N-(2,4-Dinitro­phen­yl)-N′-[nitro­(phenyl)­methyl­ene]hydrazine

Yuan, C.

doi:10.1107/S1600536808036179

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 12| December 2008| Page o2297

doi:10.1107/S1600536808036179

Open

access

N-(2,4-Dinitrophenyl)-N′-[nitro(phenyl)methylene]hydrazine

Chunlan Yuan ^a ^*

^aDepartment of Chemistry and Chemical Engineering, Baoji College of Arts and Sciences, Baoji 721007, People's Republic of China
^*Correspondence e-mail: chunlanyuan@126.com

(Received 4 September 2008; accepted 4 November 2008; online 8 November 2008)

The title compound, C₁₃H₉N₅O₆, contains three nitro groups. It is prepared by the reaction of benzaldehyde 2,4-dinitrophenylhydrazone with nitric oxide at ambient temperature. The imine group is nearly coplanar with the (2,4-dinitrophenyl)hydrazine unit. The second benzene ring and the third nitro group are twisted away from this plane, with dihedral angles of 48.5 (3) and 15.2 (3)°, respectively. Weak intramolecular N—H⋯O interactions are observed.

Related literature

For related literature regarding NO, see: Garthwaite et al. (1989 ); Murad (1999 ). For arylhydrazones, see: Chan et al. (2001 ); Försterling & Barnes (2001 ); Paschalidis et al. (2000 ). For the structure of benzaldehyde 2,4-dinitrophenylhydrazone, see Shan et al. (2003 ).

Experimental

Crystal data

C₁₃H₉N₅O₆
M_r = 331.25
Orthorhombic, P b c a
a = 6.9790 (1) Å
b = 13.469 (2) Å
c = 29.448 (8) Å
V = 2768.1 (9) Å³
Z = 8
Mo Kα radiation
μ = 0.13 mm⁻¹
T = 289 (2) K
0.52 × 0.48 × 0.22 mm

Data collection

Siemens P4 diffractometer
Absorption correction: none
3591 measured reflections
3018 independent reflections
1537 reflections with I > 2σ(I)
R_int = 0.0000
3 standard reflections every 97 reflections intensity decay: 1.0%

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.059
S = 0.98
3018 reflections
222 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2N⋯O2	0.894 (15)	1.966 (15)	2.591 (2)	125.7 (13)

Data collection: XSCANS (Siemens, 1996 ); cell refinement: XSCANS; data reduction: SHELXTL (Sheldrick, 2008 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S1600536808036179/ez2141sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808036179/ez2141Isup2.hkl

checkCIF report

Comment top

Nitric oxide (NO) has been found recently to play an important role in chemistry, biology and medicine (Garthwaite et al., 1989; Murad, 1999). In recent years, arylhydrazones have been utilized for the analysis of carbonyl compounds (Chan et al., 2001). Some arylhydrazones and their nitration products were found to have pharmacological properties (Försterling & Barnes, 2001; Paschalidis et al., 2000). Here we report the reaction of NO with an arylhydrazone, where the title compound, (I), was obtained by the reaction of NO with benzaldehyde-2,4-dinitrophenylhydrazone.

The structure of (I) (Fig.1), shows that this reaction resulted in the addition of a third NO₂ group, which is attached to the carbon atom C7, with an O1—N3—C7—C6 torsion angle of -11.6 (3)°. The imine double bond in benzaldehyde 2,4-dinitrophenylhydrazone was preserved, as indicated by the N1═C7 distance [1.2779 (19) Å] being similar to that of 1.275 (2)Å in the original compound (Shan et al., 2003). The other two nitro groups are co-planar with the benzene ring that they are attached to, with O4—N4—C12—C13 and O5—N5—C11—C12 torsion angles of 7.0 (3) and 0.0 (3)° respectively. There is a weak intramolecular N2—H(2 N)···O2 interaction.

Related literature top

For related literature regarding NO, see: Garthwaite et al. (1989); Murad (1999). For literature regarding arylhydrazones, see: Chan et al. (2001); Försterling & Barnes (2001); Paschalidis et al. (2000). For the structure of benzaldehyde 2,4-dinitrophenylhydrazone, see Shan et al. (2003).

