Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen

The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1'H-indol-3'-yl)-maleimide and 4-methyl-3-(1'H-indol-3'-yl)maleimide, are investigated and the bromo derivative is crystallized and its x-ray structure is determined. DFT calculations indicated that HOMO-1 to LUMO excitation is mainly responsible for the charge transfer character and that this transition changes its character drastically when Zn-cyclen complexation occurs.