Dimeric porphyrins metal-bridged

Several strategies based on porphyrin derivatives have been developed to reach this objective. The first approach involves the utilization of dimeric cofacial metallic porphyrins adsorbed on the surface of an edge-plane graphite (EPG) electrode.18 An 02 molecule was expected to be coordinated to form a fi-02 bridge between the two metal centers allowing subsequent scission of the O O bond by reductive activation, while the dimeric structure acts as a four-electron reservoir. 

TCP and its metal-substituted derivatives can be made to dimerize quantitatively by the addition of cations (NU, K, Cs, Ba ) to solutions of these porphyrins ( ). The stoichiometry of the dimerization reaction establishes that two porphyrins are linked by four crown-cation-crown bridges ( ). This forces the porphyrins in a parallel configuration. For steric reasons, one ring system must be rotated relative to the other. EPR ( ) and ENDOR (IS) studies of the ground state triplet [CuTCP]2 and [VOTCP12 dimers fit a model of two parallel porphyrins with the transition metal ions positioned on a common axis perpendicular to the planes, with a center-to-center distance of 0.43 nm. 

NbCl5 and TaCls metallate porphyrins in benzonitrile at 210 °C and in phenol at 295 °C respectively.173 38 The trichloride is hydrolyzed to M(Por) 2(0)3 in which three oxygen atoms are bridging two metal ions.21 The tn-p-oxo dimer dissociates to oxoacetates MO(Por)(OCOMe) in hot acetic acid and to trihalides M(Por)X3 in hydrohalic acid (HF, HC1, HBr).17a 38 NbO(OEP)X (X = I3, F, acac) complexes are also known (Scheme 11).39... 

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