Benzyltributylammonium 4-hydroxynaphthalene-2-sulfonate

The title compound, C19H34N+·C10H7O4S−, is a charge-control agent used for toners in electrophotography. In the crystal structure, centrosymmetric anions associate through O—H⋯O hydrogen bonds formed between the O—H group of one anion and the sulfonate O atom of a neighbor. The components of the dimer are offset with respect to each other so that the separation between the two parallel naphthalene skeletons is about 1.6 Å. The ethyl residues of two of the butyl groups are disordered and were modelled over two postions (site occupancies = 0.33/0.67 and 0.34/0.66).

The title compound, C 19 H 34 N + ÁC 10 H 7 O 4 S À , is a charge-control agent used for toners in electrophotography. In the crystal structure, centrosymmetric anions associate through O-HÁ Á ÁO hydrogen bonds formed between the O-H group of one anion and the sulfonate O atom of a neighbor. The components of the dimer are offset with respect to each other so that the separation between the two parallel naphthalene skeletons is about 1.6 Å . The ethyl residues of two of the butyl groups are disordered and were modelled over two postions (site occupancies = 0.33/0.67 and 0.34/0.66).

Related literature
For the function of charge-control agents, see: Nash et al. (2001). For the structures of benzyltributylammonium 4hydroxynaphthalene-1-sulfonate and benzyltributylammonium 6-hydroxynaphthalene-2-sulfonate, see: Mizuguchi et al. (2007) and Uta et al. (2009) Table 1 Hydrogen-bond geometry (Å , ). of (I) in connection with the mechanism of their high thermal stability, namely benzyltributylammonium 4-hydroxynaphthalene-1-sulfonate (Mizuguchi et al., 2007) and benzyltributylammonium 6-hydroxynaphthalene-2-sulfonate (Uta et al., 2009). The anions in both isomers are found to form chains via O-H···O hydrogen bonds formed between the O-H group of one anion and the sulfonic-O atom of neighbors. The presence of these hydrogen-bonded networks ensures the high thermal stability of these compounds as characterized by their high melting points of 462 K and 433 K, respectively. This paper describes a variation to the above in that the O-H···O hydrogen bonding occurs between isolated pairs of molecules.
The asymmetric unit of (I) comprises a benzyltributylammonium cation and a 4-hydroxynaphthalene-2-sulfonate anion, Fig. 1. Centrosymmetrically related anions associate via O-H···O hydrogen bonds, Fig. 2 and Table 1, to form a 14membered ring. As highlighted in the side-on view of Fig. 3, a step topology characterizes the dimeric unit so that the distance between the parallel naphthalene skeletons is about 1.6 Å. The hydrogen-bonded dimer in (I) is found to enhance the thermal stability as seen in the melting point of 451 K.

Experimental
Compound (I) was obtained from Orient Chemical Industries, Ltd. and was recrystallized from a dichloromethane solution.
After 48 h, a number of colorless crystals were obtained in the form of blocks.