Experimental top

A stock solution was prepared by dissolving 0.5 mol benzaldehyde -2,4-dinitrophenylhydrazine in 100 ml dry CH₂Cl₂. NO was produced by the reaction of 1 M H₂SO₄ solution trickled into an aqueous saturated NaNO₂ solution through a funnel at a pre-determined speed, while stirring under an argon atmosphere. NO was carried by argon and purified by passing it through a series of scrubbing bottles containing 4M NaOH, distilled water and CaCl₂ in turn. All the above bottles were under an argon atmosphere. The purified NO was bubbled through a previously degassed stirred stock solution at room temperature for an appropriate time. After the reaction was completed, as indicated by TLC, the reaction mixture was dried with anhydrous MgSO₄, concentrated under vacuum and purified by column chromatography on silica–gel (200–300 mesh, ethyl acetate–hexane) yielding the pure title compound.

Computing details top

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS (Siemens, 1996); data reduction: SHELXTL (Sheldrick, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The structure of the dimer formation in (I),showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are not shown.
	Fig. 2. The crystal packing of (I), viewed along the b axis.

N-(2,4-Dinitrophenyl)-N'-[nitro(phenyl)methylene]hydrazine top

Crystal data top

C₁₃H₉N₅O₆	D_x = 1.590 Mg m⁻³
M_r = 331.25	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 26 reflections
a = 6.9790 (1) Å	θ = 3.4–12.5°
b = 13.469 (2) Å	µ = 0.13 mm⁻¹
c = 29.448 (8) Å	T = 289 K
V = 2768.1 (9) Å³	Prism, yellow
Z = 8	0.52 × 0.48 × 0.22 mm
F(000) = 1360

Data collection top

Siemens P4 diffractometer	R_int = 0.000
Radiation source: normal-focus sealed tube	θ_max = 27.0°, θ_min = 1.4°
Graphite monochromator	h = 0→8
ω scans	k = 0→17
3591 measured reflections	l = 0→37
3018 independent reflections	3 standard reflections every 97 reflections
1537 reflections with I > 2σ(I)	intensity decay: 1.0%

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.039	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.059	w = 1/[σ²(F_o²) + (0.0116P)²] where P = (F_o² + 2F_c²)/3
S = 0.98	(Δ/σ)_max = 0.001
3018 reflections	Δρ_max = 0.20 e Å⁻³
222 parameters	Δρ_min = −0.14 e Å⁻³
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00375 (18)

Crystal data top

C₁₃H₉N₅O₆	V = 2768.1 (9) Å³
M_r = 331.25	Z = 8
Orthorhombic, Pbca	Mo Kα radiation
a = 6.9790 (1) Å	µ = 0.13 mm⁻¹
b = 13.469 (2) Å	T = 289 K
c = 29.448 (8) Å	0.52 × 0.48 × 0.22 mm

Data collection top

Siemens P4 diffractometer	R_int = 0.000
3591 measured reflections	3 standard reflections every 97 reflections
3018 independent reflections	intensity decay: 1.0%
1537 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.059	H atoms treated by a mixture of independent and constrained refinement
S = 0.98	Δρ_max = 0.20 e Å⁻³
3018 reflections	Δρ_min = −0.14 e Å⁻³
222 parameters

