Two acetic acid functionalized isonicotinamide (or 4-carbamoyl-1-(carboxymethyl) pyridin-1-ium) salts with Br À and BPh 4 À anions have been prepared. The hydrophilic Br À and hydrophobic BPh 4 À anions result in two salts having different solubilities in water and acetone. Further recrystallizations of Br À and BPh 4 À salts from protic H 2 O/THF and aprotic acetone/ether solvents gave single crystals of a nondecarboxylated zwitterion (a isonicotiamide betaine) and a decarboxylated isonicotiamides salt at room temperature respectively. A carboxylateÀ carboxylate dimer motif was observed in the zwitterion crystal structure. Theoretical calculations by using the PBE1PBE method at the cc-pVDZ level indicate the carboxylateÀ carboxylate dimer motif was stabilized by the CÀ H···O hydrogen bonding assisted carbon-yl···carbonyl interaction.[a] J.