Buy article online - an online subscription or single-article purchase is required to access this article.
The crystal structures of three 4-amino derivatives of 7-nitro-2,1,3-benzoxadiazole with increasing substituent ring size, viz. 7-nitro-4-(pyrrolidin-1-yl)-2,1,3-benzoxadiazole, C10H10N4O3, 7-nitro-4-(piperidin-1-yl)-2,1,3-benzoxadiazole, C11H12N4O3, and 4-(azepan-1-yl)-7-nitro-2,1,3-benzoxadiazole, C12H14N4O3, have been determined in order to understand their photophysical behaviour. All three were found to crystallize in centrosymmetric space groups. There is considerable electron delocalization compared with the parent compound, although the five-membered oxadiazole ring apparently does not participate in this. The length of the C-N bond between the amino N atom and the 7-nitrobenzoxadiazole system is found to be shorter than in similar compounds, as is the C-Nnitro bond. In each structure, the nitro group lies in the plane of the benzoxadiazole unit.
Supporting information
CCDC references: 183012; 183013; 183014
Compounds (I)-(III) were prepared according to the general procedure of Saha &
Samanta (1998). In a typical synthesis, to a solution of NBD-chloride (1 mmol)
in ethyl acetate (3 ml) cooled in an icebath was added dropwise a solution of
the amine (1.2 mmol) in ethyl acetate (2 ml). After stirring for 30 min in the
ice bath, the mixture was stirred for a further 2 h at room temperature. The
product, which appeared as a red precipitate in all cases, was filtered off
and purified by column chromatography, using a silica gel column and different
proportions of hexane and ethyl acetate as eluent. The purified compounds were
recrystallized from absolute ethanol by slow evaporation.
For all three compounds, H atoms were placed geometrically and refined using a
riding model with Ueq(H) = 1.2Ueq(C). C—H distances were
fixed at 0.97 Å for methylene H and 0.93 Å for aromatic H.
For all compounds, data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: Xtal3.5 (Hall et al., 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEX6.0 (McArdle, 1995); software used to prepare material for publication: SHELXL97.
(I) 4-nitro-7-(pyrrolidin-1-yl)-2,1,3-benzoxadiazole
top
Crystal data top
C10H10N4O3 | F(000) = 488 |
Mr = 234.22 | Dx = 1.522 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 7.0305 (12) Å | Cell parameters from 25 reflections |
b = 7.686 (2) Å | θ = 11.3–12.6° |
c = 18.951 (4) Å | µ = 0.12 mm−1 |
β = 93.69 (2)° | T = 293 K |
V = 1022.0 (4) Å3 | Plate, red |
Z = 4 | 0.70 × 0.40 × 0.20 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.2° |
Graphite monochromator | h = 0→8 |
ω scans | k = 0→9 |
1792 measured reflections | l = −22→22 |
1792 independent reflections | 3 standard reflections every 90 min |
973 reflections with I > 2σ(I) | intensity decay: none |
Refinement top
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.130 | H-atom parameters constrained |
S = 1.11 | w = 1/[σ2(Fo2) + (0.0537P)2 + 0.1481P] where P = (Fo2 + 2Fc2)/3 |
1792 reflections | (Δ/σ)max = 0.012 |
154 parameters | Δρmax = 0.17 e Å−3 |
0 restraints | Δρmin = −0.17 e Å−3 |
Crystal data top
C10H10N4O3 | V = 1022.0 (4) Å3 |
Mr = 234.22 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.0305 (12) Å | µ = 0.12 mm−1 |
b = 7.686 (2) Å | T = 293 K |
c = 18.951 (4) Å | 0.70 × 0.40 × 0.20 mm |
β = 93.69 (2)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
1792 measured reflections | 3 standard reflections every 90 min |
1792 independent reflections | intensity decay: none |
973 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.130 | H-atom parameters constrained |
S = 1.11 | Δρmax = 0.17 e Å−3 |
1792 reflections | Δρmin = −0.17 e Å−3 |
154 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
O2 | 0.2690 (3) | 0.8573 (3) | −0.09335 (10) | 0.0741 (6) | |
O3 | −0.4294 (3) | 0.5178 (3) | −0.09702 (11) | 0.0857 (7) | |
O4 | −0.2182 (3) | 0.6025 (3) | −0.16753 (11) | 0.0862 (7) | |
