Structures and antimicrobial activity of fluoro- and hydroxy-substituted thiocarboxyhydrazones

Article abstract of DOI:10.1134/S0022476615070276

A series of fluoro- and hydroxy-substituted thiocarboxyhydrazones, 2-(3-fluorobenzylidene)-Nmethylhydrazinecarbothioamide (1), 2-(2,3-difluorobenzylidene)-N-methylhydrazinecarbothioamide (2), and 2-(2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (3

Full text of DOI:10.1134/S0022476615070276

Journal of Structural Chemistry. Vol. 56, No. 7, pp. 1420-1425, 2015.
Original Russian Text © 2015 Z.-X. Liu.
STRUCTURES AND ANTIMICROBIAL ACTIVITY
OF FLUORO- AND HYDROXY-SUBSTITUTED
THIOCARBOXYHYDRAZONES
Z.-X. Liu
UDC 547.53:548.73
A series of fluoro- and hydroxy-substituted thiocarboxyhydrazones, 2-(3-fluorobenzylidene)-N-
methylhydrazinecarbothioamide (1), 2-(2,3-difluorobenzylidene)-N-methylhydrazinecarbothioamide (2),
and 2-(2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (3), are synthesized and characterized by
elemental analysis, IR and UV-vis spectra, and single crystal X-ray diffraction. Structures of the three
compounds are similar, but with a slight modification due to fluoro substituting groups. The crystal
structures of the compounds are stabilized by hydrogen bonds and π⋯π interactions. The antimicrobial
activity of the compounds shows that they are effective against some bacteria.
DOI: 10.1134/S0022476615070276
Keywords: synthesis, hiocarboxyhydrazones, antimicrobial activity, crystal structure, hydrogen bonding.
The widespread excessive use of antibacterial agents leads to the development of more resistant bacteria to
commonly used antibiotics. This has resulted in the intense search for new types of antibiotics. Hydrazones are a kind of
interesting biological active compounds. In recent years, a number of hydrazones have been reported to have various
antimicrobial activities [1-6]. Thiocarboxyhydrazones are a special kind of hydrazone compounds, with the C=O groups
replaced by C=S groups. The slight modification of the structures leads to more potent antimicrobial activities [7-10]. In
addition, such compounds have potential antitumor and cytotoxic properties [11-13]. Recent research indicated that halido-
substituted hydrazones have more potent activities than those without such substitute groups [14, 15]. In order to explore
more effective antimicrobial materials, in the present work, a serious of three thiocarboxyhydrazones, 2-(3-
fluorobenzylidene)-N-methylhydrazinecarbothioamide (1), 2-(2,3-difluorobenzylidene)-N-methylhydrazinecarbothioamide
(2), and 2-(2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (3), have been prepared, characterized, and studied on
their antimicrobial activities.
Experimental. General. All chemicals and solvents used during the synthesis were of analytical grade and used as
received. 3-Fluorobenzaldehyde, 2,3-difluorobenzaldehyde, 2-hydroxybenzaldehyde, and 4-methyl-3-thiosemicarbazide of
analytical grade were purchased from Aldrich. Elemental analyses (CHN) were performed using a Perkin-Elmer 240
elemental analyzer. Infrared spectrum was recorded on a Nicolate Magna IR 750 series II FT-IR spectrophotometer as KBr
pellets. UV-Vis spectra in the range from 200 nm to 600 nm were recorded on a Perkin-Elmer Lambda-25 spectrophotometer.
1
H NMR spectra were recorded on 300 MHz Brucker Advance.
Preparation of the compounds. The compounds were prepared according to the same method. Equimolar
quantities of 4-methyl-3-thiosemicarbazide were reacted with 3-fluorobenzaldhyde, 2,3-difluorobenzaldehyde, and
School of Chemistry and Chemical Engineering, Linyi University, Linyi Shandong, P. R. China;
zengxin_liu@163.com. The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 56, No. 7,
pp. 1476-1480, November-December, 2015. Original article submitted April 22, 2014; revised May 14, 2014.
1420
0022-4766/15/5607-1420 © 2015 by Pleiades Publishing, Ltd.

