Extended porphyrins

Sapphirins ( extended porphyrins , cyclic pentapyrroles) 91SL127. 

A new type of complex with a different spectroscopic application is provided by the texaphyrins, compounds of extended porphyrins where the ring contains five donor nitrogens. These have attracted considerable interest because of their possible medicinal applications. 

Texaphyrins. A new type of complex is provided by the texaphyrins, compounds of extended porphyrins where... 

Olefinic pyrazines like 108 were shown to react with QH in the superacid TfOH to give anti-Markovnikov addition products like 109 <050L2505>. The orientation observed is presumed to be due to the multiply charged heterocycle adjacent to the olefin. Pyrazine o-quinodimethanes underwent Diels-Alder condensation with meso-tetraarylporphyrins to give new jt-extended porphyrins <05TL2189>. A one-pot formation of polycyclic - and -lactones like 111 was developed using the reaction of pyridine and pyrazine (110) with bis(trimethylsilyl)ketene acetals. Many of them were characterized by X-ray <05EJO3724>. 

Porphyrin chromophores have received much attention, particularly as photoelectric devices and molecular wires. Efficient re-electronic communication between porphyrin macrocycles is pivotal in various complex functions. K.M. Smith et al. showed that neighboring acetylenic units on porphyrins provide a means for the efficient construction of aromatic superstructures triggered by the Bergman cyclization reaction conditions and give rise to novel [n]phenacenoporphyrins, which belong to a new class of highly re-extended porphyrins." ... 

Most devices based on Pc are fabricated by vacuum deposition, i.e. thermal evaporation. However, recent solution-based Langmuir-Blodgett (LB) techniques have also been used. LB-films of 25h-251 gave poor (10 cm V s for 25j) to moderate (1.7 x 10 cm V s for 251) mobilities (Figure 3.1.9).[162-164] More recently, high mobilities of 0.24-0.60 cm V s have been observed for LB films of amphiphilic tris(phthalocyaninato) rare earth triple-decker complexes, 25m-25o.[165] OFET characteristics have also been reported for porphyrin derivatives, 25p-q with mobilities of 2.2 x 10 cm V s and 0.012 cm V s, respec-tively.[166-168] LB-prepared thin films of Cyclo[8]pyrrole (25r), an extended porphyrin-like molecule, also exhibited a high mobility of 0.68 cm V s, but with a low on/off ratio.[169]... 

Both porphyrins and fuUerenes can be deposited onto surfaces imder ultra-high vacuum (UHV) conditions as studied by Diederich et aL [126, 127]. In a first step, a monolayer of porphyrins or extended porphyrin analogues can be formed which can be analyzed using AFM or STM imaging techniques. UHV deposition of a second layer of Ceo on top of a full monolayer of porphyrins leads to the formation of supramolecular assem-bhes, and the precise structure of the arrangement of the Ceo on the patterned layer can be controlled by the porphyrin structure. The observed modes of self-assembly result from a delicate balance between the fullerene-porphyrin interaction and the conformational motion within the porphyrin monolayer. 

Figure 32.. Structure of Hosoda s extended porphyrinic ring system,...

The regioselective, Jt-extended pyrrole-fused porphyrinoids 13 have been prepared via the 1,3-dipolar cycloaddition ofmeso-alkylidene(benzi)-porphyrins (14CC9277) repeated cycloadditions, followed by oxidation-reduction of these pentaporphyrins gave Jt-extended porphyrin analogs. 

Synthesis of TT-extended porphyrins via intramolecular oxidative couphng 12CC10069. 

Pyrrole-containing receptors include porphyrins, extended porphyrins and calix[n]pyrroles. A variety of calixpyrroles have been used as sensors and in anion-separation technologies. An interesting example is the cryptand-like calixpyrrole (2.69) that binds fluoride via six of the nine hydrogen atoms, forming a one-to-one host-guest complex in dichloromethane and THF mixed solvent. The actual stoichometry is rather complicated as each of the pairs of clefts can bind fluoride ions, forming one-to-one, one-to-two or one-to-three stoichiometries. 

We have chosen to divide the porphyrinoids into two famihes the peripherally functionalized porphyrinoids (e.g., N-confiised porphyrins, jr-extended porphyrins, oligo-porphyrins) and the coie-fimctionalized (nonplanar) por-phyrinoids (e.g., porphyrinogens, alkylidene porphyrins, oxoporphyrinogens, and some oligopyrroles). The former contains mostly molecnles that have complex elaboration at their periphery, which leads to special snpramolecular properties. Core-snbstituted porphyrinoids inclnde N-snbstituted oxoporphyrinogens and even some metalloporphyrins and porphyrin dications. 

These n-extended porphyrin derivatives show the absorption bands at wavelengths higher than 700 nm. This is important for their potential use as photosensitizers in the photodynamic therapy (PDT) of tumors. 

Crossley MJ, Johnston LA (2002) Laterally-extended porphyrin systems incorporating a switchable unit J Chem Soc, Chem Common 10 1122-1123. doi 10.1039/B111655J Dahbi S, Methnani E, Bisseret P (2010) First synthesis of 2-phosphonylated quinoxaline 1,4-dioxides an extension to the Beirut reaction. Tetrahedron Lett 51(42) 5516-5520. doi 10. 1016/j.tetlet2010.07.148... 

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