Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, 06269-3060, U.S.A. * To whom correspondence should be addressed. E-mail: [email protected]. Phone: 860-486 2797.

Pyridine (Sigma-Aldrich, 99%) was stored on freshly activated 3 Å molecular sieves (Merck). Deionized water (15 MΩ ... of finely ground material in analytical grade absolute ethanol onto Quantifoil R ...