2-hydroxybenzaldehyde, respectively, in methanol for 3 h, and the reaction progress was monitored by TLC. Then, the
solvent was removed by distillation to give a colorless solid. The precipitate formed was filtered and washed with methanol
and recrystallized from methanol. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of the
methanol solution of the compounds.
2-(3-Fluorobenzylidene)-N-methylhydrazinecarbothioamide (1). Yield, 89%. Anal. Calc. for C H FN S: C,
9 10 3
–1
51.2; H, 4.8; N, 19.9%. Found: C, 51.0; H, 4.7; N, 20.1%. IR data (KBr, cm ): 3382m, 3160w, 2998w, 2949w, 1543s,
1480w, 1443m, 1263s, 1133w, 1096w, 1034m, 966w, 923w, 880w, 817w, 775w, 681w, 570m, 520w, 445w. UV-Vis in
–1
methanol [λ , nm (ε, L⋅mol ⋅cm )]: 317 (21325). H NMR (d -DMSO, ppm): 3.03 (s, 3H), 7.20 (d, 1H), 7.40-7.8.03 (m,
–1
1
6
max
3H), 8.64 (s, 1H), 11.60 (s, 1H).
2-(2,3-Difluorobenzylidene)-N-methylhydrazinecarbothioamide (2). Yield, 92%. Anal. Calc. for C H F N S: C,
9 9 2 3
–1
47.2; H, 4.0; N, 18.3%. Found: C, 17.1; H, 3.9; N, 18.5%. IR data (KBr, cm ): 3287m, 3126m, 2986w, 1656w, 1544s, 1523s,
–1 –1
1436m, 1239s, 1173w, 1090m, 1029m, 943w, 753m, 657m, 455w. UV-Vis in methanol [λ , nm (ε, L⋅mol ⋅cm )]: 316
max
1 6
(19980). H NMR (d -DMSO, ppm): 3.03 (s, 3H), 7.23 (d, 1H), 7.36 (m, 1H), 7.62 (d, 1H), 8.64 (s, 1H), 11.71 (s, 1H).
2-(2-Hydroxybenzylidene)-N-methylhydrazinecarbothioamide (3). Yield, 85%. Anal. Calc. for C H N OS: C,
9 11 3
–1
51.7; H, 5.3; N, 20.1%. Found: C, 51.9; H, 5.3; N, 19.9%. IR data (KBr, cm ): 3483w, 3305w, 3118m, 2978w, 1655w,
1541s, 1522s, 1437m, 1241s, 1158w, 1088m, 1033m, 945w, 752m, 645m, 457w. UV-Vis in methanol [λ , nm (ε,
max
–1
–1
1
6
L⋅mol ⋅cm )]: 332 (21723), 303 (16350). H NMR (d -DMSO, ppm): 3.02 (s, 3H), 7.47-7.60 (m, 3H), 7.88 (d, 2H), 8.62 (s,
1H), 11.37 (s, 1H).
X-ray data collection and structure refinement. Suitable single crystals of the compounds were selected and
mounted in air onto thin glass fibers. Accurate unit cell parameters were determined by a least-squares fit of 2θ values, and
intensity data sets were measured on a Bruker Smart 1000 CCD diffractometer with MoK radiation (λ = 0.71073 Å) at room
α
temperature. The intensities were corrected for Lorentz and polarization effects, but no corrections for extinction were made.
The structures of the compounds were solved by direct methods using the SHELXL 97 program [16]. The non-hydrogen
atoms were located in successive difference Fourier syntheses. The final refinement was performed by full matrix least-
2
squares methods with anisotropic thermal parameters for non-hydrogen atoms on F . The amino hydrogen atoms were
located from difference Fourier maps and refined isotropically, with N–H distances restrained to 0.90(1) Å. The remaining
hydrogen atoms were located at the calculated positions. Crystallographic data and experimental details for structure analyses
are summarized in Table 1.
Fungal assay. C. albicans (ATCC 10231) was grown on Sabouraud dextrose agar (SDA) plates at 37°C and
maintained at 4°C for short-term storage. Cultures were routinely sub-cultured every 4-6 weeks. Cultures were grown to the
8
–3
stationary phase (approximately 1×10 cells⋅cm ) overnight at 37°C in the minimal medium (2% w/v glucose, 0.5% w/v
yeast nitrogen base, 0.5% w/v ammonium sulphate), again at 37°C. The complex (200 mg) was dissolved in DMSO (1.0 ml)
3 –1
and diluted by water (9.0 ml) to give a stock solution with a concentration of 2.0×10 μg⋅ml . Doubling dilutions of the
solution were made to yield a series of test solutions. Minimum inhibitory concentration MIC values (minimum
100
concentration required to inhibit 100% of cell growth) were then determined using the broth microdilution method.
Bacterial screening. Bacteria were maintained on Nutrient Agar plates at 4°C and cultured in liquid broth when
required. Liquid broth was used for the antibacterial testing. Liquid broth (13 g) was dissolved in water (1000 ml) in a Duran
bottle, and then dispensed into 250 ml conical flasks, autoclaved, and allowed to cool. Solutions of the complex were
prepared by dissolving the complex (20 mg) in DMSO (0.5 ml). To the solution sterilized Millipore water (9.5 ml) was added
3 –1
to produce a stock solution of a concentration 2.0×10 μg⋅ml . The stock solution (0.5 ml) was added to sterile water (9 ml)
–1
to produce a drug solution with a concentration of 100 μg⋅ml , and with a concentration of DMSO of 0.5%. This solution
(100 μl) was added to a microtiter plate. 1:1 serial dilutions were made so as to produce a test concentration range of 50-
–1
0.1 μg⋅ml . Both E. coli and MRSA were grown in liquid broth at 37°C and 200 rpm to an OD of 1.0. The microtiter plate
600
was inoculated with 100 μl of bacterial cells (OD = 1.0). The plates were incubated at 37°C for 24 h and OD values were
600 600
read using an RMX plate reader to give MIC values (minimum concentration required to inhibit 50% of cell growth).
50
1421

