4,4′,6,6′-Tetra­methyl-2,2′-(ethyl­ene­dithio)­dipyrimidine

The unit cell of the crystal structure of the title compound, C₁₄H₁₈N₄S₂, contains two crystallographically independent mol­ecules, each located on an inversion center. The centroid-to-centroid separation of 3.478 (2) Å indicates the existence of π–π stacking between parallel pyrimidine rings of adjacent mol­ecules.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• Disorder in main residue
• R factor = 0.043
• wR factor = 0.144
• Data-to-parameter ratio = 18.2

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT153_ALERT_1_C The su's on the Cell Axes   are Equal (x 100000)        500 Ang.
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        500 Deg.
PLAT301_ALERT_3_C Main Residue  Disorder .........................       9.00 Perc.
PLAT380_ALERT_4_C Check Incorrectly? Oriented X(sp2)-Methyl Moiety         C8

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

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

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Previous studies have shown that heterocycle-based aromatic systems with conjugated multi-branched structure possess potential applications in optical image processing, all-optical switching, and integrated optical devices (Nishihara et al., 1989; Roberto et al., 2000). Therefore we pay our attention to the pyrimidine system, which has well known reactivity in the pyrimidine ring (positions 2, 4 and 6) and can easily be modified to conjugated multi-branched structures. As part of our ongoing investigation on pyrimidine derivatives, the title compound has been prepared and its crystal structure is presented here.

There are two crystallographically independent molecules, located on individual inversion center (Fig. 1). Bond lengths and angles in the two molecules are similar. The two pyrimidine rings are planar and parallel. The crystal packing (Fig. 2) is mainly stabilized by π–π stacking, the centroid-to-centroid separation between parallel N3-pyrimidine and N3ⁱ-pyrimidine rings being of 3.478 (2) Å [symmetry code: (i) 1 - x, -y, 2 - z].

Related literature

For related literature, see: Nishihara et al. (1989); Roberto et al. (2000).

S2. Experimental

A solution of 1,2-dibromoethane (0.94 g, 5 mmol) in ethanol (10 ml) was slowly dropped into a refluxing solution of 2-thiol-4,6-dimethylpyrimidine (1.40 g, 10 mmol) and NaOH (0.4 g, 10 mmol) in ethanol (20 ml). The reaction mixture was refluxed for 3 h and then cooled to room temperature. The white powder of title compound was filtered and washed thoroughly with water and then air dried (yield 55%). Single crystals suitable for X-ray analysis were obtained by slow evaporation from a dichloromethane/2-propanol (3:1) solution.

S3. Refinement

For one of independent molecules, the ethylenedithio moiety was disordered over two sites. The occupancies were refined and converged to 0.502 (10):0.498 (10). H atoms were positioned geometrically with C—H = 0.93 (aromatic), 0.97 (methylene) and 0.96 Å (methyl), and refined in riding mode with U_iso(H) = xU_eq(C), where x = 1.5 for methyl H and x = 1.2 for others.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: APEX2; program(s) used to solve structure: SIR97 (Altamore et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of the title compound showing 30% probability displacement ellipsoids. Hydrogen atoms are omitted for clarity.
	Fig. 2. Packing diagram of of the title compound viewed along the a axis. Hydrogen atoms are omitted for clarity.

4,4',6,6'-Tetramethyl-2,2'-(ethylenedithio)dipyrimidine

Crystal data

C14H18N4S2	Z = 2
Mr = 306.44	F(000) = 324
Triclinic, P1	Dx = 1.252 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71069 Å
a = 8.487 (5) Å	Cell parameters from 5112 reflections
b = 9.167 (5) Å	θ = 1.9–27.5°
c = 10.557 (5) Å	µ = 0.32 mm^−1
α = 85.282 (5)°	T = 293 K
β = 83.264 (5)°	Block, orange-yellow
γ = 89.711 (5)°	0.46 × 0.34 × 0.31 mm
V = 812.9 (8) Å^3

Data collection

Bruker APEXII CCD area-detector diffractometer	3721 independent reflections
Radiation source: fine-focus sealed tube	3008 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
φ and ω scans	θmax = 27.5°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −11→11
Tmin = 0.866, Tmax = 0.907	k = −11→11
11764 measured reflections	l = −13→13

