Halogen Bonding Channels for Magnetic Exchange in Cu(II) Complexes with 2,5-Di(methylthio)-1,3,4-thiadiazole

Copper(II) complexes with 2,5-bis(methylthio)-1,3,4-thiadiazole (tda) formulated as [Cu(tda)(n)X-2] (n=2, X=Cl-, Br-, C2N3-; n= 1, X=C2N3-) have been isolated and fully characterized. The crystal structures of all compounds have been determined using single-crystal X-ray diffraction (SCXRD). A study of the magnetic susceptibility in the range 1.77-300 K has shown that magnetic properties of the [Cu(tda)(2)Cl-2] and [Cu(tda)(2)Br-2] complexes match those of 1D chains of antiferromagnetically-coupled Cu2+ ions. The intrachain interaction J in [Cu(tda)(2)Cl-2] turns out to be similar to 1.2 times weaker than in its bromide analogue. In its turn, [Cu(tda)(2)(C2N3)(2)] exhibits J being an order of magnitude smaller and of the opposite ferromagnetic sign. Halogen bonding (HB) between adjacent complexes is much stronger than the H-bonds or pi-pi interactions between tda ligands according to the DFT calculations.