Co-crystal sustained by π-type halogen-bonding inter­actions between 1,4-di­iodo­perchloro­benzene and naphthalene

The formation of a co-crystal sustained by π-type halogen bonds involving 1,4-di­iodo­perchloro­benzene and naphthalene is reported.

Abstract

The formation and crystal structure of a co-crystal based upon 1,4-di­iodo­perchloro­benzene (C₆I₂Cl₄) as the halogen-bond donor along with naphthalene (nap) as the acceptor is reported. The co-crystal [systematic name: 1,2,4,5-tetra­chloro-3,6-di­iodo­benzene–naphthalene, (C₆I₂Cl₄)·(nap)] generates a chevron-like structure that is held together primarily by π-type halogen bonds (i.e. C—I⋯π contacts) between the components. In addition, C₆I₂Cl₄ also inter­acts with the acceptor via C—Cl⋯π contacts that help stabilize the co-crystal. Within the solid, both aromatic components are found to engage in offset and homogeneous face-to-face π–π stacking inter­actions. Lastly, the halogen-bond donor C₆I₂Cl₄ is found to engage with neighboring donors by both Type I chlorine–chlorine and Type II iodine–chlorine contacts, which generates an extended structure.

1. Chemical context

Halogen bonding continues to be a highly utilized non-covalent inter­action in the formation of multicomponent mol­ecular solids such as co-crystals. Halogen bonding is an attractive inter­action between an electrophilic region on a halogen atom and a nucleophilic region on a second atom (Gilday et al., 2015 ▸). This electrophilic or positive region, namely the σ-hole, is located at the tip of a halogen atom bound to a carbon that inter­acts with a lone pair on an atom or an electron-rich aromatic surface (Cavallo et al., 2016 ▸). In general, iodine generates the largest positive σ-hole when combined with neighboring electronegative atoms such as fluorine. The majority of these reported halogen bonds are classified as n-type meaning that the halogen atom is inter­acting with a lone pair such as on an N or O atom (Walsh et al., 2001 ▸). A lesser investigated class of halogen bonds are π-type (i.e. C—I⋯π contacts) where the halogen atom inter­acts with an electron-rich surface such as a polycyclic aromatic hydro­carbon (Vainauskas et al., 2020 ▸; d’Agostino et al., 2015 ▸; Shen et al., 2012 ▸).

A continued goal within our research groups has been in the design and formation of halogen-bonded co-crystals based upon 1,4-di­iodo­perchloro­benzene (C₆I₂Cl₄) as the donor. Recently, we reported the formation of photoreactive co-crystals based upon C₆I₂Cl₄ along with trans-1,2-bis­(pyridine-4-yl)ethyl­ene (Bosch et al., 2019b ▸) and 4-stilbazole (Bosch et al., 2019c ▸) that are held together by primarily C—I⋯N or n-type halogen bonds. With the goal of expanding the type of halogen bonds that C₆I₂Cl₄ can form in mol­ecular co-crystals, a study with a polycyclic aromatic was undertaken. Herein, we report the solid-state crystal structure of a co-crystal held together primarily by π-type halogen bonds between C₆I₂Cl₄ and naphthalene (nap) resulting in a chevron-like structure. In addition to the π-type halogen bond, the co-crystal (C₆I₂Cl₄)·(nap) is also held together by the combination of C—Cl⋯π contacts, homogeneous face-to-face π–π stacking inter­actions, Type I chlorine–chlorine contacts, and Type II iodine–chlorine contacts.

2. Structural commentary

Crystallographic analysis reveals that (C₆I₂Cl₄)·(nap) crystallizes in the centrosymmetric triclinic space group Pī. The asymmetric unit contains half a mol­ecule of both C₆I₂Cl₄ and nap where inversion symmetry generates the remainder of each mol­ecule (Fig. 1 ▸). The co-crystal is sustained by π-type or C—I⋯π halogen bonds with a distance of 3.373 (1) Å along with a nearly perpendicular halogen-bond angle of 90.99 (4)° (Fig. 2 ▸). This halogen-bond distance and angle were determined by using the I atom on C₆I₂Cl₄ and the calculated plane for the nap mol­ecule. As expected, C₆I₂Cl₄ forms two π-type halogen bonds with two different nap mol­ecules, generating a chevron-like pattern (Fig. 2 ▸).

Figure 1.

