The title compound, C
21H
19N
3, first synthesized by Lemke [
Chem. Ber. (1970),
103, 1894–1898], due to its solvatochromic behaviour is supposed to be a good candidate for non-linear optical (NLO) and electrooptical applications. The molecule is nearly planar, with the exception of the C(CH
3)
2 group; the disubstituted C atom is displaced by 0.627 (2) Å from the mean plane of the remaining atoms of the cyclohexene ring. The hydrogen bond formed by the indolyl NH group with the N atom of one of the cyano groups [N
N 3.168 (3) Å and N—H
N 148°], links the molecules into infinite chains stretching along the [10
] direction of the crystal. The existence of this hydrogen bond was also confirmed by FT–IR spectral data [ν
N—H = 3388 cm
−1 in the solid state (KBr pellet)].
Supporting information
CCDC reference: 170919
Key indicators
- Single-crystal X-ray study
- T = 291 K
- Mean (C-C) = 0.003 Å
- R factor = 0.052
- wR factor = 0.130
- Data-to-parameter ratio = 18.0
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
Alert Level C:
ABSMU_01 Alert C The ratio of given/expected absorption coefficient lies
outside the range 0.99 <> 1.01
Calculated value of mu = 0.072
Value of mu given = 0.070
PLAT_371 Alert C Long C(sp2)-C(sp1) Bond C(7) - C(8) = 1.43 Ang.
PLAT_371 Alert C Long C(sp2)-C(sp1) Bond C(7) - C(9) = 1.43 Ang.
PLAT_601 Alert C Structure Contains Solvent Accessible VOIDS of 37.00 A 3
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
4 Alert Level C = Please check
The title compound was synthesized according to the general procedure described
by Lemke (1970). The preparation of the starting compound,
[3,5,5-trimethyl(cyclohex-2-enylidene)]malonodinitrile, C12H14N2, is
described in one of our previous papers (Kolev et al., 2001). The
starting compound (6 mmol, 20% excess) was dissolved in 80 ml of dry toluene
under continuous stirring. Indole-3-aldehyde (5 mmol Across), dissolved in 50 ml of dry toluene, was added to the solution. Nearly 1 ml of triethylamine was
used as a catalyst. The solution became dark-red after a few minutes and the
resulting compound started precipitating. After 16 h reaction time, the
solution was cooled and the resulting title compound was isolated and
recrystallized twice from glacial acetic acid and from dry toluene [m.p.
519–521 K; literature m.p. 520–522 K (Lemke, 1970)]. The purity of the
compound was confirmed by elemental analysis, IR, UV-vis and mass
spectrometry. Crystals were grown from a glacial acetic acid solution by slow
evaporation at room temperature over a period of several weeks.
H atoms were placed in calculated positions with Uiso constrained to be
1.5Ueq of the carrier atom for the methyl H atoms and 1.2Ueq
for the remaining H atoms.
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK; data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: SHELXL97, PARST95 (Nardelli, 1995) PLATON (Spek, 2001).
Crystal data top
