Full Paper
ette (1 mm pathlength), gold-mesh minigrid working electrode,
platinum wire counter electrode, and an Ag/AgCl reference elec-
trode. All spectroelectrochemical experiments were performed
using anhydrous MeCN, with nBu4NPF6 (0.1m) as the supporting
electrolyte, and a RuII complex concentration of (0.5 mm).
Photoreduction of complexes [Ru(phen)2(dppz-o-CN)]2+ and [Ru-
(phen)2(dppz-p-CN)]2+ were performed in septum sealed, 1 cm
glass cuvettes (Starna). Samples were irradiated with a custom
diode light source which emits blue light (lmax =470 nm), de-
scribed previously.[21] Optimal spectra were recorded on a Hewlett–
Packard 8453 UV–visible spectrophotometer.
search shows CoCl2·6H2O can be used as a reductive catalyst in
NaBH4/EtOH systems, improving yields and reaction time.[8e] Adopt-
ing this procedure,
7 was prepared by stirring 6 (1.86 g,
10.0 mmol), in EtOH (100 mL) and THF (10 mL) with CoCl2·6H2O
(0.237 g, 0.996 mmol). The suspension was stirred for 15 min, then
NaBH4 (1.89 g, 50.0 mmol) was added in one portion. The mixture
was refluxed for 1.5 h, then NaBH4 (0.750 g, 20.0 mmol) was added
in one portion to the hot solution. After 30 min the flask was
cooled, and filtered through a bed of Celite. The solvent was re-
moved using a rotovap, and the residue was dissolved in H2O
(100 mL). The product was extracted with CH2Cl2 (3100 mL), and
the organic extracts were combined and dried with MgSO4. The or-
ganic extracts were filtered and the solvent removed to give 7,
which was used immediately in the next step. Yield 1.32 g (84%).
Chemical reductions and protonations were performed under N2
atmosphere in dry acetonitrile, with decamethyl cobaltocene
[(Cp*)2Co] as the reducing agent and trifluoroacetic acid (TFA) as
the proton source. Saturated solutions of decamethyl cobaltocene
were prepared in a glove-box under anaerobic conditions, and
subsequently filtered. The concentration of the stock solution was
determined by adding a known volume to a concentrated sample
of [[MV](PF6)2] in dry acetonitrile, (where [MV]2+ is 1,1’-dimethyl-
11,12-Dicyanodipyrido-[3,2-a:2’,3’-c]phenazine
Synthesis was preformed according to literature procedures.[8a] 1,2-
Diamino-4,5-dicyanobenzene (7; 1.32 g, 3.97 mmol) was suspended
with phendione (0.834 g, 3.97 mmol) in EtOH (50 mL) with K2CO3
(0.400 g, 2.88 mmol) and refluxed under N2 for 24 h. The slurry was
filtered and the filter cake was washed with hot H2O (100 mL), ace-
tone (50 mL), and diethyl ether (20 mL) then dried in vacuo. Yield
1.02 g (78%). 1H NMR (500 MHz, Zn(BF4)2 [D3]MeCN): d=8.29 (dd,
J=5.2, 2.7 Hz, 2H), 9.03 (s, 2H), 9.26 (d, J=6.3 Hz, 2H), 9.83 ppm
(d, J=9.7 Hz, 2H). IR (KBr): n˜ =2250 cmÀ1 (CN stretch)
4,4’-bipyridinium or methyl viologen) and quantifying the concen-
+
C
tration of the [MV ] generated, using the literature reported molar
absorptivity values of
e
(396 nm)=41500mÀ1 cmÀ1 and
e (608 nm)=13500mÀ1 cmÀ1 [22]
.
Synthesis
11,12-Dibromodipyrido-[3,2-a:2’,3’-c]phenazine
Synthesis was preformed according to literature procedure.[8c]
Phendione, (0.300 g, 1.42 mmol) was suspended in EtOH (50 mL)
with K2CO3 (0.200 g, 1.44 mmol), with 1,2-diamino-4,5-dibromoben-
zene (3; 0.380 g, 1.42 mmol). The solution was refluxed under N2
for 12 h. The slurry was filtered using a 0.2 mm nylon membrane.
The filter cake was washed with hot H2O (100 mL), acetone
(50 mL), and Et2O (20 mL) then dried in vacuo at 508C for 12 h.
Yield 0.512 g (82%). 1H NMR (500 MHz, Zn(BF4)2, [D3]MeCN): d=
8.23 (dd, J=4.6, 13.2 Hz, 2H), 8.58 (s, 2H), 9.22 (d, J=6.9 Hz, 2H),
9.65 ppm (d, J=9.7 Hz, 2H).
