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 par...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_(12)^(Ⅲ)Mn_(4)^(Ⅱ)(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_(6)^(Ⅲ)Mn_(2)^(Ⅱ)]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.展开更多
基金Hellenic Foundation for Research and Innovation(H.F.R.I.)under the“First Call for H.F.R.I.Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant”(Project Number:400)the EPSRC for financial support under grant reference numbers EP/I03255X/1 and EP/I031421/1.GL+1 种基金the Ministerio de Ciencia e Innovación(RTI2018-094909-J-I00)CSIC(PIE 201960E002).
文摘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_(12)^(Ⅲ)Mn_(4)^(Ⅱ)(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_(6)^(Ⅲ)Mn_(2)^(Ⅱ)]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.
