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Urotropin (U) and azelaic acid (AA) form 1:1 co-crystals (UA) that give rise to a rather complex diffraction pattern, the main features of which are diffuse rods and bands in addition to the Bragg reflections. UA is characterized by solvent inclusions, parasite phases, and high vacancy and dislocation densities. These defects compounded with the pronounced tendency of U to escape from the crystal edifice lead to at least seven exotic phase transitions (many of which barely manifest themselves in a differential scanning calorimetry trace). These involve different incommensurate phases and a peritectoid reaction in the recrystallization regime (T_{h}\, \gt \,0.6). The system may be understood as an OD (order–disorder) structure based on a layer with layer group P(c)c2 and cell a_{o} ≃ 4.7, b ≃ 26.1 and c ≃ 14.4 Å. At 338 K the layer stacking is random, but with decreasing temperature the build-up of an orthorhombic MDO (maximal degree of order) structure with cell a_1 = 2a_{o}, b_1 = b, c_1 = c and space group Pcc2 is begun (at ∼301 K). The superposition structure of the OD system at T = 286 (1) K with space group Bmmb and cell \widehat{\bf a} = 2{\bf a}_{o}, \widehat{\bf b} = {\bf b} and {\widehat{\bf c}} = {\bf c}/2 owes its cohesion to van der Waals interactions between the AA chains and to three types of hydrogen bonds of varied strength between U—U and U—AA. Before reaching completion, this MDO structure is transformed, at 282 K, into a monoclinic one with cell a_{m} = −a_{o} + {}c/4, b_{m} = b, c_{m} = −2({\bf a}_{o} + {c}/2), space group P{{2_1}/{c}}, spontaneous deformation ∼2°, and ferroelastic domains. This transformation is achieved in two steps: first a furtive triggering transition, which is not yet fully understood, and second an improper ferroelastic transition. At ∼233 K, the system reaches its ground state (cell {\bf a}_{M} = {\bf a}_{m}, {\bf b}_{M} = {\bf b}, {\bf c}_{M} = {\bf c}_{m} and space group P{{2_1}/{c}}) via an irreversible transition. The phase transitions below 338 K are described by a model based on the interaction of two thermally activated slip systems. The OD structure is described in terms of a three-dimensional Monte Carlo model that involves first- and second-neighbour interactions along the a axis and first-neighbour interactions along the b and c axes. This model includes random shifts of the chains along their axes and satisfactorily accounts for most features that are seen in the observed diffraction pattern.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768102022164/lc0055sup1.cif
Contains datablock global

CCDC references: 1157222; 1157223; 205167

Computing details top

Data collection: Stoe IPDS; cell refinement: Stoe IPDS; data reduction: Stoe IPDS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Bruker XP; software used to prepare material for publication: Bruker SHELXTL.

(global) top
Crystal data top
(C6H12N4·C9H16O4)Dx = 1.231 Mg m3
Mr = 328.41Melting point: 403 K
Orthorhombic, BmmbMo Kα radiation, λ = 0.71073 Å
a = 9.4157 (19) ÅCell parameters from 721 reflections
b = 26.124 (5) Åθ = 14.5–24.1°
c = 7.2034 (14) ŵ = 0.09 mm1
V = 1771.9 (6) Å3T = 286 K
Z = 4Platelet, colourless
F(000) = 7120.72 × 0.56 × 0.04 mm
Data collection top
Stoe IPDS
diffractometer
539 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.053
Graphite monochromatorθmax = 25.0°, θmin = 3.6°
Detector resolution: 6.67 pixels mm-1h = 1010
φ scansk = 3131
6062 measured reflectionsl = 88
818 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)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.126H atoms treated by a mixture of independent and constrained refinement
S = 0.91 w = 1/[σ2(Fo2) + (0.0754P)2 + 0.4007P]
where P = (Fo2 + 2Fc2)/3
818 reflections(Δ/σ)max < 0.001
110 parametersΔρmax = 0.15 e Å3
0 restraintsΔρmin = 0.13 e Å3
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.

Authors remarks: Note that the structure is disordered, with the superposition of two acid chains and splitted carboxylic functions. This leads to problematic calculations of torsion angles, in the check-CIF procedure.

