научная статья по теме SYNTHESES, LUMINESCENCE, AND HIRSHFELD SURFACE ANALYSES OF THREE LANTHANIDE COORDINATION POLYMERS DIRECTED BY FLEXIBLE CARBOXYLATE LIGAND Химия

Текст научной статьи на тему «SYNTHESES, LUMINESCENCE, AND HIRSHFELD SURFACE ANALYSES OF THREE LANTHANIDE COORDINATION POLYMERS DIRECTED BY FLEXIBLE CARBOXYLATE LIGAND»

KOOPMHH^HOHHAS XHMH3, 2015, moM 41, № 10, c. 619-626

yM 541.49

SYNTHESES, LUMINESCENCE, AND HIRSHFELD SURFACE ANALYSES OF THREE LANTHANIDE COORDINATION POLYMERS DIRECTED BY FLEXIBLE CARBOXYLATE LIGAND © 2015 L. Lu1, *, J. Wang1, A. Q. Ma2, *, W. P. Wu1, B. Xie1, Y. Wu1, and A. Kumar3, *

1School of Chemistry and Pharmaceutical Engineering, Sichuan University of Science & Engineering, Zigong, 643000 P.R. China 2Guangdong Medical College, School of Pharmacy, Dongguan, 523808 P.R. China 3Department of Chemistry, Faculty of Science, University of Lucknow, Lucknow, 226007India *E-mail: scwangjun2011@126.com; maqandght@126.com; kumar_abhinav@lkouniv.ac.in

Received February 22, 2015

Three new complexes, namely {[Ln(L)3(2,2'-Bipy)]n • 2H2O} (Ln = Pr (I), Sm (II) and Nd (III)) (HL = 3-(4-hydroxyphenyl)propanoic acid), have been synthesized and structurally characterized by single-crystal X-ray diffraction analyses (CIF files CCDC nos. 1045041 (I), 1045042 (II), 1045043 (III)). The structural determination revealed that I—III have similar dinuclear motifs, which can be further linked into 1D chain via the hydrogen bond interactions. Furthermore, the luminescent properties of I—III show the strong emissive power and feature.

DOI: 10.7868/S0132344X15100059

INTRODUCTION

Coordination polymers of lanthanides have found a variety of applications in materials science including superconductors, luminescent probes and catalysts. Recently it has been demonstrated that luminescent lanthanide compounds have the potential as emitters in electroluminescent devices [1—10]. Although the flexibility of the coordination spheres of the f-block metal ions make design difficult, the pliability together with the tendency towards higher coordination numbers makes lanthanide ions attractive for designing different new materials with unusual networks. However, due to the nature of Ln3+ ions with partially filled 4f orbitals, large radii, and high coordination numbers, they always show characteristic luminescent emissions [11—13]. As a result, studies on luminescent lanthanide compounds are expanding rapidly, and a lot of investigations on the lanthanide frameworks have been published recently [14, 15].

As a building block, 3-(4-hydroxyphenyl)propano-ic acid (HL) can be multidentate and is an excellent candidate for construction of lanthanide coordination polymers. With the above in mind, we chose HL as ligand to construct MOFs based on the following considerations: (1) HL, as a derivative of the p-hydroxy-benzoic acid ligand, is a good spacer and has been rarely used in the assembly of coordination polymers; (2) the carboxylic group may have different coordina-tive mode due to the flexible chain, which may induce higher metal cluster [17]. Up to now, construction of new lanthanide coordination polymers based on HL is

not reported, especially involving N-containing ligand. Taking account of the above, we would like to synthesize and explore new complexes with HL and different lanthanide ions. Herein, a series of new Ln coordination polymers based on HL ligand, namely, {[Ln(L)3(2,2'-Bipy)]„ • 2H2O} (Ln = Pr (I), Sm (II) and Nd (III)), were synthesized under mild conditions and characterized by elemental analyses, IR, TGA, fluorescent measurements, and single-crystal X-ray diffraction analyses. Moreover, compounds I—III display strong photoluminescent property and high thermal stability.

