research communications Acta Cryst. (2020). E76, 889–895 https://doi.org/10.1107/S205698902000657X 889 Received 7 April 2020 Accepted 15 May 2020 Edited by J. Ellena, Universidade de Sa ˆo Paulo, Brazil Keywords: crystal structure; hydrogen bond; benzothiazine; antibacterial activity; Hirshfeld surface. CCDC reference: 2004559 Supporting information: this article has supporting information at journals.iucr.org/e Crystal structure, Hirshfeld surface analysis and interaction energy, DFT and antibacterial activity studies of (Z)-4-hexyl-2-(4-methylbenzylidene)-2H- benzo[b][1,4]thiazin-3(4H)-one Ghizlane Sebbar, a * Brahim Hni, b Tuncer Ho ¨kelek, c Joel T. Mague, d Nada Kheira Sebbar, b,e Bouchra Belkadi a and El Mokhtar Essassi b a Laboratory of Microbiology and Molecular Biology, Faculty of Sciences, University Mohammed V, Rabat, Morocco, b Laboratoire de Chimie Organique Heterocyclique URAC 21, Po ˆ le de Competence Pharmacochimie, Faculte ´ des Sciences, Universite ´ Mohammed V, Rabat, Morocco, c Department of Physics, Hacettepe University, 06800 Beytepe, Ankara, Turkey, d Department of Chemistry, Tulane University, New Orleans, LA 70118, USA, and e Laboratoire de Chimie Applique ´e et Environnement, Equipe de Chimie Bioorganique Applique ´e, Faculte ´ des Sciences, Universite ´ Ibn Zohr, Agadir, Morocco. *Correspondence e-mail: [email protected]The title compound, C 22 H 25 NOS, consists of methylbenzylidene and benzothia- zine units linked to a hexyl moiety, where the thiazine ring adopts a screw-boat conformation. In the crystal, inversion dimers are formed by weak C— H Mthn O Bnzthz hydrogen bonds and are linked into chains extending along the a-axis direction by weak C—H Bnz O Bnzthz (Bnz = benzene, Bnzthz = benzothiazine and Mthn = methine) hydrogen bonds. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from HH (59.2%) and HC/CH (27.9%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. Computational chemistry indicates that in the crystal, the C—H Bnz O Bnzthz and C—H Mthn O Bnzthz hydrogen- bond energies are 75.3 and 56.5 kJ mol 1 , respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state. The HOMO—LUMO behaviour was elucidated to determine the energy gap. Moreover, the antibacterial activity of the title compound was evaluated against gram-positive and gram-negative bacteria. 1. Chemical context 1,4-Benzothiazine derivatives constitute an important class of heterocyclic compounds which, even when part of a complex molecule, possess a wide spectrum of biological activities (Sebbar et al., 2016a; Gupta et al., 2009). Various 1,4-benzo- thiazine derivatives have been synthesized by several methods (Parai & Panda, 2009; Barange et al. , 2007; Saadouni et al., 2014). 1,4-Benzothiazine derivatives are important because of their interesting biological properties such as anti-bacterial (Olayinka, 2012; Bhikan et al., 2012), anti-fungal (Schiaffella et al., 2006; Gupta & Wagh, 2006), antiproliferative (Zieba et al., 2010), antimalarial (Barazarte et al. , 2009) and anti-inflam- matory (Kaneko et al. , 2002) activities. The biological activities of some 1,4-benzothiazines are similar to those of pheno- thiazines, featuring the same structural specificity (Hni et al., 2019a,b; Ellouz et al., 2017a,b; Sebbar et al., 2019a,b). In a continuation of our research devoted to the develop- ment of substituted 1,4-benzothiazine derivatives (Ellouz et al., 2015, 2019; Sebbar et al., 2015, 2017a; Ellouz et al.), we have ISSN 2056-9890
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Crystal structure, Hirshfeld surface analysis andinteraction energy, DFT and antibacterial activitystudies of (Z)-4-hexyl-2-(4-methylbenzylidene)-2H-benzo[b][1,4]thiazin-3(4H)-one
Ghizlane Sebbar,a* Brahim Hni,b Tuncer Hokelek,c Joel T. Mague,d Nada Kheira
Sebbar,b,e Bouchra Belkadia and El Mokhtar Essassib
aLaboratory of Microbiology and Molecular Biology, Faculty of Sciences, University Mohammed V, Rabat, Morocco,bLaboratoire de Chimie Organique Heterocyclique URAC 21, Pole de Competence Pharmacochimie, Faculte des
Sciences, Universite Mohammed V, Rabat, Morocco, cDepartment of Physics, Hacettepe University, 06800 Beytepe,
Ankara, Turkey, dDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA, and eLaboratoire de
Chimie Appliquee et Environnement, Equipe de Chimie Bioorganique Appliquee, Faculte des Sciences, Universite Ibn
Symmetry codes: (i) x þ 1; y; z; (ii) �x;�yþ 1;�zþ 1.
