Porphyrin nomenclature

For a thorough exposition of porphyrin nomenclature, see. Pure Appl. Ghent., (1987), 59,779. 

Porphyrins are formally derived from the porphin (1) nucleus by substitution of some or all peripheral positions with various side chains. In the classical system of nomenclature T, introduced by H. Fischer,Sc the peripheral /5-pyrrolic positions are numbered front 1 to 8 and the methine positions (also named meso positions) between the pyrrole rings are designated a, //, y, and 5. The rings are lettered clockwise A, B, C, and D. The classical nomenclature was in the past more and more displaced by a nomenclature which numbers all the carbon... 

Chlorophyll a, the green photosynthesis pigment, is the prototype of the chlorin (2,3-dihydro-porphyrin) class of products. It was first isolated by Willstatter1 at the turn of the century. The common structural unit in this class is the chlorin framework named after chlorophyll. The chromophore with a partially saturated pyrrole ring, which is formally derived from the completely unsaturated porphyrin, is less symmetric than the latter and systematically named according to IUPAC nomenclature as 2,3-dihydroporphyrin. 

The bacterioehlorin structural-type is formally derived from porphyrin by saturation of two peripheral C —C double bonds in oppposite pyrrole rings and therefore systematically named according to IUPAC nomenclature as 7,8,17,18-tetrahydroporphyrin. 

The concept of expansion of the porphyrin macrocycle by formally inserting additional carbon atoms between the pyrrole rings was first considered and synthetically realized by LeGoff/ He also suggested a nomenclature for these macrocyclic systems using the word platyrin which... 

Although it is just 50 years since Treibs obtained vanadyl deoxophylloerythroetioporphyrin, the major metalloporphyrin in petroleum and shales,145 it is only relatively recently that Tsutsui obtained the first titanium porphyrin, (meso-DME)Ti=0.146 A review of this general area is available 147 the nomenclature is given in Table 7. 

It is unfortunate that two systems of nomenclature are currently being used in this area. Though this author, like most in the United States, has a personal preference for the Fischer system (11) (because it retains a link with the monumental body of earlier work), the IUPAC system (12) is mandated in this chapter. To be sure, the IUPAC system has its advantages, not the least of which is the correlation of atoms between the porphyrin (12) and corrin (13) chromophore. 

In the IUPAC system, the four methine positions are conveniently numbered 5, 10, 15 and 20, and the eight remaining peripheral positions fall at 2, 3, 7, 8, 12, 13, 17 and 18. The nitrogen atoms are numbered 21 through 24. Owing to the continued use of trivial names, both in the IUPAC and classical systems of nomenclature, certain other features of porphyrin notation and isomerism need to be explained. If the eight peripheral substituents are made up of two sets of four (for example, four methyls and four ethyls), and if there is one of each on the individual pyrrole subunits (a situation which usually occurs in biologically derived porphyrins), then there are four possible so-called primary type isomers. These four isomers for the methyl/ethyl series, trivially named etioporphyrins, are shown in Scheme 1 the compounds are named etioporphyrin-I (14), etioporphyrin-II (15), etioporphyrin-III (16), and etioporphyrin-IV (17). 

Nomenclature, Abbreviations, and Coordination Chemistry of Metal Porphyrinates... 

This nomenclature procedure parallels that normally used for porphyrins, which is based on the compound with the highest level of unsaturation known thus the porphyrin is the parent compound and the related reduced structures are named hydroporphyrins. 

The nomenclature of porphyrins, which belong to the larger class of tetrapyrrole compounds, is sometimes obscured by historical remnants (e.g. chlorin which does not contain any chlorine substituent, see H22c in fig. 10, or 2,4-di(o -methoxyethyl)-deuteroporphyrin for TMb, see fig. 11 below). IUPAC has published nomenclature rules in 19863 and the numbering adopted for the ring is given in fig. 10. The 5, 10, 15, and 20 positions are commonly referred to as meso positions the roman number after a name (I though IV) denotes the relative positions of substituents a and b. 

Nomenclature of Samples. The nomenclature used to describe various samples and treatments has been outlined in detail elsewhere (8). In this study, EuYV(p)AAACS means that EuY has been loaded with 1.0 wt % vanadium porphyrin (p), then mixed with the AAA-alumina (AAA), calcined (C) and subsequently steamed (S). Naphthenate precursor will be labeled n. 

Nomenclature follows IUPAC recommendations (79PAC2251). The basic macrocyclic system I is named porphyrin, which implies that the pyrrolic nitrogen atoms are placed in positions-21 and -23, regardless of the structure of the actual tautomer. Hydro prefixes are then considered in ascending numerical order. I attempt here to maintain the arrangements of the formulas of hydroporphyrins resulting from these rules. 

Throughout this book an effort has been made to use both the original authors trivial names as well as designations based on a Franck-type approach. Since the rationale for using this latter systematic nomenclature is to allow for easy inter-comparisons between classes of molecules, a formal definition is appropriate here. For a given macrocycle, the number of pyrrole or pyrrole-like substituents is first determined and the system designated as being a porphyrin (four subunits), pentaphyrin (five subunits), hexaphyrin (six subunits), etc., as warranted. This compound name is then preeeded by a number (in brackets) that indieates the... 

Analysis of the products indicated that these new macrocycles consisted of six pyrrolic subunits linked in a (1.1.1.1.1.1) fashion by six methine subunits. As such, they may be referred to as being [26]hexaphyrins-(l.l.l.l.l.l) in the Franck-type nomenclature used in this book. Here, the key macrocycle name, hexaphyrin, came from Gossauer. Indeed, because this investigator viewed products 7.9-7.12 as being the next higher porphyrin homolog in the porphyrin-pentaphyrin series coined the term hexaphyrin for this class of macrocycles. 

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