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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.144	H-atom parameters constrained
S = 1.38	w = 1/[σ^2(Fo^2) + (0.0741P)^2] where P = (Fo^2 + 2Fc^2)/3
3721 reflections	(Δ/σ)max = 0.002
204 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	−0.1753 (2)	0.1379 (2)	0.4757 (2)	0.0806 (6)
H1A	−0.1925	0.1757	0.3909	0.121*
H1B	−0.2735	0.1379	0.5309	0.121*
H1C	−0.1358	0.0397	0.4734	0.121*
C2	−0.05600 (17)	0.23267 (15)	0.52551 (16)	0.0548 (4)
C3	−0.08802 (18)	0.29944 (17)	0.63776 (15)	0.0570 (4)
H3	−0.1856	0.2861	0.6875	0.068*
C4	0.02799 (18)	0.38698 (17)	0.67507 (15)	0.0548 (4)
C5	0.0014 (2)	0.4651 (2)	0.79489 (18)	0.0830 (6)
H5A	0.0663	0.4221	0.8564	0.125*
H5B	−0.1083	0.4567	0.8295	0.125*
H5C	0.0290	0.5666	0.7755	0.125*
C6	0.18869 (18)	0.33423 (17)	0.49854 (14)	0.0544 (4)
C7	0.5087 (5)	0.4183 (5)	0.5078 (5)	0.0581 (14)	0.498 (10)
H7A	0.4760	0.3784	0.5948	0.070*	0.498 (10)
H7B	0.6158	0.3871	0.4804	0.070*	0.498 (10)
C8	0.3687 (3)	0.0925 (2)	0.7483 (2)	0.0881 (6)
H8A	0.3110	0.0028	0.7725	0.132*
H8B	0.4025	0.0993	0.6580	0.132*
H8C	0.3014	0.1739	0.7686	0.132*
C9	0.5109 (2)	0.09497 (17)	0.81995 (15)	0.0595 (4)
C10	0.6268 (2)	−0.00835 (17)	0.80949 (16)	0.0642 (4)
H10	0.6211	−0.0824	0.7550	0.077*
C11	0.7522 (2)	−0.00184 (18)	0.88059 (16)	0.0630 (4)
C12	0.8825 (3)	−0.1125 (3)	0.8756 (3)	0.0996 (7)
H12A	0.9827	−0.0639	0.8738	0.149*
H12B	0.8822	−0.1638	0.7999	0.149*
H12C	0.8661	−0.1810	0.9498	0.149*
C13	0.64045 (18)	0.19983 (16)	0.96409 (14)	0.0519 (3)
C14	0.4877 (2)	0.44566 (18)	1.05891 (16)	0.0666 (4)
H14A	0.3960	0.3848	1.0533	0.080*
H14B	0.4659	0.4989	1.1347	0.080*
C7'	0.4535 (4)	0.5207 (6)	0.4450 (4)	0.0563 (14)	0.502 (10)
H7C	0.5195	0.5677	0.3719	0.068*	0.502 (10)
H7D	0.3642	0.5830	0.4692	0.068*	0.502 (10)
N1	0.08528 (15)	0.24921 (13)	0.45450 (12)	0.0554 (3)
N2	0.16878 (15)	0.40563 (15)	0.60426 (12)	0.0580 (3)
