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The magnitude of Δ o is determined by the field-strength of the ligand: strong field ligands, by definition, increase Δ o more than weak field ligands. Ligands can now be sorted according to the magnitude of Δ o (see the table below). This ordering of ligands is almost invariable for all metal ions and is called spectrochemical series.
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element.For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory.
As described above, π-donor ligands lead to a small Δ O and are called weak- or low-field ligands, whereas π-acceptor ligands lead to a large value of Δ O and are called strong- or high-field ligands. Ligands that are neither π-donor nor π-acceptor give a value of Δ O somewhere in-between.
In inorganic chemistry, the cis effect is defined as the labilization (or destabilization) of CO ligands that are cis to other ligands. CO is a well-known strong pi-accepting ligand in organometallic chemistry that will labilize in the cis position when adjacent to ligands due to steric and electronic effects.
Bitopic ligands target an orthosteric binding sites and allosteric binding sites on the same receptor. [13] In scientific research, bivalent ligands have been used to study receptor dimers and to investigate their properties. This class of ligands was pioneered by Philip S. Portoghese and coworkers while studying the opioid receptor system.
Examples of this type of ligand include CO, PR 3, NH 3, H 2 O, carbenes (=CRR'), and alkenes. Z-type ligands are those that accept two electrons from the metal center, as opposed to the donation occurring with the other two types of ligands. However, these ligands also form dative covalent bonds like the L-type. [2]
Cisplatin, PtCl 2 (NH 3) 2, is a coordination complex of platinum(II) with two chloride and two ammonia ligands.It is one of the most successful anticancer drugs. A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands ...
Strong-field ligands, such as CN − and CO, increase the Δ splitting and are more likely to be low-spin. Weak-field ligands, such as I − and Br − cause a smaller Δ splitting and are more likely to be high-spin. Some octahedral complexes exhibit spin crossover, where the high and low spin states exist in dynamic equilibrium.