Biphenyl-4,4′-diyl bis­(2,2,5,5-tetra­methyl-1-oxyl-3-pyrroline-3-carboxyl­ate)

In the title compound, C₃₀H₃₄N₂O₆, the complete molecule is generated by a crystallographic 2/m symmetry operation. The 1-oxyl-3-pyrroline-3-carboxyl­ate group lies on a mirror plane. The dihedral angle between the ring planes of the biphenyl fragment is constrained by symmetry to be zero, resulting in rather short intramolecular H...H contact distances of 2.02 Å. In the crystal, molecules are connected along the a-axis direction by very weak intermolecular methyl–phenyl C—H...π interactions. The C—H bond is not directed to the center of the benzene ring, but mainly to one C atom [C—H...C(x − 1, y, z): H...C = 2.91 Å and C—H...C = 143°].

Key indicators

• Single-crystal X-ray study
• T = 169 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.049
• wR factor = 0.126
• Data-to-parameter ratio = 19.8

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H11C   ..  C3      ..       2.91 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 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
   0 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

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S1. Comment

The title compound was prepared as a reference compound for pulsed electron-electron double resonance measurements (Weber et al., 2002).

The molecular structure is shown in Fig. 1. The molecule has 2/m symmetry: atoms C1, C4, O1, C5, O2, C6, C7, C8, C9, N1 and O3 lie on a mirror plane. There is a twofold axis perpendicular to this mirror plane and passing through the center of the central C—C single bond. There also is an inversion center at the midpoint of the central C—C single bond. The two six-membered rings of the biphenyl group are coplanar by symmetry, resulting in rather short intramolecular H···H contact distances of 2.02 A. The 1-oxyl-3-pyrroline-3-carboxylate group is planar. Approximate planarity of this group also has been observed in a number of related crystal structures (Papoutsakis et al., 1999; Boeyens & Kruger, 1970; Bolte, 2006; Duskova et al., 2001; Godt et al., 2000; Wiley et al., 1989 and Wiley et al., 1991)

The crystal packing is shown in Fig 2. The molecules are connected along the a-direction by four symmetry-equivalent very weak intermolecular C_methyl—H···π(phenyl) interactions (Table 1). The C_methyl—H bond is not directed to the center of the phenyl ring, but mainly to one C atom. There are no other short intermolecular contacts.

Related literature

For the preparation of the title compound see: Weber et al. (2002). For the crystal structures of related compounds see: Boeyens & Kruger (1970); Bolte (2006); Duskova et al. (2001); Godt et al., 2000; Papoutsakis et al. (1999); Wiley et al., 1989 and Wiley et al., 1991.

S2. Experimental

The title compound was prepared similar to the procedure described by Weber et al. (2002). Single crystals were obtained by recrystallization of the compound from a mixture of toluene and n-hexane (3:1).

S3. Refinement

The H atoms were positioned geometrically and treated as riding: C_methyl—H=0.98 Å, C_planar—H=0.95 Å, U_iso(H)=1.2U_eq(C_non-methyl) and U_iso(H)=1.5U_eq(C_methyl). The torsion angles about the C—C_methyl bonds were refined for the methyl groups.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The structure of the title compound shown with 50% probability displacement ellipsoids. The H atoms are drawn as small spheres of arbitrary radius. Symmetry equivalent atoms are related by i: x, -y, z, ii: 2 - x, -y, 1 - z and iii: 2 - x, y, 1 - z.
	Fig. 2. The crystal packing of the title compound, viewed down the a axis.

Biphenyl-4,4'-diyl bis(2,2,5,5-tetramethyl-1-oxyl-3-pyrroline-3-carboxylate)

Crystal data

C30H34N2O6	F(000) = 552
Mr = 518.59	Dx = 1.270 Mg m^−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 77 reflections
a = 6.931 (2) Å	θ = 3–23°
b = 9.461 (3) Å	µ = 0.09 mm^−1
c = 20.805 (4) Å	T = 169 K
β = 96.059 (14)°	Plate, yellow
V = 1356.6 (6) Å^3	0.44 × 0.30 × 0.10 mm
Z = 2

Data collection

Siemens SMART 1K CCD diffractometer	1552 reflections with I > 2σ(I)
Radiation source: normal-focus sealed tube	Rint = 0.056
Graphite monochromator	θmax = 30.5°, θmin = 2.0°
ω scans	h = −9→9
11267 measured reflections	k = −13→12
2074 independent reflections	l = −29→29

