Crystal structure and photoreactivity of a halogen-bonded cocrystal based upon 1,2-di­iodo­perchloro­benzene and 1,2-bis­(pyridin-4-yl)ethyl­ene

The formation of a photoreactive cocrystal based upon 1,2-di­iodo­perchloro­benzene (1,2-C₆I₂Cl₄) and trans-1,2-bis­(pyridin-4-yl)ethyl­ene (BPE) has been achieved. The resulting cocrystal, 2(1,2-C₆I₂Cl₄)·(BPE) or C₆Cl₄I₂·0.5C₁₂H₁₀N₂, com­prises planar sheets of the com­ponents held together by the combination of I...N halogen bonds and halogen–halogen contacts. Notably, the 1,2-C₆I₂Cl₄ mol­ecules π-stack in a homogeneous and face-to-face orientation that results in an infinite column of the halogen-bond donor. As a consequence of this stacking arrangement and I...N halogen bonds, mol­ecules of BPE also stack in this type of pattern. In particular, neighbouring ethyl­ene groups in BPE are found to be parallel and within the accepted distance for a photoreaction. Upon exposure to ultraviolet light, the cocrystal undergoes a solid-state [2 + 2] cyclo­addition reaction that produces rctt-tetra­kis­(pyridin-4-yl)cyclo­butane (TPCB) with an overall yield of 89%. A solvent-free approach utilizing dry vortex grinding of the com­ponents also resulted in a photoreactive material with a similar yield.

Computing details

Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT2018 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: SHELXTL (Bruker, 2016) and X-SEED (Barbour, 2001); software used to prepare material for publication: SHELXTL (Bruker, 2016).

1,2-Diiodo-3,4,5,6-chlorobenzene–trans-1,2-bis(pyridin-4-yl)ethylene (2/1)

Crystal data

C6Cl4I2·0.5C12H10N2	Z = 2
Mr = 558.77	F(000) = 516
Triclinic, P1	Dx = 2.419 Mg m^−3
a = 4.1177 (13) Å	Mo Kα radiation, λ = 0.71073 Å
b = 13.502 (4) Å	Cell parameters from 5904 reflections
c = 14.151 (4) Å	θ = 2.3–27.5°
α = 78.864 (12)°	µ = 4.78 mm^−1
β = 83.719 (12)°	T = 290 K
γ = 87.935 (12)°	Rod, yellow
V = 767.2 (4) Å^3	0.15 × 0.08 × 0.05 mm

Data collection

Bruker SMART APEX CCD area detector diffractometer	3508 independent reflections
Radiation source: sealed tube	2928 reflections with I > 2σ(I)
Detector resolution: 8 pixels mm^-1	Rint = 0.031
ω and φ scans	θmax = 27.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2016)	h = −5→5
Tmin = 0.783, Tmax = 1.000	k = −17→17
11912 measured reflections	l = −18→18

Refinement

Refinement on F^2	4 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.029	H-atom parameters constrained
wR(F^2) = 0.065	w = 1/[σ^2(Fo^2) + (0.0213P)^2 + 0.601P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.002
3508 reflections	Δρmax = 0.72 e Å^−3
191 parameters	Δρmin = −0.58 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. A single crystal of 2(1,2-C₆I₂Cl₄).(BPE) was mounted on a MiTeGen cryoloop in a random orientation for X-ray data collection. A Bruker Venture Duo Photon-II single-crystal X-ray diffractometer equipped with an Oxford Cryostream device was used for the data collection. APEXII and SAINT software packages (Bruker, 2016) were used for data collection and integration, respectively. The data were corrected for systematic errors using SADABS based on the Laue symmetry using equivalent reflections. The structure was solved by dual space methods using SHELXT-2018 (Sheldrick, 2015a) and refined against F² using SHELXL-2018 (Sheldrick, 2015b). The program X-Seed was used as a graphical interface (Barbour, 2001).

