Influence of Mn/Ca ratio in Mn-Ca coordination clusters: Synthesis, structure, and magnetic characterisation

International audience; Similar reactions of MnCl 2 ⋅4H 2 O and CaCl 2 with 2,6-bis(hydroxymethyl)-4-methylphenol gave heterometallic coordination clusters with very different nuclearities, depending on the Mn:Ca ratio used. With a 1:1 ratio, the hexanuclear cluster [Mn III 3 Ca II 3 (μ 3-Cl(HL Me) 6 (H 2 O) 6 ]Cl 2 ⋅6.74H 2 O (2) with a "triangle-in-triangle" topology was obtained. However, a Mn:Ca ratio of 2:1 resulted in [Mn III 12 Mn II Ca II 6 (μ 4-O) 8 (μ 3-Cl) 3.7 (μ 3-η 1-N 3) 4.3 (HL Me) 12 (-MeCN) 6 ]Cl 2 •15MeOH (3), which corresponds structurally to the replacement by Ca 2+ of six of the seven Mn II centers in our previously-published cluster [Mn III 12 Mn II 7 (μ 4-O) 8 (μ 3-η 1-N 3) 8 (HL Me) 12 (MeCN) 6 ]Cl 2. Magnetic studies showed that the three Mn III centers in 2 are moderately antiferromagnetically coupled, while the results for 3 allowed an experimental estimate of the Mn III-Mn III coupling in the original [Mn 19 ] cluster.