Two new Zn(II) complexes containing guanidinium groups, [Zn(L(1))Cl(2)](ClO(4))(2).H(2)O.CH(3)OH (1) and [Zn(L(2))Cl(2)](ClO(4))(2).0.5H(2)O (2), were synthesized and characterized (L(1)=5,5'-di[1-(guanidyl)methyl]-2,2'-bipyridyl bication and L(2)=6,6'-di[1-(guanidyl)methyl]-2,2'-bipyridyl bication). Both complexes are able to catalyze bis(p-nitrophenyl) phosphate (BNPP) hydrolysis efficiently. Obtained kinetic data reveal that both 1 and 2 show nearly 300- and 600-fold rate enhancement of BNPP hydrolysis, respectively, compared to their simple analogue without the guanidinium groups [Zn(bpy)Cl(2)] (bpy=2,2'-bipyridy) (3). Enhanced acceleration for cleavage of BNPP could be attributed to cooperative interaction between the Zn(II) ion and the guanidinium groups by electrostatic interaction and H-bonding. Studies on inhibition of sequence-specific endonucleases (DraI and SmaI) by complexes show that 1 and 2 are able to recognize nucleotide sequence, -TTT;AAA-, and highly effectively cleave the plasmid DNA in the presence of hydrogen peroxide, while 3 has no specific binding to the DNA target sequences and only shows low DNA cleavage activity.