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Dalton Transactions
Page 2 of 8
DOI: 10.1039/C8DT01292J
ARTICLE
Journal Name
as macrocycles,19 cages,20 helicates,21 metal-organic
frameworks22 and coordination compounds.23 The intriguing
achievements can be observed in the fields of luminescent and
magnetic properties too.22b, 22c, 23b, 23c However, there are few
anion-induced 3d-4f clusters used as catalysts for the CO2
conversion reactions.
General procedure for synthesis of complex 1a-1e. The ligand HL
(0.2 mmol) and Et3N (27 μL) were added to a solution of CH3CN
(6 mL), and the mixture was stirred until the ligand totally
dissolved. Then Zn(NO3)2·6H2O (0.1 mmol) and Ln(NO3)3·6H2O
(0.1 mmol) (Ln = Eu3+, Tb3+, Nd3+, Er3+, Yb3+) were added,
Ⅲ
followed by CH3OH 1.5 mL. The resulting solution was stirred
for half an hour and then filtered. The filtrate was kept in the
open air for slow evaporation. A crystalline compound was
The ligands derived from o-vanillin have been widely used
as promising building blocks to construct 3d-4f clusters with
rich structural diversity as well as intriguing chemical and
physical properties.24 Herein, we utilized a cost-effective o-
vanillin derivative named methyl-3-methoxysalicylate (HL) as
the ligand and with different anions of the transition and rare
obtained within
3 days. Further, the products were
characterized by IR and TGA.
General procedure for synthesis of complex 2a-2b. 27 μL
triethylamine was added to a 6 mL acetonitrile solution of 0.2
mmol HL and that mixture was stirred until the ligand was
totally dissolved. Then Zn(AcO)2·2H2O (0.1 mmol) and
earth salts to construct two series of 3d-4f clusters: Ln2Zn2(μ3-
OH)2L4(NO3)4 where Ln = Eu3+
Ⅲ
(
1a), Tb3+
(
1b), Er3+
(
1c), Yb3+
Ⅲ
(
(
1d), Nd3+
2a), Nd3+
(
1e) and Ln2Zn4(μ3-OH)2L4(OAc)6(NO3)2, Ln = Tb3+
Ⅲ
Ln(AcO)3·6H2O (0.1 mmol) (Ln = Tb3+, Nd3+) were added,
(2b). They show high catalytic activities on the
followed by methanol 1.5 mL. The resulting solution was
stirred for half an hour and then filtered. The filtrate was kept
in the open air for slow evaporation and a crystalline
cycloaddition of CO2 and epoxides reaction with TON values as
high as 9000 and the TOF values 660 h-1 under atmospheric
pressure and 80 oC. In addition, they also show excellent
luminescence properties with relatively high luminescence compound was obtained within 3 days. Further, the products
quantum yields and long luminescence lifetimes in visible and
near infrared regions, respectively.
were characterized by IR and TGA.
Catalytic studies
General procedure for the cycloaddition of CO2 and epoxides
under 1 bar CO2. In a representative reaction, the complex
(0.001 mmol), TBAB (0.08 mmol) and an epoxide (10 mmol)
were added to a 25 mL round-bottomed flask equipped with a
magneton. Then the flask was de-gassed and set in an oil bath
Experimental
Materials and methods
Chemicals were purchased from commercial sources and used
without further purification.
o
under 1 bar CO2, at 80 C for 14 h. After the reaction, a small
1
liquot of the reaction mixture was analyzed by H NMR to
The infrared spectra were recorded on a Burker VERTEX 70
FT-IR spectrometer using KBr pellets in the 400-4000cm-1
region. Thermogravimetric analysis experiments were
performed using a TGA/NETZSCH STA449C instrument heated
from 30~800 °C (heating rate of 10 °C/min) under the
protection of nitrogen. The solid steady-state luminescence
spectra were recorded on an Edinburgh Instrument FLS920
fluorescence spectrometer which equipped with a 450 W arc
lamp as the excitation source, and the lifetimes were
measured with a 100 WµF 920H lamp as the excitation source.
The quantum yields of the complexes were determined on
Edinburgh Instrument FLS920 using an absolute method with
BaSO4 coating as reference.
determine the conversion and selectivity. Ambient
experiments were conducted for 48 h at reaction conditions as
similar as the above approach.
General procedure for the cycloaddition of CO2 and epoxides
under 10 bar CO2. The Reactions were carried out in a 50 mL
autoclave reactor with a magneton inside. In a representative
reaction, the catalyst (0.001 mmol), TBAB (0.08 mmol) and an
epoxide (10 mmol) were added into the reactor. After three
times of inflation and deflation, the reactor was pressurized to
10 bar with CO2. Then the vessel was set in an oil bath and
stirring at 80 oC for 8 h. After the reaction, a small liquot of the
1
reaction mixture was analyzed by H NMR to determine the
Crystal data were collected on a Bruker FRAMBO
diffractometer (Mo Kα radiation, λ = 0.71073 Å) at 293 K. Data
reduction was accomplished by the Bruker SAINT program.
Multi-scan absorption corrections were applied by using the
program SADABS. Structures were solved by direct methods
and refined by a full matrix least-squares technique based on
F2 using the Olex2 program. All of the non-hydrogen atoms
were refined anisotropically. The organic hydrogen atoms
were generated geometrically. For details, see cif data in
Supporting Information. X-ray crystallographic data for all
complexes see cif files (CCDC number: 1a 1575742, 1b
1575745, 1c 1577169, 1d 1575741, 1e 1575743, 2a 1575744
and 2b 1575746).
conversion and selectivity.
Catalyst recycling tests. After the reaction, a small liquot of the
1
reaction mixture was taken and analyzed by H NMR, then it
was precipitated with ether to get the catalyst. The catalysts
1b and 2a can be recovered after centrifugal separation and
desiccation. The next catalytic recycling experiment was
started with the same amount of styrene oxide and the
recovered catalyst as described above.
Results and discussion
Structure features
Synthetic procedures
2 | J. Name., 2012, 00, 1-3
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