organic compounds
2,2-Diphenylbenzo[c]quinoline-1-oxyl
aDipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universitá degli Studi di Parma, Viale G. P. Usberti 17/A, I-43100 Parma, Italy, bFakulteti i Shkencave të Natyrës, Departamenti i Kimise, Universiteti i Tiranes, Bulevardi "Zogu I", Tirana, Albania, and cDipartimento ISAC, Universitá Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona, Italy
*Correspondence e-mail: corrado.rizzoli@unipr.it
In the title compound, C25H18NO, a stable phenanthridinic nitroxide, the ring containing the nitroxide function assumes a twist-boat conformation and the dihedral angle formed by adjacent benzene rings is 21.78 (5)°. The phenyl substituents at position 2 are approximately orthogonal to each other, forming a dihedral angle of 81.04 (4)°. The is stabilized by an intramolecular C—H⋯O hydrogen bond and by C—H⋯π interactions.
Related literature
For applications of et al. (1996); Greci (1982); Likhtenshtein et al. (2008). For their applications in medicine, see: Damiani et al. (2008); Krishna et al. (1996). For their use in pharmacology and cosmetics, see: Krishna et al. (1996); Setjurc et al. (1995); Greci et al. (2007). For their applications in chemical processes and materials science, see: Guillaneuf et al. (2007); Arends et al. (2006); Franchi et al. (2008); Bailly et al. (2006); Bugnon et al. (2007). For a description of the Cambridge structural Database, see: Allen (2002); For puckering parameters, see: Cremer & Pople (1975). For graph-set motifs, see: Etter et al. (1990). For the synthesis, see: Colonna et al. (1980).
in biology, see: CarloniExperimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 1998); cell SAINT-Plus (Bruker, 1998); data reduction: SAINT-Plus; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL97 (Keller, 1997); software used to prepare material for publication: SHELXL97, PARST95 (Nardelli, 1995) and WinSim (Duling, 1994).
Supporting information
10.1107/S1600536809013476/fb2149sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809013476/fb2149Isup2.hkl
A dried tetrahydrofuran solution (30 ml) of 2-phenyl-3,4-benzoquinoline-N-oxide (2.72 g, 10 mmol) prepared according to the literature method (Colonna et al.,1980), was reacted at room temperature with phenylmagnesium bromide (3.62 g, 20 mmol; a commercial compound produced by Aldrich). The reaction mixture was then poured into a 10% ammonium chloride water solution (100 ml) and extracted with diethyl ether. The dried organic layer was oxidised with lead dioxide (4.8 g, 20 mmol) and, after filtration, evaporated to dryness. The residue was chromatographed on silica gel column eluting with cyclohexane/ethyl acetate (8:2 v/v; 300 mL). The expected nitroxide was isolated from the red fraction in 83% yield (2.9 g): m.p 176-7°C (175°C in Colonna et al., 1980). Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution. IR in KBr, ν, cm-1: 1926, 1771, 1732, 1667, 1589, 1732. Mass, calcd. for C25H18NO, 348.44; found: m/z = 349(M++1, 22.8), 348(60.6), 318(87.1), 272(47.4), 254(66.8), 240 (100). EPR, hfccs in Gauss: aN = 10.75; aH = 2.76; aH = 2.67; aH = 1.03; aH = 0.88; aH = 0.38; aH = 0.27; g-value = 2.00577. The melting point was measured on a Mitamura Riken Kogyo Mp. D electrochemical apparatus and was not corrected. IR spectrum were recorded in KBr with a Perkin–Elmer MGX1 spectrophotometer equipped with Spectra Tech. was recorded on a Carlo Erba QMD 1000 in positive electron impact (EI) mode. The electron-spin resonance (ESR) spectrum (Fig. 3) was simulated by using WinSim program in the NIEHS Public ESR Software Tools package (Duling, 1994).
Though all the H atoms were discernible in the difference electron density maps, the H atoms were positioned into idealized positions with C—H = 0.93 Å, and refined using a riding model approximation with Uiso(H) = 1.2 Ueq(C).