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.126	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.06P)^2 + 0.9P] where P = (Fo^2 + 2Fc^2)/3
2074 reflections	(Δ/σ)max = 0.001
105 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.58234 (19)	0.0000	0.29187 (6)	0.0310 (3)
O2	0.2989 (2)	0.0000	0.33551 (6)	0.0396 (4)
O3	−0.0951 (2)	0.0000	0.09831 (7)	0.0323 (3)
N1	0.0672 (2)	0.0000	0.13356 (7)	0.0231 (3)
C1	0.9329 (3)	0.0000	0.46943 (8)	0.0231 (4)
C2	0.8678 (2)	0.12604 (16)	0.43958 (6)	0.0317 (3)
H2A	0.9076	0.2135	0.4592	0.038*
C3	0.7462 (2)	0.12691 (16)	0.38187 (7)	0.0321 (3)
H3A	0.7036	0.2137	0.3622	0.039*
C4	0.6887 (3)	0.0000	0.35376 (8)	0.0261 (4)
C5	0.3862 (3)	0.0000	0.28870 (8)	0.0211 (4)
C6	0.2971 (2)	0.0000	0.22093 (8)	0.0179 (3)
C7	0.3911 (3)	0.0000	0.16826 (8)	0.0190 (3)
H7A	0.5285	0.0000	0.1696	0.023*
C8	0.2570 (3)	0.0000	0.10658 (8)	0.0205 (3)
C9	0.0794 (2)	0.0000	0.20539 (8)	0.0185 (3)
C10	0.2784 (2)	0.13302 (16)	0.06612 (7)	0.0324 (3)
H10A	0.1799	0.1325	0.0287	0.049*
H10B	0.4079	0.1348	0.0512	0.049*
H10C	0.2611	0.2169	0.0925	0.049*
C11	−0.01778 (19)	0.13337 (14)	0.22809 (7)	0.0261 (3)
H11A	−0.1535	0.1360	0.2093	0.039*
H11B	0.0503	0.2170	0.2142	0.039*
H11C	−0.0125	0.1327	0.2753	0.039*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0170 (6)	0.0590 (9)	0.0159 (6)	0.000	−0.0032 (5)	0.000
O2	0.0240 (7)	0.0753 (12)	0.0194 (6)	0.000	0.0022 (5)	0.000
O3	0.0215 (7)	0.0429 (8)	0.0295 (7)	0.000	−0.0116 (5)	0.000
N1	0.0176 (7)	0.0302 (8)	0.0200 (7)	0.000	−0.0050 (5)	0.000
C1	0.0194 (8)	0.0309 (9)	0.0182 (8)	0.000	−0.0018 (6)	0.000
C2	0.0363 (8)	0.0306 (7)	0.0256 (7)	0.0027 (6)	−0.0087 (6)	−0.0022 (5)
C3	0.0340 (8)	0.0360 (8)	0.0244 (6)	0.0067 (6)	−0.0066 (5)	0.0026 (6)
C4	0.0166 (8)	0.0452 (11)	0.0157 (8)	0.000	−0.0023 (6)	0.000
C5	0.0183 (8)	0.0246 (8)	0.0195 (8)	0.000	−0.0017 (6)	0.000
C6	0.0164 (7)	0.0172 (7)	0.0192 (8)	0.000	−0.0020 (6)	0.000
C7	0.0179 (8)	0.0188 (8)	0.0193 (8)	0.000	−0.0021 (6)	0.000
C8	0.0211 (8)	0.0226 (8)	0.0169 (7)	0.000	−0.0015 (6)	0.000
C9	0.0159 (7)	0.0193 (8)	0.0199 (8)	0.000	−0.0006 (6)	0.000
C10	0.0376 (8)	0.0321 (7)	0.0262 (7)	−0.0044 (6)	−0.0032 (6)	0.0093 (6)
C11	0.0200 (6)	0.0234 (6)	0.0346 (7)	0.0024 (5)	0.0012 (5)	−0.0035 (5)

Geometric parameters (Å, º)

