Quantum mechanical investigation of aqueous desferrioxamine B metal complexes: trends in structure, binding, and infrared spectroscopy.

A systematic density functional theory study supported by extended X-ray absorption fine structure (EXAFS) and infrared spectroscopic data was conducted to elucidate how structure and vibrational spectra of aqueous desferrioxamine B (DFOB) metal complexes vary with the metal ion identity. Structural parameters derived from EXAFS analyses and trends in metal binding constants are well reproduced and validated by the applied computational model. Vibrational mode analysis guides determination and recognition of crucial structure- and metal-sensitive infrared marker bands. The key marker bands, CO and CN stretching modes, dominate the infrared spectra in the 1400-1650cm(-1) region. The modes are sensitive to the stability and size of the metal core (first coordination shell) and indicative of its deformation from the octahedral symmetry. The results shed light on the fundamental structural and electronic factors that control metal binding by siderophores, and drive their potentially rich and largely unexplored interactions with trace metals.