Utilizing bifurcated halogen-bonding interactions with the uranyl oxo group in the assembly of a UO2-3-bromo-5-iodobenzoic acid coordination polymer

Abstract

The synthesis and crystal structure of a new uranyl coordination polymer featuring 3-bromo-5-iodobenzoic acid is described and the luminescent and vibrational properties of the material have been explored. Compound (1), [UO2(C7H3BrIO2)2]n, features dimeric uranyl units chelated and then linked by 3-bromo-5-iodobenzoic acid ligands to form a one-dimensional coordination polymer that is subsequently assembled via bifurcated halogen-bonding interactions with uranyl oxo atoms to form a supramolecular three-dimensional network. The asymmetric, bifurcated halogen-bonding interaction in (1) is notable as it represents the first observation of this synthon in a uranyl hybrid material. Raman and IR spectroscopy showed that halogen-bonding interactions with the uranyl oxo atoms result in small shifts in ϵ1 and ϵ3 frequencies, whereas luminescence spectra collected at an excitation wavelength of 420 nm reveal partially resolved uranyl emission. The supramolecular assembly of a new crystalline uranyl 3-bromo-5-iodobenzoic acid coordination polymer displaying unique bifurcated halogen-oxo interactions is described, and the vibrational and luminescent spectroscopic manifestations thereof have been explored.