2,5-Bis{[(−)-(S)-1-(4-bromo­phen­yl)eth­yl]imino­meth­yl}thio­phene

The title compound, C₂₂H₂₀Br₂N₂S, was synthesized under solvent-free conditions. The mol­ecule shows crystallographic C₂ symmetry, with the S atom of the central thio­phene ring lying on a twofold rotation axis. Furthermore, as a consequence of the (S,S) stereochemistry, the mol­ecule has a twisted conformation. The dihedral angle between the thio­phene and benzene rings is 72.7 (2)° and that between the two benzene rings is 55.9 (2)°. In the crystal, mol­ecules are arranged in a chevron-like pattern, without any significant inter­molecular inter­actions.

Related literature

For the solvent-free organic synthesis, see: Tanaka & Toda (2000). For the structure of a chiral bis-aldimine compound, see: Espinosa Leija et al. (2009). For structures of thio­phenes substituted in positions 2 and 5 by imine functionalities, see: Bernès et al. (2013); Kudyakova et al. (2012).

Experimental

Crystal data

• C₂₂H₂₀Br₂N₂S

• M_r = 504.27

• Monoclinic, C 2

• a = 24.5329 (15) Å

• b = 5.9762 (5) Å

• c = 7.5944 (5) Å

• β = 98.536 (6)°

• V = 1101.11 (14) ų

• Z = 2

• Mo Kα radiation

• μ = 3.79 mm⁻¹

• T = 298 K

• 0.52 × 0.15 × 0.06 mm

Data collection

• Agilent Xcalibur (Atlas, Gemini) diffractometer

• Absorption correction: numerical (CrysAlis PRO; Agilent, 2013) T_min = 0.400, T_max = 0.815

• 6101 measured reflections

• 2107 independent reflections

• 1630 reflections with I > 2σ(I)

• R_int = 0.035

Refinement

• R[F² > 2σ(F²)] = 0.036

• wR(F²) = 0.072

• S = 1.03

• 2107 reflections

• 124 parameters

• 1 restraint

• H-atom parameters constrained

• Δρ_max = 0.20 e Å⁻³

• Δρ_min = −0.35 e Å⁻³

• Absolute structure: Flack (1983), 914 Friedel pairs

• Absolute structure parameter: 0.011 (8)

Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Agilent, 2013); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012).

Supporting information

S1. Comment

In continuation of our work focused on chiral bisimines (Espinosa Leija et al., 2009; Bernès et al., 2013), we have now synthesized the title compound under the solvent-free approach because of the cleaner, safer, and easier aspects to perform in the synthetic work. So, solvent-free conditions are becoming more popular and it is often claimed that the best solvent is no solvent. (Tanaka & Toda, 2000).

The bis-aldimine compound shows an E configuration over every imine bond (Fig. 1). The molecule is an (S,S) diastereoisomer as expected by synthetic procedure. The asymmetric unit contains a half-molecule. The S atom of the molecule is located on a twofold rotation axis of the space group C2. and as a consequence the Br-aldimines groups are placed opposite to the central thiophene ring. Only some previous reports of 2,5-thiophene compounds with achiral or chiral substituents have showed C₂ crystallographic symmetry like title compound (Kudyakova et al., 2012, space group C2/c; Bernès et al., 2013, space group P22₁2₁). The crystal packing does not feature any particular interactions (intra or intermolecular) and the supramolecular arrangement in the solid state shows a chevron-like pattern viewed along the b axis (Fig. 2).

Related literature

For the solvent-free organic synthesis, see: Tanaka & Toda (2000). For the structure of a chiral bis-aldimine compound, see: Espinosa Leija et al. (2009). For structures of thiophenes substituted in positions 2 and 5 by imine functionalities, see: Bernès et al. (2013); Kudyakova et al. (2012).

S2. Experimental

Under solvent-free conditions, a mixture of 2,5-thiophenedicarboxaldehyde (100 mg, 0.71 mmol) and (S)-(–)-1-(4-bromophenyl)ethylamine (285 mg, 1.42 mmol) in a 1:2 molar ratio were mixed at room temperature, giving a white solid. The crude was recrystallized from CH₂Cl₂, affording colorless crystals of the title compound.

Yield 96%; m.p. 147–149 °C. Spectroscopic data: [a]_D²⁵ = +59.6 (c 1, CHCl₃). IR (KBr): 1623 cm^-1 (C=N). ¹H NMR (400 MHz, CDCl₃/TMS): δ = 1.51, 1.53 (d, 6H, CHCH₃,), 4.44, 4.45, 4.47, 4.49(q, 2H, CH), 7.29–7.45 (m, 10 H, Ar), 8.36 (s, 2 H, HC=N). ¹³C NMR (100 MHz, CDCl₃/TMS) δ = 25.1 (CCH₃), 68.7 (CHCH₃), 120.6 (Ar), 128.3 (Ar), 130.1 (Ar), 131.4 (Ar), 144.0 (Ar), 145.1 (Ar), 152. 7 (HC=N). MS—EI: m/z= 504 (M⁺).

