Inorganic Chemistry
Article
Figure 1. Preparation scheme of the nonanuclear Tb(III) complexes.
2H: Ar), δ 7.43−7.48 (t, 1H: Ar), δ7.82−7.85 (d, 1H: Ar), δ10.7 (s,
1H: −OH) ppm. Selected IR (KBr, cm−1): 1680(-CO), 2960-
(−CH3). Elemental analysis calculated for C8H8O3: C, 63.15%, H,
5.30%. Found: C, 63.12%, H, 5.35%. ESI-MS: m/z 151.04 [M−H]+.
Other salicylate derivatives, namely, Sal-Et, Sal-Pr, and Sal-Bu, were
obtained using a similar synthesis to that of Sal-Me by changing
alcohols EtOH, PrOH, and BuOH for MeOH, respectively.
In this study, novel alkyl salicylate nonanuclear Tb(III)
complexes with hourglass structure, namely, Tb9(sal-R) and
[Tb9(sal-R)16(μ−OH)10]NO3, where sal-R = alkyl salicylate (R
= −CH3 (Me), −C2H5 (Et), −C3H7 (Pr), or −C4H9 (Bu)), are
reported as shown in Figure 1. The Tb(III) complexes were
prepared by the reaction of terbium nitrate with salicylates in
methanol. The geometrical structures were analyzed using X-
ray single-crystal analysis and shape-measure calculations.26 We
have successfully synthesized the Tb−O lattice using derivatives
of salicylate ligands.27 Optical Faraday rotation of nonanuclear
Tb(III) complexes was observed in the visible region. This is
the first observation of optical Faraday rotation in single
lanthanide complexes. We also successfully estimated enhanced
magnetic exchange interaction using electron paramagnetic
resonance (EPR) measurement at room temperature. Novel
nonanuclear Tb(III) complexes with magneto−optical proper-
ties are remarkable single molecules that directly connect with
photophysical chemistry, coordination chemistry, and material
science.
1
Synthesis of Ethyl Salicylate (Sal-Et). Yield: 66.5%. H NMR
(400 MHz, CDCl3, TMS): δ 1.39−1.42 (t, 3H: −CH3), δ 4.40−4.46
(q, 2H: −CH2), δ 6.92−6.97 (m, 2H: Ar),δ 7.51−7.55 (t, 1H: Ar),δ
7.85−7.88 (d, 1H: Ar), δ 10.8 (s, 1H: −OH) ppm. Selected IR (KBr,
cm−1): 1680(-CO), 2930(−CH2−), 2960(−CH3). Elemental
analysis calculated for C9H10O3: C, 65.05%, H, 6.07%. Found: C,
65.14%, H, 6.18%. ESI-MS: m/z 165.06 [M−H]+.
1
Synthesis of Propyl Salicylate (Sal-Pr). Yield: 60.1%. H NMR
(400 MHz, CDCl3, TMS): δ 1.02−1.06 (t, 3H: −CH3), δ 1.77−1.86
(m, 2H: −CH2), δ 4.29−4.33 (t, 2H: −CH2), δ 6.86−6.99 (m, 2H:
Ar),δ 7.43−7.47 (t, 1H: Ar), δ 7.84−7.87 (d, 1H: Ar), δ 10.8 (s, 1H:
−OH) ppm. Selected IR (KBr, cm−1): 1680(-CO), 2930(−CH2−),
2960(−CH3). Elemental analysis calculated for C10H12O3: C, 66.65%,
H, 6.71%. Found: C, 66.47%, H, 6.76%. ESI-MS: m/z 179.07 [M−
H]+.
1
Synthesis of Butyl Salicylate (Sal-Bt). Yield: 53.4%. H NMR
EXPERIMENTAL SECTION
■
(400 MHz, CDCl3, TMS): δ 0.97−1.01 (t,3H: −CH3), δ 1.44−1.53
(m, 2H: −CH2), δ 1.74−1.80 (m, 2H: −CH2), δ 4.34−4.37 (t, 2H:
−CH2), δ 6.86−6.99 (m, 2H: Ar), δ 7.43−7.47 (t, 1H: Ar), δ 7.83−
7.86 (d, 1H: Ar), δ 10.8 (s, 1H: −OH) ppm. Selected IR (KBr, cm−1):
1680(-CO), 2930(−CH2−), 2960(−CH3). Elemental analysis
calculated for C11H14O3: C, 68.02%, H, 7.27%. Found: C, 67.99%,
H, 7.33%. ESI-MS: m/z 193.09 [M−H]+.
