research papers Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Topological analysis of electron density and the electrostatic properties of isoniazid: an experimental and theoretical study

ISSN 2052-5206

Gnanasekaran Rajalakshmi,a Venkatesha R. Hathwarb‡ and Poomani Kumaradhasa* a

Laboratory of Biocrystallography and Computational Molecular Biology, Department of Physics, Periyar University, Salem 636 011, India, and bSolid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India

‡ Present address: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK8000 Aarhus C, Denmark

Correspondence e-mail: [email protected]

Isoniazid (isonicotinohydrazide) is an important first-line antitubercular drug that targets the InhA enzyme which synthesizes the critical component of the mycobacterial cell wall. An experimental charge-density analysis of isoniazid has been performed to understand its structural and electronic properties in the solid state. A high-resolution single-crystal X-ray intensity data has been collected at 90 K. An aspherical multipole refinement was carried out to explore the topological and electrostatic properties of the isoniazid molecule. The experimental results were compared with the theoretical charge-density calculations performed using CRYSTAL09 with the B3LYP/6-31G** method. A topological analysis of the electron density reveals that the Laplacian of electron density of the N—N bond is significantly less negative, which indicates that the charges at the b.c.p. (bond-critical point) of the bond are least accumulated, and so the bond is considered to be weak. As expected, a strong negative electrostatic potential region is present in the vicinity of the O1, N1 and N3 atoms, which are the reactive locations of the molecule. The C—H  N, C—H  O and N—H  N types of intermolecular hydrogen-bonding interactions stabilize the crystal structure. The topological analysis of the electron density on hydrogen bonding shows the strength of intermolecular interactions.

Received 25 July 2013 Accepted 8 December 2013

1. Introduction

# 2014 International Union of Crystallography

Acta Cryst. (2014). B70, 331–341

Mycobacterium Tuberculosis (MTB) is the deadliest infectious disease (Dye et al., 1998) which affects one-third of the world’s population (Vijay et al., 2007). Approximately nine million active tuberculosis (TB) cases develop every year and approximately two to three million die annually (World Health Organization, 2002; Bloom, 1994). MTB remains a leading cause of death when it is co-infected with AIDS (Friedland, 2007). After the discovery of some antimycobacterial agents (isoniazid, pyrazinamide, ethambutol, rifampin and streptomycin) there was a steep decrease in TB cases (Gautam et al., 2007). Since 1980 multidrug resistant (MDR; Lenaerts et al., 2008) and extensive drug resistant tuberculosis (XDR) have been rapidly emerging. Furthermore, the medical treatment available for drug resistant tuberculosis was found to be very costly, less effective, time consuming (Basso & Blanchard, 1998; Bastian & Colebunders, 1999) and having more severe side effects than the nonresistant strains. For these reasons, tuberculosis forms a major public health problem in developing countries. Several research groups across the world are working to find a solution for this problem. Studies to find new drugs with fewer side effects to combat tuberculosis are in the pipeline. Recently some new drugs, namely TMC207, OPC-67683, PA-824, LL3858 and SQ109, were developed, which are currently doi:10.1107/S2052520613033209

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research papers under clinical trial (Patralekha, 2008). For the past 30 years (Gautam et al., 2007), there have been no new drugs introduced to completely cure the disease. Therefore, there is an urgent need to develop new drugs with enhanced pharmacological properties to cure the disease. In this context, the ligand-based drug design requires precise structural knowledge of the drug molecule. However, it is known that the drugbinding mechanism is solely attributed to the presence of complementary charged groups between the drug and the receptor, charge distribution, electrostatic potential and the strength of intermolecular interactions. A deeper understanding of the structural, bond topological and the electrostatic properties of the molecule allows the bond strength to be characterized and the reactive locations of the molecule to be predicted, when present at the active site of the receptor. Isoniazid has been used as an antitubercular drug since 1950. It is bacteriocidal (Middlebrook, 1952), i.e. it kills the mycobacteria by inhibiting the mycolic acid synthesis, an essential component of the mycobacterial cell wall (Takayama et al., 1972; Winder et al., 1982; Quemard et al., 1991). It is a nicotinamide analog (Zhang & Mitchison, 2003) and a prodrug, activated by the catalase-peroxidase enzyme katG (Johnsson & Schultz, 1994; Sacchettini & Blanchard, 1996). InhA enzyme is the primary molecular target of isoniazid (Rozwarski et al., 1998). The activated drug of isoniazid, isonicotinic acyl anion or isonicotinic acyl radical is covalently attached to the nicotinamide ring of NADH present in the active site of the InhA enzyme (Rozwarski et al., 1998), as shown in Fig. 1. The crystal structure of isoniazid (Jensen, 1952) was determined by L. H. Jensen in 1952. In the present study we have redetermined the crystal structure of isoniazid at 90 K and also carried out a charge-density analysis to understand its bond strength and electrostatic properties. In the experimental electron density distribution, the electron densities were calculated using the Hansen–Coppens formalism (Hansen & Coppens, 1978), where the atomic densities are represented as three components, such as the core, spherical expansion and contraction terms () in the valence shell, and the valence deformation density in terms of normalized spherical harmonics (dlm), the radial expansion and contraction parameter of the valence shell (0 ), given as atom ðrÞ ¼ c ðrÞ þ Pv 3 v ðrÞ þ

lmax X

03 Rl ð0 rÞ

l X

Plm dlm ð; ’Þ

m¼0

l¼0

ð1Þ

Topological properties such as electron density, the second derivative of electron density and electrostatic properties of

isoniazid are also calculated. The second derivative of electron density, i.e. the Laplacian of electron density, provides information about the nature of the chemical bond (Bader, 1990). The Laplacian of electron density at the bond critical point (b.c.p.) is used to identify whether the electron density is locally concentrated or depleted at that point. The critical point is a point in space where the gradient of the electron density is zero [rbcp(r) = 0]. If r2bcp(r) < 0, the electron density is locally concentrated representing shared interactions and when r2bcp(r) > 0, the electron density is locally depleted resulting in closed-shell interactions (Bader, 1990). The topological and the electrostatic properties of the isoniazid molecule were compared with the theoretical calculations performed using CRYSTAL09 software (Dovesi et al., 2005, 2009).

