**2. Materials and Methods**

All reagents and solvents, including **2**, were obtained from commercial suppliers and were of at least reagen<sup>t</sup> grade, and used as received, unless otherwise stated. The ligands **1** and **3–6** were prepared by modified literature procedures [53–58]. Full experimental, FT-IR spectroscopic details and the single-crystal [59–66] and powder X-ray experimental [67–69], and structure refinements for **1**·CuBr**–6**·CuBr (CCDC numbers: 2001484–2001491) are given in the Supporting Information.
