Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103017797/fr1435sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270103017797/fr1435Isup2.hkl |
CCDC reference: 224509
Compound (I) was prepared from (II) in a manner similar to that used for the conversion of other 9-fluorenols to fluorenes (Hou, 1997; Robinson et al., 1998; Meyers et al., 1999). A stirred solution of iodine (14.2 mg, 0.0559 mmol), 50% aqueous H3PO2 solution (1.4 ml, 13.52 mmol) and glacial acetic acid (10 ml) was heated under argon until the mixture became colorless, and 9-(meta-tert-butylphenyl)-9-fluorenol, (II) (Meyers et al., 2003) (0.251 g, 0.799 mmol), was then added. The mixture was refluxed for 3 h, cooled to room temperature, diluted with water (50 ml) and extracted with ether. The extract was washed with saturated aqueous sodium bicarbonate, dried (anhydrous MgSO4) and concentrated in vacuo, yielding a white solid (0.226 g, yield 95%, colorless crystals (from hexanes), m.p. 328.5–330 K). The melt recrystallized on cooling and remelted at the same temperature. 1H NMR (CDCl3): δ 1.31 (s, 9H), 5.05 (s, 1H), 6.71–6.74 (m, 1H), 7.12–7.40 (m, 9H), 7.787 (s, 1H), 7.813 (s, 1H); 13C NMR (CDCl3): δ 31.38, 34.66, 54.70, 119.81, 123.71, 124.87, 125.32, 125.82, 127.20, 128.32, 140.98, 141.06, 147.86, 151.46. Compound (IV) was prepared from (III) by the method described above and recrystallized from hexanes (m.p. 433.5–435.5 K; literature m.p. 436–438 K; Tolbert et al., 1992]. The crystals that reformed from the cooled melt exhibited an identical m.p. 1H NMR (CDCl3): δ 1.29 (s, 9H), 5.04 (s, 1H), 7.01–7.03 (m, 2H), 7.22–7.40 (m, 8H), 7.78–7.81 (m, 2H); 13C NMR (CDCl3): δ 31.59, 34.41, 54.18, 120.04, 125.61, 125.79, 127.44, 128.07, 138.55, 141.21, 148.22, 149.74, 154.93.
The rotational orientations of the methyl H atoms of the tert-butyl group were refined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997). All H atoms were treated as riding, with C—H distances ranging from 0.93 to 0.98 Å and Uiso(H) values equal to 1.5 (methyl H atoms) or 1.2 times (all other H atoms) Ueq of the parent atom.
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Burla et al., 1989); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: TEXSAN, SHELXL97, and PLATON.
Fig. 1. The molecular structure and atom-numbering scheme for (I), with displacement ellipsoids at the 50% probablilty level. |
C23H22 | F(000) = 640 |
Mr = 298.41 | Dx = 1.140 Mg m−3 |
Monoclinic, P21/n | Melting point = 328.5–330 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71069 Å |
a = 10.069 (3) Å | Cell parameters from 25 reflections |
b = 14.981 (3) Å | θ = 17.3–20.7° |
c = 11.714 (3) Å | µ = 0.06 mm−1 |
β = 100.17 (2)° | T = 296 K |
V = 1739.2 (8) Å3 | Irregular fragment, colorless |
Z = 4 | 0.54 × 0.43 × 0.33 mm |
Rigaku AFC-5S diffractometer | Rint = 0.013 |
