A Mn^II₆Mn^III₆ Single-Strand Molecular Wheel with a Reuleaux Triangular Topology: Synthesis, Structure, Magnetism, and DFT Studies

Abstract

The use of the anion of 3-methyl-1,3,5-pentanetriol (mpt(3-)) in manganese carboxylate chemistry has afforded the new Mn(II/III)12 cluster [Mn(II)6Mn(III)6(mpt)6(CH3CO2)12(py)6]·3CH3CN (1·3CH3CN). Complex 1 was isolated in moderate yield by the reaction of Mn(CH3CO2)2·4H2O and H3mpt in a 2.6:1 molar ratio in a solvent mixture of acetonitrile and pyridine. The structure of 1 consists of alternating [Mn(II)2(CH3CO2)3(py)](+) and [Mn(III)2(μ-OR)2(CH3CO2)(py)](3+) dimeric units (three of each dimer), linked at each end by two alkoxo and one acetate bridges; the mpt(3-) ligands adopt the η(2):η(2):η(2):μ4 coordination mode. The overall metal topology of this new Mn12 wheel resembles a guitar plectrum, or a Reuleaux triangle. Complex 1 displays an unprecedented structural topology, being the first example of a Mn(II)6Mn(III)6 wheel constructed from alternating homovalent dimers and the only known Mn12 loop with the trigonal symmetry of a Reuleaux triangle (all other reported loops were ellipsoids). Variable-temperature, solid-state direct- and alternating-current magnetization studies were carried out on complex 1, revealing the presence of antiferromagnetic exchange interactions between the metal ions in the molecule, which lead to a spin ground-state value S = 0; the exchange coupling parameters J were calculated using density functional theory employing a hybrid B3LYP functional.

A single-stranded {Gd18} nanowheel with a symmetric polydentate diacylhydrazone ligand

“…17 It was also observed in a {Mn 12 } wheel-like cluster. 18 However, such a wheel of 1 resembling a Reuleaux triangle with vertices buckled in has not been observed so far as we know. With this shape, 1 exhibits a D 3d symmetry with a 3-fold axis across the centroid and three 2fold axes across Gd1 and Gd4 (Fig.…”

Combining Complementary Ligands into one Framework for the Construction of a Ferromagnetically Coupled [MnIII12] Wheel

“…A search of the Cambridge structural database (CSD) reveals only three examples of dodecametallic Mn wheels in the literature: the metalladiazamacrocycle [Mn 12 (tpeshz) 12 (dmf) 12 ] (H 3 tpeshz= N ‐ trans ‐2‐pentenoylsalicylhydrazide),9 the mixed‐valent [Mn III 6 Mn II 6 (O 2 CR) 14 (L) 8 ] (LH 2 = N ‐alkyldiethanolamine), in which Mn III and Mn II ions alternate around a chair‐like wheel,10 and the recently published mixed‐valent “triangular” wheel [Mn II 6 Mn III 6 (mpt) 6 (CH 3 CO 2 ) 12 (py) 6 ] (H 3 mpt=methyl‐1,3,5‐pentanetriol) consisting of alternating homovalent [Mn II 2 ] and [Mn III 2 ] dimers 10g. Interestingly, the saddle‐like topology seen in 1 is rather reminiscent of the mixed‐valent wheel [Mn III 8 Mn II 8 (O 2 CMe) 16 (teaH) 12 ] built using the closely related ligand triethanolamine (teaH 3 ) 6.…”

A Frustrated [Mn18] Wheel-of-Wheels

“…8 In Mn coordination chemistry wheels have presented nuclearities as large as eighty-four, 9 displaying a variety of topologies constructed from chains of single metal ions and polymetallic building blocks. [10][11][12][13] Amongst ligand types, those containing one or more ethanolamine (eaH) moieties ( Figure 1) have proven enormously successful in building a breadth of structurally and magnetically fascinating species. 14 Herein we extend this body of work to include the ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3), which contains three linked eaH units.…”