The labeled asymmetric unit of (C₆I₂Cl₄)·(nap). Displacement ellipsoids are drawn at the 50% probability level for non-hydrogen atoms while hydrogen atoms are shown as spheres of arbitrary size.

Figure 2.

X-ray crystal structure of (C₆I₂Cl₄)·(nap) illustrating the chevron-like packing pattern along with π-type halogen bonds. In addition, the Type I chlorine–chlorine and Type II iodine–chlorine inter­actions between neighboring chevron-based chains are also shown.

3. Supra­molecular features

In addition to π-type halogen bond within (C₆I₂Cl₄)·(nap), the donor C₆I₂Cl₄ is found to engage in Type I chlorine–chlorine contacts (Fig. 3 ▸). These inter­actions are found between crystallographically equivalent Cl atoms, namely Cl2⋯Cl2ⁱ [symmetry code: (i) 1 − x, -y, 1 − z], with a distance of 3.499 (1) Å and a C—Cl⋯Cl bond angle of θ₁ = θ₂ = 132.16 (6)° (Mukherjee et al., 2014 ▸; Desiraju & Parthasarathy, 1989 ▸). In addition, neighboring donors also inter­act via Type II iodine–chlorine contacts. This inter­action is found between I1⋯Cl2ⁱ [symmetry code: (i) 1 − x, -y, 1 − z], with a distance of 3.808 (1) Å and a C—I⋯Cl bond angle of 111.83 (4)°. Both the aromatic halogen-bond donor and acceptor are found to engage in an offset and homogeneous face-to-face π–π stacking arrangement that stabilizes the co-crystal (Fig. 3 ▸). Lastly, C₆I₂Cl₄ is inter­acting with two additional nap mol­ecules via C—Cl⋯π contacts at a distance of 3.391 (2) Å measured for Cl1⋯C5.

Figure 3.

X-ray crystal structure of (C₆I₂Cl₄)·(nap) illustrating the π-type halogen bonds and the offset face-to-face stacking of both the halogen-bond donor and acceptor.

These various non-covalent inter­actions were also investigated and visualized by utilizing a Hirshfeld surface analysis (Spackman et al., 2021 ▸) where d _norm is mapped onto the calculated surface (Fig. 4 ▸). The darkest red spots on the Hirshfeld surface represents the shortest van der Waals contacts where the π-type halogen bond is located. In addition, the faint red spots indicate separations less than the sum of the van der Waals radii for the C—Cl⋯π contacts. Lastly, dashed lines illustrate the Type I chlorine–chlorine inter­actions observed within (C₆I₂Cl₄)·(nap). This Hirshfeld surface analysis along with the observed bond lengths confirms the ability of C₆I₂Cl₄ to engage in π-type halogen bonds to a polycyclic aromatic hydro­carbon, namely nap.

Figure 4.

Hirshfeld surface of (C₆I₂Cl₄)·(nap) where d _norm is mapped onto the surface illustrating the π-type halogen bonds (darkest red spots) and C—Cl⋯π contacts (faint red spots). Lastly, the Type I chlorine–chlorine inter­actions are shown with green dashed lines.

4. Database survey

A search of the Cambridge Crystallographic Database (Version 2023.2.0 Build 3382240; Groom et al., 2016 ▸) using Conquest (Bruno et al., 2002 ▸) for structures containing 1,4-di­iodo­perchloro­benzene (C₆I₂Cl₄) in which the I atom is within the van der Waals radius of an aromatic surface revealed only one structure, refcode HONBIY (Bosch, 2019a ▸). In particular, this multicomponent solid is a monosolvate of benzene where C₆I₂Cl₄ forms two π-type halogen bonds, generating a similar chevron-like pattern observed in (C₆I₂Cl₄)·(nap).

5. Synthesis and crystallization

Materials and general methods

The solvent toluene along with the halogen-bond acceptor naphthalene (nap) were both purchased from Sigma-Aldrich Chemical (St. Louis, MO, USA) and used without any additional purification. The halogen-bond donor 1,4-di­iodo­perchloro­benzene (C₆I₂Cl₄) was synthesized utilizing a previously published method (Reddy et al., 2006 ▸).

Synthesis and crystallization

The formation of (C₆I₂Cl₄)·(nap) was achieved by dissolving 50.0 mg of C₆I₂Cl₄ in 2.0 mL of toluene and then combined with a 2.0 mL toluene solution containing 13.7 mg of nap (1:1 molar equivalent). Within two days, single crystals suitable for X-ray diffraction were formed upon loss of some of the solvent by slow evaporation.

