Laser Production of Gas-Phase Complexes of Metal alfa-Aminophosphonic Acid Mixtures and their Role in Chiral Recognition

Clusters between Group IA metal ions and chiral .alpha.-aminophosphonic acids were readily generated by Pulsed Laser Ablation (PLA) and by Electrospray Ionization (ESI) and their fragmentation was studied by mass spectrometry. The complexes studied have the general formula [{Me(I)}(C)(L)2]+, 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-aminohexyl)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 ref. .alpha.-aminophosphonic acid (E, P, H or S) of defined configuration. Collision induced dissocn. (CID) of diastereomeric [{Me(I)}(C)L2]+ complexes leads to fragmentation patterns characterized by [{Me(I)}(C)L]+/[{Me(I)}L2]+ abundance ratios which depend upon the configuration of solute C. These different spectral features were correlated to the different stabilities of the diastereomeric [{Me(I)}(CR)L]+ and [{Me(I)}(CS)L]+ complexes in the gas phase.