1,3-Diiodo­azulene

In the structure of 1,3-diiodo­azulene, C₁₀H₆I₂, as expected, the mol­ecule is planar. Also observed are short contacts between I atoms and between I and ring C atoms. The crystal structure of this compound exhibits two sets of parallel layers, nearly perpendicular to each other. The layers are formed by charge-charge inter­actions between some I atoms and nearby seven-membered rings of mol­ecules in an adjacent layer. The packing is also affected by attractive dispersion forces between I atoms in adjacent layers.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.021
• wR factor = 0.055
• Data-to-parameter ratio = 17.5

checkCIF/PLATON results

No syntax errors found



Alert level A
DIFF020_ALERT_1_A  _diffrn_standards_interval_count and
            _diffrn_standards_interval_time are missing. Number of measurements
            between standards or time (min) between standards.
DIFF022_ALERT_1_A  _diffrn_standards_decay_% is missing
            Percentage decrease in standards intensity.

Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.97
PLAT432_ALERT_2_C Short Inter X...Y Contact  I2     ..  C10     ..       3.43 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  I2     ..  C4      ..       3.45 Ang.
PLAT850_ALERT_2_C Check Flack Parameter Exact Value 0.00 and su ..       0.04

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           26.00
           From the CIF: _reflns_number_total               1903
           Count of symmetry unique reflns          969
           Completeness (_total/calc)            196.39%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       934
           Fraction of Friedel pairs measured     0.964
           Are heavy atom types Z>Si present        yes

   2 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL.

1,3-Diiodoazulene

Crystal data

C10H6I2	F(000) = 688
Mr = 379.95	Dx = 2.563 Mg m^−3
Monoclinic, Cc	Melting point: 102 K
Hall symbol: C -2yc	Mo Kα radiation, λ = 0.71073 Å
a = 7.487 (3) Å	Cell parameters from 3884 reflections
b = 23.287 (9) Å	θ = 2.9–26.0°
c = 5.675 (2) Å	µ = 6.33 mm^−1
β = 95.579 (7)°	T = 100 K
V = 984.7 (6) Å^3	Block, black
Z = 4	0.25 × 0.11 × 0.06 mm

Data collection

Bruker APEX diffractometer	1903 independent reflections
Radiation source: fine-focus sealed tube	1896 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.013
ω scans	θmax = 26.0°, θmin = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2002)	h = −9→9
Tmin = 0.301, Tmax = 0.703	k = −25→28
5207 measured reflections	l = −6→6

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.021	H-atom parameters constrained
wR(F^2) = 0.055	w = 1/[σ^2(Fo^2) + (0.044P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max = 0.001
1903 reflections	Δρmax = 0.89 e Å^−3
109 parameters	Δρmin = −0.57 e Å^−3
2 restraints	Absolute structure: Flack (1983), with 935 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (4)

Special details

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. The planar molecule sits obliquely in the unit cell. With the C centering and c-glide systematic absences, the fact that Z = 4, and the fact that the molecule sits obliquely in the unit cell, the best choice for the space group is Cc.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
I1	0.74063 (5)	0.555141 (13)	0.02278 (6)	0.01970 (10)
I2	0.76879 (5)	0.744021 (13)	0.78887 (6)	0.02440 (11)
C1	0.6640 (6)	0.6083 (2)	0.2890 (8)	0.0184 (10)
C2	0.7655 (7)	0.6534 (3)	0.3929 (10)	0.0221 (10)
H2	0.8789	0.6657	0.3499	0.026*
C3	0.6734 (7)	0.6775 (2)	0.5699 (9)	0.0182 (9)
C4	0.3829 (7)	0.6590 (2)	0.7390 (9)	0.0211 (10)
H4	0.4096	0.6901	0.8452	0.025*
C5	0.2200 (8)	0.6310 (2)	0.7632 (11)	0.0248 (12)
H5	0.1540	0.6444	0.8871	0.030*
C6	0.1431 (7)	0.5858 (2)	0.6268 (10)	0.0252 (11)
H6	0.0278	0.5742	0.6652	0.030*
C7	0.2083 (9)	0.5556 (2)	0.4457 (11)	0.0204 (13)
H7	0.1344	0.5250	0.3833	0.025*
C8	0.3682 (7)	0.5634 (2)	0.3396 (9)	0.0181 (10)
H8	0.3853	0.5384	0.2115	0.022*
C9	0.5041 (7)	0.6026 (2)	0.3964 (9)	0.0175 (8)
C10	0.5113 (7)	0.6483 (2)	0.5835 (8)	0.0171 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.02039 (16)	0.02110 (17)	0.01883 (17)	0.00258 (13)	0.00811 (12)	0.00052 (12)
I2	0.0309 (2)	0.02089 (17)	0.02124 (18)	−0.00535 (15)	0.00181 (14)	−0.00196 (15)
C1	0.019 (2)	0.019 (2)	0.018 (2)	0.0048 (19)	0.0059 (18)	0.0030 (18)
C2	0.015 (2)	0.027 (3)	0.025 (3)	−0.0006 (19)	0.004 (2)	0.006 (2)
C3	0.021 (2)	0.016 (2)	0.017 (2)	−0.0034 (19)	−0.0031 (18)	0.0023 (18)
C4	0.025 (3)	0.019 (3)	0.020 (2)	0.003 (2)	0.004 (2)	0.0048 (19)
C5	0.020 (3)	0.026 (3)	0.030 (3)	0.006 (2)	0.012 (2)	0.008 (2)
C6	0.020 (3)	0.030 (3)	0.027 (3)	0.005 (2)	0.009 (2)	0.003 (2)
C7	0.022 (3)	0.015 (3)	0.024 (3)	−0.0001 (19)	0.001 (2)	−0.0006 (18)
C8	0.020 (3)	0.016 (2)	0.018 (2)	0.0012 (18)	0.003 (2)	0.0018 (18)
C9	0.0158 (19)	0.019 (2)	0.018 (2)	0.0048 (16)	0.0015 (16)	0.0017 (16)
C10	0.023 (2)	0.014 (2)	0.014 (2)	0.0035 (18)	−0.001 (2)	0.0033 (16)

Geometric parameters (Å, º)

I1—C1	2.076 (5)	C5—C6	1.397 (8)
I2—C3	2.069 (5)	C5—H5	0.9500
C1—C2	1.395 (8)	C6—C7	1.374 (8)
C1—C9	1.401 (7)	C6—H6	0.9500
C2—C3	1.390 (8)	C7—C8	1.403 (8)
C2—H2	0.9500	C7—H7	0.9500
C3—C10	1.400 (7)	C8—C9	1.381 (7)
C4—C10	1.389 (7)	C8—H8	0.9500
C4—C5	1.401 (8)	C9—C10	1.501 (7)
C4—H4	0.9500
C2—C1—C9	109.9 (4)	C7—C6—C5	130.0 (5)
C2—C1—I1	125.4 (4)	C7—C6—H6	115.0
C9—C1—I1	124.6 (4)	C5—C6—H6	115.0
C3—C2—C1	108.8 (4)	C6—C7—C8	129.4 (5)
C3—C2—H2	125.6	C6—C7—H7	115.3
C1—C2—H2	125.6	C8—C7—H7	115.3
C2—C3—C10	109.7 (4)	C9—C8—C7	128.7 (5)
C2—C3—I2	124.7 (4)	C9—C8—H8	115.7
C10—C3—I2	125.5 (4)	C7—C8—H8	115.7
C10—C4—C5	129.9 (5)	C8—C9—C1	127.0 (5)
C10—C4—H4	115.1	C8—C9—C10	127.5 (5)
C5—C4—H4	115.1	C1—C9—C10	105.5 (5)
C6—C5—C4	127.7 (6)	C4—C10—C3	127.2 (5)
C6—C5—H5	116.1	C4—C10—C9	126.7 (5)
C4—C5—H5	116.1	C3—C10—C9	106.1 (4)
C9—C1—C2—C3	0.3 (6)	C2—C1—C9—C10	−0.6 (6)
I1—C1—C2—C3	−177.7 (4)	I1—C1—C9—C10	177.5 (3)
C1—C2—C3—C10	0.1 (6)	C5—C4—C10—C3	−179.1 (5)
C1—C2—C3—I2	177.5 (3)	C5—C4—C10—C9	0.5 (9)
C10—C4—C5—C6	−2.7 (10)	C2—C3—C10—C4	179.3 (5)
C4—C5—C6—C7	3.6 (10)	I2—C3—C10—C4	1.9 (7)
C5—C6—C7—C8	−3.1 (10)	C2—C3—C10—C9	−0.4 (6)
C6—C7—C8—C9	2.4 (10)	I2—C3—C10—C9	−177.8 (3)
C7—C8—C9—C1	178.6 (5)	C8—C9—C10—C4	1.4 (8)
C7—C8—C9—C10	−2.1 (9)	C1—C9—C10—C4	−179.1 (5)
C2—C1—C9—C8	178.9 (5)	C8—C9—C10—C3	−178.9 (5)
I1—C1—C9—C8	−3.0 (8)	C1—C9—C10—C3	0.6 (5)