The pKa value of the proximal water molecule trans to a high-valent MnVO porphyrin: towards the control of reactivity by pH

Abstract

The high-valent manganese-oxo species of Mn-TMPyP4 porphyrin interacts in the minor grooves of AT-rich regions of DNA and mediates hydroxylation of C–H bonds of deoxyribose leading to DNA break. The reaction was observed at different pHs. It is shown that the hydroxylation was not efficient at low pH (pH 6) while it worked well at higher pH (pH 8). Deprotonation of the coordinated water molecule, trans to the manganese-oxo entity, into a hydroxide anion drives high-valent manganese-oxo porphyrin toward hydroxylation at pH > 7.