S3. Refinement

The absolute configuration was determined using the anomalous dispersion of the Br atom, and was that expected from the synthesis, carried-out with an enantiomerically pure amine. All H atoms were placed in calculated positions, with C—H bond lengths fixed to 0.96 Å for the methyl group and 0.93 Å for aromatic CH groups. Isotropic displacement parameters were calculated as U_iso(H) = 1.5U_eq(carrier atom) for the methyl group and U_iso(H) = 1.2U_eq(carrier atom) otherwise.

Computing details

Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO (Agilent, 2013); data reduction: CrysAlis RED (Agilent, 2013); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012).

Figures

	Fig. 1. The molecular structure of title compound, with atom labels and 30% probability displacement ellipsoids for non-H atoms.
	Fig. 2. A packing diagram of the title compound, viewed along the b axis.

2,5-Bis{[(–)-(S)-1-(4-bromophenyl)ethyl]iminomethyl}thiophene

Crystal data

C22H20Br2N2S	F(000) = 504
Mr = 504.27	Dx = 1.521 Mg m^−3
Monoclinic, C2	Melting point: 420 K
Hall symbol: C 2y	Mo Kα radiation, λ = 0.71073 Å
a = 24.5329 (15) Å	Cell parameters from 1609 reflections
b = 5.9762 (5) Å	θ = 4.4–25.2°
c = 7.5944 (5) Å	µ = 3.79 mm^−1
β = 98.536 (6)°	T = 298 K
V = 1101.11 (14) Å^3	Prism, colourless
Z = 2	0.52 × 0.15 × 0.06 mm

Data collection

Agilent Xcalibur (Atlas, Gemini) diffractometer	2107 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1630 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
Detector resolution: 10.5564 pixels mm^-1	θmax = 26.1°, θmin = 3.0°
ω scans	h = −30→30
Absorption correction: numerical (CrysAlis PRO; Agilent, 2013)	k = −7→7
Tmin = 0.400, Tmax = 0.815	l = −9→9
6101 measured reflections

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.036	w = 1/[σ^2(Fo^2) + (0.0288P)^2 + 0.0296P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.072	(Δ/σ)max < 0.001
S = 1.03	Δρmax = 0.20 e Å^−3
2107 reflections	Δρmin = −0.35 e Å^−3
124 parameters	Absolute structure: Flack (1983), 914 Friedel pairs
1 restraint	Absolute structure parameter: 0.011 (8)
0 constraints

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.

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

	x	y	z	Uiso*/Ueq
Br1	0.15628 (2)	0.49000 (18)	0.61658 (7)	0.1112 (4)
S1	0.5	0.2196 (2)	0.5	0.0472 (4)
C9	0.47486 (16)	0.0181 (7)	0.6292 (5)	0.0427 (10)
C11	0.4216 (2)	0.4840 (10)	1.0744 (5)	0.0657 (13)
H11A	0.4194	0.6248	1.0129	0.099*
H11B	0.4595	0.4499	1.1175	0.099*
H11C	0.4013	0.4929	1.173	0.099*
C4	0.2306 (2)	0.4327 (11)	0.7169 (6)	0.0639 (15)
C1	0.33894 (18)	0.3489 (7)	0.8651 (5)	0.0441 (11)
C6	0.3243 (2)	0.5418 (9)	0.7670 (6)	0.0569 (13)
H6	0.3514	0.6457	0.7513	0.068*
N1	0.43094 (15)	0.2748 (6)	0.8052 (5)	0.0452 (9)
C5	0.2703 (2)	0.5823 (9)	0.6921 (7)	0.0674 (16)
H5	0.2613	0.711	0.6253	0.081*
C2	0.2971 (2)	0.1997 (9)	0.8837 (6)	0.0603 (13)
H2	0.3056	0.0688	0.9482	0.072*
C3	0.2431 (2)	0.2389 (11)	0.8092 (7)	0.0690 (14)
H3	0.2157	0.135	0.8218	0.083*
C7	0.3974 (2)	0.3024 (8)	0.9485 (5)	0.0501 (12)
H7	0.398	0.1616	1.0149	0.06*
C8	0.44434 (18)	0.0769 (7)	0.7709 (6)	0.0469 (12)
H8	0.4339	−0.038	0.8414	0.056*
C10	0.4853 (2)	−0.1907 (8)	0.5728 (7)	0.0540 (13)
H10	0.4743	−0.3205	0.625	0.065*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0529 (4)	0.2036 (8)	0.0729 (4)	0.0279 (5)	−0.0044 (3)	−0.0229 (5)
S1	0.0553 (11)	0.0347 (8)	0.0547 (10)	0	0.0179 (8)	0
C9	0.043 (2)	0.038 (2)	0.047 (2)	0.001 (2)	0.0052 (18)	0.005 (2)
C11	0.058 (3)	0.085 (3)	0.053 (2)	0.009 (3)	0.005 (2)	−0.003 (3)
C4	0.044 (3)	0.106 (5)	0.042 (2)	0.005 (3)	0.006 (2)	−0.009 (3)
C1	0.044 (3)	0.053 (3)	0.037 (2)	0.001 (2)	0.012 (2)	0.002 (2)
C6	0.052 (3)	0.062 (3)	0.056 (3)	−0.002 (3)	0.007 (2)	0.016 (3)
N1	0.042 (2)	0.052 (2)	0.0439 (19)	0.0014 (17)	0.0134 (17)	0.0053 (16)
C5	0.063 (4)	0.084 (4)	0.053 (3)	0.010 (3)	0.003 (3)	0.014 (3)
C2	0.064 (4)	0.067 (3)	0.053 (3)	−0.002 (3)	0.017 (2)	0.011 (3)
C3	0.051 (3)	0.094 (4)	0.065 (3)	−0.019 (3)	0.017 (3)	−0.005 (3)
C7	0.051 (3)	0.060 (3)	0.043 (2)	0.006 (2)	0.017 (2)	0.011 (2)
C8	0.039 (3)	0.051 (3)	0.051 (3)	0.000 (2)	0.008 (2)	0.013 (2)
C10	0.057 (3)	0.035 (2)	0.073 (3)	−0.001 (2)	0.017 (3)	0.005 (2)

