Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103029433/sk1691sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270103029433/sk1691Iasup2.hkl |
CCDC reference: 233137
Compound (Ia) was synthesized by a two-step procedure, as described elsewhere (Přikryl et al., 2003). Briefly, in the first step, cooling and stirring of 96% sulfuric acid (25 ml, 0.45 mol) was followed by addition of NaNO2 in small portions, so as to avoid evolution of nitrous gases. After continuous stirring and slow heating (to 343 K), the resulting solution of nitrosyl sulfuric acid was cooled to 300 K; 3-amino-5-nitrobenzo[c]-1,2-thiazole was added and the reaction mixture was stirred for 3 h. In the next step, a solution of N-butylaniline (7.82 g, 52.5 mmol) in 1 M aqueous HCl (60 ml) was treated with charcoal and kieselguhr (0.25 g each), and after 10 min of stirring the solution was filtered. The filtrate, the solution of N-butylanilinium chloride, was treated with an emulsifier and sodium acetate trihydrate (68 g, 0.5 mol) under stirring. The obtained emulsion of N-butyl aniline was mixed with finely crushed ice, and then the solution of the diazonium salt obtained in the previous step was added while stirring. The reaction mixture was stirred for 3 h, whereupon the separated orange–brown precipitate of the triazene was collected by suction. The raw product (12.6 g, 71% yield) was purified by repeated crystallization from acetone (m.p. 398–400 K).
The disorder in the n-butyl chain was modelled by resolving the positions of atoms C18 and C19 into two components (C18/C18' and C19/C19'), and using a total of 21 restraints on corresponding bond distances and anisotropic displacement parameters [a combination of DFIX and SIMU options in SHELXL97 (Sheldrick, 1997)]. The refined occupancy factors for the unprimed and primed sites were 0.53 (1) and 0.47 (1), respectively. H atoms were refined with fixed geometry, riding on their carrier atoms, with Uiso set to 1.2 (1.5 for the methyl H atoms) times Ueq of the parent atom.
Data collection: CrysAlis CCD (Oxford Diffraction Ltd, 2001'; cell refinement: CrysAlis RED (Oxford Diffraction Ltd, 2003'; data reduction: CrysAlis RED'; 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.
C17H17N5O2S | Z = 2 |
Mr = 355.42 | F(000) = 372 |
Triclinic, P1 | Dx = 1.316 Mg m−3 |
Hall symbol: -P 1 | Melting point: 399 K |
a = 9.702 (5) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.750 (5) Å | Cell parameters from 20 reflections |
c = 10.106 (6) Å | θ = 7–20° |
α = 83.24 (5)° | µ = 0.20 mm−1 |
β = 79.72 (4)° | T = 293 K |
γ = 72.92 (4)° | Needle, orange |
V = 897.0 (9) Å3 | 0.08 × 0.02 × 0.02 mm |
Oxford Diffraction Xcalibur CCD diffractometer | 2017 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.019 |
