L.J. Carlson et al. / Inorganica Chimica Acta 365 (2011) 159–166
161
6.97 (t, 1H), 7.10 (d, 1H), 7.41 (d, 1H). Selected IR bands: (cmꢂ1
1579 (m), 1458 (m), 1009 (m), 731(s).
)
di-Py(Bt). Light yellow solid. Yield: 78%. 1H NMR (CDCl3,
200 MHz, 25 oC, d from TMS): 4.99 (s, 2H, NH), 6.33 (d, 2H), 6.78
(t, 4H), 6.97 (m, 4H), 7.48 (d, 2H), 7.71 (t, 1H). Selected IR bands:
(cmꢂ1) 1582 (m), 1474 (s) 1320 (s), 1262 (m), 976 (m), 743 (s).
di-Th(Bt). Beige solid. Yield: 65%. 1H NMR (CDCl3, 200 MHz, 25
oC, d from TMS): 4.46 (s, 2H, NH), 6.51 (d, 2H), 6.65 (d, 2H), 6.77
(t, 2H), 6.93 (m, 4H), 7.04 (d, 2H). Selected IR bands: (cmꢂ1) 1579
(w), 1471 (s), 1457 (s), 1326 (m), 1250 (m), 1037 (m), 741(s).
2.3.2. Thiazole derivatives
Fig. 2. Disulfide derivatives containing free imine group (R = 2-pyridine (PyIS)2 or
The complete oxidation of the benzothiazoline derivatives was
accomplished by vigorously stirring a chloroform solution of each
at room temperature in an open flask for ꢁ5 h. The solvent was
then removed via rotary evaporation and the residue dried under
high vacuum for 10 h. Quantitative yields. A detailed procedure
for Th(oBt) is given below followed by the spectroscopic character-
ization for each benzothiazole analog.
2-thiophene (ThIS)2).
following published procedures [24]. All solvents and chemicals
were of reagent grade and used without further purification.
2.2. Physical measurements
Th(oBt). A batch of 500 mg (2.28 mmol) of Th(Bt) was dissolved
in 40 mL CHCl3 and stirred. After 5 h, the solvent was removed via
rotary evaporation and the brown-yellow solid dried under high
vacuum. Yield: 495 mg (100%). 1H NMR (CDCl3, 200 MHz, 25 °C, d
from TMS): 7.15 (d, 1H), 7.45 (m, 3H), 7.67 (d, 1H), 7.86 (d, 1H),
8.04 (d, 1H). Selected IR bands: (cmꢂ1) 1590 (w), 1542 (m), 1478
(m), 1434 (s), 1417 (s), 1311 (m), 911 (m), 695 (s).
Infrared spectra were obtained with a Thermoelectron, Avatar
330 FT-IR spectrophotometer equipped with a Smart Orbit reflec-
tance insert, diamond window. Absorption spectra were measured
on a Hewlett–Packard 8453 diode array spectrophotometer. 1H
NMR spectra were recorded on a Varian 200 MHz spectrometer.
Py(oBt). Yellow solid. 1H NMR (CDCl3, 200 MHz, 25 °C, d from
TMS): 7.42 (m, 3H), 7.85 (t, 1H), 7.97 (d, 1H), 8.11 (d, 1H), 8.38
(d, 1H), 8.71 (d, 1H). Selected IR bands: (cmꢂ1) 1585 (m), 1456
(m), 1433 (s), 1317 (m), 996 (m), 980 (s), 739 (s).
2.3. Preparation of analogs
2.3.1. Benzothiazoline derivatives
A similar method was used to prepare each benzothiazoline
derivative; First 1 equiv of the aldehyde was dissolved in 20–
25 mL of ethanol (EtOH). The solution was degassed and, under a
Fu(oBt). Beige solid. 1H NMR (CDCl3, 200 MHz, 25 °C, d from
TMS): 6.61 (m, 1H), 7.21 (d, 1H), 7.46 (m, 2H), 7.62 (d, 1H), 7.90
(d, 1H), 8.06 (d, 1H). Selected IR bands: (cmꢂ1) 1579 (w), 1502
(s), 1433 (m) 1171 (s), 1312 (m), 1244 (s), 1009 (s), 895 (s), 743
(s), 730 (s).
N
2 atmosphere, 1 equiv of neat ABT was added to it (2 equiv were
used for di-Py(Bt) and di-Th(Bt)). The reaction was then refluxed
for 2 h and the solvent immediately removed in vaccuo. Upon
reducing the volume of solvent, the thiazoline product precipitated
from solution. When approximately 10 mL of solvent remained the
solid was collected, washed with 5 mL of hexanes and dried under
vacuum for 10 h. In the case of the furan derivative, Fu(Bt), the pro-
cedure resulted in the formation of an oil which formed a solid
when triturated with diethyl ether (Et2O). The solid was collected
in a similar manner and dried under vacuum for 24 h. Yields for
the ligands ranged from 40–80%. In all cases care was taken to min-
imize exposure to oxygen. A detailed procedure for Th(Bt) is given
below followed by the spectroscopic characterization for each ben-
zothiazoline analog.