2. Experimental 2.1. X-ray intensity data collection and structure refinement details

The isoniazid sample was obtained from a commercial source and was crystallized from ethanol solvent by slow evaporation at low temperature. The grown crystals were colourless and block shaped, and from them a high quality single crystal was selected for X-ray diffraction intensity measurements. A good quality single crystal was mounted in a Hampton Research Cryoloop using paratone-N oil for data collection. The crystal was cooled by cold nitrogen gas stream to 90 K by using an Oxford Cryostream N2 open-flow crysostat. The crystal was allowed to stabilize at 90 K for 1 h. Initially the unit-cell parameters were determined from the three sets of 25 frames of reflections. A total of 86 231 reflections were collected up to the maximum diffraction angle 2 = 102.9 using a Bruker Kappa APEX II CCD area-detector system (Bruker, 2000) with Mo K radiation. Thus, the measured data set exhibits 99.1% completeness for the resolution (sin /)max ˚ 1 with a redundancy of 12. The data reduction and cell = 1.1 A refinement were performed using SAINT-Plus (Bruker, 2006); SORTAV (Blessing, 1997) was used for sorting, scaling and merging the data sets. Of the 86 231 reflections, 2789 were rejected as outliers and 83 442 reflections were accepted. After merging, 6960 unique reflections (I  2) were recovered to a ˚ 1. The internal agreement resolution of (sin /)max = 1.1 A factor for the final data set is Rint = 0.0284 and Rsigma = 0.0288. The structure was solved by direct methods using SHELXS97 (Sheldrick, 2008) and refined by SHELXL97 (Sheldrick, 2008) software. All H atoms of the molecule were located from the Fourier difference map and refined isotropically. 2.2. Mulitpole refinements

Figure 1 Schematic representation of the prodrug isoniazid into its two active forms by the KatG enzyme.

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The multipole refinement of the molecule was performed using the XDLSM routine incorporated in XD2006 (Volkov et al., 2006). Initially, the scale factor was refined for full data of ˚ 1. Subsequently, a high-order resolution (sin /)max = 1.1 A ˚ 1 was carried out to obtain refinement (sin /)max = 0.8 A

Isoniazid: experimental and theoretical study

Acta Cryst. (2014). B70, 331–341

research papers accurate positional and anisotropic displacement parameters. During this refinement the hydrogen-bond distances were adjusted to the neutron bond distances (Allen et al., 1987; C1—H1 = 1.083, C3—H3 = 1.083, C4—H4 = 1.083, C5—H5 = 1.083, N2—H2 = 1.099, N3—H3A = 1.099 and N3—H3B = ˚ ). Furthermore, multipole refinement was performed, 1.099 A in which C, N and O atoms were treated up to the hexadecapole level (l = 4), but the H atoms were refined up to the dipole level (l = 2). The kappa value for H atoms was fixed at 1.2. To reduce the number of refinement variables, a chemical constraint was imposed on the chemically equivalent atoms; subsequently this was removed in the latter part of the refinement. First Pv, , Plm and scale factors were refined in a step-wise manner for the non-H atoms until convergence was reached. Then, Pv + , Plm and scale factors were refined. In the further refinement, 0 for non-H atoms were fixed as reported by Volkov et al. (2001). At each step, the refinements were performed continuously until convergence was achieved. Finally, the multipole (Pv +  + Plm + 0 ) parameters and the positional and thermal (xyz + uij + scale) parameters were refined separately until convergence was reached. Electroneutrality was maintained throughout the refinement. The featureless residual density map (Fig. S1 of the supporting information1) reflects the correctness of the model refinement. Usually, the problem of phase retrieval in non-centrosymmetric space groups leads to large correlation effects between multipoles and structural parameters (Koritsanszky & Coppens, 2001); in the present study we did not find any such correlation in the multipole refinement (Parrish et al., 2006; Draskovic et al., 2010). In the multipole refinement, the maximum difference in mean-square displacement amplitude (DMSDA) along the interatomic bonds is found to be less ˚ 2. This indicates that the refinement was than 4  104 A complete, atomic thermal motions were well resolved suggesting clean deconvolution of the aspherical atomic electron density from the atomic displacement parameters. The topological properties of the electron density were calculated using the XDPROP routine of XD2006 (Volkov et al., 2006). The structure and multipole refinement details are presented in Table 1.

Table 1 Experimental details. Crystal data Chemical formula Mr Crystal system, space group Temperature (K) ˚) a, b, c (A ˚ 3) V (A Z Radiation type  (mm1) Crystal size (mm) Data collection Diffractometer Absorption correction Tmin, Tmax No. of measured, independent and observed [I > 2.0(I)] reflections Rint ˚ 1) (sin /)max (A Refinement R[F 2> 2(F 2)], wR(F 2), S No. of reflections No. of parameters H-atom treatment ˚ 3)
max,
min (e A

C6H7N3O 137.1 Orthorhombic, P212121 90 (2) 3.7601 (1), 11.2911 (3), 14.6877 (4) 623.58 4 Mo K 0.11 0.25  0.24  0.14

Bruker Kappa APEXII CCD detector Analytical 0.978, 0.984 83 442, 6960, 6442 0.028 1.100

0.015, 0.017, 1.02 6253 344 H atoms treated by a mixture of independent and constrained refinement 0.10, 0.10

Computer programs: KAPPA APEX, BRUKER-AXS, SAINT-Plus (Bruker, 2006), SHELXS97, SHELXL97 (Sheldrick, 2008), XD2006 (Volkov et al., 2006), ORTEP (Farrugia, 2012) PLATON (Spek, 2003).

truncation parameters were set as ITOL1 = ITOL2 = ITOL3 = ITOL4 = 6 and ITOL5 = 14. For better convergence the level shifter value was set to 0.6 Hartree per cycle. The atomic position and displacement parameters were fixed to the values obtained from the experiment. The multipolar refinement of the theoretical structure factors was carried out with the same multipoles as used in the experiment. The topological properties of electron density and electrostatic properties were compared with the experimental results.

3. Results and discussions 2.3. Computational details

3.1. Structural aspects

To compare the bond-topological properties calculated from the experimental charge-density analysis with theory, a periodic calculation was performed for the isoniazid molecule using the CRYSTAL09 software package (Dovesi et al., 2005, 2009) with the geometry obtained from the experimental multipole refinement as input. This quantum chemical calculation was carried out using the density-functional theory (DFT) method from the B3LYP (Becke, 1993; Lee et al., 1998) level of theory with the basis sets 6-31G** (Hariharan & Pople, 1973) and it provides consistent results. The shrinking factors (IS1–IS3) along the reciprocal lattice vectors were set at 4 (30 K points in the irreducible Brillouin Zone). The 1 Supporting information for this paper is available from the IUCr electronic archives (Reference: GW5026).

