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

<jats:title>Abstract</jats:title>Copper(II) complexes with 2,5‐bis(methylthio)‐1,3,4‐thiadiazole (tda) formulated as [Cu(tda)<jats:sub>n</jats:sub>X<jats:sub>2</jats:sub>] (n=2, X=Cl<jats:sup>−</jats:sup>, Br<jats:sup>−</jats:sup>, C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub><jats:sup>−</jats:sup>; n= 1, X=C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) 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)<jats:sub>2</jats:sub>Cl<jats:sub>2</jats:sub>] and [Cu(tda)<jats:sub>2</jats:sub>Br<jats:sub>2</jats:sub>] complexes match those of 1D chains of antiferromagnetically‐coupled Cu<jats:sup>2+</jats:sup> ions. The intrachain interaction <jats:italic>J</jats:italic> in [Cu(tda)<jats:sub>2</jats:sub>Cl<jats:sub>2</jats:sub>] turns out to be ∼1.2 times weaker than in its bromide analogue. In its turn, [Cu(tda)<jats:sub>2</jats:sub>(C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>] exhibits <jats:italic>J</jats:italic> 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 π‐π interactions between tda ligands according to the DFT calculations.