N1 | 0.1009 (4) | 0.7768 (3) | −0.11805 (12) | 0.0653 (7) | |
N3 | 0.2838 (3) | 0.8727 (3) | −0.02154 (11) | 0.0606 (6) | |
N4 | 0.1732 (3) | 0.8478 (3) | 0.12620 (10) | 0.0490 (6) | |
N5 | −0.2778 (4) | 0.5912 (3) | −0.10808 (13) | 0.0635 (6) | |
C1 | 0.0126 (4) | 0.7436 (3) | −0.06054 (12) | 0.0477 (6) | |
C3 | 0.1267 (3) | 0.8039 (3) | −0.00047 (12) | 0.0450 (6) | |
C4 | 0.0666 (3) | 0.7902 (3) | 0.07072 (12) | 0.0438 (6) | |
C5 | −0.1128 (4) | 0.7131 (4) | 0.07570 (13) | 0.0523 (7) | |
H5 | −0.1612 | 0.7024 | 0.1200 | 0.063* | |
C6 | −0.2204 (4) | 0.6522 (3) | 0.01718 (14) | 0.0541 (7) | |
H6 | −0.3375 | 0.6010 | 0.0243 | 0.065* | |
C7 | −0.1646 (4) | 0.6630 (3) | −0.05071 (13) | 0.0506 (7) | |
C8 | 0.1109 (4) | 0.8452 (4) | 0.19888 (13) | 0.0644 (8) | |
H8A | 0.1066 | 0.7273 | 0.2169 | 0.077* | |
H8B | −0.0139 | 0.8980 | 0.2011 | 0.077* | |
C9 | 0.2615 (5) | 0.9508 (5) | 0.23955 (15) | 0.0859 (11) | |
H9A | 0.2267 | 1.0729 | 0.2399 | 0.103* | |
H9B | 0.2798 | 0.9100 | 0.2879 | 0.103* | |
C10 | 0.4362 (5) | 0.9238 (5) | 0.20103 (15) | 0.0814 (10) | |
H10A | 0.4990 | 0.8162 | 0.2158 | 0.098* | |
H10B | 0.5247 | 1.0194 | 0.2097 | 0.098* | |
C11 | 0.3690 (4) | 0.9159 (4) | 0.12478 (13) | 0.0541 (7) | |
H11A | 0.3695 | 1.0305 | 0.1033 | 0.065* | |
H11B | 0.4483 | 0.8386 | 0.0988 | 0.065* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O2 | 0.0781 (14) | 0.0960 (16) | 0.0503 (11) | −0.0215 (12) | 0.0204 (10) | −0.0017 (11) |
O3 | 0.0661 (14) | 0.0942 (18) | 0.0944 (17) | −0.0215 (13) | −0.0123 (12) | −0.0102 (13) |
O4 | 0.1051 (18) | 0.0964 (18) | 0.0551 (13) | −0.0156 (14) | −0.0114 (12) | −0.0004 (12) |
N1 | 0.0751 (16) | 0.0708 (17) | 0.0505 (13) | −0.0076 (13) | 0.0079 (12) | −0.0022 (12) |
N3 | 0.0655 (15) | 0.0697 (16) | 0.0481 (13) | −0.0102 (12) | 0.0150 (10) | −0.0024 (11) |
N4 | 0.0518 (13) | 0.0536 (13) | 0.0421 (11) | −0.0012 (10) | 0.0062 (9) | 0.0009 (10) |
N5 | 0.0699 (17) | 0.0553 (15) | 0.0630 (16) | 0.0027 (13) | −0.0123 (13) | −0.0009 (12) |
C1 | 0.0585 (16) | 0.0430 (15) | 0.0422 (13) | 0.0086 (12) | 0.0081 (12) | 0.0051 (11) |
C3 | 0.0475 (14) | 0.0433 (15) | 0.0446 (13) | 0.0006 (12) | 0.0068 (11) | 0.0017 (11) |
C4 | 0.0472 (14) | 0.0406 (14) | 0.0442 (14) | 0.0045 (11) | 0.0065 (11) | 0.0035 (11) |
C5 | 0.0517 (15) | 0.0585 (17) | 0.0476 (14) | 0.0004 (13) | 0.0096 (11) | 0.0014 (12) |
C6 | 0.0449 (15) | 0.0533 (17) | 0.0646 (17) | 0.0004 (12) | 0.0067 (13) | 0.0018 (13) |
C7 | 0.0505 (15) | 0.0456 (15) | 0.0549 (16) | 0.0046 (12) | −0.0042 (12) | 0.0002 (12) |
C8 | 0.078 (2) | 0.072 (2) | 0.0436 (15) | −0.0106 (16) | 0.0129 (14) | 0.0018 (14) |
C9 | 0.101 (3) | 0.107 (3) | 0.0489 (17) | −0.027 (2) | 0.0033 (17) | −0.0054 (18) |
C10 | 0.080 (2) | 0.101 (3) | 0.0614 (19) | −0.017 (2) | −0.0090 (16) | 0.0035 (18) |
C11 | 0.0514 (15) | 0.0572 (17) | 0.0534 (15) | −0.0040 (13) | 0.0003 (12) | 0.0000 (13) |
Geometric parameters (Å, º) top
O2—N3 | 1.363 (3) | C5—H5 | 0.9300 |
O2—N1 | 1.388 (3) | C6—C7 | 1.371 (4) |
O3—N5 | 1.236 (3) | C6—H6 | 0.9300 |
O4—N5 | 1.230 (3) | C8—C9 | 1.506 (4) |
N1—C1 | 1.314 (4) | C8—H8A | 0.9700 |
N3—C3 | 1.310 (3) | C8—H8B | 0.9700 |
N4—C4 | 1.328 (4) | C9—C10 | 1.484 (5) |
N4—C8 | 1.472 (3) | C9—H9A | 0.9700 |
N4—C11 | 1.474 (3) | C9—H9B | 0.9700 |
N5—C7 | 1.417 (4) | C10—C11 | 1.492 (4) |
C1—C7 | 1.414 (4) | C10—H10A | 0.9700 |
C1—C3 | 1.427 (4) | C10—H10B | 0.9700 |
C3—C4 | 1.443 (3) | C11—H11A | 0.9700 |
C4—C5 | 1.402 (3) | C11—H11B | 0.9700 |
C5—C6 | 1.383 (4) | | |
| | | |
N3—O2—N1 | 112.6 (2) | C1—C7—N5 | 121.7 (3) |
C1—N1—O2 | 104.1 (2) | N4—C8—C9 | 103.3 (2) |
C3—N3—O2 | 104.9 (3) | N4—C8—H8A | 111.1 |
C4—N4—C8 | 123.3 (2) | C9—C8—H8A | 111.1 |
C4—N4—C11 | 125.8 (2) | N4—C8—H8B | 111.1 |
C8—N4—C11 | 110.9 (3) | C9—C8—H8B | 111.1 |
O4—N5—O3 | 122.4 (3) | H8A—C8—H8B | 109.1 |
O4—N5—C7 | 117.9 (3) | C10—C9—C8 | 104.5 (3) |
O3—N5—C7 | 119.7 (3) | C10—C9—H9A | 110.9 |
N1—C1—C7 | 131.4 (3) | C8—C9—H9A | 110.9 |
N1—C1—C3 | 109.1 (2) | C10—C9—H9B | 110.9 |
