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Transition metal pyridine complexes encompass many coordination complexes that contain pyridine as a ligand. Most examples are mixed-ligand complexes. Most examples are mixed-ligand complexes. Many variants of pyridine are also known to coordinate to metal ions, such as the methylpyridines, quinolines, and more complex rings.
Pyridine-N-oxides bind to metals through the oxygen. According to X-ray crystallography, the M-O-N angle is approximately 130° in many of these complexes. As reflected by the pKa of 0.79 for C 5 H 5 NOH +, pyridine N-oxides are weakly basic ligands. Their complexes are generally high spin, hence they are kinetically labile.
Owing to its flammability, Anderson named the new substance pyridine, after Greek: πῦρ (pyr) meaning fire. The suffix idine was added in compliance with the chemical nomenclature, as in toluidine, to indicate a cyclic compound containing a nitrogen atom. [30] [31] The chemical structure of pyridine was determined decades after its discovery.
Pyridine-N-oxide is the heterocyclic compound with the formula C 5 H 5 NO. This colourless, hygroscopic solid is the product of the oxidation of pyridine. It was originally prepared using peroxyacids as the oxidising agent. The compound is used infrequently as an oxidizing reagent in organic synthesis. [1]
The direct amination of pyridine with sodium amide can take place in liquid ammonia or an aprotic solvent such as xylene is commonly used. Following the addition elimination mechanism first a nucleophilic NH 2 − is added while a hydride (H − ) is leaving.
Knowing the structure of a similar homologous sequence (for example a member of the same protein family) allows highly accurate prediction of the tertiary structure by homology modeling. If the full-length protein sequence is available, it is possible to estimate its general biophysical properties , such as its isoelectric point .
Diiminopyridines (DIP, also known a pyridine diimines, PDIs) are a class of diimine ligands. They featuring a pyridine nucleus with imine sidearms appended to the 2,6–positions. The three nitrogen centres bind metals in a tridentate fashion, forming pincer complexes .
The protein structure can be considered as a sequence of secondary structure elements, such as α helices and β sheets. In these secondary structures, regular patterns of H-bonds are formed between the main chain NH and CO groups of spatially neighboring amino acids, and the amino acids have similar Φ and ψ angles. [1]