A WEAK ANTIFERROMAGNETIC INTERACTION BETWEEN MN2+ CENTERS THROUGH A TCNQ COLUMN - CRYSTAL-STRUCTURES AND MAGNETIC-PROPERTIES OF [MN-II(TPA)(TCNQ)(CH3OH)](TCNQ)(2)-CENTER-DOT-CH3CN, [MN-II(TPA)(MU-O2CCH3)]2(TCNQ)(2)CENTER-DOT-2CH(3)CN, AND [MN-II(TPA)(NCS)(2)]CENTER-DOT-CH3CN (TPA=TRIS(2-PYRIDYLMETHYL)AMINE)

Reaction of Mn(CH3COO)(2).4H(2)O and Mn(PF6)(2).4H(2)O with tpa and Li(TCNQ) (tpa = tris(2-pyridylmethyl)-amine, TCNQ = tetracyanoquinodimethane) in acetonitrile-methanol solution gave [Mn-II(tpa)(mu-O-2-CCH3)](2)(TCNQ)(2).2CH(3)CN (1) and [Mn-II(tpa)(TCNQ)(CH3OH)](TCNQ)(2).CH3CN (2), respectively. Crystal structures and magnetic properties have been studied in comparison with those of [Mn-II(tpa)(NCS)(2)].CH3CN (3). Complex 1 crystallizes with an inversion center located in the center of the bis(mu-acetato)dimanganese(II) core, and TCNQ units form diamagnetic dimers which stack to form a column structure. The acetates bridge the two Mn(II) centers in a syn-anti mode, with a Mn-Mn separation of 4.145(1) Angstrom, and mediate a weak antiferromagnetic interaction with J =-0.972(6) cm(-1) (where H =-2JS(1).S-2). In 2, four crystallographically independent TCNQ ions, called A, B, C, and D, respectively, were revealed in the unit cell, and anions C and D are located on the crystallographic inversion center. Anions A and B form dimeric units (AA and BB), respectively, and these dimers respectively stack with C and D to form columns (...AACAA...) and (...BBDBB...). The [Mn-II(tpa)(CH3OH)] unit was directly bound by the anion B, and as a result, two manganese atoms were connected through two B anions with a Mn-Mn separation of 15.397(2) Angstrom. The temperature dependence of the magnetic susceptibility of 2 has shown an antiferromagnetic behavior; that is, T-chi m values start to gradually decrease from 4.4 emu K mol(-1) at 100 K to 1.76 emu K mol(-1) at 2 K. In 3, a manganese ion has a six-coordinate geometry, which is similar to that of 2, and the closest Mn-Mn separation is 6.8873(9) Angstrom. Magnetic susceptibility measurement for 3 has revealed the Curie behavior down to 4 K and this leads one to conclude that zero-field splitting for the manganese ion and an antiferromagnetic dipole-dipole interaction between manganese ions with a Mn-Mn separation longer than 6.8873(9) Angstrom are negligible down to 4 K. By considering the magnetic behavior of 3, the antiferromagnetic behavior of 2 is concluded to be due to the antiferromagnetic interaction between two manganese ions (15.397(2) Angstrom separation) through TCNQ columns (...BBCBB...), where the anions are antiferromagnetically coupled to be diamangetic, and the exchange coupling constant (J) was estimated to be -0.197(6) cm(-1). Crystal data: [Mn-II(tpa)(mu-O-2-CCH3)](2)(TCNQ)(2).2CH(3)CN (1), monoclinic, space group P2(1)/n, a = 18.798(6) Angstrom, b = 19.260(3) Angstrom, c = 8.973(2) Angstrom, beta = 99.03(2)degrees, V = 3208(1) Angstrom(3), Z = 2, and R = 0.059 (R(w) = 0.059) for 4185 data with \F-o\ > 3 sigma(F-o);[Mn-II(tpa)(TCNQ)(CH3OH)](TCNQ)(2).CH3CN(2), triclinic, space group <P(1)over bar>, a = 9.937(3) Angstrom, b = 31.608(4) Angstrom, c = 8.207(2) Angstrom, alpha = 96.33(1)degrees, beta = 92.91(2)degrees, gamma = 89.19(2)degrees, V = 2559(1) Angstrom(3), Z = 2, and R = 0.045 (R(w) = 0.058) for 5074 data with \F-o\ > 6 sigma(F-o); [Mn-II(tpa)(NCS)(2)].CH3CN (3), orthorhombic, space group P2(1)2(1)2(1), with a = 13.271(2) Angstrom, b = 15.717(2) Angstrom, c = 11.800(2) Angstrom, V = 2461.2(5) Angstrom(3), Z =