The molecule of the title compound, C20H18N4, has twofold rotational symmetry. Each aromatic ring of the fused quinoxaline ring system is skewed from the other by 4.93 (7)°. The two quinoxaline units make a dihedral angle of 43.52 (2)°.
Supporting information
CCDC reference: 623984
Key indicators
- Single-crystal X-ray study
- T = 100 K
- Mean (C-C) = 0.002 Å
- R factor = 0.039
- wR factor = 0.111
- Data-to-parameter ratio = 9.7
checkCIF/PLATON results
No syntax errors found
Alert level C
PLAT088_ALERT_3_C Poor Data / Parameter Ratio .................... 9.66
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given ....... ?
0 ALERT level A = In general: serious problem
0 ALERT level B = Potentially serious problem
2 ALERT level C = Check and explain
0 ALERT level G = General alerts; check
0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
0 ALERT type 2 Indicator that the structure model may be wrong or deficient
1 ALERT type 3 Indicator that the structure quality may be low
1 ALERT type 4 Improvement, methodology, query or suggestion
0 ALERT type 5 Informative message, check
checkCIF publication errors
Alert level A
PUBL024_ALERT_1_A The number of authors is greater than 5.
Please specify the role of each of the co-authors
for your paper.
| Author Response: ..Each of the authors made valuable contributions to
manuscript.R. N. Salvatore suggested we investigate these unknown systems,
J. K. Kass and R. P. Gibson performed the reaction and grew the crystals.
C.H. Zambrano helped to write the manuscript while R. D. Pike
solved the x-ray structure. E. E. Dueno provided funding and completed the
manuscript.
|
1 ALERT level A = Data missing that is essential or data in wrong format
0 ALERT level G = General alerts. Data that may be required is missing
Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: XSHELL (Bruker, 2004); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
2,2',3,3'-tetramethyl-6,6'-biquinoxaline
top
Crystal data top
C20H18N4 | Z = 4 |
Mr = 314.38 | F(000) = 664 |
Monoclinic, C2/c | Dx = 1.354 Mg m−3 |
Hall symbol: -C 2yc | Melting point: 216 K |
a = 12.0225 (6) Å | Cu Kα radiation, λ = 1.54178 Å |
b = 6.7301 (3) Å | µ = 0.65 mm−1 |
c = 19.1118 (10) Å | T = 100 K |
β = 93.966 (3)° | Plate, colourless |
V = 1542.68 (13) Å3 | 0.15 × 0.15 × 0.04 mm |
Data collection top
Bruker SMART APEX-II CCD diffractometer | 1410 independent reflections |
Radiation source: fine-focus sealed tube | 1148 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.050 |
