Scheme 1.
Synthesis of [Mn(PyC3A)(H2O)]- (a) substoicheometric benzyl bromide, dioxane, RT; (b) 3 equiv. tbutyl-bromoacetate, 1 equiv. KI, DIPEA, DMF, RT; (c) 1 atm H2 (g), 10% by wt. Pd/C, MeOH; (d) picolyl chloride, KI, DIPEA, DMF, RT; (e) 1:1 CH2Cl2:TFA, RT; (f) MnCl2, pH 6.5.