A new twist on an old ligand: a [Mn] double square wheel and a [Mn] contorted wheel

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal...

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Veröffentlicht in:Inorganic chemistry frontiers 2021-04, Vol.8 (7), p.184-189
Hauptverfasser: Tziotzi, Thomais G, Coletta, Marco, Gray, Mark, Campbell, Cameron L, Dalgarno, Scott J, Lorusso, Giulia, Evangelisti, Marco, Brechin, Euan K, Milios, Constantinos J
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Sprache:eng
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Zusammenfassung:Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the pro-ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH 3 ) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO 3 ) 2 ·6H 2 O with LH 3 in basic methanolic solutions leads to the formation of [Mn III 12 Mn II 4 (μ 3 -O) 6 (μ-OH) 4 (μ 3 -OMe) 2 (μ-OMe) 2 (L) 4 (LH) 2 (H 2 O) 10 ](NO 3 ) 6 (OH) 2 ( 1 ) and [Mn III 10 (μ 3 -O) 4 (μ-OH) 4 (μ-OMe) 4 (L) 4 (H 2 O) 4 ](NO 3 ) 2 ( 2 ), the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [Mn III 6 Mn II 2 ] square wheels, linked through a common centre, and the latter a single [Mn III 10 ] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L 3− /LH 2− ligands dictate the orientation of the Jahn-Teller axes of the Mn III ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2 . Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH 3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes. The use of 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH 3 ) in manganese cluster chemistry leads to the synthesis of a {Mn 16 } double square wheel and a {Mn 10 } contorted wheel.
ISSN:2052-1553
2052-1545
2052-1553
DOI:10.1039/d0qi01495h