organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

N′-[(1E)-4-Hy­dr­oxy-3-meth­­oxy­benzyl­idene]isonicotinohydrazide monohydrate

aDepartment of Physics, Yuvaraja's College (Constituent College), University of Mysore, Mysore 570 005, Karnataka, India, bDepartment of Pharmaceutical Chemistry, JSS College of Pharmacy, JSS University, Mysuru 570 015, Karnataka, India, and cDepartment of Pharmaceutical Chemistry, Sri Adichunchanagiri College of Pharmacy, B G Nagara, Mandya District 571 448, Karnataka, India
*Correspondence e-mail: devarajegowda@yahoo.com

Edited by R. J. Butcher, Howard University, USA (Received 1 June 2016; accepted 11 August 2016; online 26 August 2016)

In the title hydrate, C14H13N3O3·H2O, the dihedral angle between the pyridine and benzene rings is 2.52 (9)°. Intra­molecular O—H⋯O hydrogen bonds occur. In the crystal, O—H⋯O, O—H⋯N, N—H⋯O and C—H⋯O hydrogen bonds link the components into a three-dimensional network. ππ inter­actions are also observed.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Hydrazones have been reported to be anti­tubercular (Vavříková et al., 2011[Vavříková, E., Polanc, S., Kočevar, M., Košmrlj, J., Horváti, K., Bősze, S., Stolaříková, J., Imramovský, A. & Vinšová, J. (2011). Eur. J. Med. Chem. 46, 5902-5909.]; Koçyiğit Kaymakçıoğlu & Rollas, 2002[Koçyiğit Kaymakçıoğlu, B. & Rollas, S. (2002). Farmaco, 57, 595-599.]), anti­cancer (Bhat et al., 2015[Bhat, M. A., Iqbal, M., Al-Dhfyan, A. & Shakeel, F. (2015). J. Mol. Liq. 203, 111-119.]), anti­fungal, anti­microbial, anti­viral and anti­malarial agents (Maccari et al., 2005[Maccari, R., Ottanà, R. & Vigorita, M. G. (2005). Bioorg. Med. Chem. Lett. 15, 2509-2513.]; Mallikarjuna et al., 2009[Mallikarjuna, B. P., Sastry, B. S., Suresh Kumar, G. V., Rajendraprasad, Y., Chandrashekar, S. M. & Sathisha, K. (2009). Eur. J. Med. Chem. 44, 4739-4746.]; Bekhit et al., 2015[Bekhit, A. A., Hassan, A. M. M., Abd El Razik, H. A., El-Miligy, M. M. M., El-Agroudy, E. J. & Bekhit, A. E. A. (2015). Eur. J. Med. Chem. 94, 30-44.]). The development of new classes of hydrazones may overcome anti­microbial resistance.

The asymmetric unit of the title compound is shown in Fig. 1[link]. The dihedral angle between the pyridine ring and the benzene rings is 2.52 (9)°. Intra­molecular O—H⋯O hydrogen bonds (Table 1[link]) occur. In the crystal, O—H⋯O, O—H⋯N, N—H⋯O and C—H⋯O hydrogen bonds (Table 1[link]) link the components into a three-dimensional network. In addition, ππ inter­actions are observed between the pyridine and benzene rings of neighbouring mol­ecules with centroid–centroid distances of 3.8251 (11) and 3.8984 (11) Å. The crystal packing is illustrated in Fig. 2[link].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O2—H2⋯O1 1.00 (3) 2.24 (3) 2.7081 (18) 107.4 (18)
O2—H2⋯N5i 1.00 (3) 1.79 (3) 2.699 (2) 150 (2)
O4—H4A⋯O2ii 0.73 (4) 2.28 (4) 2.986 (2) 163 (4)
O4—H4B⋯O3 0.92 (3) 1.93 (3) 2.832 (3) 166 (3)
N6—H6⋯O4iii 0.89 (2) 2.10 (2) 2.976 (2) 169 (2)
C8—H8A⋯O3iv 0.95 (2) 2.51 (2) 3.390 (3) 154 (2)
C15—H15⋯O4iii 1.00 (2) 2.58 (2) 3.436 (3) 143.1 (14)
C18—H18⋯O4iii 0.977 (18) 2.316 (18) 3.272 (3) 165.9 (16)
C20—H20⋯O1v 0.94 (2) 2.56 (2) 3.189 (2) 124.5 (17)
Symmetry codes: (i) [x-{\script{3\over 2}}, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]; (ii) x+1, y, z; (iii) [-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]; (iv) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]; (v) [x+{\script{3\over 2}}, -y+{\script{3\over 2}}, z-{\script{1\over 2}}].
[Figure 1]
Figure 1
The mol­ecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms are shown as spheres of arbitrary radius.
[Figure 2]
Figure 2
The packing of mol­ecules. Hydrogen bonds are shown as dashed lines.