C7—C1—C3 | 119.5 (2) | C8—C9—H9B | 110.9 |
N3—C3—C1 | 109.2 (2) | H9A—C9—H9B | 108.9 |
N3—C3—C4 | 128.1 (3) | C9—C10—C11 | 105.1 (3) |
C1—C3—C4 | 122.6 (2) | C9—C10—H10A | 110.7 |
N4—C4—C5 | 123.5 (2) | C11—C10—H10A | 110.7 |
N4—C4—C3 | 122.1 (2) | C9—C10—H10B | 110.7 |
C5—C4—C3 | 114.4 (3) | C11—C10—H10B | 110.7 |
C6—C5—C4 | 122.5 (3) | H10A—C10—H10B | 108.8 |
C6—C5—H5 | 118.8 | N4—C11—C10 | 103.6 (3) |
C4—C5—H5 | 118.8 | N4—C11—H11A | 111.0 |
C7—C6—C5 | 123.9 (3) | C10—C11—H11A | 111.0 |
C7—C6—H6 | 118.1 | N4—C11—H11B | 111.0 |
C5—C6—H6 | 118.1 | C10—C11—H11B | 111.0 |
C6—C7—C1 | 117.2 (3) | H11A—C11—H11B | 109.0 |
C6—C7—N5 | 121.1 (3) | | |
| | | |
N3—O2—N1—C1 | 0.2 (3) | C3—C4—C5—C6 | 1.3 (4) |
N1—O2—N3—C3 | −0.3 (3) | C4—C5—C6—C7 | −0.9 (4) |
O2—N1—C1—C7 | −179.8 (3) | C5—C6—C7—C1 | −0.9 (4) |
O2—N1—C1—C3 | 0.0 (3) | C5—C6—C7—N5 | 177.2 (2) |
O2—N3—C3—C1 | 0.3 (3) | N1—C1—C7—C6 | −178.1 (3) |
O2—N3—C3—C4 | −178.3 (2) | C3—C1—C7—C6 | 2.1 (3) |
N1—C1—C3—N3 | −0.2 (3) | N1—C1—C7—N5 | 3.9 (4) |
C7—C1—C3—N3 | 179.7 (2) | C3—C1—C7—N5 | −176.0 (2) |
N1—C1—C3—C4 | 178.5 (2) | O4—N5—C7—C6 | −178.7 (2) |
C7—C1—C3—C4 | −1.7 (4) | O3—N5—C7—C6 | 0.1 (4) |
C8—N4—C4—C5 | −3.2 (4) | O4—N5—C7—C1 | −0.7 (4) |
C11—N4—C4—C5 | 174.4 (2) | O3—N5—C7—C1 | 178.1 (2) |
C8—N4—C4—C3 | 176.2 (2) | C4—N4—C8—C9 | −170.2 (3) |
C11—N4—C4—C3 | −6.2 (4) | C11—N4—C8—C9 | 11.8 (3) |
N3—C3—C4—N4 | −1.1 (4) | N4—C8—C9—C10 | −29.3 (3) |
C1—C3—C4—N4 | −179.5 (2) | C8—C9—C10—C11 | 36.5 (4) |
N3—C3—C4—C5 | 178.4 (3) | C4—N4—C11—C10 | −167.7 (3) |
C1—C3—C4—C5 | 0.0 (3) | C8—N4—C11—C10 | 10.1 (3) |
N4—C4—C5—C6 | −179.3 (2) | C9—C10—C11—N4 | −28.6 (3) |
(II) 4-nitro-7-(piperidin-1-yl)-2,1,3-benzoxadiazole
top
Crystal data top
C11H12N4O3 | F(000) = 520 |
Mr = 248.25 | Dx = 1.475 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 6.7644 (19) Å | Cell parameters from 25 reflections |
b = 21.277 (6) Å | θ = 7.8–10.4° |
c = 7.788 (6) Å | µ = 0.11 mm−1 |
β = 94.22 (5)° | T = 293 K |
V = 1117.8 (10) Å3 | Plate, red |
Z = 4 | 0.40 × 0.29 × 0.16 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.137 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 1.9° |
Graphite monochromator | h = 0→8 |
ω scans | k = 0→25 |
2122 measured reflections | l = −9→9 |
1955 independent reflections | 3 standard reflections every 90 min |
732 reflections with I > 2σ(I) | intensity decay: none |
Refinement top
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)] = 0.069 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.224 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0751P)2] where P = (Fo2 + 2Fc2)/3 |
1955 reflections | (Δ/σ)max = 0.005 |
163 parameters | Δρmax = 0.25 e Å−3 |
0 restraints | Δρmin = −0.28 e Å−3 |
Crystal data top
C11H12N4O3 | V = 1117.8 (10) Å3 |
Mr = 248.25 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 6.7644 (19) Å | µ = 0.11 mm−1 |
b = 21.277 (6) Å | T = 293 K |
c = 7.788 (6) Å | 0.40 × 0.29 × 0.16 mm |
β = 94.22 (5)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.137 |
2122 measured reflections | 3 standard reflections every 90 min |
1955 independent reflections | intensity decay: none |
732 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.069 | 0 restraints |
wR(F2) = 0.224 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.25 e Å−3 |
1955 reflections | Δρmin = −0.28 e Å−3 |
163 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
O2 | 1.2708 (6) | 0.1956 (2) | 0.5115 (5) | 0.0705 (13) | |
O3 | 0.8613 (7) | 0.41196 (19) | 0.2956 (6) | 0.0708 (13) | |
O4 | 1.1369 (7) | 0.3836 (2) | 0.4337 (6) | 0.0762 (14) | |
N1 | 1.2214 (7) | 0.2591 (2) | 0.4846 (7) | 0.0627 (15) | |
N3 | 1.1279 (7) | 0.1568 (2) | 0.4370 (6) | 0.0597 (14) | |
N4 | 0.7555 (7) | 0.1166 (2) | 0.2282 (6) | 0.0520 (13) | |
N5 | 0.9771 (8) | 0.3714 (2) | 0.3535 (6) | 0.0555 (13) | |
C1 | 1.0516 (8) | 0.2576 (3) | 0.3919 (7) | 0.0464 (14) | |
C3 | 0.9927 (7) | 0.1935 (3) | 0.3611 (6) | 0.0396 (13) | |
C4 | 0.8069 (8) | 0.1761 (3) | 0.2639 (7) | 0.0427 (13) | |