ω and φ scans | θmax = 69.0°, θmin = 4.6° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2004) | h = −14→13 |
Tmin = 0.91, Tmax = 0.98 | k = −8→7 |
8311 measured reflections | l = −21→22 |
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)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.111 | w = 1/[σ2(Fo2) + 0.9428P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
1410 reflections | Δρmax = 0.19 e Å−3 |
146 parameters | Δρmin = −0.20 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0010 (2) |
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 | |
N1 | 0.65671 (9) | 0.48492 (17) | 0.37653 (6) | 0.0182 (3) | |
N2 | 0.80829 (9) | 0.16275 (17) | 0.38491 (6) | 0.0189 (3) | |
C1 | 0.95139 (10) | 0.5046 (2) | 0.27210 (6) | 0.0172 (4) | |
C2 | 0.88078 (12) | 0.6729 (2) | 0.27409 (7) | 0.0185 (4) | |
C3 | 0.78553 (11) | 0.6684 (2) | 0.30981 (7) | 0.0184 (4) | |
C4 | 0.75697 (11) | 0.4952 (2) | 0.34589 (7) | 0.0168 (4) | |
C5 | 0.63406 (11) | 0.3183 (2) | 0.40860 (7) | 0.0182 (4) | |
C6 | 0.71252 (11) | 0.1560 (2) | 0.41439 (7) | 0.0181 (4) | |
C7 | 0.83078 (11) | 0.3318 (2) | 0.34830 (7) | 0.0174 (4) | |
C8 | 0.92771 (11) | 0.3389 (2) | 0.31092 (7) | 0.0182 (4) | |
C9 | 0.52347 (12) | 0.2985 (2) | 0.43982 (8) | 0.0218 (4) | |
C10 | 0.68672 (13) | −0.0288 (2) | 0.45370 (8) | 0.0234 (4) | |
H2 | 0.8979 (12) | 0.793 (2) | 0.2479 (8) | 0.027 (4)* | |
H3 | 0.7346 (12) | 0.782 (2) | 0.3094 (8) | 0.025 (4)* | |
H8 | 0.9755 (13) | 0.225 (2) | 0.3134 (8) | 0.027 (4)* | |
H9A | 0.4851 (13) | 0.170 (2) | 0.4235 (8) | 0.028 (4)* | |
H9B | 0.4714 (12) | 0.412 (2) | 0.4249 (7) | 0.020 (4)* | |
H9C | 0.5338 (12) | 0.292 (2) | 0.4928 (9) | 0.029 (4)* | |
H10A | 0.7546 (15) | −0.113 (2) | 0.4583 (9) | 0.037 (5)* | |
H10B | 0.6623 (12) | 0.004 (2) | 0.5013 (8) | 0.026 (4)* | |
H10C | 0.6256 (13) | −0.113 (2) | 0.4268 (8) | 0.027 (4)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0188 (6) | 0.0205 (7) | 0.0151 (6) | 0.0010 (5) | −0.0009 (5) | −0.0015 (5) |
N2 | 0.0203 (7) | 0.0193 (7) | 0.0168 (6) | 0.0012 (5) | −0.0003 (5) | 0.0003 (5) |
C1 | 0.0172 (8) | 0.0202 (7) | 0.0135 (7) | −0.0004 (6) | −0.0042 (6) | −0.0023 (5) |
C2 | 0.0207 (7) | 0.0197 (8) | 0.0144 (7) | −0.0001 (6) | −0.0028 (6) | 0.0018 (6) |
C3 | 0.0192 (8) | 0.0185 (8) | 0.0170 (8) | 0.0033 (6) | −0.0026 (6) | −0.0001 (5) |
C4 | 0.0161 (7) | 0.0210 (8) | 0.0129 (7) | −0.0002 (6) | −0.0023 (5) | −0.0023 (5) |
C5 | 0.0202 (7) | 0.0211 (8) | 0.0130 (7) | −0.0004 (6) | −0.0016 (5) | −0.0024 (5) |
C6 | 0.0203 (7) | 0.0205 (8) | 0.0132 (7) | −0.0007 (6) | −0.0016 (5) | −0.0025 (5) |