C21H19N3 | F(000) = 664 |
Mr = 313.39 | Dx = 1.195 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 15.5033 (3) Å | Cell parameters from 15212 reflections |
b = 7.5309 (2) Å | θ = 3.0–27.5° |
c = 15.9609 (4) Å | µ = 0.07 mm−1 |
β = 110.774 (1)° | T = 291 K |
V = 1742.34 (7) Å3 | Plate, red |
Z = 4 | 0.40 × 0.30 × 0.05 mm |
Data collection top
Nonius KappaCCD diffractometer | 1785 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.027 |
Graphite monochromator | θmax = 27.5°, θmin = 3.0° |
Detector resolution: 10 vertical, 18 horizontal pixels mm-1 | h = −20→20 |
292 frames via ω–rotation (Δω=1°) with 3 sets at
different κ–angles and two times 20 s per frame scans | k = −9→9 |
3946 measured reflections | l = −20→18 |
3946 independent reflections | |
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)] = 0.052 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.130 | H-atom parameters constrained |
S = 0.92 | w = 1/[σ2(Fo2) + (0.0595P)2] where P = (Fo2 + 2Fc2)/3 |
3946 reflections | (Δ/σ)max < 0.001 |
219 parameters | Δρmax = 0.13 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
Crystal data top
C21H19N3 | V = 1742.34 (7) Å3 |
Mr = 313.39 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 15.5033 (3) Å | µ = 0.07 mm−1 |
b = 7.5309 (2) Å | T = 291 K |
c = 15.9609 (4) Å | 0.40 × 0.30 × 0.05 mm |
β = 110.774 (1)° | |
Data collection top
Nonius KappaCCD diffractometer | 1785 reflections with I > 2σ(I) |
3946 measured reflections | Rint = 0.027 |
3946 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.052 | 0 restraints |
wR(F2) = 0.130 | H-atom parameters constrained |
S = 0.92 | Δρmax = 0.13 e Å−3 |
3946 reflections | Δρmin = −0.18 e Å−3 |
219 parameters | |
Special details top
Experimental. The data collection covered the whole sphere of reciprocal space. The
crystal-to-detector distance was 34 mm. Crystal decay was monitored by
repeating the initial frames at the end of data collection and analysing the
duplicate reflections. |
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 | |
N1 | 0.77182 (14) | 0.7498 (3) | 0.33635 (14) | 0.1010 (7) | |
N2 | 0.92484 (13) | 0.2631 (3) | 0.36515 (14) | 0.0878 (6) | |
N3 | 1.31308 (10) | 0.3652 (2) | −0.01387 (11) | 0.0607 (5) | |
H3 | 1.3479 | 0.3771 | −0.0452 | 0.073* | |
C1 | 1.03138 (11) | 0.5987 (2) | 0.14831 (11) | 0.0422 (4) | |
C2 | 0.98908 (11) | 0.5345 (2) | 0.20362 (11) | 0.0454 (5) | |
H2 | 1.0038 | 0.4203 | 0.2264 | 0.054* | |
C3 | 0.92340 (11) | 0.6330 (2) | 0.22840 (12) | 0.0446 (5) | |
C4 | 0.89425 (11) | 0.8097 (2) | 0.18518 (12) | 0.0478 (5) | |
H4A | 0.8739 | 0.8831 | 0.2245 | 0.057* | |
H4B | 0.8421 | 0.7931 | 0.1299 | 0.057* | |
C5 | 0.97066 (11) | 0.9071 (2) | 0.16431 (11) | 0.0433 (5) | |
C6 | 1.00848 (12) | 0.7823 (2) | 0.10977 (12) | 0.0476 (5) | |
H6A | 0.9632 | 0.7728 | 0.0496 | 0.057* | |
H6B | 1.0637 | 0.8349 | 0.1051 | 0.057* | |
C7 | 0.88658 (12) | 0.5679 (2) | 0.28792 (13) | 0.0513 (5) | |