C5 | 0.6909 (8) | 0.2287 (3) | 0.2131 (7) | 0.0500 (15) | |
H5 | 0.5673 | 0.2218 | 0.1557 | 0.060* | |
C6 | 0.7508 (8) | 0.2900 (3) | 0.2441 (7) | 0.0512 (16) | |
H6 | 0.6664 | 0.3221 | 0.2035 | 0.061* | |
C7 | 0.9263 (8) | 0.3065 (3) | 0.3306 (6) | 0.0433 (13) | |
C8 | 0.5635 (8) | 0.1013 (3) | 0.1391 (8) | 0.0626 (18) | |
H8A | 0.5831 | 0.0865 | 0.0239 | 0.075* | |
H8B | 0.4820 | 0.1389 | 0.1292 | 0.075* | |
C9 | 0.4588 (8) | 0.0514 (3) | 0.2361 (8) | 0.0561 (16) | |
H9A | 0.4207 | 0.0688 | 0.3440 | 0.067* | |
H9B | 0.3389 | 0.0388 | 0.1689 | 0.067* | |
C10 | 0.5864 (8) | −0.0050 (3) | 0.2723 (7) | 0.0534 (15) | |
H10A | 0.6073 | −0.0263 | 0.1650 | 0.064* | |
H10B | 0.5193 | −0.0339 | 0.3447 | 0.064* | |
C11 | 0.7837 (8) | 0.0128 (3) | 0.3607 (7) | 0.0536 (15) | |
H11A | 0.8671 | −0.0242 | 0.3739 | 0.064* | |
H11B | 0.7645 | 0.0292 | 0.4745 | 0.064* | |
C12 | 0.8844 (7) | 0.0617 (3) | 0.2572 (7) | 0.0496 (15) | |
H12A | 1.0080 | 0.0744 | 0.3185 | 0.060* | |
H12B | 0.9147 | 0.0441 | 0.1474 | 0.060* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O2 | 0.053 (3) | 0.079 (3) | 0.075 (3) | 0.004 (2) | −0.022 (2) | −0.008 (3) |
O3 | 0.082 (3) | 0.056 (3) | 0.075 (3) | 0.008 (2) | 0.006 (3) | 0.002 (2) |
O4 | 0.071 (3) | 0.072 (3) | 0.084 (3) | −0.022 (2) | −0.010 (3) | −0.010 (3) |
N1 | 0.053 (3) | 0.072 (4) | 0.061 (3) | 0.006 (3) | −0.004 (3) | −0.007 (3) |
N3 | 0.043 (3) | 0.070 (3) | 0.064 (3) | −0.001 (3) | −0.015 (2) | −0.014 (3) |
N4 | 0.042 (3) | 0.056 (3) | 0.056 (3) | −0.002 (2) | −0.007 (2) | 0.000 (3) |
N5 | 0.064 (4) | 0.055 (3) | 0.048 (3) | −0.002 (3) | 0.008 (3) | −0.001 (3) |
C1 | 0.038 (3) | 0.062 (4) | 0.039 (3) | −0.005 (3) | 0.000 (3) | −0.005 (3) |
C3 | 0.030 (3) | 0.053 (3) | 0.035 (3) | 0.006 (3) | 0.002 (2) | −0.004 (3) |
C4 | 0.037 (3) | 0.056 (4) | 0.035 (3) | 0.003 (3) | 0.003 (2) | −0.004 (3) |
C5 | 0.045 (3) | 0.059 (4) | 0.045 (3) | 0.001 (3) | −0.006 (3) | −0.004 (3) |
C6 | 0.053 (4) | 0.061 (4) | 0.039 (3) | 0.003 (3) | −0.002 (3) | 0.008 (3) |
C7 | 0.042 (3) | 0.051 (3) | 0.037 (3) | −0.007 (3) | 0.004 (3) | −0.004 (3) |
C8 | 0.043 (3) | 0.063 (4) | 0.079 (5) | −0.002 (3) | −0.014 (3) | −0.003 (4) |
C9 | 0.041 (3) | 0.069 (4) | 0.058 (4) | −0.005 (3) | −0.001 (3) | −0.012 (3) |
C10 | 0.049 (3) | 0.065 (4) | 0.047 (4) | −0.001 (3) | 0.005 (3) | −0.005 (3) |
C11 | 0.054 (4) | 0.058 (4) | 0.048 (3) | 0.004 (3) | −0.002 (3) | −0.002 (3) |
C12 | 0.039 (3) | 0.054 (4) | 0.056 (4) | 0.000 (3) | −0.001 (3) | −0.007 (3) |
Geometric parameters (Å, º) top
O2—N3 | 1.368 (6) | C6—C7 | 1.367 (7) |
O2—N1 | 1.402 (6) | C6—H6 | 0.9300 |
O3—N5 | 1.229 (6) | C8—C9 | 1.510 (8) |
O4—N5 | 1.235 (6) | C8—H8A | 0.9700 |
N1—C1 | 1.311 (6) | C8—H8B | 0.9700 |
N3—C3 | 1.310 (6) | C9—C10 | 1.493 (7) |
N4—C4 | 1.337 (6) | C9—H9A | 0.9700 |
N4—C8 | 1.463 (6) | C9—H9B | 0.9700 |
N4—C12 | 1.465 (6) | C10—C11 | 1.503 (7) |
N5—C7 | 1.431 (7) | C10—H10A | 0.9700 |
C1—C7 | 1.402 (7) | C10—H10B | 0.9700 |
C1—C3 | 1.437 (7) | C11—C12 | 1.510 (7) |
C3—C4 | 1.466 (7) | C11—H11A | 0.9700 |
C4—C5 | 1.406 (7) | C11—H11B | 0.9700 |
C5—C6 | 1.382 (7) | C12—H12A | 0.9700 |
C5—H5 | 0.9300 | C12—H12B | 0.9700 |
| | | |
N3—O2—N1 | 111.4 (4) | C9—C8—H8A | 109.5 |
C1—N1—O2 | 104.4 (5) | N4—C8—H8B | 109.5 |
C3—N3—O2 | 106.2 (5) | C9—C8—H8B | 109.5 |
C4—N4—C8 | 121.2 (5) | H8A—C8—H8B | 108.1 |
C4—N4—C12 | 125.5 (4) | C10—C9—C8 | 112.0 (5) |
C8—N4—C12 | 113.2 (4) | C10—C9—H9A | 109.2 |
O3—N5—O4 | 123.3 (5) | C8—C9—H9A | 109.2 |
O3—N5—C7 | 119.4 (5) | C10—C9—H9B | 109.2 |
O4—N5—C7 | 117.3 (5) | C8—C9—H9B | 109.2 |
N1—C1—C7 | 130.8 (5) | H9A—C9—H9B | 107.9 |
N1—C1—C3 | 109.6 (5) | C9—C10—C11 | 111.5 (5) |
C7—C1—C3 | 119.6 (5) | C9—C10—H10A | 109.3 |
N3—C3—C1 | 108.3 (5) | C11—C10—H10A | 109.3 |
N3—C3—C4 | 128.8 (5) | C9—C10—H10B | 109.3 |
C1—C3—C4 | 122.8 (5) | C11—C10—H10B | 109.3 |
N4—C4—C5 | 124.3 (5) | H10A—C10—H10B | 108.0 |
N4—C4—C3 | 123.1 (5) | C10—C11—C12 | 110.4 (5) |
C5—C4—C3 | 112.6 (5) | C10—C11—H11A | 109.6 |