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.2792 (2)	0.72703 (10)	0.26225 (4)	0.0655 (5)
O2	0.4128 (2)	0.58358 (10)	0.27056 (4)	0.0696 (5)
O3	0.5250 (2)	0.37214 (9)	0.30832 (4)	0.0587 (4)
O4	0.5513 (2)	0.23410 (9)	0.34501 (4)	0.0668 (5)
O5	0.7770 (3)	0.22039 (11)	0.49622 (4)	0.0826 (6)
O6	0.8082 (2)	0.35414 (10)	0.53534 (4)	0.0827 (6)
N1	0.5194 (2)	0.63895 (10)	0.35787 (5)	0.0411 (4)
N2	0.5362 (2)	0.54088 (11)	0.35121 (5)	0.0423 (4)
N3	0.3764 (3)	0.66797 (13)	0.28337 (5)	0.0489 (5)
N4	0.5574 (2)	0.32486 (12)	0.34320 (5)	0.0463 (4)
N5	0.7673 (3)	0.31066 (14)	0.50021 (5)	0.0599 (5)
C1	0.3799 (3)	0.82777 (13)	0.38520 (6)	0.0409 (5)
H1	0.3459	0.7770	0.4050	0.049*
C2	0.3749 (3)	0.92498 (14)	0.39969 (6)	0.0459 (5)
H2	0.3372	0.9394	0.4293	0.055*
C3	0.4251 (3)	1.00085 (14)	0.37089 (6)	0.0490 (6)
H3	0.4223	1.0663	0.3810	0.059*
C4	0.4797 (3)	0.97942 (14)	0.32689 (6)	0.0509 (6)
H4	0.5137	1.0307	0.3073	0.061*
C5	0.4842 (3)	0.88204 (14)	0.31166 (6)	0.0449 (5)
H5	0.5195	0.8682	0.2819	0.054*
C6	0.4359 (3)	0.80519 (13)	0.34096 (6)	0.0368 (5)
C7	0.4514 (3)	0.69945 (13)	0.32858 (6)	0.0387 (5)
C8	0.5928 (3)	0.48344 (13)	0.38722 (6)	0.0376 (5)
C9	0.6383 (3)	0.52778 (13)	0.42912 (6)	0.0433 (5)
H9	0.6295	0.5964	0.4322	0.052*
C10	0.6953 (3)	0.47186 (14)	0.46549 (6)	0.0453 (5)
H10	0.7271	0.5023	0.4928	0.054*
C11	0.7052 (3)	0.37003 (14)	0.46136 (6)	0.0424 (5)
C12	0.6595 (3)	0.32304 (13)	0.42157 (6)	0.0422 (5)
H12	0.6654	0.2542	0.4194	0.051*
C13	0.6048 (3)	0.37961 (13)	0.38483 (6)	0.0376 (5)
H2N	0.508 (2)	0.5131 (11)	0.3244 (5)	0.045 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0715 (11)	0.0759 (10)	0.0491 (9)	0.0080 (10)	−0.0181 (8)	−0.0017 (8)
O2	0.1089 (14)	0.0566 (9)	0.0433 (8)	0.0080 (10)	−0.0062 (9)	−0.0146 (7)
O3	0.0786 (12)	0.0550 (9)	0.0426 (8)	−0.0004 (9)	−0.0118 (8)	−0.0065 (7)
O4	0.0932 (13)	0.0360 (8)	0.0711 (10)	0.0018 (9)	−0.0160 (9)	−0.0131 (7)
O5	0.1295 (16)	0.0517 (10)	0.0666 (10)	0.0200 (12)	−0.0158 (11)	0.0040 (9)
O6	0.1324 (17)	0.0721 (11)	0.0437 (8)	0.0087 (11)	−0.0200 (10)	−0.0044 (8)
N1	0.0411 (11)	0.0381 (9)	0.0443 (9)	0.0011 (9)	0.0036 (8)	0.0007 (8)
N2	0.0489 (12)	0.0416 (10)	0.0365 (10)	−0.0013 (9)	−0.0036 (9)	−0.0058 (8)
N3	0.0519 (13)	0.0583 (12)	0.0366 (10)	−0.0064 (11)	0.0015 (9)	0.0009 (9)
N4	0.0429 (12)	0.0467 (11)	0.0492 (10)	0.0015 (9)	−0.0012 (10)	−0.0086 (9)
N5	0.0738 (15)	0.0586 (13)	0.0471 (11)	0.0100 (12)	−0.0023 (11)	0.0012 (10)
C1	0.0408 (13)	0.0460 (12)	0.0358 (11)	0.0008 (11)	−0.0005 (10)	0.0064 (9)
C2	0.0467 (13)	0.0548 (13)	0.0362 (11)	0.0046 (12)	0.0001 (10)	−0.0056 (10)
C3	0.0483 (14)	0.0410 (12)	0.0577 (13)	0.0047 (11)	−0.0079 (12)	−0.0038 (11)
C4	0.0557 (15)	0.0493 (13)	0.0478 (12)	−0.0006 (12)	−0.0034 (12)	0.0138 (10)
C5	0.0477 (14)	0.0556 (13)	0.0315 (10)	0.0000 (11)	−0.0016 (10)	0.0050 (10)
C6	0.0350 (12)	0.0441 (11)	0.0312 (10)	0.0009 (10)	−0.0025 (9)	0.0009 (9)
C7	0.0397 (13)	0.0449 (12)	0.0314 (10)	−0.0033 (11)	0.0025 (10)	−0.0002 (9)
C8	0.0357 (12)	0.0393 (11)	0.0377 (11)	−0.0021 (10)	0.0033 (10)	0.0007 (9)
C9	0.0518 (14)	0.0379 (11)	0.0404 (11)	0.0013 (11)	0.0042 (10)	−0.0063 (9)
C10	0.0509 (15)	0.0497 (12)	0.0352 (11)	0.0000 (12)	0.0022 (10)	−0.0045 (10)
C11	0.0462 (14)	0.0458 (12)	0.0352 (10)	0.0029 (12)	0.0016 (10)	0.0022 (10)
C12	0.0402 (12)	0.0377 (11)	0.0488 (12)	0.0020 (10)	0.0046 (10)	−0.0015 (10)
C13	0.0362 (12)	0.0398 (11)	0.0367 (10)	−0.0014 (10)	0.0006 (10)	−0.0080 (9)

Geometric parameters (Å, º) top

O1—N3	1.2163 (17)	C2—H2	0.9300
O2—N3	1.2244 (17)	C3—C4	1.381 (2)
O3—N4	1.2296 (17)	C3—H3	0.9300
O4—N4	1.2244 (17)	C4—C5	1.386 (2)
O5—N5	1.2233 (17)	C4—H4	0.9300
O6—N5	1.2227 (18)	C5—C6	1.389 (2)
N1—C7	1.2779 (19)	C5—H5	0.9300
N1—N2	1.3405 (18)	C6—C7	1.474 (2)
N2—C8	1.371 (2)	C8—C13	1.403 (2)
N2—H2N	0.894 (15)	C8—C9	1.407 (2)
N3—C7	1.492 (2)	C9—C10	1.368 (2)
N4—C13	1.468 (2)	C9—H9	0.9300
N5—C11	1.462 (2)	C10—C11	1.379 (2)
C1—C2	1.378 (2)	C10—H10	0.9300
C1—C6	1.394 (2)	C11—C12	1.369 (2)
C1—H1	0.9300	C12—C13	1.377 (2)
C2—C3	1.373 (2)	C12—H12	0.9300

C7—N1—N2	124.20 (15)	C4—C5—H5	120.0
N1—N2—C8	117.91 (15)	C6—C5—H5	120.0
N1—N2—H2N	121.5 (10)	C5—C6—C1	119.08 (16)
C8—N2—H2N	120.6 (10)	C5—C6—C7	123.26 (16)
O1—N3—O2	124.43 (17)	C1—C6—C7	117.56 (16)
O1—N3—C7	117.78 (16)	N1—C7—C6	118.45 (16)
O2—N3—C7	117.76 (17)	N1—C7—N3	123.46 (16)
O4—N4—O3	123.17 (16)	C6—C7—N3	117.99 (16)
O4—N4—C13	118.22 (16)	N2—C8—C13	122.75 (17)
O3—N4—C13	118.61 (15)	N2—C8—C9	120.25 (16)
O6—N5—O5	122.99 (18)	C13—C8—C9	116.98 (17)
O6—N5—C11	118.00 (17)	C10—C9—C8	121.21 (17)
O5—N5—C11	119.01 (17)	C10—C9—H9	119.4
C2—C1—C6	120.27 (17)	C8—C9—H9	119.4
C2—C1—H1	119.9	C9—C10—C11	119.55 (17)
C6—C1—H1	119.9	C9—C10—H10	120.2
C3—C2—C1	120.63 (17)	C11—C10—H10	120.2
C3—C2—H2	119.7	C12—C11—C10	121.58 (18)
C1—C2—H2	119.7	C12—C11—N5	119.07 (17)
C2—C3—C4	119.61 (17)	C10—C11—N5	119.35 (17)
C2—C3—H3	120.2	C11—C12—C13	118.75 (17)
C4—C3—H3	120.2	C11—C12—H12	120.6
C3—C4—C5	120.49 (18)	C13—C12—H12	120.6
C3—C4—H4	119.8	C12—C13—C8	121.91 (17)
C5—C4—H4	119.8	C12—C13—N4	116.14 (16)
C4—C5—C6	119.90 (17)	C8—C13—N4	121.95 (17)

C7—N1—N2—C8	−173.30 (18)	N2—C8—C9—C10	−179.95 (17)
C6—C1—C2—C3	−0.1 (3)	C13—C8—C9—C10	1.3 (3)
C1—C2—C3—C4	0.5 (3)	C8—C9—C10—C11	−1.2 (3)
C2—C3—C4—C5	0.0 (3)	C9—C10—C11—C12	0.1 (3)
C3—C4—C5—C6	−0.8 (3)	C9—C10—C11—N5	179.60 (17)
C4—C5—C6—C1	1.2 (3)	O6—N5—C11—C12	179.67 (19)
C4—C5—C6—C7	−175.08 (19)	O5—N5—C11—C12	0.0 (3)
C2—C1—C6—C5	−0.7 (3)	O6—N5—C11—C10	0.2 (3)
C2—C1—C6—C7	175.76 (18)	O5—N5—C11—C10	−179.5 (2)
N2—N1—C7—C6	178.19 (17)	C10—C11—C12—C13	0.8 (3)
N2—N1—C7—N3	1.8 (3)	N5—C11—C12—C13	−178.71 (17)
C5—C6—C7—N1	137.61 (19)	C11—C12—C13—C8	−0.6 (3)
C1—C6—C7—N1	−38.7 (3)	C11—C12—C13—N4	−179.89 (16)
C5—C6—C7—N3	−45.8 (3)	N2—C8—C13—C12	−179.11 (17)
C1—C6—C7—N3	137.86 (16)	C9—C8—C13—C12	−0.4 (3)
O1—N3—C7—N1	164.76 (18)	N2—C8—C13—N4	0.1 (3)
O2—N3—C7—N1	−13.5 (3)	C9—C8—C13—N4	178.85 (16)
O1—N3—C7—C6	−11.6 (3)	O4—N4—C13—C12	7.0 (3)
O2—N3—C7—C6	170.13 (18)	O3—N4—C13—C12	−173.35 (17)
N1—N2—C8—C13	176.35 (17)	O4—N4—C13—C8	−172.31 (18)
N1—N2—C8—C9	−2.3 (3)	O3—N4—C13—C8	7.4 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2N···O2	0.894 (15)	1.966 (15)	2.591 (2)	125.7 (13)

Experimental details

Crystal data
Chemical formula	C₁₃H₉N₅O₆
M_r	331.25
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	289
a, b, c (Å)	6.9790 (1), 13.469 (2), 29.448 (8)
V (Å³)	2768.1 (9)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.13
Crystal size (mm)	0.52 × 0.48 × 0.22

Data collection
Diffractometer	Siemens P4 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	3591, 3018, 1537
R_int	0.000
(sin θ/λ)_max (Å⁻¹)	0.639

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.059, 0.98
No. of reflections	3018
No. of parameters	222
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.14

Computer programs: XSCANS (Siemens, 1996), SHELXTL (Sheldrick, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008).

Selected bond lengths (Å) top

N1—C7

1.2779 (19)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2N···O2	0.894 (15)	1.966 (15)	2.591 (2)	125.7 (13)

Acknowledgements

I am grateful for financial support from Foster Industrial Projects (grant No. 06JC25) of Shaanxi Province and the main project (grant No. 04JS37) of the Key Laboratory of Shaanxi Province, People's Republic of China.

References

Chan, W. H., Shuang, S. & Choi, M. M. F. (2001). Analyst, 126, 720–723. Web of Science CrossRef PubMed CAS Google Scholar
Försterling, F. H. & Barnes, C. E. (2001). J. Organomet. Chem. 617, 561–570. Google Scholar
Garthwaite, J., Garthwaite, G., Palmer, R. M. & Moncada, S. (1989). Eur. J. Pharmacol. 172, 413–417. CrossRef CAS PubMed Web of Science Google Scholar
Murad, F. (1999). Angew. Chem. Int. Ed. 38, 1857–1868. CrossRef Google Scholar
Paschalidis, D. G., Tossidis, I. A. & Gdaniec, M. (2000). Polyhedron, 19, 2629–2637. Web of Science CSD CrossRef CAS Google Scholar
Shan, S., Xu, D.-J., Hung, C.-H., Wu, J.-Y. & Chiang, M. Y. (2003). Acta Cryst. C59, o135–o136. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siemens (1996). XSCANS. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Google Scholar