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*/UeqOcc. (<1)
O10.5913 (3)0.37538 (12)0.2149 (4)0.0991 (10)0.50
H10.50000.343 (2)0.298 (8)0.23 (2)*
O2A0.3868 (10)0.3719 (5)0.0919 (13)0.139 (4)0.25
O2B0.4232 (9)0.3570 (3)0.0196 (10)0.100 (2)0.25
N10.50000.29636 (7)0.4327 (2)0.0638 (5)
N20.62853 (18)0.25000.6708 (2)0.0706 (6)
C10.50000.38525 (9)0.0717 (3)0.0717 (7)
C20.5749 (4)0.42167 (13)0.0624 (5)0.0731 (9)0.50
H2A0.61510.44990.00740.107 (13)*0.50
H2B0.65260.40370.12220.108 (13)*0.50
C30.4764 (11)0.44274 (12)0.2102 (4)0.075 (2)0.50
H3A0.42820.41460.27130.107 (13)*0.50
H3B0.40490.46410.15190.101 (13)*0.50
C40.5559 (4)0.47382 (15)0.3530 (5)0.0865 (12)0.50
H4A0.62300.45140.41510.145 (19)*0.50
H4B0.61040.49980.28850.133 (17)*0.50
C50.4662 (7)0.50000.50000.079 (3)0.50
H5B0.40550.52520.44090.118*0.25
H5C0.40550.47480.55910.118*0.25
C70.6267 (2)0.29466 (8)0.5523 (2)0.0798 (6)
H7A0.71110.29460.47510.114 (7)*
H7B0.62930.32520.62890.109 (6)*
C80.50000.25000.7842 (4)0.0732 (10)
H8A0.50000.28000.86350.11 (6)*0.50
H8B0.50000.22000.86350.11 (6)*0.50
C90.50000.25000.3177 (4)0.0569 (7)
H9A0.58330.25000.23850.06 (3)*0.50
H9B0.41670.25000.23850.08 (4)*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.100 (2)0.1015 (18)0.0958 (18)0.0275 (16)0.0252 (17)0.0294 (16)
O2A0.074 (5)0.232 (11)0.111 (7)0.083 (6)0.003 (5)0.047 (7)
O2B0.109 (6)0.108 (4)0.082 (4)0.065 (4)0.019 (4)0.033 (3)
N10.0748 (13)0.0618 (10)0.0546 (9)0.0000.0000.0048 (8)
N20.0462 (11)0.1139 (15)0.0517 (9)0.0000.0103 (8)0.000
C10.086 (2)0.0550 (13)0.0741 (15)0.0000.0000.0046 (11)
C20.077 (2)0.0646 (17)0.0776 (19)0.0102 (16)0.0014 (16)0.0102 (17)
C30.081 (7)0.0614 (14)0.0837 (16)0.005 (2)0.001 (2)0.0100 (13)
C40.093 (3)0.082 (2)0.085 (2)0.0042 (18)0.0022 (18)0.028 (2)
C50.083 (8)0.066 (2)0.089 (3)0.0000.0000.012 (2)
C70.0700 (12)0.1003 (12)0.0691 (10)0.0321 (9)0.0016 (9)0.0086 (9)
C80.068 (2)0.109 (3)0.0422 (14)0.0000.0000.000
C90.0495 (17)0.0789 (19)0.0424 (12)0.0000.0000.000
Geometric parameters (Å, º) top
O1—O2Ai0.914 (9)C1—C2i1.529 (4)
O1—C11.367 (3)C1—C21.529 (4)
O1—O2Bi1.493 (8)C2—C31.516 (7)
O1—O1i1.720 (7)C2—H2A0.9700
O1—H11.34 (4)C2—H2B0.9700
O2A—O2B0.735 (13)C3—C41.510 (6)
O2A—O1i0.914 (9)C3—H3A0.9700
O2A—C11.131 (9)C3—H3B0.9700
O2A—C2i1.748 (11)C4—C51.518 (5)
O2A—H7Bii2.7267C4—H4A0.9700
O2B—C11.100 (8)C4—H4B0.9700
O2B—O2Bi1.447 (18)C5—C4iv1.518 (5)
O2B—O1i1.493 (8)C5—H5B0.9700
O2B—C2i1.790 (8)C5—H5C0.9700
N1—C91.467 (2)C7—H7A0.9700
