Ionic Interaction\nEffects on the Structure and Dynamics\nof Orthoborate Ionic Materials

A series of orthoborate-based ionic materials of bis(glycolato)borate\n([BGB]) and bis(ethylene-1,2-dioxy)borate anions ([BEDB]) coupled\nwith tetrabutylphosphonium ([P<sub>4444</sub>]) and tetrabutylammonium\n([N<sub>4444</sub>]) cations have been synthesized, and their physicochemical\nproperties are characterized. The ionic materials based on the most\npopular orthoborate anion, bis(oxalato)borate anion ([BOB]), which\ncontains four carbonyl groups, are all liquid at ambient temperature,\nwhile the bis(glycolato)borate ([BGB]) anion, with two carbonyl groups,\nand the bis(ethylene-1,2-dioxy)borate ([BEDB]) anion, without carbonyl\ngroups, render solids at ambient temperature. The ionic materials\nbased on the [BGB] anion display the highest decomposition temperatures,\nand those based on the BEDB anion are the lowest. The [P<sub>4444</sub>][BGB], [P<sub>4444</sub>][BEDB], and [N<sub>4444</sub>][BEDB] salts\nfeature significantly wider plastic phase I temperature ranges than\ntheir analogues. FTIR spectroscopy, multinuclear (<sup>15</sup>N, <sup>31</sup>P, <sup>13</sup>C, and <sup>11</sup>B) solid-state NMR spectroscopy,\nand single-crystal X-ray diffraction were all used to unveil the ionic\ninteractions and structural features, which display weaker ionic interactions\nfor [BEDB] compared to [BGB] when bearing the same cation and present\nrelatively higher crystallinity of [P<sub>4444</sub>][BGB] among the\nionic materials.