Data collection: SMART (Bruker, 1998); cell
SAINT-Plus (Bruker, 1998); data reduction: SAINT-Plus (Bruker, 1998); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL97 (Keller, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008), PARST95 (Nardelli, 1995) and WinSim (Duling, 1994).Fig. 1. The molecular structure of the title compound. The displacement ellipsoids are drawn at the 50% probability level. The intramolecular C—H···O hydrogen bond is shown as a dashed line. | |
Fig. 2. Crystal packing of the title compound viewed approximately along the b axis. Intramolecular C—H···O hydrogen bonds are shown as dashed lines. | |
Fig. 3. Experimental and simulated ESR spectrum of the title compound. |
C25H18NO | F(000) = 732 |
Mr = 348.40 | Dx = 1.278 Mg m−3 |
Monoclinic, P21/c | Melting point = 449–450 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 12.6188 (12) Å | Cell parameters from 1226 reflections |
b = 8.8704 (8) Å | θ = 3.2–24.8° |
c = 16.6083 (15) Å | µ = 0.08 mm−1 |
β = 102.998 (2)° | T = 295 K |
V = 1811.4 (3) Å3 | Block, red |
Z = 4 | 0.16 × 0.14 × 0.08 mm |
Bruker SMART 1000 CCD diffractometer | 3548 independent reflections |
Radiation source: fine-focus sealed tube | 2115 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.047 |
ω scans | θmax = 26.0°, θmin = 1.7° |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | h = −15→15 |
Tmin = 0.972, Tmax = 0.990 | k = −10→10 |
18472 measured reflections | l = −20→20 |
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)] = 0.037 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.080 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0321P)2] where P = (Fo2 + 2Fc2)/3 |
3548 reflections | (Δ/σ)max < 0.001 |
244 parameters | Δρmax = 0.11 e Å−3 |
0 restraints | Δρmin = −0.14 e Å−3 |
72 constraints |
C25H18NO | V = 1811.4 (3) Å3 |
Mr = 348.40 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 12.6188 (12) Å | µ = 0.08 mm−1 |
b = 8.8704 (8) Å | T = 295 K |
c = 16.6083 (15) Å | 0.16 × 0.14 × 0.08 mm |
β = 102.998 (2)° |
Bruker SMART 1000 CCD diffractometer | 3548 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | 2115 reflections with I > 2σ(I) |
Tmin = 0.972, Tmax = 0.990 | Rint = 0.047 |
18472 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.080 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.11 e Å−3 |
3548 reflections | Δρmin = −0.14 e Å−3 |
244 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.26974 (9) | 0.84150 (12) | 0.17884 (7) | 0.0436 (3) | |
O1 | 0.29038 (8) | 0.90766 (11) | 0.24920 (6) | 0.0590 (3) | |
C2 | 0.29264 (10) | 0.61901 (15) | 0.09755 (8) | 0.0406 (3) | |
C20 | 0.13820 (10) | 0.64080 (15) | 0.17300 (7) | 0.0386 (3) | |
C13 | 0.22201 (11) | 0.92305 (16) | 0.10729 (9) | 0.0443 (3) | |
C8 | 0.21679 (11) | 0.85600 (16) | 0.03064 (8) | 0.0458 (4) | |
C14 | 0.33392 (11) | 0.60524 (16) | 0.25222 (8) | 0.0445 (4) | |
C1 | 0.25883 (11) | 0.67236 (14) | 0.17575 (8) | 0.0391 (3) | |