Synthesis and crystallization

Equimolar qu­anti­ties of vanillin (50 mmol) and isonicotinic acid hydrazide (50 mmol) were heated to reflux in the presence of absolute ethanol (50 ml) for 6 h; the completion of the reaction was monitored by TLC. After cooling and concentration of reaction mixture, the product was added to ice-cold water. The precipitated product was collected and dried. The crude product was recrystallized from 70 v/v ethanol solution, affording colourless prismatic crystals (yield 82%).

Spectroscopic data: IR (KBr disk, cm-1) 3356 (OH), 3324 (NH), 2969 (C—H), 1590 (Ar—C=C), 1265 (–OCH3); 1H NMR (400 MHz, DMSO-d6): 11.85 (s, 1H), 9.58 (s, 1H), 8.75 (s, 2H), 8.32 (s, 1H), 7.79 (d, 2H), 7.30 (d, 1H), 7.10 (dd, 1H), 6.83 (d, 1H). 3.81 (s, 3H); LC–MS m/z: 272.15 (M + H)+.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C14H13N3O3·H2O
Mr 289.29
Crystal system, space group Monoclinic, P21/n
Temperature (K) 296
a, b, c (Å) 8.3687 (7), 13.0913 (10), 12.6778 (11)
β (°) 99.086 (5)
V3) 1371.5 (2)
Z 4
Radiation type Cu Kα
μ (mm−1) 0.88
Crystal size (mm) 0.24 × 0.20 × 0.12
 
Data collection
Diffractometer Bruker SMART CCD area-detector
Absorption correction Multi-scan (SADABS; Sheldrick, 2007[Sheldrick, G. M. (2007). SADABS. University of Göttingen, Germany.])
Tmin, Tmax 0.770, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 7361, 2249, 1805
Rint 0.042
(sin θ/λ)max−1) 0.586
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.114, 1.04
No. of reflections 2249
No. of parameters 251
H-atom treatment All H-atom parameters refined
Δρmax, Δρmin (e Å−3) 0.25, −0.25
Computer programs: SMART and SAINT (Bruker, 2001[Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014/7 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) and ORTEP-3 for Windows (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]).

Structural data


Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015b).

