Laser production of gas phase complexes of metal α-aminophosphonic acid mixtures and their role in chiral recognition

Abstract

Clusters between first-group metal ions and chiral α-aminophosphonic acids have been readily generated by Pulsed Laser Ablation (PLA) and by Electrospray Ionization (ESI) and their fragmentation investigated by mass spectrometry. The complexes studied have the general formula [Me(I)Cl2]+, where Me(I) is H, Li, Na, or K, C is (R)-(—)-(1-aminoethyl) phosphonic acid (ER) and (S)-(+)-(1-aminoethyl) phosphonic acid (ES), (1R)-(+)-(1-amino-2-methylpropyl) phosphonic acid (PR) and (1S)-(—)-(1-amino-2-methylpropyl) phosphonic acid (PS), (1R)-(-)-(1-amino-hexyl) phosphonic acid (HR) and (1S)-(+)-(1-amino-hexyl) phosphonic acid (HS), o-phospho-L-serine (SS) and o-phospho-D-serine (SR), and L is a reference α-aminophosphonic acid (E, P, H or S) of defined configuration. Collision induced dissociation (CID) of diastereomeric [Me(I)Cl2]+ complexes leads to fragmentation patterns characterized by [Me(I)Cl]+/[Me(I)L2]+ abundance ratios which depend upon the configuration of solute C. These different spectral features were correlated to the different stability of the diastereomeric [Me(I)CRL]+ and [Me(I)CSL]+ complexes in the gas phase.