Structure and luminescent property of a Sm3+ complex containing benzoyltrifluoroacetone and 1,2-bis[(anthracen-9-ylmethyl)amino]ethane ligands

Download

Physical sciences Chemistry

DOI: 10.31276/VJSTE.63(2).20-24

Structure and luminescent property of a Sm³⁺complex

containing benzoyltriﬂuoroacetone

and 1,2-bis[(anthracen-9-ylmethyl)amino]ethane ligands

Thi Hien Dinh^1*, Minh Hai Nguyen²

¹Faculty of Chemistry, Hanoi National University of Education

²Faculty of Chemistry, University of Science, Vietnam National University, Hanoi

Received 1 April 2021; accepted 31 May 2021

Abstract:

The synthesis, structure, and luminescent properties of a samarium(III) complex (A2) containing

benzoyltriﬂuoroacetone (HTFPB) and 1,2-bis[(anthracen-9-ylmethyl)amino]ethane (BAAE2) ligands are herein

reported. The structure ofA2 has been elucidated by infrared spectroscopy and single crystal X-ray diﬀraction. X-ray

crystallographic analysis demonstrated that A2 has a mononuclear structure with a formula of Sm(TFPB)₃(BAAE2)

in which Sm³⁺ion is coordinated to six O-atoms from three TFPB ligands and two N-atoms from one ancillary

ligand (BAAE2). UV-Vis data show that A2 strongly absorbs in the region of 220-400 nm. Nonetheless, A2 gives poor

emission due to a quenching eﬀect of the anthracenyl moiety.

Keywords: anthracene, β-diketone, rare earth complex.

Classiﬁcation number: 2.2

that bispyridine, phenanthroline, and many pyridine-based

Introduction

ligands are able to turn on the emission of the central metal

β-diketonate complexes are among the most thoroughly

explored rare earth coordination compounds. This is

ion due to additional sensitizer eﬀects [7, 8]. In this study,

1,2-bis[(anthracen-9-ylmethyl)amino]ethane (BAAE2), a

ligand with a low-lying triplet state, has been utilized to

construct a tris β-diketonate complex [9-12]. BAAE2 is a

potentially good bidentate ligand as the trivalent rare-earth

ions are Lewis acids that preferentially form complexes

with nitrogen donor bases. In the following discussions, the

main attention will be focused on the syntheses, structures,

and luminescent properties of Sm³⁺complexes containing

TFPB and BAAE2 ligands.

mainly due to the fact that they are easily synthesized,

readily available from commercial sources, and are

utilized in many applications ranging from magnetism to

photoluminescence [1, 2]. The narrow and strong emission

of rare earth ions with β-diketonates makes them applicable

in optical and electroluminescent devices as well as in

luminescence sensors for cations and anions. However,

due to “Laporte-forbidden” f-f transitions, emissions from

the direct excitation of lanthanide ions are infeasible

[3]. Benzoyltriﬂuoroacetone (HTFPB) is a commercially

available and eﬃcient sensitizer that is able to transfer

excited energy to rare earth ions. Due to the suitable

triplet energy level of TFPB, a so-called “antenna eﬀect’’

is produced that turns on lanthanide emissions. Typically,

the synthesis of lanthanide β-diketonates in the ﬁrst step

involves two water molecules in the coordination sphere

of the central metal ion. Subsequent displacement of the

coordinatedwaterbyancillarychelatingligandswithvarious

electronic structures may lead to a ﬁne tuning of lanthanide-

centered emissions [4-6]. It has been well documented

Experimental

Synthesis of ligands and complexes

Synthesis of BAAE2 ligand:

Step 1: Synthesis of BAAE1[13]

BAAE1 was synthesized via a condensation reaction

between ethylenediamine and anthracene-9-carcbadehyde,

which is depicted in Scheme 1.

^*Corresponding author: Email: dth0104@gmail.com

Vietnam Journal of Science,

June 2021 • Volume 63 number 2

Technology and Engineering

Physical sciences Chemistry

Synthesis of Sm(TFPB)₃BAAE2 complex (A2)

A2 was achieved by reacting A1 with BAAE2 ligand in

chloroform-methanol solvent mixture (Scheme 3).

Scheme 1.