C7 | 0.26972 (11) | 0.70981 (15) | 0.02684 (8) | 0.0424 (3) | |
C6 | 0.30162 (12) | 0.66030 (18) | −0.04392 (9) | 0.0526 (4) | |
H6 | 0.2896 | 0.7217 | −0.0905 | 0.063* | |
C25 | 0.07658 (13) | 0.54387 (17) | 0.11658 (9) | 0.0550 (4) | |
H25 | 0.1075 | 0.4964 | 0.0775 | 0.066* | |
C3 | 0.34171 (12) | 0.48029 (16) | 0.09411 (9) | 0.0537 (4) | |
H3 | 0.3560 | 0.4186 | 0.1406 | 0.064* | |
C21 | 0.08830 (12) | 0.71122 (17) | 0.22877 (9) | 0.0512 (4) | |
H21 | 0.1280 | 0.7785 | 0.2668 | 0.061* | |
C22 | −0.01884 (13) | 0.68398 (18) | 0.22926 (10) | 0.0595 (4) | |
H22 | −0.0506 | 0.7328 | 0.2675 | 0.071* | |
C5 | 0.35039 (12) | 0.52270 (19) | −0.04600 (9) | 0.0596 (4) | |
H5 | 0.3703 | 0.4908 | −0.0938 | 0.072* | |
C23 | −0.07899 (13) | 0.58527 (19) | 0.17372 (10) | 0.0610 (4) | |
H23 | −0.1512 | 0.5656 | 0.1744 | 0.073* | |
C12 | 0.18124 (13) | 1.06672 (18) | 0.11352 (10) | 0.0621 (4) | |
H12 | 0.1884 | 1.1122 | 0.1649 | 0.074* | |
C15 | 0.30015 (13) | 0.48928 (18) | 0.29547 (9) | 0.0603 (4) | |
H15 | 0.2285 | 0.4560 | 0.2807 | 0.072* | |
C24 | −0.03136 (13) | 0.51648 (19) | 0.11758 (10) | 0.0647 (5) | |
H24 | −0.0718 | 0.4501 | 0.0793 | 0.078* | |
C9 | 0.16276 (13) | 0.9348 (2) | −0.03924 (10) | 0.0646 (5) | |
H9 | 0.1562 | 0.8914 | −0.0911 | 0.078* | |
C19 | 0.44123 (12) | 0.65176 (19) | 0.27533 (9) | 0.0614 (4) | |
H19 | 0.4658 | 0.7291 | 0.2464 | 0.074* | |
C4 | 0.36960 (13) | 0.43243 (19) | 0.02258 (10) | 0.0622 (4) | |
H4 | 0.4016 | 0.3384 | 0.0210 | 0.075* | |
C10 | 0.11911 (15) | 1.0748 (2) | −0.03309 (13) | 0.0808 (6) | |
H10 | 0.0821 | 1.1245 | −0.0804 | 0.097* | |
C11 | 0.13017 (15) | 1.1411 (2) | 0.04279 (13) | 0.0782 (5) | |
H11 | 0.1028 | 1.2375 | 0.0465 | 0.094* | |
C18 | 0.51180 (15) | 0.5847 (2) | 0.34067 (11) | 0.0777 (6) | |
H18 | 0.5835 | 0.6178 | 0.3558 | 0.093* | |
C16 | 0.37243 (17) | 0.4214 (2) | 0.36115 (10) | 0.0838 (6) | |
H16 | 0.3491 | 0.3426 | 0.3899 | 0.101* | |
C17 | 0.47781 (18) | 0.4703 (3) | 0.38350 (11) | 0.0866 (6) | |
H17 | 0.5260 | 0.4257 | 0.4277 | 0.104* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0451 (7) | 0.0437 (7) | 0.0430 (7) | −0.0050 (5) | 0.0120 (5) | −0.0072 (6) |
O1 | 0.0672 (7) | 0.0597 (7) | 0.0499 (6) | −0.0065 (5) | 0.0130 (5) | −0.0191 (5) |
C2 | 0.0382 (8) | 0.0459 (9) | 0.0375 (8) | −0.0026 (7) | 0.0083 (6) | −0.0042 (7) |
C20 | 0.0412 (8) | 0.0409 (8) | 0.0328 (7) | −0.0012 (6) | 0.0067 (6) | 0.0045 (6) |
C13 | 0.0407 (8) | 0.0414 (9) | 0.0518 (9) | −0.0035 (7) | 0.0126 (7) | 0.0040 (7) |
C8 | 0.0435 (9) | 0.0484 (9) | 0.0465 (9) | −0.0048 (7) | 0.0121 (7) | 0.0064 (7) |
C14 | 0.0442 (9) | 0.0538 (9) | 0.0347 (7) | 0.0060 (7) | 0.0073 (6) | −0.0024 (7) |
C1 | 0.0428 (8) | 0.0391 (8) | 0.0350 (7) | −0.0008 (6) | 0.0081 (6) | −0.0008 (6) |
C7 | 0.0383 (8) | 0.0501 (9) | 0.0386 (8) | −0.0081 (7) | 0.0085 (6) | −0.0028 (7) |
C6 | 0.0482 (9) | 0.0708 (11) | 0.0396 (9) | −0.0065 (8) | 0.0115 (7) | −0.0004 (8) |
