N,N′-(m-Phenyl­enedimethyl­idyne)dianiline

A new Schiff base compound, C₂₀H₁₆N₂, was prepared by the reaction of isophthalaldehyde with aniline. The terminal phenyl rings are almost perpendicular, with a dihedral angle of 85.8 (2)°. The terminal phenyl rings make dihedral angles of 60.8 (2) and 52.5 (2)° with the central ring. Both C=N groups adopt a trans configuration. Adjacent pairs of centrosymmetrically related mol­ecules are connected via π–π stacking inter­actions between their central benzene rings, with a centroid–centroid distance of 3.747 (2) Å.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.043
• wR factor = 0.130
• Data-to-parameter ratio = 18.2

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S1. Comment

Schiff base complexes have been playing an important part in the area of coordination and supramolecular chemistry. The metal complexes of Schiff bases have been of interest for many years due to their homogeneous catalysis and enzymatic reactions, antibacterial activities, magnetism and molecular architectures (Costamagna et al., 1992). Accordingly, we have designed and synthesized a new Schiff base complex, viz. 1,3-Isophthalylidene-bis(N-aniline).

The molecular structure of (I) is shown in Fig. 1. Each of the individual benzene ring is essentially planar. the terminal phenyl rings are almost perpendicular, with a relative dihedral angle of 85.8 (2) °. The terminal phenyl rings (C1—C6) and (C15—C20) make dihedral angles of 119.2 (2) and 52.5 (2) °, respectively with the central ring. Pairs of centrosymmetrically related molecules are cross-linked via π-π stacking interactions between the central C₆ rings of the molecules at (x, y, z) and (1 - x, 1 - y, 1 - z), with a centroid···centroid distance of 3.747 (2) Å (Fig. 2). The corresponding complex 1,4-Terephthalylidene-bis-N-aniline (Thyen & Zugenmaier, 1994), with terephthalaldehyde instead of isophthalaldehyde, is centrosymmetric with the two parallel aniline terminal groups in a trans arrangement and the structure does not exhibit π-π stacking.

Related literature

The corresponding complex 1,4-terephthalylidene-bis-N-aniline (Thyen & Zugenmaier, 1994), with terephthalaldehyde instead of isophthalaldehyde, is centrosymmetric, with the two parallel aniline terminal groups in a trans arrangement. For a review of Schiff base chemistry, see: Costamagna et al. (1992).

S2. Experimental

To a solution of isophthalaldehyde (1.34 g, 10 mmol) in ethanol was added a solution of aniline (0.93 g, 10 mmol) in ethanol. The mixture was refluxed for 2 h, and a yellow precipitate (8 mmol) was obtained. Colorless crystals were obtained by recrystallization of the material from methanol with a yield of 80%. Analysis calculated for C₂₀H₁₆N₂: C 84.48, H 5.67, N 9.85%. Found: C 84.44, H 5.63, N 9.89%.

S3. Refinement

C-bound H atoms were placed in calculated positions, with phenyl C—H = 0.95 Å and methylene C—H = 0.97 Å and U_iso(H) = 1.2U_eq(C), which were included in the refinement in a riding-model.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A view of complex (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms drawn as spheres of arbitrary radius.
	Fig. 2. A unit cell packing plot with the two molecules in the cell. Cg1 and Cg2 represent the centroids of adjacent central phenyl rings, as defined in the comment section.

N,N'-(m-Phenylenedimethylidyne)dianiline

Crystal data

C20H16N2	Z = 2
Mr = 284.35	F(000) = 300
Triclinic, P1	Dx = 1.176 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.7762 (16) Å	Cell parameters from 6349 reflections
b = 10.301 (2) Å	θ = 3.0–27.5°
c = 10.744 (2) Å	µ = 0.07 mm^−1
α = 79.79 (3)°	T = 295 K
β = 78.85 (3)°	Prism, colourless
γ = 73.64 (3)°	0.38 × 0.26 × 0.18 mm
V = 803.3 (3) Å^3

