SUBJECTS metalloporphyrins

Ligand substitution reactions of NO leading to metal-nitrosyl bond formation were first quantitatively studied for metalloporphyrins, (M(Por)), and heme proteins a few decades ago (20), and have been the subject of a recent review (20d). Despite the large volume of work, systematic mechanistic studies have been limited. As with the Rum(salen) complexes discussed above, photoexcitation of met allop or phyr in nitrosyls results in labilization of NO. In such studies, laser flash photolysis is used to labilize NO from a M(Por)(NO) precursor, and subsequent relaxation of the non-steady state system back to equilibrium (Eq. (9)) is monitored spectroscopically. 

Metalloporphyrins containing a metal-carbon a-bond are currently limited to complexes with eight different transition metals (Ti, Ni, Fe, Ru, Co, Rh, Ir and In) and seven different non-transition metals (Al, Ga, In, Tl, Si, Ge, and Sn). These compounds have been the subject of several recent reviews(1-33 which have discussed their synthesis and physicochemical properties. 

Porphyrins and metalloporphyrins have been the subject of numerous investigations over the past century. This attention is not surprising if one considers that particular derivatives play central roles in essential biological processes such as photosynthesis, dioxygen transport and storage, and electron transfer. 

Metal nanoparticles have extraordinary size-dependent optical properties, not present in the bulk metal and have, consequently, been the subject of intense research during the past decade or so.27 Attention has recently focused on functionalising colloidal nanoparticles with molecular recognition components for potential sensing applications.28,29,30 We have prepared a new amido-disulfide functionalised zinc metalloporphyrin (8) which was self-assembled on to gold nanoparticles to produce a novel anion-selective optical sensing system (9) (Scheme 3).4... 

Our assignments of the near infra-red spectra have important implications for the interpretation of the visible spectra. The spectra of low-spin ferric haemoproteins in the region 13—25 kK are fairly typical of metalloporphyrins, and can be explained in terms of the theory discussed in Section IIB. However, a weak band is sometimes seen at 14—16 kK which is z-polarized in ferricytochrome-c (90), ferrihaemoglobin azide (110) and ferrimyoglobin azide (92). The band at 14.4 kK in ferricytochrome-c has been the subject of much discussion. At neutral pH it has an intensity of e=800 (59) but this is very sensitive to the pH and the conformation of the protein (55). It has been suggested that this band arises from electron transfer from a distal cysteine or tyrosine to the metal (4), and that the ease of electron transfer in this way could play... 

As indicated above, metalloporphyrins have also been the subject of much... 

Since our original article was written, a regular series of reviews of porphyrin chemistry has begun two books on the chemistry of pyrroles, a second edition of Porphyrins and Metalloporphyrins (based on Falk s original book), and a small handbook concerned with laboratory methods and spectroscopic data have now appeared. A seven-volume treatise on the chemistry and biochemistry of porphyrins has also recently been published volumes 1 and 6 are particularly relevant to the subject matter of this article. 

The axial substitution reactions of metalloporphyrins have been the subject of considerable interest over the last two decades. A very detailed spec-trophotometric SF study of the reaction of imidazole with [mc50-tetrakis(p-sulfonatophenyl)porphinato]diaquochromate(III) in the range pH 6.00 to 0.100 mol dm NaOH at / = 1.00 mol dm (NaC104) shows several paths for the imidazole substitution ... 

In this chapter, we will concentrate on the subjects of synthetic strategies for (1) porphyrins and the capability of the products for molecular recognition of small organic substrates via intermolecular and noncovalent interactions (2) effective electron-transfer reaction regulated by intermolecular interaction " and (3) self-assembled porphyrin to construct supramolecular system for the guest. The Structures of porphyrins and their metalloporphyrin derivatives have attracted chemists due to their suitability as a host framework for organic guest molecules. 

Vibrational spectra of metalloporphyrins have been studied extensively because of their biological importance as prosthetic groups of a variety of heme proteins. Thus, many review articles have been published on this subject, and most of them discuss the vibrational spectra of metalloporphyrins together with those of heme proteins. Nakamoto has reviewed several articles concerning these macrocycles and discussed the state of the art of the normal coordinate analysis, the assignment of the structure-sensitive vibrations, the metal-macrocycle ring coordination, the metal-metal bonded porphyrins and the n-n complex formation and dimerization. ... 

Metalloporphyrins are versatile oxidation catalysts. The field is dominated by iron porphyrins, which serve as synthetic models for heme type oxygenases. They have been extensively studied as witnessed by the number of review articles and books on the subject. It is only possible here to cite a few items of the vast selection ... 

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