Acta Cryst. (2014). B70, 331–341

Fig. 2 shows the ORTEP (Farrugia, 2012) view of the molecular structure of isoniazid; the geometrical parameters are given in Table S1. The structural parameters of isoniazid are compared with the room-temperature structure reported by Jensen (1952) and one of its derivatives (Xie, 2007). The C—C bond lengths of the pyridine ring almost agree with the reported structure (Jensen, 1952; Xie, 2007), the maximum ˚ . The C2—C6 bond length is variation being 0.014 A ˚ 1.5012 (2) A, which is equal to the reported (Rajalakshmi et ˚ ) obtained from the al., 2011) theoretical bond length (1.505 A structure optimization. This length is much longer than the C—C bond lengths of the pyridine ring; the difference is attributed to the different hybridization nature of the bonds. ˚ ) of the Notably, the average C—C bond length ( 1.3931 A

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research papers Table 2 Hydrogen-bonding parameters of some weak and strong interactions ˚ ,  ). (A D—H  Ai

H  Ai

D  Ai

/D—H  Ai

N3—H3A  N1i N3—H3B  N1ii N2—H2  N2iii N2—H2  N3iii C3—H3  N3iii C1—H1  O1iv C5—H5  O1iv

2.539 2.182 2.770 2.091 2.706 2.587 2.654

3.143 (5) 3.039 (4) 3.439 (4) 2.914 (4) 3.536 (3) 3.252 (4) 3.242 (4)

124.2 (10) 171.2 (10) 136.3 (8) 161.1 (10) 139.3 (8) 125.2 (7) 122.5 (8)

(14) (11) (10) (10) (11) (9) (11)

Symmetry codes: (i) x þ 32 ; y þ 1; þz þ 12; (ii) x þ 52 ; y þ 1; þz þ 12; (iii) x þ 12 ; y þ 32 ; z; (iv) x þ 12 ; y þ 12 ; z.

pyridine ring is almost equal to the C—C bond length of the nicotinamide group present in the NAD+ molecule (Guillot et al., 2003). The C—N bond lengths of the pyridine ring ˚ ] and C6—N2 [1.3469 (2) A ˚ ] are almost equal. [1.3414 (3) A This shows that the C6—N2 bond may have partial doublebond character (Jensen, 1952) similar to the C—N bond present in the pyridine ring. Further, this distance is shorter ˚ ) reported in the theoretical study than the distance (1.371 A (Rajalakshmi et al., 2011). The C—N bond length of the pyridine ring of the isoniazid molecule is almost equal to the ˚ ] of the nicotinamide (Guillot et C—N bond length [1.348 (2) A + al., 2003) group of NAD and is in good agreement with the reported structure (Wardell et al., 2005); however, it is slightly longer than the C—N bond length of the pyridine ring of an optimized structure (Rajalakshmi et al., 2011); the corre˚ . The bond length of the sponding bond length is 1.337 A ˚ , which is equal to the carbonyl C O bond is 1.2319 (2) A reported experimental room-temperature structure (Liu et al., 2005) and the theoretically predicted bond lengths (Rajalakshmi et al., 2011). The bond length of the N—N bond is ˚ , which is exactly equal to the room-temperature 1.4161 (4) A structure (Jensen, 1952; Liu et al., 2005) and the optimized isoniazid molecule (Rajalakshmi et al., 2011), while this bond

length is shorter than the corresponding bond length of one of ˚ ; Wardell et al., 2005]; this difference its derivatives [1.458 (2) A may be attributed to the presence of the nitrobenzaldehyde group in the isoniazid derivative molecule. The torsion angle of C2—C6—N2—N3 is 173.03 (2) ; this wide angle twist indicates that the hydrazide group in the molecule exhibit trans conformation with respect to the pyridine ring and this angle is almost equal to the theoretical structure (Rajalakshmi et al., 2011). The dihedral angle between the pyridine ring and the hydrazide group is 17 , which indicates that they are not coplanar. 3.2. Hydrogen-bonding interactions and Hirshfeld surface analysis

The molecular packing of the crystal is predominantly stabilized by C—H  N, C—H  O and N—H  N types of intermolecular hydrogen-bonding interactions (Table 2). Both H atoms of the NH2 group form N3—H3A  N1i and N3— H3B  N1ii intermolecular hydrogen-bonding interactions with the N1i,ii atoms of neighboring symmetrically sitting molecules in the crystal (Fig. 3). The hydrogen-bond parameters of the strong N3—H3B  N1ii interaction are: ˚ , N3  N1ii 3.039 (4) A ˚ , and the angle H3B  N1ii 2.182 (11) A  is 171.2 (10) . Apart from these interactions, the N2—H2 group also forms a strong intermolecular interaction with the N3 atom of the NH2 group (N2—H2  N3iii) of the neighboring molecule (I), and the N3 atom forms an interaction with the N2—H2iii group of the neighboring molecule (I0 ) N3  H2—N2iii), which lies just above the molecule (I) (Fig. 3). Surprisingly, the hydrogen-bonding parameters of these ˚ , N3  N2iii two interactions [H2  N3iii 2.091 (10) A  ˚ 2.914 (4) A, and the angle is 161.1 (10) ] are found to be equal. These interactions form an infinite spiral type (Jensen, 1952) structure in the crystal. Molecules (I) and (I0 ) also form —

Figure 2 Structure of the isoniazid molecule showing atoms with 50% probability displacement ellipsoids and the atom-numbering scheme. The H atoms are drawn with arbitrary size.

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Figure 3 The hydrogen-bonding interactions of the isoniazid molecule in the crystal.

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Acta Cryst. (2014). B70, 331–341

research papers ˚ [symmetry interactions in the crystal at a distance of 3.760 A 3 1 codes: (i) x þ 2 ; y þ 1; þz þ 2; (ii) x þ 52 ; y þ 1; þz þ 12; (iii) x þ 12 ; y þ 32 ; z]. Intermolecular interactions play an important role in biological recognition of drugs by receptors (Naray-Szabo & Ferenczy, 1995). In particular, the hydrogen-bonding interactions formed between the drug and the receptor provide crucial information for rational drug design. To understand the percentage contribution of intermolecular hydrogenbonding interactions, in recent years Hirshfeld surface analysis has been used to quantify the intermolecular interactions in

crystals. Hirshfeld surface analysis (McKinnon et al., 2004) was performed using CrystalExplorer 3.0 software (Wolff et al., 2007). In isoniazid crystals, the highest contribution of interaction arises from H  H contacts (43.2%). Further, the contribution of N  H interactions is 20.1%, which stabilizes the crystal structure. The contribution of other intermolecular interactions is found to be in decreasing order [O  H (14.4%), C  C (8.8%), C  H (6.7%), C  O (3.9%) and C  N (2.6%)]. 3.3. Charge-density distribution

