Journal of the American Chemical Society
Article
aerobically oxidized by suspending and stirring in ethanol with 1 equiv
HBr(aq) overnight (18 h) in air, resulting in the green solid product
[Co(PDI-Py)]Br3 (488.2 mg, yield: 55.0%). H NMR (DMSO-d6,
the light precipitate [Zn(PDI-R)]Br2 (yield: 25.0%−45.0%) was
collected by filtration and then washed with cold ethanol and diethyl
ether three times.
1
400 MHz, Figure S7): δ 8.96−9.08 (4H, s,s, Py-H), δ 8.30 (2H, s, Py-
H), δ 6.69−6.74 (H, t, −CH2NHCH2−), δ 4.20−4.24 (2H, d,
−CH2NHCH2−), δ 3.54−3.61 (2H, t, −CN−CH2−), δ 3.20−3.33
(4H, m, −CH2CH2CH2− and −CH2NHCH2−), δ 3.06 (6H, s, CH3),
δ 2.25−2.30 (2H, m, −CH2CH2CH2−), δ 2.04−2.15 (2H, m, −C
N−CH2−). Anal. Calcd (found) for [Co(PDI-Ph)]Br3
(C20H25N5CoBr3): %C, 37.88 (37.37); %H, 3.97 (4.08); %N, 11.04
(10.84).
[Zn(PDI)]Br2. 1H NMR (DMSO-d6, 400 MHz, Figure S9): δ 8.61−
8.65 (H, t, Py-H), δ 8.50−8.52 (2H, d, Py-H), δ 4.49−4.55 (H, t,
−CH2NHCH2−), δ 4.13−4.18 (2H, d, −CH2NHCH2−), δ 3.73−
3.79 (2H, t, −CN−CH2−),
δ 3.13−3.19 (2H, m,
−CH2CH2CH2−), δ 2.93−2.96 (2H, d, −CH2NHCH2−), δ 2.60
(6H, s, CH3), δ 2.10−2.16 (2H, d, −CH2CH2CH2−), δ 1.61−1.71
(2H, m, −CN−CH2−). Anal. Calcd (found) for [Zn(PDI)]Br2
(C15H22N4ZnBr2): %C, 37.26 (37.17); %H, 4.59 (4.51); %N, 11.59
(10.89).
1
[Zn(PDI-Ph)]Br2. H NMR (DMSO-d6, 400 MHz, Figure S10): δ
Scheme 7. Synthesis Route for [Co(PDI-Py)]Br3
8.74 (2H, s, Py-H), δ 8.14−8.17 (2H, d, Phenyl-H), δ 7.65−7.67 (3H,
m, Phenyl-H), δ 4.50−4.56 (H, t, −CH2NHCH2−), δ 4.16−4.20 (2H,
d, −CH2NHCH2−), δ 3.75−3.81 (2H, t, −CN−CH2−), δ 3.12−
3.21 (2H, m, −CH2CH2CH2−),
δ 2.94−2.98 (2H, d,
−CH2NHCH2−), δ 2.69 (6H, s, CH3), δ 2.13−2.17 (2H, d, −C
N−CH2−), δ 1.62−1.72 (2H, m, −CH2CH2CH2−). Anal. Calcd
(found) for [Zn(PDI-Ph)]Br2 (C21H26N4ZnBr2): %C, 45.07 (45.78);
%H, 4.68 (4.86); %N, 10.01 (10.43).
1
[Zn(PDI-Py)]Br2. H NMR (DMSO-d6, 400 MHz, Figure S11): δ
8.88−8.90 (2H, d, Py-H), δ 8.84 (2H, s, Py-H), δ 8.15−8.17 (2H, d,
Py-H), δ 4.49−4.55 (H, t, −CH2NHCH2−), δ 4.17−4.20 (2H, d,
−CH2NHCH2−), δ 3.76−3.82 (2H, t, −CN−CH2−), δ 3.11−3.20
(2H, m, −CH2CH2CH2−), δ 2.95−2.98 (2H, d, −CH2NHCH2−), δ
2.69 (6H, s, CH3), δ 2.14−2.17 (2H, d, −CN−CH2−), δ 1.62−
1.72 (2H, m, −CH2CH2CH2−). Anal. Calcd (found) for [Zn(PDI-
Py)]Br2 (C20H25N5ZnBr2): %C, 42.85 (43.02); %H, 4.49 (4.50); %N,
12.49 (13.08).