Geometric parameters (Å, º)

Br1—C4	1.899 (5)	C1—C7	1.505 (6)
S1—C9^i	1.724 (4)	C6—H6	0.93
S1—C9	1.724 (4)	C6—C5	1.383 (7)
C9—C8	1.442 (6)	N1—C7	1.468 (5)
C9—C10	1.356 (6)	N1—C8	1.265 (5)
C11—H11A	0.96	C5—H5	0.93
C11—H11B	0.96	C2—H2	0.93
C11—H11C	0.96	C2—C3	1.382 (7)
C11—C7	1.509 (7)	C3—H3	0.93
C4—C5	1.356 (7)	C7—H7	0.98
C4—C3	1.365 (7)	C8—H8	0.93
C1—C6	1.391 (6)	C10—C10^i	1.405 (10)
C1—C2	1.383 (7)	C10—H10	0.93
C9—S1—C9^i	91.4 (3)	C4—C5—H5	120.3
C8—C9—S1	121.6 (3)	C6—C5—H5	120.3
C10—C9—S1	111.2 (3)	C1—C2—H2	119
C10—C9—C8	127.1 (4)	C3—C2—C1	122.0 (5)
H11A—C11—H11B	109.5	C3—C2—H2	119
H11A—C11—H11C	109.5	C4—C3—C2	118.9 (5)
H11B—C11—H11C	109.5	C4—C3—H3	120.6
C7—C11—H11A	109.5	C2—C3—H3	120.6
C7—C11—H11B	109.5	C11—C7—H7	108.5
C7—C11—H11C	109.5	C1—C7—C11	113.2 (4)
C5—C4—Br1	119.5 (4)	C1—C7—H7	108.5
C5—C4—C3	121.3 (5)	N1—C7—C11	109.9 (4)
C3—C4—Br1	119.2 (4)	N1—C7—C1	108.2 (3)
C6—C1—C7	122.2 (4)	N1—C7—H7	108.5
C2—C1—C6	116.9 (4)	C9—C8—H8	117.9
C2—C1—C7	120.9 (4)	N1—C8—C9	124.1 (4)
C1—C6—H6	119.3	N1—C8—H8	117.9
C5—C6—C1	121.3 (5)	C9—C10—C10^i	113.1 (3)
C5—C6—H6	119.3	C9—C10—H10	123.5
C8—N1—C7	116.7 (3)	C10^i—C10—H10	123.5
C4—C5—C6	119.5 (5)
Br1—C4—C5—C6	179.2 (4)	C2—C1—C6—C5	0.2 (7)
Br1—C4—C3—C2	−179.2 (4)	C2—C1—C7—C11	−122.6 (5)
S1—C9—C8—N1	4.2 (6)	C2—C1—C7—N1	115.3 (4)
S1—C9—C10—C10^i	1.2 (7)	C3—C4—C5—C6	−2.3 (8)
C9^i—S1—C9—C8	−177.3 (4)	C7—C1—C6—C5	−179.6 (4)
C9^i—S1—C9—C10	−0.4 (3)	C7—C1—C2—C3	179.7 (4)
C1—C6—C5—C4	1.0 (7)	C7—N1—C8—C9	176.9 (4)
C1—C2—C3—C4	−1.0 (7)	C8—C9—C10—C10^i	177.9 (5)
C6—C1—C2—C3	−0.2 (7)	C8—N1—C7—C11	131.9 (4)
C6—C1—C7—C11	57.3 (5)	C8—N1—C7—C1	−104.0 (4)
C6—C1—C7—N1	−64.8 (5)	C10—C9—C8—N1	−172.2 (5)
C5—C4—C3—C2	2.3 (7)

Symmetry code: (i) −x+1, y, −z+1.