9,9-Bis(methoxy­carbonyl­ethyl)fluorene

In the title compound, C₂₁H₂₂O₄, the three fused rings of the fluorene system are almost coplanar. There exists a weak inter­molecular C—H...O inter­action.

Key indicators

• Single-crystal X-ray study
• T = 292 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.060
• wR factor = 0.187
• Data-to-parameter ratio = 14.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C2     -   C3      ..       5.07 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C4     -   C5      ..       5.57 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C7     -   C8      ..       6.01 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C8     -   C9      ..       5.97 su
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C4
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C16
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C20
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.02
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          5

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   9 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
   8 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
   0 ALERT type 4 Improvement, methodology, query or suggestion

---

S1. Comment

Since the discovery of an electroluminescent (EL) polymer in 1990, EL conjugated polymers and oligomers offer new opportunities for information technology because of potential application in light-emitting diodes (Yang et al., 1996; Komaba et al., 1997). Polyquinolines, polyquinoxalines and polyfluorenes have recently been demonstrated as electron-transport layers light-emitting diodes due to their high thermal and oxidative stability, outstanding mechanical property, and good film-forming ability (Kreyenschmidt et al., 1998). However, polyquinolines, polyquinoxalines and polyfluorenes possess poor solution processability. Fluorene derivatives show interesting and unique chemical and physical properties because they contain a rigid planar biphenyl unit, and the facile substitution at 9-position (atom C13 in Fig. 1) can improve the solubility and processability of polymers without significantly increasing the steric interaction in the polymer backbone (Zhan et al., 2002). As a result, homopolymers and copolymers of fluorene derivatives have emerged as the most attractive blue-emitting materials due to their high effiency and excellent thermal stability (Lee & Tsuysui, 2000; Johansson et al., 2001). The synthesis of monomer (I) was carried out and the structure was determined by X-ray diffraction in order to confirm the molecular structure and to investigate its stereochemistry.

In (I), the three fused rings are essentially coplanar (Fig. 1), the dihedral angles formed by the five-membered ring with both two benzene rings being 0.6 (1)°. The two ester groups are nearly upright with respect to the fused-ring system. Selected bond lengths and angles are listed in Table 1. There is a weak intermolecular C—H···O interaction (Fig. 2 and Table 2).

S2. Experimental

A 50 ml three-necked round-bottomed flask was charged with fluorine (4 g) and methyl acrylate (5 ml) and heated to 308 K. Benzyltrimethylammonium methoxide (1 ml) was rapidly added dropwise with stirring, raising the temperature to 353 K. Excess methyl acrylate was evaporated by distillation to a kettle temperature of 343 K at a pressure of 10 m mH g, then cooled to 263 K, and the residue was removed by filteration, air dried and recrystallized from methanol to obtain the compound (I) in 83% yield. Suitable crystals for X-ray analysis were obtained by slow evaporation of methanol solution at room temperature (m.p. 355–356 K). IR (KBr, ν cm⁻¹): 3036 (Ar—H), 2948 (C—H), 1741 (C═O), 1449 (C═C), 1198, 1112 (C—O—C); ¹H NMR (CDCl₃): δ 7.71–7.31 (m, 8H), 3.46 (s, 6H), 2.43–2.39 (m, 4H), 1.58–1.53 (m, 4H). Elemental analysis calculated for C₂₁H₂₂O₄: C 74.54, H 6.55%; found: C 74.66, H 6.41%.

S3. Refinement

All H atoms were initially located in difference Fourier maps. The methyl H atoms were then constrained to an ideal geometry, with C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C), but each group was allowed to rotate freely about its C—C bond. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H = 0.93 Å for phenyl H atoms, C—H = 0.97 Å for methylene H atoms and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2001); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The asymmetric unit of (I), showing 50% probability displacement ellipsoids.
	Fig. 2. Intermolecular C—H···O interactions (dashed lines) [symmetry code: (a) 2 − x, 1/2 + y, 1/2 − z].