EXPERIMENTAL

Materials and physical measurements. All the reagents and solvents for synthesis and analysis were commercially available and used directly. Elemental analyses for carbon, hydrogen and nitrogen were performed on a Vario EL III elemental analyzer. The infrared spectra (4000 ~ 600 cm-1) were recorded by using KBr pellet on an AVATAR-370 IR spectrometer. TGA were carried out with a Metter-Toledo TA 50 in dry dinitrogen (60 mL min-1) at a heating rate of5°C min-1. X-ray power diffraction (XRPD) data were recorded on a Rigaku RU200 difractometer at 60 kV, 300 mA for CuZ"a radiation (X = 1.5406 A), with a scan speed of 2°/min and a step size of 0.02° in 29. Luminescence spectra for crystal solid samples were recorded at room temperature on an Edinburgh FLS920 phos-phorimeter.

Table 1. Crystallographic data and structure refinement details for complexes I—III

Parameter Value

Pr (I) Nd (II) Sm (III)

Formula weight 1655.21 1655.82 1672.09

Crystal system Triclinic Triclinic Triclinic

Space group P1 P1 p1

a, A 11.261(6) 11.2368 (9) 11.2382(6)

b, A 11.925(6) 11.9077(10) 11.8868(9)

c, A 14.769(7) 14.7521(12) 14.7568(8)

a, deg 88.829(7) 88.619(2) 88.619(5)

P, deg 84.053(8) 83.996(2) 83.873(4)

Y, deg 68.011(7) 68.070(2) 68.270(6)

V, A3 1828.7(16) 1828.8(3) 1820.5(2)

Z 1 1 1

Pcalcd g/cm3 1.503 1.510 1.525

p., mm-1 1.394 1.488 1.675

F(000) 842 838 846

9 Range, deg 1.84-25.30 3.16-25.20 2.78-25.40

Reflection collected 9551 30340 13496

Independent reflections (R^j) 9551 (0.0191) 30340 (0.4401) 13496 (0.0609)

Reflections with I > 2o(I) 5836 4397 5271

Number of parameters 463 463 458

R1, wR2 (I> 2ct(I))* 0.0373, 0.1014 0.0786, 0.1226 0.0481, 0.1227

R1, wR2 (all data)** 0.0433, 0.1066 0.1849, 0.2156 0.0910, 0.1558

O-H = 0.83 and H-H = 1.38 Á, each within a standard deviation of 0.01 and 0.02 Á, respectively. Table 1 shows crystallographic data of I—III. Selected bond distances and bond angles are listed in Table 2. Some H-bonded parameters are listed in Table 3.

Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (CCDC nos. 1045041 (I), 1045042 (II), 1045043 (III); depo-sit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

Hirshfeld surface analysis. Molecular Hirshfeld surfaces [19] in the crystal structure were constructed on the basis of the electron distribution calculated as the sum of spherical atom electron densities [20, 21]. For a given crystal structure and a set of spherical atomic densities, the Hirshfeld surface is unique [21]. The normalized contact distance (dnorm) based on both de and d¡ (where de is distance from a point on the surface to the nearest nucleus outside the surface and d¡ is distance from a point on the surface to the nearest nucleus inside the surface) and the vdW radii of the atom, as given by Eq. (1) enables identification of the regions of particular importance to intermolecular interac-

' R = S(F0 - FC)/S(F0), ** wR2 = {S[w( F02 - FC2)2]/S(F02)2 }1/2.

X-ray crystallography. Single crystal X-ray diffraction analyses of the compounds were carried out on a Bruker SMART APEX II CCD diffractometer equipped with a graphite monochromated Mo^a radiation (k = 0.71073 A) by using ® scan technique at room temperature. The intensities were corrected for Lorentz and polarization effects as well as for empirical absorption based on multi-scan techniques; all structures were solved by direct methods and refined by full-matrix least-squares fitting on F2 by SHELX-97 [18]. Absorption corrections were applied by using multi-scan program SADABS. The hydrogen atoms of organic ligands were placed in calculated positions and refined using a riding on attached atoms with isotropic thermal parameters 1.2 times those of their carrier atoms. In III, 38% of the data were observed, which may be attributed to the small measurable crystals and the relatively bad quality of data. The water hydrogen atoms were refined with isotropic thermal parameters 1.5 times those of their carrier atoms. The H atoms of free water molecule were located in a difference Fourier map and then refined as riding in their as-found relative positions with distance restraints of

