Benzannulated Phenalenyl Radical
A R T I C L E S
MS: m/z calcd for C17H11O2 [MH+], 247.0754, found 247.0759;
Anal. Calcd (found) for C17H10O2: C, 82.91 (82.60); H, 4.09 (3.91).
Preparation of 6-Benzylamino-benzo[de]anthracen-7-one (20). A
mixture of 6-hydroxybenzanthrone (4.92 g, 0.02 mol) and benzyl-
amine (15 mL) were heated to 185 °C in a heavy-walled sealed
tube for 48 h. The mixture was allowed to cool, the tube was vented
and opened, and the contents poured into 50 mL of distilled water.
The aqueous mixture was extracted with 200 mL chloroform. The
organic layer was washed repeatedly with water and dried over
anhydrous sodium sulfate. The solvent was removed under reduced
pressure to give red oil. The crude product was purified by column
chromatography on Al2O3 with CHCl3 to give a yellow solid.
Recrystallization from a methanol and dichloromethane mixture
100, 110, 115, 125, 140, 150, 165, 175, 185, 200, 250, 270, and
293 K (low-temperature Bruker Kryoflex system, Bruker-AXS, Inc.,
UCR) For the 15K data set the crystal size was 0.10 × 0.30 ×
0.30 mm3 (Cyrocool-LHe Cryogenic System, Cryo Industries of
America, Argonne). X-ray intensity data were collected on a Bruker
APEX282 platform-CCD X-ray diffractometer system (Mo-radia-
tion, λ ) 0.71073 Å, 50 KV/40 mA power). The CCD detector
was placed at a distance of 5.000 cm (15 K data) and 5.0670 cm
(all other data) from the crystal.
A total of 2400 frames were collected for a hemisphere of
reflections, with scan width of 0.3° in ω, starting ω and 2θ angles
at -30°, and φ angles of 0, 90, 180, and 270° for every 600 frames,
30 s/frame at 293 and 150 K, 15 s/frame at 15 K, and 10 s/frame
at all other temperature. Based on a monoclinic crystal system, the
frames were integrated using the Bruker SAINT software package83
using a narrow-frame integration algorithm. Absorption corrections
were applied to all the raw intensity data using the SADABS
program.84
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gave 4 g (60%) of the desired compound. mp 190 °C; H NMR
(300 MHz, CDCl3, 25 °C): δ 12.41 (1H, s), 8.69 (1H, d, J ) 7.9
Hz), 8.56 (1H, d, J ) 7.7 Hz), 8.45 (1H, d, J ) 8.1 Hz), 7.87 (1H,
d, J ) 9.3 Hz), 7.78 (1H, d, J ) 8.0 Hz), 7.74 (1H, t, J ) 8.4 Hz),
7.61 (1H, t, J ) 7.5 Hz), 7.50-7.29 (6H, m), 7.10 (1H, d, J ) 9.3
Hz), 4.76 ppm (2H, d, J ) 5.9 Hz); 13C NMR (75 MHz, CDCl3,
25 °C): δ 155.45, 138.40, 131.49, 130.19, 128.92, 127.53, 127.22,
127.10, 126.93, 124.91, 122.57, 122.03, 114.43, 46.81; ESI-MS:
m/z calcd for C24H18NO [MH+] 336.1388; found, 336.1389; Anal.
Calcd (found) for C24H17NO: C, 85.94 (85.48); H, 5.11 (4.98); N,
4.18 (4.18).
The Bruker SHELXTL software package85 was used for phase
determination and structure refinement. The distribution of intensi-
ties and systematically absent reflections indicated the P2/c (#13)
space group for 15, 100, 110,175, 185, 200, 250, 270, 293 K data,
and P2(1)/c (#14) space group for 115, 125, 140, 150, 165 K data.
Direct methods of phase determination followed by two Fourier
cycles of refinement led to an electron density map from which
most of the non-hydrogen atoms were identified in the asymmetry
unit of the unit cell. With subsequent isotropic refinement, all of
the non-hydrogen atoms were identified. The SADI, DFIX, SIMU,
DELU, and EADP restraints were applied to stabilize the refinement
of the σ-dimer of the superstructure and π-dimer substructure. A
free variable parameter, FVAR, was used to determine the site
occupancy factor for the π-dimer/σ-dimer ratios at the various
temperatures. All data sets were refined to 0.75 Å resolutions
(maximum 2θ angle of 56.56°). Detailed descriptions of the analysis
and results are provided in the Supporting Information.
Preparation of Bis(6- benzylamino-7-oxo-benz-anthracene)boron
Tetraphenylborate (18+BPh4-). A mixture of 6-N-benzylamino-7-
oxo-benzanthracene (0.67 g, 2 mmol) and triethylamine (0.20 g, 2
mmol) in dry dichloromethane (40 mL) was treated with boron
trichloride (1 M solution in hexane) under argon. The mixture was
stirred for 72 h at room temperature. The yellow solution of the
ligand became dark red in color upon addition of boron trichloride.
Solid sodium tetraphenyl borate (1.03 g, 3 mmol) was added and
the reaction was stirred at room temperature. After 1 h the reaction
was filtered and 20 mL of dry methanol was added to the filtrate.