Data collection

Rigaku RAXIS-RAPID diffractometer	3624 independent reflections
Radiation source: fine-focus sealed tube	2738 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.016
Detector resolution: 10.000 pixels mm^-1	θmax = 27.5°, θmin = 3.0°
ω scans	h = −10→9
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −13→12
Tmin = 0.973, Tmax = 0.990	l = −13→13
7920 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.130	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0691P)^2 + 0.053P] where P = (Fo^2 + 2Fc^2)/3
3624 reflections	(Δ/σ)max < 0.001
199 parameters	Δρmax = 0.16 e Å^−3
0 restraints	Δρmin = −0.22 e Å^−3

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

	x	y	z	Uiso*/Ueq
N1	0.66676 (14)	0.80219 (11)	0.43392 (10)	0.0506 (3)
N2	0.27572 (14)	0.42636 (11)	0.86926 (10)	0.0494 (3)
C1	1.0361 (2)	0.99763 (16)	0.19367 (15)	0.0654 (4)
H1	1.1191	1.0410	0.1415	0.079*
C2	0.99453 (19)	0.89164 (16)	0.15464 (13)	0.0594 (4)
H2	1.0506	0.8629	0.0760	0.071*
C3	0.86986 (17)	0.82709 (14)	0.23124 (12)	0.0514 (3)
H3	0.8414	0.7560	0.2038	0.062*
C4	0.78783 (16)	0.86901 (12)	0.34905 (11)	0.0459 (3)
C5	0.83306 (19)	0.97395 (14)	0.38884 (14)	0.0584 (3)
H5	0.7815	1.0008	0.4689	0.070*
C6	0.9545 (2)	1.03902 (15)	0.31012 (16)	0.0674 (4)
H6	0.9812	1.1116	0.3363	0.081*
C7	0.53387 (16)	0.78369 (12)	0.39400 (12)	0.0463 (3)
H7	0.5145	0.8189	0.3105	0.056*
C8	0.40962 (15)	0.70868 (11)	0.47468 (11)	0.0433 (3)
C9	0.25288 (16)	0.70395 (13)	0.43283 (12)	0.0488 (3)
H9	0.2261	0.7498	0.3534	0.059*
C10	0.13722 (16)	0.63159 (14)	0.50845 (13)	0.0519 (3)
H10	0.0327	0.6295	0.4798	0.062*
C11	0.17518 (16)	0.56267 (12)	0.62576 (12)	0.0477 (3)
H11	0.0970	0.5135	0.6757	0.057*
C12	0.33100 (15)	0.56638 (12)	0.67014 (11)	0.0434 (3)
C13	0.44736 (15)	0.63837 (12)	0.59366 (11)	0.0439 (3)
H13	0.5523	0.6398	0.6221	0.053*
C14	0.37739 (17)	0.49192 (13)	0.79393 (11)	0.0484 (3)
H14	0.4857	0.4931	0.8178	0.058*
C15	0.33471 (16)	0.34699 (13)	0.98210 (12)	0.0473 (3)
C16	0.21510 (17)	0.35252 (15)	1.09537 (13)	0.0566 (3)