The featureless residual density map (Fig. S1) reflects the correctness of the multipole model of isoniazid. The deformation density map of isoniazid (Fig. 4) shows the aspherical charge-density distribution and reveals the charge accumulation in various types of bonds and their shapes in the bonding region, and the lone pair position of N and O atoms in the molecule. A critical point search was carried out for the molecule; invariably a (3,1) type of critical point was found for all bonds (Fig. 5), which confirms the covalent sharing of atoms in the molecule. The critical point in the molecule is where the first derivative of the electron density is zero (r = 0). We have characterized the topological properties of electron density at the b.c.p. of all bonds in the molecule. Table 3 shows the topological properties of electron density at the b.c.p. of isoniazid. The electron density bcp(r) of the C—C bonds of the pyridine ring ranges from 2.16 (2) to ˚ 3; the average value is 2.20 e A ˚ 3. The electron 2.23 (1) e A density, bcp(r) , of the C—N bonds of the pyridine ring is ˚ 3, which is equal to the density of the C—N bonds 2.44 e A present in the pyrazine ring of cytosine monohydrate (Munshi & Guru Row, 2006); this value is also almost close to the ˚ 3] of the hydrazide density of the C6—N2 bond [2.37 (2) e A group. The C2—C6 bond exhibits less electron density ˚ 3 compared with all other bonds in the molecule. 1.83 (2) e A The same trend is also found in the theoretical structure, ˚ 3. In the electronwhere the corresponding value is 1.79 e A rich carbonyl C O bond carrying high electron density at the

Figure 4 The experimental (a) static, (b) dynamic and (c) theoretical model deformation density maps of the isoniazid molecule drawn in C1, N1, C3 ˚ 3 intervals. and C6, O1, N3 planes. The contours are drawn at  0.1 e A Solid blue lines represent positive contours, red dotted lines are negative contours and the green dashed lines are zero contours. Acta Cryst. (2014). B70, 331–341

Figure 5 The molecular graph showing the (3,1) and (3,+1) critical points of the isoniazid molecule.

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research papers Table 3 Topological properties of the electron density of isoniazid. The first line indicates the experimental values and the second line indicates the values obtained from the periodic calculation using the B3LYP/6-31G** method. bcp(r) and r2bcp(r): electron density and the Laplacian of electron density at the bcp; 1, 2, 3: eigenvalues; : bond ellipticity; d1, d2: the distance between the b.c.p. and each bonded atom; D: the total bond path length;
d%: the percentage displacement of the b.c.p. from the midpoint of the bond. Bonds

˚ 3) bcp(r) (e A

˚ 5) r2bcp(r) (e A

˚ 5) 1 (e A

˚ 5) 2 (e A

˚ 5) 3 (e A



˚) d1 (A

˚) d2 (A

˚) D (A


d%

C1—C2

2.20 2.09 2.23 2.15 2.16 2.08 1.83 1.79 2.20 2.12 2.39 2.31 2.48 2.34 2.37 2.31 2.14 2.05 2.97 2.78 1.86 1.85 1.84 1.84 1.86 1.85 1.83 1.89 1.92 1.72 2.27 2.22 2.12 1.79

20.6 (1) 17.3 21.6 (1) 19.7 19.8 (1) 17.2 14.7 (1) 13.9 20.5 (1) 19.2 25.7 (1) 23.6 26.2 (1) 23.9 26.6 (1) 26 5.71 (4) 4.9 39.6 (1) 27.2 19.3 (1) 17.4 18.4 (1) 17.1 19.5 (1) 18 17.5 (1) 17.4 24.9 (1) 13.7 27.1 (2) 26.3 25.2 (1) 15.3

16.8 15 16.5 15.7 16.7 14.5 13.8 12.5 16.2 15.6 18.6 18 20.1 18.1 20.3 18.9 17.4 16.6 28.9 24 18.4 17.2 18 17.2 18.4 17.4 17.8 18 23.9 20.4 28.8 28.9 25.1 21

14.9 12.3 14.9 13.5 14.2 12.6 12.9 11.4 14.3 13.1 17.1 15.9 18.6 16.4 17.3 15.8 16.3 15.8 26.3 22.9 17.3 16.6 16.8 16.3 17.4 16.6 16.7 17.5 22.7 19.1 27.5 27.5 23.7 19.8

11.0 10.0 9.8 9.5 11.1 9.9 12.0 10.1 10.0 9.4 9.9 10.3 12.4 10.6 11.1 8.6 28.0 27.5 15.6 19.8 16.5 16.4 16.4 16.4 16.2 16.1 17 16.1 21.7 25.8 29.2 30.1 23.6 25.5

0.13 0.23 0.11 0.4 0.18 0.15 0.07 0.09 0.14 0.19 0.09 0.13 0.08 0.1 0.17 0.2 0.06 0.05 0.1 0.05 0.06 0.03 0.07 0.05 0.06 0.05 0.07 0.03 0.05 0.02 0.05 0.05 0.06 0.06

0.713 0.699 0.675 0.693 0.691 0.708 0.739 0.736 0.689 0.668 0.800 0.792 0.762 0.789 0.798 0.801 0.722 0.724 0.779 0.801 0.732 0.718 0.728 0.717 0.730 0.715 0.732 0.722 0.821 0.805 0.740 0.750 0.791 0.800

0.680 0.695 0.716 0.697 0.706 0.689 0.762 0.765 0.703 0.724 0.542 0.551 0.579 0.552 0.549 0.546 0.694 0.692 0.453 0.431 0.352 0.365 0.356 0.366 0.353 0.368 0.351 0.362 0.279 0.294 0.270 0.260 0.308 0.299

1.393 1.393 1.390 1.390 1.398 1.396 1.502 1.501 1.392 1.392 1.342 1.342 1.342 1.347 1.347 1.347 1.416 1.416 1.232 1.232 1.084 1.083 1.084 1.083 1.083 1.083 1.083 1.083 1.100 1.099 1.010 1.009 1.099 1.099

1.2 0.1 1.5 0.1 0.5 0.7 0.8 0.9 0.5 2.1 9.6 9.0 6.8 8.8 9.3 9.5 0.9 1.1 13.2 15.0 17.6 16.3 17.2 16.2 17.4 16.0 17.8 16.6 24.6 23.2 23.3 24.3 22.0 22.8

C1—C5 C2—C3 C2—C6 C3—C4 C4—N1 C5—N1 C6—N2 N2—N3 C6 O1 C1—H1 C3—H3 C4—H4 C5—H5 N2—H2 N3—H3A N3—H3B

(2) (1) (2) (2) (2) (2) (2) (2) (1) (2) (3) (3) (3) (3) (3) (4) (3)

b.c.p., the experimental and predicted theoretical bcp(r) ˚ 3, respectively, where the values are 2.97 (2) and 2.78 e A experimental value is slightly higher than the reported bcp(r) ˚ 3) of the paracetamol molecule of C O bonds (2.802 e A (Bouhmaida et al., 2009). The bcp(r) value of the N—N bond ˚ 3; this value is almost equal to the electron is 2.14 (1) e A ˚ 3) predicted by the DFT method density bcp(r) (2.13 e A (Rajalakshmi et al., 2011) and it is also close to the reported ˚ 3) of the electron density of the N—NH2 bonds (2.13 e A thiosemicarbazide molecule (Novakovie et al., 2007). Furthermore, this experimental electron density also almost agrees with the density calculated from the periodic theore˚ 3). The average experimental tical calculation (2.05 e A electron density at the b.c.p. of the N—H bond (Novakovie et ˚ 3 and the corresponding theoretical value al., 2007) is 2.10 e A 3 ˚ . The experimental and theoretical electron is 1.91 e A density bcp(r) at the b.c.p. of the C—H bond varies from ˚ 3, respectively. ˚ 3/1.84 to 1.89 e A 1.83 (3) to 1.86 (3) e A These values are in good agreement with the reported values (Novakovie et al., 2007). A bond-path analysis has been carried out on all bonds of isoniazid, which reveals how the b.c.p.s deviate from the internuclear axis (bonds; Table 3).

