The resin-supported boron-scorpionate ligand, KTp' (Tp'= {HB(resin-Benzotriazole) (pyrazolyl*)2}), readily binds nickel(II) as a tridentate chelate from simple salts in methanol, signified by a green coloring of the beads (Inorg. Chem. 2011  p.1). These nickel coordination complexes demonstrate significant histidine affinity under mildly basic conditions. With triethylamine present, the individual selectivity of Bead-Tp'NiNO3 has also been tested for other amino acids (AA = serine and lysine) using 1H NMR peak integration in which amino acid signals were integrated relative to an internal standard (13% v/v CH2Cl2 in CCl4 sealed in a glass capillary). For each trial, the Bead-Tp'Ni(His)n complex produced a noticeable and consistent bleaching of the green color. Re-addition of Ni(NO3)2 to bead-Tp'Ni(His)n  consistently regenerated the green color. To confirm that the changes in the histidine spectrum were solely due to bead uptake of the His, the effect of free nickel(II) on free His was tested as a control experiment by 1H NMR. Bead recyclability for all testing has remained consistent in this work. The testing of Bead-Tp'NiNO3 for selectivity among various nitrogen-rich amino acids should expand the utility of this established scorpionate class of ligands to broad applications of amino acid selectivity for protein sensing and purification.

Evaluating the effectiveness of supported nickel scorpionates to select for specific amino acids

247th National Meeting (2014)

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