A solution of anthracene-9-caboxaldehyde (0.400 g;

H₂C

F₃C

OH₂

CH₂

1.94 mmol) in 12 ml DMF/CH₃OH (v/v, 1:5) was added

to ethylenediamine (0.067ml, 0.97 mmol) in methanol and

the mixture was reﬂuxed for 4 h with constant stirring.

After the solution had cooled to room temperature, a yellow

precipitate was formed and collected by vacuum ﬁltration.

The product was washed by a few drops of DMF, a large

amount of methanol, and air-dried. The yield was 0.364 g

(86%).

BAAE2

H₂C

Scheme 3.

A solution of BAAE2 (0.397 g, 1 mmol) in CHCl₃(15

ml) was added dropwise under stirring to a solution of A1

(0.831 g, 1 mmol) in MeOH (15 ml). The mixture was

stirred at room temperature for about 1 h until a yellowish

precipitate formed. The solvent was removed in vacuum and

the resulting solid was then washed with n-hexane. After

drying under vacuum, a pale-yellow powder was obtained.

The product was crystallized in EtOH/CH₂Cl₂(v/v, 1:1) and

the yield was 74%.

Step 2: Synthesis of BAAE2 ligand [13]

The synthetic procedure of ligand BAAE2 was based on

a reaction reducing ligand BAAE1 by NaBH₄in methanol

as described in Scheme 2.

Measurements

The IR spectra of A2 was measured with a FT-IR 8700

infrared spectrophotometer (4000-400 cm^-1) in KBr pellets

at Institute of Chemistry, Vietnam Academy of Science and

Technology.

Scheme 2.

BAAE1 (0.396 g, 0.907 mmol) was dissolved in a

mixture of CH₂Cl₂(30 ml) and CH₃OH (15 ml) to obtain a

yellow solution. A solution of NaBH₄(0.527 g, 13.9 mmol)

in methanol (3 ml) was added under stirring to the mixture.

The solution was stirred overnight at room temperature to

give a yellow solid. The product was washed several times

with distilled water, ﬁnally with diethyl ether, and air-dried.

The yield was 0.320 g (80%).

Single crystal X-ray diﬀraction data of the complex A2

was collected on the X-ray diﬀractometer (Bruker D8 Quest)

at 298 K at the Faculty of Chemistry, University of Science,

Vietnam National University, Hanoi. Structure solution and

reﬁnement were performed with OLEX2 programs.

Absorption spectra of the ligands and the complexes

were measured in dichloromethane at room temperature on

Cary 5000 UV/Vis spectrometer at Faculty of Environmental

Chemistry, Hanoi National University of Education.

Emission spectra of the complexes were measured on

Hitachi Fluorescence Spectrophotometer F-7000.

Synthesis of the complexes:

Synthesis of Sm(TFPB)₃(H₂O)₂complex (A1)

Sm₂O₃(0.070 g, 0.2 mmol) was dissolved in HCl at

50^oC, then distilled water was added and heated at 100^oC to

form SmCl₃. A solution of NaOH (0.048 g, 1.2 mmol) and

HTFPB (0.259 g, 1.2 mmol) in MeOH (15 ml) was added

dropwise under stirring to a solution of SmCl₃in MeOH

(15 ml). The mixture was stirred at room temperature until

a white solid completely formed. The product was washed

by a large amount of CCl₄and air-dried. The yield was 88%.

Results and discussion

Infrared spectroscopy

TheinfraredspectrumofthecomplexSm(TFPB)₃BAAE2

(A2) is shown in Fig. 1. Typical absorption bands of the

complexes and ligand are shown in Table 1.

Vietnam Journal of Science,

June 2021 • Volume 63 number 2

Technology and Engineering

Physical sciences Chemistry

Fig. 1. The infrared spectrum of A2.

Table1. Typicalabsorptionbandsofthecomplexesandligand(cm^-1).