C25 | 0.0578 (10) | 0.0598 (10) | 0.0492 (9) | −0.0158 (8) | 0.0159 (8) | −0.0097 (8) |
C3 | 0.0627 (10) | 0.0526 (10) | 0.0460 (9) | 0.0061 (8) | 0.0128 (8) | −0.0018 (7) |
C21 | 0.0474 (9) | 0.0599 (10) | 0.0467 (9) | −0.0056 (7) | 0.0113 (7) | −0.0060 (7) |
C22 | 0.0504 (10) | 0.0726 (11) | 0.0592 (10) | −0.0016 (8) | 0.0205 (8) | −0.0002 (9) |
C5 | 0.0520 (10) | 0.0823 (13) | 0.0468 (9) | −0.0012 (9) | 0.0159 (8) | −0.0138 (9) |
C23 | 0.0452 (9) | 0.0765 (12) | 0.0610 (10) | −0.0096 (9) | 0.0112 (8) | 0.0115 (9) |
C12 | 0.0625 (11) | 0.0494 (10) | 0.0782 (12) | −0.0006 (8) | 0.0241 (9) | −0.0012 (9) |
C15 | 0.0582 (10) | 0.0713 (11) | 0.0513 (9) | 0.0106 (8) | 0.0119 (8) | 0.0165 (8) |
C24 | 0.0612 (11) | 0.0725 (12) | 0.0577 (10) | −0.0262 (9) | 0.0076 (9) | −0.0069 (9) |
C9 | 0.0687 (11) | 0.0689 (12) | 0.0558 (10) | 0.0025 (9) | 0.0129 (9) | 0.0158 (9) |
C19 | 0.0491 (10) | 0.0752 (12) | 0.0560 (10) | 0.0062 (8) | 0.0035 (8) | −0.0030 (9) |
C4 | 0.0652 (11) | 0.0634 (11) | 0.0591 (10) | 0.0113 (8) | 0.0164 (8) | −0.0149 (9) |
C10 | 0.0855 (14) | 0.0726 (13) | 0.0831 (14) | 0.0150 (11) | 0.0166 (11) | 0.0324 (11) |
C11 | 0.0866 (14) | 0.0491 (11) | 0.0998 (15) | 0.0135 (9) | 0.0229 (12) | 0.0181 (11) |
C18 | 0.0564 (11) | 0.0990 (15) | 0.0687 (12) | 0.0196 (11) | −0.0048 (10) | −0.0123 (12) |
C16 | 0.0889 (16) | 0.0997 (15) | 0.0638 (12) | 0.0323 (12) | 0.0192 (11) | 0.0338 (11) |
C17 | 0.0782 (15) | 0.1184 (18) | 0.0552 (11) | 0.0486 (13) | −0.0020 (11) | 0.0070 (12) |
N1—O1 | 1.2811 (13) | C22—C23 | 1.371 (2) |
N1—C13 | 1.4057 (17) | C22—H22 | 0.9300 |
N1—C1 | 1.5064 (16) | C5—C4 | 1.369 (2) |
C2—C3 | 1.3844 (18) | C5—H5 | 0.9300 |
C2—C7 | 1.3994 (18) | C23—C24 | 1.362 (2) |
C2—C1 | 1.5305 (17) | C23—H23 | 0.9300 |
C20—C25 | 1.3763 (18) | C12—C11 | 1.375 (2) |
C20—C21 | 1.3810 (18) | C12—H12 | 0.9300 |
C20—C1 | 1.5383 (18) | C15—C16 | 1.392 (2) |
C13—C12 | 1.387 (2) | C15—H15 | 0.9300 |
C13—C8 | 1.3933 (18) | C24—H24 | 0.9300 |
C8—C9 | 1.3942 (19) | C9—C10 | 1.372 (2) |
C8—C7 | 1.4665 (19) | C9—H9 | 0.9300 |
C14—C15 | 1.3760 (19) | C19—C18 | 1.375 (2) |
C14—C19 | 1.385 (2) | C19—H19 | 0.9300 |
C14—C1 | 1.5244 (17) | C4—H4 | 0.9300 |
C7—C6 | 1.3961 (19) | C10—C11 | 1.369 (2) |
C6—C5 | 1.371 (2) | C10—H10 | 0.9300 |
C6—H6 | 0.9300 | C11—H11 | 0.9300 |
C25—C24 | 1.387 (2) | C18—C17 | 1.363 (3) |
C25—H25 | 0.9300 | C18—H18 | 0.9300 |
C3—C4 | 1.3796 (19) | C16—C17 | 1.368 (3) |
C3—H3 | 0.9300 | C16—H16 | 0.9300 |
C21—C22 | 1.375 (2) | C17—H17 | 0.9300 |
C21—H21 | 0.9300 | ||
O1—N1—C13 | 119.72 (11) | C21—C22—H22 | 119.8 |
O1—N1—C1 | 119.05 (10) | C4—C5—C6 | 119.76 (14) |
C13—N1—C1 | 117.73 (11) | C4—C5—H5 | 120.1 |
C3—C2—C7 | 119.14 (13) | C6—C5—H5 | 120.1 |
C3—C2—C1 | 121.50 (12) | C24—C23—C22 | 118.95 (15) |
C7—C2—C1 | 119.32 (12) | C24—C23—H23 | 120.5 |
C25—C20—C21 | 117.79 (13) | C22—C23—H23 | 120.5 |
