Calix[4]arene nitroxide tetraradical and octaradicalThis article is part of a ChemComm ‘Supramolecular Chemistry’ web-based themed issue marking the International Year of Chemistry 2011.Electronic supplementary information (ESI) available: Experimental and computational details, and complete reference 19. See DOI: 10.1039/c1cc11172h

1,3-Alternate calix[4]arene with para-phenylene spacers connecting nitroxide monoradicals and high-spin (S= 1) diradicals provides tetraradical and octaradical scaffolds that possess conformations with slow electron spin relaxation rates (1/T1). Such scaffolds may facilitate tuning of relaxation rates that are more favorable for MRI or DNP applications. [ABSTRACT FROM AUTHOR]