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3.4. Laplacian of electron density

The Laplacian of electron density r2bcp(r) gives the chemical significance of the bond, i.e. whether the charges are locally concentrated or depleted (Bader, 1990). The Laplacian of electron density, r2bcp(r), of the C—C bonds of the pyridine ring does not vary much as the bcp(r) varies; its average ˚ 5. Notably, the experimental/theoretical value is 20.6 e A 2 ˚ 5] bond r bcp(r) value of the C2—C6 [14.7 (1)/13.9 e A is found to be less negative compared with the other C—C bonds in the molecule; this indicates that, locally, the electron density at the b.c.p. of the C2—C6 bond is less concentrated. This may be due to the effect of the neighbouring high electronegative groups present in the molecule; a similar trend is also found in the theoretical structure of isoniazid (Rajalakshmi et al., 2011). As expected, the experimental and theoretical negative Laplacian values at the b.c.p. of the C—N bonds [C6—N2 26.6 (1)/26.0, C4—N1 25.7 (1)/23.6 and ˚ 5] are found to be high. C5—N1 26.2 (1)/23.9 e A Although the N atoms of the C—N bonds are attached to different groups, the Laplacian values are found to be almost ˚ 5, equal. The Laplacian of the N2—N3 bond is 5.71 (4) e A

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research papers which almost agrees with the value obtained from the periodic ˚ 5); the less negative value of theoretical calculation (4.9 e A the Laplacian indicates that the charges at the b.c.p. of the N— N bond are least accumulated (weak bond) on comparing with all other bonds in the molecule. This can be visualized when we look at the density in the b.c.p. position of the N—N bond (Fig. 4). Further, the r2bcp(r) value calculated at the b.c.p. of the N—N bond obtained from the DFT method (Rajalakshmi ˚ 5) than the et al., 2011) is found to be much higher (12.5 e A value determined by the present experimental study ˚ 5]. This discrepancy may be attributed to the [5.71 (4) e A basis-set effect or insufficient method of calculation. The electron density of the C O bond is highly concentrated compared with all other bonds in the molecule, and the ˚ 5; this value is corresponding Laplacian value is 39.6 (1) e A 2 5 ˚ equal to r bcp(r) [39.7 (2) e A ] of the C O bond present in the l-glutamine (Wagner & Luger, 2001). The charges at the b.c.p. of the N—H bonds are more concentrated than the C—H bond and their average experi˚ 5 and 18.7/ mental/theoretical values are 25.7/18.4 e A 5 2 ˚ 17.5 e A , respectively; the high negative r bcp(r) value of the N—H bonds indicates that the charges of these bonds are highly concentrated comapred with the C—H bonds. The Laplacian of electron density and the corresponding curvature values 1, 2 and 3 at the b.c.p. of all bonds of isoniazid are presented in Table 3. The contour maps (Fig. 6) display the Laplacian of electron density of isoniazid in the pyridine ring

and the hydrazide planes. The lone-pair positions of O1 and N1 atoms are clearly visible.

Figure 6

Figure 7

The experimental (a, b) and theoretical (c, d) negative Laplacian of the electron density of the isoniazid molecule drawn in C1, N1, C3 and C6, ˚ 5, O1, N3 planes. Contours are drawn in logarithmic scale, 3  2N e A where N = 2, 4 and 8  10n, n = 2, 1, 0, 1, 2. Solid blue lines and dotted red lines represent positive and negative contours, respectively.

Trajectory plots showing the gradient vector field of electron density of the isoniazid molecule: (a) pyridine ring, (b) hydrazide and (c) NH2 groups. The closed black thick solid lines around the atoms showing the boundaries of the atomic basin and the red open circles represent the (3,1) critical points.

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research papers Table 4 ˚ 3). Atomic charges (e) and volumes (A Experimental

b3lyp/6-31g**

Atoms

q(Pv)

qAIM

Vtot

qAIM

Vtot

C1 C2 C3 C4 C5 C6 N1 N2 N3 O1 H1 H2 H3 H4 H5 H3A H3B 

0.22 0.24 0.22 0.18 0.28 0.05 0.14 0.28 0.36 0.26 0.22 0.36 0.22 0.22 0.21 0.19 0.23 –

0.11 0.07 0.11 0.29 0.21 1.12 0.93 0.91 0.75 1.06 0.17 0.56 0.19 0.17 0.15 0.39 0.42 –

11.3 9.3 12.1 10.7 11.7 6.5 14.4 13.3 13.9 17.9 5.9 2.1 6.3 6.8 7 3.3 3.4 155.9

0.04 0.02 0.02 0.34 0.36 1.09 0.94 0.76 0.72 1.12 0.1 0.44 0.09 0.09 0.09 0.41 0.4 –

11.3 9.4 11.5 10.2 10.5 6.2 14.3 12.7 13.9 18.1 6.3 2.8 7 7.4 7.3 3.2 3.8 155.8

The bond-energy density distribution of the isoniazid molecule was calculated. The total energy densities, Hbcp(r) (Abramov, 1997; Tsirelson, 2002), of C—N, C O and N—N bonds are 0.5928, 0.8674 and 0.4450 a.u.; the corresponding predicted theoretical values are: 0.5617, 0.7286 and 0.4096 a.u., respectively. The experimental and theoretical potential energy density, Vbcp(r), of C—N, C O and N— N bonds are 0.9103, 1.3234, 0.8300 and 0.8612, 1.1985, 0.7699 a.u., respectively. When the potential energy density Vbcp(r) dominates, the total electronic energy density Hbcp(r) becomes negative; this increases the stability of bonds in the molecule (Cramer & Kraka, 1984). 3.5. Gradient vector field