Compounds

ν_O-H

3450 3030

3040

3300 3035

3054

ν_C-Caromaν_C-F

ν_C=O

ν_C-N

ν_Sm-O

HTFPB

BAAE2

1191

1600

1100

1170

1295

1608

1609

557

562

991

The IR spectrum of A1 exhibits the typical broad

absorption in the region 3000-3500 cm^-1, which proposes

the presence of water molecules coordinated to the central

ion Sm³⁺. In contrast, the absence of the broad bands in

the region of 3000-3500 cm^-1for A2 suggests that water

molecules in A1 have been displaced by the nitrogen

donor of BAAE2 ligand. The respective ν_C-Fvibration of

A2 is found at 1295 cm^-1that, compared to the starting

material, is shifted to a somewhat higher frequency. The

absorption at 1600 cm^-1, which is typical for C=O sketch

in the HTFPB ligand, is red-shifted to 1609 cm^-1in A2

[2]. In addition, the absorption band responsible for ν_Sm-N

at 506 cm^-1in A2 conﬁrms the complexation of Sm³⁺ions

with BAAE2 ligands through nitrogen atoms. The change

in absorption frequency of ν_C=Ocompared with free ligands

and the emergence of ν_Sm-Nabsorption in the low frequency

prove that HTFPB and BAAE2 ligands are present in the

coordination sphere of Sm³⁺.

Fig. 2. Molecular structure of A2.

The structure of the complex reveals a coordination

number of eight in the central metal ion in which Sm³⁺

is bonded to six oxygen atoms from three TFPB and two

nitrogen atoms from the BAAE2 ligand. The bond lengths

of Sm1-O are 2.355-2.418 Å. The bond lengths of Sm³⁺

with two nitrogen atoms of BAAE2 are 2.599-2.658 Å.

The O-Sm1-O bond angles are nearly the same and in the

range of 69.58-70.7^o, which is longer than that of N-Sm1-N

(67.26^o). The C-N bond lengths (1.465-1.491 Å) in the

complex were found to be longer than a C-N single bond

(1.472 Å). This conﬁrms the delocalization of π electrons

in the chelate ring upon complexation of BAAE2. The C-C

bond length in the diketonate of C2 is 1.359-1.430 Å, which

is shorter than the C-C bond length (1.54 Å) but longer than

that of C=C (1.34 Å). Similarly, the C-O bond length in the

diketone of A2 is 1.247-1.268 Å and it is also shorter than

the bond length of C-O but longer than that of C=O. This

Single crystal X-ray diﬀraction

The structure of A2 was determined by single crystal conﬁrms the delocalization of π electrons in the β-diketonate

X-ray diﬀraction (Fig. 2). Selected bond lengths and angles upon complexation between Sm³⁺and TFPB ligands. The

are provided in Table 2. Crystal data and data collection coordination of Sm³⁺with BAAE2 ligands through two

parameters for the complex are given in Table 3.

nitrogen atoms forms a ﬁve-membered chelate ring.

Vietnam Journal of Science,

June 2021 • Volume 63 number 2

Technology and Engineering

Physical sciences Chemistry

Table 2. Selected bond lengths and angles for A2.

UV-Vis absorption spectroscopy

To determine the photophysical properties of the

compounds, we measured absorption spectra of ligands and

Sm³⁺complexes in the region of 200-800 nm in a CH₂Cl₂

solvent. The absorption spectra of A1, A2, HTFPB, and

BAAE2 are displayed in Fig. 3.

Bond lengths/Å

Sm1-O1

2.418(5)

2.355(5)

2.370(5)

2.368(5)

2.374(5)

2.357(5)

2.599(6)

2.658(6)

1.259(9)

1.273(9)

1.258(9)

1.247(7)

1.268(7)

O6-C14

N1-C1

1.249(8)

1.491(9)

1.465(9)

1.486(7)

1.478(8)

1.480(8)

1.351(12)

1.394(12)

1.373(12)

1.418(11)

1.365(10)

1.496(10)

1.412(10)

Sm1-O2

Sm1-O3

N1-C2

Sm1-O4

N2-C3

Sm1-O5

N2-C4

Sm1-O6

N2-C5

Sm1-N1

C2-C3

Sm1-N2

C6-C7

O1-C6

C7-C8

O2-C8

C9-C10

C10-C11

C12-C13

C13-C14

O3-C9

O4-C11

O5-C12

Bond angles/^o

O1-Sm1-O2

O3-Sm1-O4

O5-Sm1-O6

N1-Sm1-N2

C1-N1-C2

N1-C2-C3

C2-C3-N2

C3-N2-C4

C4-N2-C5

C5-N2-C3

69.58(18)

70.7(2)

Fig. 3. Absorption spectra of A1, A2, HTFPB, and BAAE2 in

CH₂Cl₂at room temperature.