+ −
Preparation of [Co(PDI-Py-CH3 I )]Br3. A scheme for the synthesis
+ −
of [Co(PDI-Py-CH3 I )]Br3 is shown in Scheme 8. 4-(N-Methyl-4-
pyridyl)-2,6-diacetylpyridine (DAP-Py-CH3 I , 352 mg, 0.92 mmol)
+ −
was dissolved in 8 mL of MeCN and 1 mL of ethanol. A 4.00 mL
ethanol solution of CoBr2 (201 mg, 0.92 mmol) was added into this
mixture with stirring under N2. Then 3,3′-diaminodipropylamine
(128.18 μL, 0.92 mmol) was slowly dropped in. The mixture was
stirred and refluxed at 55 °C for 24 h. After the mixture was allowed
to cool to room temperature, the dark precipitate [Co(PDI-Py-
+ −
1
[Zn(PDI-Py-CH3 I )]Br2. H NMR (DMSO-d6, 400 MHz, Figure
S12): δ 9.33−9.35 (2H, d, Py-H), δ 9.03 (2H, s, Py-H), δ 8.94−8.95
(2H, d, Py-H), δ 4.51−4.57 (H, t, −CH2NHCH2−), δ 4.47 (3H, s,
+ −
+
CH3 I )]Br2 was collected by filtration and then washed with cold
ethanol three times. [Co(PDI-Py-CH3 I )]Br2 was aerobically
N−CH3 ), δ 4.19−4.22 (2H, d, −CH2NHCH2−), δ 3.77−3.84 (2H,
+ −
t, −CN−CH2−), δ 3.12−3.20 (2H, m, −CH2CH2CH2−), δ 2.97−
3.00 (2H, d, −CH2NHCH2−), δ 2.72 (6H, s, CH3), δ 2.15−2.19 (2H,
d, −CN−CH2−), δ 1.65−1.75 (2H, m, −CH2CH2CH2−). Anal.
oxidized by suspending and stirring in ethanol with 1 equiv of
HBr(aq) overnight (18 h) in air, resulting in the brown solid product
+ −
[Co(PDI-Py-CH3 I )]Br3 (202 mg, yield: 28.3%). 1H NMR (DMSO-
+ −
Calcd (found) for [Zn(PDI-Py-CH3 I )]Br2 (C21H28N5ZnIBr2): %C,
d6, 400 MHz, Figure S8): δ 9.37−9.39 (2H, d, Py-H), δ 9.27 (2H, s,
35.90 (36.04); %H, 4.02 (4.08); %N, 9.97 (10.16).
Py-H), δ 9.00−9.02 (2H, d, Py-H), δ 6.74−6.79 (H, t,
Electrochemical Methods and Product Analysis. Electro-
chemical experiments were conducted using a Bio-Logic SP-200
potentiostat/galvanostat with data recorded using the Bio-Logic EC-
Lab V10.44 software package. In all measurements, the reference
electrode was a Ag/AgNO3 (1.0 mM in MeCN with 0.1 M
nBu4NPF6) nonaqueous reference electrode separated from the
solution by a CoralPor glass frit (Bioanalytical Systems, Inc.) and
externally referenced to the ferrocenium/ferrocene redox couple
(Fc+/0).
+
−CH2NHCH2−), δ 4.48 (3H, s, N−CH3 ), δ 4.21−4.25 (2H, d,
−CH2NHCH2−), δ 3.55−3.62 (2H, t, −CN−CH2−), δ 3.24−3.31
(4H, m, −CH2CH2CH2− and −CH2NHCH2−), δ 3.08 (6H, s, CH3),
δ 2.27−2.32 (2H, m, −CH2CH2CH2−), δ 2.04−2.14 (2H, m, −C
+
N−CH2−). Anal. Calcd (found) for [Co(PDI-Py-CH3 I−)]Br3
(C21H28N5CoIBr3): %C, 32.50 (33.02); %H, 3.64 (3.40); %N, 9.02
(9.16).
+ −
Scheme 8. Synthesis Route for [Co(PDI-Py-CH3 I )]Br3
Cyclic Voltammetry (CV) under N2 and CO2. Cyclic voltammo-
grams were conducted in quiescent solution, using a 0.071 cm2 glassy
carbon disk working electrode (CH instruments), a Ag/AgNO3 (1.0
mM in MeCN with 0.1 M nBu4NPF6) nonaqueous reference
electrode, and a carbon rod auxiliary electrode (99.999%, Strem
Chemicals). Electrolyte solutions contained 0.1 M nBu4NPF6 in
MeCN with reported concentrations of H2O. The typical scan rate for
reported CVs was 0.050 V/s unless otherwise noted. Prior to each
measurement, the electrolyte solution was sparged with either N2 or
CO2 as indicated for at least 10 min, and the headspace was then
blanketed with the same gas during the measurement. To avoid
electrolyte evaporation, all gases were saturated with MeCN before
use by first bubbling them through a gas-washing bottle filled with
MeCN. The uncompensated solution resistance (Ru ≈ 120 Ω) in the
cell was measured using a single-point impedance measurement at
100 kHz with a 20 mV amplitude about the open-circuit potential
before each set of measurements. CVs were automatically corrected
for iR drop at 85% through positive feedback using the Bio-Logic EC-
Lab software.
Preparation of [Zn(PDI-R)]Br2. The general synthesis methods for
the [Zn(PDI-R)]Br2 complexes are analogous to those for the
[Co(PDI-R)]Br2 complexes. Briefly, the relevant DAP-R compound
(0.92 mmol) was dissolved in 8 mL of MeCN and 1 mL of ethanol. A
4.00 mL ethanol solution of ZnBr2 (207 mg, 0.92 mmol) was added
into this mixture with stirring under N2. Then 3,3′-diamino-
dipropylamine (128.18 μL, 0.92 mmol) was slowly dropped in. The
mixture was stirred and refluxed at 70 °C for 24 h. After the mixture
was allowed to cool to room temperature, diethyl ether was added and
For all the calculations of kinetic parameters in our study, EC0 O
=
2
−1.36 V vs Fc+/0 (−0.72 V vs SHE) is used as the thermodynamic
3767
J. Am. Chem. Soc. 2021, 143, 3764−3778