9,9-bis(methoxycarbonylethyl)fluorene

Crystal data

C21H22O4	F(000) = 720
Mr = 338.39	Dx = 1.204 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2480 reflections
a = 12.0711 (18) Å	θ = 2.4–21.9°
b = 10.0544 (15) Å	µ = 0.08 mm^−1
c = 15.751 (2) Å	T = 292 K
β = 102.390 (3)°	Block, colorless
V = 1867.1 (5) Å^3	0.30 × 0.24 × 0.20 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2243 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.025
Graphite monochromator	θmax = 25.0°, θmin = 2.4°
ϕ and ω scans	h = −13→14
9112 measured reflections	k = −11→11
3274 independent reflections	l = −13→18

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)] = 0.060	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.187	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0862P)^2 + 0.4752P] where P = (Fo^2 + 2Fc^2)/3
3274 reflections	(Δ/σ)max < 0.001
228 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.19 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
C1	0.7963 (2)	0.8785 (2)	0.07117 (16)	0.0704 (6)
C2	0.7584 (3)	0.8345 (3)	−0.0127 (2)	0.1052 (10)
H2	0.6814	0.8303	−0.0379	0.126*
C3	0.8423 (6)	0.7952 (4)	−0.0596 (3)	0.1378 (17)
H3	0.8214	0.7632	−0.1162	0.165*
C4	0.9564 (6)	0.8063 (4)	−0.0182 (5)	0.150 (2)
H4	1.0106	0.7810	−0.0490	0.180*
C5	0.9924 (3)	0.8506 (3)	0.0623 (3)	0.1169 (13)
H5	1.0694	0.8576	0.0870	0.140*
C6	0.9121 (2)	0.8856 (2)	0.1078 (2)	0.0783 (8)
C7	0.92643 (19)	0.9361 (2)	0.1967 (2)	0.0762 (7)
C8	1.0236 (2)	0.9615 (4)	0.2642 (3)	0.1123 (12)
H8	1.0966	0.9450	0.2564	0.135*
C9	1.0047 (4)	1.0121 (4)	0.3420 (3)	0.1276 (14)
H9	1.0669	1.0286	0.3869	0.153*
C10	0.9006 (4)	1.0380 (4)	0.3551 (2)	0.1224 (13)
H10	0.8918	1.0736	0.4077	0.147*
C11	0.8090 (3)	1.0123 (3)	0.29177 (19)	0.0886 (8)
H11	0.7369	1.0292	0.3013	0.106*
C12	0.82057 (19)	0.9610 (2)	0.21269 (16)	0.0646 (6)
C13	0.72783 (18)	0.9261 (2)	0.13542 (16)	0.0636 (6)
C14	0.65022 (18)	0.8163 (2)	0.15897 (18)	0.0720 (7)
H14A	0.6160	0.8486	0.2054	0.086*
H14B	0.5895	0.7996	0.1088	0.086*
C15	0.70962 (19)	0.6870 (2)	0.18716 (17)	0.0686 (6)
H15A	0.7337	0.6476	0.1379	0.082*
H15B	0.7771	0.7053	0.2315	0.082*
C16	0.6379 (2)	0.5886 (2)	0.22227 (17)	0.0697 (6)
C17	0.6330 (3)	0.3709 (3)	0.2766 (3)	0.1324 (15)
H17A	0.6093	0.4045	0.3269	0.199*
H17B	0.6830	0.2967	0.2930	0.199*
H17C	0.5678	0.3429	0.2341	0.199*
C18	0.65472 (19)	1.0479 (2)	0.1008 (2)	0.0792 (7)
H18A	0.5987	1.0217	0.0497	0.095*
