244 Smita Dayal et al.
1
CH
ptopropyltrimethoxysilane (8.5 g) and tetrahydrofuran (50 mL) was
treated dropwise with a CH MgCl-tetrahydrofuran solution (50 mL).
The reaction mixture was stirred for 1 h and then treated dropwise with
CH
with a tetrahydrofuran-diethyl ether solution (1:8, 90 mL), and filtered.
The solid was washed (diethyl ether), and the washings and filtrate were
combined and concentrated by rotary evaporation at room tempera-
3
OSi(CH
3
)
2
(CH
2
)
3
SH, 1. Under Ar, a 0ꢀC solution of 3-merca-
oil was distilled (40 torr, 83–92ꢀC) and weighed (1.23 g, 32%). NMR
(CDCl ): d 3.40 (s, 3H, CH O), 1.32 (m, 2H, Si(CH CH ), 1.20 (m,
2H, SiCH CH ), 0.87 (s, 9H, Si(CH CCH ), 0.78 (m, 2H, SiCH ),
0.08 (s, 6H, SiCH ).
6 is colorless oil.
SiPc[OSi(CH (CH
(316 mg) and a suspension of SiPc(OH)
3
3
2
)
2
2
3
2
2
2
)
3
3
2
3
3
OH (40 mL), both being done at low temperature (0ꢀC), diluted
3
)
2
2
)
3
C(CH
3
)
3
]
2
, Pc 110, 7. A mixture of silanol 6
(150 mg) and pyridine
2
(70 mL) that had been dried by distillation (4 mL of distillate) was
distilled (14 mL of distillate) for 2 h, and the residual was evaporated
to dryness by rotary evaporation (40ꢀC). The solid was chromato-
O III, hexanes-CH Cl solution, 4:1), vacuum-dried
2 3 2 2
(60ꢀC) and weighed (187 mg, 81%). UV–Vis (toluene) kmax, nm: 668.
ture. The concentrate was distilled (60 torr, 90–110ꢀC) and weighed
1
3.8 g, 54%). H NMR (C
(
6
D
6
3
): d 3.21 (s, 3H, OCH ), 2.24 (q, 2H,
Si(CH
SiCH
is a colorless liquid. It is soluble in CH
toluene and hexanes.
SiPc[OSi(CH (CH
SiPc(OH) (135 mg), silane 1 (1.60 g), and pyridine (80 mL) was
2
)
2
CH
2
), 1.49 (m, 2H, SiCH
2
CH
2
), 1.14 (t, 1H, SH), 0.47 (m, 2H,
graphed (Al
2
), 0.04 (s, 6H, SiCH
3
).
1
1
2
Cl
2
, dimethylformamide,
H NMR (300 MHz, C
3-Pc H), 0.42 (s, 18H, Si(CH
)1.11 (m, 4H, SiCH CH ), )2.09 (m, 4H, SiCH
SiCH
6
D
6
): d 9.72 (m, 8H, 1, 4-Pc H), 7.89 (m, 8H, 2,
CCH ), 0.11 (m, 4H, Si(CH CH ),
), )2.60 (s, 12H,
Si , 886.3991;
2
)
3
3
2
)
2
2
3
)
2
2
)
3
SH]
2
, Pc 93, 2. Under Ar, a mixture of
2
2
2
+
2
3
). HRMS-FAB (m ⁄ z): [M] calcd for C50
H
58
N
8
O
2
3
distilled (5 mL of distillate) for 1 h, and evaporated to dryness by
rotary evaporation (30ꢀC). The solid was chromatographed (basic-
Al O III, CH Cl -ethyl acetate solution, 5:1), air-dried, and weighed
2 3 2 2
found 886.3985, 886.3999.
7 is a blue solid. It is soluble in CH
toluene, and insoluble in hexanes.
