научная статья по теме ORGANIC-ACID EFFECT ON THE STRUCTURES OF CD(II) METAL-ORGANIC COMPLEXES BASED ON 2-(3-PYRIDYL)IMIDAZO[4,5-F]-1,10-PHENANTHROLINE Химия

КООРДИНАЦИОННАЯ ХИМИЯ, 2010, том 36, № 9, с. 668-679

УДК 541.49

ORGANIC-ACID EFFECT ON THE STRUCTURES OF Cd(II) METAL-ORGANIC COMPLEXES BASED ON 2-(3-PYRIDYL)IMIDAZO[4,5-/]-1,10-PHENANTHROLINE

© 2010 X. L. Wang*, J. X. Zhang, G. C. Liu, H. Y. Lin, and Y. Q. Chen

Faculty of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000, P.R. China

*E-mail: wangxiuli@bhu.edu.cn Received December 30, 2009

Three new Cd(II) complexes consisting of phenanthroline derivative and organic acid ligands, formulated as [Cd3(3-PIP)2(L1)6] (I), [Cd(3-PIP)(L2)] • H2O (II), and [Cd(3-PIP)(L3)] (III) (3-PIP = 2-(3-pyridyl)imi-dazo[4,5-f]-1,10-phenanthroline, HL1 = 3,5-dinitrobenzoic acid, H2L2 = oxalic acid, H2L3 = benzene-1,3-dicarboxylic acid), have been synthesized via the hydrothermal reaction and characterized by single-crystal X-ray diffraction, elemental analyses and FT-IR spectra. Complex I is a trinuclear structure. Complex II features a 1D zigzag chain. Complex III shows a twisted double chain of binuclear units sustained by double car-boxylate bridges. Three complexes are further extended into 3D supramolecular frameworks by hydrogen bonding and n—п-stacking interactions. The structural differences among I—III show that the organic car-boxylates have important effects on the structures. Furthermore, the supramolecular interactions are the critical factors in determining the final structures of the complexes. In addition, the thermal stabilities and luminescent properties of complexes I and II are also investigated.

INTRODUCTION

During the past decade, the self-assembly of metal-organic complexes have attracted much interest due to their intriguing topological structures and interesting applications as functional materials in catalysis, optics, magnetism, etc. [1—4]. To date, a variety of useful metal-organic complexes have been obtained by chemists [5, 6]. However, one of the obvious challenges to chemists is the rational and controllable preparation of the target metal organic complexes in this area, the formation of which is greatly affected by the design of organic ligands, the nature of the metal ions, and other factors [7—9]. As an important family of multidentate O-donor ligands, organic carboxylate anions as bridging ligands seem to be excellent building blocks with variable charge, and versatile coordination modes and can be regarded not only as hydrogen bond acceptors but also as hydrogen bond donors for constructing high-dimensional networks [10-12]. On the other hand, 5,6-substituted 1,10-phenanthroline derivatives have been extensively employed in the preparation of metal-organic complexes as they may provide not only the chelating coordination sites but also the potential supramo-lecular recognition sites for n—n-stacking interactions to form interesting supramolecular structures [13—18].

On the basis of the aforementioned points, we chose three structurally representative organic car-

boxylate ligands (3,5-dinitrobenzoic acid (HL1), oxalic acid (H2L2), and benzene-1,3-dicarboxylic acid (H2L3)) and 2-(3-pyridyl)imidazo[4,5-/]-1,10-phenanthroline (3-PIP) as mixed ligands because of their remarkable advantages: (i) as preferred multifunctional oxygen-donor connectors, a variety of number, and the length and angle of carboxylate groups in these carboxylate acids give a good opportunity to yield novel metal-organic complexes [19—21]; (ii) compared to 2,2'-bipyridine and 1,10-phenathroline, 3-PIP possesses a larger conjugated system for providing potential supramolecular recognition sites for n—n-stacking interactions, and the N atoms of imidazole groups can act as H-bond acceptors and donors to assemble supromolecular structures [14, 15].