O1—C5	1.354 (2)	C6—C7	1.332 (2)
O1—C4	1.414 (2)	C6—C9	1.509 (2)
O2—C5	1.199 (2)	C7—C8	1.503 (2)
O3—N1	1.2766 (19)	C7—H7A	0.9500
N1—C8	1.484 (2)	C8—C10^i	1.5299 (17)
N1—C9	1.488 (2)	C8—C10	1.5299 (17)
C1—C2^i	1.3970 (17)	C9—C11	1.5285 (16)
C1—C2	1.3971 (17)	C9—C11^i	1.5285 (16)
C1—C1^ii	1.495 (3)	C10—H10A	0.9800
C2—C3	1.3922 (19)	C10—H10B	0.9800
C2—H2A	0.9500	C10—H10C	0.9800
C3—C4	1.3760 (17)	C11—H11A	0.9800
C3—H3A	0.9500	C11—H11B	0.9800
C4—C3^i	1.3761 (17)	C11—H11C	0.9800
C5—C6	1.478 (2)
C5—O1—C4	117.92 (14)	N1—C8—C7	99.78 (13)
O3—N1—C8	123.07 (14)	N1—C8—C10^i	110.45 (10)
O3—N1—C9	122.02 (15)	C7—C8—C10^i	112.51 (9)
C8—N1—C9	114.91 (13)	N1—C8—C10	110.45 (10)
C2^i—C1—C2	117.19 (16)	C7—C8—C10	112.51 (9)
C2^i—C1—C1^ii	121.40 (8)	C10^i—C8—C10	110.69 (15)
C2—C1—C1^ii	121.40 (8)	N1—C9—C6	99.50 (13)
C3—C2—C1	121.74 (13)	N1—C9—C11	109.27 (9)
C3—C2—H2A	119.1	C6—C9—C11	113.40 (9)
C1—C2—H2A	119.1	N1—C9—C11^i	109.28 (9)
C4—C3—C2	118.90 (13)	C6—C9—C11^i	113.40 (9)
C4—C3—H3A	120.6	C11—C9—C11^i	111.28 (15)
C2—C3—H3A	120.6	C8—C10—H10A	109.5
C3—C4—C3^i	121.52 (17)	C8—C10—H10B	109.5
C3—C4—O1	119.12 (8)	H10A—C10—H10B	109.5
C3^i—C4—O1	119.12 (8)	C8—C10—H10C	109.5
O2—C5—O1	123.36 (16)	H10A—C10—H10C	109.5
O2—C5—C6	125.39 (17)	H10B—C10—H10C	109.5
O1—C5—C6	111.25 (14)	C9—C11—H11A	109.5
C7—C6—C5	126.39 (16)	C9—C11—H11B	109.5
C7—C6—C9	112.83 (14)	H11A—C11—H11B	109.5
C5—C6—C9	120.78 (14)	C9—C11—H11C	109.5
C6—C7—C8	112.99 (16)	H11A—C11—H11C	109.5
C6—C7—H7A	123.5	H11B—C11—H11C	109.5
C8—C7—H7A	123.5
C2^i—C1—C2—C3	−1.2 (3)	C9—N1—C8—C10^i	118.61 (10)
C1^ii—C1—C2—C3	178.55 (19)	O3—N1—C8—C10	61.39 (10)
C1—C2—C3—C4	0.1 (2)	C9—N1—C8—C10	−118.61 (10)
C2—C3—C4—C3^i	1.0 (3)	C6—C7—C8—N1	0.0
C2—C3—C4—O1	−173.34 (14)	C6—C7—C8—C10^i	−117.08 (11)
C5—O1—C4—C3	−92.77 (15)	C6—C7—C8—C10	117.08 (11)
C5—O1—C4—C3^i	92.77 (15)	O3—N1—C9—C6	180.0
C4—O1—C5—O2	0.0	C8—N1—C9—C6	0.0
C4—O1—C5—C6	180.0	O3—N1—C9—C11	−60.99 (10)
O2—C5—C6—C7	180.0	C8—N1—C9—C11	119.01 (10)
O1—C5—C6—C7	0.0	O3—N1—C9—C11^i	60.99 (10)
O2—C5—C6—C9	0.0	C8—N1—C9—C11^i	−119.01 (10)
O1—C5—C6—C9	180.0	C7—C6—C9—N1	0.0
C5—C6—C7—C8	180.0	C5—C6—C9—N1	180.0
C9—C6—C7—C8	0.0	C7—C6—C9—C11	−115.91 (11)
O3—N1—C8—C7	180.0	C5—C6—C9—C11	64.09 (11)
C9—N1—C8—C7	0.0	C7—C6—C9—C11^i	115.92 (11)
O3—N1—C8—C10^i	−61.39 (10)	C5—C6—C9—C11^i	−64.08 (11)

Symmetry codes: (i) x, −y, z; (ii) −x+2, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C11—H11C···C3^iii	0.98	2.91	3.745 (2)	143

Symmetry code: (iii) x−1, y, z.