TABLE 1. Crystallographic Data for the Compounds
Parameter
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions a, Å
b, Å
C H FN S
9 10 3
C H F N S
9 9 2 3
C H N OS
9 11 3
211.3
229.2
209.3
Triclinic
P-1
Monoclinic
Triclinic
P-1
P2 /c
1
4.5437(12)
10.6756(15)
11.2586(19)
107.588(2)
90.856(2)
101.029(2)
509.43(17)
2
8.7200(7)
8.0308(8)
14.8960(13)
90
6.0340(11)
8.5636(16)
10.4989(19)
75.826(2)
75.707(2)
82.160(2)
508.04(16)
2
c, Å
α, deg
92.373(2)
90
β, deg
γ, deg
3
Cell volume, Å
1042.25(16)
4
Number of formula units/cell Z
3
D
, g/cm
1.377
1.461
1.368
calc
F(000)
220
472
220
–1
Absorption coefficient, mm
Temperature, K
0.295
0.308
0.289
298(2)
298(2)
298(2)
Wavelength, Å
0.71073
0.71073
0.30×0.27×0.23
2.88-25.50
0.71073
0.33×0.33×0.27
2.46-25.50
Crystal size, mm
0.17×0.13×0.12
1.90-25.50
θ Range for data collection, deg
Index ranges (h, k, l)
–5, 5; –12, 11; –13, 13 –10, 9; –9, 9; –15, 18 –7, 7; –10, 10; –12, 12
25.50 (96.3) 25.50 (99.3) 25.50 (98.6)
0.9515 and 0.9654 0.9132 and 0.9325 0.9107 and 0.9261
3564 / 1832 (0.0308) 9513 / 1932 (0.0271) 4673 / 1869 (0.0255)
Completeness to θ, %
Max and min transmission
Totle number of measured / unique reflections
(R )
int
1605
1832 / 2 / 134
1.175
1708
1932 / 2 / 143
1.087
1636
1869 / 2 / 135
1.217
Number of observed reflections [I > 2σ(I)]
Data / restraints / parameters
2
Goodness-of-fit on F
R = 0.0686,
1
R = 0.0334,
1
R = 0.0601,
1
Final R indices [I > 2σ(I)]
wR = 0.2637
2
wR = 0.0867
2
wR = 0.1605
2
R indices (all data)
R = 0.0779,
1
R = 0.0391,
1
R = 0.0675,
1
wR = 0.2795
2
wR = 0.0923
2
wR = 0.1640
2
3
Largest diff. peak and hole, e/Å
0.444, –0.416
0.206, –0.189
0.350, –0.218
Results and discussion. Chemistry. 4-Methyl-3-thiosemicarbazide was treated with appropriate aldehydes to
produce the desired products (Scheme 1). The purity of all products was determined by TLC using several solvent systems of
1
different polarities. The synthesized compounds were characterized by elemental analysis, IR, UV-Vis, and H NMR spectra.
Scheme 1. Synthesis of the compounds. 1: X = H, Y = F;
2: X = Y = F; 3: X = OH, Y = H.
1
Spectral analysis. The H NMR spectra of the compounds show signals at about 11-12 ppm, which are related to
the protons of the NH groups. The signals of the protons on the CH=N double bonds appear at about 8.6 ppm, and the
aromatic protons occur in the range 7.2-8.1 ppm. The signals indicative of the protons of the CH groups are located at about
3
3.0 ppm.
1422