In this paper, three new Cd(II) complexes, namely, trinuclear cluster [Cd3(3-PIP)2(L1)6] (I), 1D zigzag chain [Cd(3-PIP)(L2)] • H2O (II) and 1D twisted double chain [Cd(3-PIP)(L3)] (III), have been prepared and investigated to determine the influence of organic acid on the formation of such complexes. Moreover, the thermal stabilities and luminescent properties of complexes I and II have been reported. Coordination modes of the 3-PIP (a), L1 (b, c), L2 (d), and L3 (e) ligands appeared in complexes I—III are following:

O2N

=N N=

W

(a)

NO2

o2n

/O\zO

Ca Cd (b)

.Cd Oy ^O \ /

C-C

/ \ ox /O

Cd

(d)

NO2

O

0

1

Cd Cd (c)

Cd

\

O

O

(e) \

Cd

Cd

Scheme.

EXPERIMENTAL

Solvents and starting materials for the synthesis were commercially available and used as received. The ligand 3-PIP was synthesized according to method [22] and characterized by FT-IR and XH NMR spectra. FT-IR spectra (KBr pellets) were taken on a Magna FT-IR 560 spectrometer. Thermogravimetric data for complexes I and II were performed using a Pyris Diamond thermal analyzer. Fluorescence spectra were recorded at room temperature on a Hitachi F-4500 fluorescence/phosphorescence spectrophotometer.

Synthesis of I. A mixture of Cd(NO3)2 • 4H2O (0.031 g, 0.1 mmol), 3-PIP (0.015 g, 0.05 mmol), HL1 (0.042 g, 0.2 mmol), NaOH (0.008 g, 2.0 ml), and H2O (7 ml) was stirred for 20 min and sealed in a 25 ml teflon-lined stainless-steel container. The container was heated to 160°C, held at this temperature for 4 days, and then cooled to room temperature at a rate of 5°C h-1. Yellow block crystals suitable for X-ray diffraction of complex I were obtained. The yield was ~40% based on Cd.

For C7SH4oCd3N22O36

anal. calcd, %: Found, %:

C, 42.57; C, 42.49;

H, 1.82; H, 1.75;

N, 14.01. N, 14.10.

IR spectrum (KBr; v, cm-1): 3287 w, 3080 m, 2360 w, 1615 s, 1538 s, 1453 m, 1408 m, 1346 s, 1194 w, 1069 s, 917 m, 810 m, 733 s, 526 w.

Synthesis of II. A mixture of Cd(NO3)2 • 4H2O (0.031 g, 0.1 mmol), 3-PIP (0.030 g, 0.1 mmol), H2L2 (0.013 g, 0.1 mmol), NaOH (0.008 g, 2.0 ml), and H2O (7 ml) was stirred for 20 min and sealed in a 25 ml teflon-lined stainless-steel container. The container

was heated to 150°C and held at this temperature for 4 days. Then it was cooled to room temperature at a rate of 5°C h-1. Yellow block crystals suitable for X-ray diffraction of complex II were obtained. The yield was ~50% based on Cd.

For C20H13CdN5O5

anal. calcd, %: C, 46.53; H, 2.52; N, 13.57. Found, %: C, 46.44; H, 2.46; N, 13.49.

IR spectrum (KBr; v, cm-1): 3538 w, 3388 m, 3176 w, 2358 s, 1650 s, 1594 s, 1499 m, 1424 w, 1355 w, 1309 s, 1192 w, 1069 w, 1029 w, 804 s, 742 m, 702 m.

Synthesis of III. A mixture of Cd(NO3)2 • 4H2O (0.031 g, 0.1 mmol), 3-PIP (0.015 g, 0.05 mmol), H2L3 (0.017 g, 0.1 mmol), NaOH (0.008 g, 2.0 ml), and H2O (10 ml) was stirred for 20 min and sealed in a 25 ml teflon-lined stainless-steel container. The container was heated to 170°C and held at this temperature for 2 days. Then it was cooled to room temperature at a rate of 5°C h-1. Yellow block crystals suitable for X-ray diffraction of complex III were isolated by mechanical separation from lots of white amorphous solid. The yield was ~5% based on Cd.

For C26H15CdN5O4

anal. calcd, %: C, 54.37; H, 2.61; N, 12.20. Found, %: C, 54.43; H, 2.58; N, 12.14.

IR spectrum (KBr; v, cm-1): 3070 m, 2920 m, 2856 w, 2353 w, 1610 s, 1544 s, 1385 s, 1075 w, 760 s, 723 s.

