Three new unsymmetrical compartmental dinucleating ligands, 4‐bromo‐2‐(4‐methylpiperazin‐1‐ylmethyl)‐6‐{2‐(1‐piperidyl)ethyl}aminomethylphenol (HL1), 4‐bromo‐2‐(4‐methylpiperazin‐1‐ylmethyl)‐6‐{2‐(morpholin‐4‐yl)ethyl}aminomethylphenol (HL2), and 4‐bromo‐2‐(4‐methylpiperazin‐1‐ylmethyl)‐6‐{2‐(thiomorpholin‐4‐yl)ethyl}aminomethylphenol (HL3), have been synthesized in order to model the active site of type 3 copper proteins. The dicopper(II) complexes of these ligands give first hints about the influence of a thioether group close to the metal site. The bromophenol‐based ligands have one piperazine arm and one other bidentate arm in positions 2 and 6 of the phenolic ring, respectively. With each ligand a dinuclear copper(II) complex was prepared and structurally characterized. The copper ions were found to have square pyramidal environments and a mixture of endogenous phenoxo and exogenous acetate bridging. The influence of a heteroatom in one arm of the ligand on catecholase activity and speciation in solution was studied by UV/Vis spectroscopy, ESI‐MS experiments and, DFT calculations. Helpful heteroatoms: Model complexes for type 3 copper proteins that contain compartmental bischelating ligands have been prepared (see structure). Incorporation of heteroatoms into a side arm of a phenol‐based ligand, especially in the form of a thioether, was found to increase the turnover number for the oxidation of catechols.