1. Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, United States, Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain, Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, cc 15001, Place Eugène Bataillon 34095, Montpellier, France, and Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520, United States