4142 Beynek et al.
Asian J. Chem.
microcrystalline sample using a Sherwood Scientific Magnetic
Susceptibility Balance at room temperature.
reaction mixture was reduced to half its original volume and
then the mixture was placed in a refrigerator to induce precipi-
tation. The yellow powder products were filtered and dried.
Yields 70 and 50 % respectively.
Synthesis
6,6’-Bis(2-nitrophenoxymethyl) 2,2’-bipyridine: The
new precursor dinitro compound was prepared using 6,6’-
bis(bromomethyl)-2,2’-bipyridine and potassium o-nitrophe-
nolate by a modification procedure to that described previously
published methods14. A solution of 2-nitrophenol (1.392 g, 10
mmol) in hot anhydrous DMF (40 mL) was treated with K2CO3
(0.690 g, 5 mmol) and gently boiled. To this solution, 6,6’-
bis(bromomethyl)-2,2’-bipyridine (1,710 g, 5 mmol) in 20 mL
anhydrous DMF was added during 0.5 h. Gently reflux was
maintained for 4 h and a half of the solvent was distilled from
the mixture, which was then poured into H2O (400 mL).Yellow
product was filtered off and washed with dilute aq. NaOH
solution and H2O and then dried. Yield: 2.213 g (96.6 %).
m.p. 182-183 °C. IR (KBr, νmax, cm-1): 3079w, 2905w, 2856w,
1611m, 1584m, 1574m, 1521vs, 1491m, 1443s, 1404w, 1351s
(NO2), 1294s, 1270m, 1257s, 1157m, 1108m, 1087m, 1048m,
993m, 861s (NO2), 819m, 785s, 766m, 744vs, 679m, 632s,
525w, 479w.1H NMR (300 MHz; CDCl3): δ 5.44 (4H, s, CH2),
7.1 (2H, t, J = 7.91 Hz), 7.2 (2H, d, J = 7.3 Hz), 7.53 (2H, d,
J = 7.3 Hz), 7.71 (2H, d, J = 7.3 Hz), 7.88-7.94 (4H, m), 8.34
(2H, d, J = 7.9 Hz).13C NMR (75 MHz; CDCl3):δ 71.82 (CH2),
114.89, 120.51, 121.04, 121.51, 125.97, 134.30, 137.59,
140.35 (C), 152.33 (C), 155.51 (C), 155.70 (C).
[PbL1](ClO4)2 (νmax, cm-1):1632m (C=N), 1586m, 1490m,
-
1441m, 1373w, 1262m, 1213m, 1183w, 1080vs (ClO4 ),
1005m, 911w, 795s, 756m, 743s, 622s (ClO4-), 582w, 524w.1H
NMR (300 MHz; acetone-d6): δ5.80 (4H, s, CH2), 6.93 (2H,
d, J = 7.9 Hz), 7.16 (2H, t, J = 7.1 Hz), 7.28-7.49 (4H, m),
7.68 (2H, t, J = 7.8 Hz), 7.81 (2H, d, J = 7.9 Hz), 7.87 (2H, d,
J = 7.5 Hz), 8.36 (2H, d, J = 7.6 Hz), 8.68 (2H, t, J = 7.9 Hz),
8.93 (2H, d, J = 8.3 Hz), 9.40 (2H, s, HC=N). ΛM (µS/cm),
(acetone, 10-3 M): 160, 25.4 °C. µeff (BM), 24 °C: 0.88 BM.
*
*
UV-visible (DMSO): 305 nm π→π (C=N), 292 nm π→π
(aromatik ring). MALDI-TOF (m/z): Found: 781.788, calc.:
781.828 for [Pb(L1)]+. Found: C, 44.67; H, 3.14; N, 8.53.
Calcd. for C36H26N6O10Cl2Pb: C, 44.09; H, 2.67; N, 8.57.
[PbL2](NO3)2 (νmax, cm-1): 1607m (C=N), 1584m, 1505m,
1488m, 1440m, 1366s (NO3-), 1294vs,1210s, 1117m, 1029m,
991m, 921w, 868s(NO3-), 794s, 754vs, 649m, 589m. ΛM (µS/
cm),(acetone,10-3 M): 178, 24.2°C µeff (BM), 24 °C: 0.99 BM.
*
*
UV-visible (DMSO): 310 nm π→π (C=N), 290, 286 nm π→π
(aromatic ring). MALDI-TOF (m/z): Found: 805,745 calc.:
805.850 for [Pb(L2)]+. Found: C, 49.03; H, 2.80; N, 11.85.