Synthesis of QD-Pc conjugates. The Pcs (18–24) were dissolved in
2 2
Cl , dimethylformamide and
1
(
9
190 mg, 96%). UV–Vis (toluene) kmax, nm: 669. H NMR (C
.72 (m, 8H, 1, 4-Pc H), 7.87 (m, 8H, 2, 3-Pc H), 0.91 (q, 4H,
Si(CH CH ), 0.39 (t, 2H, SH), )1.02 (m, 4H, SiCH CH ), )2.22 (t,
H, SiCH ), )2.68 (s, 12H, SiCH ): d 148.9 (5-Pc
C), 136.3 (4a-Pc C), 131.1 (2, 3-Pc C), 123.9 (1, 4-Pc C), 27.1
Si(CH CH ), 27.0 (SiCH CH ), 15.3 (SiCH ), )3.2 (SiCH ).
is a blue solid. It is soluble in CH Cl , dimethylformamide and
toluene, and insoluble in hexanes.
HOSiPcOSi(CH (CH SH, Pc 219, 3. A mixture of phthalocy-
anine 2 (114 mg) and a solution of trichloroacetic acid (150 mg) in
CH Cl (100 mL) was stirred at room temperature for 1.5 h, treated
with pyridine (20 mL) and then H O (100 mL), and separated. The
aqueous portion of the reaction product was washed (CH Cl ), and the
6
D
6
): d
anhydrous toluene and mixed with QD solutions. QD and Pc
concentrations of 5 · 10 and 8 · 10 M were used to obtain high
ET efficiency and to keep Pc self-quenching low.
)
5
)5
2
)
2
2
2
2
1
3
4
2
3 3
). C NMR (CDCl
Photophysical studies. The synthesized QDs and conjugates were
studied by steady-state absorption (Varian Cary 50) and fluorescence
(Varian Eclipse fluorescence spectrophotometer) spectroscopy. A
500 nm wavelength light excitation was used for all the spectroscopic
studies. It should be emphasized that one can excite the QDs exclusively
if 500 nm light is used because the Pcs do not appreciably absorb at this
wavelength. The Pc emission peak observed near 675 nm is therefore due
solely to ET from the photoexcited QDs. QDs with an emission at
625 nm were used so as to have sufficient spectral overlap for good ET
with the Pcs used, all of which have very similar absorption profiles.
For the study of ET dynamics, pure QDs and QD-conjugates were
investigated by fs time-resolved laser spectroscopy after 24 h of
conjugation time. It was found that 24 h is the optimum time for
conjugation (6), when maximum quenching of the QD emission occurs
while at the same time the Pc fluorescence could be detected.
Broadband fs-laser pulses were used to probe the dynamics at the fs
time scale between 450 and 750 nm. The laser setup has been discussed
previously (25,26). For the fs measurements, 2 mm quartz cuvettes
were used. All experiments were carried out at room temperature.
Absorption spectra were collected before and after the time-resolved
measurements. No changes in the absorption spectra were detected.
(
2
)
2
2
2
2
2
3
2
2
2
3
)
2
2 3
)
2
2
2
2
2
washings and the organic portion of the reaction product were
combined and concentrated by rotary evaporation (room tempera-
ture). The concentrate was passed down an Al
2 3
O column (basic-
Al V, CH Cl -ethyl acetate solution, 10:1), and evaporated to
2
2
O
3
2
dryness by rotary evaporation (room temperature). The solid was
washed (acetonitrile), air-dried and weighed (52 mg, 50%). UV–Vis
1
(
7
toluene) kmax, nm: 680. H NMR (C
6
D
6
): d 9.67 (m, 8H, 1, 4-Pc H),
CH ), 0.36 (t, 1H, SH),
), )2.64 (s, 6H, SiCH ).
): 149.9 (5-Pc C), 135.8 (4a-Pc, C), 131.6 (2, 3-Pc, C),
24.2 (1, 4-Pc, C), 27.0 (Si(CH CH ), 26.8 (SiCH CH ), 15.0
). HRMS-MALDI (m ⁄ z): [M-OH] calcd for
, 689.1724; found 689.1690.
Cl
.84 (m, 8H, 2, 3-Pc H), 0.90 (q, 2H, Si(CH
1.00 (m, 2H, SiCH CH ), )2.19 (t, 2H, SiCH
3
2
)
2
2
)
2
2
2
3
1
C NMR (CDCl
3
1
2
)
2
2
2
+
2
(SiCH
2
), )3.2 (SiCH
OSSi
3
C
37
H
29
N
8
2
3
is a blue solid. It is soluble in CH
toluene, and insoluble in hexanes.