Table 2. Selected bond distances (À) and angles (deg) of structures I—III

Bond d, Â Bond d, Â

Pr(1)-O(1) Pr(1)—O(4) Pr(1)—O(8) Pr(1)-N(2) Nd(1)-O(1) Nd(1)-O(4) Nd(1)-O(7) Nd(1)-N(2) Sm(1)-O(1) Sm(1)-O(4) Sm(1)-N(1) 2.562(4) 2.414(4) 2.610(3) 2.660(5) I 2.529(7) 2.498(8) 2.404(7) 2.645(11) I 2.503(4) 2.372(5) 2.607(5) Pr(1)-O(2) Pr(1)-O(7) Pr(1)-N(1) I Nd(1)-O(2) Nd(1)-O(5) Nd(1)-N(1) I Sm(1)-O(2) Sm(1)-O(7) Sm(1)-N(2) 2.631(3) 2.527(4) 2.649(5) 2.613(7) 2.587(6) 2.634(8) 2.610(5) 2.382(6) 2.628(5)

Angle ro,deg Angle ro, deg

O(1)Pr(1)O(2) O(1)Pr(1)O(7) O(1)Pr(1)N(1) O(2)Pr(1)O(8) O(4)Pr(1)O(7) O(1)Nd(1)O(2) O(1)Nd(1)O(5) O(1)Nd(1)N(1) O(2)Nd(1)O(4) O(2)Nd(1)N(1) O(1)Sm(1)O(2) O(2)Sm(1)N(2) O(4)Sm(1)N(1) O(7)Sm(1)N(1) 49.88(12) 143.91(13) 83.67(12) 138.36(11) 79.67(11) I 50.1(2) 153.6(2) 84.2(2) 143.6(2) 74.9(2) I 50.79(15) 108.16(16) 79.60(17) 143.28(17) O(1)Pr(1)O(4) O(1)Pr(1)N(2) O(2)Pr(1)O(7) O(4)Pr(1)O(8) O(4)Pr(1)N(2) I O(1)Nd(1)O(4) O(1)Nd(1)O(7) O(1)Nd(1)N(2) O(2)Nd(1)O(5) O(2)Nd(1)N(2) I O(1)Sm(1)O(4) O(4)Sm(1)O(7) O(4)Sm(1)N(2) O(7)Sm(1)N(2) 125.89(12) 69.65(14) 144.42(10) 70.32(10) 137.52(13) 144.3(3) 125.4(2) 70.3(3) 137.6(3) 108.1(2) 126.25(15) 74.71(16) 137.62(2) 147.64(16)

tions. The combination of de and d¡ in the form of two-dimensional (2D) fingerprint plot [22, 23] provides a summary of intermolecular contacts in the crystal [19]. The Hirshfeld surfaces mapped with dnorm and 2D fingerprint plots were generated using the Crystal-Explorer 2.1 [23]. Graphical plots of the molecular Hirshfeld surfaces mapped with dnorm used a red-white-blue colour scheme, where red highlight shorter contacts, white represents the contact around vdW separation, and blue is for longer contact. Additionally, two further coloured plots representing shape index

and curvedness based on local curvatures are also presented in this paper [24].

, vdW , vdW

d = di - n + d e - r e

norm v-dW vd-W .

rr

ie

Synthesis of complex I. A mixture of H2O (10 mL) and CH3OH (5 mL) solution containing HL (0.1 mmol) and was added Pr(NO3)2 • 4H2O (0.15 mmol) in water at 60°C. The pH of the resulting solution was adjusted to 6 using dilute NaOH

Table 3. Geometric parameters of hydrogen bonds for I—III

Distance, À

Angle OHO, deg

O(9)-O(1)

O(6)-O(1w)

O(3)-O(2)

O(1w)-O(3)

O(1w)-O(2w)

O(2w)—O(9)

O(2w)-O(6)

O(3)-O(2) O(9)-O(1w) O(6)-O(1) O(76)-O(7)

I

2.

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