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Mixed-ligand complexes featuring a carboxylato ligand and bidentate chelate N,N′-donor ligands along with a single halogenido ligand are rarely subjected to studies despite their interesting physical, chemical and biological properties. A direct synthesis involving non-steroidal anti-inflammatory drugs flufenamic acid and niflumic acid and sterically hindering N,N′-donor ligands (neocuproine and 2,2′-biquinoline) has been used to prepare mononuclear mixed-ligand zinc complexes with a composition of [ZnCl(<i>flu</i>)(<i>neo</i>)] (<b>1A</b> and <b>1B</b>) and [ZnCl(<i>nif</i>)(<i>biq</i>)] (<b>2</b>). Single-crystal X-ray diffraction data have shown that the carboxylate binding mode differs in the two polymorphs <b>1A</b> and <b>1B</b>, which form molecules of same composition, and the deviations in molecular geometry are further reflected in their supramolecular structures. The inter- and intramolecular interactions and their contributions to the stability of the crystal structures has been investigated by Hirshfeld surface analysis. The spectral properties of the prepared complexes in solid-state and solution have been analyzed. Additionally, the interaction with the biomacromolecules (fish sperm DNA, human and bovine serum albumins), studied by fluorescence assays, showed a stronger binding of <b>1A</b> and <b>1B</b> in comparison with <b>2</b>.