N3	0.51650 (15)	0.20336 (14)	0.89806 (12)	0.0573 (3)
N4	0.75976 (15)	0.10482 (15)	0.95989 (13)	0.0609 (4)
S1	0.3561 (4)	0.3698 (6)	0.3876 (3)	0.0653 (6)	0.498 (10)
S2	0.65828 (6)	0.33032 (5)	1.07490 (4)	0.06776 (18)
S1'	0.3855 (4)	0.3241 (4)	0.4131 (4)	0.0627 (6)	0.502 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0612 (11)	0.0723 (11)	0.1141 (16)	−0.0139 (9)	−0.0200 (10)	−0.0279 (11)
C2	0.0493 (8)	0.0444 (7)	0.0728 (10)	−0.0037 (6)	−0.0167 (7)	−0.0038 (7)
C3	0.0460 (8)	0.0578 (8)	0.0659 (9)	−0.0067 (6)	−0.0029 (7)	−0.0012 (7)
C4	0.0517 (8)	0.0603 (8)	0.0524 (8)	−0.0060 (6)	−0.0031 (6)	−0.0077 (7)
C5	0.0730 (12)	0.1109 (16)	0.0656 (11)	−0.0186 (11)	0.0084 (9)	−0.0321 (10)
C6	0.0524 (8)	0.0573 (8)	0.0541 (8)	−0.0100 (6)	−0.0029 (6)	−0.0113 (6)
C7	0.0451 (18)	0.054 (2)	0.074 (3)	−0.0017 (15)	−0.0004 (17)	−0.010 (2)
C8	0.0991 (15)	0.0875 (13)	0.0861 (13)	−0.0213 (11)	−0.0510 (12)	0.0004 (10)
C9	0.0734 (11)	0.0564 (8)	0.0505 (8)	−0.0190 (7)	−0.0179 (7)	0.0004 (7)
C10	0.0821 (12)	0.0565 (9)	0.0565 (8)	−0.0137 (8)	−0.0108 (8)	−0.0142 (7)
C11	0.0658 (10)	0.0618 (9)	0.0631 (9)	−0.0048 (8)	−0.0072 (8)	−0.0164 (7)
C12	0.0869 (15)	0.0971 (16)	0.122 (2)	0.0188 (12)	−0.0169 (14)	−0.0479 (14)
C13	0.0581 (9)	0.0514 (8)	0.0469 (7)	−0.0114 (6)	−0.0064 (6)	−0.0069 (6)
C14	0.0799 (11)	0.0591 (9)	0.0580 (9)	−0.0045 (8)	0.0090 (8)	−0.0122 (7)
C7'	0.0485 (18)	0.061 (3)	0.057 (2)	−0.0077 (17)	0.0011 (15)	−0.0031 (19)
N1	0.0557 (7)	0.0502 (7)	0.0626 (7)	−0.0053 (5)	−0.0103 (6)	−0.0135 (5)
N2	0.0523 (7)	0.0691 (8)	0.0531 (7)	−0.0154 (6)	0.0003 (6)	−0.0167 (6)
N3	0.0622 (8)	0.0553 (7)	0.0559 (7)	−0.0086 (6)	−0.0139 (6)	−0.0036 (6)
N4	0.0571 (8)	0.0652 (8)	0.0633 (8)	−0.0058 (6)	−0.0108 (6)	−0.0171 (6)
S1	0.0560 (10)	0.0808 (15)	0.0580 (8)	−0.0124 (9)	0.0088 (6)	−0.0198 (9)
S2	0.0806 (3)	0.0653 (3)	0.0617 (3)	−0.0084 (2)	−0.0146 (2)	−0.0215 (2)
S1'	0.0550 (9)	0.0644 (11)	0.0685 (11)	−0.0105 (7)	0.0076 (7)	−0.0259 (9)