Radiation source: fine-focus sealed tube | θmax = 25.1°, θmin = 2.2° |
Graphite monochromator | h = 0→11 |
ω scans | k = 0→17 |
3263 measured reflections | l = −13→13 |
3080 independent reflections | 3 standard reflections every 100 reflections |
2043 reflections with I > 2σ(I) | intensity decay: 0.7% |
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)] = 0.037 | H-atom parameters constrained |
wR(F2) = 0.109 | w = 1/[σ2(Fo2) + (0.0483P)2 + 0.2217P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
3080 reflections | Δρmax = 0.15 e Å−3 |
212 parameters | Δρmin = −0.14 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: 0.0174 (17) |
C23H22 | V = 1739.2 (8) Å3 |
Mr = 298.41 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.069 (3) Å | µ = 0.06 mm−1 |
b = 14.981 (3) Å | T = 296 K |
c = 11.714 (3) Å | 0.54 × 0.43 × 0.33 mm |
β = 100.17 (2)° |
Rigaku AFC-5S diffractometer | Rint = 0.013 |
3263 measured reflections | 3 standard reflections every 100 reflections |
3080 independent reflections | intensity decay: 0.7% |
2043 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.109 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.15 e Å−3 |
3080 reflections | Δρmin = −0.14 e Å−3 |
212 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.56269 (17) | 0.72208 (12) | 0.64909 (16) | 0.0574 (5) | |
C2 | 0.60468 (19) | 0.63648 (13) | 0.68187 (18) | 0.0684 (5) | |
C3 | 0.6701 (2) | 0.61937 (13) | 0.79321 (18) | 0.0694 (5) | |
C4 | 0.69446 (17) | 0.68630 (12) | 0.87458 (16) | 0.0596 (5) | |
C4A | 0.65216 (14) | 0.77243 (11) | 0.84260 (13) | 0.0461 (4) | |
C4B | 0.66489 (14) | 0.85634 (11) | 0.90815 (13) | 0.0451 (4) | |
C5 | 0.72398 (16) | 0.87472 (13) | 1.02220 (14) | 0.0560 (5) | |
C6 | 0.72343 (18) | 0.96137 (13) | 1.06173 (16) | 0.0628 (5) | |
C7 | 0.66601 (18) | 1.02865 (13) | 0.98982 (16) | 0.0629 (5) | |
C8 | 0.60713 (16) | 1.01129 (12) | 0.87584 (15) | 0.0546 (4) | |
C8A | 0.60763 (14) | 0.92482 (10) | 0.83551 (13) | 0.0428 (4) | |
C9 | 0.55028 (15) | 0.88810 (10) | 0.71566 (13) | 0.0451 (4) | |
C9A | 0.58670 (15) | 0.79027 (11) | 0.72969 (14) | 0.0456 (4) | |
C10 | 0.40089 (15) | 0.90825 (10) | 0.68014 (12) | 0.0424 (4) | |
C11 | 0.30464 (14) | 0.85460 (10) | 0.71907 (12) | 0.0415 (4) | |
C12 | 0.16780 (15) | 0.87381 (10) | 0.69501 (13) | 0.0438 (4) | |
C13 | 0.12901 (17) | 0.95011 (11) | 0.62963 (14) | 0.0548 (4) | |
C14 | 0.22205 (18) | 1.00394 (12) | 0.59070 (15) | 0.0609 (5) | |
C15 | 0.35826 (17) | 0.98303 (11) | 0.61511 (14) | 0.0544 (4) | |
C16 | 0.06130 (15) | 0.81638 (11) | 0.73881 (15) | 0.0517 (4) | |
C17 | 0.12213 (19) | 0.73680 (12) | 0.81064 (18) | 0.0688 (5) | |
C18 | −0.0126 (2) | 0.87343 (14) | 0.8162 (2) | 0.0805 (6) | |
C19 | −0.0402 (2) | 0.78058 (14) | 0.63534 (19) | 0.0793 (6) | |
H1 | 0.5189 | 0.7336 | 0.5738 | 0.069* | |
H2 | 0.5887 | 0.5902 | 0.6284 | 0.082* | |