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
I1	0.24195 (6)	0.26852 (2)	0.51627 (2)	0.04165 (9)
Cl1	0.5409 (3)	0.54003 (8)	0.15189 (8)	0.0619 (3)
Cl2	0.9278 (3)	0.37431 (9)	0.06306 (7)	0.0645 (3)
I2	0.2089 (4)	0.51541 (16)	0.37413 (14)	0.0477 (2)	0.5895 (13)
Cl3	0.9897 (3)	0.15892 (8)	0.18345 (8)	0.0581 (3)
Cl4	0.658 (2)	0.1062 (4)	0.3924 (6)	0.0592 (14)	0.5895 (13)
N1	−0.0686 (8)	0.2054 (2)	0.7094 (2)	0.0477 (8)
C7	0.4609 (8)	0.3024 (2)	0.3720 (2)	0.0333 (7)
C8	0.4379 (8)	0.3997 (2)	0.3175 (2)	0.0347 (7)
C12	0.6292 (8)	0.2279 (2)	0.3300 (2)	0.0358 (7)
C11	0.7737 (8)	0.2506 (3)	0.2351 (3)	0.0385 (8)
C9	0.5790 (9)	0.4211 (3)	0.2214 (3)	0.0403 (8)
C10	0.7492 (9)	0.3466 (3)	0.1810 (3)	0.0416 (8)
C2	−0.2387 (9)	0.1216 (3)	0.7194 (3)	0.0457 (9)
H2	−0.275618	0.098770	0.663601	0.055*
C1	−0.3637 (9)	0.0665 (3)	0.8074 (3)	0.0415 (8)
H1	−0.484620	0.008961	0.810271	0.050*
C4	−0.1303 (10)	0.1856 (3)	0.8812 (3)	0.0484 (9)
H4	−0.087602	0.210442	0.935376	0.058*
C5	−0.3065 (9)	0.0981 (3)	0.8920 (3)	0.0400 (8)
C3	−0.0176 (10)	0.2361 (3)	0.7893 (3)	0.0510 (10)
H3	0.100320	0.294730	0.783742	0.061*
C6	−0.4232 (9)	0.0435 (3)	0.9892 (3)	0.0450 (9)
H6	−0.384953	0.073143	1.040995	0.054*
Cl4A	0.244 (3)	0.4982 (9)	0.3684 (9)	0.075 (3)	0.4105 (13)
I2A	0.6649 (7)	0.08069 (16)	0.4059 (2)	0.0485 (4)	0.4105 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.04061 (14)	0.05105 (15)	0.03022 (13)	−0.00472 (10)	0.00041 (9)	−0.00170 (10)
Cl1	0.0889 (8)	0.0433 (5)	0.0455 (6)	−0.0013 (5)	−0.0026 (5)	0.0088 (4)
Cl2	0.0877 (8)	0.0682 (7)	0.0331 (5)	−0.0121 (6)	0.0149 (5)	−0.0081 (5)
I2	0.0535 (5)	0.0474 (5)	0.0425 (4)	0.0125 (5)	−0.0025 (4)	−0.0128 (3)
Cl3	0.0621 (6)	0.0582 (6)	0.0582 (6)	0.0053 (5)	0.0033 (5)	−0.0277 (5)
Cl4	0.0847 (19)	0.029 (2)	0.057 (2)	0.0114 (19)	−0.0050 (15)	0.0052 (17)
N1	0.0558 (19)	0.0425 (17)	0.0384 (18)	−0.0010 (14)	0.0027 (15)	0.0038 (14)
C7	0.0318 (16)	0.0427 (18)	0.0249 (16)	−0.0064 (13)	−0.0022 (13)	−0.0046 (13)
C8	0.0361 (17)	0.0366 (17)	0.0329 (18)	−0.0028 (13)	−0.0070 (14)	−0.0082 (14)
C12	0.0363 (17)	0.0356 (17)	0.0349 (18)	−0.0038 (13)	−0.0067 (14)	−0.0033 (14)
C11	0.0363 (18)	0.0428 (19)	0.039 (2)	−0.0047 (14)	−0.0026 (15)	−0.0153 (15)
C9	0.047 (2)	0.0399 (19)	0.0316 (18)	−0.0083 (15)	−0.0061 (16)	0.0005 (14)
C10	0.044 (2)	0.049 (2)	0.0317 (19)	−0.0094 (16)	0.0006 (16)	−0.0082 (16)
C2	0.059 (2)	0.050 (2)	0.0276 (18)	0.0062 (18)	−0.0047 (17)	−0.0057 (15)
C1	0.048 (2)	0.0381 (18)	0.036 (2)	−0.0018 (15)	−0.0018 (16)	−0.0031 (15)
C4	0.065 (2)	0.045 (2)	0.036 (2)	−0.0046 (18)	−0.0043 (18)	−0.0091 (16)
C5	0.0452 (19)	0.0411 (19)	0.0314 (18)	0.0047 (15)	−0.0022 (15)	−0.0034 (15)
C3	0.062 (3)	0.041 (2)	0.047 (2)	−0.0095 (18)	−0.002 (2)	−0.0026 (17)
C6	0.056 (2)	0.046 (2)	0.0309 (19)	0.0017 (16)	−0.0017 (17)	−0.0039 (16)
Cl4A	0.083 (4)	0.070 (5)	0.061 (4)	0.035 (3)	0.015 (2)	−0.007 (3)
I2A	0.0628 (6)	0.0329 (10)	0.0472 (8)	0.0021 (7)	−0.0074 (5)	−0.0007 (7)