Graphite monochromator | θmax = 27.6°, θmin = 2.8° |
Detector resolution: Sapphire CCD detector pixels mm-1 | h = −12→12 |
Rotation method data acquisition using ω and phi scans | k = −11→12 |
6600 measured reflections | l = −11→13 |
3993 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.067 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.163 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0613P)2] where P = (Fo2 + 2Fc2)/3 |
3993 reflections | (Δ/σ)max = 0.001 |
249 parameters | Δρmax = 0.16 e Å−3 |
21 restraints | Δρmin = −0.22 e Å−3 |
C17H17N5O2S | γ = 72.92 (4)° |
Mr = 355.42 | V = 897.0 (9) Å3 |
Triclinic, P1 | Z = 2 |
a = 9.702 (5) Å | Mo Kα radiation |
b = 9.750 (5) Å | µ = 0.20 mm−1 |
c = 10.106 (6) Å | T = 293 K |
α = 83.24 (5)° | 0.08 × 0.02 × 0.02 mm |
β = 79.72 (4)° |
Oxford Diffraction Xcalibur CCD diffractometer | 2017 reflections with I > 2σ(I) |
6600 measured reflections | Rint = 0.019 |
3993 independent reflections |
R[F2 > 2σ(F2)] = 0.067 | 21 restraints |
wR(F2) = 0.163 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.16 e Å−3 |
3993 reflections | Δρmin = −0.22 e Å−3 |
249 parameters |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
N1 | 0.3368 (3) | 0.5051 (3) | 0.3631 (3) | 0.0598 (9) | |
S2 | 0.22366 (10) | 0.45907 (11) | 0.28394 (10) | 0.0565 (3) | |
C3 | 0.0691 (3) | 0.5813 (3) | 0.3510 (3) | 0.0407 (8) | |
C4 | 0.0161 (4) | 0.7698 (4) | 0.5196 (3) | 0.0468 (9) | |
H4 | −0.0842 | 0.8007 | 0.5200 | 0.056* | |
C5 | 0.0812 (4) | 0.8285 (4) | 0.5983 (3) | 0.0492 (9) | |
C6 | 0.2333 (4) | 0.7867 (4) | 0.6005 (4) | 0.0535 (10) | |
H6 | 0.2728 | 0.8331 | 0.6531 | 0.064* | |
C7 | 0.3199 (4) | 0.6803 (4) | 0.5268 (4) | 0.0546 (10) | |
H7 | 0.4194 | 0.6498 | 0.5312 | 0.065* | |
C8 | 0.2599 (4) | 0.6124 (4) | 0.4404 (3) | 0.0484 (9) | |
C9 | 0.1055 (3) | 0.6613 (3) | 0.4382 (3) | 0.0401 (8) | |
N2 | −0.0082 (4) | 0.9397 (4) | 0.6866 (3) | 0.0667 (9) | |
O1 | −0.1407 (4) | 0.9619 (4) | 0.7007 (3) | 0.0989 (11) | |
O2 | 0.0523 (3) | 1.0062 (3) | 0.7411 (3) | 0.0881 (10) | |
N3 | −0.0715 (3) | 0.6045 (3) | 0.3234 (3) | 0.0420 (7) | |
N4 | −0.0740 (3) | 0.5117 (3) | 0.2430 (3) | 0.0434 (7) | |
N5 | −0.2047 (3) | 0.5258 (3) | 0.2118 (3) | 0.0458 (7) | |
C10 | −0.2098 (4) | 0.4242 (4) | 0.1233 (3) | 0.0477 (9) | |
C11 | −0.0832 (4) | 0.3365 (4) | 0.0587 (3) | 0.0570 (10) | |
H11 | 0.0067 | 0.3460 | 0.0691 | 0.068* | |
C12 | −0.0900 (4) | 0.2347 (4) | −0.0214 (4) | 0.0612 (11) | |
H12 | −0.0038 | 0.1756 | −0.0642 | 0.073* | |
C13 | −0.2190 (5) | 0.2185 (5) | −0.0393 (4) | 0.0709 (12) | |
H13 | −0.2226 | 0.1487 | −0.0928 | 0.085* | |
C14 | −0.3440 (5) | 0.3079 (5) | 0.0236 (4) | 0.0759 (13) | |
H14 | −0.4335 | 0.2993 | 0.0104 | 0.091* | |
C15 | −0.3420 (4) | 0.4105 (4) | 0.1058 (4) | 0.0628 (11) | |