N'-[(1E)-4-Hydroxy-3-methoxybenzylidene]isonicotinohydrazide monohydrate top
Crystal data top
C14H13N3O3·H2ODx = 1.401 Mg m3
Mr = 289.29Melting point: 298 K
Monoclinic, P21/nCu Kα radiation, λ = 1.54178 Å
a = 8.3687 (7) ÅCell parameters from 2249 reflections
b = 13.0913 (10) Åθ = 4.9–64.5°
c = 12.6778 (11) ŵ = 0.88 mm1
β = 99.086 (5)°T = 296 K
V = 1371.5 (2) Å3Prism, colourless
Z = 40.24 × 0.20 × 0.12 mm
F(000) = 576
Data collection top
Bruker SMART CCD area-detector
diffractometer
2249 independent reflections
Radiation source: fine-focus sealed tube1805 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.042
ω and φ scansθmax = 64.5°, θmin = 4.9°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2007)
h = 79
Tmin = 0.770, Tmax = 1.000k = 1415
7361 measured reflectionsl = 1412
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullAll H-atom parameters refined
R[F2 > 2σ(F2)] = 0.043 w = 1/[σ2(Fo2) + (0.059P)2 + 0.2398P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.114(Δ/σ)max = 0.001
S = 1.04Δρmax = 0.25 e Å3
2249 reflectionsΔρmin = 0.25 e Å3
251 parametersExtinction correction: SHELXL-2014/7 (Sheldrick 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0065 (7)
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.01283 (15)0.81847 (9)0.90314 (11)0.0528 (4)
O20.04008 (15)0.61830 (10)0.93903 (12)0.0539 (4)
O30.81796 (17)0.55219 (9)0.64551 (13)0.0627 (4)
O40.7956 (2)0.43537 (13)0.83061 (19)0.0730 (5)
N51.22351 (17)0.77082 (12)0.50647 (12)0.0476 (4)
N60.72171 (17)0.70837 (12)0.67777 (13)0.0439 (4)
N70.59405 (17)0.66654 (11)0.72119 (12)0.0469 (4)
C80.0359 (3)0.92178 (15)0.8789 (2)0.0645 (7)
C90.12124 (18)0.74987 (12)0.87380 (13)0.0378 (4)
C100.25461 (19)0.77494 (14)0.82747 (14)0.0404 (4)
C110.35901 (19)0.69995 (13)0.80039 (14)0.0413 (4)
C120.3261 (2)0.59800 (14)0.82145 (16)0.0478 (5)
C130.1922 (2)0.57302 (13)0.86640 (16)0.0468 (5)
C140.0886 (2)0.64756 (13)0.89347 (14)0.0400 (4)
C150.4981 (2)0.73119 (15)0.75230 (15)0.0452 (5)
C160.8276 (2)0.64568 (13)0.64171 (14)0.0411 (4)
C170.96296 (18)0.69426 (12)0.59529 (13)0.0361 (4)
C180.9779 (2)0.79793 (13)0.57671 (15)0.0423 (4)
C191.1081 (2)0.83129 (14)0.53230 (15)0.0446 (5)
C201.2073 (2)0.67153 (15)0.52461 (19)0.0570 (6)
C211.0808 (2)0.63071 (14)0.56764 (17)0.0499 (5)
H20.106 (3)0.678 (2)0.955 (2)0.107 (9)*
H60.731 (3)0.7757 (18)0.6774 (16)0.058 (6)*
H100.283 (2)0.8450 (16)0.8173 (16)0.058 (6)*
H130.168 (2)0.5017 (16)0.8816 (16)0.064 (6)*
H180.900 (2)0.8477 (15)0.5953 (15)0.055 (5)*
H120.402 (3)0.5455 (15)0.8037 (16)0.063 (6)*
H191.118 (2)0.9016 (16)0.5182 (16)0.058 (6)*
H150.519 (2)0.8058 (17)0.7452 (15)0.057 (6)*
H211.075 (3)0.5576 (17)0.5790 (17)0.068 (6)*
H201.289 (3)0.6279 (17)0.5081 (17)0.070 (7)*
H8A0.051 (3)0.9615 (18)0.8970 (19)0.080 (7)*
H8B0.143 (3)0.9463 (18)0.918 (2)0.089 (8)*
H8C0.031 (3)0.930 (2)0.792 (2)0.102 (9)*
H4B0.785 (4)0.475 (2)0.770 (2)0.103 (10)*
H4A0.841 (4)0.472 (3)0.867 (3)0.132 (15)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0479 (7)0.0351 (7)0.0847 (10)0.0084 (5)0.0386 (7)0.0072 (6)
O20.0455 (8)0.0385 (7)0.0868 (11)0.0000 (5)0.0386 (7)0.0034 (6)
O30.0569 (8)0.0407 (7)0.1011 (12)0.0071 (6)0.0452 (8)0.0036 (7)
O40.0819 (12)0.0538 (9)0.0861 (13)0.0240 (8)0.0218 (10)0.0032 (9)
N50.0380 (8)0.0474 (8)0.0618 (10)0.0014 (6)0.0216 (7)0.0035 (7)
N60.0354 (8)0.0421 (9)0.0599 (10)0.0036 (6)0.0250 (7)0.0039 (7)
N70.0346 (8)0.0539 (9)0.0576 (10)0.0046 (7)0.0237 (7)0.0048 (7)
C80.0622 (14)0.0354 (10)0.105 (2)0.0109 (9)0.0420 (14)0.0106 (11)
C90.0327 (8)0.0353 (9)0.0485 (10)0.0047 (7)0.0156 (7)0.0002 (7)
C100.0348 (9)0.0390 (9)0.0504 (11)0.0001 (7)0.0160 (7)0.0013 (8)
C110.0335 (9)0.0479 (10)0.0457 (10)0.0003 (7)0.0161 (7)0.0029 (8)
