This invention concerns a coordination complex and salts and optically resolved enantiomers thereof, of the formula (R).sub.3 --M, wherein R comprises 1,10-phenanthroline or a substituted derivative thereof, M comprises a suitable transition metal, e.g. ruthenium(II) or cobalt(III), and R is bonded by M by a coordination bond.
The complexes of this invention are useful in methods for labeling, nicking and cleaving DNA. The lambda enantiomer of complexes of this invention is useful in methods for specifically labeling, detecting, nicking and cleaving Z-DNA.
The complexes may also be used in a method for killing tumor cells and may be combined with a pharmaceutically acceptable carrier to form a pharmaceutical composition for the treatment of tumor cells in a subject. The invention further concerns methods for treating a subject afflicted with tumor cells.