Figure 3A partial packing diagram down the a-axis direction giving an end view ofthree adjacent chains.
Figure 2Detail of the chain of dimers viewed down the b-axis direction with theweak C—HMthn� � �OBnzthz and C—HBnz� � �OBnzthz (Bnz = benzene, Bnzthz= benzothiazine and Mthn = methine) hydrogen bonds depicted bydashed lines.
4. Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the
crystal of the title compound, a Hirshfeld surface (HS)
analysis (Hirshfeld, 1977; Spackman & Jayatilaka, 2009) was
carried out by using Crystal Explorer 17.5 (Turner et al., 2017).
In the HS plotted over dnorm (Fig. 4), the white surface indi-
cates contacts with distances equal to the sum of van der Waals
radii, and the red and blue colours indicate distances shorter
(in close contact) or longer (distinct contact) than the van der
Waals radii, respectively (Venkatesan et al., 2016). The bright-
red spots appearing near O1 and hydrogen atoms H4 and H15
indicate their roles as the respective donors and/or acceptors;
they also appear as blue and red regions corresponding to
positive and negative potentials on the HS mapped over
electrostatic potential (Spackman et al., 2008; Jayatilaka et al.,
2005) as shown in Fig. 5. The blue regions indicate the positive
electrostatic potential (hydrogen-bond donors), while the red
regions indicate the negative electrostatic potential
(hydrogen-bond acceptors). The shape-index of the HS is a
tool to visualize the �–� stacking by the presence of adjacent
red and blue triangles; if there are no adjacent red and/or blue
triangles, then there are no �–� interactions. Fig. 6 clearly
suggests that there are no �–� interactions in (I).
The overall two-dimensional fingerprint plot, Fig. 7a, and
those delineated into H� � �H, H� � �C/C� � �H, H� � �S/S� � �H,
H� � �O/O� � �H and H� � �N/N� � �H contacts (McKinnon et al.,
2007) are illustrated in Fig. 7 b--f, respectively, together with
their relative contributions to the Hirshfeld surface. The most
important interaction is H� � �H, contributing 59.2% to the
overall crystal packing, which is reflected in Fig. 7b as widely
scattered points of high density due to the large hydrogen
content of the molecule with the tip at de = di = 1.14 A. In the
absence of C—H� � �� interactions, the pair of characteristic
wings in the fingerprint plot delineated into H� � �C/C� � �H
contacts (Fig. 7c, 27.9% contribution to the HS) has the tips at
de + di = 2.77 A. The pair of spikes in the fingerprint plot
delineated into H� � �S/S� � �H (Fig. 7d, 5.6% contribution) has
the tips at de + di = 2.98 A. The H� � �O/O� � �H contacts (Fig. 7e,
5.5% contribution) have a symmetrical distribution of points
with the tips at de + di = 2.27 A. Finally, the H� � �N/N� � �H
Figure 4View of the three-dimensional Hirshfeld surface of the title compoundplotted over dnorm in the range �0.2415 to 1.4195 a.u.
Figure 5View of the three-dimensional Hirshfeld surface of the title compoundplotted over electrostatic potential energy in the range �0.0500 to 0.0500a.u. using the STO-3 G basis set at the Hartree–Fock level of theoryhydrogen-bond donors and acceptors are shown as blue and red regionsaround the atoms corresponding to positive and negative potentials,respectively.
Figure 6Hirshfeld surface of the title compound plotted over shape-index.
Figure 7The full two-dimensional fingerprint plots for the title compound,showing (a) all interactions, and delineated into (b) H� � �H, (c) H� � �C/C� � �H, (d) H� � �S/S� � �H, (e) H� � �O/O� � �H and (f) H� � �N/N� � �H inter-actions. The di and de values are the closest internal and externaldistances (in A) from given points on the Hirshfeld surface contacts.
contacts (Fig. 7f), make only a 0.8% contribution to the HS
with the tips at de + di = 3.28 A.
The Hirshfeld surface representations with the function
dnorm plotted onto the surface are shown for the H� � �H,
H� � �C/C� � �H, H� � �S/S� � �H and H� � �O/O� � �H interactions in
Fig. 8a--d, respectively.
The Hirshfeld surface analysis confirms the importance of
H-atom contacts in establishing the packing. The large number
of H� � �H and H� � �C/C� � �H interactions suggest that van der
Waals interactions and hydrogen bonding play the major roles
in the crystal packing (Hathwar et al., 2015).