C6—C5—C4 | 123.5 (5) | C12—C11—H11A | 109.6 |
C6—C5—H5 | 118.3 | C10—C11—H11B | 109.6 |
C4—C5—H5 | 118.3 | C12—C11—H11B | 109.6 |
C7—C6—C5 | 124.1 (5) | H11A—C11—H11B | 108.1 |
C7—C6—H6 | 118.0 | N4—C12—C11 | 110.2 (4) |
C5—C6—H6 | 118.0 | N4—C12—H12A | 109.6 |
C6—C7—C1 | 117.3 (5) | C11—C12—H12A | 109.6 |
C6—C7—N5 | 120.0 (5) | N4—C12—H12B | 109.6 |
C1—C7—N5 | 122.6 (5) | C11—C12—H12B | 109.6 |
N4—C8—C9 | 110.6 (5) | H12A—C12—H12B | 108.1 |
N4—C8—H8A | 109.5 | | |
| | | |
N3—O2—N1—C1 | −1.1 (6) | C4—C5—C6—C7 | −1.7 (9) |
N1—O2—N3—C3 | 1.3 (6) | C5—C6—C7—C1 | −0.3 (8) |
O2—N1—C1—C7 | 177.4 (5) | C5—C6—C7—N5 | 178.8 (5) |
O2—N1—C1—C3 | 0.4 (6) | N1—C1—C7—C6 | −176.4 (6) |
O2—N3—C3—C1 | −1.0 (6) | C3—C1—C7—C6 | 0.4 (7) |
O2—N3—C3—C4 | −179.3 (5) | N1—C1—C7—N5 | 4.5 (9) |
N1—C1—C3—N3 | 0.4 (6) | C3—C1—C7—N5 | −178.7 (5) |
C7—C1—C3—N3 | −177.0 (5) | O3—N5—C7—C6 | 0.4 (8) |
N1—C1—C3—C4 | 178.8 (5) | O4—N5—C7—C6 | 179.5 (5) |
C7—C1—C3—C4 | 1.4 (8) | O3—N5—C7—C1 | 179.5 (5) |
C8—N4—C4—C5 | −3.5 (9) | O4—N5—C7—C1 | −1.4 (8) |
C12—N4—C4—C5 | 170.6 (5) | C4—N4—C8—C9 | −129.1 (5) |
C8—N4—C4—C3 | 176.5 (5) | C12—N4—C8—C9 | 56.1 (6) |
C12—N4—C4—C3 | −9.3 (9) | N4—C8—C9—C10 | −52.9 (6) |
N3—C3—C4—N4 | −5.1 (9) | C8—C9—C10—C11 | 53.1 (6) |
C1—C3—C4—N4 | 176.9 (5) | C9—C10—C11—C12 | −54.5 (6) |
N3—C3—C4—C5 | 175.0 (5) | C4—N4—C12—C11 | 127.3 (6) |
C1—C3—C4—C5 | −3.0 (8) | C8—N4—C12—C11 | −58.1 (6) |
N4—C4—C5—C6 | −176.8 (5) | C10—C11—C12—N4 | 56.2 (6) |
C3—C4—C5—C6 | 3.1 (8) | | |
(III) 4-(azepan-1-yl)-7-nitro-2,1,3-benzoxadiazole
top
Crystal data top
C12H14N4O3 | F(000) = 552 |
Mr = 262.27 | Dx = 1.444 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 7.4909 (16) Å | Cell parameters from 25 reflections |
b = 10.8002 (14) Å | θ = 9.3–10.6° |
c = 15.1001 (19) Å | µ = 0.11 mm−1 |
β = 98.958 (14)° | T = 293 K |
V = 1206.7 (3) Å3 | Plate, red |
Z = 4 | 0.32 × 0.21 × 0.10 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.3° |
Graphite monochromator | h = 0→8 |
ω scans | k = 0→12 |
2115 measured reflections | l = −17→17 |
2115 independent reflections | 3 standard reflections every 90 min |
1043 reflections with I > 2σ(I) | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.051 | H-atom parameters constrained |
wR(F2) = 0.174 | w = 1/[σ2(Fo2) + (0.0918P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max = 0.001 |
2115 reflections | Δρmax = 0.22 e Å−3 |
173 parameters | Δρmin = −0.20 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.010 (3) |
Crystal data top
C12H14N4O3 | V = 1206.7 (3) Å3 |
Mr = 262.27 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.4909 (16) Å | µ = 0.11 mm−1 |
b = 10.8002 (14) Å | T = 293 K |
c = 15.1001 (19) Å | 0.32 × 0.21 × 0.10 mm |
β = 98.958 (14)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
2115 measured reflections | 3 standard reflections every 90 min |
2115 independent reflections | intensity decay: none |
1043 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.051 | 0 restraints |
wR(F2) = 0.174 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.22 e Å−3 |
2115 reflections | Δρmin = −0.20 e Å−3 |
173 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
O2 | 0.8728 (4) | −0.1494 (2) | 0.06047 (15) | 0.0596 (7) | |
O3 | 0.4812 (4) | −0.0492 (2) | −0.27555 (16) | 0.0706 (8) | |
O4 | 0.6308 (4) | −0.1977 (2) | −0.20052 (18) | 0.0749 (9) | |
N1 | 0.7892 (4) | −0.1647 (2) | −0.02781 (18) | 0.0523 (8) | |
N3 | 0.8594 (4) | −0.0311 (2) | 0.09053 (17) | 0.0503 (8) | |
N4 | 0.7419 (4) | 0.2345 (2) | 0.08964 (17) | 0.0465 (7) | |
N5 | 0.5748 (4) | −0.0910 (3) | −0.20698 (18) | 0.0533 (8) | |
C1 | 0.7237 (4) | −0.0540 (3) | −0.0513 (2) | 0.0398 (7) | |
C3 | 0.7682 (4) | 0.0303 (3) | 0.02302 (19) | 0.0382 (7) | |
C4 | 0.7099 (4) | 0.1577 (3) | 0.0190 (2) | 0.0426 (8) | |
C5 | 0.6087 (5) | 0.1927 (3) | −0.0638 (2) | 0.0493 (9) | |
H5 | 0.5680 | 0.2739 | −0.0710 | 0.059* | |
C6 | 0.5672 (4) | 0.1114 (3) | −0.1349 (2) | 0.0483 (8) | |
H6 | 0.4989 | 0.1408 | −0.1875 | 0.058* | |