H18B	0.6143	1.0765	0.1446	0.095*
C19	0.7222 (2)	1.1643 (2)	0.0773 (2)	0.0846 (8)
H19A	0.7747	1.1944	0.1293	0.101*
H19B	0.7665	1.1341	0.0365	0.101*
C20	0.6511 (2)	1.2780 (2)	0.03870 (17)	0.0730 (7)
C21	0.6501 (3)	1.4868 (3)	−0.0286 (2)	0.0964 (9)
H21A	0.6001	1.4627	−0.0824	0.145*
H21B	0.7029	1.5528	−0.0394	0.145*
H21C	0.6067	1.5221	0.0106	0.145*
O1	0.54479 (16)	0.6070 (2)	0.23306 (16)	0.1079 (7)
O2	0.69117 (15)	0.47347 (17)	0.24044 (16)	0.1023 (7)
O3	0.55127 (16)	1.2881 (2)	0.03373 (16)	0.1089 (8)
O4	0.71125 (15)	1.37081 (18)	0.00951 (14)	0.0894 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0886 (17)	0.0488 (12)	0.0766 (16)	−0.0009 (12)	0.0242 (13)	0.0067 (11)
C2	0.161 (3)	0.0699 (18)	0.086 (2)	−0.0091 (18)	0.031 (2)	0.0071 (16)
C3	0.269 (6)	0.070 (2)	0.093 (2)	−0.013 (3)	0.081 (4)	−0.0017 (18)
C4	0.224 (6)	0.072 (2)	0.201 (6)	0.007 (3)	0.147 (5)	0.015 (3)
C5	0.127 (3)	0.0708 (19)	0.180 (4)	0.0110 (18)	0.094 (3)	0.015 (2)
C6	0.0701 (16)	0.0506 (13)	0.125 (2)	0.0072 (11)	0.0457 (15)	0.0203 (14)
C7	0.0536 (13)	0.0610 (14)	0.112 (2)	−0.0069 (11)	0.0124 (13)	0.0182 (14)
C8	0.0620 (17)	0.093 (2)	0.172 (4)	−0.0194 (15)	0.004 (2)	0.030 (2)
C9	0.128 (3)	0.117 (3)	0.115 (3)	−0.046 (3)	−0.023 (3)	0.015 (2)
C10	0.151 (3)	0.105 (3)	0.106 (3)	−0.053 (3)	0.015 (3)	−0.007 (2)
C11	0.104 (2)	0.0714 (16)	0.0908 (19)	−0.0210 (15)	0.0206 (17)	−0.0021 (15)
C12	0.0625 (13)	0.0508 (12)	0.0795 (16)	−0.0065 (10)	0.0131 (11)	0.0042 (11)
C13	0.0513 (12)	0.0565 (13)	0.0824 (15)	0.0002 (10)	0.0132 (11)	0.0050 (11)
C14	0.0538 (12)	0.0646 (14)	0.0961 (17)	−0.0057 (11)	0.0131 (12)	0.0043 (13)
C15	0.0596 (13)	0.0618 (14)	0.0858 (16)	−0.0054 (11)	0.0186 (12)	0.0025 (12)
C16	0.0593 (14)	0.0622 (14)	0.0914 (17)	−0.0035 (11)	0.0245 (12)	−0.0010 (12)
C17	0.112 (2)	0.0732 (18)	0.234 (4)	−0.0034 (17)	0.086 (3)	0.039 (2)
C18	0.0561 (13)	0.0661 (15)	0.113 (2)	0.0038 (11)	0.0132 (13)	0.0117 (14)
C19	0.0599 (14)	0.0678 (15)	0.125 (2)	0.0060 (12)	0.0181 (14)	0.0218 (15)
C20	0.0631 (15)	0.0625 (14)	0.0928 (17)	0.0030 (12)	0.0155 (13)	0.0053 (13)
C21	0.107 (2)	0.0682 (16)	0.113 (2)	0.0065 (16)	0.0210 (18)	0.0221 (16)
O1	0.0795 (13)	0.0884 (13)	0.172 (2)	0.0072 (10)	0.0623 (13)	0.0246 (13)
O2	0.0792 (12)	0.0611 (11)	0.181 (2)	0.0003 (9)	0.0607 (13)	0.0227 (12)
O3	0.0660 (12)	0.0859 (13)	0.173 (2)	0.0126 (10)	0.0210 (12)	0.0399 (14)
O4	0.0791 (11)	0.0674 (11)	0.1247 (15)	0.0055 (9)	0.0287 (10)	0.0229 (10)

