Articles
(85%) of pure fBDP. TLC (silica gel, toluene/ethyl acetate, 4:1)
Rf =0.30. H NMR (CDCl3, TMS) δ [ppm] 1.56 (s, 3H), 1.79 (s, 3H),
FWHM) was the excitation source. The experiments were
performed using rectangular quartz cells with right angle
geometry. The concentration of BDPÀ C60 was kept low (2.5 μM)
to avoid triplet-triplet annihilation. The laser beam was
defocused to cover all the path length (10 mm) of the analyzing
beam from a 150 W Xe lamp. The detection system was a PTI
monochromator coupled to a Hamamatsu R666 PM tube. The
signals were acquired and averaged by a digital oscilloscope
(Hewlett-Packard 54504) and then transferred to a computer.
1
2
3
4
5
6
7
8
9
1
2.62 (s, 3H), 2,83 (s, 3H), 3.06 (s, 6H, N(CH3)2), 6.15 (s, 1H, pyrrole),
6.81 (d, 2H, Ar, J=8.4 Hz), 7.07 (d, 2H, Ar, J=8.4 Hz), 10.04 (s,
1H, CHO). 13C NMR (100 MHz, CDCl3) δ [ppm] 11.5, 13.0, 14.8,
15.1, 40.5, 112.4, 123.8, 126.1, 128.9, 129.5, 132.0, 133.6, 135.6,
143.2, 147.1, 150.8, 156.3, 159.9, 185.9. ESI-MS [m/z] 396.2033
[M+H]+ (395.1980 calculated for C22H24BF2N3O). Anal. calcd C
66.85, H 6.12, N 10.63; found C 66.77, H 6.18, N 10.55%.
°
BDPÀ C60. A solution of fBDP (50 mg, 0.12 mmol), C60 (91 mg,
0.12 mmol), and N-methylglycine (11 mg, 0.12 mmol) in 60 mL
of anhydrous toluene was stirred under reflux in argon for 10 h.
The solvent was removed under reduced pressure and the
product was purified by flash column chromatography (silica
gel, toluene/cyclohexane (5:1) to toluene gradient), affording
47 mg (34%) of pure BDPÀ C60. TLC (silica gel, toluene) Rf =0.62.
1H NMR (400 MHz, CDCl3) δ [ppm] 1.57 (s, 3H), 1.73 (s, 3H), 2.69
(s, 3H), 2.74 (s, 3H, NCH3, pyrrolidine ring), 2.81 (s, 3H), 3.04 (s,
6H, N(CH3)2), 4.12 (d, 2H, pyrrolidine ring, J=9.5 Hz), 4.92 (s, 1H,
pyrrolidine ring), 5.06 (d, 1H, pyrrolidine ring, J=9.5 Hz), 6.00 (s,
1H, pyrrole), 6.84 (d, 2H, Ar, J=8.5 Hz), 7.15 (d, 2H, Ar, J=
8.5 Hz). 13C NMR (100 MHz, CDCl3) δ [ppm] 11.7, 13.2, 14.6, 15.0,
40.3, 68.7, 69.8, 76.2, 82.6, 112.3, 123.6, 124.2, 126.2, 128.8,
129.6, 131.8, 133.7, 135.1, 135.7, 136.0, 136.3, 139.5, 139.7,
140.2, 141.3, 141.6, 141.7, 141.8, 141.9, 142.0, 142.1, 142.2,
142.4, 142.4, 142.5, 142.8, 142.9, 143.3, 144.2, 144.3, 144.4,
144.9, 145.0, 145.1, 145.2, 145.3, 145.4, 145.6, 145.8, 145.9,
146.0, 146.1, 146.3, 146.5, 147.0, 147.1, 150.7, 152.8, 153.1,
153.9, 156.2 156.4, 159.8. ESI-MS [m/z] 1143.2561 [M+H]+
(1142.2453 calculated for C84H29BF2N4). Anal. calcd C 88.27, H
2.56, N 4.90; found C 88.14, H 2.63, N 4.86%.
All determinations were performed at 25 C and the solutions
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
were de-oxygenated by bubbling with solvent-saturated high
purity argon for at least 20 min.
2.5. Computational Details
Density funtional therory (DFT) calculations were performed
using Gaussian 09 software (Gaussian, Wallingford, CT) with the
B3LYP functional coupled with the 6-31G(d) basis set. Geo-
metries for all structures were fully optimized, and conforma-
tional searches were performed to locate the minimum-energy
conformers of all of the structures. Initially, a large number of
geometries were generated through the conformational search
modules of Spartan’14 (Wavefunction, Inc., Irvine.) using MMFF
force field and then subjected to AM1 optimization. All
structures were then successively re-optimized at the B3LYP/6-
31 G(d) levels of theory. TDDFT calculations were carried out at
the CAM-B3LYP/6-31 G(d) level of theory. This hybrid exchange-
correlation functional is the long-range corrected version of
B3LYP that accounts for the true asymptotic behavior at long
interelectronic distances.[25]
2.3. Spectroscopic Studies
2.6. Electrochemical Studies
UV-visible absorption and fluorescence spectra were recorded
in toluene and DMF using a quartz cell of 1 cm path length at
The voltammetric characterization of the redox processes was
performed with a potentiostat-galvanostat Autolab (Electro-
chemical Instruments, Utrecht, The Netherlands) using a Pt
working electrode, a Pt counter electrode and a silver wire
quasi/reference electrode in a conventional three-electrode
cell.[26] Electrochemical studies of aBDP, MC60 and BDPÀ C60 were
carried out in o-dichlorobenzene (o-DCB) deoxygenated solu-
tion (nitrogen bubbling) with 0.1 M tetra-n-butylammonium
tetrafluoroborate (TBABF4) as the supporting electrolyte at
room temperature. All measurements were conducted with a
scan rate of 100 mVsÀ 1. The Pt working electrode was cleaned
between experiments by polishing with 0.3 mm alumina paste
followed by solvent rinses. After each voltammetric experiment,
ferrocene was added as an internal standard and the potential
axis was calibrated against the formal potential for the
saturated calomel electrode (SCE).
°
25.0�0.5 C. The steady-state fluorescence emission spectra
were performed exciting the samples at λexc =480 nm in the
solvents indicated above. Absorbances (<0.05) were matched
at the excitation wavelength and the areas of the emission
spectra were integrated in the range of 490–700 nm. The
fluorescence quantum yield (ΦF) of aBDP and the constitutive
BDP of the dyad were determined by comparison of the area
below the corrected emission spectrum with that of fluorescein
as a reference (ΦF =0.92 in 0.1 M NaOH) and considering the
refractive index of the solvents.[23] Absorption and emission
spectra of BDPÀ C60 were recorded in DMF varying the
concentration (0–0.129 M) of trifluoroacetic acid (TFA).
2.4. Transient Absorption Measurements
Transient absorption spectra of BDPÀ C60 were determined in Ar-
2.7. Photodecomposition of 1,3-Diphenylisobenzofuran (DPBF)
saturated solutions of toluene, DMF and DMF/TFA (0.129 M) by
laser flash photolysis.[24]
A
Spectron SL400 Nd:YAG laser
Solutions of DPBF (20 μM) and photosensitizer in 2 mL of
toluene or DMF were irradiated in 1 cm path length quartz cells
generating 532 nm laser pulses (12 mJ per pulse, ca. 18 ns 120
ChemPhysChem 2019, 20, 1–17
3
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!