Author: Mishal Hayat

Coordination complexes

Compounds having one central metal attached to the ligand through coordinate covalent bond is known as coordination compounds. Ligand may be atoms, ions or molecules having lone pair which is donated to the central metal in complex. Transition metals has a specialty of vacant d orbital, due to this empty orbital it can accommodate many changes and has a wide spread applications in different fields. It may be used as catalysts, in medicinal field, material science, environmental remediation, nano technology etc.

TYPES OF COORDINATION COMPLEXE

Perfect or Penetrating Complex

In a perfect complex, the complex ion is either completely stable, that is, undissociated or is very feebly dissociated in solution. For example:

K₄ [Fe(CN)₆] → 4K⁺ + [Fe(CN)₆]^4-  ⇌ Fe²⁺ + 6CN^–

Imperfect or Normal Complex

In an imperfect complex, the complex ion is either less stable or dissociates appreciably. For example:

K₂ [Cd(CN)₄ ] → 2K⁺  + [Cd(CN)₄] ^2– ⇌ Cd²⁺ + 4CN ^–

Ligands

►The molecules and ions that surround the metal ion in a complex are known as ligands or complexing agents.

►An atom or group of atoms which bind to the central metal atom or ion through lone pair of electrons present on its donor atom.

►Depending on number of pairs donated by different atoms, it is of following types.

PREPARATION OF COMPLEXE

By Substitution Reactions

Substitution reaction means to replace ligands in a reactant they may occur through associative, dissociative or interchange mechanism.

[Cu(H₂O)SO₄+4NH₃→[Cu(NH₃ )₄ SO₄+4H₂O]

By Direct Combinations

In direct combination complexes refer to reaction between different ligands or other complexes to form a new complex. In this type of reaction metal center or ligand is involve some time both take part in reaction.

PtCl₄ + 2KCl → K₂ [PtCl₆ ]

By Redox Reactions

Change in oxidation number of the metal complexes occur, it may outer electron sphere or inner electron sphere

CoCl₂ + 2NH₄ Cl + 10 NH₃ + H₂O₂ → 2[Co (NH₃) ₆ ] Cl₃ + 2H₂O

Applications

Our environment is facing many challenges including climate change, pollution from industries to air as well as to water etc., for all these problems coordination compounds play a vital role in heavy metal removal, air purification, biodegradation, sensing and detection, and many more.

 Heavy metal removal

industrial waste water is a key issue for most of the aquatic life to resolve this issue coordination complexes play a vital role. As discuss above complexes is of two type one is labile other is stable these heavy metals are attached to the ligands it may be strong or weak field ligand, and through attachment it may remove from the water. When heavy metals such as Ni(II), Cr(III), Cu(II), Hg(II), Cd(II) and Pb(II) bind to the ligand(s), the environmental fate and toxicity of heavy metals can be significantly influenced. Different separation techniques were then perform including ion exchange adsorption membrane filtration etc.,

Air purification

some of MOFs (metal organic framework), zeolites, polymeric coordination, metal oxide are used for air purification. Particulate matter, VOC heavy metals etc., are forming a stable complex through adsorption, absorption or catalytic oxidation. These process are highly selective, low cost and efficient.

Sensing and detection

some of coordination complexes may also used in various sensing and detecting platforms, they detect gases like O2 CO NO etc., biomolecules for example DNA, RNA, glucose etc.,  it may also detect some ions including Na+ k+ ca+ etc., PH sensing, fluorescence sensing, electrochemical sensing, magnetic sensing etc.

Also read: Molarity Calculations

Follow Us on

FACEBOOK

INSTAGRAM

YOUTUBE

The post Coordination complexes as an influential tool for environmental remediation appeared first on IM Group Of Researchers - An International Research Organization.