Porphyrins solids

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... 

As evident from a comparison between the voltammetric data in the lower panels in Figures 3.47 and 3.48, the Fe porphyrins display better defined metal-based redox peaks compared with their Co counterparts. Furthermore, and in analogy with FeTsPc, set for all Fe porphyrins (solid circles in Figure 3.47) was slightly more... 

Yamashita, K., Harima, Y., Matsubayashi, T. (1989). Conductance control of porphyrin solids by molecular design and doping, J. Phys. Chem., 93 5311. 

Bhyrappa, P. Wilson, S.R. Suslick. K.S. Hydrogen-bonded porphyrinic solids Supramolecular networks of octahydroxy porphyrins. J. Am. Chem. Soc. 1997. 119. 

In contra.st to their interaction with applied electric, magnetic or electromagnetic fields, porphyrins and metalloporphyrins can also interact with other chemical species. One might view such interactions as chemo-responsive rather than field-responsive. The development of chemo-responsive materials based on porphyrins, however, is somewhat less advanced. One example of such applications is that porphyrin solids, being highly porous, are involved in the current development of molecularly based molecular sieves or shape-selective solid catalysts. Porphyrins and metalloporphyrins have also been examined for a variety of sensor applications, further proving their importance as a class of chemo-responsive materials. 

A number of researchers have explored synthetic strategies for the construction of porphyrinic solids that contain molecule-sized cavities or channels. Porphyrin macrocycles can be envisioned as flat, rigid, geometrically square building blocks approximately I nm wide. Out-of-plane twisting by the 5,10,15,20-substituted phenyl rings (as necessitated by steric constraints) provides a route to constmct structures extending beyond the porphyrin macrocycle plane. Chemical modification of the perimeter is facile in many cases. Additionally the thermal stability makes them an attractive precursor for potential use at elevated temperatures. Furthermore, metalloporphyrins have demonstrated catalytic ability in a wide variety of reactions ... 

Goldberg and coworkers have synthesized porphyrinic solids that utilize other weak intcrmoiccular interactions between porphyrin building blocks. The structures of inclusion compounds formed from halogen-substituted... 

Solid SIMS has proved useful in the study of acetylated precursors of a series of glycosylated porphyrins (solid SIMS spectra are not complicated by chemical noise or matrix reactions). ... 

Jones R, Tredgold R FI and Flodge P 1983 Langmuir-Blodgett films of simple esterified porphyrins Thin Solid Films 99 25-32... 

Jones R, Tredgold R FI, Floorfar A and Flodge P 1984 Eleetrioal-eonduetivity in Langmuir-Blodgett films of porphyrins—inplane and through-the-film studies Thin Solid Films 113 115-28... 

Tliere are several reasons for this great interest in the tautomerism of porphyrins (which could justify its own review) (1) their biological significance, (2) their applications in material science ( hole burning is related to their tautomerism), (3) the simplicity of the system (annular tautomerism involving intramolecular proton transfer both in solution and in the solid state), and (4) the possibility of elucidating the kinetic processes in great detail. 

Tire solid-state behavior of porphyrins, as studied by both NMR and crystallography, are discussed in reference to Scheme 1. 

In (87BBPC941), Limbach made a major contribution to understanding crystalline and amorphous environments using compounds that in the gas phase show symmetric double minimum potentials. Several compounds were used to illustrate the periodic (crystal) and random (glass) distortions of the potential surface, among them H2P and porphycene. Tlie seminal paper on the tautomerism of porphyrins in the solid state is that of Limbach... 

Fig. 1. Combined proton tautomerism and 90° rotation of porphyrin molecule in the solid state, (a) Reduced scheme proposed by Frydman et al. (89JA7001). (b) Complete scheme according to Limbach et al. (94JA6593).

---