C120.0411 (10)0.0431 (10)0.0642 (12)0.0057 (8)0.0240 (9)0.0066 (9)
C130.0429 (10)0.0358 (9)0.0667 (13)0.0015 (7)0.0235 (9)0.0030 (9)
C140.0351 (9)0.0388 (9)0.0498 (10)0.0018 (7)0.0183 (7)0.0005 (7)
C150.0377 (10)0.0501 (11)0.0516 (11)0.0004 (8)0.0185 (8)0.0023 (8)
C160.0327 (9)0.0404 (9)0.0535 (11)0.0031 (7)0.0170 (7)0.0030 (8)
C170.0283 (8)0.0389 (8)0.0429 (10)0.0011 (6)0.0116 (7)0.0035 (7)
C180.0356 (9)0.0384 (9)0.0557 (11)0.0010 (7)0.0155 (8)0.0042 (8)
C190.0394 (10)0.0378 (10)0.0596 (12)0.0038 (7)0.0170 (8)0.0012 (8)
C200.0459 (11)0.0466 (11)0.0870 (16)0.0072 (9)0.0371 (10)0.0075 (10)
C210.0434 (10)0.0378 (10)0.0744 (14)0.0033 (8)0.0280 (9)0.0049 (9)
Geometric parameters (Å, º) top
O1—C91.3691 (19)C10—C111.393 (2)
O1—C81.407 (2)C10—H100.96 (2)
O2—C141.355 (2)C11—C121.397 (3)
O2—H20.99 (3)C11—C151.455 (2)
O3—C161.228 (2)C12—C131.374 (3)
O4—H4B0.92 (3)C12—H120.99 (2)
O4—H4A0.73 (3)C13—C141.384 (2)
N5—C191.329 (2)C13—H130.98 (2)
N5—C201.331 (2)C15—H151.00 (2)
N6—C161.340 (2)C16—C171.498 (2)
N6—N71.389 (2)C17—C211.377 (2)
N6—H60.88 (2)C17—C181.386 (2)
N7—C151.272 (2)C18—C191.375 (3)
C8—H8A0.95 (3)C18—H180.97 (2)
C8—H8B1.01 (3)C19—H190.94 (2)
C8—H8C1.10 (3)C20—C211.373 (3)
C9—C101.380 (2)C20—H200.94 (2)
C9—C141.397 (2)C21—H210.97 (2)
C9—O1—C8116.83 (14)C12—C13—H13120.9 (12)
C14—O2—H2111.8 (16)C14—C13—H13117.9 (13)
H4B—O4—H4A97 (3)O2—C14—C13118.52 (15)
C19—N5—C20116.19 (16)O2—C14—C9122.53 (15)
C16—N6—N7119.02 (15)C13—C14—C9118.95 (16)
C16—N6—H6123.2 (15)N7—C15—C11121.94 (18)
N7—N6—H6117.8 (15)N7—C15—H15119.6 (12)
C15—N7—N6115.06 (15)C11—C15—H15118.4 (12)
O1—C8—H8A109.6 (15)O3—C16—N6123.10 (16)
O1—C8—H8B109.9 (14)O3—C16—C17119.78 (15)
H8A—C8—H8B111 (2)N6—C16—C17117.12 (15)
O1—C8—H8C109.3 (14)C21—C17—C18117.44 (16)
H8A—C8—H8C106 (2)C21—C17—C16117.37 (15)
H8B—C8—H8C111 (2)C18—C17—C16125.18 (15)
O1—C9—C10125.07 (15)C19—C18—C17118.63 (16)
O1—C9—C14115.08 (14)C19—C18—H18119.2 (12)
C10—C9—C14119.85 (15)C17—C18—H18122.1 (12)
C9—C10—C11121.21 (16)N5—C19—C18124.45 (17)
C9—C10—H10120.9 (13)N5—C19—H19116.3 (13)
C11—C10—H10117.7 (13)C18—C19—H19119.3 (13)
C10—C11—C12118.41 (16)N5—C20—C21123.69 (18)
C10—C11—C15118.65 (16)N5—C20—H20117.2 (14)
C12—C11—C15122.94 (16)C21—C20—H20119.1 (14)
C13—C12—C11120.34 (16)C20—C21—C17119.60 (17)
C13—C12—H12121.8 (12)C20—C21—H21120.1 (14)
C11—C12—H12117.8 (12)C17—C21—H21120.3 (14)
C12—C13—C14121.23 (17)
C16—N6—N7—C15179.18 (16)C10—C11—C15—N7176.74 (17)
C8—O1—C9—C103.4 (3)C12—C11—C15—N73.8 (3)
C8—O1—C9—C14176.32 (19)N7—N6—C16—O30.3 (3)
O1—C9—C10—C11179.83 (16)N7—N6—C16—C17179.83 (14)
C14—C9—C10—C110.5 (3)O3—C16—C17—C216.0 (3)
C9—C10—C11—C120.2 (3)N6—C16—C17—C21173.86 (17)
C9—C10—C11—C15179.66 (16)O3—C16—C17—C18173.15 (18)
C10—C11—C12—C130.9 (3)N6—C16—C17—C187.0 (3)
C15—C11—C12—C13179.58 (18)C21—C17—C18—C190.1 (3)
C11—C12—C13—C141.1 (3)C16—C17—C18—C19179.19 (17)
C12—C13—C14—O2179.03 (18)C20—N5—C19—C180.9 (3)
C12—C13—C14—C90.4 (3)C17—C18—C19—N50.8 (3)
O1—C9—C14—O20.5 (3)C19—N5—C20—C210.2 (3)
C10—C9—C14—O2179.79 (17)N5—C20—C21—C170.6 (4)
O1—C9—C14—C13179.92 (16)C18—C17—C21—C200.7 (3)
C10—C9—C14—C130.4 (3)C16—C17—C21—C20179.90 (19)
N6—N7—C15—C11179.50 (16)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O11.00 (3)2.24 (3)2.7081 (18)107.4 (18)
O2—H2···N5i1.00 (3)1.79 (3)2.699 (2)150 (2)
O4—H4A···O2ii0.73 (4)2.28 (4)2.986 (2)163 (4)
O4—H4B···O30.92 (3)1.93 (3)2.832 (3)166 (3)
N6—H6···O4iii0.89 (2)2.10 (2)2.976 (2)169 (2)
C8—H8A···O3iv0.95 (2)2.51 (2)3.390 (3)154 (2)
C15—H15···O4iii1.00 (2)2.58 (2)3.436 (3)143.1 (14)
C18—H18···O4iii0.977 (18)2.316 (18)3.272 (3)165.9 (16)
C20—H20···O1v0.94 (2)2.56 (2)3.189 (2)124.5 (17)
Symmetry codes: (i) x3/2, y+3/2, z+1/2; (ii) x+1, y, z; (iii) x+3/2, y+1/2, z+3/2; (iv) x+1/2, y+1/2, z+3/2; (v) x+3/2, y+3/2, z1/2.
 

