Observation of Ferromagnetic and Antiferromagnetic Coupling in 1-D and 2-D Extended Structures of Copper(II) Terephthalates.
The reaction between CuCl(2).2H(2)O and disodium terephthalate, Na(2)tp, in aqueous solution simultaneously produces chain, bis(aqua)[&mgr;-(terephthalato-kappaO:kappaO')]copper(II), monohydrate, Cutp(OH(2))(2).H(2)O (1), and layered, bis(aqua)[&mgr;-(terephthalato-kappaO)]copper(II), Cutp(OH(2))(2) (2), structured materials. 1 (C(8)H(10)CuO(7)) belongs to the orthorhombic P2(1)2(1)2 space group [a = 6.3015(4) Å, b = 6.8743(4) Å, c = 22.9972(14) Å, and Z = 4] and incorporates tp in a bridging bis-monodentate binding mode and Cu(II) in a tetragonally elongated octahedron. 2 (C(8)H(10)CuO(6)) which belongs to the orthorhombic Pmc2(1) space group [a = 10.7421(8) Å, b = 7.2339(10) Å, c = 5.7143(13) Å, and Z = 2] incorporates tp in a mono-bidentate binding mode and Cu(II) in a distorted square pyramid. 1 and 2 exhibit axial X-band powder EPR spectra with g( perpendicular) = 2.08, g( parallel) = 2.29 (1) and g( perpendicular) = 2.07, g( parallel) = 2.29 (2) at 300 K. 1 obeys the Curie-Weiss law at high temperatures (theta = -7.2 K) and at low temperatures behaves as 1-D magnetic chains with an exchange-coupling constant of J/k(B)= -9.15 K (H = -2JS(1).S(2)). This material displays a spontaneous moment below 2 K under small applied magnetic fields, consistent with the presence of spin canting. 2 exhibits ferromagnetic interactions with theta = +0.8 K. Along the 1-D chain where coordinated water forms the bridge between metal centers, the coupling between Cu(II) is J/k(B) = +0.6 K. The fit of the magnetic susceptibility for 2 using a molecular field correction, which takes into consideration antiferromagnetic interactions between chains via the tp ligand, yields J'/k(B) = -0.13 K.
Deakin
Laura
L
Department of Chemistry, University of Utah, 315 South 1400 East Rm. Dock, Salt Lake City, Utah 84112-0850.
Arif
Atta M.
AM
Miller
Joel S.
JS