Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807038901/at2365sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807038901/at2365Isup2.hkl |
CCDC reference: 660242
A mixture of 2-chloro-5-nitroaniline (0.345 g, 0.002 mol) and 4-(diethylamino)-2-hydroxybenzaldehyde (0.386 g, 0.002 mol) in 15 ml of absolute ethanol containing 2 drops of 4 M sulfuric acid was refluxed for about 3 h. On cooling, the solid separated, was filtered and recrystallized from acetone (m.p.: 441–445 K). Analysis found: C 58.59, H 5.16, N 12.01%; C17H18ClN3O3 requires: C 58.71, H 5.22, N 12.08%.
All H atoms were refined using a riding model with O—H = 0.83 Å and C—H = 0.94–0.97 Å, and with Uiso(H) = 1.19–1.50Ueq(C, O).
Schiff bases are used as substrates in the preparation of number of industrial and biologically active compounds via ring closure, cycloaddition and replacement reactions. Some Schiff base derivatives were reported to possess antimicrobial, anti-inflammatory and central nervous system activities. Moreover, Schiff bases are also known to have biological activities such as antimicrobial, antifungal, antitumor, and as herbicides. A new Schiff base, (I), C17H18ClN3O3 has been synthesized and herein its crystal structure is reported.
The phenol and 2-chloro-5-nitrophenyl groups of the title molecule (I) (Fig. 1) are coplanar with each other [dihedral angle = 5.1 (4)°] and also with the imine linkage, forming torsion angles C7—N2—C6—C5 and N2—C7—C8—C9 of 5.0 (2)° and 0.2 (2)(18)°, respectively.
Intermolecular C—H···O hydrogen bonding between a chlorophenyl hydrogen (C2–H2A) and O2 from the nitro group link the molecules into a chain along the c axis of the unit cell and stabilize crystal packing (Fig. 2). Intramolecular O—H···N hydrogen bonding also occurs between the hydroxyl hydrogen (H3) and the imine nitrogen (N2) within the asymmetric unit (Fig. 1, Tablo 1).
For related structures, see: Odabaşoğlu et al. (2007); Yathirajan et al. (2007). For related literature, see: Hodnett & Dunn (1970); Misra et al. (1981); Agarwal et al. (1983); Varma et al. (1986); Singh & Dash (1988).
Data collection: CrysAlis PRO (Oxford Diffraction, 2007); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
C17H18ClN3O3 | F(000) = 728 |
Mr = 347.79 | Dx = 1.404 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 9461 reflections |
a = 7.4956 (3) Å | θ = 4.9–32.3° |
b = 23.3915 (7) Å | µ = 0.25 mm−1 |
c = 10.0552 (5) Å | T = 203 K |
β = 111.008 (5)° | Plate, yellow |
V = 1645.82 (12) Å3 | 0.49 × 0.45 × 0.25 mm |
Z = 4 |
Oxford Diffraction Gemini R diffractometer | 5364 independent reflections |
Radiation source: fine-focus sealed tube | 3914 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.054 |
Detector resolution: 10.5081 pixels mm-1 | θmax = 32.3°, θmin = 4.9° |
φ and ω scans | h = −11→11 |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007) | k = −34→33 |
Tmin = 0.940, Tmax = 1.000 | l = −15→14 |
