • Electrons move from the ligand to the metal center.

• MLCT (Metal to Ligand Charge Transfer):

  • Electrons transition from d orbitals of the metal to molecular orbitals of the ligand.

Metal Complexes Examples

• Iron(II) in Porphyrins:

  • Used in hemoglobin, binds oxygen (O2).

  • Iron binds O2 through coordination in a porphyrin ring structure.

  • Absorbance noted at approximately 460 nm due to chromophores.

• Ruthenium Complexes:

  • Example of ruthenium trisbipyridine, studied for photophysics including fluorescence spectra.

  • This complex has significant implications in research and numerous publications exist.

Ligands in Metal Complexes

• Types of Ligands:

  • Monodentate:

    • Ligands forming a single bond to the metal.

  • Polydentate:

    • Ligands that can form multiple bonds.

    • Examples include bidentate (two bonds), tetradentate (four bonds), and hexadentate (six bonds).

• EDTA (Ethylenediaminetetraacetic Acid):

  • Functions as a hexadentate ligand with two amines and four carboxylic acid groups.

  • Utilized to form stable metal complexes.

Labile vs Inert Compounds

• Labile Ligands:

  • Ligands that can easily be replaced or removed.

• Inert Ligands:

  • Ligands that are more stable and have a slower rate of substitution.

Factors Affecting Labile/Inert Status

• Size of Metal Ion:

  • Smaller metal ions typically exhibit more inert properties.

• Metal Charge and Coordination:

  • Higher charges on metal centers often result in increased inertness.

• D Electron Configuration:

  • Configuration affects whether complexes are labile or inert, with certain configurations being more reactive.

Crystal Field Theory

• Energy Levels:

  • D orbitals split in energy when ligands coordinate with the metal center.

  • Splitting occurs due to interactions between the induced electric field of ligands and the d orbitals of the metal.

Splitting in Octahedral vs Tetrahedral Complexes

• Octahedral Complexes:

  • d orbitals split into two groups:

    • EG:

      • Higher energy (d x²-y², d z²).

    • T2G:

      • Lower energy (d xy, d xz, d yz).

• Tetrahedral Complexes:

  • Reverse splitting:

    • T2G orbitals are at higher energy, while EG are stabilized and at lower energy.

Spectrochemical Series

• Arrangement of Ligands:

  • Ligands are ranked based on their ability to influence d orbital splitting.

  • Weak field ligands such as iodide result in minimal splitting, while strong field ligands like CO cause significant splitting.

Selection Rules for Electronic Transitions

• Energy Selection Rule:

  • The energy of a photon must match the gap of transition for absorbance to occur.

• Spin Selection Rule:

  • The electronic transition cannot change the net spin multiplicity of the electrons.

Conclusion

• Review these topics thoroughly before the exam.

• Focus on understanding the interaction between ligands and metal centers, along with their implications on color and reactivity in coordination chemistry.