2,2'-Bi(9,9-di-n-propyl­fluorene)

The central part of the title mol­ecule, C₃₈H₄₂, is planar, all the rings being in the same plane; the lateral chains (excluding H atoms) are also planar, with each pair almost perpendicular to the ring plane. In the dimer, the two alkyl-substituted fluorene moieties are head-to-foot. The mol­ecule is on a special position of the space group, a centre of symmetry.

S1. Comment

Oligomers based on fluorene are interesting materials for optoelectronic applications, such as optical limiting, two-photon technology or light-emitting devices (Rheinhart, 1999). Nevertheless, although polyfluorene-based materials exhibit high luminescent yields, and thermal and oxidative stability, in the solid state, their optical properties are strongly influenced by the degree of organization of the material. As a rule, thin layers of regular poly(alkylfluorene) develop an additional broad band in the yellow part of their luminescent or electroluminescent spectra attributed to the formation of excimers and/or aggregates (Kläner et al., 1999). One way to suppress these troublesome phenomena is to use a well defined crystalline structure of another dimer of fluorene for which conformational motion is avoided. Recently, we have reported the crystal structure of 2,2'-bi(9,9-dihexylfluorene) (Suchod & Stéphan, 2000). As part of our programme, we present here the structure of another dimer of fluorene, (I), for which the alkyl chains grafted at the 9-position of the fluorene moiety have been shortened from 6 to 3 CH₂ units.

Surprisingly, with n-propyl chains the molecular conformation is totally different from that with hexyl ones. Whereas with the latter, alkyl chains were on the same side of the fluorene ring, with propyl chains the fluorene moieties are head-to-foot. The stacking of the molecules is also very different; the planes of conjugated dimers are parallel but shifted, while in the preceding structure there was a perpendicular arrangement of neighbouring molecules. Nevertheless, in both cases, photoluminescence measurements on crystals clearly indicate that the shift leading to yellow instead of blue light emission is avoided.

S2. Experimental

The title compound was obtained as described previously (Suchod & Stéphan, 2000) via Ni-catalyzed coupling corresponding of 2-bromofluorene monomeric units.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1998); cell refinement: CAD-4 Software; data reduction: Xtal3.2 SORTRF ADDREF (Hall et al., 1992); program(s) used to solve structure: Xtal3.2 GENTAN; program(s) used to refine structure: Xtal3.2 CRYLSQ; molecular graphics: Xtal3.2 ORTEP; software used to prepare material for publication: Xtal3.2 BONDLA CIFIO.

2,2'-bi(9,9-dipropylfluorene)

Crystal data

C38H42	F(000) = 540
Mr = 498.75	Dx = 1.106 Mg m^−3
Monoclinic, P21/c	Melting point: 458 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 8.9944 (9) Å	Cell parameters from 20 reflections
b = 16.257 (2) Å	θ = 10–12°
c = 10.519 (1) Å	µ = 0.06 mm^−1
β = 103.08 (1)°	T = 293 K
V = 1498.2 (3) Å^3	Parallelepiped, translucent pale white
Z = 2	0.3 × 0.3 × 0.2 mm

Data collection

Nonius CAD-4 diffractometer	θmax = 30.0°, θmin = 2.3°
ω scans	h = −12→12
4655 measured reflections	k = 0→22
4355 independent reflections	l = 0→14
3724 reflections with I > 2σ(I)	2 standard reflections every 100 reflections
Rint = 0.01	intensity decay: 1%