17009 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.056 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.162 | H-atom parameters constrained |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0722P)2 + 0.8483P] where P = (Fo2 + 2Fc2)/3 |
5364 reflections | (Δ/σ)max = 0.001 |
220 parameters | Δρmax = 0.41 e Å−3 |
0 restraints | Δρmin = −0.31 e Å−3 |
C17H18ClN3O3 | V = 1645.82 (12) Å3 |
Mr = 347.79 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.4956 (3) Å | µ = 0.25 mm−1 |
b = 23.3915 (7) Å | T = 203 K |
c = 10.0552 (5) Å | 0.49 × 0.45 × 0.25 mm |
β = 111.008 (5)° |
Oxford Diffraction Gemini R diffractometer | 5364 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007) | 3914 reflections with I > 2σ(I) |
Tmin = 0.940, Tmax = 1.000 | Rint = 0.054 |
17009 measured reflections |
R[F2 > 2σ(F2)] = 0.056 | 0 restraints |
wR(F2) = 0.162 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.41 e Å−3 |
5364 reflections | Δρmin = −0.31 e Å−3 |
220 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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. |
x | y | z | Uiso*/Ueq | ||
Cl | 1.34352 (6) | −0.00398 (2) | 0.80924 (6) | 0.03748 (14) | |
O1 | 0.6102 (2) | 0.14212 (7) | 0.38511 (19) | 0.0513 (4) | |
O2 | 0.45852 (19) | 0.08230 (6) | 0.46828 (16) | 0.0390 (3) | |
O3 | 1.19131 (17) | −0.09886 (5) | 1.04607 (14) | 0.0301 (3) | |
H3 | 1.1681 | −0.0748 | 0.9815 | 0.036* | |
N1 | 0.6067 (2) | 0.10152 (6) | 0.46062 (16) | 0.0273 (3) | |
N2 | 0.97949 (19) | −0.03280 (5) | 0.83664 (15) | 0.0230 (3) | |
N3 | 0.8752 (2) | −0.22171 (6) | 1.26954 (17) | 0.0307 (3) | |
C1 | 1.1265 (2) | 0.02557 (7) | 0.70757 (18) | 0.0230 (3) | |
C2 | 1.1238 (2) | 0.06546 (7) | 0.60541 (19) | 0.0272 (3) | |
H2A | 1.2378 | 0.0753 | 0.5920 | 0.033* | |
C3 | 0.9525 (2) | 0.09101 (7) | 0.52241 (18) | 0.0265 (3) | |
H3A | 0.9478 | 0.1184 | 0.4528 | 0.032* | |
C4 | 0.7889 (2) | 0.07449 (6) | 0.54647 (17) | 0.0218 (3) | |
C5 | 0.7879 (2) | 0.03435 (6) | 0.64667 (17) | 0.0213 (3) | |
H5A | 0.6728 | 0.0245 | 0.6583 | 0.026* | |
C6 | 0.9605 (2) | 0.00830 (6) | 0.73132 (17) | 0.0204 (3) | |
C7 | 0.8315 (2) | −0.05334 (6) | 0.85754 (17) | 0.0231 (3) | |
H7A | 0.7096 | −0.0400 | 0.8009 | 0.028* | |
C8 | 0.8467 (2) | −0.09556 (6) | 0.96367 (17) | 0.0218 (3) | |
C9 | 1.0257 (2) | −0.11792 (6) | 1.05438 (17) | 0.0217 (3) | |
C10 | 1.0346 (2) | −0.15990 (6) | 1.15374 (18) | 0.0243 (3) | |
H10A | 1.1540 | −0.1748 | 1.2107 | 0.029* | |
C11 | 0.8672 (2) | −0.18063 (6) | 1.17092 (17) | 0.0237 (3) | |
C12 | 0.6883 (2) | −0.15741 (7) | 1.08184 (19) | 0.0268 (3) | |
H12A | 0.5746 | −0.1699 | 1.0919 | 0.032* | |
C13 | 0.6820 (2) | −0.11718 (7) | 0.98224 (18) | 0.0265 (3) | |
H13A | 0.5621 | −0.1032 | 0.9232 | 0.032* | |
C14 | 1.0565 (3) | −0.24648 (8) | 1.36135 (19) | 0.0336 (4) | |
H14A | 1.0431 | −0.2600 | 1.4496 | 0.040* | |
H14B | 1.1550 | −0.2167 | 1.3867 | 0.040* | |