HOSi(CH (CH CH , 4. n-Butyldimethylchlorosilane (5.0 mL)
was added to a cool (ice bath) solution of H O (1.0 mL), N(C
5.0 mL) and ether (50 mL), and the mixture was stirred for 1 h at
2
2
, dimethylformamide and
RESULTS AND DISCUSSION
3
)
2
2
)
3
3
The synthesis of Pc 93, Pc 219, Pc 109 and Pc 110 is
summarized in Scheme 1. The reactions used to prepare the
precursors for Pc 219, Pc 109 and Pc 110 and those used to
prepare the compounds themselves follow reactions developed
earlier for similar molecules (18–20). The molecules used in
this study are depicted in Fig. 1.
2
2 5 3
H )
(
room temperature and filtered. The filtrate was concentrated to an oil
by rotary evaporation (30ꢀC), and the oil was weighed (3.09 g, 81%),
1
H NMR (C
CH
is a colorless oil.
SiPc[OSi(CH (CH
257 mg) and a suspension of SiPc(OH)
that had been dried by distillation (9 mL of distillate) was distilled
34 mL of distillate) for 2 h, and the residual was evaporated to dryness
by rotary evaporation (40ꢀC). The solid was chromatographed (Al I,
6
D
6
): d 1.28 (m, 4H, SiCH
2
(CH
2
)
2
), 0.86 (t, 3H,
Si(CH
2
)
3
3
), 0.48 (m, 2H, SiCH
2
), 0.01 (s, 6H, SiCH
3
).
4
3
)
2
2
)
3
CH
3
]
2
, Pc 109, 5. A mixture of silanol 4
(150 mg) and pyridine (70 mL)
(
2
The effects of axial group functionalization on ET
(
To study the effects of functionalization of the siloxy ligands of
the Pcs and those of the number (one or two) of functionalized
siloxy ligands on ET efficiency, conjugates of the QDs with
various Pcs were studied. The terminology used for the parts of
the axial ligands is explained in Fig. 2.
2
O
3
toluene), washed (hexanes), vacuum-dried (60ꢀC), and weighed (60 mg,
1
2
1
4
)
Si
9%). UV–Vis (toluene) kmax, nm: 668. H NMR (C
, 4-Pc H), 7.88 (m, 8H, 2, 3-Pc H), 0.12 (t, 6H, Si(CH
H, Si(CH CH ), )1.14 (m, 4H, SiCH CH ), )2.10 (m, 4H, SiCH
2.62 (s, 12H, SiCH ). HRMS-FAB (m ⁄ z): [M] calcd for C44
, 802.3052; found 802.3068, 802.3056.
is a blue solid. It is soluble in CH
toluene, and slightly soluble in hexanes.
CH OSi(CH (CH C(CH , 6. A solution of 4, 4-dimethyl-1-
6
D
6
): d 9.73 (m, 8H,
CH ), )0.08 (m,
),
2
)
3
3
2
)
2
2
2
2
2
+
3
46 8 2-
H N O
3
Effect of axial ligand functionalization on ET-amino vs thiol
functions. The effect of axial ligand functionalization was
studied by conjugating Pc 4 and Pc 219 to CdSe QDs. Pc 4 has
a dimethylamino group as axial ligand function while Pc 219
has a thiol function (Fig. 1). Figure 3a shows the steady-state
absorption and emission spectra of the QDs and their
conjugates. A higher quenching efficiency of QD emission
5
2 2
Cl , dimethylformamide and
3
3
)
2
2
)
3
3 3
)
pentene (2.01 g), dimethylchlorosilane (4.0 mL) and platinum-divin-
yltetramethyldisiloxane complex in xylene (Gelest, 2.1–2.4% Pt in
xylenes, 0.1 mL) in a pressure tube was warmed (60ꢀC) for 2 days,
purged with Ar at elevated temperature (60ꢀC), treated with CH
3
OH
(
5 mL) and concentrated to an oil by rotary evaporation (30ꢀC). The