Two acetic acid functionalized isonicotinamide (or 4‐carbamoyl‐1‐(carboxymethyl) pyridin‐1‐ium) salts with Br⁻ and BPh₄⁻ anions have been prepared. The hydrophilic Br⁻ and hydrophobic BPh₄⁻ anions result in two salts having different solubilities in water and acetone. Further recrystallizations of Br⁻ and BPh₄⁻ salts from protic H₂O/THF and aprotic acetone/ether solvents gave single crystals of a non‐decarboxylated zwitterion (a isonicotiamide betaine) and a decarboxylated isonicotiamides salt at room temperature respectively. A carboxylate−carboxylate dimer motif was observed in the zwitterion crystal structure. Theoretical calculations by using the PBE1PBE method at the cc‐pVDZ level indicate the carboxylate−carboxylate dimer motif was stabilized by the C−H⋅⋅⋅O hydrogen bonding assisted carbonyl⋅⋅⋅carbonyl interaction.

中文翻译：

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C-H⋅⋅⋅O氢键辅助的羧酸盐⋅⋅⋅羧酸相互作用防止N-乙酸盐异烟酰胺甜菜碱脱羧

两个乙酸官能化异烟酰胺（或4-氨基甲酰基-1-（羧甲基）吡啶-1-鎓）盐与溴^-和BPH ₄ ^-的阴离子已经制备。亲水溴^-和疏水BPH ₄ ^-阴离子导致具有在水和丙酮不同溶解度两种盐。的Br进一步重结晶^-和BPH ₄ ^-的盐从质子ħ ₂O / THF和非质子丙酮/醚溶剂在室温下分别得到非脱羧两性离子（异烟酰胺甜菜碱）和脱羧异烟酰胺盐的单晶。在两性离子晶体结构中观察到羧酸盐-羧酸盐二聚体基序。使用cc-pVDZ水平的PBE1PBE方法进行的理论计算表明，羧酸盐-羧酸盐二聚体基序通过C-H···O氢键辅助的羰基···羰基相互作用而稳定。