Revealing successive steps of deprotonation of L- phosphoserine through 13C and 31P chemical shielding tensor fingerprints

The effects of deprotonation on the (13)C and (31)P chemical shielding tensors of L-O-phosphoserine are revealed by using solid-state NMR spectroscopy and ab initio calculations. The characteristic changes in some principal elements of the (13)C and (31)P chemical shift tensors have been detected during successive steps of deprotonation of carboxyl, phosphate, and amide functional groups. The calculations carried out in a polarizable continuum taking into account the effects of the surroundings have shown their ability to reproduce correctly the changes of the principal values induced by deprotonation and to provide precious information, which is very difficult to obtain experimentally, about the concurrent changes in the orientation of chemical shielding tensors in the molecular frame. The experimentally observed subtle effects related to the deprotonation-induced modifications of intermolecular contacts involving hydrogen bonding as well as the influence of counterions on the (13)C and (31)P principal elements of the chemical shift tensors are also discussed.