Refinement

Refinement on F	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.076	w = 1/(0.1 + 1.4σ^2)
wR(F^2) = 0.045	(Δ/σ)max = 0.027
S = 1.13	Δρmax = 0.20 e Å^−3
3724 reflections	Δρmin = −0.18 e Å^−3
257 parameters	Extinction correction: Zachariasen (1967), Eq22 p292 "Cryst. Comp." Munksgaard 1970
0 restraints	Extinction coefficient: 0.85 (3)
0 constraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.0735 (2)	−0.0561 (1)	−0.1315 (1)	0.0466 (7)
C2	0.0703 (2)	−0.02002 (9)	−0.0117 (1)	0.0411 (7)
C3	0.2046 (2)	−0.0232 (1)	0.0859 (1)	0.0521 (8)
C4	0.3362 (2)	−0.0605 (1)	0.0674 (1)	0.0527 (8)
C5	0.6076 (2)	−0.1543 (1)	−0.0416 (2)	0.0579 (9)
C6	0.6961 (2)	−0.1949 (1)	−0.1131 (2)	0.073 (1)
C7	0.6366 (2)	−0.2179 (1)	−0.2406 (2)	0.083 (1)
C8	0.4857 (2)	−0.2023 (1)	−0.2995 (2)	0.075 (1)
C9	0.2295 (2)	−0.1351 (1)	−0.2739 (1)	0.0526 (8)
C10	0.2045 (2)	−0.09281 (9)	−0.1514 (1)	0.0454 (7)
C11	0.3370 (2)	−0.09543 (9)	−0.0519 (1)	0.0437 (7)
C12	0.4560 (2)	−0.13809 (9)	−0.1009 (1)	0.0472 (8)
C13	0.3957 (2)	−0.1621 (1)	−0.2292 (1)	0.0545 (8)
C14	0.2101 (2)	−0.0747 (1)	−0.3899 (2)	0.061 (1)
C15	0.3093 (3)	0.0019 (1)	−0.3671 (2)	0.074 (1)
C16	0.2920 (4)	0.0557 (2)	−0.4871 (3)	0.105 (2)
C17	0.1205 (2)	−0.2089 (1)	−0.3117 (2)	0.060 (1)
C18	0.1319 (3)	−0.2745 (1)	−0.2084 (2)	0.078 (1)
C19	0.0099 (3)	−0.3397 (2)	−0.2403 (3)	0.081 (1)
H1	−0.014 (2)	−0.0574 (9)	−0.201 (1)	0.050 (4)*
H3	0.210 (2)	0.003 (1)	0.170 (2)	0.064 (5)*
H4	0.430 (2)	−0.061 (1)	0.138 (2)	0.063 (5)*
H5	0.650 (2)	−0.135 (1)	0.050 (2)	0.063 (5)*
H6	0.796 (2)	−0.207 (1)	−0.075 (2)	0.083 (6)*
H7	0.702 (2)	−0.248 (1)	−0.293 (2)	0.095 (6)*
H8	0.441 (2)	−0.217 (1)	−0.389 (2)	0.084 (6)*
H14a	0.229 (2)	−0.108 (1)	−0.468 (2)	0.066 (5)*
H14b	0.094 (2)	−0.057 (1)	−0.419 (1)	0.064 (5)*
H15a	0.291 (2)	0.035 (1)	−0.288 (2)	0.105 (7)*
H15b	0.420 (2)	−0.015 (1)	−0.337 (2)	0.090 (6)*
H16a	0.317 (3)	0.020 (2)	−0.559 (3)	0.14 (1)*
H16b	0.183 (3)	0.075 (2)	−0.519 (3)	0.17 (1)*
H16c	0.359 (3)	0.101 (2)	−0.474 (2)	0.113 (9)*
H17a	0.011 (2)	−0.187 (1)	−0.340 (2)	0.080 (6)*
H17b	0.140 (2)	−0.232 (1)	−0.391 (2)	0.060 (5)*
H18a	0.232 (3)	−0.299 (2)	−0.184 (3)	0.15 (1)*
H18b	0.131 (2)	−0.251 (1)	−0.120 (2)	0.113 (8)*
H19a	−0.092 (4)	−0.316 (2)	−0.250 (3)	0.17 (1)*
H19b	0.002 (3)	−0.356 (2)	−0.334 (3)	0.13 (1)*
H19c	0.027 (3)	−0.386 (2)	−0.182 (2)	0.14 (1)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0430 (8)	0.0571 (9)	0.0383 (7)	0.0067 (7)	0.0061 (6)	−0.0027 (7)
C2	0.0423 (7)	0.0425 (8)	0.0402 (7)	−0.0028 (6)	0.0130 (6)	−0.0011 (6)
C3	0.0461 (8)	0.068 (1)	0.0428 (8)	−0.0040 (8)	0.0110 (7)	−0.0156 (8)
C4	0.0406 (8)	0.072 (1)	0.0437 (8)	−0.0034 (8)	0.0054 (6)	−0.0096 (8)
C5	0.0469 (9)	0.066 (1)	0.059 (1)	0.0047 (8)	0.0090 (8)	0.0005 (9)
C6	0.046 (1)	0.088 (1)	0.084 (1)	0.020 (1)	0.0104 (9)	−0.004 (1)
C7	0.062 (1)	0.104 (2)	0.085 (1)	0.029 (1)	0.021 (1)	−0.019 (1)
C8	0.063 (1)	0.098 (2)	0.064 (1)	0.024 (1)	0.0125 (9)	−0.020 (1)
C9	0.0479 (8)	0.068 (1)	0.0411 (8)	0.0132 (8)	0.0085 (6)	−0.0076 (7)
C10	0.0474 (8)	0.0509 (9)	0.0383 (7)	0.0049 (7)	0.0103 (6)	−0.0022 (6)
C11	0.0413 (7)	0.0475 (8)	0.0426 (7)	−0.0014 (6)	0.0099 (6)	−0.0015 (6)
C12	0.0442 (8)	0.0499 (9)	0.0483 (8)	0.0041 (7)	0.0122 (6)	0.0016 (7)
C13	0.0500 (9)	0.064 (1)	0.0502 (9)	0.0126 (8)	0.0118 (7)	−0.0040 (8)
C14	0.054 (1)	0.087 (1)	0.0422 (8)	0.014 (1)	0.0108 (7)	−0.0027 (9)
C15	0.071 (1)	0.089 (2)	0.062 (1)	0.007 (1)	0.017 (1)	0.008 (1)
C16	0.097 (2)	0.123 (3)	0.095 (2)	0.001 (2)	0.023 (2)	0.039 (2)
C17	0.058 (1)	0.075 (1)	0.0453 (9)	0.0095 (9)	0.0063 (7)	−0.0165 (9)
C18	0.083 (2)	0.077 (1)	0.066 (1)	−0.009 (1)	−0.000 (1)	−0.005 (1)
C19	0.066 (1)	0.073 (1)	0.100 (2)	0.003 (1)	0.013 (1)	−0.014 (1)