C7 | 0.0190 (7) | 0.0182 (7) | 0.0144 (7) | −0.0002 (6) | −0.0027 (6) | −0.0004 (5) |
C8 | 0.0185 (7) | 0.0188 (8) | 0.0168 (8) | 0.0020 (6) | −0.0022 (6) | −0.0007 (5) |
C9 | 0.0199 (8) | 0.0261 (8) | 0.0194 (8) | 0.0004 (7) | 0.0023 (6) | 0.0007 (6) |
C10 | 0.0262 (9) | 0.0229 (8) | 0.0212 (8) | 0.0002 (7) | 0.0031 (6) | 0.0024 (6) |
Geometric parameters (Å, º) top
N1—C5 | 1.3152 (17) | C5—C6 | 1.4427 (19) |
N1—C4 | 1.3777 (17) | C5—C9 | 1.5003 (18) |
N2—C6 | 1.3171 (17) | C6—C10 | 1.4964 (19) |
N2—C7 | 1.3721 (17) | C7—C8 | 1.4092 (18) |
C1—C8 | 1.3801 (19) | C8—H8 | 0.958 (16) |
C1—C2 | 1.4175 (19) | C9—H9A | 1.020 (16) |
C1—C1i | 1.489 (3) | C9—H9B | 1.016 (15) |
C2—C3 | 1.3735 (19) | C9—H9C | 1.012 (17) |
C2—H2 | 0.982 (16) | C10—H10A | 0.991 (18) |
C3—C4 | 1.4087 (19) | C10—H10B | 1.000 (16) |
C3—H3 | 0.979 (16) | C10—H10C | 1.035 (16) |
C4—C7 | 1.4122 (19) | | |
| | | |
C5—N1—C4 | 117.16 (12) | C5—C6—C10 | 120.71 (12) |
C6—N2—C7 | 117.11 (12) | N2—C7—C8 | 119.06 (12) |
C8—C1—C2 | 119.03 (13) | N2—C7—C4 | 121.12 (12) |
C8—C1—C1i | 120.28 (9) | C8—C7—C4 | 119.79 (13) |
C2—C1—C1i | 120.68 (9) | C1—C8—C7 | 120.56 (13) |
C3—C2—C1 | 121.14 (13) | C1—C8—H8 | 121.9 (9) |
C3—C2—H2 | 118.9 (9) | C7—C8—H8 | 117.5 (9) |
C1—C2—H2 | 119.9 (9) | C5—C9—H9A | 110.4 (9) |
C2—C3—C4 | 120.09 (13) | C5—C9—H9B | 111.6 (8) |
C2—C3—H3 | 121.5 (9) | H9A—C9—H9B | 107.2 (11) |
C4—C3—H3 | 118.4 (9) | C5—C9—H9C | 110.5 (9) |
N1—C4—C3 | 119.99 (12) | H9A—C9—H9C | 107.0 (12) |
N1—C4—C7 | 120.87 (13) | H9B—C9—H9C | 110.0 (12) |
C3—C4—C7 | 119.12 (12) | C6—C10—H10A | 108.7 (10) |
N1—C5—C6 | 121.73 (12) | C6—C10—H10B | 110.9 (9) |
N1—C5—C9 | 118.61 (12) | H10A—C10—H10B | 109.7 (13) |
C6—C5—C9 | 119.67 (12) | C6—C10—H10C | 111.7 (9) |
N2—C6—C5 | 121.83 (13) | H10A—C10—H10C | 106.6 (13) |
N2—C6—C10 | 117.46 (12) | H10B—C10—H10C | 109.2 (12) |
| | | |
C8—C1—C2—C3 | −4.64 (19) | N1—C5—C6—C10 | 177.46 (12) |
C1i—C1—C2—C3 | 174.30 (14) | C9—C5—C6—C10 | −2.49 (19) |
C1—C2—C3—C4 | 0.6 (2) | C6—N2—C7—C8 | −174.64 (11) |
C5—N1—C4—C3 | 179.05 (11) | C6—N2—C7—C4 | 3.49 (19) |
C5—N1—C4—C7 | 0.92 (18) | N1—C4—C7—N2 | −4.19 (19) |
C2—C3—C4—N1 | −174.35 (12) | C3—C4—C7—N2 | 177.67 (12) |
C2—C3—C4—C7 | 3.81 (19) | N1—C4—C7—C8 | 173.92 (12) |
C4—N1—C5—C6 | 2.70 (19) | C3—C4—C7—C8 | −4.22 (19) |
C4—N1—C5—C9 | −177.35 (11) | C2—C1—C8—C7 | 4.18 (19) |
C7—N2—C6—C5 | 0.13 (19) | C1i—C1—C8—C7 | −174.77 (13) |
C7—N2—C6—C10 | 179.29 (11) | N2—C7—C8—C1 | 178.35 (12) |
N1—C5—C6—N2 | −3.4 (2) | C4—C7—C8—C1 | 0.20 (19) |
C9—C5—C6—N2 | 176.65 (12) | | |
Symmetry code: (i) −x+2, y, −z+1/2. |