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The parent of porphyrins is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins. [1] With a total of 26 π-electrons, of which 18 π-electrons form a planar, continuous cycle, the porphyrin ring structure is often described as aromatic.
In coordination chemistry, a macrocyclic ligand is a macrocyclic ring having at least nine atoms (including all hetero atoms) and three or more donor sites that serve as ligands. [1] Crown ethers and porphyrins are prominent examples. Macrocyclic ligands often exhibit high affinity for metal ions, the macrocyclic effect.
The corrin ring resembles the porphyrin ring. [2] Both feature four pyrrole-like subunits organized into rings. Corrins have a central 15-membered C 11 N 4 ring whereas porphryins have an interior 16-membered C 12 N 4 ring. All four nitrogen centers are linked by conjugation structure, with alternating double and single bonds.
The general term protoporphyrin refers to porphine derivatives that have the outer hydrogen atoms in the four pyrrole rings replaced by other functional groups. The prefix proto often means 'first' in science nomenclature (such as carbon protoxide), hence Hans Fischer is thought to have coined the name protoporphyrin as the first class of porphyrins. [3]
These often have side groups that do not occur in nature, and possibly at the carbons in the methylene bridges (meso positions) instead of the pyrrole rings. The Meso-substituted porphyrinogens are intermediates in the so-called Lindsey synthesis of meso-substituted porphyrins. Oxidation turns the central hexahydroporphine core into a porphine ...
The molecule is a flat macrocycle, consisting of four pyrrole-like rings joined by four methine bridges, which makes it the simplest of the tetrapyrroles. [1] The nonpolar tetrapyrrolic ring structure of porphine means it is poorly soluble in most organic solvents and hardly water soluble. [2] As a result, porphine is mostly of theoretical ...
The porphyrin ring is a planar dianionic, tetradentate ligand. The iron is typically Fe 2+ or Fe 3+. One or two ligands are attached at the axial sites. The porphyrin ring has 4 nitrogen atoms that bind to the iron, leaving two other coordination positions of the iron available for bonding to the histidine of the protein and a divalent atom. [2]
Heme A (or haem A) is a heme, a coordination complex consisting of a macrocyclic ligand called a porphyrin, chelating an iron atom. Heme A is a biomolecule and is produced naturally by many organisms.