Th(Bt). First, 0.75 mL (8.18 mmol) of 2-thiophenecarboxalde-
hyde was in dissolved 25 mL of EtOH and 0.88 mL (8.18 mmol) of
ABT was added to it. The solution was refluxed for 2 h and then
carefully placed under vacuum to slowly reduce the solvent. A light
yellow powder began to form as the volume of solvent decreased.
When ꢁ10 mL of solvent remained, the solid was quickly collected
on a Büchner funnel, washed with ꢁ5 mL of hexane, and immedi-
ately dried under high vacuum for 10 h. Yield: 1.36 g (76%). 1H
NMR (CDCl3, 200 MHz, 25 °C, d from TMS): 4.51 (s, 1H, NH), 6.63
(s, 1H), 6.69 (d, 1H), 6.80 (t, 1H), 6.95 (m, 2H), 7.06 (t, 1H), 7.12
di-Py(oBt). Light yellow solid. 1H NMR (CDCl3, 200 MHz, 25 °C, d
from TMS): 7.50 (m, 4H), 8.07 (m, 5H), 8.47 (d, 2H). Selected IR
bands: (cmꢂ1) 1565 (m), 1447 (m), 1319 (m), 974 (m), 816 (m),
719 (s).
di-Th(oBt). Beige solid: 1H NMR (CDCl3, 200 MHz, 25 °C, d from
TMS): 7.46 (m, 4H), 7.69 (s, 2H), 7.89 (d, 2H), 8.08 (d, 2H). Selected
IR bands: (cmꢂ1) 1547 (m), 1429 (s), 1312 (s), 1237 (s), 896 (m),
759 (s), 724 (s).
2.3.3. Disulfide derivatives
The syntheses of (ThIS)2 and (PyIS)2 are analogous and were
each carried out in a two step process. First, bis-aminothiophenol
disulfide was prepared following published procedure [25]. Next,
a batch of the disulfide, (2 equiv, ꢁ2 mmol scale) was dissolved
in a minimum amount of EtOH and was then added to one equiv
of the corresponding aldehyde dissolved in ꢁ25 mL of EtOH (2-pyr-
idinecarboxaldehyde for (PyIS)2, 2-thiophenecarboxaldehyde for
(ThIS)2). The reaction was refluxed for 1.5 h resulting in the forma-
tion of a precipitate. The solid was collected on a Büchner funnel
and dried under high vacuum for 8 h.
(PyIS)2. Light yellow solid. Yield: 85%. 1H NMR (CDCl3, 200 MHz,
25 °C, d from TMS): 7.21 (m, 6H), 7.40 (m, 2H), 7.68 (m, 2H), 7.85 (t,
2H), 8.39 (d, 2H), 8.67 (s, 2H, imine), 8.73 (d, 2H). Selected IR
(t, 1H), 7.30 (d, 1H). Selected IR bands: (cmꢂ1) 1583 (m,
1458 (s), 1310 (m), 702 (s).
mN@C),
Py(Bt). Light yellow solid. Yield: 82%. 1H NMR (CDCl3, 200 MHz,
25 oC, d from TMS): 5.07 (s, 1H, NH), 6.41 (s, 1H), 6.82 (m, 2H), 6.80
(t, 1H), 7.03 (m, 2H), 7.23 (m, 1H), 7.59 (d, 1H), 7.71 (t, 1H), 8.56 (d,
1H). Selected IR bands: (cmꢂ1) 1578 (m), 1468 (s), 1435 (s), 1073
(m), 746(s).
bands: (cmꢂ1) 1611 (s,
1298 (m), 743(s, SS).
mN@C), 1581 (m), 1469 (m), 1443 (m),
m
(ThIS)2. Slow evaporation of an ethanolic solution of (ThIS)2 re-
sulted in the formation of yellow microcrystalline (ThIS)2. Yield:
40%. 1H NMR (CDCl3, 200 MHz, 25 °C, d from TMS): 7.15 (m, 8H),
7.51 (t, 4H), 7.66 (d, 2H), 8.57 (s, 2H, imine-H). Selected IR bands:
Fu(Bt). Beige solid. Yield: 40%. 1H NMR (CDCl3, 200 MHz, 25 oC, d
from TMS): 4.43 (s, 1H, NH), 6.35 (m, 3H), 6.7 2 (d, 1H), 6.80 (t, 1H),
(cmꢂ1) 1604 (s,
mN@C), 1563 (m), 1421 (s), 1036 (m), 722 (s, mSS).