A bulky oxime for the synthesis of Mn(III) clusters

• Published in: Journal of coordination chemistry 2015-10, Vol.68 (19), p.3472-3484
• Main Authors: Kalofolias, Dimitris A., Flamourakis, Andreas G., Siczek, Milosz, Lis, Tadeusz, Milios, Constantinos J.
• Format: Article
• Language: English
• Subjects: Crystal structures; Magnetic properties; Mn(III) oximato complexes; Single-molecule magnets
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2015.1075014

The reaction between Mn(OAc) 2 ·4H 2 O and Br-saoH 2 (=5-Br-salicylaldoxime) in EtOH in the presence of NMe 4 OH led to the formation of the hexanuclear cluster [Mn 6 O 2 (Br-sao) 6 (OAc) 2 (H 2 O) 2 (EtOH) 2 ]·2.8H 2 O·2.2EtOH (1). Switching from Mn(OAc) 2 ·4H 2 O to Mn(ClO 4 ) 2 ·6H 2 O, the same reaction upon addition of pivH (= trimethyl acetic acid) yielded [Mn 6 O 2 (Br-sao) 6 (piv) 2 (H 2 O) 2 (EtOH) 2 ]·6EtOH (2 6EtOH), and finally upon changing pivH to NaO 2 CPh, we were able to isolate [Mn 6 Na 2 O 2 (Br-sao) 6 (O 2 CPh) 4 (H 2 O) 2 (EtOH) 4 ]·6EtOH (3 6EtOH). Clusters 1 and 2 6EtOH describe "typical" [Mn 6 /oximate] complexes consisting of two {Mn 3 } oxo-centered triangular units bridged by oximate groups, while in 3 6EtOH these triangular motifs are separated by two sodium cations. An investigation into the magnetic properties of all three clusters revealed the presence of dominant antiferromagnetic interactions, leading to ground states of S = 4 and 2 for 1 and 3, respectively. Finally, cluster 2 6EtOH functions as a single-molecule magnet with U eff  = 27.54 K.