Fig. 7 shows the gradient vector field of electron density r(r) of the isoniazid molecule plotted using WinXPRO software (Stash & Tsirelson, 2002). Gradient trajectories are originated at atomic centres and terminate at the b.c.p. The thick solid lines represent the zero-flux surfaces of atoms in the molecule, which defines the boundary of the atomic basin. Notably, the high electronegative atoms (O1, N1 and N3) of the molecule exhibit a larger volume than all the other atoms in the molecule. Interestingly, the value of N2 and all the C atoms in the molecule are prismatic in shape. Due to the asphericity of the valence electron density the gradient lines are dominant in the core of the atomic basin and decrease ˚ 3, away from the nucleus. The atomic volume of O1 is 17.92 A which is larger than all the other atoms in the molecule and a ˚ 3). The volume similar trend is also observed in theory (18.06 A 3 ˚ , which is slightly less compared with of the N2 atom is 13.28 A 3 ˚ 3) atoms. The same scenario is ˚ N1 (14.39 A ) and N3 (13.92 A observed in the theoretical calculation (Table 4). The atomic ˚ 3 and agrees well volume of hydrogen varies from 2.1 to 7.0 A with the reported values (Stevens et al., 2010) in which the volumes of the H atoms H2, H3A and H3B are less than the other H atoms; perhaps this volume difference is attributed to

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their involvement in hydrogen-bonding interactions (Koch & Popelier, 1995). The correctness of the experimental model has been verified by the theoretically calculated AIM volume. ˚ 3, which The AIM volume of the isoniazid molecule is 623.5 A ˚ 3 deteris exactly equal to the unit-cell volume of 623.58 A mined from the X-ray diffraction. The various calculated model atomic charges and the corresponding atomic volumes are given in Table 4. 3.6. Atomic charges and electrostatic potential

The AIM (Bader, 1991) charges of isoniazid have been calculated using TOPXD (Volkov et al., 2000) software (Table 4). As expected, the O1 atom carries a high negative charge (1.06 e) with a corresponding theoretical value of 1.12 e. The C6 atom possesses a high positive charge of 1.12 e as it is attached to the more electronegative O atom, thus this bond is highly polarized. The N1 and N2 atoms carry an equal amount of negative charge and the values obtained from both experiment and theory are 0.93/0.94 e and 0.91/0.76 e, respectively, which are slightly higher than the N3 atom (0.75/0.72 e). The charges of the H atoms H3A, H3B and H2 are more positive than all the other H atoms in the molecule. The molecular electrostatic potential map (ESP) is the visualization of a potential when a proton or other point positive charge is brought near the molecule (Zhu et al., 2005). In ligand–receptor interactions, the ESP provides information about the complementarity between the ligand and the receptor (Politzer & Murray, 2002). It is used to predict the chemically reactive nature of the molecule as negative regions are the sites of protonation and nucleophilic attack, while the regions of positive potential are the electrophilic sites. Fig. 8 depicts the electrostatic potential map of isoniazid, which displays the highly electronegative regions in the vicinity of the O1, N1 and N3 atoms. Although the N2 atom carries negative charge, no electronegative region is found in its vicinity. This may be due to the group charge effect and a similar trend is also observed in the theoretical ESP map (Rajalakshmi et al., 2011). The O1, N1 and N3 atoms are the

Figure 8 The isosurface representation of the molecular electrostatic potential of ˚ 1 (blue) the isoniazid molecule. Positive potentials are drawn at +0.3 e A ˚ 1 (red). and the negative potential is drawn at 0.1 e A

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research papers Table 5 Topological properties of hydrogen bonds. Interactions H3 A  N1i ii

H3B  N1 H2  N2iii H2  N3iii H3  N3iii H1  O1iv H5  O1iv

bcp(r) ˚ 3) (e A

r2bcp(r) ˚ 3) (e A

1 ˚ 5) (e A

2 ˚ 5) (e A

3 ˚ 5) (e A

d1 ˚) (A

d2 ˚) (A

Rij ˚) (A

G(r) (a.u.)

V(r) (a.u.)

H(r) (a.u.)

D (kJ mol1)

0.054 (2) 0.06 0.08 (1) 0.153 0.026 (2) 0.028 0.14 (2) 0.213 0.036 (2) 0.043 0.041 (1) 0.049 0.048 (1) 0.046

0.871 (1) 0.874 3.46 (1) 2.904 0.547 (1) 0.5 3.53 (1) 3.357 0.619 (1) 0.678 0.754 (1) 0.791 0.727 (1) 0.727

0.21 0.22 0.34 0.75 0.11 0.09 0.8 1.18 0.16 0.15 0.14 0.18 0.16 0.18

0.18 0.21 0.24 0.74 0.05 0.06 0.62 1.14 0.11 0.07 0.13 0.16 0.15 0.16

1.26 1.31 4.05 4.40 0.70 0.65 4.95 5.68 0.89 0.91 1.02 1.14 1.04 1.14

1.054 1.04 0.645 0.668 1.133 1.109 0.618 0.616 1.109 1.103 1.077 1.103 1.141 1.103

1.469 1.476 1.34 1.284 1.66 1.537 1.295 1.25 1.583 1.591 1.476 1.447 1.455 1.447

2.523 2.516 1.985 1.952 2.793 2.646 1.913 1.866 2.692 2.694 2.553 2.55 2.597 2.55

0.005 0.007 0.026 0.025 0.004 0.004 0.029 0.032 0.005 0.005 0.006 0.006 0.006 0.006

0.001 0.004 0.016 0.020 0.023 0.028 0.021 0.029 0.003 0.003 0.004 0.004 0.004 0.004

0.004 0.002 0.01 0.005 0.002 0.001 0.008 0.003 0.002 0.002 0.002 0.002 0.002 0.002

1.76 5.23 20.35 26.29 30.29 36.80 6.64 38.10 4.02 3.94 5.23 5.23 5.28 5.28

D is the bond dissociation energy. Symmetry codes: (i) x þ 32 ; y þ 1; þz þ 12; (ii) x þ 52 ; y þ 1; þz þ 12; (iii) x þ 12 ; y þ 32 ; z; (iv) x þ 12 ; y þ 12 ; z.