H3 | 0.6982 | 0.5615 | 0.8137 | 0.083* | |
H4 | 0.7385 | 0.6741 | 0.9496 | 0.072* | |
H5 | 0.7632 | 0.8293 | 1.0710 | 0.067* | |
H6 | 0.7624 | 0.9744 | 1.1379 | 0.075* | |
H7 | 0.6666 | 1.0867 | 1.0180 | 0.075* | |
H8 | 0.5681 | 1.0570 | 0.8276 | 0.066* | |
H9 | 0.5992 | 0.9146 | 0.6588 | 0.054* | |
H11 | 0.3333 | 0.8041 | 0.7628 | 0.050* | |
H13 | 0.0380 | 0.9650 | 0.6119 | 0.066* | |
H14 | 0.1935 | 1.0547 | 0.5477 | 0.073* | |
H15 | 0.4207 | 1.0193 | 0.5877 | 0.065* | |
H17A | 0.1830 | 0.7577 | 0.8778 | 0.103* | |
H17B | 0.1704 | 0.7000 | 0.7647 | 0.103* | |
H17C | 0.0514 | 0.7025 | 0.8347 | 0.103* | |
H18A | −0.0781 | 0.8374 | 0.8454 | 0.121* | |
H18B | −0.0574 | 0.9221 | 0.7718 | 0.121* | |
H18C | 0.0512 | 0.8966 | 0.8800 | 0.121* | |
H19A | 0.0065 | 0.7453 | 0.5866 | 0.119* | |
H19B | −0.0843 | 0.8298 | 0.5916 | 0.119* | |
H19C | −0.1063 | 0.7443 | 0.6633 | 0.119* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0481 (10) | 0.0711 (12) | 0.0530 (10) | −0.0008 (9) | 0.0091 (8) | −0.0130 (9) |
C2 | 0.0642 (12) | 0.0629 (12) | 0.0795 (14) | 0.0007 (10) | 0.0165 (10) | −0.0231 (10) |
C3 | 0.0692 (13) | 0.0550 (11) | 0.0841 (14) | 0.0087 (9) | 0.0141 (11) | −0.0026 (10) |
C4 | 0.0565 (11) | 0.0601 (11) | 0.0619 (11) | 0.0062 (9) | 0.0096 (9) | 0.0034 (9) |
C4A | 0.0354 (8) | 0.0555 (10) | 0.0481 (9) | −0.0006 (7) | 0.0097 (7) | −0.0007 (7) |
C4B | 0.0331 (8) | 0.0573 (10) | 0.0453 (9) | −0.0041 (7) | 0.0081 (6) | −0.0019 (7) |
C5 | 0.0465 (9) | 0.0738 (12) | 0.0459 (9) | −0.0028 (9) | 0.0029 (7) | 0.0011 (9) |
C6 | 0.0563 (11) | 0.0794 (14) | 0.0512 (10) | −0.0136 (10) | 0.0052 (8) | −0.0158 (10) |
C7 | 0.0590 (11) | 0.0627 (12) | 0.0668 (12) | −0.0153 (9) | 0.0106 (9) | −0.0173 (10) |
C8 | 0.0475 (9) | 0.0541 (10) | 0.0618 (11) | −0.0089 (8) | 0.0084 (8) | −0.0011 (8) |
C8A | 0.0318 (8) | 0.0521 (9) | 0.0447 (8) | −0.0083 (7) | 0.0071 (6) | −0.0022 (7) |
C9 | 0.0400 (8) | 0.0549 (10) | 0.0411 (8) | −0.0058 (7) | 0.0096 (6) | 0.0031 (7) |
C9A | 0.0339 (8) | 0.0555 (10) | 0.0488 (9) | −0.0019 (7) | 0.0109 (7) | −0.0049 (7) |
C10 | 0.0422 (8) | 0.0477 (9) | 0.0357 (8) | −0.0020 (7) | 0.0021 (6) | −0.0008 (7) |
C11 | 0.0415 (8) | 0.0417 (8) | 0.0399 (8) | 0.0014 (7) | 0.0032 (6) | 0.0018 (6) |
C12 | 0.0410 (8) | 0.0450 (9) | 0.0430 (8) | 0.0015 (7) | 0.0012 (6) | −0.0049 (7) |
C13 | 0.0446 (9) | 0.0556 (10) | 0.0582 (10) | 0.0060 (8) | −0.0078 (8) | 0.0019 (8) |
C14 | 0.0648 (11) | 0.0509 (10) | 0.0595 (11) | 0.0019 (9) | −0.0091 (9) | 0.0135 (8) |
C15 | 0.0574 (10) | 0.0534 (10) | 0.0491 (9) | −0.0088 (8) | 0.0006 (8) | 0.0097 (8) |
C16 | 0.0389 (9) | 0.0510 (10) | 0.0648 (11) | −0.0022 (7) | 0.0082 (7) | −0.0031 (8) |
C17 | 0.0593 (11) | 0.0676 (12) | 0.0831 (14) | −0.0053 (9) | 0.0225 (10) | 0.0157 (10) |
C18 | 0.0642 (13) | 0.0759 (14) | 0.1106 (17) | −0.0016 (11) | 0.0405 (12) | −0.0098 (12) |
