Properties of DSDPBF and DMDPBF
J. Phys. Chem. A, Vol. 106, No. 10, 2002 1963
Workstation (Austin, TX). The working electrode consisted of
a platinum disk either 1 or 3 mm in diameter inlaid in glass.
All electrodes were polished with 0.05 µm alumina (Buehler,
Ltd.) and sonicated in water and then in ethanol for 5 min each
and then dried in an oven at 110 °C for 10 min. A platinum
coil served as the counter electrode, and a silver wire contained
in a separate compartment containing a Vycor glass frit (BAS,
West Lafayette, IN) served as a quasi-reference-electrode.
Concentrations of DMDPBF and DSDPBF varied depending
on the electrochemical experiment but ranged from 1 to 3 mM.
All standard potentials are versus SCE and were determined
reduced pressure afforded and an orange-yellow solid which
was shown by 1H NMR to be a 1:1 mixture of exo:endo adducts.
The solid was dissolved in anhydrous acetonitrile (CH2Cl2; 18
mL) and anhydrous trifluoroacetic acid (1.8 mL). The mixture
was heated at reflux under argon for 20 h and then allowed to
cool to room temperature. Removal of the solvent by distillation
under reduced pressure and azeotropic distillation of the
trifluoroacetic acid with ethyl acetate (EtOAc) produced a beige
solid. Flash column chromatography over silica gel, eluting with
2% ether-hexane, afforded dimethyldiphenylbenzo[k]fluo-
ranthene (8) as a fluorescent yellow solid (1.40 g, 88%): Rf
0.45 (2% ether-benzene); mp 265-270 °C (decomposes); νmax
(film) 3056, 2916, 1593, 1494, 1372, 1025, 908, 827, 777, 733,
701 cm-1; δH (300 MHz, CDCl3) 7.72-7.52 (12H, m), 7.38
(2H, s), 7.30 (2H, t, J 7.5 Hz), 6.56 (2H, d, J 7.5 Hz), 2.33 (6H,
s); δC (125 MHz, CDCl3) 139.2, 136.9, 135.6, 135.5, 134.2,
134.1, 131.6, 130.1, 130.0, 129.2, 127.8, 127.7, 126.5, 125.6,
121.8, 20.2; m/z (CI) 433 [M + H]+, 391, 307 (found: [M +
H]+, 433.1953. C34H24 requires [M + H]+, 433.1956).
Synthesis of DSDPBF (11). The second half of the synthesis
is provided in Scheme 2. To a suspension of compound (8; 87
mg, 0.201 mmol) and N-bromosuccinimide (73 mg, 0.412
mmol) in carbon tetrachloride (1.0 mL) was added benzoyl
peroxide (3 mg, 0.012 mmol). The orange mixture was heated
to reflux giving a dark orange colored solution containing some
solid. After a total of 4 h at reflux, the reaction mixture was
allowed to cool to room temperature, and the solid succinimide
was filtered off, washing through with carbon tetrachloride (15
mL). The solvent was removed under reduced pressure giving
an orange foam. Purification by flash column chromatography
over silica gel (hexane-dichloromethane 25:1) afforded the
dibromide 9 as a yellow solid (85 mg, 72%): 1H NMR (300
MHz, CDCl3) δ 7.80-7.67 (m, 8H), 7.64 (s, 2H), 7.60-7.50
(m, 4H), 7.34 (m, 2H), 6.61 (d, J ) 7.2 Hz, 2H), 4.80 (s, 4H);
13C NMR (75 MHz, CDCl3) δ 138.0, 136.0, 135.4, 134.6, 133.5,
132.8, 129.9, 129.5, 129.3, 129.2, 128.2, 128.0, 127.8, 126.3,
122.6, 31.4; IR (film) 3054, 2920, 2850, 1595, 1488, 1440 cm-1;
LRCIMS m/z 591 (M + H+, 36), 511 (100), 431 (26); HRCIMS
m/z calcd for C34H22Br2, M + H+, 589.0166; found, 589.0126.