N1—C71.473 (2)C7—H7B0.9700
N1—C7i1.473 (2)C8—N2v1.460 (2)
N2—C7iii1.446 (2)C8—H8A0.9700
N2—C71.446 (2)C8—H8B0.9700
N2—C81.460 (2)C9—N1iii1.467 (2)
C1—O2Bi1.100 (8)C9—H9A0.9700
C1—O2Ai1.131 (9)C9—H9B0.9700
C1—O1i1.367 (3)
O2Ai—O1—C155.2 (6)O2A—C1—C2i80.7 (6)
O2Ai—O1—O2Bi22.4 (9)O2Ai—C1—C2i135.1 (6)
C1—O1—O2Bi45.0 (3)O1—C1—C2i152.2 (3)
O2Ai—O1—O1i103.0 (6)O1i—C1—C2i107.69 (19)
C1—O1—O1i51.04 (16)O2B—C1—C2120.4 (4)
O2Bi—O1—O1i84.8 (4)O2Bi—C1—C284.2 (5)
O2Ai—O1—H1121 (2)O2A—C1—C2135.1 (6)
C1—O1—H193.0 (19)O2Ai—C1—C280.7 (6)
O2Bi—O1—H199 (2)O1—C1—C2107.69 (19)
O1i—O1—H150.2 (16)O1i—C1—C2152.2 (3)
O2B—O2A—O1i129.4 (19)C2i—C1—C255.0 (3)
O2B—O2A—C168.5 (11)C3—C2—C1112.8 (4)
O1i—O2A—C183.2 (8)C3—C2—H2A109.0
O2B—O2A—C2i81.2 (12)C1—C2—H2A109.0
O1i—O2A—C2i119.7 (11)C3—C2—H2B109.0
C1—O2A—C2i59.6 (5)C1—C2—H2B109.0
O2B—O2A—H7Bii104.3H2A—C2—H2B107.8
O1i—O2A—H7Bii98.7C4—C3—C2111.7 (7)
C1—O2A—H7Bii171.3C4—C3—H3A109.3
C2i—O2A—H7Bii125.3C2—C3—H3A109.3
O2A—O2B—C173.1 (12)C4—C3—H3B109.3
O2A—O2B—O2Bi117.8 (13)C2—C3—H3B109.3
C1—O2B—O2Bi48.9 (5)H3A—C3—H3B107.9
O2A—O2B—O1i28.3 (11)C3—C4—C5116.2 (5)
C1—O2B—O1i61.5 (4)C3—C4—H4A108.2
O2Bi—O2B—O1i95.2 (4)C5—C4—H4A108.2
O2A—O2B—C2i74.9 (13)C3—C4—H4B108.2
C1—O2B—C2i58.2 (4)C5—C4—H4B108.2
O2Bi—O2B—C2i89.4 (3)H4A—C4—H4B107.4
O1i—O2B—C2i90.5 (5)C4—C5—C4iv112.3 (5)
C9—N1—C7107.79 (12)C4—C5—H5B109.1
C9—N1—C7i107.79 (12)C4iv—C5—H5B109.1
C7—N1—C7i108.26 (18)C4—C5—H5C109.1
C7iii—N2—C7107.62 (18)C4iv—C5—H5C109.1
C7iii—N2—C8108.71 (12)H5B—C5—H5C107.9
C7—N2—C8108.71 (12)N2—C7—N1112.28 (14)
O2B—C1—O2Bi82.3 (10)N2—C7—H7A109.1
O2B—C1—O2A38.4 (7)N1—C7—H7A109.1
O2Bi—C1—O2A117.2 (8)N2—C7—H7B109.1
O2B—C1—O2Ai117.2 (8)N1—C7—H7B109.1
O2Bi—C1—O2Ai38.4 (7)H7A—C7—H7B107.9
O2A—C1—O2Ai140.9 (13)N2—C8—N2v112.0 (2)
O2B—C1—O1123.0 (5)N2—C8—H8A109.2
O2Bi—C1—O173.6 (4)N2v—C8—H8A109.2
O2A—C1—O1115.9 (6)N2—C8—H8B109.2
O2Ai—C1—O141.6 (5)N2v—C8—H8B109.2
O2B—C1—O1i73.6 (4)H8A—C8—H8B107.9
O2Bi—C1—O1i123.0 (5)N1—C9—N1iii111.3 (2)
O2A—C1—O1i41.6 (5)N1—C9—H9A109.4
O2Ai—C1—O1i115.9 (6)N1iii—C9—H9A109.4
O1—C1—O1i77.9 (3)N1—C9—H9B109.4
O2B—C1—C2i84.2 (5)N1iii—C9—H9B109.4
O2Bi—C1—C2i120.4 (4)H9A—C9—H9B108.0
O1i—O2A—O2B—C160.7 (19)O1i—O2A—C1—O126.1 (12)
C2i—O2A—O2B—C160.7 (3)C2i—O2A—C1—O1156.5 (4)
H7Bii—O2A—O2B—C1174.9H7Bii—O2A—C1—O176.7
O1i—O2A—O2B—O2Bi40 (3)O2B—O2A—C1—O1i137.3 (19)
C1—O2A—O2B—O2Bi20.4 (8)C2i—O2A—C1—O1i130.4 (9)
C2i—O2A—O2B—O2Bi81.1 (8)H7Bii—O2A—C1—O1i102.8
H7Bii—O2A—O2B—O2Bi154.5O2B—O2A—C1—C2i92.3 (12)