Fig. 1. UV-Vis spectra of the compounds.
The IR and UV-Vis spectra (Fig. 1) of the compounds are very similar. The medium and sharp bands at about
–1 –1
3300 cm are assigned to ν . The bands observed at slight over and below 3000 cm are assigned to the aromatic and
N–H
–1
aliphatic C–H vibrations. The in tense bands at about 1550 cm are due to the absorption of the C=N bonds [17]. The
–1
medium bands at about 830-860 cm are attributed to ν . The absorptions of the electronic spectra may be assigned to
C–S
n → π* transitions.
Crystal structure description. The molecular structures of compounds 1, 2, and 3 are shown in Figs. 2a, b, and c,
respectively. In each of the compounds, the sulfur atom and the azomethine nitrogen atom are in trans position with respect
to the N2–C8 bond. The molecules of the compounds are not coplanar, as evidenced by the dihedral angles (2.2(5)° for 1,
4.3(4)° for 2, and 10.5(5)° for 3) between the N1N2C8S1 thiourea groups and the benzene rings. The bond distances in the
thiosemicarbazone side chains agree well with the values observed for similar compounds where the C=S groups are pre-sent
in the thionic form [17]. There is no obvious charge delocalization in the molecules, as evidenced by the typical C–N single
bonds between C8 and N3 atoms.
Fig. 2. ORTEP view of the molecular structure, showing the atom numbering scheme for non-hydrogen atoms.
Selected bond lengths (Å) and bond angles (deg) for 1: C7–N1 1.268(6), N1–N2 1.363(5), C8–N2 1.347(6),
C8–S1 1.683(4), C8–N3 1.322(6); C7–N1–N2 116.5(4), N1–N2–C8 119.5(4), N2–C8–S1 120.0(3), N2–C8–N3
116.2(4); for 2: C7–N1 1.273(2), N1–N2 1.373(2), N2–C8 1.351(2), C8–S1 1.690(2), C8–N3 1.315(2); C7–N1–
N2 115.9(1), N1–N2–C8 119.8(1), N2–C8–S1 119.1(1), N2–C8–N3 117.2(1); for 3: C7–N1 1.285(4), N1–N2
1.378(4), N2–C8 1.348(4), C8–S1 1.688(3), C8–N3 1.325(4); C7–N1–N2 115.2(3), N1–N2–C8 121.9(3),
N2–C8–S1 118.6(2), N2–C8–N3 117.5(3).
1423

TABLE 2. Hydrogen Bond Geometry (Å, deg) for the Compounds
D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A
1
i
N2–H2⋯S1
0.90(1)
0.90(1)
2.553(15)
2.35(4)
3.444(4)
3.110(5)
172(6)
142(6)
ii
N3–H3⋯F1
2
iii
N3–H3⋯S1
0.90(1)
2.877(19)
3.565(2)
135(2)
3
iv
N3–H3⋯S1
0.90(1)
0.82
2.80(3)
1.96
3.474(3)
2.685(4)
134(4)
146
O1–H1⋯N1
i
Symmetry codes: 3–x, 1–y, 1–z; 1–x, 1–y, –z; 2–x, –1/2+y, 1/2–z; –1+x, y, z.
ii
iii
iv
–1
TABLE 3. Antimicrobial Assay Results (μmol⋅l )
Compound
C. albicans MIC
MRSA MIC
E. coli MIC
50
100
50
1
6.25
3.12
25
25
25
25
12.5
>50
>50
2
3
>50
>50
Ketoconazole
4.50
In the crystal structure of 1, the molecules are linked through intermolecular N–H⋯S and N–H⋯F hydrogen bonds
(Table 2) to form 1D chains running along the ac vector direction. In the crystal structure of 2, the molecules are linked
through intermolecular N–H⋯S hydrogen bonds (Table 2) to form 2D layers parallel to the bc plane. In addition, in this
compound, π⋯π interactions exist with a centroid to centroid distance of 3.951(2) Å. In the crystal structure of 3, the
molecules are linked through intermolecular N–H⋯S and O–H⋯N hydrogen bonds (Table 2) to form 1D chains running
along the a axis direction.
Biological assay results. The biological assay results are summarized in Table 3. Compounds 1 and 2 have strong
activities against C. albicans and E. coli, and medium activities against MRSA. Compound 3 has a weak activity against
C. albicans, and no activity against MRSA and E. coli. Thus, it is easy to see that the fluoro groups in the compounds may
facilitate the antimicrobial activities. Compound 2 has the strongest activity against C. albicans as compared to the other two
compounds, and is stronger than Ketoconazole.
In summary, three new similar fluoro- and hydroxy-substituted thiocarboxyhydrazones have been prepared and
characterized. Single crystal structures of the compounds are presented. The antimicrobial activity of the compounds shows
that they are effective against some bacteria.
Crystallographic data for structural analyses have been deposited with the Cambridge Crystallographic Data Center,
CCDC Nos. 981998 (1), 981999 (2), and 982000 (3). Copies of this information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk).
The author acknowledges the Linyi University for supporting this work.
REFERENCES
1. M. Alagesan, N. S. P. Bhuvanesh, and N. Dharmaraj, Dalton Trans., 42, No. 19, 7210-7223 (2013).
2. M. D. Altintop, A. Ozdemir, G. Turan-Zitouni, S. Ilgin, O. Atli, G. Iscan, and Z. A. Kaplancikli, Eur. J. Med. Chem.,
58, 299-307 (2012).
1424

