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X-ray structure studies have been carried out on single crystals of 4,4′-dichlorobenzophenone at temperatures from 164 to 295 K. The structure determined at 164 K is monoclinic I2/c. Crystal data: T = 164 K; a = 24.527 (6), b = 6.064 (1), c = 7.457 (4) Å; β = 100.10 (2)°; V = 1091.9 (6) Å3; Z = 4; d_{c} = 1.528 g cm^{-3}; \lambda(Mo K{\alpha}) = 0.71073 \AA; \mu = 0.565 mm^{-1}; F(000) = 512; R = 0.04. The temperature dependence of the unit-cell parameters and of the intensities of some symmetry-sensitive reflections has been measured over the range 164–293 K, both in warm-up and cool-down experiments. It has been established that the phase transformation between the C2/c and I2/c structures occurs as a sequence of two closely spaced first-order phase transitions. In between these phase transitions the crystal is in an intermediate state whose structure is different from both C2/c and I2/­c. The experimental data give us ground to suppose that the intermediate state is disordered, having a primitive cell half as large as in the two ordered phases. Within the temperature interval where the said intermediate state exists the thermal expansivity along axis c is negative.

Supporting information

cif

Crystallographic Information File (CIF)
Contains datablocks bnz_ltw, I

fcf

Structure factor file (CIF format)
Contains datablock I

CCDC reference: 136449

Computing details top

Data collection: Recentering 2T/T (Operations Manual SYTENX P21; Cupertino, 1973); cell refinement: Least-Squares Orientation Matrix Program (Cupertino, 1973); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993); molecular graphics: SHELXL93 (Sheldrick, 1993).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
4,4'-dichlorobenzophenone top
Crystal data top
C13H8Cl2OF(000) = 512
Mr = 251.09Dx = 1.527 Mg m3
Monoclinic, I2/cMo Kα radiation, λ = 0.71073 Å
a = 24.527 (6) ÅCell parameters from 15 reflections
b = 6.064 (1) Åθ = 15–16°
c = 7.457 (4) ŵ = 0.57 mm1
β = 100.10 (2)°T = 164 K
V = 1091.9 (7) Å3Plate, transparent
Z = 40.50 × 0.50 × 0.30 mm
Data collection top
SYNTEX P21
diffractometer
Rint = 0.116
Radiation source: fine-focus sealed tubeθmax = 25.1°, θmin = 3.4°
Graphite monochromatorh = 029
ω–2θ scansk = 17
1025 measured reflectionsl = 88
945 independent reflections3 standard reflections every 97 reflections
842 reflections with F > 4σ(F) intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.040Isotropic
wR(F2) = 0.145Calculated w = 1/[σ2(Fo2) + (0.0457P)2 + 2.5539P]
where P = (Fo2 + 2Fc2)/3
S = 1.19(Δ/σ)max < 0.001
898 reflectionsΔρmax = 0.33 e Å3
91 parametersΔρmin = 0.32 e Å3
0 restraintsExtinction correction: SHELXL93 (Sheldrick, 1993), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0040 (13)
Crystal data top
C13H8Cl2OV = 1091.9 (7) Å3
Mr = 251.09Z = 4
Monoclinic, I2/cMo Kα radiation
a = 24.527 (6) ŵ = 0.57 mm1
b = 6.064 (1) ÅT = 164 K
c = 7.457 (4) Å0.50 × 0.50 × 0.30 mm
β = 100.10 (2)°
Data collection top
SYNTEX P21
diffractometer
Rint = 0.116
1025 measured reflections3 standard reflections every 97 reflections
945 independent reflections intensity decay: none
842 reflections with F > 4σ(F)
Refinement top
R[F2 > 2σ(F2)] = 0.0400 restraints
wR(F2) = 0.145Isotropic
S = 1.19Δρmax = 0.33 e Å3
898 reflectionsΔρmin = 0.32 e Å3