C7 | 0.6217 (4) | −0.0107 (3) | −0.13214 (19) | 0.0446 (8) | |
C8 | 0.6450 (5) | 0.3529 (3) | 0.0889 (3) | 0.0588 (10) | |
H8A | 0.6238 | 0.3713 | 0.1493 | 0.071* | |
H8B | 0.5283 | 0.3447 | 0.0513 | 0.071* | |
C9 | 0.7461 (6) | 0.4605 (3) | 0.0551 (3) | 0.0702 (12) | |
H9A | 0.7917 | 0.4345 | 0.0013 | 0.084* | |
H9B | 0.6616 | 0.5277 | 0.0385 | 0.084* | |
C10 | 0.9029 (6) | 0.5090 (3) | 0.1219 (3) | 0.0740 (12) | |
H10A | 0.9660 | 0.5715 | 0.0926 | 0.089* | |
H10B | 0.8548 | 0.5490 | 0.1706 | 0.089* | |
C11 | 1.0379 (5) | 0.4115 (3) | 0.1611 (3) | 0.0688 (11) | |
H11A | 1.1400 | 0.4523 | 0.1968 | 0.083* | |
H11B | 1.0825 | 0.3688 | 0.1124 | 0.083* | |
C12 | 0.9609 (5) | 0.3161 (3) | 0.2194 (3) | 0.0620 (10) | |
H12A | 1.0582 | 0.2871 | 0.2646 | 0.074* | |
H12B | 0.8734 | 0.3572 | 0.2503 | 0.074* | |
C13 | 0.8711 (5) | 0.2050 (3) | 0.1709 (2) | 0.0560 (9) | |
H13A | 0.9640 | 0.1511 | 0.1543 | 0.067* | |
H13B | 0.8079 | 0.1594 | 0.2120 | 0.067* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O2 | 0.0781 (17) | 0.0429 (13) | 0.0536 (14) | 0.0124 (12) | −0.0033 (13) | 0.0003 (11) |
O3 | 0.0793 (19) | 0.0814 (19) | 0.0446 (14) | −0.0087 (15) | −0.0110 (14) | 0.0003 (13) |
O4 | 0.096 (2) | 0.0536 (16) | 0.0683 (18) | 0.0026 (15) | −0.0074 (15) | −0.0182 (13) |
N1 | 0.0625 (19) | 0.0471 (17) | 0.0459 (16) | 0.0037 (14) | 0.0039 (14) | −0.0012 (13) |
N3 | 0.0648 (19) | 0.0384 (15) | 0.0454 (15) | 0.0111 (14) | 0.0014 (14) | 0.0014 (12) |
N4 | 0.0513 (16) | 0.0389 (15) | 0.0475 (15) | 0.0031 (12) | 0.0022 (13) | −0.0007 (12) |
N5 | 0.0519 (18) | 0.062 (2) | 0.0448 (17) | −0.0109 (15) | 0.0033 (14) | −0.0028 (14) |
C1 | 0.0383 (17) | 0.0390 (17) | 0.0432 (17) | 0.0035 (14) | 0.0101 (14) | 0.0004 (14) |
C3 | 0.0399 (17) | 0.0365 (16) | 0.0383 (16) | 0.0024 (14) | 0.0062 (14) | 0.0044 (13) |
C4 | 0.0427 (18) | 0.0406 (17) | 0.0449 (17) | 0.0007 (14) | 0.0085 (14) | 0.0017 (15) |
C5 | 0.054 (2) | 0.0419 (18) | 0.049 (2) | 0.0092 (16) | −0.0005 (16) | 0.0076 (15) |
C6 | 0.048 (2) | 0.0496 (19) | 0.0441 (18) | −0.0006 (16) | −0.0020 (15) | 0.0089 (15) |
C7 | 0.0399 (18) | 0.0536 (19) | 0.0390 (17) | −0.0024 (15) | 0.0025 (14) | 0.0027 (15) |
C8 | 0.052 (2) | 0.0454 (19) | 0.076 (2) | 0.0111 (17) | 0.0037 (19) | −0.0055 (18) |
C9 | 0.078 (3) | 0.044 (2) | 0.085 (3) | 0.011 (2) | 0.004 (2) | 0.0040 (19) |
C10 | 0.073 (3) | 0.047 (2) | 0.106 (3) | −0.006 (2) | 0.024 (2) | −0.014 (2) |
C11 | 0.058 (2) | 0.058 (2) | 0.090 (3) | −0.007 (2) | 0.008 (2) | −0.018 (2) |
C12 | 0.067 (2) | 0.058 (2) | 0.060 (2) | 0.0007 (19) | 0.0033 (19) | −0.0159 (18) |
C13 | 0.067 (2) | 0.053 (2) | 0.0459 (19) | 0.0031 (18) | 0.0000 (18) | 0.0011 (16) |
Geometric parameters (Å, º) top
O2—N3 | 1.365 (3) | C8—C9 | 1.518 (5) |
O2—N1 | 1.392 (4) | C8—H8A | 0.9700 |
O3—N5 | 1.242 (3) | C8—H8B | 0.9700 |
O4—N5 | 1.226 (4) | C9—C10 | 1.518 (6) |
N1—C1 | 1.320 (4) | C9—H9A | 0.9700 |
N3—C3 | 1.314 (4) | C9—H9B | 0.9700 |
N4—C4 | 1.344 (4) | C10—C11 | 1.515 (5) |
N4—C8 | 1.469 (4) | C10—H10A | 0.9700 |
N4—C13 | 1.475 (4) | C10—H10B | 0.9700 |
N5—C7 | 1.424 (4) | C11—C12 | 1.526 (5) |
C1—C7 | 1.415 (4) | C11—H11A | 0.9700 |
C1—C3 | 1.443 (4) | C11—H11B | 0.9700 |
C3—C4 | 1.442 (4) | C12—C13 | 1.508 (5) |
C4—C5 | 1.409 (4) | C12—H12A | 0.9700 |
C5—C6 | 1.384 (4) | C12—H12B | 0.9700 |
C5—H5 | 0.9300 | C13—H13A | 0.9700 |
C6—C7 | 1.379 (4) | C13—H13B | 0.9700 |
C6—H6 | 0.9300 | | |
| | | |
N3—O2—N1 | 112.6 (2) | H8A—C8—H8B | 107.7 |
C1—N1—O2 | 104.0 (2) | C10—C9—C8 | 114.5 (3) |
C3—N3—O2 | 105.7 (2) | C10—C9—H9A | 108.6 |
C4—N4—C8 | 120.3 (3) | C8—C9—H9A | 108.6 |
C4—N4—C13 | 122.7 (3) | C10—C9—H9B | 108.6 |
C8—N4—C13 | 117.0 (3) | C8—C9—H9B | 108.6 |
O4—N5—O3 | 123.4 (3) | H9A—C9—H9B | 107.6 |
O4—N5—C7 | 118.1 (3) | C11—C10—C9 | 114.9 (3) |
O3—N5—C7 | 118.5 (3) | C11—C10—H10A | 108.6 |
N1—C1—C7 | 131.2 (3) | C9—C10—H10A | 108.6 |
N1—C1—C3 | 109.3 (3) | C11—C10—H10B | 108.6 |
C7—C1—C3 | 119.4 (3) | C9—C10—H10B | 108.6 |
N3—C3—C4 | 129.1 (3) | H10A—C10—H10B | 107.5 |