H15 | −0.4286 | 0.4692 | 0.1486 | 0.075* | |
C16 | −0.3312 (4) | 0.6387 (4) | 0.2664 (4) | 0.0580 (10) | |
H16A | −0.3220 | 0.6521 | 0.3577 | 0.070* | |
H16B | −0.4184 | 0.6081 | 0.2704 | 0.070* | |
C17 | −0.3480 (4) | 0.7801 (4) | 0.1840 (5) | 0.0844 (14) | |
H17A | −0.3426 | 0.7630 | 0.0904 | 0.101* | 0.527 (9) |
H17B | −0.2660 | 0.8157 | 0.1900 | 0.101* | 0.527 (9) |
H17C | −0.3883 | 0.7787 | 0.1032 | 0.101* | 0.473 (9) |
H17D | −0.2546 | 0.8010 | 0.1582 | 0.101* | 0.473 (9) |
C18 | −0.4867 (9) | 0.8959 (13) | 0.2239 (12) | 0.098 (4) | 0.527 (9) |
H18A | −0.5054 | 0.9665 | 0.1485 | 0.118* | 0.527 (9) |
H18B | −0.5676 | 0.8537 | 0.2457 | 0.118* | 0.527 (9) |
C19 | −0.4770 (14) | 0.9693 (14) | 0.3436 (12) | 0.138 (5) | 0.527 (9) |
H19A | −0.5112 | 0.9201 | 0.4251 | 0.208* | 0.527 (9) |
H19B | −0.5362 | 1.0672 | 0.3386 | 0.208* | 0.527 (9) |
H19C | −0.3774 | 0.9673 | 0.3433 | 0.208* | 0.527 (9) |
C18' | −0.4510 (16) | 0.8901 (11) | 0.2752 (12) | 0.117 (5) | 0.473 (9) |
H18C | −0.5408 | 0.8626 | 0.3029 | 0.141* | 0.473 (9) |
H18D | −0.4081 | 0.8865 | 0.3556 | 0.141* | 0.473 (9) |
C19' | −0.4889 (14) | 1.0431 (10) | 0.2160 (15) | 0.131 (5) | 0.473 (9) |
H19D | −0.4049 | 1.0788 | 0.2050 | 0.197* | 0.473 (9) |
H19E | −0.5669 | 1.1015 | 0.2753 | 0.197* | 0.473 (9) |
H19F | −0.5189 | 1.0467 | 0.1298 | 0.197* | 0.473 (9) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0381 (17) | 0.076 (2) | 0.066 (2) | −0.0117 (16) | −0.0037 (15) | −0.0231 (18) |
S2 | 0.0393 (5) | 0.0647 (7) | 0.0648 (7) | −0.0070 (5) | −0.0056 (4) | −0.0244 (5) |
C3 | 0.0335 (19) | 0.046 (2) | 0.040 (2) | −0.0093 (16) | −0.0029 (15) | −0.0013 (16) |
C4 | 0.039 (2) | 0.045 (2) | 0.054 (2) | −0.0075 (17) | −0.0089 (17) | −0.0024 (18) |
C5 | 0.054 (2) | 0.043 (2) | 0.048 (2) | −0.0072 (18) | −0.0077 (17) | −0.0091 (18) |
C6 | 0.057 (2) | 0.054 (2) | 0.057 (2) | −0.021 (2) | −0.0134 (19) | −0.010 (2) |
C7 | 0.042 (2) | 0.068 (3) | 0.059 (2) | −0.021 (2) | −0.0168 (18) | 0.001 (2) |
C8 | 0.036 (2) | 0.059 (2) | 0.051 (2) | −0.0147 (18) | −0.0061 (16) | −0.0024 (19) |
C9 | 0.0338 (19) | 0.045 (2) | 0.042 (2) | −0.0120 (16) | −0.0052 (15) | −0.0007 (17) |
N2 | 0.078 (3) | 0.055 (2) | 0.063 (2) | −0.007 (2) | −0.014 (2) | −0.0104 (18) |
O1 | 0.078 (2) | 0.100 (3) | 0.110 (3) | −0.001 (2) | −0.0030 (19) | −0.050 (2) |
O2 | 0.112 (3) | 0.072 (2) | 0.086 (2) | −0.0131 (18) | −0.0314 (18) | −0.0323 (17) |
N3 | 0.0357 (16) | 0.0470 (18) | 0.0436 (16) | −0.0122 (13) | −0.0056 (12) | −0.0036 (14) |
N4 | 0.0375 (16) | 0.0489 (18) | 0.0459 (17) | −0.0142 (13) | −0.0074 (13) | −0.0044 (14) |
N5 | 0.0315 (16) | 0.0578 (19) | 0.0503 (17) | −0.0144 (14) | −0.0040 (13) | −0.0115 (15) |
C10 | 0.043 (2) | 0.060 (2) | 0.044 (2) | −0.0168 (18) | −0.0093 (16) | −0.0086 (18) |