91 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 on F2 for ALL reflections except for 47 with very negative F2 or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The observed criterio of F2 > 2sigma(F2) is used only for calculating _R_factor_obs etc. and 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
Cl0.21473 (3)0.50763 (12)0.79785 (10)0.0386 (3)
C10.05324 (10)0.1400 (4)0.7610 (3)0.0215 (6)
C20.05524 (11)0.3485 (4)0.6832 (3)0.0232 (6)
C30.10497 (11)0.4589 (4)0.6909 (3)0.0256 (6)
C40.15300 (11)0.3594 (4)0.7796 (3)0.0254 (6)
C50.15266 (11)0.1522 (5)0.8563 (3)0.0268 (6)
C60.10284 (11)0.0428 (4)0.8460 (3)0.0245 (6)
C70.00000.0162 (5)0.75000.0236 (8)
O0.00000.1838 (4)0.75000.0389 (8)
H20.0227 (12)0.416 (5)0.621 (4)0.028 (7)*
H30.1061 (12)0.590 (5)0.640 (4)0.028 (7)*
H50.1866 (13)0.103 (5)0.921 (4)0.034 (8)*
H60.1003 (12)0.103 (6)0.901 (4)0.033 (8)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl0.0284 (5)0.0454 (5)0.0419 (5)0.0131 (3)0.0055 (3)0.0010 (3)
C10.0225 (13)0.0191 (12)0.0230 (12)0.0018 (9)0.0044 (10)0.0022 (9)
C20.0256 (13)0.0206 (13)0.0227 (13)0.0018 (10)0.0024 (10)0.0009 (10)
C30.0325 (15)0.0194 (13)0.0258 (13)0.0043 (11)0.0074 (10)0.0001 (10)
C40.0258 (13)0.0272 (13)0.0237 (13)0.0066 (11)0.0061 (10)0.0058 (10)
C50.0221 (13)0.0312 (14)0.0261 (13)0.0056 (11)0.0018 (11)0.0033 (11)
C60.0282 (14)0.0212 (13)0.0238 (12)0.0035 (10)0.0037 (10)0.0045 (10)
C70.027 (2)0.016 (2)0.026 (2)0.0000.0015 (15)0.000
O0.0308 (15)0.0150 (13)0.068 (2)0.0000.0017 (14)0.000
Geometric parameters (Å, º) top
Cl—C41.746 (3)C3—H30.88 (3)
C1—C21.396 (4)C4—C51.381 (4)
C1—C61.400 (3)C5—C61.381 (4)
C1—C71.496 (3)C5—H50.93 (3)
C2—C31.384 (4)C6—H60.98 (3)
C2—H20.94 (3)C7—O1.213 (4)
C3—C41.384 (4)C7—C1i1.496 (3)
C2—C1—C6118.6 (2)C3—C4—Cl117.8 (2)
C2—C1—C7121.7 (2)C6—C5—C4118.9 (2)
C6—C1—C7119.6 (2)C6—C5—H5125 (2)
C3—C2—C1121.1 (2)C4—C5—H5116 (2)
C3—C2—H2118.2 (19)C5—C6—C1120.9 (2)
C1—C2—H2120.7 (19)C5—C6—H6122.0 (17)
C2—C3—C4118.6 (2)C1—C6—H6117.1 (17)
C2—C3—H3120.7 (19)O—C7—C1120.11 (14)
C4—C3—H3120.6 (19)O—C7—C1i120.11 (15)
C5—C4—C3121.9 (2)C1—C7—C1i119.8 (3)
C5—C4—Cl120.3 (2)
C6—C1—C2—C30.6 (4)C4—C5—C6—C10.6 (4)
C7—C1—C2—C3178.5 (2)C2—C1—C6—C51.3 (4)
C1—C2—C3—C40.8 (4)C7—C1—C6—C5179.3 (2)
C2—C3—C4—C51.5 (4)C2—C1—C7—O150.8 (2)
C2—C3—C4—Cl176.7 (2)C6—C1—C7—O27.1 (2)
C3—C4—C5—C60.8 (4)C2—C1—C7—C1i29.2 (2)
Cl—C4—C5—C6177.4 (2)C6—C1—C7—C1i152.9 (2)
Symmetry code: (i) x, y, z+3/2.

Experimental details

Crystal data
Chemical formulaC13H8Cl2O
Mr251.09
Crystal system, space groupMonoclinic, I2/c
Temperature (K)164
a, b, c (Å)24.527 (6), 6.064 (1), 7.457 (4)
β (°) 100.10 (2)
V3)1091.9 (7)
Z4
Radiation typeMo Kα
µ (mm1)0.57
Crystal size (mm)0.50 × 0.50 × 0.30
Data collection
DiffractometerSYNTEX P21
diffractometer
Absorption correction
No. of measured, independent and
observed [F > 4σ(F)] reflections
1025, 945, 842
Rint0.116
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.145, 1.19
No. of reflections898
No. of parameters91
H-atom treatmentIsotropic
Δρmax, Δρmin (e Å3)0.33, 0.32

Computer programs: Recentering 2T/T (Operations Manual SYTENX P21; Cupertino, 1973), Least-Squares Orientation Matrix Program (Cupertino, 1973), SHELXS86 (Sheldrick, 1990), SHELXL93 (Sheldrick, 1993).

Selected bond lengths (Å) top
Cl—C41.746 (3)
 
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