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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)
Author(s) -
Madalan Augustin M.,
Voronkova Violeta,
Galeev Ravil,
Korobchenko Ludmila,
Magull Jörg,
Roesky Herbert W.,
Andruh Marius
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200200619
Subject(s) - chemistry , crystallography , electron paramagnetic resonance , intermolecular force , supramolecular chemistry , crystal structure , stacking , ligand (biochemistry) , intramolecular force , antiferromagnetism , manganese , ion , radical , single crystal , stereochemistry , molecule , nuclear magnetic resonance , biochemistry , physics , receptor , organic chemistry , condensed matter physics
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)