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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 64| Part 1| January 2008| Page o269
https://doi.org/10.1107/S160053680706607X

2,4-Di­amino-6-methyl-1,3,5-triazine methanol solvate

Małgorzata Kaczmarek,a Wanda Radecka-Paryzeka and Maciej Kubickia*

aDepartment of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
*Correspondence e-mail: mkubicki@amu.edu.pl

(Received 9 November 2007; accepted 7 December 2007; online 12 December 2007)

The crystal structure of the title compound, C4H7N5·CH4O, is determined by an extensive network of hydrogen bonding. A sequence of centrosymmetric dimeric associations, formed by two different N—H(amino)⋯N(ring) hydrogen bonds, connects the triazine rings into a planar mol­ecular tape. The methanol solvent mol­ecules act as di-acceptors and mono-donors of hydrogen bonds and inter­link, almost perpendicularly, the hydrogen-bonded tapes into a three-dimensional structure.

Related literature

For related literature, see: Allen (2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]); Radecka-Paryzek et al. (2005[Radecka-Paryzek, W., Patroniak, V. & Lisowski, J. (2005). Coord. Chem. Rev. 249, 2156-2175.]); Šebenik et al. (1989[Šebenik, A., Osredkar, U. & Žigon, M. (1989). Polym. Bull. 22, 155-161.]); Tashiro & Oiwa (1981[Tashiro, T. & Oiwa, M. (1981). J. Polym. Sci. Polym. Chem. 19, 645-654.]).

[Scheme 1]

Experimental

Crystal data

  • C4H7N5·CH4O

  • Mr = 157.19

  • Monoclinic, C 2/c

  • a = 21.024 (5) Å

  • b = 5.4726 (10) Å

  • c = 14.198 (3) Å

  • β = 95.66 (2)°

  • V = 1625.6 (6) Å3

  • Z = 8

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 295 (2) K

  • 0.4 × 0.2 × 0.2 mm
Data collection

  • Kuma KM4 CCD diffractometer

  • Absorption correction: none

  • 5226 measured reflections

  • 1737 independent reflections

  • 1191 reflections with I > 2σ(I)

  • Rint = 0.019
Refinement

  • R[F2 > 2σ(F2)] = 0.050

  • wR(F2) = 0.146

  • S = 1.07

  • 1737 reflections

  • 122 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.17 e Å−3

  • Δρmin = −0.28 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
O1S—H1S⋯N5 0.96 (4) 1.86 (4) 2.816 (2) 176 (3)
N2—H2B⋯O1Si 0.87 (3) 2.26 (3) 3.093 (2) 160 (2)
N2—H2A⋯N1ii 0.86 (2) 2.20 (2) 3.060 (2) 180 (2)
N4—H4B⋯O1Siii 0.89 (2) 2.27 (2) 2.956 (2) 133.2 (19)
N4—H4A⋯N3iv 0.88 (2) 2.15 (2) 3.024 (2) 177.3 (19)
Symmetry codes: (i) [x, -y+2, z+{\script{1\over 2}}]; (ii) [-x+{\script{1\over 2}}, -y+{\script{5\over 2}}, -z+2]; (iii) [-x, y, -z+{\script{3\over 2}}]; (iv) -x, -y+2, -z+2.

Data collection: CrysAlis CCD (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD (Version 1.171.31.5) and CrysAlis RED (Version 1.171.31.5). Oxford Diffraction Poland Sp. z o.o., Wrocław, Poland.]); cell refinement: CrysAlis RED (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD (Version 1.171.31.5) and CrysAlis RED (Version 1.171.31.5). Oxford Diffraction Poland Sp. z o.o., Wrocław, Poland.]); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989[Siemens (1989). Stereochemical Workstation Operation Manual. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.]); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S160053680706607X/rz2183sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S160053680706607X/rz2183Isup2.hkl

checkCIF report


Comment top

Triazine compounds are used in pharmaceutical industry as coupling agents for the synthesis of peptides and as side chain of antibiotics, as well as in formulating bactericides and fungicides. 2,4-Diamino-6-methyl-1,3,5-triazine (acetoguanamine) is used as an intermediate for pharmaceuticals and as a modifier and flexibilizer of formaldehyde resins (Šebenik et al. 1989, Tashiro et al.1981). The title compound, 2,4-diamino-6-methyl-1,3,5-triazine methanol solvate, was isolated during the efforts to prepare new lanthanide macrocyclic complexes as part of our research program involving the study of the coordination template effect in generating the supramolecular Schiff base macrocycles derived from various diamines and dicarbonyls (Radecka-Paryzek et al. 2005).