C11 | 0.048 (2) | 0.071 (3) | 0.053 (2) | −0.021 (2) | 0.0005 (18) | −0.014 (2) |
C12 | 0.058 (3) | 0.070 (3) | 0.057 (2) | −0.019 (2) | 0.0002 (19) | −0.020 (2) |
C13 | 0.078 (3) | 0.079 (3) | 0.065 (3) | −0.029 (3) | −0.011 (2) | −0.024 (2) |
C14 | 0.060 (3) | 0.092 (3) | 0.089 (3) | −0.026 (3) | −0.025 (2) | −0.027 (3) |
C15 | 0.052 (2) | 0.079 (3) | 0.065 (3) | −0.020 (2) | −0.0111 (19) | −0.024 (2) |
C16 | 0.038 (2) | 0.070 (3) | 0.070 (3) | −0.016 (2) | −0.0100 (19) | −0.015 (2) |
C17 | 0.059 (3) | 0.074 (3) | 0.119 (4) | −0.011 (2) | −0.023 (3) | −0.007 (3) |
C18 | 0.039 (5) | 0.084 (6) | 0.168 (10) | 0.005 (4) | −0.037 (5) | −0.021 (7) |
C19 | 0.129 (9) | 0.099 (10) | 0.180 (12) | −0.020 (8) | 0.003 (10) | −0.055 (9) |
C18' | 0.064 (8) | 0.096 (7) | 0.176 (12) | 0.004 (7) | −0.021 (8) | −0.006 (9) |
C19' | 0.134 (10) | 0.068 (9) | 0.166 (13) | −0.016 (7) | 0.018 (10) | 0.000 (8) |
N1—C8 | 1.337 (4) | C13—C14 | 1.367 (5) |
N1—S2 | 1.653 (3) | C13—H13 | 0.9300 |
S2—C3 | 1.705 (3) | C14—C15 | 1.381 (5) |
C3—N3 | 1.390 (4) | C14—H14 | 0.9300 |
C3—C9 | 1.394 (4) | C15—H15 | 0.9300 |
C4—C5 | 1.363 (4) | C16—C17 | 1.506 (4) |
C4—C9 | 1.400 (4) | C16—H16A | 0.9700 |
C4—H4 | 0.9300 | C16—H16B | 0.9700 |
C5—C6 | 1.415 (5) | C17—C18 | 1.506 (4) |
C5—N2 | 1.457 (5) | C17—C18' | 1.508 (5) |
C6—C7 | 1.335 (5) | C17—H17A | 0.9700 |
C6—H6 | 0.9300 | C17—H17B | 0.9700 |
C7—C8 | 1.443 (5) | C17—H17C | 0.9700 |
C7—H7 | 0.9300 | C17—H17D | 0.9700 |
C8—C9 | 1.436 (4) | C18—C19 | 1.505 (5) |
N2—O2 | 1.221 (4) | C18—H18A | 0.9700 |
N2—O1 | 1.224 (4) | C18—H18B | 0.9700 |
N3—N4 | 1.293 (3) | C19—H19A | 0.9600 |
N4—N5 | 1.325 (3) | C19—H19B | 0.9600 |
N5—C10 | 1.426 (4) | C19—H19C | 0.9600 |
N5—C16 | 1.459 (4) | C18'—C19' | 1.505 (5) |
C10—C15 | 1.372 (4) | C18'—H18C | 0.9700 |
C10—C11 | 1.376 (5) | C18'—H18D | 0.9700 |
C11—C12 | 1.374 (5) | C19'—H19D | 0.9600 |
C11—H11 | 0.9300 | C19'—H19E | 0.9600 |
C12—C13 | 1.352 (5) | C19'—H19F | 0.9600 |
C12—H12 | 0.9300 | ||
C8—N1—S2 | 108.5 (2) | C10—C15—C14 | 118.6 (4) |
N1—S2—C3 | 96.41 (16) | C10—C15—H15 | 120.7 |
N3—C3—C9 | 123.7 (3) | C14—C15—H15 | 120.7 |
N3—C3—S2 | 127.3 (2) | N5—C16—C17 | 113.0 (3) |
C9—C3—S2 | 108.9 (2) | N5—C16—H16A | 109.0 |
C5—C4—C9 | 117.7 (3) | C17—C16—H16A | 109.0 |
C5—C4—H4 | 121.2 | N5—C16—H16B | 109.0 |
C9—C4—H4 | 121.2 | C17—C16—H16B | 109.0 |
C4—C5—C6 | 123.5 (3) | H16A—C16—H16B | 107.8 |
C4—C5—N2 | 119.5 (3) | C16—C17—C18 | 115.7 (7) |
C6—C5—N2 | 117.0 (3) | C16—C17—C18' | 104.9 (6) |
C7—C6—C5 | 119.7 (3) | C16—C17—H17A | 108.4 |
C7—C6—H6 | 120.2 | C18—C17—H17A | 108.4 |
C5—C6—H6 | 120.2 | C18'—C17—H17A | 133.0 |
C6—C7—C8 | 120.3 (3) | C16—C17—H17B | 108.4 |
C6—C7—H7 | 119.8 | C18—C17—H17B | 108.4 |
C8—C7—H7 | 119.8 | C18'—C17—H17B | 92.1 |
N1—C8—C9 | 116.9 (3) | H17A—C17—H17B | 107.4 |