C8 | 0.82267 (15) | 0.6688 (3) | 0.31439 (14) | 0.0672 (6) | |
C9 | 0.90860 (13) | 0.3979 (3) | 0.32954 (14) | 0.0608 (6) | |
C10 | 0.93022 (13) | 1.0729 (2) | 0.10920 (13) | 0.0588 (5) | |
H10A | 0.8823 | 1.0389 | 0.0544 | 0.088* | |
H10B | 0.9779 | 1.1345 | 0.0957 | 0.088* | |
H10C | 0.9051 | 1.1494 | 0.1429 | 0.088* | |
C11 | 1.04724 (12) | 0.9601 (2) | 0.25218 (13) | 0.0590 (5) | |
H11A | 1.0221 | 1.0361 | 0.2861 | 0.088* | |
H11B | 1.0950 | 1.0220 | 0.2390 | 0.088* | |
H11C | 1.0725 | 0.8554 | 0.2864 | 0.088* | |
C12 | 1.09727 (11) | 0.4906 (2) | 0.12729 (11) | 0.0467 (5) | |
H12 | 1.1090 | 0.3790 | 0.1538 | 0.056* | |
C13 | 1.14364 (11) | 0.5335 (2) | 0.07342 (11) | 0.0485 (5) | |
H13 | 1.1312 | 0.6453 | 0.0471 | 0.058* | |
C14 | 1.21002 (11) | 0.4295 (2) | 0.05107 (12) | 0.0460 (5) | |
C15 | 1.24434 (11) | 0.2509 (2) | 0.07679 (11) | 0.0444 (5) | |
C16 | 1.22783 (12) | 0.1170 (3) | 0.12974 (12) | 0.0535 (5) | |
H16 | 1.1869 | 0.1360 | 0.1596 | 0.064* | |
C17 | 1.27243 (13) | −0.0424 (3) | 0.13735 (13) | 0.0637 (6) | |
H17 | 1.2606 | −0.1318 | 0.1720 | 0.076* | |
C18 | 1.33486 (14) | −0.0740 (3) | 0.09456 (14) | 0.0692 (6) | |
H18 | 1.3640 | −0.1837 | 0.1009 | 0.083* | |
C19 | 1.35395 (13) | 0.0548 (3) | 0.04322 (14) | 0.0650 (6) | |
H19 | 1.3963 | 0.0351 | 0.0151 | 0.078* | |
C20 | 1.30800 (12) | 0.2156 (3) | 0.03455 (12) | 0.0510 (5) | |
C21 | 1.25459 (12) | 0.4895 (3) | −0.00406 (12) | 0.0569 (5) | |
H21 | 1.2457 | 0.6008 | −0.0310 | 0.068* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.1147 (17) | 0.1093 (17) | 0.1101 (17) | 0.0341 (13) | 0.0783 (15) | 0.0100 (13) |
N2 | 0.1057 (15) | 0.0763 (15) | 0.1108 (17) | 0.0105 (12) | 0.0747 (14) | 0.0251 (12) |
N3 | 0.0642 (10) | 0.0671 (12) | 0.0694 (12) | −0.0082 (9) | 0.0467 (9) | −0.0109 (10) |
C1 | 0.0467 (10) | 0.0404 (11) | 0.0433 (11) | 0.0001 (9) | 0.0208 (9) | −0.0008 (9) |
C2 | 0.0530 (11) | 0.0398 (11) | 0.0506 (13) | 0.0008 (9) | 0.0272 (10) | 0.0008 (9) |
C3 | 0.0455 (10) | 0.0441 (11) | 0.0476 (12) | −0.0033 (9) | 0.0207 (9) | −0.0032 (9) |
C4 | 0.0500 (10) | 0.0462 (11) | 0.0522 (12) | 0.0031 (9) | 0.0242 (9) | 0.0003 (9) |
C5 | 0.0483 (10) | 0.0384 (10) | 0.0467 (12) | 0.0016 (8) | 0.0211 (9) | −0.0001 (9) |
C6 | 0.0535 (11) | 0.0469 (11) | 0.0478 (12) | −0.0003 (9) | 0.0246 (9) | 0.0000 (9) |
C7 | 0.0555 (11) | 0.0500 (12) | 0.0610 (13) | 0.0014 (10) | 0.0363 (11) | 0.0006 (10) |
C8 | 0.0755 (14) | 0.0720 (15) | 0.0717 (16) | 0.0094 (12) | 0.0479 (13) | 0.0080 (12) |
C9 | 0.0675 (13) | 0.0628 (15) | 0.0723 (15) | −0.0005 (11) | 0.0495 (12) | 0.0060 (13) |
C10 | 0.0698 (12) | 0.0455 (12) | 0.0654 (14) | 0.0057 (10) | 0.0293 (11) | 0.0042 (10) |
C11 | 0.0638 (12) | 0.0567 (13) | 0.0577 (14) | −0.0048 (10) | 0.0232 (11) | −0.0073 (10) |
C12 | 0.0545 (11) | 0.0420 (11) | 0.0499 (12) | 0.0041 (9) | 0.0264 (10) | −0.0001 (9) |
C13 | 0.0584 (11) | 0.0463 (12) | 0.0486 (12) | −0.0002 (9) | 0.0285 (10) | −0.0013 (9) |
