Pyridine complexes linkage isomers

Purpureocobalt — see Cobalt, chloropentaammine-Purpureocobaltic chloride —see Cobalt, chloropentaammine-, chloride Pyridine, 2-hydroxy-5-methyl-dodecacobalt complexes, 168 Pyridine complexes linkage isomers, 186 Pyrimidine complexes... 

A variety of linkage isomer pairs have been produced from somewhat more complex ligands, such as substituted pyridines and benzoic acids, for example (5a) and (5b).77,78 These complexes have been employed in detailed studies of inner-sphere electron transfer reactions in order to assess the importance of the nature and orientation of the bridge between redox centres on intramolecular electron transfer rates.77-80... 

Momenteau s route to doubly-strapped porphyrins was easily adapted to produce compounds in which an axial base was incorporated into one of the straps Condensation of tetra(o-hydroxyphenyl)porphyrin (250) (mbcture of four isomers) with one equivalent of 1,12-dibromododecane gave a mixture of two singly-linked porphyrins, depending on whether adjacent (255), or opposite (254) meso-phenyl groups were linked. This mixture was reacted with 3,5-bis(3-bromopropyl)pyridine 256 and the desired cross trans-linked isomer 257 isolated by preparative tic (5% overall yield) (Scheme 77). A similar porphyrin 259 was prepared from a,p,a,p-tetra(o-aminophenyl)porphyrin (142) in this case the straps were tied to the porphyrin skeleton by amide linkages (Scheme 78). Following iron insertion and reduction, visible absorption and H-NMR spectra of both compounds were consistent with a five-coordinate high spin (S = 2) iron(II) complex. 

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