N3—C3—C1 | 108.3 (3) | C10—C11—C12 | 113.9 (3) |
C4—C3—C1 | 122.5 (3) | C10—C11—H11A | 108.8 |
N4—C4—C5 | 122.9 (3) | C12—C11—H11A | 108.8 |
N4—C4—C3 | 122.7 (3) | C10—C11—H11B | 108.8 |
C5—C4—C3 | 114.3 (3) | C12—C11—H11B | 108.8 |
C6—C5—C4 | 122.9 (3) | H11A—C11—H11B | 107.7 |
C6—C5—H5 | 118.6 | C13—C12—C11 | 116.0 (3) |
C4—C5—H5 | 118.6 | C13—C12—H12A | 108.3 |
C7—C6—C5 | 123.6 (3) | C11—C12—H12A | 108.3 |
C7—C6—H6 | 118.2 | C13—C12—H12B | 108.3 |
C5—C6—H6 | 118.2 | C11—C12—H12B | 108.3 |
C6—C7—C1 | 117.4 (3) | H12A—C12—H12B | 107.4 |
C6—C7—N5 | 121.5 (3) | N4—C13—C12 | 114.6 (3) |
C1—C7—N5 | 121.1 (3) | N4—C13—H13A | 108.6 |
N4—C8—C9 | 113.4 (3) | C12—C13—H13A | 108.6 |
N4—C8—H8A | 108.9 | N4—C13—H13B | 108.6 |
C9—C8—H8A | 108.9 | C12—C13—H13B | 108.6 |
N4—C8—H8B | 108.9 | H13A—C13—H13B | 107.6 |
C9—C8—H8B | 108.9 | | |
| | | |
N3—O2—N1—C1 | −0.2 (4) | C4—C5—C6—C7 | −0.6 (5) |
N1—O2—N3—C3 | 0.1 (4) | C5—C6—C7—C1 | 0.7 (5) |
O2—N1—C1—C7 | −178.6 (3) | C5—C6—C7—N5 | 179.7 (3) |
O2—N1—C1—C3 | 0.3 (3) | N1—C1—C7—C6 | 177.8 (3) |
O2—N3—C3—C4 | 177.5 (3) | C3—C1—C7—C6 | −1.0 (4) |
O2—N3—C3—C1 | 0.1 (3) | N1—C1—C7—N5 | −1.1 (5) |
N1—C1—C3—N3 | −0.3 (4) | C3—C1—C7—N5 | −179.9 (3) |
C7—C1—C3—N3 | 178.8 (3) | O4—N5—C7—C6 | 178.5 (3) |
N1—C1—C3—C4 | −177.9 (3) | O3—N5—C7—C6 | −0.7 (5) |
C7—C1—C3—C4 | 1.1 (4) | O4—N5—C7—C1 | −2.6 (5) |
C8—N4—C4—C5 | 10.9 (5) | O3—N5—C7—C1 | 178.2 (3) |
C13—N4—C4—C5 | −169.9 (3) | C4—N4—C8—C9 | −93.0 (4) |
C8—N4—C4—C3 | −165.7 (3) | C13—N4—C8—C9 | 87.8 (4) |
C13—N4—C4—C3 | 13.4 (5) | N4—C8—C9—C10 | −76.2 (4) |
N3—C3—C4—N4 | −1.1 (5) | C8—C9—C10—C11 | 52.7 (5) |
C1—C3—C4—N4 | 176.0 (3) | C9—C10—C11—C12 | −65.6 (5) |
N3—C3—C4—C5 | −178.0 (3) | C10—C11—C12—C13 | 87.6 (4) |
C1—C3—C4—C5 | −0.9 (4) | C4—N4—C13—C12 | 150.0 (3) |
N4—C4—C5—C6 | −176.3 (3) | C8—N4—C13—C12 | −30.8 (4) |
C3—C4—C5—C6 | 0.6 (5) | C11—C12—C13—N4 | −47.6 (5) |
Experimental details
| (I) | (II) | (III) |
Crystal data |
Chemical formula | C10H10N4O3 | C11H12N4O3 | C12H14N4O3 |
Mr | 234.22 | 248.25 | 262.27 |
Crystal system, space group | Monoclinic, P21/c | Monoclinic, P21/c | Monoclinic, P21/c |
Temperature (K) | 293 | 293 | 293 |
a, b, c (Å) | 7.0305 (12), 7.686 (2), 18.951 (4) | 6.7644 (19), 21.277 (6), 7.788 (6) | 7.4909 (16), 10.8002 (14), 15.1001 (19) |
β (°) | 93.69 (2) | 94.22 (5) | 98.958 (14) |
V (Å3) | 1022.0 (4) | 1117.8 (10) | 1206.7 (3) |
Z | 4 | 4 | 4 |
Radiation type | Mo Kα | Mo Kα | Mo Kα |
µ (mm−1) | 0.12 | 0.11 | 0.11 |
Crystal size (mm) | 0.70 × 0.40 × 0.20 | 0.40 × 0.29 × 0.16 | 0.32 × 0.21 × 0.10 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | – | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1792, 1792, 973 | 2122, 1955, 732 | 2115, 2115, 1043 |
Rint | 0.000 | 0.137 | 0.000 |
(sin θ/λ)max (Å−1) | 0.594 | 0.594 | 0.594 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.130, 1.11 | 0.069, 0.224, 1.05 | 0.051, 0.174, 1.03 |
No. of reflections | 1792 | 1955 | 2115 |
No. of parameters | 154 | 163 | 173 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.17, −0.17 | 0.25, −0.28 | 0.22, −0.20 |
Selected geometric parameters (Å, º) for (I) topN4—C4 | 1.328 (4) | N5—C7 | 1.417 (4) |
| | | |
C4—N4—C8 | 123.3 (2) | C8—N4—C11 | 110.9 (3) |
C4—N4—C11 | 125.8 (2) | | |
| | | |
C8—N4—C4—C5 | −3.2 (4) | O3—N5—C7—C6 | 0.1 (4) |
Selected geometric parameters (Å, º) for (II) topN4—C4 | 1.337 (6) | N5—C7 | 1.431 (7) |
| | | |
C4—N4—C8 | 121.2 (5) | C8—N4—C12 | 113.2 (4) |
C4—N4—C12 | 125.5 (4) | | |
| | | |
C8—N4—C4—C5 | −3.5 (9) | O3—N5—C7—C6 | 0.4 (8) |
Selected geometric parameters (Å, º) for (III) topN4—C4 | 1.344 (4) | N5—C7 | 1.424 (4) |
| | | |
C4—N4—C8 | 120.3 (3) | C8—N4—C13 | 117.0 (3) |
C4—N4—C13 | 122.7 (3) | | |
| | | |
C8—N4—C4—C5 | 10.9 (5) | O3—N5—C7—C6 | −0.7 (5) |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
If you have already registered and are using a computer listed in your registration details, please email
support@iucr.org for assistance.
