Two new complexes of Ti and Zr were synthesized with 3-hydroxyflavone bidentate ligand and investigated in homogeneous ethylene polymerization. Both complexes were characterized by UV-VIS, H-1 and C-13 NMR, and electrochemical studies. The geometries and energies of all possible isomeric species were studied by full unconstrained optimizations performed at Density Functional Theory (DFT) level. The polymerization reactions were performed at different experimental conditions with methylaluminoxane (MAO), as the cocatalyst. Both complexes were active in ethylene polymerization in all the conditions used. However, zirconium complex showed the best activity comparing to the titanium complex at 2500 Al/M ratio. The polymers obtained were high density polyethylene with ultra high molecular weights. (C) 2013 Elsevier B.V. All rights reserved.