C1—O2A—O2B—O1i60.7 (19)O1i—O2A—C1—C2i130.4 (9)
C2i—O2A—O2B—O1i121 (2)H7Bii—O2A—C1—C2i126.8
H7Bii—O2A—O2B—O1i114.2O2B—O2A—C1—C283.6 (16)
O1i—O2A—O2B—C2i121 (2)O1i—O2A—C1—C2139.2 (6)
C1—O2A—O2B—C2i60.7 (3)C2i—O2A—C1—C28.8 (8)
H7Bii—O2A—O2B—C2i124.4H7Bii—O2A—C1—C2118.1
O2A—O2B—C1—O2Bi155.8 (11)O2Ai—O1—C1—O2B95.1 (13)
O1i—O2B—C1—O2Bi127.8 (4)O2Bi—O1—C1—O2B69.0 (10)
C2i—O2B—C1—O2Bi121.8 (4)O1i—O1—C1—O2B61.1 (6)
O2Bi—O2B—C1—O2A155.8 (11)O2Ai—O1—C1—O2Bi26.1 (13)
O1i—O2B—C1—O2A28.0 (12)O1i—O1—C1—O2Bi130.1 (5)
C2i—O2B—C1—O2A82.4 (13)O2Ai—O1—C1—O2A138.8 (18)
O2A—O2B—C1—O2Ai139.2 (17)O2Bi—O1—C1—O2A112.7 (9)
O2Bi—O2B—C1—O2Ai16.6 (7)O1i—O1—C1—O2A17.4 (8)
O1i—O2B—C1—O2Ai111.2 (7)O2Bi—O1—C1—O2Ai26.1 (13)
C2i—O2B—C1—O2Ai138.4 (6)O1i—O1—C1—O2Ai156.2 (11)
O2A—O2B—C1—O191.2 (14)O2Ai—O1—C1—O1i156.2 (11)
O2Bi—O2B—C1—O164.7 (4)O2Bi—O1—C1—O1i130.1 (5)
O1i—O2B—C1—O163.2 (5)O2Ai—O1—C1—C2i98.8 (11)
C2i—O2B—C1—O1173.5 (4)O2Bi—O1—C1—C2i124.8 (7)
O2A—O2B—C1—O1i28.0 (12)O1i—O1—C1—C2i105.1 (5)
O2Bi—O2B—C1—O1i127.8 (4)O2Ai—O1—C1—C252.1 (11)
C2i—O2B—C1—O1i110.4 (3)O2Bi—O1—C1—C278.2 (5)
O2A—O2B—C1—C2i82.4 (13)O1i—O1—C1—C2151.8 (3)
O2Bi—O2B—C1—C2i121.8 (4)O2B—C1—C2—C341.6 (7)
O1i—O2B—C1—C2i110.4 (3)O2Bi—C1—C2—C3119.1 (5)
O2A—O2B—C1—C2125.6 (12)O2A—C1—C2—C34.1 (11)
O2Bi—O2B—C1—C278.6 (5)O2Ai—C1—C2—C3157.8 (7)
O1i—O2B—C1—C2153.6 (3)O1—C1—C2—C3170.2 (3)
C2i—O2B—C1—C243.2 (4)O1i—C1—C2—C372.5 (6)
O1i—O2A—C1—O2B137.3 (19)C2i—C1—C2—C314.7 (3)
C2i—O2A—C1—O2B92.3 (12)C1—C2—C3—C4173.7 (3)
H7Bii—O2A—C1—O2B34.5C2—C3—C4—C5175.7 (3)
O2B—O2A—C1—O2Bi27.1 (13)C3—C4—C5—C4iv174.8 (4)
O1i—O2A—C1—O2Bi110.1 (11)C7iii—N2—C7—N159.7 (2)
C2i—O2A—C1—O2Bi119.5 (5)C8—N2—C7—N157.90 (19)
H7Bii—O2A—C1—O2Bi7.3C9—N1—C7—N259.39 (18)
O2B—O2A—C1—O2Ai67 (2)C7i—N1—C7—N257.0 (2)
O1i—O2A—C1—O2Ai70 (2)C7iii—N2—C8—N2v58.44 (10)
C2i—O2A—C1—O2Ai159.6 (16)C7—N2—C8—N2v58.44 (10)
H7Bii—O2A—C1—O2Ai32.8C7—N1—C9—N1iii58.33 (11)
O2B—O2A—C1—O1111.2 (11)C7i—N1—C9—N1iii58.33 (11)
Symmetry codes: (i) x+1, y, z; (ii) x1/2, y, z1/2; (iii) x, y+1/2, z; (iv) x, y+1, z1; (v) x+1, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N11.34 (4)1.56 (6)2.732 (3)140 (2)
C7—H7B···O2Avi0.972.733.185 (10)110
C7—H7A···O2Bvi0.972.603.240 (8)124
C8—H8B···O2Bvii0.972.413.348 (9)161
C9—H9B···N2ii0.972.763.654 (2)154
C2—H2B···O1viii0.972.783.730 (5)166
Symmetry codes: (ii) x1/2, y, z1/2; (vi) x+1/2, y, z+1/2; (vii) x, y+1/2, z+1; (viii) x+3/2, y, z1/2.
 

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