6. Refinement

Crystal data, data collection, and structure refinement details are summarized in Table 1 ▸. Intensity data were corrected for Lorentz, polarization, and background effects using APEX4 (Bruker, 2021 ▸). Hydrogen atoms bound to carbon atoms were located in the difference Fourier map and were geometrically constrained using the appropriate AFIX commands.

Table 1. Experimental details.

Crystal data
Chemical formula	C6Cl4I2·C10H8
M r	595.82
Crystal system, space group	Triclinic, P
Temperature (K)	100
a, b, c (Å)	5.4830 (7), 6.4533 (11), 12.171 (2)
α, β, γ (°)	87.274 (5), 85.912 (5), 82.629 (9)
V (Å3)	425.68 (12)
Z	1
Radiation type	Mo Kα
μ (mm−1)	4.31
Crystal size (mm)	0.14 × 0.12 × 0.10
Data collection
Diffractometer	Bruker D8 Venture Duo with Photon III
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 ▸)
T min, T max	0.626, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	30681, 2518, 2465
R int	0.050
(sin θ/λ)max (Å−1)	0.717
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.017, 0.038, 1.09
No. of reflections	2518
No. of parameters	100
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.77, −0.47

Computer programs: APEX4 (Bruker, 2021 ▸), SAINT (Bruker, 2016 ▸), SHELXT2018/2 (Sheldrick, 2015a ▸), SHELXL (Sheldrick, 2015b ▸), and OLEX2 (Dolomanov et al., 2009 ▸).

Supplementary Material

CCDC reference: 2291675

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

C6Cl4I2·C10H8	Z = 1
Mr = 595.82	F(000) = 278
Triclinic, P1	Dx = 2.324 Mg m−3
a = 5.4830 (7) Å	Mo Kα radiation, λ = 0.71073 Å
b = 6.4533 (11) Å	Cell parameters from 9944 reflections
c = 12.171 (2) Å	θ = 3.2–30.6°
α = 87.274 (5)°	µ = 4.31 mm−1
β = 85.912 (5)°	T = 100 K
γ = 82.629 (9)°	Irregular, clear colourless
V = 425.68 (12) Å3	0.14 × 0.12 × 0.10 mm

Data collection

Bruker D8 Venture Duo with Photon III diffractometer	2465 reflections with I > 2σ(I)
phi and ω scans	Rint = 0.050
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θmax = 30.7°, θmin = 3.2°
Tmin = 0.626, Tmax = 0.746	h = −7→7
30681 measured reflections	k = −9→9
2518 independent reflections	l = −17→17

Refinement

Refinement on F2	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.017	H-atom parameters constrained
wR(F2) = 0.038	w = 1/[σ2(Fo2) + 0.4448P] where P = (Fo2 + 2Fc2)/3
S = 1.09	(Δ/σ)max = 0.001
2518 reflections	Δρmax = 0.77 e Å−3
100 parameters	Δρmin = −0.47 e Å−3
0 restraints

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 numerical absorption correction was applied based on a Gaussian integration over a multifaceted crystal and followed by a semi-empirical correction for adsorption applied using SADABS (Bruker, 2016). The program SHELXT (Sheldrick, 2015a) was used for the initial structure solution and SHELXL (Sheldrick, 2015b) was used for the refinement of the structure. Both programs were utilized within the OLEX2 software (Dolomanov et al., 2009).