N1—C8—C7 | 125.1 (3) | C16—C17—H17C | 110.8 |
C9—C8—C7 | 118.0 (3) | C18—C17—H17C | 85.4 |
C3—C9—C4 | 130.1 (3) | C18'—C17—H17C | 110.8 |
C3—C9—C8 | 109.2 (3) | H17B—C17—H17C | 126.7 |
C4—C9—C8 | 120.7 (3) | C16—C17—H17D | 110.8 |
O2—N2—O1 | 123.7 (4) | C18—C17—H17D | 121.9 |
O2—N2—C5 | 118.7 (4) | C18'—C17—H17D | 110.8 |
O1—N2—C5 | 117.6 (3) | H17A—C17—H17D | 87.2 |
N4—N3—C3 | 110.3 (3) | H17C—C17—H17D | 108.8 |
N3—N4—N5 | 114.3 (3) | C19—C18—C17 | 111.4 (7) |
N4—N5—C10 | 115.1 (3) | C19—C18—H18A | 109.3 |
N4—N5—C16 | 120.6 (3) | C17—C18—H18A | 109.3 |
C10—N5—C16 | 124.2 (3) | C19—C18—H18B | 109.3 |
C15—C10—C11 | 119.6 (3) | C17—C18—H18B | 109.3 |
C15—C10—N5 | 119.7 (3) | H18A—C18—H18B | 108.0 |
C11—C10—N5 | 120.7 (3) | C19'—C18'—C17 | 116.0 (9) |
C12—C11—C10 | 120.0 (3) | C19'—C18'—H18C | 108.3 |
C12—C11—H11 | 120.0 | C17—C18'—H18C | 108.3 |
C10—C11—H11 | 120.0 | C19'—C18'—H18D | 108.3 |
C13—C12—C11 | 121.5 (4) | C17—C18'—H18D | 108.3 |
C13—C12—H12 | 119.2 | H18C—C18'—H18D | 107.4 |
C11—C12—H12 | 119.2 | C18'—C19'—H19D | 109.5 |
C12—C13—C14 | 118.0 (4) | C18'—C19'—H19E | 109.5 |
C12—C13—H13 | 121.0 | H19D—C19'—H19E | 109.5 |
C14—C13—H13 | 121.0 | C18'—C19'—H19F | 109.5 |
C13—C14—C15 | 122.3 (4) | H19D—C19'—H19F | 109.5 |
C13—C14—H14 | 118.9 | H19E—C19'—H19F | 109.5 |
C15—C14—H14 | 118.9 | ||
C8—N1—S2—C3 | 0.0 (3) | C9—C3—N3—N4 | −177.8 (3) |
N1—S2—C3—N3 | 178.1 (3) | S2—C3—N3—N4 | 4.3 (4) |
N1—S2—C3—C9 | 0.0 (3) | C3—N3—N4—N5 | 179.7 (2) |
C9—C4—C5—C6 | 0.7 (5) | N3—N4—N5—C10 | −179.9 (3) |
C9—C4—C5—N2 | −178.7 (3) | N3—N4—N5—C16 | 0.1 (4) |
C4—C5—C6—C7 | −2.8 (5) | N4—N5—C10—C15 | 167.1 (3) |
N2—C5—C6—C7 | 176.6 (3) | C16—N5—C10—C15 | −12.9 (5) |
C5—C6—C7—C8 | 2.8 (5) | N4—N5—C10—C11 | −10.8 (5) |
S2—N1—C8—C9 | 0.0 (4) | C16—N5—C10—C11 | 169.3 (3) |
S2—N1—C8—C7 | 178.9 (3) | C15—C10—C11—C12 | −0.8 (5) |
C6—C7—C8—N1 | −179.8 (4) | N5—C10—C11—C12 | 177.0 (3) |
C6—C7—C8—C9 | −0.9 (5) | C10—C11—C12—C13 | 0.4 (6) |
N3—C3—C9—C4 | 4.2 (5) | C11—C12—C13—C14 | 0.7 (6) |
S2—C3—C9—C4 | −177.6 (3) | C12—C13—C14—C15 | −1.4 (7) |
N3—C3—C9—C8 | −178.2 (3) | C11—C10—C15—C14 | 0.2 (6) |
S2—C3—C9—C8 | 0.0 (3) | N5—C10—C15—C14 | −177.7 (3) |
C5—C4—C9—C3 | 178.6 (3) | C13—C14—C15—C10 | 0.9 (6) |
C5—C4—C9—C8 | 1.2 (5) | N4—N5—C16—C17 | 85.5 (4) |
N1—C8—C9—C3 | −0.1 (4) | C10—N5—C16—C17 | −94.6 (4) |
C7—C8—C9—C3 | −179.0 (3) | N5—C16—C17—C18 | 172.3 (5) |
N1—C8—C9—C4 | 177.8 (3) | N5—C16—C17—C18' | −163.2 (8) |
C7—C8—C9—C4 | −1.2 (5) | C16—C17—C18—C19 | 80.5 (13) |
C4—C5—N2—O2 | −169.3 (3) | C18'—C17—C18—C19 | 10.9 (17) |
C6—C5—N2—O2 | 11.3 (5) | C16—C17—C18'—C19' | −179.1 (13) |
C4—C5—N2—O1 | 10.0 (5) | C18—C17—C18'—C19' | −60.0 (19) |
C6—C5—N2—O1 | −169.5 (3) |
Experimental details
Crystal data | |
Chemical formula | C17H17N5O2S |
