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)

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)