Porphyrins potential applications

These studies have led to the development of other Co porphyrins with potential applications in a variety of areas with the common theme of catalyzing the efficient reduction of 02. These systems are explored in Section 6.1.4. 

Cobaloxime(I) generated by the electrochemical reductions of cobaloxime(III), the most simple model of vitamin Bi2, has been shown to catalyze radical cyclization of bromoacetals.307 Cobalt(I) species electrogenerated from [ConTPP] also catalyze the reductive cleavage of alkyl halides. This catalyst is much less stable than vitamin Bi2 derivatives.296 It has, however, been applied in the carboxylation of benzyl chloride and butyl halides with C02.308 Heterogeneous catalysis of organohalides reduction has also been studied at cobalt porphyrin-film modified electrodes,275,3 9-311 which have potential application in the electrochemical sensing of pollutants. 

A second example has been addressed in which the synthesis and potential application of a series of neutral O-glycosylated porphyrin dimers and two original O-glycosyl cationic dimers were examined in PDT. In order to understand the influence of the number of glycosyl moieties, the spatial geometry and the ionic character on their photodynamic activity was evaluated.144 The in vitro results... 

Porphyrins are also able to directly interact with the nanotube sidewalls. For example, tetraphenyl porphyrin (H2-TPP) has been reported to interact with nanotubes to form TPPs/CNTs compounds that are stable for days. Stability has been enhanced by using a micelle-assisted approach, leading to stable structures with potential applications in light harvesting devices [76]. 

The low stability of the magnesium porphyrins has precluded most potential applications. Other metallotetrapyrroles have found industrial uses for oil desulfurization, as photoconducting agents in photocopiers, deodorants, germicides, optical computer disks, semiconductor devices, photovoltaic cells, optical and electrochemical sensing, and molecular electronic materials. A few scattered examples of the use of Mg porphyrins in nonlinear optical studies have appeared" and magnesium phthalocyanines have been used in a few studies as semiconductor or photovoltaic materials" " One of the few... 

Once the synthetic methodologies were developed, the research efforts were focused on the preparation of photoactive systems where fullerenes had already shown potential applicability, such as organic photovoltaic materials. In these molecular-scale engineered systems, a fullerene electron acceptor contained in one submolecular fragment is coupled with an electron donor contained in the opposite component. Zinc porphyrins were thus coupled to in many different architectures such as, for instance, in that shown in Scheme 9.11, where the ZnP was appended to... 

The Fullerenes form particularly strong complexes with porphyrins as exemplified by the X-ray crystal structure of the covalent Fullerene-porphyrin conjugate 15.8 (Figure 15.29).48 This property allows fullerenes and porphyrins to form extended supramolecular arrays (even when not covalently linked) and has been used to engineer host-guest complexes in which a Fullerene is sandwiched in between a pair of porphyrins, and ordered arrays involving interleaved porphyrins and Fullerenes. Applications include the use of porphyrin solid phases in the chromatographic separation of Fullerenes and potential applications in porous frameworks and photovoltaic devices.49... 

The present article will focus in particular on structurally characterized complexes and will refer to current trends and potential applications, simultaneously aiming at a coherent picture of the entire family of organometallic lanthanide amides including the inorganic derivatives. The elements Sc, Y, La will be treated as lanthanide elements Ln. Previous reviews cover this subject mostly as an aspect wrapped up under a comprehensive depiction of both metal amides [19] and lanthanide chemistry [20]. Other articles focus on special topics in this field, e.g., inorganic amides [21], silylamides [22], phthalocyanines [23] or porphyrins [24],... 

Due to the great potential applications and the widespread interests of OFETs, several review articles with emphasis on different aspects of OFETs have been published [8-13], However, despite the extensive studies and increasing research interests in phthalocyanine as well as porphyrin semiconductors, there is still no review article that systematically generalizes the research achievements in the field of tetrapyrrole organic semiconductors for OFETs. Thus, the present contribution should interest scientists in both industrial and theoretical fields. The main contents of this chapter is as follows Firstly, some basic introduction of the structure and characteristics of OFET is provided then theoretical factors that influence the performance of OFET devices is discussed finally, the progress in phthalocyanine-based OFETs in the order of p-type, n-type, and ambipolar semiconductors is summarized. 