Geometric parameters (Å, º)

I1—C7	2.110 (3)	C11—C10	1.378 (5)
Cl1—C9	1.726 (4)	C9—C10	1.384 (5)
Cl2—C10	1.725 (4)	C2—C1	1.379 (5)
I2—C8	2.046 (4)	C2—H2	0.9300
Cl3—C11	1.728 (4)	C1—C5	1.391 (5)
Cl4—C12	1.716 (6)	C1—H1	0.9300
N1—C3	1.316 (5)	C4—C5	1.383 (5)
N1—C2	1.328 (5)	C4—C3	1.385 (5)
C7—C12	1.392 (5)	C4—H4	0.9300
C7—C8	1.395 (5)	C5—C6	1.469 (5)
C8—C9	1.398 (5)	C3—H3	0.9300
C8—Cl4A	1.758 (11)	C6—C6^i	1.320 (7)
C12—C11	1.390 (5)	C6—H6	0.9300
C12—I2A	2.077 (4)
C3—N1—C2	117.0 (3)	C11—C10—Cl2	120.5 (3)
C12—C7—C8	119.1 (3)	C9—C10—Cl2	119.8 (3)
C12—C7—I1	120.5 (2)	N1—C2—C1	123.9 (4)
C8—C7—I1	120.4 (2)	N1—C2—H2	118.0
C7—C8—C9	120.0 (3)	C1—C2—H2	118.0
C7—C8—Cl4A	121.1 (5)	C2—C1—C5	119.1 (3)
C9—C8—Cl4A	118.8 (5)	C2—C1—H1	120.4
C7—C8—I2	122.1 (3)	C5—C1—H1	120.4
C9—C8—I2	117.9 (3)	C5—C4—C3	119.7 (4)
C11—C12—C7	120.2 (3)	C5—C4—H4	120.1
C11—C12—Cl4	118.4 (4)	C3—C4—H4	120.1
C7—C12—Cl4	121.3 (4)	C4—C5—C1	116.7 (3)
C11—C12—I2A	118.5 (3)	C4—C5—C6	120.1 (3)
C7—C12—I2A	121.2 (3)	C1—C5—C6	123.3 (3)
C10—C11—C12	120.6 (3)	N1—C3—C4	123.5 (4)
C10—C11—Cl3	119.0 (3)	N1—C3—H3	118.3
C12—C11—Cl3	120.3 (3)	C4—C3—H3	118.3
C10—C9—C8	120.2 (3)	C6^i—C6—C5	126.7 (5)
C10—C9—Cl1	119.3 (3)	C6^i—C6—H6	116.6
C8—C9—Cl1	120.5 (3)	C5—C6—H6	116.6
C11—C10—C9	119.7 (3)

Symmetry code: (i) −x−1, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···I2A^ii	0.93	3.31	4.072 (5)	141

Symmetry code: (ii) −x, −y, −z+1.