Geometric parameters (Å, º)

C1—C2	1.375 (4)	C14—C15	1.504 (3)
C1—C6	1.395 (3)	C14—H14A	0.9700
C1—C13	1.515 (3)	C14—H14B	0.9700
C2—C3	1.432 (6)	C15—C16	1.497 (3)
C2—H2	0.9300	C15—H15A	0.9700
C3—C4	1.396 (6)	C15—H15B	0.9700
C3—H3	0.9300	C16—O1	1.187 (3)
C4—C5	1.326 (6)	C16—O2	1.325 (3)
C4—H4	0.9300	C17—O2	1.432 (3)
C5—C6	1.370 (4)	C17—H17A	0.9600
C5—H5	0.9300	C17—H17B	0.9600
C6—C7	1.463 (4)	C17—H17C	0.9600
C7—C12	1.378 (3)	C18—C19	1.516 (3)
C7—C8	1.428 (4)	C18—H18A	0.9700
C8—C9	1.390 (6)	C18—H18B	0.9700
C8—H8	0.9300	C19—C20	1.480 (3)
C9—C10	1.342 (6)	C19—H19A	0.9700
C9—H9	0.9300	C19—H19B	0.9700
C10—C11	1.346 (5)	C20—O3	1.195 (3)
C10—H10	0.9300	C20—O4	1.324 (3)
C11—C12	1.382 (4)	C21—O4	1.440 (3)
C11—H11	0.9300	C21—H21A	0.9600
C12—C13	1.508 (3)	C21—H21B	0.9600
C13—C18	1.539 (3)	C21—H21C	0.9600
C13—C14	1.544 (3)
C2—C1—C6	120.7 (3)	C15—C14—H14A	108.7
C2—C1—C13	128.8 (3)	C13—C14—H14A	108.7
C6—C1—C13	110.4 (2)	C15—C14—H14B	108.7
C1—C2—C3	117.3 (4)	C13—C14—H14B	108.7
C1—C2—H2	121.3	H14A—C14—H14B	107.6
C3—C2—H2	121.3	C16—C15—C14	113.81 (19)
C4—C3—C2	118.2 (4)	C16—C15—H15A	108.8
C4—C3—H3	120.9	C14—C15—H15A	108.8
C2—C3—H3	120.9	C16—C15—H15B	108.8
C5—C4—C3	124.2 (4)	C14—C15—H15B	108.8
C5—C4—H4	117.9	H15A—C15—H15B	107.7
C3—C4—H4	117.9	O1—C16—O2	122.4 (2)
C4—C5—C6	117.6 (4)	O1—C16—C15	126.2 (2)
C4—C5—H5	121.2	O2—C16—C15	111.45 (19)
C6—C5—H5	121.2	O2—C17—H17A	109.5
C5—C6—C1	121.9 (3)	O2—C17—H17B	109.5
C5—C6—C7	129.6 (3)	H17A—C17—H17B	109.5
C1—C6—C7	108.4 (2)	O2—C17—H17C	109.5
C12—C7—C8	118.5 (3)	H17A—C17—H17C	109.5
C12—C7—C6	108.3 (2)	H17B—C17—H17C	109.5
C8—C7—C6	133.2 (3)	C19—C18—C13	113.79 (19)
C9—C8—C7	117.2 (3)	C19—C18—H18A	108.8
C9—C8—H8	121.4	C13—C18—H18A	108.8
C7—C8—H8	121.4	C19—C18—H18B	108.8
C10—C9—C8	122.9 (4)	C13—C18—H18B	108.8
C10—C9—H9	118.5	H18A—C18—H18B	107.7
C8—C9—H9	118.5	C20—C19—C18	113.7 (2)
C9—C10—C11	119.8 (4)	C20—C19—H19A	108.8
C9—C10—H10	120.1	C18—C19—H19A	108.8
C11—C10—H10	120.1	C20—C19—H19B	108.8
