Chak and McAuley
189
suspension was refluxed for 12 h. After cooling to room
temperature, the reaction mixture was concentrated (rotovap)
and pump-dried. A crystalline white solid of the isothio-
uronium salt was obtained. A solution of NaOH (13 g,
0.325 mol) in 215 mL of water (6% NaOH) was prepared
and bubbled with nitrogen for 15 min. To the isothio-
uronium salt was added the deaerated 6% NaOH solution
and the reaction mixture was well-stirred and refluxed in a
nitrogen atmosphere for 2 h. After the mixture was cooled to
room temperature, and subsequently in an ice bath, 6 mol/L
HCl was added dropwise until the pH of the solution
reached 1. The milky solution obtained was saturated with
NaCl and extracted with 3 × 100 mL CH2Cl2. The organic
layers were combined and dried with anhydr. MgSO4, con-
centrated by rotovap, and pumped dry. The desired product
was isolated as a colorless viscous oil. Yield: 90%. 1H NMR
(90 MHz, CDCl3) δ: 7.35–7.75 (m, 4H, ArH), 3.20 (t, 4H,
J = 6 Hz, CH2NTs), 2.6 (q, 4H, J = 6 Hz, CH2S), 2.40 (s,
3H, CH2Ar), 1.90 (m, 4H, CH2CH2CH2), 1.45 (t, 2H, J =
6 Hz, SH). MS (CI): 318 [M + 1], 348 [M + 29], 360 [M +
41].
N,N′-Bis(2′-pyridylmethyl)-1,7-dithia-4,11-
diazacyclotetradecane (L4)
To a two-necked, round-bottomed flask equipped with a
magnetic stirrer, reflux condenser, and nitrogen inlet was
added a solution of L3 (1.30 g, 6.1 mmol), triethylamine
(4.5 mL, 32.3 mmol, 5 equiv.), and 2-(chloromethyl)pyridine
hydrochloride (2 g, 12.2 mmol) in 50 mL of absolute etha-
nol. The solution was heated to a gentle reflux under a nitro-
gen atmosphere for 12 h. After cooling to room temperature,
CHCl3 (3 × 100 mL) was added to the orange-red reaction
mixture. The organic phase was washed with water (5 ×
100 mL) and dried over anhydr. Na2SO4. CHCl3 was re-
moved by rotoevaporation and the brown oil obtained was
purified by column (silica gel, EtOAc–CH2Cl2, 60%:40%).
Fractions with a Rf value of 0.2 were collected. The title
product was obtained as a pale yellow oil that yielded clear
1
white crystals. Yield: 500 mg, 20%. H NMR (250 MHz,
CDCl3) δ: 8.42, 7.61, 7.56, 7.38, 7.07 (m, 8H, pyridine Hs),
3.74 (s, 2H, CH2-pyridine), 3.62 (s, 2H, CH2-pyridine),
2.60–2.73 (m, 8H, CH2S), 2.51 (t, J = 7 Hz, 8H, CH2N),
1.75 (tt, J = 7 Hz, 4H, CH2CH2CH2). 13C{1H} NMR
(CDCl3) δ: 159.9, 159.6 (quat. ArC), 148.8, 136.3, 136.1,
122.7, 122.6, 121.8, 121.7 (ArC), 61.3, 61.0 (CH2-pyridine),
52.6, 52.1 (CH2N), 29.3, 29.2 (SCH2), 27.1 (CH2CH2CH2).
MS (CI): 417 [M + 1], 445 [M + 29].
N,N′-Bistosyl-1,7-dithia-4,11-diazacyclotetradecane (6)
To a 5 L three-necked round flask equipped with a me-
chanical stirrer, condenser, and a dropping funnel was added
oven-dried Cs2CO3 (14.8 g, 0.0454 mol) and 1 L of freshly
opened DMF. The resulting suspension was stirred vigor-
ously in a nitrogen atmosphere and warmed to 50 °C. A so-
lution containing the dibromide (3) (4.82 g, 0.0125 mol) and
dithiol (5) (4 g, 0.0125 mol) in 500 mL of DMF was pre-
pared and bubbled in nitrogen for 20 min. This solution was
then added to the Cs2CO3–DMF suspension via high dilution
a rate of 4 to 5 mL/h. After the addition of all reactants, the
mixture was stirred overnight. Upon cooling to room tem-
perature, DMF was removed by rotatory evaporation. After
extraction of the residual pale yellow solid with CHCl3 sev-
eral times, the resultant yellow solution obtained was taken
to dryness and evacuated, yielding a pale brown oil that was
purified by column chromatography (silica gel, CH2Cl2–
EtOAc, 95%:5%). Fractions with Rf = 0.7 were collected.
