Exchange Interactions at the Supramolecular Level − Synthesis, Crystal Structure, Magnetic Properties, and EPR Spectra of [Mn(MAC)(TCNQ)2] (MAC = Pentaaza Macrocyclic Ligand; TCNQ·− = Radical Anion of 7,7,8,8-Tetracyano-p-quinodimethane)
✍ Scribed by Augustin M. Madalan; Violeta Voronkova; Ravil Galeev; Ludmila Korobchenko; Jörg Magull; Herbert W. Roesky; Marius Andruh
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 120 KB
- Volume
- 2003
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
The reaction between [Mn(MAC)(H~2~O)~2~]Cl~2~·4H~2~O and LiTCNQ (MAC = 2,13‐dimethyl‐3,6,9,12,18‐pentaazabicyclo[12.3.1]octadeca‐1(18),2,12,14,16‐pentaene) affords a complex with the formula [Mn(MAC)(TCNQ)~2~] (1), whose crystal structure has been determined. Its structure consists of neutral mononuclear entities. The manganese(II) ion is heptacoordinated, with a pentagonal bipyramidal geometry. The apical positions are occupied by the TCNQ·^−^ radicals, while the macrocyclic ligand is coordinated at the equatorial positions. The seven Mn−N distances range from 2.273(3) to 2.301(6) Å. The strong intermolecular π−π stacking interactions between the TCNQ radicals (3.2 Å) leads to weave‐like infinite chains, which propagate along the crystallographic c axis. The cryomagnetic investigation of 1 revealed a weak intermolecular antiferromagnetic coupling of the Mn^2+^ ions (J = −0.18 cm^−1^), which is mediated by the diamagnetic (TCNQ)~2~^2−^ pairs resulting from the stacking interactions in the crystal. The intermolecular exchange interaction between the Mn^2+^ ions was further confirmed by variable temperature EPR spectroscopic measurements [|J| = 0.15(5) cm^−1^], which have been carried out in both the X and Q bands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)