possible reactive locations of the molecule and these atoms form strong hydrogen-bonding interactions with neighbouring amino acid residues present in the active site of the InhA protein molecule (Rozwarski et al., 1998). The ESP and the atomic charges can be used to understand the alignment of isoniazid in the active site of InhA. Rozwarski et al. (1998) reports explicitly about the nature of the interaction between the InhA protein and isoniazid (1zid), in which the electronegative region N1 atom interacts with water via a hydrogen bond and the carbonyl oxygen O1 atom forms a hydrogen bond with the neighbouring amide group of the nicotinamide ring, and with one of the hydroxyl groups of diol at the ribose ring near the nicotinamide. Thus it may block the interaction of one of the diol groups in the co-enzyme NADH with the N atom of the amino acid residue Lys165. Similarly, it prevents the interaction of the amide group of nicotinamide with the carbon and sulfur group of the amino acid residue Met199, which reduces the binding affinity of NADH with the receptor. The ESP map shows the maximum positive electrostatic potential surface over the pyridine ring, hence the pyridine ring is involved in the -stacking interaction with Phe149. A large electronegative region is present around the O1, N1 and N3 atoms. The large electronegative N1 atom presumably forms a strong intermolecular hydrogen bond with water. The strong electronegative region around the N3 atom results in the formation of a strong interaction with the C and S atoms of Met199 amino acid residues present in the active site of the Inha enzyme. The surface around the O1 atom shows its electrophilicity nature with the co-enzyme NADH. Isoniazid is a polar molecule, its dipole moment is 4.4 (2) D; this value is significantly higher than the corresponding theoretical value (Rajalakshmi et al., 2011; 2.04 D). The large dipole moment enhancement of the molecule in the crystal is mainly attributed to the intermolecular interaction in the crystal (Koritsanszky & Coppens, 2001), as these interactions are absent in the gas phase (Rajalakshmi et al., 2011). Acta Cryst. (2014). B70, 331–341

3.7. Topological analysis of hydrogen-bonding interactions

The isoniazid molecule in the crystal forms weak and strong intermolecular interactions in the crystal (Table 2). The N— H  N, C—H  N and C—H  O types of interactions are present in the crystal in which the N—H  N interaction is considered to be an important interaction, playing an important role in forming the structure of giant molecules such as protein, RNA and DNA, and also in drug–receptor interactions (Reji & Kulkarni, 2007). The investigation of the topological properties of strong and weak hydrogen-bonding interactions is necessary, as it provides information about the molecular recognition (Desiraju, 1995; Desiraju & Steiner, 1999). In recent years, several experimental and theoretical studies (Schiott et al., 1998; Overgaard & Iversen, 2012; Madsen et al., 2011; Madsen, 2012) outline the topological properties of hydrogen-bonding interactions. Here we have calculated such properties for various types of hydrogenbonding interactions (Table 5). A critical point search was carried out on all hydrogen bonds (Table 2) which gave a (3,1) type of critical point. The electron density, bcp(r), of the hydrogen bonds H2  N3iii, H3A  N1ii and H3B  N(1)(i) are 0.14 (1), 0.08 (1) and ˚ 3, respectively. The corresponding Laplacian of 0.054 (2) e A the electron densities r2bcp(r) are: 3.53 (1), 3.46 (1) and ˚ 5, respectively. The positive value of the 0.871 (1) e A Laplacian r2bcp(r) > 0, |V|/G < 1 and Hbcp(r) > 0 of hydrogenbonding interactions show that these interactions are closedshell type (Gatti, 2005). From bond dissociation energy (BDE; Espinosa & Molins, 2000; Table 5) it is clear that the C— H  N and C—H  O bonds are much weaker than N—H  N hydrogen-bonding interactions. Figs. 9(a)–(d) show the Laplacians of the N—H  N hydrogen-bonding interactions, showing the polarization of the lone-pair lobes of N atoms towards its corresponding H atoms and the N atoms of the neighbouring molecule through its corresponding H atoms. The map clearly shows the interacting N atoms and the posi-

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research papers The authors thank Professor T. N. Guru Row for collecting the high-resolution X-ray intensity data and GR thanks UGC for providing a UGC Non-SAP fellowship to carry out this research work.

References

Figure 9 Laplacian maps showing the (a) N3—H3A  N1i, (b) N3—H3B  N1ii, (c) N2—H2  N2iii and (d) N2—H2  N3iii hydrogen-bonding interac˚ 5, where N = tions. Contours are drawn in a logarithmic scale, 3  2N e A 2, 4 and 8  10n, n = 2, 1, 0, 1, 2. Solid blue lines and dotted red lines represent positive and negative contours, respectively. X1, X2 and X3 represent the symmetry codes: (i) x þ 32 ; y þ 1; þz þ 12; (ii) x þ 52 ; y þ 1; þz þ 12; (iii) x þ 12 ; y þ 32 ; z.

tions of the H atoms of hydrogen bonds [symmetry codes: (i) x þ 32 ; y þ 1; þz þ 12; (ii) x þ 52 ; y þ 1; þz þ 12; (iii) x þ 12 ; y þ 32 ; z].

4. Conclusion The experimental charge-density analysis of isoniazid was carried out to understand its topological and electrostatic properties of the molecule; the results were compared with the periodic theoretical calculations. The C O bond has a high negative Laplacian of electron density; this is a relatively highly polarized bond in the molecule. The charges of the N— N bond is least accumulated. In the ESP map a high electronegative region is found in the vicinity of the O1 and N1 atoms; a similar trend is also observed in theory. Furthermore, these two atoms also form more hydrogen-bonding interactions with the symmetrically sitting neighbouring molecules in the crystal. The Hirshfeld surface analysis explores the contribution of different types of intermolecular interactions of the isoniazid molecule in the crystal. The fine structural and electronic parameters obtained from the high-resolution Xray diffraction measurement may be useful to design a new isoniazid drug molecule with enhanced pharmacological activity to treat the TB disease.

