Crystal structure, infrared and Raman spectra of tripotassium trisaccha-rinate dihydrate, K₃(C₇H 4NO₃S)₃·2H₂O

The crystal structure of tripotassium trisaccharinate dihydrate, K₃(C₇H₄NO₃S)₃ ·2H₂O, is triclinic, space group P 1̄, Z = 2. It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K-O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K-N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O) = 2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O) = 2.851(3) Å) and the disordered water molecules (O23W) (R(O...O) = 3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C-H...O hydrogen bonds (R(C-H...O) = 3.027(4) - 3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate.