research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Crystal structure of 1-amino-2-oxo-2,5,6,7,8,9-hexa­hydro-1H-cyclo­hepta­[b]pyridine-3-carbo­nitrile

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aChemistry Department, Faculty of Science, Helwan University, Cairo, Egypt, and bInstitut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Postfach 3329, D-38023 Braunschweig, Germany
*Correspondence e-mail: p.jones@tu-bs.de

Edited by H. Stoeckli-Evans, University of Neuchâtel, Switzerland (Received 25 July 2016; accepted 27 July 2016; online 2 August 2016)

In the title compound, C11H13N3O, the seven-membered ring adopts a conformation such that the three atoms not involved in the aromatic plane lie on the same side of that plane. One hydrazinic H atom forms an intra­molecular hydrogen bond to the O atom; the other forms a classical inter­molecular hydrogen bond N—H⋯O, which combines with a `weak' Har⋯O inter­action to build up double layers of mol­ecules parallel to the bc plane.

1. Chemical context

We have recently described various novel approaches for the synthesis of a new class of N-substituted amino derivatives of pyridines and pyrimidines (Elgemeie, Salah et al., 2015[Elgemeie, G. H., Salah, A. M., Mohamed, R. A. & Jones, P. G. (2015). Acta Cryst. E71, 1319-1321.]; Elgemeie et al., 2016[Elgemeie, G. H., Abu-Zaied, M. & Azzam, R. (2016). Nucleosides Nucleotides Nucleic Acids, 35, 211-222.]). These compounds are important as pyrimidine ring systems that are not nucleoside analogs, and are inter­esting as anti­metabolic agents (Elgemeie & Hamed, 2014[Elgemeie, G. H. & Hamed, M. (2014). Curr. Microw. Chem. 1, 155-176.]; Elgemeie & Abd Elaziz, 2015[Elgemeie, G. H. & Abd Elaziz, H. (2015). Curr. Microw. Chem. 2, 90-128.]). They have a greater selectivity for a broader range of human tumors, hence our inter­est in this class of compounds (Elgemeie, Abou-Zeid et al., 2015[Elgemeie, G. H., Abou-Zeid, M., Alsaid, S., Hebishy, A. & Essa, H. (2015). Nucleosides Nucleotides Nucleic Acids, 34, 659-673.]; Elgemeie, Mohamed et al., 2015[Elgemeie, G. H., Mohamed, R. A., Hussein, H. A. & Jones, P. G. (2015). Acta Cryst. E71, 1322-1324.]).

[Scheme 1]

We report here a novel one-step synthesis of a cyclo­heptane-ring-fused N-amino-2-pyridone derivative by reaction of the sodium salt of 2-(hy­droxy­methyl­ene)-1-cyclo­hepta­none (1) with a cyano­acetohydrazide (2). Thus, (1) reacted with (2) in piperidine acetate to give a product of mol­ecular formula C11H13N3O (M+ = 203), for which two isomeric structures, (3) and (4), seemed possible, corres­ponding to two possible modes of cyclization. Spectroscopic data cannot differentiate between these structures, and therefore the crystal structure was determined, confirming the exclusive presence of tautomer (3) in the solid state. The formation of (3) from the reaction of (1) and (2) is assumed to proceed via initial addition of the active methyl­ene carbon atom of (2) to the formyl group of (1) to give the favoured, kinetically controlled product (3). The 1H NMR spectra of the product revealed the presence of an N—NH2 group at δ = 6.4 p.p.m. and a pyridine H-4 at 7.8 p.p.m. in solution.

2. Structural commentary

The structure of the title compound is shown in Fig. 1[link] and confirms the presence of tautomer (3) in the solid state. Mol­ecular dimensions [e.g. the hydrazinic N1—N2 bond length of 1.4201 (15) Å] may be regarded as normal; an extensive structural investigation of alkyl-substituted 3-cyano-2-pyridones (with an unsubstituted NH function in the ring) was published by Fischer et al. (2004[Fischer, C. B., Polborn, K., Steininger, H. & Zipse, H. (2004). Z. Naturforsch. Teil B, 59, 1121-1131.]). The seven-membered ring adopts a conformation such that all three atoms C6, C7 and C8 lie to the same side of the plane formed by the pyridone ring together with C5 and C9; the respective deviations from this plane are 1.480 (2), 1.616 (3) and 1.470 (2) Å.

[Figure 1]
Figure 1
The mol­ecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The intra­molecular N—H⋯O hydrogen bond is shown as a dashed line (see Table 1[link])

3. Supra­molecular features

The classical hydrogen-bond donor N1—H01 is only involved in intra­molecular hydrogen bonding (Fig. 1[link] and Table 1[link]). The second such donor N1—H02 forms a classical hydrogen bond to the acceptor O1 of a neighbouring mol­ecule related by the 21 screw axis. Additionally, the `weak' but quite short hydrogen bond C4—H4⋯O1 links mol­ecules related by the c glide plane. The overall effect is to build up double layers of mol­ecules (Fig. 2[link] and Table 1[link]) parallel to the bc plane, in which the top and bottom mol­ecules of the layer are related by inversion.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N2—H01⋯O1 0.90 (2) 2.05 (2) 2.6255 (15) 120.4 (16)
N2—H02⋯O1i 0.91 (2) 2.16 (2) 3.0225 (15) 158.2 (17)
C4—H4⋯O1ii 0.95 2.45 3.2105 (16) 137
C9—H9A⋯O1i 0.99 2.63 3.4903 (16) 146
Symmetry codes: (i) [-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) [x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}].
[Figure 2]
Figure 2
Crystal packing of the title compound, viewed approximately normal to the bc plane. Dashed lines indicate the hydrogen bonds (see Table 1[link]), and for clarity H atoms not involved in hydrogen bonding have been omitted.

4. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.37, last update May 2016; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) revealed four other examples of the cyclo­hepta­[b]pyridin-2-one ring system: refcodes AHEQAF (Elgemeie et al., 2002[Elgemeie, G. H., Mahmoud, M. A. & Jones, P. G. (2002). Acta Cryst. E58, o1293-o1295.]), ATUYAP and IBATUB (Albov et al., 2004a[Albov, D. V., Mazina, O. S., Rybakov, V. B., Babaev, E. V., Chemyshev, V. V. & Aslanov, L. A. (2004a). Kristallografiya, 49, 208-218 [translated as Crystallogr. Rep. 49, 158-168].],b[Albov, D. V., Rybakov, V. B., Babaev, E. V. & Aslanov, L. A. (2004b). Acta Cryst. E60, o894-o895.]) and QAHLOB (Fischer et al., 2004[Fischer, C. B., Polborn, K., Steininger, H. & Zipse, H. (2004). Z. Naturforsch. Teil B, 59, 1121-1131.]).

5. Synthesis and crystallization

A solution of the sodium salt of 2-(hy­droxy­methyl­ene)-1-cyclo­hepta­none [(1); 1.60 g, 0.01 mol], N-cyano­acetohydrazide [(2); 0.09 g, 0.01 mol] and piperidine acetate (1 ml) in water (30 ml) and ethanol (30 ml) was refluxed for 10 min. Acetic acid (1.5 ml) was added to the hot solution. The precipitated solid was collected by filtration and crystallized from ethanol, giving colourless plate-like crystals (yield 85%, m.p. 508 K).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. The NH hydrogens were located in a difference Fourier map and freely refined. The C-bound H atoms were included using a riding model starting from calculated positions: C—H = 0.95–0.99 Å with Uiso(H) = 1.2Ueq(C).

Table 2
Experimental details

Crystal data
Chemical formula C11H13N3O
Mr 203.24
Crystal system, space group Monoclinic, P21/c
Temperature (K) 100
a, b, c (Å) 8.5680 (4), 10.0475 (4), 11.6778 (5)
β (°) 103.272 (4)
V3) 978.46 (7)
Z 4
Radiation type Cu Kα
μ (mm−1) 0.74
Crystal size (mm) 0.10 × 0.10 × 0.05
 
Data collection
Diffractometer Oxford Diffraction Xcalibur Atlas Nova
Absorption correction Multi-scan (CrysAlis PRO; Agilent, 2010[Agilent (2010). CrysAlis PRO. Agilent Technologies Ltd., Yarnton, England.])
Tmin, Tmax 0.795, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 19833, 2046, 1674
Rint 0.062
(sin θ/λ)max−1) 0.630
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.109, 1.06
No. of reflections 2046
No. of parameters 144
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.28, −0.30
Computer programs: (CrysAlis PRO; Agilent, 2010[Agilent (2010). CrysAlis PRO. Agilent Technologies Ltd., Yarnton, England.]), SHELXS97 and SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and XP (Siemens, 1994[Siemens (1994). XP. Siemens Analytical X-Ray Instruments, Madison, Wisconsin, USA.]).

Supporting information


Computing details top

Data collection: (CrysAlis PRO; Agilent, 2010); cell refinement: (CrysAlis PRO; Agilent, 2010); data reduction: (CrysAlis PRO; Agilent, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

1-Amino-2-oxo-2,5,6,7,8,9-hexahydro-1H-cyclohepta[b]pyridine-3-carbonitrile top
Crystal data top
C11H13N3OF(000) = 432
Mr = 203.24Dx = 1.380 Mg m3
Monoclinic, P21/cCu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2ybcCell parameters from 6583 reflections
a = 8.5680 (4) Åθ = 3.9–76.1°
b = 10.0475 (4) ŵ = 0.74 mm1
c = 11.6778 (5) ÅT = 100 K
β = 103.272 (4)°Plate, colourless
V = 978.46 (7) Å30.10 × 0.10 × 0.05 mm
Z = 4
Data collection top
Oxford Diffraction Xcalibur Atlas Nova
diffractometer
2046 independent reflections
Radiation source: sealed X-ray tube, Nova (Cu) X-ray Source1674 reflections with I > 2σ(I)
Mirror monochromatorRint = 0.062
Detector resolution: 10.3543 pixels mm-1θmax = 76.1°, θmin = 5.3°
ω–scanh = 1010
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)
k = 1212
Tmin = 0.795, Tmax = 1.000l = 1414
19833 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.109H atoms treated by a mixture of independent and constrained refinement
S = 1.06 w = 1/[σ2(Fo2) + (0.0602P)2 + 0.2053P]
where P = (Fo2 + 2Fc2)/3
2046 reflections(Δ/σ)max < 0.001
144 parametersΔρmax = 0.28 e Å3
0 restraintsΔρmin = 0.30 e Å3
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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

8.5275 (0.0007) x + 0.7466 (0.0052) y - 3.3783 (0.0058) z = 0.3993 (0.0040)

* -0.0117 (0.0008) N1 * 0.0031 (0.0009) C2 * 0.0072 (0.0009) C3 * -0.0090 (0.0009) C4 * 0.0007 (0.0009) C4A * 0.0097 (0.0009) C9A 1.4803 (0.0024) C6 1.6155 (0.0026) C7 1.4700 (0.0023) C8