70.34(17)

67.26(17)

112.6(5)

110.4(5)

111.9(5)

109.4(5)

107.5(5)

108.9(5)

The spectra highlight strong absorptions in the region

of 220-400 nm for the HTFPB and BAAE2 ligands as well

as the A1 and A2 complexes. The broad bands observed

at 327 and 328 nm are assigned to singlet-singlet π-π*

transition in β-diketonate moiety [14]. These absorption

bands are shifted slightly to the longer wavelength region

compared with that of free HTFPB (325 nm), which hints at

the perturbation of Sm³⁺upon complexation [7]. The bands

at a lower wavelength around 260 nm are anthracene-based

π-π* electronic transitions. The auxiliary ligand BAAE2 is

also absorbed at ultraviolet wavelengths. The lanthanide f-f

transitions are not allowed, which makes absorption due to

Sm³⁺ions imperceptible in the spectra of A1 and A2.

Table 3. Crystal data and structure refinement for A2.

Formula

C₅₀H₅₀N₆O₆F₉Sm

M_w/g.mol^-1

1046.12

Crystal system

monoclinic

a/Å

10.7101(10)

b/Å

23.075(2)

c/Å

23.458(2)

Photoluminescence spectroscopy

α/°

ThephotoluminescencespectraofA1andA2werestudied

using an excitation wavelength of 365 nm. The emission

spectra are shown in the Fig. 4. Despite the quenching eﬀect

of O-H stretches, A1 gives a strong orange color and narrow

band emission. This might be due to the very eﬃcient

sensitization of TFPB to Sm³⁺. Meanwhile, A2 is much less

emissive than A1 but gives the same pattern of emission

bands. We assume that the low-lying triplet energy level

of the anthracenyl core in BAAE2 leads to intramolecular

energy transfer from excited Sm³⁺. The emission lines at 565,

603, 651, and 710nm are assigned to the ⁴G_5/2→6F_J(J=1/2-

9/2) transitions of Sm³⁺. The strongest emission band

β/°

102.355(3)

γ/°

Volume/Å³

Space group

5663.0(9)

P2₁/c

_calcg/cm³

1.227

μ/mm^-1

1.107

Reﬂections collected

Independent reﬂections

33163

10312 [R_int=0.1464, R_sigma=0.1418]

Data/restraints/parameters 10312/741/721

R1/wR2 [I≥2σ (I)]

R₁=0.0641, wR₂=0.1364

0.996

GOF

centered at 651nm stems from the G_5/2→⁶F_7/2transition.

Vietnam Journal of Science,

June 2021 • Volume 63 number 2

Technology and Engineering

Physical sciences Chemistry

copper and sulﬁde ions in living cells”, New J. Chem., 41, pp.5981-

120

100

5987.

[3] M. Hatanaka, S. Yabushita (2009), “Theoretical study on the

f-f transition intensities of lanthanide trihalide systems”, J. Phys.

Chem. A, 113, pp.12615-12625.

[4] Y.-W. Yip, H. Wen, W.-T. Wong, P.A. Tanner, K.-L. Wong

(2012), “Increased antenna eﬀect of the lanthanide complexes by

control of a number of terdentate n-donor pyridine ligands”, Inorg.

Chem., 51, pp.7013-7015.

[5] E.G. Moore, A.P.S. Samuel, K.N. Raymond (2009), “From

antenna to assay: lessons learned in lanthanide luminescence”, Acc.

Chem. Res., 42, pp.542-552.

500

550

600

650

700

750

[6] H.-Q. Yin, X.-Y. Wang, X.-B. Yin (2019), “Rotation restricted

emission and antenna eﬀect in single metal-organic frameworks”, J.

Am. Chem. Soc., 141, pp.15166-15173.

-20

Wavelength (nm)

[7] T.-N. Trieu, T.-H. Dinh, H.-H. Nguyen, U. Abram, M.-H.

Nguyen (2015), “Novel lanthanide(iii) ternary complexes with

naphthoyltriﬂuoroacetone: a synthetic and spectroscopic study”, Z.

Anorg. Allg. Chem., 641, pp.1934-1940.

Fig. 4. PL spectra of A1 (a red line), A2 (a blue line) complexes.

