Synthesis, crystal and molecular structure, and spectral properties of guanidinium salt of complex uranyl 2-methoxybenzoate

Abstract

A crystalline uranyl 2-methoxybenzoate, [C(NH₂)₃][UO₂L₃]·H₂O, was synthesized. Its structure was determined by single crystal X-ray diffraction, and the electronic and IR spectra were recorded. The coordination number of the U atom is 8, with methoxyl O atom not involved in coordination bonding with uranyl. The structure contains a system of hydrogen bonds with water molecule of crystallization and guanidinium cation acting as proton donors. The electronic absorption spectrum of the crystalline complex has a pronounced vibronic structure, whereas in the solution spectrum all the lines are strongly broadened. This may be due to dissociation of the complex anion in solution, which leads to superposition of several spectra. In the IR spectrum, there is a set of band characteristic of guanidinium cations. The uranyl group in [C(NH₂)₃][UO₂L₃]·H₂O has almost symmetrical structure. Therefore, only the band of its antisymmetric vibrations is observed in the IR spectrum.