X-ray structure determination. A Bruker Apex CCD diffractometer (MoZ~a radiation, graphite monochromator, X = 0.71073 A) was used to collect

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

Parameter Value

I II I

Empirical formula C78H40Cd3N22O36 C20H13CdN5O5 C26H15CdN5O4

Formula weight 2198.55 515.76 573.83

Crystal system Monoclinic Triclinic Monoclinic

Space group C2/c P1 C2/c

a, A 20.9592(13) 9.7563(8) 15.0444(13)

b, A 24.0724(13) 10.0403(9) 15.9118(13)

c, A 15.5509(9) 11.5126(16) 19.0246(16)

a, deg 90 110.1270(10) 90

P, deg 93.1420(10) 99.0560(10) 110.337(2)

Y, deg 90 108.8490(10) 90

V, A3 7834.2(8) 955.21(18) 4270.3(6)

Z 4 2 8

Pcalcd g cm—3 1.864 1.793 1.785

Crystal size, mm 0.28 x 0.23 x 0.17 0.29 x 0.26 x 0.18 0.229 x 0.217 x 0.208

F(000) 4376 512.0 2288

9 range, deg 1.69-25.00 1.98-25.00 1.93-24.99

Ranges of h, k, and l indices -24 < h < 24 -11 < h < 6 -17< h < 15

-28 < k < 27 -11 < k < 11 -18< k < 15

-10< l < 18 -13 < l < 13 -22< l < 22

Reflections collected/unique 19753/6873 4883/3326 10705/3744

^int 0.0303 0.0137 0.0396

GOOF 1.044 1.014 0.917

R1, wR2 (I> 2ct(T))* 0.0644/0.1867 0.0252/0.0647 0.0321/0.0788

R1, wR2 (all data) 0.0831/0.2003 0.0297/0.0667 0.0562/0.0918

Max and min transmission 0.855/0.775 0.805/0.715 0.800/0.783

* R = SjlFoi - lFc№o|; wR2 = S[w(F20

2 2 2 2 -, n -F2) ]/S[w(Fo2) ]1/2.

data. The structures were solved by direct methods with SHELXS-97 and Fourier techniques and refined by the full-matrix least-squares method on F2 with SHELXL-97 [23, 24]. All non-hydrogen atoms were refined anisotropically, hydrogen atoms of the ligands were generated theoretically onto the specific atoms

and refined isotropically with fixed thermal factors, and the H atoms of water molecules were located in different Fourier synthesis maps. All crystal data and structure refinement details for the three compounds are given in Table 1. The data of relevant bond distances and angles are listed in Table 2. Hydrogen bonding

Table 2. Selected bond lengths and angles for complexes I—III*

Bond d, Â Bond d, Â

Cd(1)-O(2) Cd(1)-N(1) Cd(1)-O(14) Cd(2)-O(1)#1 Cd(2)-O(8) Cd(2)-O(14)#! Cd(1)-O(2)#2 Cd(1)-N(1) Cd(1)-O(3) Cd(1)-O(3) Cd(1)-N(2) Cd(1)-O(2) 2.195(6) 2.324(5) 2.354(4) 2.213(6) 2.241(5) 2.376(4) I 2.248(2) 2.286(2) 2.342(2) I 2.221(3) 2.358(3) 2.371(3) Cd(1)-O(7) Cd(1)-N(2) Cd(1)-O(13) Cd(2)-O(1) Cd(2)-O(8)#1 Cd(2)-O(14) I Cd(1)-O(1) Cd(1)-O(4) Cd(1)-N(2) I Cd(1)-O(4)#3 Cd(1)-N(1) Cd(1)-O(1) 2.225(5) 2.326(5) 2.566(5) 2.213(6) 2.241(5) 2.376(4) 2.253(2) 2.3245(19) 2.380(2) 2.257(3) 2.368(3) 2.401(3)

Angle ro, deg Angle ro, deg

I

O(2)Cd(1)O(7) 97.0(2) O(2)Cd(1)N(1) 111.2(2)

O(7)Cd(1)N(1) 89.32(18) O(2)Cd(1)N(2) 90.9(2)

O(7)Cd(1)N(2) 161.13(19) N(1)Cd(1)N(2) 71.83(18)

O(2)Cd(1)O(14) 97.8(2) O(7)Cd(1)O(14) 1

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