3. P. Yang, Y. Wang, Z.-C. Duan, Y. Shao, G.-H. Nie, X.-J. Song, and D.-T. Tian, Chin. J. Struct. Chem., 32, No. 7,
1023-1030 (2013).
4. Z. A. Kaplancikli, M. D. Altintop, A. Ozdemir, G. Turan-Zitouni, S. I. Khan, and N. Tabanca, Lett. Drug Des.
Discovery, 9, No. 3, 310-315 (2012).
5. D. Blanot, J. Lee, and S. E. Girardin, Chem. Biol. Drug Des., 79, No. 1, 2-8 (2012).
6. T. Horiuchi, Y. Takeda, N. Haginoya, M. Miyazaki, M. Nagata, M. Kitagawa, K. Akahane, and K. Uoto, Chem. Pharm.
Bull., 59, No. 8, 991-1002 (2011).
7. G. D. K. Kumar, G. E. Chavarria, A. K. Charlton-Sevcik, W. M. Arispe, M. T. MacDonough, T. E. Strecker,
S. E. Chen, B. G. Siim, D. J. Chaplin, and M. L. Trawick, Bioorg. Med. Chem. Lett., 20, No. 4, 1415-1419 (2010).
8. Y. Li, Z.-Y. Yang, and J.-C. Wu, Eur. J. Med. Chem., 45, No. 12, 5692-5701 (2010).
9. A. Kumar, S. Singh, H. Bordbar, T. Cartledge, and S. Ahmed, Lett. Drug Des. Discovery., 8, No. 3, 241-245 (2011).
10. D. S. Raja, N. S. P. Bhuvanesh, and K. Natarajan, Eur. J. Med. Chem., 46, No. 9, 4584-4594 (2011).
11. K. Hu, Z.-H. Yang, S.-S. Pan, H.-J. Xu, and J. Ren, Eur. J. Med. Chem., 45, No. 8, 3453-3458 (2010).
12. A. I. Matesanz, and P. Souza, Mini-Rev. Med. Chem., 9, No. 12, 1389-1396 (2009).
13. I. Dilovic, M. Rubcic, V. Vrdoljak, S. K. Pavelic, M. Kralj, I. Piantanida, and M. Cindric, Bioorg. Med. Chem., 16,
No. 9, 5189-5198 (2008).
14. C. Congiu and V. Onnis, Bioorg. Med. Chem., 21, No. 21, 6592-6599 (2013).
15. M. Zhang, D.-M. Xian, H.-H. Li, J.-C. Zhang, and Z.-L. You, Aust. J. Chem., 65, No. 4, 343-350 (2012).
16. G. M. Sheldrick, Acta Crystallogr., A64, No. 1, 112-122 (2008).
17. M. B. Ferrari, S. Capacchi, G. Reffo, G. Pelosi, P. Tarasconi, R. Albertini, S. Pinelli, and P. Lunghi, J. Inorg. Biochem.,
81, No. 1, 89-97 (2000).
1425