C19 | 0.0587 (12) | 0.0773 (14) | 0.0946 (15) | −0.0183 (10) | −0.0065 (11) | −0.0040 (12) |
C1—C9A | 1.383 (2) | C16—C18 | 1.532 (2) |
C1—C2 | 1.383 (3) | C16—C19 | 1.538 (2) |
C2—C3 | 1.377 (3) | C1—H1 | 0.9300 |
C3—C4 | 1.375 (2) | C2—H2 | 0.9300 |
C4—C4A | 1.389 (2) | C3—H3 | 0.9300 |
C4A—C9A | 1.396 (2) | C4—H4 | 0.9300 |
C4A—C4B | 1.467 (2) | C5—H5 | 0.9300 |
C4B—C5 | 1.391 (2) | C6—H6 | 0.9300 |
C4B—C8A | 1.391 (2) | C7—H7 | 0.9300 |
C5—C6 | 1.379 (2) | C8—H8 | 0.9300 |
C6—C7 | 1.374 (3) | C9—H9 | 0.9800 |
C7—C8 | 1.387 (2) | C15—H15 | 0.9300 |
C8—C8A | 1.379 (2) | C14—H14 | 0.9300 |
C8A—C9 | 1.523 (2) | C13—H13 | 0.9300 |
C9—C9A | 1.513 (2) | C11—H11 | 0.9300 |
C9—C10 | 1.519 (2) | C17—H17A | 0.9600 |
C10—C15 | 1.380 (2) | C17—H17B | 0.9600 |
C10—C11 | 1.396 (2) | C17—H17C | 0.9600 |
C15—C14 | 1.386 (2) | C18—H18A | 0.9600 |
C14—C13 | 1.374 (2) | C18—H18B | 0.9600 |
C13—C12 | 1.393 (2) | C18—H18C | 0.9600 |
C12—C11 | 1.387 (2) | C19—H19A | 0.9600 |
C12—C16 | 1.532 (2) | C19—H19B | 0.9600 |
C16—C17 | 1.524 (2) | C19—H19C | 0.9600 |
C9A—C1—C2 | 119.16 (17) | C1—C2—H2 | 119.8 |
C3—C2—C1 | 120.46 (18) | C4—C3—H3 | 119.4 |
C4—C3—C2 | 121.18 (18) | C2—C3—H3 | 119.4 |
C3—C4—C4A | 118.77 (17) | C3—C4—H4 | 120.6 |
C4—C4A—C9A | 120.30 (15) | C4A—C4—H4 | 120.6 |
C4—C4A—C4B | 131.33 (15) | C6—C5—H5 | 120.6 |
C9A—C4A—C4B | 108.36 (14) | C4B—C5—H5 | 120.6 |
C5—C4B—C8A | 120.16 (15) | C7—C6—H6 | 119.6 |
C5—C4B—C4A | 130.96 (15) | C5—C6—H6 | 119.6 |
C8A—C4B—C4A | 108.86 (13) | C6—C7—H7 | 119.5 |
C6—C5—C4B | 118.86 (17) | C8—C7—H7 | 119.5 |
C7—C6—C5 | 120.74 (17) | C8A—C8—H8 | 120.7 |
C6—C7—C8 | 120.98 (17) | C7—C8—H8 | 120.7 |
C8A—C8—C7 | 118.64 (17) | C9A—C9—H9 | 109.0 |
C8—C8A—C4B | 120.61 (14) | C10—C9—H9 | 109.0 |
C8—C8A—C9 | 129.13 (14) | C8A—C9—H9 | 109.0 |
C4B—C8A—C9 | 110.25 (13) | C10—C15—H15 | 120.1 |
C9A—C9—C10 | 115.58 (12) | C14—C15—H15 | 120.1 |
C9A—C9—C8A | 101.81 (12) | C13—C14—H14 | 119.8 |
C10—C9—C8A | 112.13 (12) | C15—C14—H14 | 119.8 |
C1—C9A—C4A | 120.12 (16) | C14—C13—H13 | 119.2 |
C1—C9A—C9 | 129.18 (15) | C12—C13—H13 | 119.2 |
C4A—C9A—C9 | 110.69 (13) | C12—C11—H11 | 118.8 |
C15—C10—C11 | 118.78 (14) | C10—C11—H11 | 118.8 |
C15—C10—C9 | 120.61 (14) | C16—C17—H17A | 109.5 |
C11—C10—C9 | 120.48 (13) | C16—C17—H17B | 109.5 |
C10—C15—C14 | 119.82 (15) | H17A—C17—H17B | 109.5 |
C13—C14—C15 | 120.44 (16) | C16—C17—H17C | 109.5 |
C14—C13—C12 | 121.52 (15) | H17A—C17—H17C | 109.5 |
C11—C12—C13 | 117.00 (14) | H17B—C17—H17C | 109.5 |
C11—C12—C16 | 122.98 (14) | C16—C18—H18A | 109.5 |
C13—C12—C16 | 120.00 (14) | C16—C18—H18B | 109.5 |
C12—C11—C10 | 122.42 (14) | H18A—C18—H18B | 109.5 |
C17—C16—C18 | 107.44 (16) | C16—C18—H18C | 109.5 |
C17—C16—C12 | 112.78 (13) | H18A—C18—H18C | 109.5 |
C18—C16—C12 | 109.09 (14) | H18B—C18—H18C | 109.5 |
C17—C16—C19 | 107.99 (15) | C16—C19—H19A | 109.5 |