H16	0.0994	0.4111	1.0974	0.068*
C17	0.26643 (19)	0.27153 (15)	1.20555 (13)	0.0591 (4)
H17	0.1859	0.2780	1.2818	0.071*
C18	0.4324 (2)	0.18267 (15)	1.20450 (14)	0.0626 (4)
H18	0.4655	0.1282	1.2792	0.075*
C19	0.5502 (2)	0.1741 (2)	1.09289 (16)	0.0879 (6)
H19	0.6636	0.1122	1.0912	0.105*
C20	0.5026 (2)	0.25688 (19)	0.98157 (14)	0.0778 (5)
H20	0.5849	0.2512	0.9062	0.093*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0509 (6)	0.0530 (6)	0.0467 (6)	−0.0147 (5)	−0.0086 (4)	−0.0003 (5)
N2	0.0485 (6)	0.0539 (6)	0.0445 (6)	−0.0110 (5)	−0.0127 (4)	−0.0001 (5)
C1	0.0602 (8)	0.0676 (9)	0.0675 (9)	−0.0266 (7)	−0.0142 (7)	0.0154 (7)
C2	0.0573 (8)	0.0716 (9)	0.0455 (7)	−0.0169 (7)	−0.0095 (6)	0.0047 (6)
C3	0.0548 (7)	0.0539 (7)	0.0463 (7)	−0.0152 (6)	−0.0142 (5)	0.0007 (5)
C4	0.0447 (6)	0.0438 (6)	0.0467 (7)	−0.0082 (5)	−0.0130 (5)	0.0025 (5)
C5	0.0608 (8)	0.0530 (7)	0.0617 (8)	−0.0134 (6)	−0.0093 (6)	−0.0102 (6)
C6	0.0709 (9)	0.0538 (8)	0.0840 (11)	−0.0260 (7)	−0.0172 (8)	−0.0035 (7)
C7	0.0469 (6)	0.0446 (6)	0.0435 (6)	−0.0063 (5)	−0.0096 (5)	−0.0021 (5)
C8	0.0420 (6)	0.0397 (6)	0.0450 (6)	−0.0046 (5)	−0.0069 (5)	−0.0068 (5)
C9	0.0468 (6)	0.0505 (7)	0.0453 (7)	−0.0050 (5)	−0.0150 (5)	0.0004 (5)
C10	0.0421 (6)	0.0560 (7)	0.0578 (8)	−0.0097 (6)	−0.0181 (5)	−0.0012 (6)
C11	0.0417 (6)	0.0474 (6)	0.0520 (7)	−0.0096 (5)	−0.0092 (5)	−0.0019 (5)
C12	0.0425 (6)	0.0428 (6)	0.0423 (6)	−0.0051 (5)	−0.0087 (5)	−0.0057 (5)
C13	0.0416 (6)	0.0461 (6)	0.0450 (6)	−0.0088 (5)	−0.0107 (5)	−0.0080 (5)
C14	0.0441 (6)	0.0558 (7)	0.0450 (7)	−0.0097 (6)	−0.0121 (5)	−0.0047 (5)
C15	0.0477 (6)	0.0515 (7)	0.0432 (6)	−0.0119 (6)	−0.0131 (5)	−0.0020 (5)
C16	0.0419 (6)	0.0664 (8)	0.0553 (8)	−0.0108 (6)	−0.0071 (5)	0.0035 (6)
C17	0.0553 (8)	0.0707 (9)	0.0480 (7)	−0.0205 (7)	−0.0047 (6)	0.0048 (6)
C18	0.0698 (9)	0.0639 (8)	0.0492 (8)	−0.0114 (7)	−0.0190 (6)	0.0073 (6)
C19	0.0689 (10)	0.1005 (13)	0.0617 (10)	0.0240 (9)	−0.0132 (8)	0.0037 (9)
C20	0.0632 (9)	0.0964 (12)	0.0467 (8)	0.0143 (9)	−0.0034 (6)	−0.0009 (7)

