A new type of anionic metal dicyanamide extended networks through [Cu(N4-macrocycle)]2+ cation templation. Structure and magnetic properties.

Abstract

Two isomorphous anionic metal dicyanamide extended systems [Cu(pCTH)][M(dca)(4)] (M = Mn(II), Co(II); dca = dicyanamide; pCTH = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetrazacyclotetradecane-4,11-diene) have been prepared through [Cu(pCTH)](2+) templation and characterized by X-ray crystallography and magnetic measurements. In these complexes, the [M(dca)(4)](2)(-) anions form 2D (4,4) distorted square-gridlike sheets in which each elongated octahedral M(N(dca))(6) metal center is connected to four neighboring ones through single dicyanamide bridges in equatorial positions. [Cu(pCTH)](2+) cations lie between the sheets and display weak bonding interactions with the axial dicyanamide ligands on the M centers of two neighboring [M(dca)(4)](n)()(2)(n)()(-) sheets, thus leading to a 3D heterometallic network. Variable-temperature magnetic measurements reveal weak antiferromagnetic interactions between metal centers across mu(1,5)-dicyanamide bridging ligands. For the cobalt(II) compound, the experimental data for T > 30 K match well with the calculated curve by taking into consideration the spin-orbit coupling effect for the (4)T(1g) ground state of the cobalt(II) and an axial distortion of the octahedral geometry. No long-range magnetic order was observed in these compounds above 2 K.