A. P. I. Bhat and B. R. Bhat
Synthesis
calculated for C20H13CuNNaO6S6 [M+]: 642.2; found: 643.4; UV–visible
λ
max (nm): 275, 345, 420, 482, 562. μeff: 1.65.
Synthesis of ligand L1
General Procedure for Homocoupling Reaction
The ligand was synthesized by a similar method to that described
in the literature.[15,16] A 1:1 equimolar ethanolic solution of 2-
aminonaphthalene sulfonic acid (1 mmol) and 2,4-dihydroxy-
benzaldehyde (1 mmol) were mixed and heated for 2 h with
constant stirring. The characteristic yellow precipitate obtained
was filtered, washed, recrystallized from ethanol and dried in
vacuo. The purity of the prepared ligand was checked by thin-
layer chromatography and elemental analysis.
In this procedure, magnesium turnings (13 mmol, 0.320 g atom) were
placed in a two-necked round-bottom flask with a calcium chloride
guard tube and a crystal of iodine was added. Aryl halide (2 mmol
of 10 mmol in total) in 5 ml anhydrous diethyl ether was added with
constant stirring at room temperature. Initially, an increase in the tem-
perature of the reaction mixture was observed and the appearance of
turbidity after few minutes indicated the initiation of the reaction. The
remaining aryl halide (8 mmol) in 5 ml ether was added dropwise and
the reaction mixture was stirred for 40 min. The catalyst (0.13 mol%)
was added to the reaction mixture. Stirring was continued and after
5 h the reaction mixture was cooled and hydrolyzed with a saturated
solution of 10% aqueous ammonium chloride. The product was
extracted with ether; the combined organic layers were dried over an-
hydrous magnesium sulfate. The product obtained compared well
with the authentic samples using gas chromatography.
Synthesis of complexes (C1, C2, C3)
The complexes C1, C2 and C3 were synthesized strictly under an-
hydrous conditions (Fig. 1). To a methanolic (20 ml) solution
containing CS2 (0.2 ml, 3 mmol) and sodium metal, L1 (1 mmol)
and metal acetate [M(CH3COO)2] (M = Co, Ni and Cu) (1 mmol)
was added with constant stirring. The mixture was refluxed for
4 h. The colored complexes obtained were filtered, washed with
methanol followed by petroleum ether (60–80°C) and dried in
vacuo. Compounds were soluble in DMSO and DMF.
Results and Discussion
C1:, Yield 0.400 g, 61%; m.p. 320–323°C. Elemental analysis calcu-
lated for C20H15CoNNaO7S6 (%): C, 36.64; H, 2.31; N, 2.14; S, 29.34;
found: C, 36.56; H, 2.28; N, 2.13; S, 29.25; FT-IR (KBr, cmꢀ1): 3381
ν(OH), 1605 ν(CH¼N), 1220 ν(C―O), 1454, 1247 ν(C¼C), 1056,
1018 ν(C¼S), 994 ν(C―S), 617 ν(SC¼CS), 847 δr(H2O), 526 δw(H2O);
MS (ESI) (m/z) calculated for C20H15CoNNaO7S6 [M+]: 655.6; found:
656.3; UV–visible λmax (nm) 280, 353, 419, 456; μeff 4.26.
C2:, Yield 0.439 g, 67%; m.p. >350°C. Elemental analysis calculated
for C20H15NNaNiO7S6 (%): C, 36.65; H, 2.31; N, 2.14; S, 29.35. found:
C, 36.54; H, 2.28; N, 2.13; S, 29.23; FT-IR (KBr, cmꢀ1): 3299 ν(OH),
1609 ν(CH¼N), 1220 ν(C―O), 1427 ν(C¼C), 1047 ν(C¼S), 982, 931
ν(C―S), 615 ν(SC¼CS), 856 δr(H2O), 541 δw(H2O); MS (ESI) (m/z) cal-
culated for C20H15NNaNiO7S6 [M+]: 655.4; found: 656.7; UV–visible
Synthesis
Elemental analyses (C, H, N, S) were in good agreement with the
molecular formula proposed for L1 and complexes C1–C3. The
electronic absorption spectra of ligand and complexes were
made in DMSO. The spectra of the ligand displayed three main
bands. The bands in the region of 280 nm were assigned to the
π–π* transitions of the aromatic rings. The band at 312–359 nm
involved n–π* transition of the S¼O and C¼N groups. The band
in the region 404 nm can be attributed to a charge transfer tran-
sition within the ligand (CT). In the spectra of all the complexes,
the bands in the region 280–357 nm were assigned to intra-li-
gand charge transfer transition (ILCT). The spectra of C1 showed
ligand-to-metal charge transfer transition (LMCT) in the region
419–456 nm and the spectra of C2 showed d–d transition in the
range 481–515 nm, which suggests an octahedral geometry for
the complexes. The magnetic moment values for C1 and C2 were
4.26 and 3.58 BM, respectively, supporting octahedral geome-
try.[17,18] The spectrum of C3 showed d–d transition in the range
λmax (nm): 286, 357, 422, 481, 515; μeff: 3.58.
C3:, Yield 0.405 g, 63%; m.p. >350°C. Elemental analysis calculated
for C20H13CuNNaO6S6 (%): C, 37.40; H, 2.04; N, 2.18; S, 29.96; found:
C,37.37; H, 2.02; N, 2.17; S, 29.84; FT-IR (KBr, cmꢀ1): 3313 ν(OH), 1606
ν(CH¼N), 1200 ν(C―O), 1428 ν(C¼C), 1051 ν(C¼S), 1002, 954
ν(C―S), 615 ν(SC¼CS), 859 δr(H2O), 550 δw(H2O); MS (ESI) (m/z)
Figure 1. Synthesis of complexes C1, C2 and C3.
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Appl. Organometal. Chem. 2014, 28, 383–388