Potassium-controlled synthesis of heterotopic macrocycles based on isothiosemicarbazide

The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H2NNC(SCH3)NH2·HI) in the presence of potassium triflate, followed by addition of M(CH3COO)2·nH2O, where M=Ni, Cu, Zn, afforded [NiLKI3] (2), [NiLK(CF3SO3)] (3), [CuLK(CF3SO3)(CH3OH)] (4) and [(ZnILK)2CH3OH] (5), respectively. Compounds 2–5 have been characterised by X-ray crystallography. IR, electronic, mass, 1H, 13C{1H} and 19F{1H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin–spin interactions, which are mostly dipolar in origin.