Tetrapyrrole complexes phthalocyanines

Phthalocyanines - Pthalocyanine complexes form a very large class among tetrapyrrole complexes. Their chemistry, physics, and applications for novel materials are being reviewed in a multi volume series [106]. Usually they are made by reductive tetramerization of phthalodinitrile with a metal salt (see below), but metallations of free phthalocyanine, H2(Pc), are also documented. Work in the last two decades has been concentrated on phthalocyanine complexes of Ru, Os, Rh, Pd, Pt, and Ag Berezin gives references on IrCl(Pc) and AuCl(Pc) [107]. 

Diazaporphyrins - Like the phthalocyanines, a 10,20-diaza-porphinoid palladium complex was composed by cyclooligomerization. The condensation of two suitable bispyrrole halves yielded the tetrapyrrole complex, cis [1,11-dimethoxy-2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18-hexadecamethyl- 10,20-diaza-decahydro-porphyrinato]palladium(II) [124]. 

The present article reviews the photochemical deactivation modes and properties of electronically excited metallotetrapyrroles. Of the wide variety of complexes possessing a tetrapyrrole ligand and their highly structured systems, the subject of this survey is mainly synthetic complexes of porphyrins, chlorins, corrins, phthalocyanines, and naphthalocyanines. All known types of photochemical reactions of excited metallotetrapyrroles are classified. As criteria for the classification, both the nature of the primary photochemical step and the net overall chemical change, are taken. Each of the classes is exemplified by several recent results, and discussed. The data on exciplex and excimer formation processes involving excited metallotetrapyrroles are included. Various branches of practical utilization of the photochemical and photophysical properties of tetrapyrrole complexes are shown. Motives for further development and perspectives in photochemistry of metallotetrapyrroles are evaluated. 

D.K.R Ng, J. Jiang, K. Kasuga and K. Machida conclude this volume with an overview of rare-earth and actinide half-sandwich tetrapyrrole complexes. When tetrapyrrole molecules, such as porphyrins or phthalocyanines, are reacted with the rare earths and actinides, they are split in half, forming the half-sandwich complexes because the metal atoms are larger than the core size of the macrocyclic ligands. They also can form sandwich-type complexes in which the metal centers are sandwiched between the macrocycles. However, this chapter is devoted to the former class of compounds. Ng and co-workers discuss the synthesis, structure, and spectroscopic and electrochemical properties of half-sandwich complexes of porphyrins and phthalocyanines. The authors... 

As demonstrated above, lanthanide complexes containing phthalocyanines and various porphyrins as ligands have been studied in great detail. In contrast, the number of studies on analogous complexes containing phthalocyaninato and tetrapyrrole ligands like tetrabenzoporphyrinato-, tetraazaporphyrinato- or N-confused porphyrinato-, is rather limited [151-155], though such compounds also attract considerable interest. 

Coordination compounds composed of tetrapyrrole macrocyclic ligands encompassing a large metal ion in a sandwich-like fashion have been known since 1936 when Linstead and co-workers (67) reported the first synthesis of Sn(IV) bis(phthalocyanine). Numerous homoleptic and heteroleptic sandwich-type or double-decker metal complexes with phthalocyanines (68-70) and porphyrins (71-75) have been studied and structurally characterized. The electrochromic properties of the lanthanide pc sandwich complexes (76) have been investigated and the stable radical bis(phthalocyaninato)lutetium has been found to be the first example of an intrinsic molecular semiconductor (77). In contrast to the wealth of literature describing porphyrin and pc sandwich complexes, re-... 

The application of X-ray absorption spectroscopy (XAS), X-ray absorption nearedge structure (XANES), and EXAFS to tetrapyrroles that are not iron porphyrins is as yet relatively limited. Studies include EXAFS of 3-propenamide-zinc(II)-mcso-tetraphenylporphyrin complexes [201], XANES of vanadyl-phthalocyanine and vanadyl-meso-tetraphenylporphyrin [202], and XANES of iron(III)-phthalocyanine and its CO adduct [203]. 

Formally, tetravalent cerium is long known to form stable sandwich complexes with tetrapyrrole-type macrocyclic ligands such as porphyrines, phthalocyanines, and 2,3,-naphthalocyanines (Scheme 12). For the rare earth sandwich complex series, virtually all the neutral complexes can be formulated as Ln° (ring-1 ) (ring-2 ), in which a trivalent rare earth metal center is sandwiched between a... 

Tetrapyrrolic macrocycles, such as porphyrin, consisted of four pyrrole units bonded by different bridges, for example methene in the case of porphyrins and aza-methene in the case of phthalocyanines [1]. These ligands can complex metal ion transition and the synthesized metallocomplexes are extremely stable [2, 3]. While some metalloporphyrins constitute the redox center of naturally occurring proteins, like heme in hemoglobin, metallophthalocyanines are purely synthetic molecules. The (electro) chemical properties of MN4 complexes have been widely studied and have been particularly used for the catalysis of several electrochemical reactions in homogeneous solutions [4]. It was shown that the electrochemical properties of a... 

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