The mixture was allowed to stand and after three days 0.45 g (45%)
of a red crystalline salt was isolated by filtration and washed with
Magnetic Susceptibility Measurements. Magnetic susceptibility
measurements on two separate batches (see Supporting Information)
of 18 were performed over the temperature range 4-355 K on a
George Associates Faraday balance operating at 0.5 T. The system
was calibrated using Al and Pt NIST standards.
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methanol and ether. mp 222 °C; H NMR (300 MHz, CD3CN, 25
°C): δ 8.82 (1H, d, J ) 8.0 Hz), 8.51 (1H, d, J ) 7.2 Hz), 8.35
(1H, d, J ) 9.6 Hz), 8.23 (2H, d, J ) 7.4 Hz), 7.95 (1H, t, J ) 7.7
Hz), 7.45 (1H, t, J ) 7.5 Hz), 7.36 (1H, t, J ) 7.6 Hz), 7.31-7.24
(6H, m), 7.17-7.06 (4H, m), 7.00 (4H, t, J ) 7.6 Hz), 6.84 (2H,
t, J ) 7.8 Hz), 4.85 (1H, d, J ) 17.0 Hz), 4.75 (1H, d, J ) 17.1
Hz); MALDI-MS: m/z calcd for C48H32BN2O2 679.2551 [M+];
found 679; Anal. Calcd (found) for C72H52B2N2O2.CH2Cl2: C, 80.90
(81.05); H, 5.02 (4.84); N, 2.58 (2.46).
Conductivity Measurements. The single-crystal conductivity
(σ), of 18 was measured for two crystals (Figure S5-S7, Supporting
Information) in a four-probe configuration using in-line contacts
which were attached with silver paint. The needle-like crystals were
freely positioned on a sapphire substrate, and the electrical
connections between the silver paint contacts on the crystal and
the indium pads on the substrate were made by thin, flexible 25
µm diameter silver wires to relieve mechanical stress during thermal
cycling of the crystal. The temperature dependence of the conduc-
tivity was measured in the range 319-65 K using a custom-made
helium variable temperature probe with a Lake Shore 340 temper-
ature controller driven by LabVIEW software. A Keithley 236 unit
was used as a voltage source and current meter, and two 6517A
Keithley electrometers were used to measure the voltage drop
between the potential leads in a four-probe configuration.
Band Structure Calculations. The band structure calculations
made use of a modified version of the extended Huckel theory
(EHT) band structure program,86,87 as described previously.32 The
parameter set is chosen to provide a reasonably consistent picture
of bonding in heterocyclic organic compounds.10,88 The EHT
calculations used a Gaussian smoothing factor (∆ ) 0.02 eV)32 to
Crystallization of Bis(6-benzylamino-7-oxo-benz-anthracene)-
boron Radical (18). A solution of 40 mg (4.0 × 10-5 mol) of
18+BPh4 in 20 mL of dry acetonitrile was placed in a container
-
(25 mL round-bottom flask), and 25 mg (12 × 10-5 mol) of TDAE
taken in 20 mL of dry acetonitrile was placed in another container
(25 mL round-bottom flask). The containers were attached to an
invertible H-cell in the glovebox. The H-cell was removed from
the glovebox and inverted slowly. The solutions were allowed to
diffuse through the glass frit. After sitting in the dark for 15 days,
the cell yielded 19 mg (Yield 70%) of black shining crystals;
247 °C (decomposition temperature). ESI-MS: m/z calcd for
C48H32BN2O2 679.2551 [M+]; found 679.2554; Anal. Calcd (found)
for C48H32BN2O2: C, 84.83 (84.27); H, 4.75 (4.72); N, 4.12 (4.44).
Cyclic Voltammetry. Electrochemical measurements were per-
formed using a CH Instruments Electrochemical Analyzer, with
scan rates of 100 mV/s on solutions (10-3 M) of 18+BPh4 in
-
oxygen-free acetonitrile (distilled from CaH2) containing 0.1 M
tetra-n-butylammonium hexafluorophosphate. Potentials were scanned
with respect to the saturated calomel reference electrode in a single-
compartment cell fitted with Pt electrodes and referenced to the
Fc/Fc+ couple of ferrocene at 0.38 V vs SCE.
X-ray Crystallography. A black prismatic fragment (0.39 ×
0.35 × 0.26 mm3) of 18 was used for the single crystal X-ray
diffraction study of C48H32BN2O2 at the following temperatures:
(82) APEX 2, 2009.5-1; Bruker AXS Inc.: Madison, WI, 2009.
(83) SAINT, V7.60A; Bruker AXS Inc.: Madison, WI, 2009.
(84) SADABS, 2008/1; Bruker AXS Inc.: Madison, WI, 2008.
(85) SHELXTL, 2008/4; Bruker AXS Inc.: Madison, WI, 2008.
(86) Hoffmann, R. J. Chem. Phys. 1963, 39, 1397–1412.
(87) Hoffmann, R. Solids and Surfaces; VCH: New York, 1988.
(88) Haddon, R. C.; Siegrist, T.; Fleming, R. M.; Bridenbaugh, P. M.;
Laudise, R. A. J. Mater. Chem 1995, 5, 1719–1724.
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