Corroles are tetrapyrrole macrocycles that are closely related to porphyrins, with one carbon atom less in the onter periphery and one NH proton more in their inner core. They may also be considered as the aromatic version (identical skeleton) of the only partially conjugated corrin, the cobalt-coordinating ligand in Vitamin B. Two potential application of corroles are in tumor detection and their use in photovoltaic devices. Selective snbstitntion of corroles via nitration, hydroformylation, and chlorosulfonation for the gallinm were studied in detail and the respective mechanistic pathways and spectroscopic data were reported, (an example is shown in Fignre 27). Overall, over 139 varions corroles were synthesized and the effect of various metal complexation pertaining to their selective reactivity examined. ... 

In the case of expanded porphyrins, the transport-based approach, which is relevant to potential applications involving the regulation of anion flux (e.g., the development of chloride anion carriers for treatment of cystic fibrosis or adjuvants to allow improved uptake into cells of antiviral agents), has for the most part involved the use of a U-tube aqueous I-dichloromethane-... 

Radiative and Nonradiative Decay Processes - Due to the potential application of these compounds as photosensitizers for photodynamic therapy" the photophysical properties of porphyrins and phthalocyanines, and their corresponding metal complexes, have been investigated extensively over the past decade. The photophysical properties of water-soluble metalloporphyrins, and especially the tetraphenylsulfonates," have been re-examined but nothing new has been found. The disulfonated metallophthalocyanines (MPcS2, where M = Al ", Ga" , or Zn") form complexes with fluoride ions for which the fluorescence yields and lifetimes are decreased with respect to the parent dyes while there are... 

Within the large number of multiredox arrays containing metalloporphyrins/covalently bound (conjugate) fullerene-metalloporphyrin dyads have gained enormous interest in the last ten years, mainly due to their potential application as artificial antennae Due to the multiredox behaviour of the fullerenes (up to six reversible one-electron reductions and at least one reversible one-electron oxidation), the porphyrin ligands and the incorporated metals, the assignment of electron-transfer steps in such systems is difficult. Recently, spectroelectrochemical characterisation has been carried out on a number of fullerene-[(TPP)Co] dyads shown in Scheme 4.3, which exhibit rather complex redox behaviour (Figure 4.19). 

Since Pt dissolution is favored by high electrode potential, relative humidity, and temperature, the possibility to limit the risk of electrocatalyst aging is based on the use of Pt-alloy catalyst instead of pure platinum, at least for the cathode, which is characterized by higher potential with respect to anode, and by adoption of operative conditions not too severe in terms of humidity and temperature. While this last point requires interventions on the membrane structure, the study of catalyst materials has evidenced that a minor tendency to sintering can be obtained by the addition of non-noble metals, such as Ni, Cr, or Co, to the Pt cathode catalyst [59, 60], suggesting a possible pathway for future work. On the other hand also the potential application of non-platinum catalysts is under study, in particular transition metal complexes with structures based on porphyrines and related derivatives have been proposed to substitute noble metals [61], but their activity performance is still far from those of Pt-based catalysts. 

Because of their extended 7r-system, porphyrins and related compounds absorb visible light. Therefore, their potential application as chromophores for harvesting solar energy, as a means to mimic the natural role of chlorophyll, has been under intense study. In addition, porphyrins can act as mediators of electron transfer, both as oxidants and as reductants. Therefore, the role of porphyrins as catalysts for various reductions and oxidations also has been studied by many authors. 

Potential applications of easily oxidisable porphyrins are as sources of reduced oxygen species (e.g. peroxide, hydroxyl radicals) and as molecular conductors—one of the subjects of the next section. 

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