Crystal structure and Hirshfeld surface analysis of 1-methyl-4-(2-methyl-10H-benzo[b]thieno[2,3-e][1,4]diazepin-4-yl)piperazin-1-ium 2,5-dihydroxybenzoate propan-2-ol monosolvate

The asymmetric unit of the title salt consists of an olanzapinium cation, an independent 2,5 dihydroxybenzoate anion and a solvent isopropyl alcohol molecule. The central seven-membered heterocycle is in a boat conformation, while the piperazine ring displays a distorted chair conformation. The dihedral angle between the benzene and thiene rings flanking the diazepine ring is 52.58 (19)°. In the crystal, the anions and cations are connected by N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network.


Chemical context
Olanzapine is an atypical antipsychotic with indications for the treatment of schizophrenia, acute mania and the prevention of relapse in bipolar disorder. Olanzapine is structurally similar to clozapine, but is classified as a thienobenzodiazepine. Reviews on olanzapine in the management of bipolar disorders (Narasimhan et al., 2007) and olanzapine-associated toxicity and fatality in overdose (Chue & Singer, 2003) have been published. Olanzapine, the pharmaceutically active component of the title compound, a thienobenzodiazepine derivative, along with clozapine, quetiapine, risperidone and ziprasidone, belongs to the newer generation of atypical antipsychotic agents (Chakrabarti et al., 1980;Callaghan et al., 1999;Kennedy et al., 2001;Tandon & Jibson, 2003).
These atypical antipsychotic agents, in comparison with the older generation, show greater efficacy against both positive and negative symptoms of schizophrenia (a debilitating mental disorder) as well as associated cognitive deficits and are virtually devoid of extrapyramidal symptoms (Tandon, 2002). The therapeutic action of olanzapine against the symptoms of schizophrenia is thought to be due to its high affinity for dopaminergic D2 and serotonergic 5-HT2A receptor systems implicated in the pathogenesis of this disease (Bever & Perry, 1998).

Supramolecular features
In the crystal, the anions and cations are connected by C-HÁ Á ÁO, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds ( A superimposed fit of (I) (red) and the related structure (II) (blue).

Figure 3
A superimposed fit of (I) (red) and the related structure (III) (green).

Figure 4
Crystal packing of (I), showing the C-HÁ Á ÁO hydrogen bonds [R 2 with distances equal to the sum of van der Waals radii are indicated in white (Venkatesan et al., 2016). From Fig. 6, the bright-red spots appearing near the hydrogen atoms H2N, H4N, H10, and H13 in the cation indicate that these hydrogen atoms are involved in the intermolecular interactions. The shape-index (SI) diagram, a tool to visualizestacking interactions, for the cation, anion and solvent molecule is shown in Fig. 7. No adjacent red and blue triangles are seen, indicating that nointeractions are present, which is in agreement with the experimental findings. The overall twodimensional fingerprint (2D-FP) plots are illustrated in Fig. 6. The HÁ Á ÁH contacts make the highest contribution (53.8%) to the total crystal packing (broad peaks at d e + d i = $2.3 Å ). The second highest contribution is from HÁ Á ÁC/CÁ Á ÁH contacts (21.8%) and is indicated by the broad wing-like structure at d e + d i = $2.6 Å . The symmetrical sharp spikes at d e + d i = $1.6 Å are attributed to HÁ Á ÁO/OÁ Á ÁH contacts (14.3%).

Synthesis and crystallization
Olanzapine (156 mg, 0.5 mmol) and 2,5-dihydroxybenzoic acid (77 mg, 0.5 mmol) were dissolved in 20 mL of isopropyl alcohol and stirred magnetically for 5 h at 330 K. The mixture was kept aside for two days at room temperature and the salt formed was filtered off and dried. The compound was recrystallized from (1:1) isopropyl alcohol/DMF by slow evaporation at room temperature (m.p. 373-375 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Views of the Hirshfeld surfaces of title compound (I) mapped with d norm in two different orientations. The HS is plotted in the range À0.1500 to 1.4938 a.u.

Figure 7
Views of the shape-index diagram of title compound (I). Data collection: SMART (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2018); molecular graphics: QMOL (Gans & Shalloway, 2001), Mercury (Macrae et al., 2020); software used to prepare material for publication: ORTEPIII (Burnett & Johnson, 1996), WinGX publication routines (Farrugia, 2012) and PLATON (Spek, 2020). Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.