C10—C11—C12	120.9 (3)	C18—C19—H19B	108.8
C10—C11—H11	119.5	H19A—C19—H19B	107.7
C12—C11—H11	119.5	O3—C20—O4	122.6 (2)
C7—C12—C11	120.7 (3)	O3—C20—C19	125.5 (2)
C7—C12—C13	111.5 (2)	O4—C20—C19	112.0 (2)
C11—C12—C13	127.8 (2)	O4—C21—H21A	109.5
C12—C13—C1	101.29 (18)	O4—C21—H21B	109.5
C12—C13—C18	111.74 (19)	H21A—C21—H21B	109.5
C1—C13—C18	111.6 (2)	O4—C21—H21C	109.5
C12—C13—C14	110.88 (19)	H21A—C21—H21C	109.5
C1—C13—C14	112.41 (19)	H21B—C21—H21C	109.5
C18—C13—C14	108.82 (17)	C16—O2—C17	117.3 (2)
C15—C14—C13	114.40 (18)	C20—O4—C21	116.4 (2)
C6—C1—C2—C3	0.7 (4)	C11—C12—C13—C1	179.0 (2)
C13—C1—C2—C3	179.9 (2)	C7—C12—C13—C18	−119.7 (2)
C1—C2—C3—C4	−1.1 (5)	C11—C12—C13—C18	60.1 (3)
C2—C3—C4—C5	0.2 (6)	C7—C12—C13—C14	118.7 (2)
C3—C4—C5—C6	1.0 (6)	C11—C12—C13—C14	−61.5 (3)
C4—C5—C6—C1	−1.5 (4)	C2—C1—C13—C12	−179.1 (2)
C4—C5—C6—C7	179.6 (3)	C6—C1—C13—C12	0.2 (2)
C2—C1—C6—C5	0.6 (4)	C2—C1—C13—C18	−60.1 (3)
C13—C1—C6—C5	−178.7 (2)	C6—C1—C13—C18	119.2 (2)
C2—C1—C6—C7	179.8 (2)	C2—C1—C13—C14	62.5 (3)
C13—C1—C6—C7	0.4 (3)	C6—C1—C13—C14	−118.2 (2)
C5—C6—C7—C12	178.2 (3)	C12—C13—C14—C15	−61.3 (3)
C1—C6—C7—C12	−0.9 (3)	C1—C13—C14—C15	51.3 (3)
C5—C6—C7—C8	−2.0 (5)	C18—C13—C14—C15	175.4 (2)
C1—C6—C7—C8	178.9 (3)	C13—C14—C15—C16	171.4 (2)
C12—C7—C8—C9	−0.9 (4)	C14—C15—C16—O1	−4.0 (4)
C6—C7—C8—C9	179.3 (3)	C14—C15—C16—O2	175.6 (2)
C7—C8—C9—C10	−0.5 (6)	C12—C13—C18—C19	55.9 (3)
C8—C9—C10—C11	1.4 (6)	C1—C13—C18—C19	−56.7 (3)
C9—C10—C11—C12	−0.9 (5)	C14—C13—C18—C19	178.6 (2)
C8—C7—C12—C11	1.4 (4)	C13—C18—C19—C20	176.2 (2)
C6—C7—C12—C11	−178.7 (2)	C18—C19—C20—O3	7.8 (4)
C8—C7—C12—C13	−178.8 (2)	C18—C19—C20—O4	−172.4 (2)
C6—C7—C12—C13	1.0 (3)	O1—C16—O2—C17	−1.8 (5)
C10—C11—C12—C7	−0.6 (4)	C15—C16—O2—C17	178.6 (3)
C10—C11—C12—C13	179.7 (3)	O3—C20—O4—C21	0.4 (4)
C7—C12—C13—C1	−0.7 (2)	C19—C20—O4—C21	−179.4 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···O2^i	0.93	2.57	3.462 (3)	161

Symmetry code: (i) −x+2, y+1/2, −z+1/2.