We present the effect of the DNA damage efficiency by excitation wavelengths above 700 nm within d-d transition bands Of (L-lysine) (dppz) Cu(II) complexes. Our results show significant DNA cleavage between 700 and 755 nm. The efficiency of photosensitized DNA cleavage and quantum yield of singlet oxygen production at different excitation wavelengths have been determined to gain insight into the involvement of the d-d band in the DNA damage process. Time-dependent density functional (TD-DFT) calculations were performed to understand the influence of the metal to L-lysine transition on the d-d bands of the Cu(II) complex-DNA moiety. It is found that the involvement of d-d transition in the reaction pathway of singlet oxygen formation seems to play an important role in the DNA cleavage efficiency using light of wavelength above 700 nm. (c) 2006 Elsevier B.V. All rights reserved.