Metalloporphyrins dimers

Several papers have appeared concerning Ru -porphyrin complexes. The first examples of metalloporphyrin dimers linked by M—M bonds have been synthesized ... 

Metalloporphyrin Dimeric S2 Emission Resulting from Triplet-Triplet Annihilation... 

As is known, the triplet and singlet tetrapyrrolic pigment states are caused by excitation of delocalized ir electrons of the heteroaromatic macrocycle (1 ). The most favourable structure of dimeric complexes for metal 1oporphyrin TTA seems to be a sandwich dimer as in the case when molecular orientation of plane to plane electronic shells reaches the maximum overlap. Quantum chemistry calculations of metalloporphyrin dimers indicates that for the dimeric emission process the 2 state is split into states of higher energy (SJ) and lower energy ( 2). In the case of a sandwich dimer of 04 symmetry, the following states are seen ... 

Fig. 42 Effect of chain fluorination on the LC phases of peri-hexabenzocoronene based mesogens (compounds 152-155) [274—276] and the fused metalloporphyrin dimer 156 (7/° C) G = glassy state, Co/ortho = orthorhombic phase [277]...

Only a few compounds containing Ru, Os, Rh or Ir do not possess type C. Notable are the metalloporphyrin dimers with Ru = Ru (entry 3) or Rh-In bonds (entry 34), the alkyl or acyl rhodium(III) (entries 31, 36, 38), alkyl-iridium(III) (entry 39) or arylruthenium(III) compounds (entry 12). All these species contain pentacoordinate noble metal ions, Type B. A reason for this unusual behavior of the metal ions is seen in the strong trans effect of the axial ligand L in these systems which is a strong o-donor (metalloporphyrinyl, alkyl, aryl, acyl) which precludes further coordination in the trans position of L. The reluctance of RhMe(OEP) to accept an axial ligand is shown by its crystallization as a re-dimer from n-hexane in presence of the base 1-Meim. 

Metal-metal multiple bonds in Ad- and 5d-metalloporphyrin dimers 93ACR586. 

The great synthetic ability of the oxidized Ru metalloporphyrin dimers permits the development of a general synthesis of o-bonded ruthenium(III) porphyrins. 

Di(porphyrinato)rhodium(II) [Rh(Por)]2 described by OgoshP Wayland , Coil-man, and Kadish are the only known metalloporphyrin dimers containing one single metal-metal bond. Oxidative cleavage (Eq. 24) or thermal homolytic cleavage (Eq. 25) of the Rh-H bond of Rh(OEP)H can produce the [Rh(OEP)]2 dimer The Rh" dimer may also be formed by electrochemical reduction of some Rh" porphyrin complexes (See Sect. D III 4). 

Analogously, apparently super-Nemstian responses to monoanions as observed with metalloporphyrin-based ISEs were shown to result from the formation of OH -bridged metalloporphyrin dimers in the ISE membranes (31, 45). Apparently super-Nemstian responses to F with slopes from -70 to 85 mV/decade were obtained with membranes based on Ga(III)octaethylporphyrin and anionic sites, which were quantitatively explained as responses co-determined by F as the primary ion and OH ions as the secondary ion with 1 1 and 1 2 complexation stoichiometry, respectively. 

Electron transfer reactions from metalloporphyrin dimers have been studied using molecules that have a quinone moiety chemically attached to the porphyrin ring. These metalloporphyrin complexes are designed such that charge separation can be accomplished between the porphyrin and the quinone, and that these transients can then be used as oxidants. 

Figure 8.3.1. Unwanted metalloporphyrin dimerization L is a nitrogen base, e.g., imidazole.

Sakurai, X, Shi, K., Sato, H., Tashiro, K., Osuka, A., Saeki, A., Seki, S., Tagawa, S., Sasaki, S., Masunaga, H., Osaka, K., Takata, M., Aida, X Prominent electron transport property observed for triply fused metalloporphyrin dimer directed columnar liquid crystalline assembly by amphiphilic molecular design. J. Am. Chem. Soc. 130, 13812-13813 (2008)... 

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