From discrete tricyanovinylene appended 7-azaindole copper(II) paddlewheel to an infinite 1D network: Synthesis, crystal structure and magnetic properties

Abstract

A tricyanovinylene appended 7-azaindole derivative (TCVazaH) was synthesized and used as a ligand for the formation of paddlewheel type complexes ([(TCVaza)4Cu2], 1) upon reaction with CuX2 salts. The role played by the anion X− (NO3−, TfO− or Cl−) on the formation of the copper complexes was studied. Whereas for NO3− or TfO− anions, a discrete complex [(1)(DMF)2] was obtained, in the case of Cl−, a 1D infinite chain 2 ([(1)CuCl2(DMF)4]) was formed. The presence of the same paddlewheel core is the common feature between the discrete binuclear complex and the infinite 1D network. In both cases, the cis-(2,2) regioisomer of the binuclear unit is observed. While, in the discrete species, the axial positions of the Cu centres are occupied by DMF molecules, in the infinite chain, the DMF molecules are replaced by chloride anions leading thus to the formation of an anionic paddlewheel [(1)Cl2]2− unit. The bridging of the latter by [Cu(DMF)4]2+ cationic complexes generates the 1D chain. The study of the magnetic properties of [(1)(DMF)2] by magnetometry using a SQUID magnetometer revealed a strong antiferromagnetic coupling with J=−327(5)cm−1 between the two Cu(II) centres within the paddlewheel complex. For the infinite network 2, the magnetic coupling within a paddlewheel complex is too strong for any coupling with the bridging [Cu(DMF)4]2+ to be observed.