C15 | 1.1208 (4) | −0.29595 (9) | 1.2914 (3) | 0.0470 (5) | |
H15A | 1.2391 | −0.3116 | 1.3576 | 0.070* | |
H15B | 1.1412 | −0.2824 | 1.2068 | 0.070* | |
H15C | 1.0232 | −0.3254 | 1.2650 | 0.070* | |
C16 | 0.7024 (3) | −0.24621 (8) | 1.2819 (2) | 0.0365 (4) | |
H16A | 0.7309 | −0.2848 | 1.3218 | 0.044* | |
H16B | 0.6040 | −0.2495 | 1.1866 | 0.044* | |
C17 | 0.6245 (4) | −0.21056 (10) | 1.3756 (3) | 0.0480 (5) | |
H17A | 0.5152 | −0.2298 | 1.3854 | 0.072* | |
H17B | 0.5855 | −0.1734 | 1.3322 | 0.072* | |
H17C | 0.7230 | −0.2058 | 1.4689 | 0.072* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl | 0.0244 (2) | 0.0427 (3) | 0.0451 (3) | 0.00914 (16) | 0.01210 (19) | 0.00777 (19) |
O1 | 0.0425 (8) | 0.0488 (9) | 0.0589 (10) | 0.0079 (7) | 0.0136 (7) | 0.0329 (8) |
O2 | 0.0258 (6) | 0.0482 (8) | 0.0409 (8) | 0.0009 (5) | 0.0093 (6) | 0.0095 (6) |
O3 | 0.0257 (6) | 0.0334 (6) | 0.0320 (7) | 0.0020 (5) | 0.0114 (5) | 0.0096 (5) |
N1 | 0.0294 (7) | 0.0263 (6) | 0.0250 (7) | 0.0028 (5) | 0.0082 (6) | 0.0048 (5) |
N2 | 0.0259 (6) | 0.0210 (6) | 0.0221 (6) | 0.0019 (5) | 0.0089 (5) | 0.0038 (5) |
N3 | 0.0401 (8) | 0.0247 (6) | 0.0304 (8) | 0.0011 (6) | 0.0164 (7) | 0.0075 (6) |
C1 | 0.0206 (7) | 0.0225 (7) | 0.0264 (8) | 0.0021 (5) | 0.0090 (6) | −0.0006 (6) |
C2 | 0.0261 (7) | 0.0285 (7) | 0.0320 (9) | −0.0031 (6) | 0.0166 (7) | 0.0013 (6) |
C3 | 0.0305 (8) | 0.0259 (7) | 0.0262 (8) | −0.0017 (6) | 0.0139 (7) | 0.0048 (6) |
C4 | 0.0244 (7) | 0.0199 (6) | 0.0210 (7) | 0.0002 (5) | 0.0081 (6) | 0.0008 (5) |
C5 | 0.0206 (6) | 0.0206 (6) | 0.0234 (7) | −0.0007 (5) | 0.0086 (6) | 0.0014 (5) |
C6 | 0.0237 (7) | 0.0177 (6) | 0.0208 (7) | 0.0001 (5) | 0.0090 (6) | 0.0006 (5) |
C7 | 0.0249 (7) | 0.0217 (7) | 0.0228 (7) | 0.0023 (5) | 0.0087 (6) | 0.0031 (6) |
C8 | 0.0261 (7) | 0.0186 (6) | 0.0205 (7) | 0.0007 (5) | 0.0081 (6) | 0.0021 (5) |
C9 | 0.0251 (7) | 0.0205 (6) | 0.0210 (7) | 0.0007 (5) | 0.0099 (6) | −0.0001 (5) |
C10 | 0.0289 (7) | 0.0201 (6) | 0.0239 (7) | 0.0039 (5) | 0.0096 (6) | 0.0022 (6) |
C11 | 0.0331 (8) | 0.0166 (6) | 0.0229 (7) | −0.0003 (5) | 0.0119 (6) | 0.0002 (5) |
C12 | 0.0280 (7) | 0.0259 (7) | 0.0275 (8) | −0.0033 (6) | 0.0112 (6) | 0.0025 (6) |
C13 | 0.0255 (7) | 0.0264 (7) | 0.0264 (8) | 0.0004 (6) | 0.0079 (6) | 0.0031 (6) |
C14 | 0.0484 (11) | 0.0286 (8) | 0.0227 (8) | 0.0032 (7) | 0.0115 (8) | 0.0083 (6) |
C15 | 0.0610 (14) | 0.0342 (10) | 0.0476 (13) | 0.0148 (9) | 0.0217 (11) | 0.0096 (9) |
C16 | 0.0481 (11) | 0.0279 (8) | 0.0370 (10) | −0.0063 (7) | 0.0197 (9) | 0.0065 (7) |
C17 | 0.0527 (13) | 0.0499 (12) | 0.0525 (13) | −0.0034 (10) | 0.0324 (11) | 0.0039 (10) |
Cl—C1 | 1.7251 (16) | C8—C13 | 1.407 (2) |
O1—N1 | 1.222 (2) | C8—C9 | 1.424 (2) |
O2—N1 | 1.2258 (19) | C9—C10 | 1.385 (2) |
O3—C9 | 1.3495 (19) | C10—C11 | 1.412 (2) |
O3—H3 | 0.8300 | C10—H10A | 0.9400 |
N1—C4 | 1.472 (2) | C11—C12 | 1.426 (2) |
N2—C7 | 1.293 (2) | C12—C13 | 1.363 (2) |