The bond lengths within the ring are exceptionally uniform in all the 2,4-diaminotriazine derivatives. For 38 compounds found in the CSD (Allen, 2002; search conditions: only organics, no disorder, no errors) the mean standard deviation of the C?N bond lengths is as small as 0.007 Å. The same is true for the title compound, the mean value of the C?N bond distances being 1.346 (14) Å. The triazine ring is planar (Fig. 1), with a maximum deviation from the least-squares plane of 0.013 (1)Å for N5. The amino groups are almost coplanar with the ring plane, the dihedral angles between the NH2 groups and the ring plane are 6(3)° for N2H2 and 2(2)° for N4H2. Only the methyl carbon atom C61 deviates significantly from the plane by 0.055 (3) Å.

The crystal structure is determined by an extensive network of hydrogen bonds. Each NH2 group acts as a donor in hydrogen bond with the ring nitrogen atoms of neighboring molecules, related by two different centres of symmetry. The sequence of such hydrogen-bonded dimers creates an almost planar molecular tape of molecules along the [101] direction (Fig. 2). The tapes are interlinked by hydrogen bonds with the methanol solvent molecules, which act as di-acceptors and mono-donors of hydrogen bonds (Fig. 3). As a result, a three-dimensional structure of almost perpendicular tapes is formed in the crystal.

Related literature top

For related literature, see: Allen (2002); Radecka-Paryzek et al. (2005); Šebenik et al. (1989); Tashiro & Oiwa (1981).

Experimental top

To a solution of lanthanum(III) nitrate complex of Schiff base ligand, product of [2 + 1] condensation of one molecule of 2,4-diamino-6-methyl-1,3,5-triazine with two molecules of 2,6-diacetylpyridine (0.1 mmol), in methanol (10 ml), 2,4-diamino-6-methyl-1,3,5-triazine (0.1 mmol) dissolved in hot methanol (10 ml) was added in order to receive the [2 + 2] Schiff base macrocyclic complex. After standing at room temperature for several hours, transparent crystals of the title compound were obtained. The crystals were initially transparent but after few minutes in open air they became opaque and gradually lost their crystallinity. Therefore the crystal used for data collection was sealed in a glass capillary.

Refinement top

The methyl hydrogen atoms were positioned geometrically (AFIX 137) and refined using a riding model, with Uiso(H) = 1.3 Ueq(C). All other hydrogen atoms were located in difference Fourier maps and freely refined.

Structure description top

Triazine compounds are used in pharmaceutical industry as coupling agents for the synthesis of peptides and as side chain of antibiotics, as well as in formulating bactericides and fungicides. 2,4-Diamino-6-methyl-1,3,5-triazine (acetoguanamine) is used as an intermediate for pharmaceuticals and as a modifier and flexibilizer of formaldehyde resins (Šebenik et al. 1989, Tashiro et al.1981). The title compound, 2,4-diamino-6-methyl-1,3,5-triazine methanol solvate, was isolated during the efforts to prepare new lanthanide macrocyclic complexes as part of our research program involving the study of the coordination template effect in generating the supramolecular Schiff base macrocycles derived from various diamines and dicarbonyls (Radecka-Paryzek et al. 2005).

The bond lengths within the ring are exceptionally uniform in all the 2,4-diaminotriazine derivatives. For 38 compounds found in the CSD (Allen, 2002; search conditions: only organics, no disorder, no errors) the mean standard deviation of the C?N bond lengths is as small as 0.007 Å. The same is true for the title compound, the mean value of the C?N bond distances being 1.346 (14) Å. The triazine ring is planar (Fig. 1), with a maximum deviation from the least-squares plane of 0.013 (1)Å for N5. The amino groups are almost coplanar with the ring plane, the dihedral angles between the NH2 groups and the ring plane are 6(3)° for N2H2 and 2(2)° for N4H2. Only the methyl carbon atom C61 deviates significantly from the plane by 0.055 (3) Å.

