The interactions of methylxanthine bases with metal ions are of major biological interest and are important in bioinorganic chemistry. One of these bases is 8-chlorotheophylline (Ctp), which exhibits high stimulant action. Here, the metal complexation reactions of Ctp with Cr(III), Mn(II), Co(II), Ni(II), and Cu(II) ions were investigated, in a 1:2 molar ratio and in basic media. All of the prepared complexes were confirmed using elemental analysis, magnetic moment measurements, molar conductance, thermal analysis, and UV–Vis., IR, and Raman spectroscopies. Spectroscopic results revealed direct cation interactions for all of the metal ions via the deprotonated N7 atom of Ctp. The biological activity of the complexes was examined to determine the effect of chelation on the bioactivity of Ctp. It was observed that free Ctp possesses very low inhibitory activity towards several bacteria and fungi. However, the potency of its Cr(III)-complex exceeded that of the standard drug Ciprofloxacin against all of the tested bacterial strains, and the potency of this complex was 28% and 11% higher than those of the standard drug Fluconazole against the Aspergillus flavus and Penicillium Sp fungal strains, respectively.

The free drug 8-chlorotheophylline (Ctp) possesses very low inhibitory activity towards the fungal strain Aspergillus flavus. This work demonstrates that binding to metal ions influences the drug activity to various extents, showing moderate activity with Co(II) ions, strong activity with Mn(II) ions, and remarkable growth inhibition with Cr(III) ions. The potency of the Cr(III)-Ctp complex is 28% greater than that of the standard drug Fluconazole against this fungal strain.