C18—C16—C19 | 109.65 (16) | C16—C19—H19B | 109.5 |
C12—C16—C19 | 109.83 (15) | H19A—C19—H19B | 109.5 |
C9A—C1—H1 | 120.4 | C16—C19—H19C | 109.5 |
C2—C1—H1 | 120.4 | H19A—C19—H19C | 109.5 |
C3—C2—H2 | 119.8 | H19B—C19—H19C | 109.5 |
C9A—C1—C2—C3 | −0.3 (3) | C4B—C4A—C9A—C1 | 179.53 (14) |
C1—C2—C3—C4 | 0.4 (3) | C4—C4A—C9A—C9 | 179.90 (14) |
C2—C3—C4—C4A | −0.2 (3) | C4B—C4A—C9A—C9 | −1.02 (16) |
C3—C4—C4A—C9A | −0.3 (2) | C10—C9—C9A—C1 | 59.2 (2) |
C3—C4—C4A—C4B | −179.12 (16) | C8A—C9—C9A—C1 | −179.04 (15) |
C4—C4A—C4B—C5 | 0.4 (3) | C10—C9—C9A—C4A | −120.20 (14) |
C9A—C4A—C4B—C5 | −178.58 (15) | C8A—C9—C9A—C4A | 1.58 (15) |
C4—C4A—C4B—C8A | 178.88 (16) | C9A—C9—C10—C15 | −150.03 (15) |
C9A—C4A—C4B—C8A | −0.06 (16) | C8A—C9—C10—C15 | 93.89 (17) |
C8A—C4B—C5—C6 | 0.6 (2) | C9A—C9—C10—C11 | 34.1 (2) |
C4A—C4B—C5—C6 | 179.01 (16) | C8A—C9—C10—C11 | −81.92 (17) |
C4B—C5—C6—C7 | −0.2 (3) | C11—C10—C15—C14 | 0.6 (2) |
C5—C6—C7—C8 | 0.0 (3) | C9—C10—C15—C14 | −175.26 (15) |
C6—C7—C8—C8A | −0.2 (3) | C10—C15—C14—C13 | −0.8 (3) |
C7—C8—C8A—C4B | 0.6 (2) | C15—C14—C13—C12 | 0.5 (3) |
C7—C8—C8A—C9 | 179.84 (14) | C14—C13—C12—C11 | 0.0 (2) |
C5—C4B—C8A—C8 | −0.8 (2) | C14—C13—C12—C16 | 178.86 (16) |
C4A—C4B—C8A—C8 | −179.55 (14) | C13—C12—C11—C10 | −0.2 (2) |
C5—C4B—C8A—C9 | 179.81 (13) | C16—C12—C11—C10 | −178.98 (14) |
C4A—C4B—C8A—C9 | 1.11 (16) | C15—C10—C11—C12 | −0.1 (2) |
C8—C8A—C9—C9A | 179.12 (15) | C9—C10—C11—C12 | 175.74 (14) |
C4B—C8A—C9—C9A | −1.61 (15) | C11—C12—C16—C17 | −0.1 (2) |
C8—C8A—C9—C10 | −56.7 (2) | C13—C12—C16—C17 | −178.87 (15) |
C4B—C8A—C9—C10 | 122.52 (14) | C11—C12—C16—C18 | 119.20 (17) |
C2—C1—C9A—C4A | −0.2 (2) | C13—C12—C16—C18 | −59.6 (2) |
C2—C1—C9A—C9 | −179.51 (16) | C11—C12—C16—C19 | −120.60 (17) |
C4—C4A—C9A—C1 | 0.5 (2) | C13—C12—C16—C19 | 60.6 (2) |
Experimental details
Crystal data | |
Chemical formula | C23H22 |
Mr | 298.41 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 296 |
a, b, c (Å) | 10.069 (3), 14.981 (3), 11.714 (3) |
β (°) | 100.17 (2) |
V (Å3) | 1739.2 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.06 |
Crystal size (mm) | 0.54 × 0.43 × 0.33 |
Data collection | |
Diffractometer | Rigaku AFC-5S diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3263, 3080, 2043 |
Rint | 0.013 |
(sin θ/λ)max (Å−1) | 0.596 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.109, 1.04 |
No. of reflections | 3080 |
No. of parameters | 212 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.15, −0.14 |
Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996), MSC/AFC Diffractometer Control Software, PROCESS in TEXSAN (Molecular Structure Corporation, 1997), SIR92 (Burla et al., 1989), LS in TEXSAN and SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003), TEXSAN, SHELXL97, and PLATON.
