Reaction diastereoselectivity of chiral aminoalcohols/[Co(II)NO3]+ complexes in evaporating ESI nanodroplets: new insights from a joint experimental and computational investigation.

The nature of the ionic species, formed by electrospray ionization (ESI) of Co(NO3)2/CH3OH solns. with a pair of aminoalcs. W and Y, has been investigated by mass spectrometric and computational methods. Collision induced dissocn. (CID) of ions, formally corresponding to the [WYCoNO3]+ structures, yields fragmentation patterns which reflect not only the expected [WYCoNO3]+ connectivity but also that of other isomeric structures. Formation of these latter species is obsd. only in the presence of a tertiary aminoalc., like N-methylpseudoephedrine. The CID patterns are found to be strongly dependent on the chem. form (whether the free aminoalc. or its hydrochloride), the configuration, and the relative concn. of the W and Y aminoalcs. This variability parallels the results of classical MD (mol. dynamics) simulations of the [WYCoNO3]+ adducts which show a drastic alteration of the mech.-dynamical features of the adducts by simply changing the charge state of W and/or Y, their abs. configuration, or by removing the solvent. The present exptl. and computational study confirms the observation of fast stereoselective reactions in ESI nanodroplets before their evapn. and warns against any automatic correlation between the ESI spectrum of an analyte and its structure in soln.