Strongly Isolated Ferromagnetic Layers in Poly-trans-μ-dichloro- and Poly-trans-μ-dibromobis(1-(2-chloroethyl)-tetrazole-N⁴)copper(II) Complexes

Abstract

Two new isostructural compounds, dichlorobis(1-(2-chloroethyl)tetrazole)copper(II) (1) and dibromobis(1-(2-chloroethyl)tetrazole)copper(II) (2), have been prepared. The synthesis, characterization, and spectral and magnetic properties as well as the crystal and molecular structures of 1 and 2 have been studied. Both complexes form two-dimensional, distorted square grid planes of copper and halides, distinctly separated by layers of tetrazole ligands. The differential (ac) magnetic susceptibility, chi = (deltaM/deltaH)(T), and magnetization M(H) of both complexes have been studied as a function of temperature and field. The compounds possess a ferromagnetic interaction within the isolated copper-halide layers (J/k(B) = 8.0 K, J/k(B) = 10.2 K, respectively, for the chloride and the bromide, and T(c) = 4.75 K, T(c) = 8.01 K). The magnetic coupling J'/k(B) between the different layers is found to be very weak (|J'/J| <or= 2 x 10(-2)).

Linkage isomers of dibromobis(1-(2-methoxyethyl)tetrazole)copper(ii) containing either a bromide or a unique tetrazole bridge

“…The solvent effect observed here, whereby two different linkage isomers of [Cu(teeOMe) 6 with side chains of equal length: L = 1-butyltetrazole and with longer side chains: L = 1-pentyltetrazole and 1-hexyltetrazole) all resulted in complexes with magnetic properties resembling those compound 2. No compounds comparable in structure and magnetism to compound 1 have been identified.…”

“…However, since all other bis(1-alkyltetrazole)copper() halides of which the structure has been solved 3-6 adopt crystal structures containing two-dimensional grids of halide-bridged copper ions with axial N donor ligands, it is plausible that 2 adopts a similar structure. This is especially likely because the magnetic properties of 2 are almost identical to the magnetic behaviour 6 observed in e.g. [Cu(teec) 2 Br 2 ] n .…”

“…1) and discussed below. Crystal data are provided in Table 1 and selected bond distances and angles for all three structure determinations are presented in Tables 2 and 3. The structure is built up from centrosymmetric square trans-[Cu(teeOMe) 2 6 The N(2) atoms of the tetrazole rings of two neighbouring [Cu(teeOMe) 2 Br 2 ] units occupy the axial positions above and below the square plane, completing a tetragonally distorted octahedron with bond angles ranging from 88.62(4) to 91.76(6)Њ. The axial Cu(1)-N(2) distance of 2.781(2) Å is considerably longer than normal coordination bonds: however, in view of the bond angles involving N(2), the copper ion and the other donor atoms, which are close to 90Њ, the Cu(I)-N(2) bond may be regarded as semi-coordinated.…”

“…10.5-16 K) and is in good agreement with the critical temperature observed for [Cu(teec) 2 Br 2 ] n (T c = 8.0 K). 6 The fact that the T c value is much lower than the Curie-Weiss temperature θ can be ascribed to the pronounced two-dimensional character of this material. Because sufficiently large single crystals were not available, all measurements were performed on polycrystalline samples: therefore no distinction could be made between the different crystal axes.…”

“…µ-1,2-η 2 Bridges are observed in e.g. [Ag (5-(trifluoromethyl) 6 ]. NMR and infrared measurements have indicated that 1-phenyltetrazole, 1-methyltetrazole and 1-cyclohexyltetrazole also form µ-3,4-η 2 bridges in molybdenum carbonyl compounds.…”