A New Type of Anionic Metal Dicyanamide Extended Networks through [Cu(N4-macrocycle)]2+ Cation Templation. Structure and Magnetic Properties

Two isomorphous anionic metal dicyanamide extended systems [Cu(pCTH)][M(dca)4] (M = Mn(ll), Co(ll); 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(Ndca)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^2n- sheets, thus leading to a 3D heterometallic network. Variable-temperature magnetic measurements reveal weak antiferromagnetic interactions between metal centers across mu1,5-dicyanamide bridging ligands. For the cobalt(ll) 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 4T1g ground state of the cobalt(ll) and an axial distortion of the octahedral geometry. No long-range magnetic order was observed in these compounds above 2 K.