Toward crystal engineering of organic porous solids: Diammine salts of trimesic acid¹

We report the synthesis and X-ray crystallographic characterization of three new dibasic organic cation salts of 1,3,5-benzenetricarboxylic acid, trimesic acid. The focus of the study concerns crystal engineering of organic solids with predictable but fine-tuneable porosity. All three salts self-assemble into 2-D grids via interionic hydrogen bonding. Full details of single crystal X-ray diffraction studies of the salts are reported: (1) N,N,N′,N′-tetramethylethylenediammonium dihydrogentrimesate dihydrate, [HMe₂ NCH₂CH₂NMe₂H]2[l-CO₂-3,5(CO ₂H)₂C₆H₃]·2H₂O, a = 12.583(3), b = 15.1177(13), c = 15.407(3), β = 113.466(20), P2₁/c, d_calc(Mg/m³) = 1.42, Z = 4, 3515 unique reflns., R_f = 0.061, R_w, = 0.055; (2) N,N,N′,N′-tetraethylethylenediammonium dihydrogentrimesate, [HEt₂NCH₂CH₂NEt₂H]2[l-CO ₂-3,5(CO₂H)₂C₆H₃], a = 6.6196(18), b = 9.243(2), c = 12.360(4), α = 75.16(4), β = 75.88(5), γ = 84.297(22), PT, d_calc(Mg/m³) = 1.39, Z = 1, 1844 unique reflns., R_f = 0.056, R_w, = 0.050; (3) N,N,N′,N′-tetramethylethylenediammonium hydrogentrimesate, [HMe₂NCH₂CH₂NMe₂H][1,3-(CO ₂)₂-5-(CO₂H)C₆H₃], a = 8.636(4), b = 21.6877(17), c = 9.436(5), β = 114.49(6), P2₁/c, d_calc(Mg/m³) = 1.35, Z = 4, 2820 unique reflns., R_f = 0.050, R_w, = 0.054.