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The coordination properties of the new polynucleating ligand H 3 L1 (1,3-bis(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene) with Mn II/III are described. Depending on the solvent used, the reaction of H 3 L1 with Mn(OAc) 2 yields either of the two new multinuclear assemblies [Mn 2 (HL1) 2 (py) 4 ] (1) and [Mn 3 (HL1) 3 ] (2), as revealed by X-ray crystallography. The structure of 2 is remarkable in that it shows a unique asymmetric triple-stranded helicate. Complexes 1 and 2 can be interconverted by controlling the solvent of the reaction system, and therefore, this ensemble constitutes an interesting externally addressable switch. In the presence of Mn III /pyridine, partial degradation of H 3 L1 occurs via oxidative cleavage, and the new complex [Mn 2 (L2) 2 (py) 4 ] (3) is formed. The crystal structure of this complex has shown the fully deprotonated form of the new donor H 3 L2 (3-(3-oxo-3-phenylpropionyl)-5-methylsalicylic acid). From the same reaction, the Mn II complex 1 is also obtained. A rational synthesis of H 3 L2 is reported, and this has been used to prepare 3 in high yields, directly from its components. Variable-temperature magnetic susceptibility ( m ) measurements were performed on complexes 1−3 under a magnetic field of 1 kG. The data for each complex were fit to the appropriate m vs T theoretical equation, respectively. In 1, the Mn II ions are uncoupled, with g ) 2.01. The data from 2 were fit by assuming the presence of an exchange coupled Mn II ‚‚‚Mn II pair next to a magnetically isolated Mn II center. The fit gave J ) −2.75 cm -1 , g 12 ) 1.97, and g 3 ) 1.92, respectively. In 3, two models fit the experimental data. In the most satisfactory, the Mn III ions are coupled antiferromagnetically with J ) −1.48 cm -1 and g ) 1.98 and a term for weak ferromagnetic intermolecular exchange is included with zJ′ ) 0.39 cm -1 . The other model contemplates the presence of two uncloupled zero field split Mn III ions.

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Two New bis-β-Diketones as Ligands for Novel Systems in Supramolecular Chemistry. -The Claisen condensation of 1,3-diacetyl-2-hydroxy-5-methylbenzene (I) with esters yields new outstanding tetraketone ligands. -(AROMI, G.; GAMEZ, P.; CARRERO BERZAL, P.; DRIESSEN, W. L.; REEDIJK*, J.; Synth. Commun. 33 (2003) 1, 11-18; Leiden Inst. Chem., Leiden Univ., NL-2300 RA Leiden, Neth.; Eng.) -K. Woydowski 22-038