Anionic 3D cage networks self-assembled by iodine and V-shaped pentaiodides using dimeric oxoammonium cations produced in situ as templatesElectronic supplementary information (ESI) available: UV-Vis spectra of TEMPO with I2 in chloroform (Fig. S1) and n-hexane (Fig. S2), possible reaction processes for some relevant fragments in ESI-MS (Scheme S1) and crystallographic data in CIF. CCDC reference numbers 917822 and 929899. For ESI and crystallographic data in CIF or other electronic format see D

A novel co-crystal, [(BTEMPO) 2 2+ 4I 2 2I 5 ] (BTEMPO + = 4-benzoyloxy-2,2,6,6-tetramethylpiperidinyl-1-oxoammonium cation), was successfully constructed using iodine and 4-benzoyloxy-2,2,6,6-tetramethylpiperidinyl-1-oxy free radical (BTEMPO) as starting materials and was well characterized by XRD, Raman and calculation. The co-crystal possesses a fascinating 3D anionic cage structure formed by V-shaped-pentaiodides and iodine via multiple halogen bonding and on a template of dimeric (BTEMPO) 2 2+ cations. The cationic dimers are held together by a pair of reversed CHO&z.dbd;C hydrogen bonds and stabilized the 3D cage structure by CHI hydrogen bonds between methyl-protons of BTEMPO + and iodine in the framework. The reaction mechanism of producing BTEMPO + and I 5 is proposed and verified by UV-Vis spectroscopy and ESI-MS, which initially goes through a halogen bonding complex between iodine and BTEMPO free radical and then Milliken inner charge transfer and charge separation reaction. UV-Vis absorption spectroscopy confirms the halogen bonding complex between I 2 and BTEMPO with a formation constant of 6.94 M 1 and a 1:1 stoichiometry in chloroform. The ESI-MS directly led to observation of the less stable intermediates in the mechanism. It is believed that the mechanism proposed here is helpful in understanding the interactions between I 2 and organic electron donors, which are debated frequently, and fills the gaps in the reaction mechanism of I 2 with free radicals or analogues. A novel 3D cage network assembled by the reaction of I 2 with BTEMPO free radicals using dimeric BTEMPO + cations produced in situ as template.