Supramolecular Arrangement in Styphnic Acid and Naphthalene-1 , 4-diol ( 1 : 1 ) through a Novel Synthetic Rote for Styphnic Acid

1 Chemistry Department, Faculty of Science, Taif University, Al-Haweiah, P.O. Box 888, Taif 21974, Saudi Arabia 2Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt 3 Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt 4Osman Gazi University, Art and Science Faculty, Department of Chemistry, Eskişehir, Turkey 5 Giresun University, Art and Science Faculty, Department of Chemistry, Giresun, Turkey


Introduction
Many of the electron donor-acceptor (EDA) interactions had been widely studied spectrophotometrically in the determination of drugs that are easy to be determined based on CT-complex formation with some electron acceptors [1][2][3].
The study of the charge-transfer complexes formed in the reaction of aromatic electron acceptors (-acceptors) with various electron donors has attracted considerable interest, and growing importance owing to their significant, physical and chemical properties [4,5].A vast number of the chargetransfer complexes formed during the reaction of and -acceptors with organic compounds containing different sites of donation (nitrogen, oxygen or sulfur atoms) were extensively investigated [6][7][8][9][10].This paper is a continuation of our previous investigation [11][12][13][14] concerned with the formation of stable charge-transfer complexes formed during the reaction of electron donors.
The picric acid (2,4,6-trinitrobenzene-1-ol) (2,4,6-trinitrophenol) and picrates can be used in explosive materials.2,4,6-trinitrobenzene-1,3-diol is an analog of the picric acid and it is also known as styphnic acid, or trinitroresorcinol.With regard to explosive power and sensitiveness styphnic acid is similar to picric acid.Since, its price is considerably higher than that of picric acid, it is not used in explosive technology and only lead styphnate (lead trinitroresorcinate) is of great practical importance as an initiator.On the whole, the properties of styphnate salts are similar to those of picrates.

Results and Discussion
It is well known that nitro group in picric acid is a strong oxidizing agent, and concerning picric acid that contains three of these nitro groups, we believed that, it is the source of the oxidation of the -naphthol along with itself to give naphtalene-1,4-diol and styphnic acid, respectively.Similar features of this kind of mechanisms were suggested earlier [15].The reaction under investigation is a reaction between an electron-rich -naphthol and electron-poor picric acid in a methanol chloroform mixture as a solvent.
The 1 H NMR of the separated complex (Figure 1) revealed one singlet signal for the symmetrical H 2 and H 3 protons in 1,4-dihydroxynaphthalene at  = 6.91 ppm along with one singlet signal for one proton in styphnic acid at  = 6.91 ppm.
The possibility of hydrogen bonds was explored for the synthesized compound by the statistical criterion proposed by Taylor and Kennard [15] and was found to be very effective in supramolecular arrangement of molecular units in the solid state.In the solid state, the naphtalene-1,4-diol part of the asymmetric unit acts as hydrogen bond donor via its O5, C5, C8, and C9 atoms to O2, O3, and O4 atoms of symmetry related styphnic acid parts which are explained below, to give three-dimensional network in supramolecular arrangement.
These two polymeric chains fit into one another by molecules in asymmetric unit so the polymeric chains are arranged approximately perpendicular to each other (Figure 7).6, Table 1).and C5-H5⋅ ⋅ ⋅ O3 v intermolecular hydrogen bonds to form polymeric chains lying parallel to the [010] plane (Figure 8, Table 2).The C5 and C9 atoms of naphtalene-1,4-diol in the asymmetric unit act as bifurcated hydrogen bond donors via their H5 and H9 either to form polymeric chains along the  and  axes or to extend the these chains through the  axis so the polymeric chains bond to each other by O2 ii ⋅ ⋅ ⋅ H5⋅ ⋅ ⋅ O3 v and O3 iv ⋅ ⋅ ⋅ H9⋅ ⋅ ⋅ O4 iii bifurcated hydrogen bonds, respectively (Figure 9, Table 2).
Also, there were found some  ⋅ ⋅ ⋅  interactions between the rings of naphtalene-1,4-diol and the rings of styphnic acid through the  axis (Figure 10) to contribute to supramolecular arrangement in the solid state (Figure 11).

Figure 4 :
Figure 4: The asymmetric unit of the compound with the atomic labeling scheme.Displacement ellipsoids of non-H atoms are drawn at the 30% probability level.

Figure 6 :
Figure 6: The view of infinite polymeric chains along the  axis.

Figure 7 :
Figure 7: The arrangement of polymeric chains along  and  axis.

Figure 8 :
Figure 8: Forming of polymeric chains lying parallel to the [010] plane.

Figure 9 :
Figure 9: The view of bifurcated hydrogen bonds.

Figure 10 :Figure 11 :
Figure 10: The  ⋅ ⋅ ⋅  interactions in the molecules along the  axis.

Table 1 :
Crystal data and structure refinement for the compound.