Although 4-amino derivatives of 7-nitro-2,1,3-benzoxadiazole (NBD) are considered to be highly efficient fluorophores and have wide applications (Chattopadhyay, 1990), so far only a few crystal structures of these have been reported (Saha & Samanta, 1999a). As benzoxadiazole is considered a complex heterocyclic moiety, the standard input data for initial parameterization for sophisticated theoretical calculations are yet not available. Crystal structure determinations also provide information about whether a crystal exhibits nonlinear optical (NLO) activity: a non-centrosymmetric crystal is a precondition for second-order NLO activity.
It has been shown (Suzuki et al., 1988) that 4-chloro-7-nitrobenzoxadiazole (NBD-chloride) is NLO active. Although the Cl is thought to be part of the π-system and has some electron-donating capacity, the double bonds in the six-membered ring of the benzoxadiazole moiety are localized, i.e. no resonance is detected. It was therefore of interest to determine the structure when this benzoxadiazole unit is attached to a strongly electron-donating group, such as amine, so we report here the crystal structures of three new 4-amino NBD derivatives, 4-nitro-7-(pyrrolidin-1-yl)-2,1,3-benzoxadiazole, (I), 4-nitro-7-(piperidin-1-yl)-2,1,3-benzoxadiazole, (II), and 4-(azepan-1-yl)-7-nitro-2,1,3-benzoxadiazole, (III). \sch
In addition, to follow the details of the structural changes in the intramolecular charge-transfer (ICT) state that accompanies and governs the excited state ICT process, knowledge of ground state crystal structure is important. The present studies were also carried out in order to obtain information on the electron flow and its direction, the change in the order of the C4—N4 bond that connects the amine moiety to the benzoxadiazole subunit in the three derivatives, the pyramidality of the amine N atom, and the change of twist angle with change of substituent amine. It is known that the character of the C4—N4 bond and the configuration of amine N atom determine the photophysical properties of some donor-acceptor (D—A) molecules (Saha & Samanta, 1998). It is also known that the ground state twist angle can be a useful predictor of the excited state conformation (Saha & Samanta, 1999b).
The molecular structures of compounds (I)-(III) are shown in Figs. 1–3, respectively. Unlike the parent compound NBD-chloride, derivatives (I)-(III) are centrosymmetric and show considerable alteration of bond order in the six-membered ring of the benzoxadiazole unit. The C4—C5 bond [1.349 (9) Å] has appreciable double-bond character in NBD-chloride (Suzuki et al., 1988), whereas in the present systems, this bond has considerable single-bond character, with a mean bond length of 1.40 Å. Similarly, the C5—C6 bond in NBD-chloride is 1.435 (9) Å, whereas in (I)-(III) it has an average length of 1.38 Å, indicating that the alteration of bond order of these compounds is due to substitution with a stronger donor.
The C4—N4 bond, which is very important for photophysical behaviour, is found to be considerably shorter in each of (I), (II) and (III). In similar donor-acceptor molecules with ICT states, for example 3,5-dimethyl-4-dimethylaminobenzonitrile, the corresponding C4—N4 bond length is 1.414 (3) Å, and at 173 K it is also twisted by 59.3 (2)° (Heine et al., 1994). However, this is shorter than the corresponding bond in the salt 4-aminobenzonitrile hydrochloride [1.467 (2) Å], which is considered to be a pure single bond (Colapietro et al., 1981). In the case of 4-dimethylaminobenzonitrile (DMABN), the corresponding bond is 1.367 (3) Å, with a twist angle of 10.8 (2)° (Heine et al., 1994), where considerable double-bond character has been predicted on the basis of photophysical properties. For NBD derivatives, the mean C4—N4 length is 1.34 Å. Comparing this with all the data mentioned above, we can conclude that there is a considerable charge flow from donor to acceptor, making the bond appreciably shorter. The double bond character of C4—N4 can also be explained by a formal bond valence approach.
Another noteworthy point is that the C7—N5 bond is considerably shorter in the present NBD derivatives (mean 1.42 Å) compared with NBD-chloride [1.470 (8) Å; Suzuki et al., 1988]. This indicates that the nitro group acts as the acceptor, a conclusion which is supported by the observation that the nitro group is almost coplanar with the benzoxadiazole unit. The adjacent five-membered ring of the benzoxadiazole does not contribute to electron flow, which is evident from the fact that its geometry does not change much on substitution with an amino group. Hence, the dipole moment is directed from the amino to the nitro group, removing the complexity and controversy about the involvement of the benzoxadiazole unit.
Comparing the derivatives studied, it can be seen that (I) has the shortest C4—N4 bond. This is due to the maximum overlap of the amine lone pair with the benzoxadiazole moiety, resulting from the favorable nitrogen conformation retarding rotation around the bond. This observation supports the dynamic NMR data that (I) has a higher barrier to rotation than previously reported compounds (Saha & Samanta, 1998).
The cyclic amino moiety in (II) is found to be in the stable chair conformation. The three angles around the amine N atom indicate the pyramidality at the N atom: in these derivatives, the environment of the amino N atom is almost planar. Furthermore, it can be seen from the data that (III) is more planar than the others. This is due to the lower barrier to inversion for larger rings (Oki, 1985), and also supports the photophysical observations that (III) has the maximum nonradiative rate constant value (Saha & Samanta, 1998).
There is a small increase in the twist angle between the amine and NBD moieties on going from (I) to (III). The maximum twist angle detected for (III) is 10.9 (5)° [τ(C8—N4—C4—C5)], which indicates that the excited state is unlikely to be twisted, contrary to the speculation that a twisted intramolecular charge transfer (TICT) state is involved (Forgues et al., 1993). This supports our earlier findings (Saha & Samanta, 1998).
In summary, from the structure determinations on these three NBD derivatives, we have been able to extract valuable data about the effect of amino substitutions, and some of these data supplement photophysical observations.