[Ru(phen)2(11,12-dicyanodipyrido-[3,2-a:2’,3’-c]phen-
azine)](PF6)2
[Ru(phen)2Cl2] (0.119 g, 0.225 mmol) and (dppz-o-CN) (0.083 g,
0.250 mmol) were added to EtOH (30 mL) and H2O (30 mL). The so-
lution was refluxed under N2 for 72 h and then filtered hot. An
aqueous solution of NH4PF6 (0.15 g, 0.89 mmol) in water (3 mL)
was added to the filtrate, causing immediate precipitation of
a brown solid. The mixture was filtered and the solid was washed
with 50 mL H2O (50 mL) and 50 mL diethyl ether (50 mL) and dried
in vacuo for 24 h. Yield 0.227 g (93%). CHN 1H NMR (500 MHz,
[D3]MeCN): d=7.63 (m, 4H), 7.77 (dd, J=5.4, 2.9 Hz, 2H), 7.98 (d,
J=5.2 Hz, 2H), 8.14 (d, J=5.2 Hz, 2H), 8.18 (d, J=4.0 Hz, 2H), 8.24
(s, 4H), 8.60 (t, J=7.5, 9.2 Hz, 4H), 9.07 (s, 2H), 9.56 ppm (d, J=
9.7 Hz, 2H). IR (KBr): n˜ =2250 cmÀ1 (CN stretch); ESI-MS:
[MÀ2(PF6)]2+: calcd: 396.9 m/z, found: 397.0; elemental analysis
calcd (%) for [Ru(phen)2(11,12-dicyanodipyrido-[3,2-a:2’,3’-c]phen-
azine)](PF6)2·2H2O (C44H28F12N10O2P2Ru): C 47.20, H 2.52, N 12.51;
found: C 47.36, H 2.35, N 12.08.
[Ru(phen)2(11,12-dibromodipyrido-[3,2-a:2’,3’-c]phenazine)]-
(PF6)2
[Ru(phen)2Cl2] (0.119 g, 0.225 mmol) and dppz-o-Br (0.110 g,
0.250 mmol) were added to EtOH (30 mL) and H2O (30 mL). The so-
lution was refluxed under N2 for 68 h, filtered and NH4PF6 (0.15 g,
0.89 mmol) was added to the filtrate. A red precipitate was formed
which was filtered and the solid washed with H2O (50 mL) and di-
ethyl ether (50 mL) and dried in vacuo at 508C for 12 h. Yield
1
0.219 g (82%). H NMR (500 MHz, [D3]MeCN): d=7.62 (m, 4H), 7.74
2,1,3-Benzothiadiazole (9), 4,7-dibromo-2,1,3-benzothiadiazole
(10), 1,2-diamino-3,6-dibromobenzene (11), and 10,13-dibro-
modipyrido-[3,2-a:2’,3’-c]phenazine
(dd, J=5.4, 13.8 Hz, 2H), 7.99 (d, J=6.8 Hz, 2H), 8.09 (d, J=6.3 Hz,
2H), 8.19 (d, J=6.9 Hz, 2H), 8.24 (s, 4H), 8.59 (t, J=7.5, 6.8 Hz, 4H),
8.79 (s, 2H), 9.52 ppm (d, J=9.2 Hz, 2H). CHN ESI-MS: [MÀ2(PF6)]2+
: calcd: 450.5 m/z, found: 450.536; elemental analysis calcd (%) for
[Ru(phen)2(11,12-dibromodipyrido-[3,2-a:2’,3’-c]phenazi-
ne)](PF6)2·H2O (C42H26Br2F12N8OP2Ru): C 41.71, H 2.17, N 9.26; found:
C 41.55, H 1.80, N 9.29.
The synthesis of compounds 9, 10, and 11 were previously re-
ported.[8e,f] Synthesis of 11 was performed according to literature
methods using CoCl2·6H2O as a reductive catalyst with NaBH4/
EtOH, and immediately used to synthesize (dppz-p-Br) according to
literature procedures.[8g] Compound (11; 1.32 g, 5.00 mmol) was
added to phendione (1.06 g, 5.02 mmol) and K2CO3 (0.400 g,
2.88 mmol) in EtOH (50 mL) and refluxed under N2 for 12 h. The
slurry was filtered and the filter cake was washed with hot H2O
(100 mL), acetone (50 mL), and diethyl ether (20 mL). The filter
cake was dried in vacuo. Yield 1.89 g (86%). 1H NMR (500 MHz,
Zn(BF4)2 [D3]MeCN): d=8.00 (s, 2H), 8.25 (dd, J=4.7, 13.2 Hz, 2H),
9.25 (d, J=6.3 Hz, 2H), 9.69 ppm (d, J=8.6 Hz, 2H).
5,6-Dibromo-2,1,3-benzothiadiazole (5), 5,6-dicyano-2,1,3-ben-
zothiadiazole (6), and 1,2-diamino-4,5-dicyanobenzene (7)
The synthesis of compounds 5 and 6 were previously reported.[8d]
Sulfur extrusion from 6 using NaBH4/EtOH as the reducing system,
was reported to give 7 in 53% yield. Due to the difficulty in reduc-
tive desulfurization of substituted diaminobenzene derivatives, re-
Chem. Eur. J. 2015, 21, 17314 – 17323
17321
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim