title: Paramagnetic spherical nanoparticles by the self-assembly of persistent trityl radicals.
abstract: Spherical nanoparticles and fibres observable by cryo-electron microscopy are spontaneously formed by the Finland trityl radical at concentrations above 15 mM. These species represent a new class of paramagnetic, metal-free, nanoscale supramolecular materials. Self-association was observed under a variety of experimental conditions, including aqueous solution at room temperature, low temperature frozen glasses and the gas phase. Oligomers formed by at least 5 Finland radicals were detected by ion-mobility mass spectrometry. Magnetic susceptibility data as well as low temperature EPR spectra show coupling between electronic spins in the self-assembled species. Quantum chemical calculations show stacking along the C3 symmetry axis. Nanoparticle formation requires additional lateral packing that can be provided by hydrogen bonding involving the triangular array of carboxylic acid groups leading to the assembly of geodesic spheres.
authors.affiliation: Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Cluster Building, Barcelona Science Park, Baldiri Reixac, 10-12 08028 Barcelona, Spain. mpons@ub.edu.
authors.forename: I
authors.initials: I
authors.lastname: Marin-Montesinos
authors.affiliation: Department of Physical Chemistry, University of Barcelona, Martí i Franquès, 1-11 08028-Barcelona, Spain and Institute of Theoretical and Computational Chemistry, University of Barcelona (IQTCUB), Spain.
authors.forename: J C
authors.initials: JC
authors.lastname: Paniagua
authors.affiliation: Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Cluster Building, Barcelona Science Park, Baldiri Reixac, 10-12 08028 Barcelona, Spain. mpons@ub.edu.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Peman
authors.affiliation: Mass Spectrometry Core Facility, Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac, 10-12 08028 Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Vilaseca
authors.affiliation: Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Luis
authors.affiliation: Department of Physics, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Van Doorslaer
authors.affiliation: Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Cluster Building, Barcelona Science Park, Baldiri Reixac, 10-12 08028 Barcelona, Spain. mpons@ub.edu.
authors.forename: M
authors.initials: M
authors.lastname: Pons