Acknowledgements

The authors thank the Universities Sophisticated Instrumental Centre, Karnatak University, Dharwad, for the CCD X-ray facilities and X-ray data collection.

References

First citationBekhit, A. A., Hassan, A. M. M., Abd El Razik, H. A., El-Miligy, M. M. M., El-Agroudy, E. J. & Bekhit, A. E. A. (2015). Eur. J. Med. Chem. 94, 30–44.  Google Scholar
First citationBhat, M. A., Iqbal, M., Al-Dhfyan, A. & Shakeel, F. (2015). J. Mol. Liq. 203, 111–119.  Google Scholar
First citationBruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationFarrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationKoçyiğit Kaymakçıoğlu, B. & Rollas, S. (2002). Farmaco, 57, 595–599.  Google Scholar
First citationMaccari, R., Ottanà, R. & Vigorita, M. G. (2005). Bioorg. Med. Chem. Lett. 15, 2509–2513.  Web of Science CrossRef PubMed CAS Google Scholar
First citationMallikarjuna, B. P., Sastry, B. S., Suresh Kumar, G. V., Rajendraprasad, Y., Chandrashekar, S. M. & Sathisha, K. (2009). Eur. J. Med. Chem. 44, 4739–4746.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSheldrick, G. M. (2007). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationVavříková, E., Polanc, S., Kočevar, M., Košmrlj, J., Horváti, K., Bősze, S., Stolaříková, J., Imramovský, A. & Vinšová, J. (2011). Eur. J. Med. Chem. 46, 5902–5909.  Google Scholar

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