Dipicolylamine-Based Fluorescent Probes and Their Potential for the Quantification of Fe in Aqueous Solutions.

We have synthesized two ligand systems, N(SO)(R)dpa (L1) and N(SO)(R)dpa (L2), where R = biphenyl and R = azobenzene, which are sulfonamide derivatives of the NNN-donor chelating dipicolylamine. Both L1 and L2 can be used as sensors for detecting Fe and are highly sensitive and selective over a wide range of common cations. Time-dependent density functional theory (TDDFT) calculations confirmed that the key excitations of L2 and the [Fe(L2)(HO)] model complex involve -R-unit-based π and π* charge transfer.