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Abramov, Yu. A. (1997). Acta Cryst. A53, 264–272. Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Guy, O. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–S19. Bader, R. F. W. (1990). Atoms in Molecules. A Quantum Theory. Oxford: Clarendon Press. Bader, R. F. W. (1991). Chem. Rev. 91, 893–928. Basso, L. A. & Blanchard, J. S. (1998). Adv. Exp. Med. Biol. 456, 115– 144. Bastian, I. & Colebunders, R. (1999). Drugs, 58, 633–661. Becke, A. D. (1993). J. Chem. Phys. 98, 5648–5652. Blessing, R. H. (1997). J. Appl. Cryst. 30, 421–426. Bloom, B. R. (1994). Tuberculosis: Pathogenesis, Protection and Control. Washington, DC: American Society for Microbiology Press. Bouhmaida, N., Bonhomme, F., Guillot, B., Jelsch, C. & Ghermani, N. E. (2009). Acta Cryst. B65, 363–374. Bruker (2000). APEX. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2006). APEX2, Version 1.0.22, BIS, Version 1.2.08, COSMO, Version 1.48, and SAINT, Version 7.06A. Bruker AXS Inc., Madison, Wisconsin, USA. Cramer, D. & Kraka, E. (1984). Croat. Chem. Acta, 57, 1259–1281. Desiraju, G. R. (1995). Angew. Chem. Int. Ed. 34, 2311–2327. Desiraju, G. R. & Steiner, T. (1999). The Weak Hydrogen Bonds in Structural Chemistry and Biology. Oxford University Press. Dovesi, R., Orlando, R., Civalleri, B., Roetti, C., Saunders, V. R. & Zicovich-Wilson, C. M. (2005). Z. Kristallogr. 220, 571–573. Dovesi, R., Saunders, V. R., Roetti, C., Orlando, R., Zicovich-Wilson, C. M., Pascale, F., Civalleri, B., Doll, K., Harrison, N. M., Bush, I. J. D’Arco, P. & Llunell, M. (2009). CRYSTAL09 User’s Manual. University of Torino, Italy. Draskovic, B. M., Bogdanovic, G. A., Neelakantan, M. A., Chamayou, A. C., Thalamuthu, S., Avadhut, Y. S., Gunne, J. S. A. D., Banerjee, S. & Janiak, C. (2010). Cryst. Growth Des. 10, 1665–1676. Dye, C., Garnett, G. P., Sleeman, K. & Williams, B. G. (1998). Lancet, 352, 1886–1891. Espinosa, E. & Molins, E. (2000). J. Chem. Phys. 113, 5686–5694. Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Friedland, G. (2007). Curr. Infect. Dis. Rep. 9, 252–261. Gatti, G. (2005). Z. Kristallogr. 220, 399–457. Gautam, R., Saklani, A. & Jachak, S. M. (2007). J. Ethnopharmacol. 110, 200–234. Guillot, B., Muze, N., Artacho, E., Lecomte, C. & Jelsch, C. (2003). J. Phys. Chem. B, 107, 9109–9121. Hansen, N. K. & Coppens, P. (1978). Acta Cryst. A34, 909–921. Hariharan, P. C. & Pople, J. A. (1973). Theor. Chim. Acta, 28, 213–222. Jensen, L. H. (1952). J. Am. Chem. Soc. 76, 4663–4667. Johnsson, K. & Schultz, P. G. (1994). J. Am. Chem. Soc. 116, 7425– 7426. Koch, U. & Popelier, P. L. A. (1995). J. Chem. Phys. 99, 9747–9754. Koritsanszky, T. S. & Coppens, P. (2001). Chem. Rev. 101, 1583–1627. Lee, C., Yang, W. & Parr, R. G. (1998). Phys. Rev. B, 37, 785–789. Lenaerts, A. J., Degroote, M. A. & Orme, I. M. (2008). Trends Microbiol. 16, 48–54. Liu, W., Ma, Y., Wang, R.-J., Yin, Y.-W. & Zhao, Y.-F. (2005). Acta Cryst. E61, o3069–o3070. Madsen, A. O. (2012). Struct. Bond. 146, 21–52. Madsen, A. Ø, Mattson, R. & Larsen, S. (2011). J. Phys. Chem. A, 115, 7794–7804. McKinnon, J. J., Spackman, M. A. & Mitchell, A. S. (2004). Acta Cryst. B60, 627–668.

Isoniazid: experimental and theoretical study

Acta Cryst. (2014). B70, 331–341

research papers Middlebrook, G. (1952). Am. Rev. Tuberc. 65, 765–767. Munshi, P. & Guru Row, T. N. (2006). Acta Cryst. B62, 612– 626. Naray-Szabo, G. & Ferenczy, G. G. (1995). Chem. Rev. 95, 829– 847. Novakovie, S. B., Bogdanovie, G. A., Fraisse, B., Ghermani, N. E., Bouhmaida, N. & Bire, A. S. (2007). J. Phys. Chem. A, 111, 13492– 13505. Overgaard, J. & Iversen, B. B. (2012). Struct. Bond. 146, 53–74. Parrish, D., Zhurova, E. A., Kirschbaum, K. & Pinkerton, A. A. (2006). J. Phys. Chem. B, 110, 26442–26447. Patralekha, C. (2008). Lancet Infect. Dis. 8, 354. Politzer, P. & Murray, J. S. (2002). Theor. Chem. Acc. 108, 134–142. Quemard, A., Lacave, C. & Laneelle, G. (1991). Antimicrob. Agents Chemother. 35, 1035–1039. Rajalakshmi, G., Devipriya, B., Parameswari, A. R., Stephen, A. D. & Kumaradhas, P. (2011). Comput. Theor. Chem. 966, 259–264. Reji, T. & Kulkarni, G. U. (2007). Beilstein J. Org. Chem. 3, 1. Rozwarski, D. A., Grant, G. A., Barton, D. H., Jacobs, W. R. & Sacchettini, J. C. (1998). Science, 279, 98–102. Sacchettini, J. C. & Blanchard, J. S. (1996). Res. Microbiol. 147, 36–43. Schiott, B., Iverson, B., Madsen, G. K. H. & Bruice, T. C. (1998). J. Am. Chem. Soc. 120, 12117–12124. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Stash, A. & Tsirelson, V. (2002). J. Appl. Cryst. 35, 371–373. Stevens, E. D., Dowd, M. K., Johnson, G. P. & French, A. D. (2010). Carbohydr. Res. 345, 1469–1481.

Acta Cryst. (2014). B70, 331–341

Takayama, K., Warg, L. & David, H. L. (1972). Antimicrob. Agents Chemother. 2, 29–35. Tsirelson, V. G. (2002). Acta Cryst. B58, 632–639. Vijay, V., Raghuvir, R. S. P., Dinesh, M., Chintan, D., Priti, A., Anamik, S. & Evans, C. C. (2007). Eur. J. Med. Chem. 15, 1–13. Volkov, A., Abramov, Y. A. & Coppens, P. (2001). Acta Cryst. A57, 272–282. Volkov, A., Gatti, C., Abramov, Y. & Coppens, P. (2000). Acta Cryst. A56, 252–258. Volkov, A., Macchi, P., Farrugia, L. J., Gatti, C., Mallinson, P. R., Richter, T. & Koritsanszky, T. (2006). XD2006. University at Buffalo, State University of New York, NY, USA; University of Milano, Italy; University of Glasgow, UK; CNRISTM, Milano, Italy; Middle Tennessee State University, TN, USA. Wagner, A. & Luger, P. (2001). J. Mol. Struct. 595, 39–46. Wardell, S. M. S. V., de Souza, M. V. N., Wardell, J. L., Low, J. L. & Glidewell, C. (2005). Acta Cryst. C61, o683–o689. Winder, F. G., Ratledge, C. & Stanford, J. (1982). Editors. The Biology of Mycobacteria, pp. 354–438. London: Academic Press. Wolff, S. K., Grimwood, D. J., McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). CrystalExplorer 3.0. University of Western Australia, Perth. World Health Organization (2002). Tuberculosis. WHO Fact Sheets, No. 104. World Health Organization, Geneva. Xie, Z.-Y. (2007). Acta Cryst. E63, o2956. Zhang, Y. & Mitchison, D. (2003). Int. J. Tuberc. Lung Dis. 7, 6–21. Zhu, N., Klein Stevens, C. L. & Stevens, E. D. (2005). J. Chem. Cryst. 35, 13–22.

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