Calcd. for C38H26N8O8Pb: C, 49.08; H, 2.82; N, 12.05.
RESULTS AND DISCUSSION
6,6’-Bis(2-aminophenoxymethyl)-2,2’-bipyridine:
Reduction of the above dinitro derivative,6,6’-bis(2-nitro-
phenoxymethyl)-2,2’-bipyridine, to the diamine compound
was effected by modification of a previously reported method14.
6,6’-Bis(2-nitrophenoxymethyl)-2,2’-bipyridine (1.832 g,
4 mmol) was slurried in EtOH-H2O (1:1, 80 mL) containing
iron powder (2.234 g, 40 mmol) and brought to reflux. Glacial
acetic acid (1.2 mL) was added dropwise and reflux was
maintained for a further 18 h after which the mixture was
filtered hot (using well packed celite aid). The cooled fitrate
was extracted with chloroform and oily product was obtained
by evaporation of organic phase under vacuum. Crystallization
from EtOH:H2O (1:1, 20 mL) gave the pale brown powder
product in 70 % (1.103 g) yield. m.p. 180-182 °C. IR (KBr,
The new diamino compound, 6,6'-bis(2-aminophenoxy-
methyl)-2,2'-bipyridine was obtained starting from 6-amino-
2-methylpyridine, which was converted to 6-bromo-2-methyl-
pyridine by reaction with concentrated aqueous hydrobromic
acid and bromine. Then, 6,6’-dimethyl-2,2’-bipyridine was
prepared using 6-bromo-2-methylpyridine by a modification
of the method described by Iyoda et al.15 and was reacted with
N-bromosuccinimide. Then, the dinitro compound, 6,6’-bis(2-
nitrophenoxymethyl) 2,2’-bipyridine, was prepared using a
Williamson ether synthesis from two equivalents of 2-nitro-
phenol and one equivalent of 6,6'-bis(bromomethyl)-2,2'-
bipyridine in DMF and nitro groups were reduced to amine
using metallic iron14 (Scheme-I). Physical data for all compounds
are given in the experimental section. The complexes were
obtained with 50-70 % yields.
ν
max, cm-1): 3439m (NH2), 3356m δ(NH2),1612m, 1572m,
1505vs, 1442s, 1403w, 1279w,1267m, 1218vs, 1140w, 1108w,
1081vw, 1048m, 991m, 908w, 849w, 782vs, 734vs, 659w,
631s, 548s.1H NMR (300 MHz; CDCl3): δ 3.90 (4H, s (br),
NH2), 5.26 (4H, s, CH2), 6.60-6.83 (8H, m), 7.45 (2H, d, J =
7.7Hz), 7.78 (2H, t, J = 7.8 Hz), 8.30 (2H, d, J = 7.9 Hz).13C
NMR (75 MHz; CDCl3): δ 71.46 (CH2), 112.61, 115.65,
118.69, 120.34, 121.45, 122.0, 124.07, 136.67 (C), 137.96
(C), 154.87(C), 155.76(C). Q-TOF (m/z): Found 399.1833
calc.: (399.1800)for [M+H]+.
NO2
(i),(ii), (iii)
+ 2
N
N
OH
H3C
N
NH2
Br
Br
(iv)
N
N
N
N
O
O
O
O
(v)
Macrocyclic Schiff base complexes: 2,2’-Bipyridine-
6,6’-dicarboxaldehyde or 1,10-phenanthroline-2,9-dicar-
boxaldehyde (1.0 mmol) was dissolved in MeOH (25 mL)
containing Pb(ClO4)2·H2O or Pb(NO3)2 (1.0 mmol). The
solution was stirred vigorously and heated while a methanolic
solution of 6,6’-bis(2-aminophenoxymethyl)-2,2’-bipyridine
(0.40 g, 1.0 mmol) was added slowly. The resultant solution
was refluxed for 4-5 h and filtered hot. The solvent of the
NO2
O2N
NH2
H2N
(i) 47% HBr, Br2, NaNO2 then NaOH (ii) NiCl2(PPh3)2, Zn, Et4NI, THF, under Ar (iii) NBS, CCl4, benzoyl
peroxide (iv) DMF, K2CO3 (v) Fe, CH3COOH.
Scheme-I: Synthetic route for diamine compound, 6,6'-bis(2-amino-
phenoxymethyl)-2,2'-bipyridine
Two new lead(II) complexes of the 23-membered Schiff
base macrocyclic ligands L1 and L2 were prepared using in