Synthesis of Tb9(sal-Me). Methyl salicylate (0.41 g, 2.7 mmol)
was dissolved in methanol, and triethylamine (0.44 g, 4.40 mmol) was
added to this solution with stirring at 40 °C. Then, Tb(NO3)3·6H2O
(0.686 g, 1.52 mmol) in methanol was added dropwise to this solution
with further stirring for 20 min. White powder, Tb9(sal-Me), [Tb9(sal-
Me)16(μ-OH)10]+[NO3]−, was obtained. Selected IR (KBr, cm−1):
1382(NO3), 1680 (-CO), 2960 (−CH3). Elemental analysis
calculated for C128H122O61NTb9: C, 37.67%, H, 3.01%, N, 0.34%.
Found: C, 37.97%, H, 3.14%, N, 0.31%. FAB-MS: m/z 4018.8
[Tb9(sal-Me)16(μ-OH)10]+.
Synthesis of Tb9(sal-Et). Ethyl salicylate (0.448 g, 2.7 mmol) was
dissolved in methanol, and triethylamine (0.44 g, 4.40 mmol) was
added to this solution with stirring at 40 °C. Then, Tb(NO3)3·6H2O
(0.686 g, 1.52 mmol) in methanol was added dropwise to this solution
with further stirring for 20 min. White powder, Tb9(sal-Et), [Tb9(sal-
Et)16(μ-OH)10]+[NO3]−), was obtained. Selected IR (KBr, cm−1):
1382(NO3), 1680(-CO), 2930(−CH2−), 2960(−CH3). Elemental
analysis calculated for C148H160O61NTb9: C, 40.17%, H, 3.61%, N,
0.33%. Found: C, 39.91%, H, 3.59%, N, 0.34%. FAB-MS: m/z 4242.2
[Tb9(sal-Et)16(μ-OH)10]+.
Synthesis of Tb9(sal-Pr). Propyl salicylate (0.486 g, 2.7 mmol)
was dissolved in methanol, and triethylamine (0.44 g, 4.39 mmol) was
added to this solution with stirring at 40 °C. Then, Tb(NO3)3·6H2O
(0.686 g, 1.52 mmol) in methanol was added dropwise to this solution
with further stirring for 20 min. White powder, Tb9(sal-Pr), [Tb9(sal-
Materials. Salicylic acid (C6H4(OH)COOH), methanol
(CH3OH), ethanol (C2H5OH), propanol (C3H7OH), and butanol
(C4H9OH) were purchased from Kanto Chemical Co., Inc. Terbium-
(III) nitrate hexhydrate (Tb(NO3)3·6H2O), sulfuric acid (H2SO4), and
triethylamine (C6H15N) were also purchased from Kanto Chemical
Co., Inc. All other chemicals and solvents were reagent grade and were
used without further purification.
1
Apparatus. H NMR data were measured using an Auto-NMR
1
JEOL ECS 400 MHz Spectrometer. H NMR chemical shifts were
determined using tetramethylsilane (TMS) as an internal standard.
Electrospray ionization mass spectrometry (ESI-MS) measurements
were made using Thermo Scientific Exactive. Fast atom bombardment
mass spectrometry (FAB-MS) spectra were measured on JEOL JMS-
700TZ. Elemental analyses were performed by MICRO CORDER
JM10. Infrared spectra were recorded on a JASCO FT/IR-350
spectrometer. X-ray diffraction (XRD) spectra were characterized by a
RIGAKU X-ray diffractometer RINT 2200. Single-crystal X-ray
diffractions were made on a RIGAKU RAXIS RAPID imaging plate
area detector. Quantitative elemental analysis was performed with
inductively coupled plasma−atomic emission spectroscopy (ICP-
AES). EPR spectra of nuclei Gd(III) complexes were measured
using a JEOL JES-TE200 X-band ESR spectrometer.
Synthesis of Methyl Salicylate (Sal-Me). A solution of salicylic
acid (3.0 g, 21.7 mmol) in 30 mL of methyl alcohol was added to
sulfuric acid (1.0 mL), and after it was stirred and reacted for 5 h,
distilled water (20 mL) was added to the reaction mixture. The pH
value of this solution was adjusted to pH 7 by adding sodium
carbonate. The mixture was extracted with ether (2 × 30 mL). The
organic layer was separated and dried with magnesium sulfate, and the
solvent was evaporated. The residue was chromatographed on silica gel
1
eluting with ethyl acetate/hexane (35/65). Yield: 62.1%. H NMR
(400 MHz, CDCl3, TMS): δ 3.95 (s, 3H: −CH3), δ 6.86−6.99 (m,
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dx.doi.org/10.1021/ic5009363 | Inorg. Chem. XXXX, XXX, XXX−XXX