C14 | 0.0497 (10) | 0.0471 (12) | 0.0494 (12) | −0.0056 (9) | 0.0275 (9) | −0.0045 (9) |
C15 | 0.0421 (10) | 0.0498 (12) | 0.0436 (12) | −0.0041 (9) | 0.0181 (9) | −0.0072 (9) |
C16 | 0.0523 (11) | 0.0565 (13) | 0.0545 (13) | 0.0003 (10) | 0.0223 (10) | 0.0000 (10) |
C17 | 0.0651 (13) | 0.0589 (14) | 0.0625 (15) | 0.0031 (11) | 0.0172 (11) | 0.0058 (11) |
C18 | 0.0653 (14) | 0.0623 (15) | 0.0700 (16) | 0.0147 (11) | 0.0115 (12) | −0.0073 (12) |
C19 | 0.0533 (12) | 0.0767 (16) | 0.0665 (15) | 0.0080 (12) | 0.0234 (11) | −0.0165 (12) |
C20 | 0.0471 (10) | 0.0578 (13) | 0.0514 (13) | −0.0052 (10) | 0.0216 (10) | −0.0109 (10) |
C21 | 0.0688 (13) | 0.0521 (12) | 0.0621 (14) | −0.0065 (11) | 0.0384 (11) | −0.0059 (10) |
Geometric parameters (Å, º) top
N1—C8 | 1.146 (2) | C10—H10B | 0.9600 |
N2—C9 | 1.147 (2) | C10—H10C | 0.9600 |
N3—C21 | 1.350 (2) | C11—H11A | 0.9600 |
N3—C20 | 1.384 (2) | C11—H11B | 0.9600 |
N3—H3 | 0.8600 | C11—H11C | 0.9600 |
C1—C2 | 1.362 (2) | C12—C13 | 1.341 (2) |
C1—C12 | 1.436 (2) | C12—H12 | 0.9300 |
C1—C6 | 1.504 (2) | C13—C14 | 1.436 (2) |
C2—C3 | 1.425 (2) | C13—H13 | 0.9300 |
C2—H2 | 0.9300 | C14—C21 | 1.374 (2) |
C3—C7 | 1.361 (2) | C14—C15 | 1.451 (2) |
C3—C4 | 1.493 (2) | C15—C16 | 1.397 (2) |
C4—C5 | 1.527 (2) | C15—C20 | 1.404 (2) |
C4—H4A | 0.9700 | C16—C17 | 1.370 (3) |
C4—H4B | 0.9700 | C16—H16 | 0.9300 |
C5—C10 | 1.528 (2) | C17—C18 | 1.389 (3) |
C5—C6 | 1.532 (2) | C17—H17 | 0.9300 |
C5—C11 | 1.535 (2) | C18—C19 | 1.368 (3) |
C6—H6A | 0.9700 | C18—H18 | 0.9300 |
C6—H6B | 0.9700 | C19—C20 | 1.387 (3) |
C7—C8 | 1.426 (3) | C19—H19 | 0.9300 |
C7—C9 | 1.427 (3) | C21—H21 | 0.9300 |
C10—H10A | 0.9600 | | |
| | | |
C21—N3—C20 | 109.03 (15) | H10A—C10—H10C | 109.5 |
C21—N3—H3 | 125.5 | H10B—C10—H10C | 109.5 |
C20—N3—H3 | 125.5 | C5—C11—H11A | 109.5 |
C2—C1—C12 | 119.74 (16) | C5—C11—H11B | 109.5 |
C2—C1—C6 | 119.60 (15) | H11A—C11—H11B | 109.5 |
C12—C1—C6 | 120.66 (15) | C5—C11—H11C | 109.5 |
C1—C2—C3 | 123.42 (17) | H11A—C11—H11C | 109.5 |
C1—C2—H2 | 118.3 | H11B—C11—H11C | 109.5 |
C3—C2—H2 | 118.3 | C13—C12—C1 | 126.93 (17) |
C7—C3—C2 | 121.61 (17) | C13—C12—H12 | 116.5 |
C7—C3—C4 | 120.68 (15) | C1—C12—H12 | 116.5 |
C2—C3—C4 | 117.70 (15) | C12—C13—C14 | 128.49 (18) |
C3—C4—C5 | 113.43 (14) | C12—C13—H13 | 115.8 |
C3—C4—H4A | 108.9 | C14—C13—H13 | 115.8 |
C5—C4—H4A | 108.9 | C21—C14—C13 | 123.19 (18) |
C3—C4—H4B | 108.9 | C21—C14—C15 | 105.60 (15) |
C5—C4—H4B | 108.9 | C13—C14—C15 | 131.22 (16) |
H4A—C4—H4B | 107.7 | C16—C15—C20 | 117.69 (17) |
C4—C5—C10 | 109.05 (14) | C16—C15—C14 | 135.48 (16) |
C4—C5—C6 | 108.20 (14) | C20—C15—C14 | 106.83 (16) |
C10—C5—C6 | 109.61 (14) | C17—C16—C15 | 119.46 (18) |
C4—C5—C11 | 109.53 (14) | C17—C16—H16 | 120.3 |
C10—C5—C11 | 109.86 (14) | C15—C16—H16 | 120.3 |
C6—C5—C11 | 110.56 (13) | C16—C17—C18 | 121.6 (2) |
C1—C6—C5 | 114.44 (14) | C16—C17—H17 | 119.2 |
C1—C6—H6A | 108.6 | C18—C17—H17 | 119.2 |