Rms deviation of fitted atoms = 0.0079

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.14967 (13)0.49677 (10)0.37289 (9)0.0161 (3)
C20.13750 (15)0.63589 (13)0.36852 (11)0.0168 (3)
C30.17684 (15)0.69947 (13)0.48064 (12)0.0168 (3)
C40.22210 (15)0.62730 (13)0.58375 (11)0.0173 (3)
H40.24510.67270.65710.021*
C4A0.23457 (16)0.48899 (13)0.58178 (11)0.0169 (3)
C50.29860 (17)0.41294 (13)0.69430 (11)0.0197 (3)
H5A0.22430.33910.70000.024*
H5B0.30250.47290.76220.024*
C60.46697 (17)0.35590 (14)0.70100 (12)0.0218 (3)
H6A0.53150.42310.67030.026*
H6B0.51970.33950.78450.026*
C70.46682 (17)0.22636 (14)0.63197 (12)0.0212 (3)
H7A0.57870.19420.64470.025*
H7B0.40550.15870.66510.025*
C80.39649 (16)0.23537 (13)0.49953 (12)0.0199 (3)
H8A0.40850.14780.46370.024*
H8B0.45960.30080.46560.024*
C90.21817 (16)0.27618 (13)0.46552 (12)0.0186 (3)
H9A0.17080.24670.38410.022*
H9B0.15970.23120.51850.022*
C9A0.19855 (15)0.42414 (13)0.47385 (11)0.0159 (3)
C100.17377 (16)0.84204 (14)0.48160 (12)0.0200 (3)
N20.12201 (15)0.43233 (12)0.26182 (10)0.0207 (3)
H010.090 (2)0.500 (2)0.2110 (18)0.036 (5)*
H020.037 (2)0.376 (2)0.2551 (16)0.030 (5)*
N30.17469 (17)0.95620 (12)0.48127 (12)0.0298 (3)
O10.09637 (12)0.69230 (9)0.27097 (8)0.0208 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0174 (6)0.0137 (5)0.0162 (5)0.0004 (4)0.0016 (4)0.0012 (4)
C20.0134 (6)0.0151 (6)0.0214 (7)0.0001 (4)0.0028 (5)0.0014 (5)
C30.0150 (6)0.0129 (6)0.0223 (6)0.0009 (4)0.0037 (5)0.0012 (5)
C40.0154 (6)0.0171 (6)0.0199 (6)0.0005 (5)0.0047 (5)0.0024 (5)
C4A0.0153 (6)0.0162 (6)0.0192 (6)0.0000 (5)0.0036 (5)0.0012 (5)
C50.0240 (7)0.0182 (6)0.0170 (6)0.0015 (5)0.0051 (5)0.0018 (5)
C60.0212 (7)0.0241 (7)0.0182 (6)0.0018 (5)0.0006 (5)0.0020 (5)
C70.0197 (7)0.0204 (7)0.0229 (7)0.0036 (5)0.0037 (5)0.0044 (5)
C80.0199 (7)0.0182 (6)0.0215 (6)0.0026 (5)0.0048 (5)0.0005 (5)
C90.0193 (7)0.0137 (6)0.0218 (6)0.0002 (5)0.0026 (5)0.0003 (5)
C9A0.0133 (6)0.0145 (6)0.0195 (6)0.0006 (4)0.0030 (5)0.0008 (4)
C100.0183 (6)0.0182 (7)0.0227 (6)0.0002 (5)0.0033 (5)0.0007 (5)
N20.0272 (7)0.0176 (6)0.0154 (5)0.0018 (5)0.0006 (5)0.0033 (4)
N30.0340 (8)0.0182 (6)0.0366 (7)0.0000 (5)0.0068 (6)0.0004 (5)
O10.0237 (5)0.0170 (4)0.0199 (5)0.0012 (4)0.0012 (4)0.0039 (4)
Geometric parameters (Å, º) top
N1—C9A1.3680 (16)C10—N31.1471 (19)
N1—C21.4017 (16)C4—H40.9500
N1—N21.4201 (15)C5—H5A0.9900
C2—O11.2486 (16)C5—H5B0.9900
C2—C31.4260 (18)C6—H6A0.9900
C3—C41.3826 (18)C6—H6B0.9900
C3—C101.4328 (18)C7—H7A0.9900
C4—C4A1.3943 (18)C7—H7B0.9900
C4A—C9A1.3892 (18)C8—H8A0.9900
C4A—C51.5101 (17)C8—H8B0.9900
C5—C61.5375 (19)C9—H9A0.9900
C6—C71.5308 (19)C9—H9B0.9900
C7—C81.5283 (18)N2—H010.90 (2)
C8—C91.5432 (18)N2—H020.91 (2)
C9—C9A1.5018 (17)
C9A—N1—C2124.66 (11)C4A—C5—H5B109.1
C9A—N1—N2119.86 (10)C6—C5—H5B109.1
C2—N1—N2115.22 (10)H5A—C5—H5B107.8
O1—C2—N1119.27 (11)C7—C6—H6A108.8
O1—C2—C3126.31 (12)C5—C6—H6A108.8
N1—C2—C3114.42 (11)C7—C6—H6B108.8
C4—C3—C2121.64 (12)C5—C6—H6B108.8
C4—C3—C10121.30 (12)H6A—C6—H6B107.7
C2—C3—C10117.01 (12)C8—C7—H7A108.3
C3—C4—C4A121.04 (12)C6—C7—H7A108.3
C9A—C4A—C4118.72 (12)C8—C7—H7B108.3
C9A—C4A—C5120.85 (12)C6—C7—H7B108.3
C4—C4A—C5120.26 (12)H7A—C7—H7B107.4
C4A—C5—C6112.46 (11)C7—C8—H8A108.7
C7—C6—C5113.75 (11)C9—C8—H8A108.7
C8—C7—C6115.79 (11)C7—C8—H8B108.7
C7—C8—C9114.41 (11)C9—C8—H8B108.7
C9A—C9—C8111.42 (11)H8A—C8—H8B107.6
N1—C9A—C4A119.48 (12)C9A—C9—H9A109.3
N1—C9A—C9119.26 (11)C8—C9—H9A109.3
C4A—C9A—C9121.22 (12)C9A—C9—H9B109.3
N3—C10—C3178.28 (16)C8—C9—H9B109.3
C3—C4—H4119.5H9A—C9—H9B108.0
C4A—C4—H4119.5N1—N2—H01102.6 (13)
C4A—C5—H5A109.1N1—N2—H02108.8 (12)
C6—C5—H5A109.1H01—N2—H02107.1 (17)
C9A—N1—C2—O1177.72 (12)C4A—C5—C6—C780.60 (15)
N2—N1—C2—O13.59 (17)C5—C6—C7—C861.27 (16)
C9A—N1—C2—C31.60 (18)C6—C7—C8—C961.68 (16)
N2—N1—C2—C3175.73 (11)C7—C8—C9—C9A80.91 (14)
O1—C2—C3—C4179.57 (13)C2—N1—C9A—C4A2.30 (19)
N1—C2—C3—C40.30 (18)N2—N1—C9A—C4A176.17 (12)
O1—C2—C3—C102.1 (2)C2—N1—C9A—C9175.43 (12)
N1—C2—C3—C10177.22 (11)N2—N1—C9A—C91.55 (18)
C2—C3—C4—C4A1.5 (2)C4—C4A—C9A—N10.99 (18)
C10—C3—C4—C4A175.93 (13)C5—C4A—C9A—N1176.19 (12)
C3—C4—C4A—C9A0.82 (19)C4—C4A—C9A—C9176.68 (12)
C3—C4—C4A—C5174.41 (12)C5—C4A—C9A—C91.48 (19)
C9A—C4A—C5—C666.67 (16)C8—C9—C9A—N1109.73 (13)
C4—C4A—C5—C6108.45 (14)C8—C9—C9A—C4A67.96 (16)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H01···O10.90 (2)2.05 (2)2.6255 (15)120.4 (16)
N2—H02···O1i0.91 (2)2.16 (2)3.0225 (15)158.2 (17)
C4—H4···O1ii0.952.453.2105 (16)137
C9—H9A···O1i0.992.633.4903 (16)146
Symmetry codes: (i) x, y1/2, z+1/2; (ii) x, y+3/2, z+1/2.
 