The desired product was isolated as a white crystalline solid.
Syntheses of Co(II), Ni(II), and Cu(II) complexes
[Co(L2(CH3CN)(NO3)2]·CH3CN (complex A)
An acetonitrile solution of L2 (0.06 g, 0.175 mmol) in a
round-bottomed flask was purged with nitrogen for 20 min.
A solution of [Co(H2O)6](NO3)2 (0.0496 g, 0.17 mmol) in
acetonitrile was added dropwise to the ligand solution. The
reaction mixture, now pink, was stirred at room temperature
under a nitrogen atmosphere overnight to ensure complete
complexation before concentration to ~1 mL on the rotovap.
Slow evaporation of the solvent at room temperature yielded
pink crystals of X-ray quality. Yield: 40 mg. Anal. calcd. for
C20H32N6S3O6Co (%): C 39.51, H 5.31, N 13.83; found: C
38.91, H 5.20, N 13.46.
[Co(L2)(ClO4)](ClO4) (complex B)
1
Yield: 30%. H NMR (90 MHz, CDCl3) δ: 7.8 (m, ArH),
A solution of 0.57 g (0.156 mmol) of [Co(H2O)6](ClO4)2
in dry nitromethane was added dropwise to a similar N2-
purged solution of the ligand (0.0546 g, 0.159 mmol). The
mixture turned deep red instantly and was refluxed gently
under N2 for about 1 h. After cooling, the solvent was re-
moved and the resultant red oil was triturated with EtOH to
a reddish-brown solid that was dried in vacuo. Yield:
0.089 g (92%). Anal. calcd. for C16H26N2S3O8Cl2Co (%): C
31.07, H 4.56, N 4.53; found: C 30.97, H 4.26, N 4.67.
Compounds A and B are stable in air and, when dissolved
in acetonitrile or nitromethane, show different spectroscopic
characteristics and electrochemical behavior.
7.35 (m, ArH), 3.00–3.5 (m, CH2NTs), 2.5–2.9 (m, CH2S),
2.45 (s, CH3Ar), 2.00 (m, CH2CH2CH2). MS (CI): 543 [M +
1], 571 [M + 29].
1,7-Dithia-4,11-diazacyclotetradecane (L3)
A sample of (6) (0.5 g, 0.92 mmol) was added slowly un-
der a nitrogen atmosphere to a stirred suspension of LiAlH4
(0.41 g, 10.8 mmol) in 40 mL of dry THF. The reaction mix-
ture was stirred under reflux for 72 h. After cooling to room
temperature, the excess LiAlH4 was destroyed by dropwise
addition of 30 mL of THF–H2O (2:1 v/v). The mixture was
filtered and the precipitate was carefully washed with
CH2Cl2. Evaporation of the solvent afforded 150 mg of L3
as a white crystalline waxy solid, which was used for subse-
quent reactions without further purification. 1H NMR
(90 MHz, CDCl3) δ: 2.6–2.8 (m, 16H, CH2S, CH2N), 1.8
(m, 4H, CH2CH2CH2), 1.45 (s, 2H, NH). MS (CI): 235 [M +
1], 263 [M + 29], 275 [M + 41].
[Ni(L2(CH3CN)](ClO4)2·CH3CN
An acetonitrile solution of L2 (0.170 g, 0.496 mmol) was
purged with nitrogen for 20 min and a solution of
[Ni(H2O)6](ClO4)2 (0.145 g, 0.396 mmol) in acetonitrile was
added dropwise to the ligand solution. The reaction mixture
changed to purple and was stirred at room temperature under
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