The crystal structure is determined by an extensive network of hydrogen bonds. Each NH2 group acts as a donor in hydrogen bond with the ring nitrogen atoms of neighboring molecules, related by two different centres of symmetry. The sequence of such hydrogen-bonded dimers creates an almost planar molecular tape of molecules along the [101] direction (Fig. 2). The tapes are interlinked by hydrogen bonds with the methanol solvent molecules, which act as di-acceptors and mono-donors of hydrogen bonds (Fig. 3). As a result, a three-dimensional structure of almost perpendicular tapes is formed in the crystal.

For related literature, see: Allen (2002); Radecka-Paryzek et al. (2005); Šebenik et al. (1989); Tashiro & Oiwa (1981).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989) and WinGX (Farrugia, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1] Fig. 1. Anisotropic displacement ellipsoid representation (at the 50% probability level) of the molecule of the title compound, together with the numbering scheme. The hydrogen atoms are drawn as spheres with arbitrary radii. The intermolecular hydrogen bond is depicted as a dashed line.
[Figure 2] Fig. 2. The molecular tape along [101] direction. Hydrogen bonds are depicted as dashed lines. Symmetry codes: (i) x,y,z (ii) -x,2 - y,-2z (iii) 1/2 - x,5/2 - y,2 - z (iv) 1/2 + x,1/2 + y,z.
[Figure 3] Fig. 3. The packing of the molecules as seen approximately along the a axis. Hydrogen bonds are shown as dashed lines.
2,4-Diamino-6-methyl-1,3,5-triazine methanol solvate top
Crystal data top
C4H7N5·CH4OF(000) = 672
Mr = 157.19Dx = 1.285 Mg m−3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 2082 reflections
a = 21.024 (5) Åθ = 4–22°
b = 5.4726 (10) ŵ = 0.10 mm−1
c = 14.198 (3) ÅT = 295 K
β = 95.66 (2)°Block, colourless
V = 1625.6 (6) Å30.4 × 0.2 × 0.2 mm
Z = 8
Data collection top
Kuma KM-4-CCD four-circle
diffractometer		1191 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.019
Graphite monochromatorθmax = 27.0°, θmin = 2.9°
Detector resolution: 8.1929 pixels mm-1h = −26→26
ω scansk = −4→6
5226 measured reflectionsl = −18→18
1737 independent 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)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.146H atoms treated by a mixture of independent and constrained refinement
S = 1.07 w = 1/[σ2(Fo2) + (0.0834P)2 + 0.3526P]
where P = (Fo2 + 2Fc2)/3
1737 reflections(Δ/σ)max = 0.001
122 parametersΔρmax = 0.17 e Å−3
0 restraintsΔρmin = −0.29 e Å−3
Crystal data top
C4H7N5·CH4OV = 1625.6 (6) Å3
Mr = 157.19Z = 8
Monoclinic, C2/cMo Kα radiation
a = 21.024 (5) ŵ = 0.10 mm−1
b = 5.4726 (10) ÅT = 295 K
c = 14.198 (3) Å0.4 × 0.2 × 0.2 mm
β = 95.66 (2)°
Data collection top
Kuma KM-4-CCD four-circle
diffractometer		1191 reflections with I > 2σ(I)
5226 measured reflectionsRint = 0.019
1737 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0500 restraints
wR(F2) = 0.146H atoms treated by a mixture of independent and constrained refinement
S = 1.07Δρmax = 0.17 e Å−3
1737 reflectionsΔρmin = −0.29 e Å−3
122 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
xyzUiso*/Ueq
N10.19697 (6)1.0111 (2)0.94292 (10)0.0405 (4)
C20.14975 (8)1.1070 (3)0.99110 (11)0.0375 (4)
N20.16650 (8)1.2910 (3)1.04951 (12)0.0491 (4)
H2B0.1372 (12)1.360 (4)1.0792 (17)0.069 (7)*
H2A0.2049 (11)1.346 (4)1.0518 (15)0.056 (6)*
N30.08942 (6)1.0268 (3)0.98441 (10)0.0410 (4)
C40.07625 (8)0.8402 (3)0.92379 (12)0.0400 (4)
N40.01687 (8)0.7548 (3)0.91381 (14)0.0576 (5)
H4B0.0074 (11)0.634 (4)0.8728 (16)0.065 (7)*
H4A−0.0141 (11)0.813 (4)0.9441 (16)0.055 (6)*
N50.11934 (6)0.7355 (3)0.87109 (10)0.0412 (4)
C60.17841 (8)0.8266 (3)0.88561 (12)0.0388 (4)
C610.22793 (9)0.7086 (4)0.83245 (15)0.0521 (5)
H61A0.26820.78980.84720.068*
H61B0.21540.72050.76570.068*
H61C0.23210.53970.85020.068*
O1S0.08620 (7)0.4874 (2)0.69953 (10)0.0574 (4)
H1S0.0976 (14)0.579 (6)0.756 (3)0.113 (11)*
C1S0.08937 (12)0.2368 (4)0.71909 (17)0.0707 (7)
H1S10.13290.19160.73800.092*
H1S20.07390.14690.66340.092*
H1S30.06350.20000.76930.092*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0315 (7)0.0499 (8)0.0406 (8)−0.0021 (6)0.0066 (6)−0.0054 (6)
C20.0315 (8)0.0475 (9)0.0331 (8)−0.0026 (7)0.0021 (6)−0.0012 (7)
N20.0350 (8)0.0597 (10)0.0532 (10)−0.0065 (7)0.0078 (7)−0.0180 (8)
N30.0327 (8)0.0499 (8)0.0412 (8)−0.0050 (6)0.0078 (6)−0.0053 (6)
C40.0344 (9)0.0465 (9)0.0397 (9)−0.0035 (7)0.0056 (7)−0.0003 (7)
N40.0382 (9)0.0674 (11)0.0689 (11)−0.0150 (8)0.0135 (8)−0.0252 (10)
N50.0387 (8)0.0436 (8)0.0419 (8)−0.0041 (6)0.0068 (6)−0.0049 (6)
C60.0365 (9)0.0442 (9)0.0358 (9)0.0014 (7)0.0034 (7)0.0019 (7)
C610.0441 (10)0.0601 (11)0.0534 (11)0.0022 (9)0.0113 (8)−0.0105 (9)
O1S0.0728 (10)0.0551 (8)0.0426 (8)0.0036 (7)−0.0031 (7)0.0031 (6)
C1S0.0870 (18)0.0544 (13)0.0731 (15)−0.0019 (11)0.0203 (13)−0.0045 (11)
Geometric parameters (Å, º) top
N1—C61.331 (2)N5—C61.335 (2)
N1—C21.365 (2)C6—C611.492 (2)
C2—N21.330 (2)C61—H61A0.9600
C2—N31.337 (2)C61—H61B0.9600
N2—H2B0.87 (3)C61—H61C0.9600
N2—H2A0.86 (2)O1S—C1S1.400 (2)
N3—C41.347 (2)O1S—H1S0.96 (4)
C4—N41.328 (2)C1S—H1S10.9600
C4—N51.358 (2)C1S—H1S20.9600
N4—H4B0.89 (2)C1S—H1S30.9600
N4—H4A0.88 (2)
C6—N1—C2114.47 (14)N1—C6—C61117.42 (15)
N2—C2—N3118.93 (16)N5—C6—C61116.44 (16)
N2—C2—N1116.28 (15)C6—C61—H61A109.5
N3—C2—N1124.78 (16)C6—C61—H61B109.5
C2—N2—H2B118.5 (17)H61A—C61—H61B109.5
C2—N2—H2A118.6 (14)C6—C61—H61C109.5
H2B—N2—H2A123 (2)H61A—C61—H61C109.5
C2—N3—C4115.34 (14)H61B—C61—H61C109.5
N4—C4—N3117.85 (16)C1S—O1S—H1S110 (2)
N4—C4—N5117.65 (17)O1S—C1S—H1S1109.5
N3—C4—N5124.49 (15)O1S—C1S—H1S2109.5
C4—N4—H4B118.5 (15)H1S1—C1S—H1S2109.5
C4—N4—H4A123.7 (14)O1S—C1S—H1S3109.5
H4B—N4—H4A118 (2)H1S1—C1S—H1S3109.5
C6—N5—C4114.73 (15)H1S2—C1S—H1S3109.5
N1—C6—N5126.14 (15)
C6—N1—C2—N2179.66 (15)N4—C4—N5—C6−178.87 (16)
C6—N1—C2—N30.7 (2)N3—C4—N5—C62.1 (3)
N2—C2—N3—C4179.99 (16)C2—N1—C6—N51.3 (2)
N1—C2—N3—C4−1.1 (3)C2—N1—C6—C61−178.50 (15)
C2—N3—C4—N4−179.45 (16)C4—N5—C6—N1−2.6 (3)
C2—N3—C4—N5−0.4 (3)C4—N5—C6—C61177.21 (15)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1S—H1S···N50.96 (4)1.86 (4)2.816 (2)176 (3)
N2—H2B···O1Si0.87 (3)2.26 (3)3.093 (2)160 (2)
N2—H2A···N1ii0.86 (2)2.20 (2)3.060 (2)180 (2)
N4—H4B···O1Siii0.89 (2)2.27 (2)2.956 (2)133.2 (19)
N4—H4A···N3iv0.88 (2)2.15 (2)3.024 (2)177.3 (19)
Symmetry codes: (i) x, −y+2, z+1/2; (ii) −x+1/2, −y+5/2, −z+2; (iii) −x, y, −z+3/2; (iv) −x, −y+2, −z+2.

Experimental details

Crystal data
Chemical formulaC4H7N5·CH4O
Mr157.19
Crystal system, space groupMonoclinic, C2/c
Temperature (K)295
a, b, c (Å)21.024 (5), 5.4726 (10), 14.198 (3)
β (°) 95.66 (2)
V (Å3)1625.6 (6)
Z8
Radiation typeMo Kα
µ (mm−1)0.10
Crystal size (mm)0.4 × 0.2 × 0.2
Data collection
DiffractometerKuma KM-4-CCD four-circle
Absorption correction–
No. of measured, independent and
observed [I > 2σ(I)] reflections		5226, 1737, 1191
Rint0.019
(sin θ/λ)max (Å−1)0.639
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.146, 1.07
No. of reflections1737
No. of parameters122
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)0.17, −0.29

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), Stereochemical Workstation Operation Manual (Siemens, 1989) and WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1S—H1S···N50.96 (4)1.86 (4)2.816 (2)176 (3)
N2—H2B···O1Si0.87 (3)2.26 (3)3.093 (2)160 (2)
N2—H2A···N1ii0.86 (2)2.20 (2)3.060 (2)180 (2)
N4—H4B···O1Siii0.89 (2)2.27 (2)2.956 (2)133.2 (19)
N4—H4A···N3iv0.88 (2)2.15 (2)3.024 (2)177.3 (19)
Symmetry codes: (i) x, −y+2, z+1/2; (ii) −x+1/2, −y+5/2, −z+2; (iii) −x, y, −z+3/2; (iv) −x, −y+2, −z+2.
 

Acknowledgements

This work was supported by the Ministry of Science and Higher Education (grant No. N204 03117 33).

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
 First citationFarrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.  CrossRef CAS IUCr Journals Google Scholar
 First citationOxford Diffraction (2006). CrysAlis CCD (Version 1.171.31.5) and CrysAlis RED (Version 1.171.31.5). Oxford Diffraction Poland Sp. z o.o., Wrocław, Poland.  Google Scholar
 First citationRadecka-Paryzek, W., Patroniak, V. & Lisowski, J. (2005). Coord. Chem. Rev. 249, 2156–2175.  Web of Science CrossRef CAS Google Scholar
 First citationŠebenik, A., Osredkar, U. & Žigon, M. (1989). Polym. Bull. 22, 155–161.  Google Scholar
 First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
 First citationSiemens (1989). Stereochemical Workstation Operation Manual. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.  Google Scholar
 First citationTashiro, T. & Oiwa, M. (1981). J. Polym. Sci. Polym. Chem. 19, 645–654.  CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 64| Part 1| January 2008| Page o269
https://doi.org/10.1107/S160053680706607X
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