Macrocyclic complexes dinuclear sites

Magnetic susceptibility measurements carried out on (15) in the temperature range 5 to 300 K are consistent with a system composed of an antiferromagnetically coupled copper(II) pair and a magnetically independent third copper(II) ion. The macrocyclic complex therefore reproduces qualitatively features of the oxidase active site and the observed 2J value of -192 cm indicates the presence of a moderate antiferromagnetic interaction within the dinuclear moiety, albeit weaker than that of the protein type-3 site which is diamagnetic even at room temperature. 

Love and coworkers have reported a series of dinuclear cobalt complexes derived from a rigid binucleating macrocycle H4L 18 as shown in Fig. 26 (150). The synthesis of the dicobalt complex [Co2(L18)] (36) was achieved by an anaerobic transamination reaction between H4L18 and [Co(thf) N(SiMe3)2 2] in THF. The unsaturated species 36 forms a bis(pyridine) adduct, 36 py2 (py — pyridine), which has a cleft-like structure reminiscent of pacman diporphyrin complexes (151,152). Both cobalt ions are square pyramidal, with Col and Co2 displaced out of the N4-basal planes by 0.17 and 0.18 A, respectively. The apical sites are occupied by pyridine nitrogen atoms that are exo and endo to the cleft. Interestingly the endo pyridine is canted and reflects the... 

---