C25—C20—C1 | 122.53 (12) | C11—C12—C13 | 119.18 (16) |
C21—C20—C1 | 119.68 (12) | C11—C12—H12 | 120.4 |
C12—C13—C8 | 121.22 (14) | C13—C12—H12 | 120.4 |
C12—C13—N1 | 120.37 (13) | C14—C15—C16 | 120.49 (16) |
C8—C13—N1 | 118.42 (13) | C14—C15—H15 | 119.8 |
C13—C8—C9 | 117.42 (14) | C16—C15—H15 | 119.8 |
C13—C8—C7 | 119.23 (12) | C23—C24—C25 | 121.02 (15) |
C9—C8—C7 | 123.33 (14) | C23—C24—H24 | 119.5 |
C15—C14—C19 | 118.45 (14) | C25—C24—H24 | 119.5 |
C15—C14—C1 | 121.29 (13) | C10—C9—C8 | 121.41 (16) |
C19—C14—C1 | 120.02 (13) | C10—C9—H9 | 119.3 |
N1—C1—C14 | 109.01 (10) | C8—C9—H9 | 119.3 |
N1—C1—C2 | 107.22 (10) | C18—C19—C14 | 120.63 (17) |
C14—C1—C2 | 110.28 (11) | C18—C19—H19 | 119.7 |
N1—C1—C20 | 105.34 (10) | C14—C19—H19 | 119.7 |
C14—C1—C20 | 112.28 (10) | C5—C4—C3 | 120.32 (15) |
C2—C1—C20 | 112.42 (10) | C5—C4—H4 | 119.8 |
C6—C7—C2 | 118.75 (13) | C3—C4—H4 | 119.8 |
C6—C7—C8 | 122.32 (13) | C11—C10—C9 | 119.86 (17) |
C2—C7—C8 | 118.88 (12) | C11—C10—H10 | 120.1 |
C5—C6—C7 | 121.16 (14) | C9—C10—H10 | 120.1 |
C5—C6—H6 | 119.4 | C10—C11—C12 | 120.78 (17) |
C7—C6—H6 | 119.4 | C10—C11—H11 | 119.6 |
C20—C25—C24 | 120.47 (14) | C12—C11—H11 | 119.6 |
C20—C25—H25 | 119.8 | C17—C18—C19 | 120.67 (18) |
C24—C25—H25 | 119.8 | C17—C18—H18 | 119.7 |
C4—C3—C2 | 120.80 (14) | C19—C18—H18 | 119.7 |
C4—C3—H3 | 119.6 | C17—C16—C15 | 120.05 (18) |
C2—C3—H3 | 119.6 | C17—C16—H16 | 120.0 |
C22—C21—C20 | 121.45 (14) | C15—C16—H16 | 120.0 |
C22—C21—H21 | 119.3 | C18—C17—C16 | 119.70 (17) |
C20—C21—H21 | 119.3 | C18—C17—H17 | 120.2 |
C23—C22—C21 | 120.30 (15) | C16—C17—H17 | 120.2 |
C23—C22—H22 | 119.8 |
D—H···A | D—H | H···A | D···A | D—H···A |
C21—H21···O1 | 0.93 | 2.42 | 3.044 (2) | 124 |
C24—H24···Cg1i | 0.93 | 3.27 | 3.864 (3) | 136 |
C6—H6···Cg2ii | 0.93 | 3.16 | 3.932 (4) | 142 |
C10—H10···Cg3iii | 0.93 | 2.97 | 3.839 (4) | 154 |
Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+3/2, z−1/2; (iii) −x, −y+2, −z. |
Experimental details
Crystal data | |
Chemical formula | C25H18NO |
Mr | 348.40 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 295 |
a, b, c (Å) | 12.6188 (12), 8.8704 (8), 16.6083 (15) |
β (°) | 102.998 (2) |
V (Å3) | 1811.4 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.16 × 0.14 × 0.08 |
Data collection | |
Diffractometer | Bruker SMART 1000 CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 1998) |
Tmin, Tmax | 0.972, 0.990 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 18472, 3548, 2115 |
Rint | 0.047 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.080, 1.01 |
No. of reflections | 3548 |
No. of parameters | 244 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.11, −0.14 |
Computer programs: SMART (Bruker, 1998), SAINT-Plus (Bruker, 1998), SIR97 (Altomare et al., 1999), ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL97 (Keller, 1997), SHELXL97 (Sheldrick, 2008), PARST95 (Nardelli, 1995) and WinSim (Duling, 1994).
