Two new heteroleptic Zn(II) complexes of the 4,4'-bis(hydroxymethyl)-2,2'-bipyridine have been synthesized by using different stoichiometric ratios of tropolone. In an attempt to induce the formation of metal complex co-crystals, liquid assisted solid state reaction followed by solvent crystallization has been conducted by using the new Zn(II) tropolonate derivatives 1 and 2 with saccharin. The novel Zn(II) species obtained exhibits different structures and properties with respect to their precursors, due to a hydrogen exchange between saccharin and the tropolonate coordinated ligand.