Infrared spectroscopy of multiply charged metal ions: methanol-solvated divalent manganese 18-crown-6 ether systems.

We have developed an electrosonic spray ionization source to successfully generate divalent Mn(2+)(18-crown-6)(CH(3)OH)(1-3) complexes in the gas phase. These complexes have been investigated using infrared predissociation spectroscopy in both the CH and OH stretching regions and with density functional theory calculations. To resolve complications from overlapping bands in the CH stretching region due to CH(3)OH and 18-crown-6 CH stretching modes along with strongly perturbed OH stretching modes, we have used d(1) and d(4) methanol substitution. For n = 1, the Mn(2+)...18-crown-6 geometry is highly distorted from its gas-phase neutral configuration in order to maximize favorable electrostatic interactions between the 18-crown-6 macrocyclic oxygens and Mn(2+). For n = 2 and 3, CH(3)OH...CH(3)OH and CH(3)OH...18-crown-6 interactions compete with the Mn(2+)...18-crown-6 interaction, as evidenced by intense hydrogen-bonded OH stretching modes shifted over 500 cm(-1) to lower frequency.