Mr | 355.42 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 9.702 (5), 9.750 (5), 10.106 (6) |
α, β, γ (°) | 83.24 (5), 79.72 (4), 72.92 (4) |
V (Å3) | 897.0 (9) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.20 |
Crystal size (mm) | 0.08 × 0.02 × 0.02 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur CCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6600, 3993, 2017 |
Rint | 0.019 |
(sin θ/λ)max (Å−1) | 0.651 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.067, 0.163, 1.03 |
No. of reflections | 3993 |
No. of parameters | 249 |
No. of restraints | 21 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.16, −0.22 |
Computer programs: CrysAlis CCD (Oxford Diffraction Ltd, 2001', CrysAlis RED (Oxford Diffraction Ltd, 2003', CrysAlis RED', SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.
N1—C8 | 1.337 (4) | C5—N2 | 1.457 (5) |
N1—S2 | 1.653 (3) | C6—C7 | 1.335 (5) |
S2—C3 | 1.705 (3) | C7—C8 | 1.443 (5) |
C3—N3 | 1.390 (4) | C8—C9 | 1.436 (4) |
C3—C9 | 1.394 (4) | N3—N4 | 1.293 (3) |
C4—C5 | 1.363 (4) | N4—N5 | 1.325 (3) |
C4—C9 | 1.400 (4) | N5—C10 | 1.426 (4) |
C5—C6 | 1.415 (5) | N5—C16 | 1.459 (4) |
N1—S2—C3 | 96.41 (16) | N3—N4—N5 | 114.3 (3) |
N3—C3—C9 | 123.7 (3) | N4—N5—C10 | 115.1 (3) |
N3—C3—S2 | 127.3 (2) | N4—N5—C16 | 120.6 (3) |
C9—C3—S2 | 108.9 (2) | C10—N5—C16 | 124.2 (3) |
N4—N3—C3 | 110.3 (3) | ||
C4—C5—N2—O1 | 10.0 (5) | N4—N5—C16—C17 | 85.5 (4) |
S2—C3—N3—N4 | 4.3 (4) | N5—C16—C17—C18 | 172.3 (5) |
C3—N3—N4—N5 | 179.7 (2) | N5—C16—C17—C18' | −163.2 (8) |
N3—N4—N5—C10 | −179.9 (3) | C16—C17—C18—C19 | 80.5 (13) |
N3—N4—N5—C16 | 0.1 (4) | C16—C17—C18'—C19' | −179.1 (13) |
N4—N5—C10—C11 | −10.8 (5) |
1,3-Diaryltriazenes, Ar—N=N—N(R)—Ar, represent a well known class of antitumour agents which act by non-covalent interaction with B-DNA, viz. either by intercalation between the base pairs of the DNA duplex or by binding to the DNA minor groove (Vaughan, 1990; Kimball & Haley, 2002). The third type of drugs in this class exhibits the so called `mixed binding' mode in which a planar part of the drug molecule is involved in the intercalative interaction, whereas a non-planar portion(s) protrudes out of the helix interior, where it interacts with minor groove functionalities. Thus, as a part of our program aimed at developing novel anticancer drugs, we have prepared a series of derivatives, (I), in which R is an alkyl, alkoxy or hydroxyalkyl group. As detailed knowledge of the molecular structure is of central value in drug design, it is of interest to examine the extent of conjugation (i.e. planarity) in these molecules by a combined use of theoretical and experimental methods. In this communication, we report on the crystal structure of the n-butyl derivative, (Ia).
