Solid-State Photoconversion of a Discrete Mixed Iodine(I) System to a 1D Polymer

Abstract

The first example of a mixed halogen(I) complex (2), containing three distinct iodine(I) moieties ([N―I―N]⁺, O―I―N, and [O―I―O]⁻) within the same structure, was synthesized with 4-styrylpyridine (4-stypy) and 3,4,5,6-tetrafluorophthalate as the stabilizing Lewis bases. This complex was observed to be in equilibrium with its respective bis(OIN) complex (1a), with isolated samples of 2 also being found to convert to 1a in solution. Upon UV irradiation of 2, a single-crystal-to-single-crystal [2 + 2] cycloaddition reaction was observed, converting the discrete salt 2 to the 1D polymer 5. Complex 5 retained all the iodine(I) moieties from prior to photoconversion and represents the first example of nondestructive photoconversion of a halogen(I) complex. To facilitate comparisons to 2 and 5, several additional closely related iodine(I) complexes were synthesized, with the iodine(I) complexes characterized by NMR (¹H, ¹H-¹⁵N HMBC) and SCXRD, as well as by Raman and IR spectroscopy for 2, 5, and their close structural analogue 1a.