Transition metals and their complexes have an important impact on chemistry and are found in many application in life in general. Ruthenium and rhodium are two members of noble metals and proved to be suitable for anticancer activity. With the aim of changing the coordination environment in ruthenium and rhodium complexes, this thesis presents a series of Ru(II) polypyridyl and Rh(III) pincer-type complexes. All new Ru(II) and Rh(III) complexes were characterized by NMR spectroscopy, ESI-MS spectrometry and UV-Vis spectrophotometry . For some of the complexes a single crystal X-ray crystallography was performed. The substitution reactions of Ru(II) and Rh(III) complexes with mononucleotides, oligonucleotides and amino acids were studied quantitatively by UV-Vis spectroscopy. Measurements of the activation enthalpies and entropies for all synthesized complexes are supporting an associative mechanism for the substitution process. NMR spectroscopy studies were performed on some Ru(II) complexes where after the hydrolyses of the metal-Cl bond the complexes are capable to interact with guanine derivatives forming monofunctional adducts via N7 atom. The interactions of Ru(II) and Rh(III) complexes with fully complementary 15-mer and 22-mer duplexes of DNA and fully complementary 13-mer duplexes of RNA were studied by UV-Vis spectroscopy. The interactions of ruthenium(II) and rhodium(III) complexes with calf thymus and herring testes DNA were examined by absorption using UV-Vis spectroscopy, fluorescence emission spectral studies by ethidium bromide displacement studies and viscosity measurements. ; eng