Synthesis and characterization of heterometallic rings templated through alkylammonium or imidazolium cations.

We report the synthesis and structural characterization of a series of heterometallic rings templated via alkylammonium or imidazolium cations. The template and preference of each metal's coordination geometry can control the structure of heterometallic compounds, leading to octa-, nona-, deca-, dodeca-, and tetradeca-metallic rings. The compounds were characterized by single-crystal X-ray diffraction, elemental analysis, magnetometry, and EPR measurements. Magnetic measurements show that the exchange coupling between metal centres is antiferromagnetic. EPR spectroscopy shows that the spectra of {Cr ₇ Zn} and {Cr ₉ Zn} have S = 3/2 ground states, while the spectra of {Cr ₁₂ Zn ₂ } and {Cr ₈ Zn} are consistent with S = 1 and 2 excited states. The EPR spectra of {(ImidH)-Cr ₆ Zn ₂ }, {(1-MeImH)-Cr ₈ Zn ₂ }, and {(1,2-diMeImH)-Cr ₈ Zn ₂ } include a combination of linkage isomers. The results on these related compounds allow us to examine the transferability of magnetic parameters between compounds.