C5—C6—H6A | 108.6 | C19—C18—C17 | 120.66 (19) |
C1—C6—H6B | 108.6 | C19—C18—H18 | 119.7 |
C5—C6—H6B | 108.6 | C17—C18—H18 | 119.7 |
H6A—C6—H6B | 107.6 | C18—C19—C20 | 117.79 (19) |
C3—C7—C8 | 121.46 (18) | C18—C19—H19 | 121.1 |
C3—C7—C9 | 123.89 (16) | C20—C19—H19 | 121.1 |
C8—C7—C9 | 114.64 (16) | N3—C20—C19 | 129.62 (18) |
N1—C8—C7 | 179.5 (2) | N3—C20—C15 | 107.62 (16) |
N2—C9—C7 | 177.5 (2) | C19—C20—C15 | 122.76 (19) |
C5—C10—H10A | 109.5 | N3—C21—C14 | 110.92 (18) |
C5—C10—H10B | 109.5 | N3—C21—H21 | 124.5 |
H10A—C10—H10B | 109.5 | C14—C21—H21 | 124.5 |
C5—C10—H10C | 109.5 | | |
| | | |
C12—C1—C2—C3 | 179.59 (15) | C12—C13—C14—C15 | 1.9 (3) |
C6—C1—C2—C3 | −0.5 (3) | C21—C14—C15—C16 | −179.28 (19) |
C1—C2—C3—C7 | −176.18 (16) | C13—C14—C15—C16 | 0.2 (3) |
C1—C2—C3—C4 | 5.2 (3) | C21—C14—C15—C20 | −0.09 (19) |
C7—C3—C4—C5 | 148.38 (16) | C13—C14—C15—C20 | 179.40 (18) |
C2—C3—C4—C5 | −33.0 (2) | C20—C15—C16—C17 | −1.0 (3) |
C3—C4—C5—C10 | 172.35 (15) | C14—C15—C16—C17 | 178.10 (19) |
C3—C4—C5—C6 | 53.19 (19) | C15—C16—C17—C18 | 0.9 (3) |
C3—C4—C5—C11 | −67.40 (19) | C16—C17—C18—C19 | 0.1 (3) |
C2—C1—C6—C5 | 23.8 (2) | C17—C18—C19—C20 | −0.9 (3) |
C12—C1—C6—C5 | −156.27 (15) | C21—N3—C20—C19 | 178.82 (19) |
C4—C5—C6—C1 | −48.67 (19) | C21—N3—C20—C15 | −0.8 (2) |
C10—C5—C6—C1 | −167.48 (14) | C18—C19—C20—N3 | −178.82 (18) |
C11—C5—C6—C1 | 71.28 (18) | C18—C19—C20—C15 | 0.7 (3) |
C2—C3—C7—C8 | 178.32 (17) | C16—C15—C20—N3 | 179.87 (15) |
C4—C3—C7—C8 | −3.1 (3) | C14—C15—C20—N3 | 0.51 (19) |
C2—C3—C7—C9 | −0.8 (3) | C16—C15—C20—C19 | 0.2 (3) |
C4—C3—C7—C9 | 177.77 (18) | C14—C15—C20—C19 | −179.11 (17) |
C2—C1—C12—C13 | 179.10 (17) | C20—N3—C21—C14 | 0.7 (2) |
C6—C1—C12—C13 | −0.8 (3) | C13—C14—C21—N3 | −179.92 (15) |
C1—C12—C13—C14 | 179.81 (16) | C15—C14—C21—N3 | −0.4 (2) |
C12—C13—C14—C21 | −178.73 (18) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3···N2i | 0.86 | 2.41 | 3.168 (3) | 148 |
C21—H21···N1ii | 0.93 | 2.55 | 3.301 (3) | 138 |
Symmetry codes: (i) x+1/2, −y+1/2, z−1/2; (ii) x+1/2, −y+3/2, z−1/2. |
Experimental details
Crystal data |
Chemical formula | C21H19N3 |
Mr | 313.39 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 291 |
a, b, c (Å) | 15.5033 (3), 7.5309 (2), 15.9609 (4) |
β (°) | 110.774 (1) |
V (Å3) | 1742.34 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.40 × 0.30 × 0.05 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3946, 3946, 1785 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.650 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.052, 0.130, 0.92 |
No. of reflections | 3946 |
No. of parameters | 219 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.13, −0.18 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3···N2i | 0.86 | 2.41 | 3.168 (3) | 148 |
C21—H21···N1ii | 0.93 | 2.55 | 3.301 (3) | 138 |
Symmetry codes: (i) x+1/2, −y+1/2, z−1/2; (ii) x+1/2, −y+3/2, z−1/2. |
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