Conclusions

Samarium (III) complexes containing TFPB and

BAAE2 ligands were synthesized. The structure of A2 was

deﬁnitively determined by X-ray diﬀraction and revealed a

ﬁve-membered chelate ring of BAAE2 with Sm³⁺ions. The

results also described that Sm³⁺in A2 adopts a coordination

number of eight as it is bonded to six oxygen atoms from

three TFPB ligands and two nitrogen atoms of BAAE2. UV-

[8] Y. Ni, J. Tao, J. Jin, C. Lu, Z. Xu, F. Xu, J. Chen, Z. Kang

(2014), “An investigation of the eﬀect of ligands on thermal stability

of luminescent samarium complexes”, J. Alloys Compd., 612, pp.349-

354.

[9] J. Sun, B. Song, Z. Ye, J. Yuan (2015), “Mitochondria

targetable time-gated luminescence probe for singlet oxygen based

Vis results conﬁrm the strong absorptions produced by the on a β-diketonate-europium complex”, Inorg. Chem., 54, pp.11660-

11668.

β-diketonate and anthracenyl fragments. The A1 and A2

complexes both display Sm³⁺-centered orange emissions

in which that of A2 is much weaker due to triplet-triplet

energy transfer arising from the anthracenyl ring of BAAE2.

Attempts to disrupt the aromaticity of the anthracenyl ring

in order to switch on Sm³⁺emissions in A2 are presently

being made in our laboratory.

[10] J. Wu, Y. Xing, H. Wang, H. Liu, M. Yang, J. Yuan

(2017), “Design of a β-diketonate-Eu³⁺complex-based time-gated

luminescence probe for visualizing mitochondrial singlet oxygen”,

New J. Chem., 41, pp.15187-15194.

[11] H. Ma, X. Wang, B. Song, L. Wang, Z. Tang, T. Luo, J. Yuan

(2018), “Extending the excitation wavelength from UV to visible light

for a europium complex-based mitochondria targetable luminescent

probe for singlet oxygen”, Dalton Trans., 47, pp.12852-12857.

ACKNOWLEDGEMENTS

This work was completed with ﬁnancial support from

the Ministry of Education and Training of Vietnam, under

the project B2018-SPH-49.

[12] S.N.A. Jenie, S.M. Hickey, Z. Du, D. Sebben, D.A. Brooks,

N.H. Voelcker, S.E. Plush (2017), “A europium-based ‘oﬀ-on’

colourimetric detector of singlet oxygen”, Inorg. Chim. Acta, 462,

pp.236-240.

COMPETING INTERESTS

The authors declare that there is no conﬂict of interest

regarding the publication of this article.

[13] G.-q. Zhang, G.-q. Yang, L.-y. Yang, Q.-q. Chen, J.-S. Ma

(2005), “Synthesis, characterization and photophysical properties of

novel dinuclear silver(I) and mononuclear palladium(II) complexes

with 1,2-bis[(anthracen-9-ylmethyl)amino]ethane”, Eur. J. Inorg.

Chem., 2005, pp.1919-1926.

REFERENCES

[1] B. Song, G. Wang, M. Tan, J. Yuan (2006), “A europium(III)

complex as an eﬃcient singlet oxygen luminescence probe”, J. Am.

Chem. Soc., 128, pp.13442-13450.

[14] K. Lunstroot, P. Nockemann, K. Van Hecke, L. Van Meervelt,

C. Görller-Walrand, K. Binnemans, K. Driesen (2009), “Visible and

near-infrared emission by samarium(III)-containing ionic liquid

mixtures”, Inorg. Chem., 48, pp.3018-3026.

[2] Y. Wang, H. Wang, X. Zhao, Y. Jin, H. Xiong, J. Yuan, J. Wu

(2017), “A β-diketonate-europium(iii) complex-based ﬂuorescent

probe for highly sensitive time-gated luminescence detection of

Vietnam Journal of Science,

June 2021 • Volume 63 number 2

Technology and Engineering

5 trang yennguyen 18/04/2022 860

Download

Bạn đang xem tài liệu "Structure and luminescent property of a Sm3+ complex containing benzoyltrifluoroacetone and 1,2-bis[(anthracen-9-ylmethyl)amino]ethane ligands", để tải tài liệu gốc về máy hãy click vào nút Download ở trên

File đính kèm:

structure_and_luminescent_property_of_a_sm3_complex_containi.pdf