D—H···A | D—H | H···A | D···A | D—H···A |
C21—H21···O1 | 0.93 | 2.42 | 3.044 (2) | 124 |
C24—H24···Cg1i | 0.93 | 3.27 | 3.864 (3) | 136 |
C6—H6···Cg2ii | 0.93 | 3.16 | 3.932 (4) | 142 |
C10—H10···Cg3iii | 0.93 | 2.97 | 3.839 (4) | 154 |
Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+3/2, z−1/2; (iii) −x, −y+2, −z. |
Acknowledgements
Financial support from the Universitá Politecnica delle Marche and the Universitá degli Studi di Parma is gratefully acknowledged.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Most nitroxides (aminoxyls) are stable radicals that have received a great attention since the second half of the last century for the variety of their applications. In fact, in biology they have been used as relatively stable spin-adducts for studying short-lived radicals such as superoxide (Carloni et al., 1996), hydroxy and alkylperoxy radicals (Greci, 1982) that are typical for peroxidation processes. In this field, nitroxides have also been used as spin probes/spin labels for studying membranes and proteins (Likhtenshtein et al., 2008). In medicine, they have been studied as mimics of superoxide dismutase (Damiani et al., 2008), catalase (Krishna et al., 1996) and as contrast agents of NMR-imaging. In pharmacology, they have been used to study the metabolism of drugs (Setjurc et al., 1995). As antioxidants they have been used in polymers, in stabilising monomers for polyaddition during controlled radical polymerization, for the synthesis of living polymers and in large hydrocarbon distilleries for preventing polymerization and incrustation of pipes (Guillaneuf et al., 2007). As antioxidants, they have also been studied in the medical (ischemia-reperfusion) and cosmetic field for protecting against free radical damage (Greci et al., 2007). In chemistry, they have been used as inhibitors of radical processes, in radical synthesis and as mediators of controlled oxidations of primary alcohols and aldehydes (Arends et al., 2006). Recently, nitroxides have found applications in supramolecular chemistry (Franchi et al., 2008), in nanomaterials (Bailly et al., 2006) and in other technologies such as the construction of free radical batteries (Bugnon et al., 2007). In view of its potential application in cosmetics and as a precursor of alkoxyamines used in the controlled radical polymerization, the title compound has been synthesized and its crystal structure is reported here.
In the molecule of the title compound (Fig. 1), geometric parameters are usual. The value of the N1-O1 bond length (1.2811 (13) Å) corresponds well to the mean value of 1.286 (1) Å found from 891 observations yielded by the Cambridge Crystallographic Database (version 5.30; Allen, 2002) for the N—O single bond, and is in agreement with the radical character of the oxygen atom evidenced by an ESR study (Fig. 3). The benzoquinoline ring system is not planar, the dihedral angle between the C2–C7 and C8–C13 benzene rings being 21.78 (5)° as a result of the sp3 character of the C1 carbon atom. The ring containing the nitroxide function assumes a twist-boat conformation, with puckering parameters Q = 0.443 (2) Å, θ = 110.23 (18) ° and ϕ = -142.62 (18) ° (Cremer & Pople, 1975). The dihedral angle formed by the phenyl substituents at C1 is 81.04 (4)°. The molecular conformation is stabilized by an intramolecular C—H···O hydrogen bond (Tab. 1) generating an S(5) ring motif (Etter et al., 1990). In the crystal packing (Fig. 2), weak C—H···π interactions are observed ranging from 2.97 to 3.27 Å (Table 1).