Recent experiments on a pH-responsive, luminescent, dimetallic Eu(III) complex showed that this compound exhibits pH dependent luminescence decay over a biologically relevant pH range from 4 to 8 (J.Am.Chem.Soc., 134, 17372). Initial theoretical calculations were performed on the homo-di-Eu(II) structure to obtain optimized geometries for deprotonated and singly protonated structures on this complex’s many protonation sites. In the present work, we present further quantum mechanical calculations on di-Eu(III) complexes, as well as complexes conataining di-La(III) and di-Lu(III) ions to determine the pKa’s of all ionizable sites. The calculations have been carried out at the DFT/SDD(all) level of theory in gas phase and implicit solvent (SMD). A series of 22 singly protonated, doubly protonated, and triply protonated systems, has been investigated for each dimetallic complex. The pKa results and their implications regarding the experimentally observed broad pH range will be discussed.

Computational determination of pKas on pH-responsive and luminescent dimetallic lanthanide complexes

251st National Meeting (2016)

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