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

	x	y	z	Uiso*/Ueq
I1	0.56547 (2)	0.30084 (2)	0.68774 (2)	0.01552 (4)
Cl1	0.87192 (8)	0.70258 (6)	0.72721 (3)	0.01816 (8)
Cl2	0.73398 (7)	0.12959 (6)	0.43367 (3)	0.01748 (8)
C1	0.8224 (3)	0.4211 (2)	0.57480 (12)	0.0125 (3)
C2	0.9407 (3)	0.5897 (2)	0.60178 (12)	0.0130 (3)
C3	0.8824 (3)	0.3322 (2)	0.47217 (12)	0.0127 (3)
C4	0.5015 (3)	0.0935 (3)	1.02907 (13)	0.0161 (3)
C5	0.3321 (3)	0.2714 (3)	1.00359 (14)	0.0187 (3)
H5	0.333552	0.396640	1.041387	0.022*
C6	0.1657 (3)	0.2649 (3)	0.92489 (15)	0.0214 (3)
H6	0.053127	0.385222	0.908670	0.026*
C7	0.1621 (3)	0.0800 (3)	0.86822 (14)	0.0209 (3)
H7	0.046094	0.076467	0.814172	0.025*
C8	0.3245 (3)	−0.0955 (3)	0.89020 (14)	0.0189 (3)
H8	0.320044	−0.218777	0.851101	0.023*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
I1	0.01377 (6)	0.01772 (6)	0.01506 (6)	−0.00420 (4)	0.00031 (3)	0.00367 (3)
Cl1	0.02229 (18)	0.01951 (17)	0.01340 (16)	−0.00507 (14)	0.00101 (13)	−0.00473 (13)
Cl2	0.01990 (17)	0.01571 (16)	0.01881 (17)	−0.00845 (13)	−0.00281 (13)	−0.00202 (13)
C1	0.0122 (6)	0.0126 (6)	0.0128 (6)	−0.0027 (5)	−0.0011 (5)	0.0018 (5)
C2	0.0143 (6)	0.0132 (6)	0.0115 (6)	−0.0013 (5)	−0.0023 (5)	−0.0010 (5)
C3	0.0129 (6)	0.0119 (6)	0.0139 (6)	−0.0032 (5)	−0.0032 (5)	0.0007 (5)
C4	0.0150 (7)	0.0205 (7)	0.0129 (6)	−0.0037 (6)	0.0019 (5)	−0.0007 (6)
C5	0.0200 (7)	0.0180 (7)	0.0177 (7)	−0.0022 (6)	0.0023 (6)	−0.0008 (6)
C6	0.0191 (8)	0.0224 (8)	0.0208 (8)	0.0013 (6)	0.0015 (6)	0.0030 (6)
C7	0.0171 (7)	0.0299 (9)	0.0162 (7)	−0.0048 (6)	−0.0015 (6)	−0.0004 (6)
C8	0.0177 (7)	0.0246 (8)	0.0156 (7)	−0.0066 (6)	0.0004 (6)	−0.0035 (6)

Geometric parameters (Å, º)

I1—C1	2.0929 (15)	C4—C8ii	1.419 (2)
Cl1—C2	1.7196 (16)	C5—H5	0.9500
Cl2—C3	1.7252 (16)	C5—C6	1.374 (3)
C1—C2	1.399 (2)	C6—H6	0.9500
C1—C3	1.400 (2)	C6—C7	1.410 (3)
C2—C3i	1.401 (2)	C7—H7	0.9500
C4—C4ii	1.430 (3)	C7—C8	1.376 (3)
C4—C5	1.418 (2)	C8—H8	0.9500
C2—C1—I1	120.33 (11)	C4—C5—H5	119.6
C2—C1—C3	118.93 (13)	C6—C5—C4	120.84 (16)
C3—C1—I1	120.74 (11)	C6—C5—H5	119.6
C1—C2—Cl1	120.19 (12)	C5—C6—H6	120.0
C1—C2—C3i	120.74 (14)	C5—C6—C7	120.05 (16)
C3i—C2—Cl1	119.07 (11)	C7—C6—H6	120.0
C1—C3—Cl2	120.49 (12)	C6—C7—H7	119.6
C1—C3—C2i	120.33 (13)	C8—C7—C6	120.82 (16)
C2i—C3—Cl2	119.16 (11)	C8—C7—H7	119.6
C5—C4—C4ii	119.00 (19)	C4ii—C8—H8	119.8
C5—C4—C8ii	122.12 (15)	C7—C8—C4ii	120.41 (16)
C8ii—C4—C4ii	118.88 (19)	C7—C8—H8	119.8
I1—C1—C2—Cl1	−1.15 (18)	C3—C1—C2—C3i	−0.4 (2)
I1—C1—C2—C3i	178.35 (11)	C4ii—C4—C5—C6	0.5 (3)
I1—C1—C3—Cl2	3.33 (18)	C4—C5—C6—C7	−0.1 (3)
I1—C1—C3—C2i	−178.35 (11)	C5—C6—C7—C8	−0.3 (3)
C2—C1—C3—Cl2	−177.92 (11)	C6—C7—C8—C4ii	0.2 (3)
C2—C1—C3—C2i	0.4 (2)	C8ii—C4—C5—C6	179.92 (16)
C3—C1—C2—Cl1	−179.91 (11)

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y, −z+2.

Funding Statement

RHG gratefully acknowledges financial support from Webster University in the form of various Faculty Research Grants.