PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Inorganic chemistry → Coordination chemistry ↓


Electronic spectra of coordination compounds


Coordination compounds, also called complex compounds, have been a subject of great interest in the field of chemistry. The study of their electronic spectra is important as it provides information about their structural and electronic properties, which aids in understanding their behaviour in various chemical processes. The electronic spectra of these compounds arise from electronic transitions between different energy levels, mainly due to the presence of d-electrons in transition metal ions.

Basics of coordination compounds

Coordination compounds contain a central metal atom or ion that is bound to surrounding molecules or ions, called ligands. Metal-ligand bonding involves d-orbitals in transition metals, and these interactions lead to the formation of unique electronic structures.

Components of coordination compounds

  • Central metal ion or atom: Usually a transition metal, characterized by d-orbitals.
  • Ligands: Molecules or ions that donate electron pairs to the metal centre, forming coordination bonds.
  • Coordination number: The number of ligand donor atoms bonded to the central metal.

Understanding electronic spectra

Electronic spectra arise from the absorption of light, causing transitions of electrons within d-orbitals. In the context of coordination compounds, the most relevant transitions are:

  • D-D transition: Transition between d-orbitals of different energies due to crystal field splitting.
  • Charge transfer transition: It involves the transfer of electron between metal and ligand.

Key concepts

To understand the electronic spectra of coordination compounds, it is necessary to understand some key concepts, such as crystal field theory, ligand field theory and spectrochemical series.

Crystal field theory

Crystal field theory (CFT) describes the effect of the approach of the ligand to the metal ion in terms of electrostatic interactions. In an octahedral field, the approach of the ligand along the axes leads to repulsion of the metal d-orbitals and splitting into two groups:

    - t 2g: three orbitals (d xy, d xz, d yz)
    - e g: two orbitals (d z 2, d x 2 -y 2)
e.g. T2G

The difference in energy between these sets of orbitals corresponds to the crystal field splitting energy (Δ). When these absorption energies are in the visible region, the compound exhibits colours.

Ligand field theory

Ligand field theory is based on CFT and considers covalent interactions by incorporating molecular orbital theory. Metal-ligand bonds can have partial covalent character, which further affects the energy levels and observed spectra.

Spectrochemical series

The spectrochemical series arranges ligands based on their ability to split d-orbitals. Strong field ligands, such as CN - and CO cause larger splitting than weak field ligands, such as I - or Br - As a result, the color and absorption characteristics of coordination compounds vary considerably depending on the ligands present.

The spectrochemical series is represented as follows:

I - < Br - < S 2- < SCN - < Cl - < NO 3 - < F - < OH - < C 2 O 4 2- < H 2 O < NCS - < EDTA 4- < NH 3 < en < bipy < phen < NO 2 - < PPh 3 < CN - < CO

Interpretation of electronic spectra: An example

Let us consider the octahedral complex [Co(NH 3) 6] 3+. In this complex, we use electronic spectroscopy to determine the types of electronic transitions and the absorption wavelengths:

  1. dd transitions: In an octahedral field Co 3+ ion will undergo dd transitions. These transitions are often forbidden by selection rules, making them weak but observable.
  2. Charge Transfer: The charge transfer process may involve electron transfer from the ligand to the metal or vice versa, resulting in strong absorption.
Associate

Absorption of light causes excitation from lower energy t 2g orbitals to higher energy e g orbitals. This energy difference can be determined, giving information about the extent of orbital splitting and the nature of the ligands.

Applications and significance

The study of electronic spectra of coordination compounds has various applications in fields such as analytical chemistry, materials science and even medicine.

Analytical chemistry

The characteristic colors of coordination compounds can be used for analytical purposes, such as identifying transition metals or determining their concentrations in a sample using spectrophotometry.

Physics

Coordination compounds are used to develop new materials with unique electronic, magnetic, and optical properties. For example, they are important in the development of dyes and pigments as well as catalysts.

Medicine

The ability of coordination compounds to interact strongly with biological molecules makes them useful in pharmaceuticals. For example, some platinum complexes are used in the treatment of cancer.

Conclusion

Electronic spectra of coordination compounds provide in-depth information about their electronic structure and chemical behavior. By understanding the changes that occur, scientists can elucidate structural properties, predict reactivity, and apply these compounds in a variety of scientific and industrial contexts.

This exploration of electronic spectra not only advances our knowledge of coordination chemistry but also paves the way for advances in many scientific fields by taking advantage of the unique properties of these compounds.


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Electronic spectra of coordination compounds

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