New heteroleptic complexes (1-8) containing Zn(ii) ion coordinated to an N,N-chelating ligand (the 4,4′-dinonyl-2,2′-bipyridine, bpy-9) and to diketonates L such as tropoloids (Tropolone and Hinokitiol) or 1-phenyl-3-methyl-4-R-5-pyrazolones have been synthesized by using different stoichiometric ratio with respect to the L ancillary ligand. The molecular structure of the bis-tropolonate derivative [(bpy-9)Zn(L)2] 5 has been determined by single-crystal X-ray diffraction. The antitumour activity of all Zn(ii) complexes was tested in vitro against three different human prostate cancer cells: DU145, LNCaP and PC-3. Moreover, their effect on cell survival signalling and/or inhibitors of the PC-3 cell cycle have been analyzed. The results indicate that 1-8 exhibit strong cytotoxic activity against all cell lines affecting key molecules such as p-AKT and p21 waf, involved in the cell proliferation and/or arrest. Zinc(ii) is thus a promising alternative to Pt(ii) ion in the design of new, better performing antitumour agents.