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Chemical Equilibrium
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
The region surrounding the central atom or ion and its ligands is called the coordination sphere. The coordination number is the total number of points at which the central atom or ion attaches to its ligands. Both [Co(NH3)6]3+ and [CoCl(NH3)5]2+ have coordination numbers of 6. The most common coordination numbers observed in complex ions are 2, 4, and 6. If the complex carries a net electric charge, as the two examples given here do, it is called a complex ion. If it is electrically neutral, it is referred to as a coordination compound. An example of a coordination compound is [Co(NH3)6]Cl3.
Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What are the two main approaches for using cantilevers in biosensing?By immobilizing a ligand on one side of the cantilever and placing it in contact with a receptor in solution, the cantilever bends in response to a change in surface stress generated by ligand-receptor binding; the greater the binding energy, the greater the bending. A ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bending causes movement of the cantilever tip of the order of 1–100 nm.Furthermore, the resonance frequency of a microcantilever varies sensitively with molecular adsorption. In the dynamic or resonance mode, cantilevers are excited close to their resonance frequency, which is typically in the kHz or even MHz range. When an additional mass is attached to the oscillating cantilever, its resonance frequency changes (adding a mass lowers the resonance frequency). This is not surprising since, at a first approximation, cantilevers behave like a harmonic oscillator, an ideal oscillating spring-mass system.
Metal Exposure and Toxic Responses
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
Chelation is the formation of a metal ion complex in which the metal ion is associated with one or more electron donors referred to as a ligand. The ligand may be monodentate, bidentate, or multidentate (i.e., it may attach or coordinate using one or two or more donor atoms). Bidentate ligands form ring structures that include the metal ion and the two ligand atoms that are attached to the metal. The donor molecule is properly referred to as a chelating agent. This term is derived from the Greek chela, for claw.
pH-dependent two Cd(II) coordination architectures with methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate and 1,3-bis(4-pyridyl)propane mixed ligands: syntheses, crystal structures, and photoluminescent properties
Published in Journal of Sulfur Chemistry, 2020
In recent few decades, Sulfur-containing coordination polymers (CPs) are of high interest due to their fascinating topologies and desirable properties [1–7]. However, the controllable synthesis of these materials is a great challenge because intrinsic and external factors play a critical role in their self-assembly, such as the ligands chosen, the coordination geometry of central metal, reaction temperature, counterions, solvent, pH value, reaction time, metal-to-ligand ratio and other possible influences [8–13]. Among them, the pH value of the reaction systems is especially important by changing the coordination of central metal ions and the deprotonation of organic ligands. At present, many CPs with distinct structures were synthesized based on the assembly of the same metal ions and organic ligands under different pH values [14–17].
Synthesis and characterization of new ruthenium(III) complexes derived from fluoreneamine-based Schiff base ligands and their catalytic activity in transfer hydrogenation of ketones
Published in Journal of Coordination Chemistry, 2020
Veerasamy Nagalakshmi, Raja Nandhini, Galmari Venkatachalam, Kasturi Balasubramani
Schiff base ligands, considered as privileged ligands and attractive due to their stability and the ease by which modified variations can be obtained, are once again topical in connection with a diverse range of applications such as organic synthesis [1, 2]. For several reasons, Schiff bases have been found to be among the most convenient and attractive ligands for ruthenium complexes [3–7]. Schiff base ligands have been used extensively in coordination chemistry to build complexes with transition and main group metals. The proper choice of ligands is key in manipulating the activity and selectivity of catalysts. Steric and electronic effects around the metal center can be finely adjusted through an appropriate selection of the Schiff base ligands. Experimental data suggests that the steric bulk of the Schiff base has a greater impact on catalytic performance compared to the electronic influence of Schiff base ligands [8]. The two donor atoms O,N in the ligated Schiff base exert opposite electronic effects, thus a flexible interplay between these two binding sites can be achieved and it triggers catalytic activity. Schiff base complexes of transition metals [9] having O,N-donor atoms have shown an exponential increase as inorganic catalysts for various organic transformations.
Review: Schiff base metal complexes as anti-inflammatory agents
Published in Journal of Coordination Chemistry, 2023
Qurat-Ul-Ain Sandhu, Muhammad Pervaiz, Abdul Majid, Umer Younas, Zohaib Saeed, Adnan Ashraf, Rana Rashad Mahmood Khan, Sami Ullah, Faisal Ali, Seemal Jelani
Ligands are building blocks in coordination chemistry, acting as functional groups that bind to metal ions to produce complexes. Generally, ligands are donor atoms that donate pairs of electrons to the metal ion, behaving as Lewis bases. Ligands like nalidixic acid, cinoxacin, 2-guanidinobenzimidazole and N-carboxymethylpseudoephedrine provide electrons towards central metal ion and show biological activities [1]. Schiff bases (SB) were discovered in 1864 by Hugo Schiff by a condensation process. Schiff bases are the condensation product of carbonyl compounds, including aldehydes/ketones and primary amines as shown in Figure 1 [3, 4]. SB, comprising an imine or azomethine functional group (–C = N–), are utilized in the development of other compounds.