To sodium sulfide (262 mg, 1.092 mmol), dibromide (9; 358
mg, 0.606 mmol), and 4 Å molecular sieves under argon was
added dry THF (7.0 mL). The mixture was stirred at ambient
temperature for a further 24 h. The mixture was diluted with
dichloromethane and filtered through Celite and then washed
through with more dichloromethane. The solvent was removed
under reduced pressure to afford a yellow solid. Purification
by column chromatography over silica gel (hexane-dichloro-
methane 2:1) afforded the sulfide 10 as an orange-brown sticky
solid (263 mg, 94%): 1H NMR (300 MHz, CDCl3) δ 7.75-
7-65 (m, 8H), 7.56 (m, 4H), 7.49 (s, 2H), 7.32 (m, 2H), 6.57
(d, J ) 7.1 Hz, 2H), 4.27 (s, 4H); 13C NMR (75 MHz, CDCl3)
δ 37.3, 121.7, 122.1, 125.8, 126.1, 127.7, 127.8, 127.9, 128.1,
129.2, 129.3, 129.4, 129.4, 129.5, 129.7, 129.7, 129.8, 129.9,
130.0, 130.0, 138.8; IR (film) 3055, 2923, 2852, 1765, 1692,
1606, 1494, 1440, 1373, 1264 cm-1; LRCIMS m/z 463 (M +
H+, 100); HRCIMS m/z calcd for C34H22S, M + H+, 463.1520;
found, 463.1501.
by adding ferrocene (taking Eo
) 0.424 V vs SCE in
Fc/Fc+
benzene) as an internal potential marker.3
Bulk electrolysis to produce the dimer was performed using
a large area platinum mesh working electrode and a large area
platinum mesh counter electrode that was placed in a compart-
ment that was separated from the working electrode by a fine
glass frit. The reference electrode consisted of a silver wire
placed in the same compartment as the working electrode but
separated by glass frit made of Vycor. The working electrode
was biased 1.6V vs Ag wire for 1 h using a Princeton Applied
Research (PAR, Princeton, NJ) model 175 universal program-
mer, model 173 potentiostat-galvostat, and model 179 digital
coulometer.
Calculations. Semiempirical AM1 calculations were per-
formed using HyperChem (HyperCube, Inc., Gainesville, FL).
The following molecular parameters were used: total charge
was set to zero, the spin multiplicity was one, the iteration limit
was 50, the convergent limit was 0.01, the spin pairing was set
to RHF, and the lowest state was determined. The optimized
geometry in vacuo was determined by using the Fletcher-
Reeves algorithm with termination conditions consisting of a
RMS gradient of 0.05 Kcal/A mol or a total of 1680 cycles.
Electrogenerated Chemiluminescence. ECL measurements
were obtained using the same procedure as previously reported.5
These measurements were made with solutions prepared in the
same manner as those used to obtain the cyclic voltammograms.
The working electrode in all cases was a platinum disk
approximately 3 mm in diameter inlaid in glass. The concentra-
tion for the monomers of DMDPBF and DSDPBF were
approximately 2 ( 0.2 mM, whereas the concentration for the
dimer of DMDPBF was 0.5 ( 0.1 mM as the result of low
solubility in the solvent mixture. The cell was pulsed between
the oxidation and reduction peak potentials of each compound
using a Princeton Applied Research (PAR, Princeton, NJ) model
175 universal programmer, model 173 potentiostat-galvostat,
and model 179 digital coulometer. The pulse width for all
experiments was 0.1 s. All spectra were recorded using a charge
couple device (CCD) camera (Photometrics CH260, Photo-
metrics, Tucson, AZ) cooled to -100 °C and a Chemspec 100S
(American Holographic, Littleton, MA) spectrometer. The
relative ECL efficiencies were determined using Ru(bpy)3-
(ClO4)2 as the standard (φECL ) 0.05). The apparatus and
methodologies for determining the ECL efficiency have been
previously published.5
Synthesis of DMDPBF (8). The overall reaction mechanism
that was used to synthesize this compound is shown in Scheme
1. The first five steps are similar to the previously reported
synthesis of DPBF.3 A solution of isobenzofuran (6; 1.10 g,
3.68 mmol, 1.0 equiv) and freshly sublimed acenaphthylene (7;
0.671 g, 4.41 mmol, 1.2 equiv) in xylenes (18 mL) was heated
to reflux under argon. After 17 h, the solution was allowed to
cool to room temperature; some precipitate appeared in the
solution at this time. Removal of the solvent by distillation under
To a stirred solution of the sulfide 10 (69 mg, 0.149 mmol)
in dry dichloromethane (1.5 mL) at 0 °C under argon was added,
dropwise, peracetic acid (0.125 mL, 0.60 mmol, 32 wt % in
acetic acid). When the addition was complete, the reaction was
warmed to room temperature and stirred for a further 30 h. The
reaction was quenched with saturated aqueous sodium hydrogen
carbonate (20 mL) and extracted with dichloromethane (3 ×