Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Inorganic chemistry ↓


Coordination chemistry


Coordination chemistry is a fascinating and diverse field within inorganic chemistry that explores the behavior and characteristics of coordination compounds. These compounds are formed by the combination of ligands, which are ions or molecules that can donate electron pairs, and a central metal atom or ion. The study of coordination chemistry is important because these compounds have a multitude of applications in a variety of industries, including catalysis, medicine, and materials science.

Basic terminology and concepts

Before delving deeper into coordination chemistry, it is essential to understand some fundamental terms and concepts:

1. Ligands

Ligands are ions or molecules that have at least one electron pair that they can donate to the central metal atom or ion to form a coordination bond. Ligands can be classified based on the number of bonds they form with the central metal:

  • Monodentate ligands: These ligands donate one pair of electrons to the central atom. Examples include H2O and NH3.
  • Bidentate ligands: These ligands can form two bonds with the metal ion. An example of this is ethylenediamine (en).
  • Polydentate ligands: These ligands, also called chelating agents, can form multiple bonds. An example is ethylenediaminetetraacetate (EDTA).

2. Coordination number

The coordination number refers to the number of ligand donor atoms that are bonded to the central metal ion in the coordination complex. For example, if there are six NH3 ligands surrounding the cobalt ion in a complex, the coordination number is 6.

Metal Ligand Ligand

3. Complex ions and coordination complexes

A complex ion is a charged species consisting of a central metal ion bound to one or more ligands. A coordination complex, on the other hand, can be neutral or charged and consists of a complex ion and any counter ions that balance the charge, or in some cases, no counter ions.

4. Oxidation state

The oxidation state of the central metal atom or ion in a coordination compound indicates the number of electron pairs donated by the ligands and helps in understanding the electronic configuration and behaviour of the compound. It is calculated by considering the overall charge of the complex and the charges of the ligands.

Notable coordination compounds

The properties and applications of coordination compounds can vary greatly. Here are some examples:

  • Hexaamminenickel(II) chloride: The formula for this compound is [Ni(NH3)6]Cl2 The central metal, nickel, has a coordination number of 6, surrounded by six ammonia ligands.
  • Potassium ferricyanide: Represented by the formula K3[Fe(CN)6], it consists of Fe3+ ions surrounded by six cyanide ligands, with the potassium ions balancing the charge.

Structure and bonding in coordination compounds

Coordination compounds have diverse structures depending on the arrangement of ligands around the central metal ion. These structures play an important role in determining the properties of the compound.

1. Coordination geometry

The coordination geometry depends on the coordination number and electronic configuration of the metal ion. Common geometries include:

  • Linear: seen in coordination number 2, as in [Ag(NH3)2]+.
  • Tetrahedral: Common with coordination number 4, found in complexes such as [Ni(CO)4].
  • Square planar: Also common with coordination number 4, seen in [PtCl4]2-
  • Octahedral: the most common geometry for coordination number 6, for example, [Co(NH3)6]3+
Ligand Metal Ligand

2. Crystal field theory

Crystal field theory (CFT) explains the electronic structure of transition metal complexes. It describes how the presence of a ligand affects the energy levels of the metal d-orbitals, which split into different energy states under the influence of the ligand's electric field. This splitting pattern affects the colour, magnetism and stability of the complexes.

Spectroscopic and magnetic properties of coordination compounds

The interaction of coordination compounds with light and magnetic fields reveals important information about their structure and behavior.

1. Electronic spectra

Coordination compounds often display bright colours due to d-d electron transitions between split energy levels as a result of crystal field splitting. An example of this is the deep blue colour of [Cu(NH3)4]2+, where the electron transitions absorb certain wavelengths of light.

2. Magnetism

Compounds can be paramagnetic or diamagnetic depending on the arrangement of electrons in the split d-orbitals:

  • Paramagnetic: If unpaired electrons are present, as in [Fe(H2O)6]3+, the compound is attracted to a magnetic field.
  • Diamagnetic: If all the electrons are paired, as in [Cu(NH3)4]2+, it is repelled by a magnetic field.
M3+ Ligand

Applications of coordination compounds

Coordination compounds have wide applications in various fields. Here are some important examples:

1. Medicinal chemistry

In medicine, coordination compounds play important roles. For example, cis-platin, a platinum complex, is an important chemotherapy drug used in the treatment of cancer. It works by binding to DNA and inhibiting cell division.

2. Catalysis

Many industrial processes rely on coordination compounds as catalysts. An example of this is the use of [RhCl(PPh3)3] in the hydrogenation of alkenes.

3. Materials science

Coordination polymers and metal-organic frameworks (MOFs), which are networks formed by coordination bonds, are used in gas storage and separation due to their porous nature.

4. Colors and pigments

Coordination compounds are used to make dyes and pigments. The bright colors of compounds such as Prussian Blue are due to metal-to-ligand or d-d transitions.

Stability and reactivity of coordination compounds

The stability and reactivity of coordination compounds are affected by several factors:

1. Ligand field strength

The strength of the ligand field is determined by the electron donating ability of the ligand, which affects the energy gap between the split d-orbitals. CN- create a larger gap, making the complex stable.

2. Chelate effect

Chelating ligands, which form multiple bonds with the metal ion, increase stability due to entropy gain. For example, EDTA complexes are more stable than those formed by monodentate ligands.

3. Hard and soft acids and bases (HSAB) theory

According to the HSAB theory, hard acids prefer hard bases, while soft acids prefer soft bases. For example, Ag+ (soft acid) forms stable complexes with I- (soft base).

Conclusion

Coordination chemistry is a rich and dynamic field that is connected to many areas of science and technology. By understanding the structure, bonding, and properties of coordination compounds, we can better understand their role in the natural world and their applications in technology and industry. The breadth of coordination chemistry, from medallions in enzymes to brightly colored complexes in art, highlights its importance and its growing fascination for chemists and scientists around the world.


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Coordination chemistry

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