X.-Q. Song et al. / Inorganica Chimica Acta 402 (2013) 156–164
157
Scheme 1. The synthetic route of the ligand L.
purification. The lanthanide nitrates [19] were prepared according
to the literature method.
silica, gradient elution from petroleum to 1:1 petroleum–ethyl ace-
tate to give a white solid. 2.55 g, Yield 76.2%. m.p. 121–122 °C.
Anal., Calc. for C53H48N4O8S4: C, 63.83; H, 4.85; N, 5.62; S, 12.86;
The metal ions analyses were determined by EDTA titration
using xylenol orange as indicator. Carbon, nitrogen, sulfur and
hydrogen analyses were performed using an EL elemental analyzer.
Conductivity measurements were carried out with a DDS-307-type
conductivity bridge using 1.0 ꢁ 10ꢂ3 mol dmꢂ3 solutions in
methanol at 25 °C. Powder X-ray diffraction patterns (PXRD) were
determined with Rigaku-D/Max-II X-ray diffractometer with
Found: C, 63.67; H, 4.74; N, 5.76%. IR (KBr,
m
, cmꢂ1): 3375 (s),
2912 (m), 2886 (w), 1650 (s, C@O), 1597 (m), 1532 (s), 1481 (m),
1293 (s), 1226 (s, Ar–O), 752 (s). 1H NMR (CDCl3, 400 MHz): d:
3.892 (s, 8H, OCH2), 4.688 (d, 8H, NHCH2, J = 5.2 Hz), 6.697 (m,
12H, ArH), 6.913 (m, 4H, ArH), 7.069 (t, 4H, NH), 7.156 (t, 4H,
ArH), 7.530 (m, 4H, ArH), 8.009 (t, 4H, ArH).
graphite-monochromatized Cu Ka radiation. Melting points were
determined on Kofler apparatus. Infrared spectra (4000–
a
2.3. Synthesis of the complexes
400 cmꢂ1) were obtained with KBr discs on a Therrno Mattson FTIR
spectrometer. 1H NMR spectra were recorded in CDCl3 solution at
room temperature on a Bruker 400 instrument operating at a fre-
quency of 400 MHz and referenced to tetramethylsilane
(0.00 ppm) as an internal standard. Chemical shift multiplicities
are reported as s = singlet, d = doublet, t = triplet and m = multiplet.
The emission spectra of the sample was collected by two lenses in
a monochromator (WDG30), detected by a photomultiplier and
processed by a Boxcar Average (EGG model 162) in line with a
microcomputer. Quantum yields were determined by an absolute
method [20] using an integrating sphere on FLS920 of Edinburgh
Instrument. The luminescence decays were recorded using a
pumped dye laser (Lambda Physics model FL2002) as the excita-
tion source. The nominal pulse width and the line width of the
dye-laser output were 10 ns and 0.18 cmꢂ1, respectively. Reported
quantum yields and luminescence lifetimes are averages of at least
three independent determinations. The estimated errors for quan-
tum yields and luminescence lifetimes are 10%. The 77 K solution-
state phosphorescence spectra of the Gd(III) complex was recorded
with solution samples (a 1:1 Ethyl acetate–MeOH (v/v) mixture)
loaded in a quartz tube inside a quartz-walled optical Dewar flask
filled with liquid nitrogen in the phosphorescence mode [21].
One millimole of ligand and 1 equiv (1 mmol) of the lanthanide
nitrates were dissolved in a hot methanol + ethyl acetate (v/
v = 1:10) solution to make a concentrated solution. Then the flask
was cooled, and the mixture was filtered into a sealed 10–20 mL
glass vial for crystallization at room temperature. After about three
weeks crystals suitable for analysis were obtained. IR, molar con-
ductance and elemental analysis data for all complexes are sum-
marized in Tables 1 and 2 respectively.
2.4. X-ray single-crystal diffraction analysis
The single crystal was carefully selected under a microscope
and glued at the tip of a thin glass fiber with cyanoacrylate adhe-
sive. Diffraction data were collected at 296 K on a computer con-
trolled Bruker SMART Apex CCD area detector diffractometer
which equipped with graphite-monochromated Mo Ka radiation
(k = 0.71073 Å) operating at 50 kV and 30 mA. The crystal struc-
tures were solved by direct methods and refined with full-matrix
least squares on F2 using the SHELXT-97 program package [24].
All the non-hydrogen atoms were located from the difference maps
and refined with anisotropic thermal parameters. The H atoms of
the organic ligand were placed theoretically, while the H atoms
of water were located from the difference maps. All the hydrogen
atoms were isotropically refined using the riding model. Further
details of the X-ray structural analysis are given in Table 1 and rep-
resentative bond lengths (Å) are presented in Table 2.
2.2. Synthesis of the ligand
The synthetic route for the ligand (L) is shown in Scheme 1. 2-
Thenylsalicylamide was prepared according to the literature proce-
dure with minor modifications [22] and pentaerythritol benzene-
sulfonate [23] were prepared according to the literature.
3. Results and discussion
To
a solution of pentaerythritol benzenesulfonate (2.32 g,
3.3 mmol) in anhydrous N,N-dimethylformamide (DMF) was
added dried K2CO3 (2.07 g, 15 mmol) and the mixture was stirred
for 30 min at room temperature, 2-thenylsalicylamide 3.50 g
(15 mmol) in 20 ml of anhydrous DMF was added dropwise in
30 min and the resulting solution was stirred and heated to reflux
for 48 h. After cooling down, inorganic salts were separated by fil-
tration and the solvent removed from the filtrate under reduced
pressure. The crude product was purified by chromatography on
3.1. Physical measurements
Analytical data for the newly synthesized lanthanide com-
plexes, listed in Table 3, conforms to a 1:1 metal–to–L stoichiome-
try. All complexes are soluble in DMF, DMSO, ethanol, methanol
and slightly soluble in ethyl acetate. The molar conductance of
the complexes in methanol (Table 3) indicate that all complexes
act as non-electrolytes.
Song, Xue-Qin