5. Interaction energy calculations
The intermolecular interaction energies are calculated using
CE–B3LYP/6–31G(d,p) energy model available in Crystal
Explorer 17.5 (Turner et al., 2017), where a cluster of mol-
ecules is generated by applying crystallographic symmetry
operations with respect to a selected central molecule within
the radius of 3.8 A by default (Turner et al., 2014). The total
intermolecular energy (Etot) is the sum of electrostatic (Eele),
polarization (Epol), dispersion (Edis) and exchange-repulsion
(Erep) energies (Turner et al., 2015) with scale factors of 1.057,
0.740, 0.871 and 0.618, respectively (Mackenzie et al., 2017).
Hydrogen-bonding interaction energies (in kJ mol�1) are
�15.5 (Eele), �2.9 (Epol), �109.6 (Edis), 62.8 (Erep) and �75.3
(Etot) for C4—H4� � �O1 and �24.8 (Eele), �9.3 (Epol), �60.1
(Edis), 46.9 (Erep) and �56.5 (Etot) for C15—H15� � �O1.
6. DFT calculations
The optimized structure of the title compound in the gas phase
was generated theoretically via density functional theory
(DFT) using standard B3LYP functional and 6–311 G(d,p)
basis-set calculations (Becke, 1993) as implemented in
GAUSSIAN 09 (Frisch et al., 2009). The theoretical and
experimental results are in good agreement (Table 2). The
highest-occupied molecular orbital (HOMO), acting as an
electron donor, and the lowest-unoccupied molecular orbital
(LUMO), acting as an electron acceptor, are very important
parameters for quantum chemistry. When the energy gap is
small, the molecule is highly polarizable and has high chemical
reactivity. The DFT calculations provide some important
information on the reactivity and site selectivity of the mol-
ecular framework. EHOMO and ELUMO clarify the inevitable
charge-exchange collaboration inside the studied material,
Figure 9The energy band gap of the title compound.
Figure 10Antibacterial activity of the title compound (I) and commercial antibioticChloramphenicol (Chlor) against bacteria Escherichia coli, Pseudomonasaeruginosa, Staphylococcus aureus and Streptococcus fasciens.
5 mg ml�1 for Streptococcus fasciens, which corresponds to the
best MIC activity as compared to the commercial antibiotic. In
addition, the maximum effect of I was recorded against
Pseudomonas aeruginosa (diameter of inhibition 12.1 mm).
Chlor presents an antibacterial activity diameter of inhibition
of between 19 mm and 27 mm and no zone inhibition was
observed with dimethylsulfoxide (DMSO) [(1%): 1 mL of
DMSO added to 99 mL ofulltra-pure water] [The test samples
were first dissolved in DMSO (1%), which did not affect the
microbial growth.] On one hand, the chemical structure of I
can explain this biological effect. The mechanism of action of I
is not attributable to one specific mechanism, but there are
several targets in the cell: degradation of the cell wall, damage
to membrane proteins, damage to cytoplasmic membrane,
leakage of cell contents and coagulation of cytoplasm. On the
other hand, it should be noted that the functionalized deri-
vatives by ester groups and benzene rings have the highest
antibacterial coefficient (92% of pathogenic bacteria are
sensitive). This study is expected to take anti-inflammatory,
antifungal, anti-parasitic and anti-cancer activities, because
the literature gives a lot of interesting results on these topics.
Some other types of bacteria may possibly be tested by
employing the same method so as eventually to generalize the
The experimental details including the crystal data, data
collection and refinement are summarized in Table 5. The C-
bound H atoms were positioned geometrically, with C—H =
0.95 A (for aromatic and methine H atoms), 0.99 A (for
methylene H atoms) and 0.98 A (for methyl H atoms), and
constrained to ride on their parent atoms, with Uiso(H) = k �
Ueq(C), where k = 1.5 (for methyl H atoms) and k = 1.2 for
other H atoms.
Funding information
JTM thanks Tulane University for support of the Tulane
Crystallography Laboratory. TH is grateful to Hacettepe
University Scientific Research Project Unit (grant No. 013
D04 602 004).
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S = 1.084860 reflections228 parameters0 restraints
supporting information
sup-2Acta Cryst. (2020). E76, 889-895
Primary atom site location: dualSecondary atom site location: difference Fourier
mapHydrogen site location: inferred from
neighbouring sitesH-atom parameters constrained
w = 1/[σ2(Fo2) + (0.0868P)2]
where P = (Fo2 + 2Fc
2)/3(Δ/σ)max = 0.002Δρmax = 0.54 e Å−3
Δρmin = −0.22 e Å−3
Special details
Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, collected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = –30.00 and 210.00°. The scan time was 20 sec/frame.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.Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. H-atoms attached to carbon were placed in calculated positions (C—H = 0.95 - 0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)