N2—C6 | 1.3993 (19) | C12—H12A | 0.9400 |
N3—C11 | 1.367 (2) | C13—H13A | 0.9400 |
N3—C14 | 1.461 (2) | C14—C15 | 1.520 (3) |
N3—C16 | 1.462 (2) | C14—H14A | 0.9800 |
C1—C2 | 1.382 (2) | C14—H14B | 0.9800 |
C1—C6 | 1.408 (2) | C15—H15A | 0.9700 |
C2—C3 | 1.391 (2) | C15—H15B | 0.9700 |
C2—H2A | 0.9400 | C15—H15C | 0.9700 |
C3—C4 | 1.387 (2) | C16—C17 | 1.523 (3) |
C3—H3A | 0.9400 | C16—H16A | 0.9800 |
C4—C5 | 1.379 (2) | C16—H16B | 0.9800 |
C5—C6 | 1.407 (2) | C17—H17A | 0.9700 |
C5—H5A | 0.9400 | C17—H17B | 0.9700 |
C7—C8 | 1.428 (2) | C17—H17C | 0.9700 |
C7—H7A | 0.9400 | ||
C9—O3—H3 | 109.5 | C9—C10—H10A | 119.5 |
O1—N1—O2 | 123.10 (15) | C11—C10—H10A | 119.5 |
O1—N1—C4 | 118.42 (14) | N3—C11—C10 | 121.36 (15) |
O2—N1—C4 | 118.48 (14) | N3—C11—C12 | 120.67 (15) |
C7—N2—C6 | 121.17 (14) | C10—C11—C12 | 117.97 (14) |
C11—N3—C14 | 121.75 (15) | C13—C12—C11 | 120.09 (15) |
C11—N3—C16 | 121.84 (15) | C13—C12—H12A | 120.0 |
C14—N3—C16 | 116.27 (14) | C11—C12—H12A | 120.0 |
C2—C1—C6 | 122.75 (14) | C12—C13—C8 | 123.02 (15) |
C2—C1—Cl | 118.06 (12) | C12—C13—H13A | 118.5 |
C6—C1—Cl | 119.18 (12) | C8—C13—H13A | 118.5 |
C1—C2—C3 | 120.04 (14) | N3—C14—C15 | 112.76 (16) |
C1—C2—H2A | 120.0 | N3—C14—H14A | 109.0 |
C3—C2—H2A | 120.0 | C15—C14—H14A | 109.0 |
C4—C3—C2 | 117.34 (14) | N3—C14—H14B | 109.0 |
C4—C3—H3A | 121.3 | C15—C14—H14B | 109.0 |
C2—C3—H3A | 121.3 | H14A—C14—H14B | 107.8 |
C5—C4—C3 | 123.63 (14) | C14—C15—H15A | 109.5 |
C5—C4—N1 | 118.29 (13) | C14—C15—H15B | 109.5 |
C3—C4—N1 | 118.09 (14) | H15A—C15—H15B | 109.5 |
C4—C5—C6 | 119.49 (13) | C14—C15—H15C | 109.5 |
C4—C5—H5A | 120.3 | H15A—C15—H15C | 109.5 |
C6—C5—H5A | 120.3 | H15B—C15—H15C | 109.5 |
N2—C6—C5 | 125.29 (13) | N3—C16—C17 | 112.71 (16) |
N2—C6—C1 | 117.97 (14) | N3—C16—H16A | 109.1 |
C5—C6—C1 | 116.74 (14) | C17—C16—H16A | 109.1 |
N2—C7—C8 | 122.36 (14) | N3—C16—H16B | 109.1 |
N2—C7—H7A | 118.8 | C17—C16—H16B | 109.1 |
C8—C7—H7A | 118.8 | H16A—C16—H16B | 107.8 |
C13—C8—C9 | 116.94 (14) | C16—C17—H17A | 109.5 |
C13—C8—C7 | 120.60 (14) | C16—C17—H17B | 109.5 |
C9—C8—C7 | 122.46 (14) | H17A—C17—H17B | 109.5 |
O3—C9—C10 | 118.11 (14) | C16—C17—H17C | 109.5 |
O3—C9—C8 | 121.03 (14) | H17A—C17—H17C | 109.5 |
C10—C9—C8 | 120.86 (14) | H17B—C17—H17C | 109.5 |
C9—C10—C11 | 121.09 (15) | ||
C6—C1—C2—C3 | 1.0 (3) | C13—C8—C9—O3 | −178.67 (15) |
Cl—C1—C2—C3 | −179.07 (13) | C7—C8—C9—O3 | 1.6 (2) |
C1—C2—C3—C4 | −0.4 (2) | C13—C8—C9—C10 | 1.3 (2) |
C2—C3—C4—C5 | −0.3 (2) | C7—C8—C9—C10 | −178.35 (15) |
C2—C3—C4—N1 | 179.38 (15) | O3—C9—C10—C11 | 178.20 (14) |
O1—N1—C4—C5 | 170.73 (17) | C8—C9—C10—C11 | −1.8 (2) |
O2—N1—C4—C5 | −9.2 (2) | C14—N3—C11—C10 | −0.4 (2) |
O1—N1—C4—C3 | −9.0 (2) | C16—N3—C11—C10 | −175.88 (16) |
O2—N1—C4—C3 | 171.05 (16) | C14—N3—C11—C12 | 179.56 (15) |
C3—C4—C5—C6 | 0.4 (2) | C16—N3—C11—C12 | 4.1 (2) |
N1—C4—C5—C6 | −179.30 (13) | C9—C10—C11—N3 | −179.47 (15) |
C7—N2—C6—C5 | 5.0 (2) | C9—C10—C11—C12 | 0.6 (2) |
