048ChemInform Abstract The magnetic interactions between metal and ligand spins in metalloporphyrin π-cation radicals (I) are investigated as a function of d orbital type for synthetically accessible compounds containing S = 1/2 metals from the first transition series. The preparation of (Ia)-(Id) from the corresponding neutral complex by oxidation with phenoxathiinylium hexachloroantimonate is described. Extensive studies are carried out on the presumably planar compound (Ib) with an overall S = 1 state. The ferromagnetic coupling of spins is rationalized as arising from the exchange interaction of unpaired electrons in orthogonal magnetic orbitals. By contrast, (Ia), crystallizing in the space group P1 with Z=2, has a ruffled porphyrin core in the solid state and is diamagnetic (S = 0). The antiferromagnetic coupling is rationalized in terms of overlap of the magnetic orbitals, i.e. bond formation with spin pairing in the bonding MO. Applications to analogous systems of other metals are discussed.

Reaction of equimolar quantities of (I) and (II) leads to the simultaneous preparation of the title complex (III) and a new phase of the previously characterized bis(3‐chloropyridine) complex (IV), which is formed even when the starting complex (I) is in excess.