The molecular structure along with the atom-numbering scheme is shown in Fig. 1. The terminal atoms, C18 and C19, of the n-butyl chain are disordered between two positions (C18/C18' and C19/C19') with approximately equal occupancies; the disorder results from concerted rotations about the C16—C17 and C17—C18 bonds (Table 1) and gives rise to two conformers, differing mainly in the orientation (gauche and trans) of the C19 and C19' sites, respectively (Fig. 1).
As noted above, the main purpose of this work was to establish the extent of π-electron delocalization and hence the overall planarity of the molecule. As shown in Table 1, the sum of the valence angles around atom N5 is close to 120°, i.e. the formally amine N atom is sp2-hybridized, with the lone-pair electrons available for π bonding. Furthermore, the N3=N4 and N4—N5 bonds, although non-equivalent, are intermediate between a double and single bond, assuming bond lengths of 1.23 and 1.41 Å for pure N=N double and N—N single bonds, respectively (Burke-Laing & Laing, 1976). These data indicate the π-electron delocalization within the triazene linkage. That the N3=N4 double bond is delocalized through conjugation with the lone-pair electrons on atom N5 rather than the adjacent heterocyclic ring is also evidenced by (i) the C3—N3 bond distance [1.390 (4) Å], which is only slightly, though significantly, shortened relative to the value [1.425 (3) Å] found for a pure Csp2—Nsp2 single bond (Adler et al., 1976) and (ii) the pattern of bond lengths and angles within the heterocyclic ring, which is almost identical with other benzo[c]-1,2-thiazole derivatives containing substituents not involved in conjugation with the aromatic system, as revealed by a search of the Cambridge Structural Database (Allen et al., 1983). Similarly, the N5—C10 distance [1.426 (4) Å] is even identical, within experimental error, to the above value of 1.425 Å and comparable to the N5—C16 bond length [1.459 (4) Å], which is definitely deconjugated with the triazene moiety. Even though the conjugation of the triazene π system with the aromatic rings is very small, if any, both rings are aproximately coplanar with the plane of the triazene grouping; the dihedral angle between the mean planes through the 5-nitrobenzo[c]-1,2-thiazole and the triazene groups is 4.0 (3))°; the corresponding dihedral angle for the phenyl ring/triazene group is 11.9 (3)°. Thus, based on the present crystallographic data, molecule (Ia) is approximately planar as a whole, except for the n-butyl group, which is roughly perpendicular to the rest of the molecule (Table 1). However, a rather low barrier to rotation around the C—N bond linking the heterocyclic ring and the triazene group is predicted, while almost free rotation of the phenyl ring around the triazene is expected.
The crystal packing is dominated by a π–π stacking interaction between the centrosymmetricaly related molecules, which leads to the formation of dimers across the centre of symmetry. The mean interplanar separation of the planar portion of the molecules within the dimer is 3.47 Å. The stacking geometry (Fig. 2) is such that the triazene linkage of one molecule superimposes the benzo ring of the heterocyclic moiety in the other molecule. The n-butyl chains are loosely packed by van der Waals interactions, as reflected by Ueq of the C atoms, which increases on approaching the methyl termini.