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We have been studying the characteristics and variability of sp versus ap conformations of 9-(tert-butylphenyl and isopropylphenyl)fluorenes and their corresponding 9-fluorenols in solution and in the crystalline state (Hou, 1997; Meyers et al., 1997; Robinson et al., 1998; Meyers et al., 1999; Hou et al., 1999). The solution conformations were readily ascertained by 1H NMR spectroscopy. In this context, we have now examined the title compound, 9-(meta-tert-butylphenyl)fluorene, (I), prepared from 9-(meta-tert-butylphenyl)-9-fluorenol, (II). While (II), as we recently reported, is freely rotating in solution, it crystallizes out 100% as its sp conformer, exhibits O—H···π(fluorene) intermolecular hydrogen bonds in its molecular packing, and melts undecomposed, but the melt fails to recrystallize over a long period (Meyers et al., 2003).
The structure of (I) with its atom-numbering scheme is shown in Fig. 1. No hydrogen bonding is evident, the shortest H9–fluorene distance being about 3.8 Å, which precludes the most reasonable C—H···π(arene)-type bond. Solution NMR clearly shows free rotation of the 9-aryl group, and the angle between the fluorene and aryl planes of crystalline (I) [78.71 (6)°] would easily accommodate either the sp or the ap rotomeric conformation. However, both figures show that crystalline (I) is ap, in contrast to its sp 9-fluorenol progenitor (II). The surprising difference in their rotational conformations in the crystalline state may well be associated with the difference in their molecular packing. The intermolecular O—H···π(fluorene) hydrogen bonding shown in the molecular packing of (II) (Meyers et al., 2003) requires the tert-butyl group and the C9—O bond to point in the same direction, hence the O1—C9—C10—C11 torsion angle of −11.6 (4)°, i.e. the sp conformation. In contrast, the preferred molecular packing of (I) requires the corresponding tert-butyl group and the C9—H bond to point in opposite directions, hence the H9—C9—C10—C11 torsion angle of 157°, i.e. the ap conformation.
When (I) is melted it recrystallizes readily, in contrast to the failure of melted (II) to recrystallize over a long period, a behavior which may be associated with the difficulty of reforming the intermolecular hydrogen bonds required for molecular packing of crystals of (II). This explanation, rather than one involving? conformational differences, is supported by our recent observation that the melt of 9-(para-tert-butylphenyl)-9-fluorenol, (III), which is devoid of this type of conformational isomerism but which exhibits intermolecular hydrogen bonding, likewise fails to recrystallize when cooled (McLean et al., 2003). In contrast, the corresponding fluorene (IV), which has no OH group and cannot undergo hydrogen bonding, produces a melt that readily recrystallizes on cooling.