Geometric parameters (Å, º)

C1—C2	1.505 (2)	C8—H8B	0.9600
C1—H1A	0.9600	C8—H8C	0.9600
C1—H1B	0.9600	C9—N3	1.347 (2)
C1—H1C	0.9600	C9—C10	1.363 (2)
C2—N1	1.340 (2)	C10—C11	1.377 (2)
C2—C3	1.377 (2)	C10—H10	0.9300
C3—C4	1.385 (2)	C11—N4	1.3450 (19)
C3—H3	0.9300	C11—C12	1.496 (3)
C4—N2	1.337 (2)	C12—H12A	0.9600
C4—C5	1.498 (2)	C12—H12B	0.9600
C5—H5A	0.9600	C12—H12C	0.9600
C5—H5B	0.9600	C13—N3	1.3272 (18)
C5—H5C	0.9600	C13—N4	1.331 (2)
C6—N1	1.3253 (19)	C13—S2	1.7595 (16)
C6—N2	1.3331 (19)	C14—C14^ii	1.523 (3)
C6—S1	1.746 (3)	C14—S2	1.804 (2)
C6—S1'	1.808 (3)	C14—H14A	0.9700
C7—C7^i	1.501 (9)	C14—H14B	0.9700
C7—S1	1.993 (6)	C7'—C7'^i	1.503 (9)
C7—H7A	0.9700	C7'—S1'	1.962 (6)
C7—H7B	0.9700	C7'—H7C	0.9700
C8—C9	1.499 (2)	C7'—H7D	0.9700
C8—H8A	0.9600
C2—C1—H1A	109.5	N3—C9—C10	121.50 (14)
C2—C1—H1B	109.5	N3—C9—C8	116.28 (16)
H1A—C1—H1B	109.5	C10—C9—C8	122.20 (16)
C2—C1—H1C	109.5	C9—C10—C11	119.23 (15)
H1A—C1—H1C	109.5	C9—C10—H10	120.4
H1B—C1—H1C	109.5	C11—C10—H10	120.4
N1—C2—C3	121.02 (13)	N4—C11—C10	120.31 (15)
N1—C2—C1	116.35 (15)	N4—C11—C12	117.42 (16)
C3—C2—C1	122.63 (16)	C10—C11—C12	122.26 (16)
C2—C3—C4	118.66 (15)	C11—C12—H12A	109.5
C2—C3—H3	120.7	C11—C12—H12B	109.5
C4—C3—H3	120.7	H12A—C12—H12B	109.5
N2—C4—C3	120.86 (15)	C11—C12—H12C	109.5
N2—C4—C5	117.29 (14)	H12A—C12—H12C	109.5
C3—C4—C5	121.85 (15)	H12B—C12—H12C	109.5
C4—C5—H5A	109.5	N3—C13—N4	127.89 (14)
C4—C5—H5B	109.5	N3—C13—S2	119.91 (12)
H5A—C5—H5B	109.5	N4—C13—S2	112.20 (11)
C4—C5—H5C	109.5	C14^ii—C14—S2	112.22 (17)
H5A—C5—H5C	109.5	C14^ii—C14—H14A	109.2
H5B—C5—H5C	109.5	S2—C14—H14A	109.2
N1—C6—N2	127.90 (14)	C14^ii—C14—H14B	109.2
N1—C6—S1	111.75 (14)	S2—C14—H14B	109.2
N2—C6—S1	119.71 (14)	H14A—C14—H14B	107.9
N1—C6—S1'	112.50 (14)	C7'^i—C7'—S1'	98.6 (4)
N2—C6—S1'	118.89 (14)	C7'^i—C7'—H7C	112.1
C7^i—C7—S1	97.3 (4)	S1'—C7'—H7C	112.1
C7^i—C7—H7A	112.3	C7'^i—C7'—H7D	112.1
S1—C7—H7A	112.3	S1'—C7'—H7D	112.1
C7^i—C7—H7B	112.3	H7C—C7'—H7D	109.7
S1—C7—H7B	112.3	C6—N1—C2	115.82 (14)
H7A—C7—H7B	109.9	C6—N2—C4	115.73 (13)
C9—C8—H8A	109.5	C13—N3—C9	115.11 (13)
C9—C8—H8B	109.5	C13—N4—C11	115.95 (13)
H8A—C8—H8B	109.5	C6—S1—C7	98.73 (17)
C9—C8—H8C	109.5	C13—S2—C14	103.18 (8)
H8A—C8—H8C	109.5	C6—S1'—C7'	96.10 (16)
H8B—C8—H8C	109.5
N1—C2—C3—C4	1.3 (2)	S2—C13—N3—C9	−177.29 (10)
C1—C2—C3—C4	−178.81 (16)	C10—C9—N3—C13	−1.0 (2)
C2—C3—C4—N2	−0.5 (2)	C8—C9—N3—C13	177.51 (14)
C2—C3—C4—C5	179.09 (15)	N3—C13—N4—C11	−1.2 (2)
N3—C9—C10—C11	0.1 (3)	S2—C13—N4—C11	177.79 (11)
C8—C9—C10—C11	−178.30 (17)	C10—C11—N4—C13	0.1 (2)
C9—C10—C11—N4	0.3 (3)	C12—C11—N4—C13	−178.68 (18)
C9—C10—C11—C12	179.08 (19)	N1—C6—S1—C7	−157.0 (2)
N2—C6—N1—C2	−0.4 (2)	N2—C6—S1—C7	31.4 (4)
S1—C6—N1—C2	−171.1 (2)	S1'—C6—S1—C7	−61.0 (5)
S1'—C6—N1—C2	169.7 (2)	C7^i—C7—S1—C6	−96.1 (3)
C3—C2—N1—C6	−0.8 (2)	N3—C13—S2—C14	−2.25 (14)
C1—C2—N1—C6	179.23 (13)	N4—C13—S2—C14	178.69 (12)
N1—C6—N2—C4	1.1 (2)	C14^ii—C14—S2—C13	−78.53 (18)
S1—C6—N2—C4	171.2 (2)	N1—C6—S1'—C7'	153.0 (2)
S1'—C6—N2—C4	−168.4 (2)	N2—C6—S1'—C7'	−35.9 (4)
C3—C4—N2—C6	−0.6 (2)	S1—C6—S1'—C7'	61.7 (5)
C5—C4—N2—C6	179.79 (15)	C7'^i—C7'—S1'—C6	99.1 (3)
N4—C13—N3—C9	1.6 (2)

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