References

First citationAgilent (2010). CrysAlis PRO. Agilent Technologies Ltd., Yarnton, England.  Google Scholar
First citationAlbov, D. V., Mazina, O. S., Rybakov, V. B., Babaev, E. V., Chemyshev, V. V. & Aslanov, L. A. (2004a). Kristallografiya, 49, 208–218 [translated as Crystallogr. Rep. 49, 158–168].  Google Scholar
First citationAlbov, D. V., Rybakov, V. B., Babaev, E. V. & Aslanov, L. A. (2004b). Acta Cryst. E60, o894–o895.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationElgemeie, G. H. & Abd Elaziz, H. (2015). Curr. Microw. Chem. 2, 90–128.  CrossRef CAS Google Scholar
First citationElgemeie, G. H., Abou-Zeid, M., Alsaid, S., Hebishy, A. & Essa, H. (2015). Nucleosides Nucleotides Nucleic Acids, 34, 659–673.  Web of Science CrossRef CAS PubMed Google Scholar
First citationElgemeie, G. H., Abu-Zaied, M. & Azzam, R. (2016). Nucleosides Nucleotides Nucleic Acids, 35, 211–222.  Web of Science CrossRef CAS PubMed Google Scholar
First citationElgemeie, G. H. & Hamed, M. (2014). Curr. Microw. Chem. 1, 155–176.  CrossRef CAS Google Scholar
First citationElgemeie, G. H., Mahmoud, M. A. & Jones, P. G. (2002). Acta Cryst. E58, o1293–o1295.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationElgemeie, G. H., Mohamed, R. A., Hussein, H. A. & Jones, P. G. (2015). Acta Cryst. E71, 1322–1324.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationElgemeie, G. H., Salah, A. M., Mohamed, R. A. & Jones, P. G. (2015). Acta Cryst. E71, 1319–1321.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationFischer, C. B., Polborn, K., Steininger, H. & Zipse, H. (2004). Z. Naturforsch. Teil B, 59, 1121–1131.  CAS Google Scholar
First citationGroom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSiemens (1994). XP. Siemens Analytical X–Ray Instruments, Madison, Wisconsin, USA.  Google Scholar

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ISSN: 2056-9890
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