Geometric parameters (Å, º)

N1—C7	1.2648 (16)	C9—H9	0.9300
N1—C4	1.4149 (16)	C10—C11	1.3743 (18)
N2—C14	1.2632 (17)	C10—H10	0.9300
N2—C15	1.4146 (16)	C11—C12	1.3976 (17)
C1—C6	1.371 (2)	C11—H11	0.9300
C1—C2	1.373 (2)	C12—C13	1.3849 (17)
C1—H1	0.9300	C12—C14	1.4682 (17)
C2—C3	1.3855 (19)	C13—H13	0.9300
C2—H2	0.9300	C14—H14	0.9300
C3—C4	1.3863 (18)	C15—C20	1.372 (2)
C3—H3	0.9300	C15—C16	1.3807 (18)
C4—C5	1.3825 (19)	C16—C17	1.3791 (19)
C5—C6	1.379 (2)	C16—H16	0.9300
C5—H5	0.9300	C17—C18	1.355 (2)
C6—H6	0.9300	C17—H17	0.9300
C7—C8	1.4632 (17)	C18—C19	1.361 (2)
C7—H7	0.9300	C18—H18	0.9300
C8—C13	1.3936 (17)	C19—C20	1.388 (2)
C8—C9	1.3941 (17)	C19—H19	0.9300
C9—C10	1.3801 (18)	C20—H20	0.9300
C7—N1—C4	119.49 (11)	C9—C10—H10	119.7
C14—N2—C15	119.86 (11)	C10—C11—C12	120.12 (12)
C6—C1—C2	119.56 (14)	C10—C11—H11	119.9
C6—C1—H1	120.2	C12—C11—H11	119.9
C2—C1—H1	120.2	C13—C12—C11	119.18 (11)
C1—C2—C3	120.66 (14)	C13—C12—C14	119.25 (11)
C1—C2—H2	119.7	C11—C12—C14	121.54 (11)
C3—C2—H2	119.7	C12—C13—C8	121.02 (11)
C2—C3—C4	119.62 (13)	C12—C13—H13	119.5
C2—C3—H3	120.2	C8—C13—H13	119.5
C4—C3—H3	120.2	N2—C14—C12	122.46 (11)
C5—C4—C3	119.40 (12)	N2—C14—H14	118.8
C5—C4—N1	118.50 (12)	C12—C14—H14	118.8
C3—C4—N1	121.99 (12)	C20—C15—C16	118.43 (12)
C6—C5—C4	120.16 (14)	C20—C15—N2	122.31 (12)
C6—C5—H5	119.9	C16—C15—N2	119.09 (11)
C4—C5—H5	119.9	C17—C16—C15	120.27 (12)
C1—C6—C5	120.55 (14)	C17—C16—H16	119.9
C1—C6—H6	119.7	C15—C16—H16	119.9
C5—C6—H6	119.7	C18—C17—C16	121.03 (13)
N1—C7—C8	122.23 (11)	C18—C17—H17	119.5
N1—C7—H7	118.9	C16—C17—H17	119.5
C8—C7—H7	118.9	C17—C18—C19	119.27 (13)
C13—C8—C9	118.70 (11)	C17—C18—H18	120.4
C13—C8—C7	120.71 (11)	C19—C18—H18	120.4
C9—C8—C7	120.58 (11)	C18—C19—C20	120.55 (15)
C10—C9—C8	120.43 (11)	C18—C19—H19	119.7
C10—C9—H9	119.8	C20—C19—H19	119.7
C8—C9—H9	119.8	C15—C20—C19	120.41 (14)
C11—C10—C9	120.55 (12)	C15—C20—H20	119.8
C11—C10—H10	119.7	C19—C20—H20	119.8
C6—C1—C2—C3	0.6 (2)	C10—C11—C12—C14	−178.87 (11)
C1—C2—C3—C4	−0.70 (19)	C11—C12—C13—C8	1.12 (17)
C2—C3—C4—C5	−0.59 (18)	C14—C12—C13—C8	179.03 (10)
C2—C3—C4—N1	−176.67 (11)	C9—C8—C13—C12	−0.81 (17)
C7—N1—C4—C5	131.54 (13)	C7—C8—C13—C12	−179.55 (10)
C7—N1—C4—C3	−52.35 (16)	C15—N2—C14—C12	174.56 (11)
C3—C4—C5—C6	2.01 (19)	C13—C12—C14—N2	178.68 (11)
N1—C4—C5—C6	178.23 (12)	C11—C12—C14—N2	−3.47 (19)
C2—C1—C6—C5	0.9 (2)	C14—N2—C15—C20	−48.6 (2)
C4—C5—C6—C1	−2.2 (2)	C14—N2—C15—C16	136.25 (14)
C4—N1—C7—C8	176.51 (10)	C20—C15—C16—C17	1.7 (2)
N1—C7—C8—C13	−8.86 (18)	N2—C15—C16—C17	177.05 (12)
N1—C7—C8—C9	172.43 (12)	C15—C16—C17—C18	−1.8 (2)
C13—C8—C9—C10	0.39 (18)	C16—C17—C18—C19	0.3 (2)
C7—C8—C9—C10	179.13 (11)	C17—C18—C19—C20	1.1 (3)
C8—C9—C10—C11	−0.30 (19)	C16—C15—C20—C19	−0.3 (3)
C9—C10—C11—C12	0.61 (19)	N2—C15—C20—C19	−175.48 (16)
C10—C11—C12—C13	−1.01 (18)	C18—C19—C20—C15	−1.1 (3)