Geometric parameters (Å, º)

C1—C2	1.396 (2)	C10—C11	1.398 (2)
C1—C10	1.379 (2)	C11—C12	1.464 (2)
C1—H1	0.95 (1)	C12—C13	1.392 (2)
C2—C3	1.398 (2)	C14—C15	1.518 (3)
C2—C2^i	1.492 (2)	C14—H14a	1.04 (2)
C3—C4	1.383 (2)	C14—H14b	1.06 (2)
C3—H3	0.98 (2)	C15—C16	1.515 (4)
C4—C11	1.379 (2)	C15—H15a	1.03 (2)
C4—H4	0.99 (1)	C15—H15b	1.01 (2)
C5—C6	1.381 (3)	C16—H16a	1.03 (3)
C5—C12	1.390 (2)	C16—H16b	1.01 (3)
C5—H5	1.01 (2)	C16—H16c	0.94 (2)
C6—C7	1.378 (3)	C17—C18	1.509 (3)
C6—H6	0.92 (2)	C17—H17a	1.03 (2)
C7—C8	1.382 (3)	C17—H17b	0.97 (2)
C7—H7	1.02 (2)	C18—C19	1.507 (3)
C8—C13	1.378 (3)	C18—H18a	0.97 (3)
C8—H8	0.97 (2)	C18—H18b	1.01 (2)
C9—C10	1.522 (2)	C19—H19a	0.98 (3)
C9—C13	1.527 (2)	C19—H19b	1.01 (3)
C9—C14	1.545 (2)	C19—H19c	0.96 (3)
C9—C17	1.543 (2)
C2—C1—C10	120.8 (1)	C8—C13—C9	128.6 (1)
C2—C1—H1	122 (1)	C8—C13—C12	120.4 (1)
C10—C1—H1	118 (1)	C9—C13—C12	110.9 (1)
C1—C2—C3	117.2 (1)	C9—C14—C15	116.1 (1)
C1—C2—C2^i	121.6 (1)	C9—C14—H14a	106.4 (9)
C3—C2—C2^i	121.2 (1)	C9—C14—H14b	109.2 (9)
C2—C3—C4	122.5 (1)	C15—C14—H14a	111.2 (9)
C2—C3—H3	120.3 (9)	C15—C14—H14b	108.8 (9)
C4—C3—H3	117.1 (9)	H14a—C14—H14b	105 (1)
C3—C4—C11	119.3 (1)	C14—C15—C16	113.3 (2)
C3—C4—H4	121 (1)	C14—C15—H15a	111 (1)
C11—C4—H4	120 (1)	C14—C15—H15b	109 (1)
C6—C5—C12	118.3 (2)	C16—C15—H15a	111 (1)
C6—C5—H5	122.1 (9)	C16—C15—H15b	109 (1)
C12—C5—H5	119.6 (9)	H15a—C15—H15b	102 (2)
C5—C6—C7	121.0 (2)	C15—C16—H16a	107 (2)
C5—C6—H6	119 (1)	C15—C16—H16b	112 (2)
C7—C6—H6	120 (1)	C15—C16—H16c	113 (1)
C6—C7—C8	120.8 (2)	H16a—C16—H16b	107 (2)
C6—C7—H7	121 (1)	H16a—C16—H16c	108 (2)
C8—C7—H7	119 (1)	H16b—C16—H16c	110 (2)
C7—C8—C13	118.9 (2)	C9—C17—C18	115.4 (1)
C7—C8—H8	123 (1)	C9—C17—H17a	108 (1)
C13—C8—H8	119 (1)	C9—C17—H17b	106.9 (9)
C10—C9—C13	101.0 (1)	C18—C17—H17a	111 (1)
C10—C9—C14	111.6 (1)	C18—C17—H17b	110.8 (9)
C10—C9—C17	111.3 (1)	H17a—C17—H17b	103 (1)
C13—C9—C14	110.7 (1)	C17—C18—C19	114.1 (2)
C13—C9—C17	112.1 (1)	C17—C18—H18a	113 (2)
C14—C9—C17	109.9 (1)	C17—C18—H18b	112 (1)
C1—C10—C9	128.3 (1)	C19—C18—H18a	111 (2)
C1—C10—C11	120.8 (1)	C19—C18—H18b	109 (1)
C9—C10—C11	110.9 (1)	H18a—C18—H18b	97 (2)
C4—C11—C10	119.4 (1)	C18—C19—H19a	111 (2)
C4—C11—C12	132.1 (1)	C18—C19—H19b	107 (1)
C10—C11—C12	108.5 (1)	C18—C19—H19c	114 (1)
C5—C12—C11	130.8 (1)	H19a—C19—H19b	98 (2)
C5—C12—C13	120.6 (2)	H19a—C19—H19c	113 (2)
C11—C12—C13	108.6 (1)	H19b—C19—H19c	112 (2)

Symmetry code: (i) −x, −y, −z.