C7—N2—C6—C1 | −175.37 (15) | N3—C11—C12—C13 | −178.87 (16) |
C4—C5—C6—N2 | 179.86 (14) | C10—C11—C12—C13 | 1.1 (2) |
C4—C5—C6—C1 | 0.2 (2) | C11—C12—C13—C8 | −1.6 (3) |
C2—C1—C6—N2 | 179.40 (15) | C9—C8—C13—C12 | 0.4 (2) |
Cl—C1—C6—N2 | −0.5 (2) | C7—C8—C13—C12 | −179.95 (16) |
C2—C1—C6—C5 | −0.9 (2) | C11—N3—C14—C15 | −85.2 (2) |
Cl—C1—C6—C5 | 179.17 (11) | C16—N3—C14—C15 | 90.5 (2) |
C6—N2—C7—C8 | 179.62 (14) | C11—N3—C16—C17 | −85.1 (2) |
N2—C7—C8—C13 | −179.46 (15) | C14—N3—C16—C17 | 99.1 (2) |
N2—C7—C8—C9 | 0.2 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2A···O2i | 0.94 | 2.41 | 3.291 (2) | 157 |
O3—H3···N2 | 0.83 | 1.90 | 2.6356 (18) | 147 |
Symmetry code: (i) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C17H18ClN3O3 |
Mr | 347.79 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 203 |
a, b, c (Å) | 7.4956 (3), 23.3915 (7), 10.0552 (5) |
β (°) | 111.008 (5) |
V (Å3) | 1645.82 (12) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.25 |
Crystal size (mm) | 0.49 × 0.45 × 0.25 |
Data collection | |
Diffractometer | Oxford Diffraction Gemini R |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2007) |
Tmin, Tmax | 0.940, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17009, 5364, 3914 |
Rint | 0.054 |
(sin θ/λ)max (Å−1) | 0.752 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.056, 0.162, 1.10 |
No. of reflections | 5364 |
No. of parameters | 220 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.41, −0.31 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2007), CrysAlis PRO, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2A···O2i | 0.94 | 2.41 | 3.291 (2) | 156.8 |
O3—H3···N2 | 0.83 | 1.90 | 2.6356 (18) | 147.2 |
Symmetry code: (i) x+1, y, z. |
Schiff bases are used as substrates in the preparation of number of industrial and biologically active compounds via ring closure, cycloaddition and replacement reactions. Some Schiff base derivatives were reported to possess antimicrobial, anti-inflammatory and central nervous system activities. Moreover, Schiff bases are also known to have biological activities such as antimicrobial, antifungal, antitumor, and as herbicides. A new Schiff base, (I), C17H18ClN3O3 has been synthesized and herein its crystal structure is reported.
The phenol and 2-chloro-5-nitrophenyl groups of the title molecule (I) (Fig. 1) are coplanar with each other [dihedral angle = 5.1 (4)°] and also with the imine linkage, forming torsion angles C7—N2—C6—C5 and N2—C7—C8—C9 of 5.0 (2)° and 0.2 (2)(18)°, respectively.
Intermolecular C—H···O hydrogen bonding between a chlorophenyl hydrogen (C2–H2A) and O2 from the nitro group link the molecules into a chain along the c axis of the unit cell and stabilize crystal packing (Fig. 2). Intramolecular O—H···N hydrogen bonding also occurs between the hydroxyl hydrogen (H3) and the imine nitrogen (N2) within the asymmetric unit (Fig. 1, Tablo 1).