邱燕璇 楊 猛 嚴(yán) 華 高斐鮮 歐陽振杰 董 文

(廣州大學(xué)化學(xué)化工學(xué)院，廣州 510006)

0 Introduction

The 5,5-bis(1H-tetrazoly)amine (H2BTA, CAS No.127661-01-2)functional ligand has been found recently a good building block to self-assemble 3d or 4f metal supramolecular complex[1-6]. The H2BTA and its deprotonated anions (scheme 1)can control the crystal structures using not only the hundreds of different coordinating and bridging modes to metal ions,but also simultaneously the formation of complementary intermolecular N-H…N and N-H…O hydrogen bonds in diverse environments[1-10]. The control of different crystal structures is essential to advance crystal engineering and to construct the desired molecular materials. Up to now, the report concerning the structures of H2BTA and Sm3+metallic complexes, to the best of our knowledge, has been very limited[2].H2BTA can be prepared by cycloaddition of neutral or ionic azides and cyanogroups[6]. Here, we report the synthsis of the novel Sm3+mononuclear complex [Sm2(BTA)3·(H2O)10]·5H2O (1) based on H2BTA functional ligand.

Scheme 1 H2BTA with three reversible types of protonated, deprotonated, triprotonated mode

1 Experimental

1.1 Materials and instrumentation

All analytical grade chemicals and solvents were purchased commercially and used without further purification. Deionized water was used for the conventional synthesis. H2BTA ligand was prepared by the reaction of sodium dicyanamide and sodium azide in the presence of water according to the literature via a Demko-Sharpless synthesis method[6]. Elemental analyses of C, H and N were made on a Perkin-Elmer 240C elemental analyzer. The calculation fluorescence spectrum of 1 uses Gaussian 09 program package.

1.2 Synthesis of 1

A mixture of H2BTA (0.031 g,0.2 mmol),SmCl3·6H2O(0.073 g, 0.2 mmol) aqueous solution(20 mL) was heated in a 25 mL Teflon-lined autoclave at 160℃for 72 h, followed by slow cooling (5 ℃·h-1) to room temperature. The resulting mixture was filtered and colorless crystals of 1 were collected and dried in air(65%yield based on H2BTA).Elemental analysis calcd.for [Sm2(BTA)3·(H2O)10]·5H2O (%)： C 7.03, H 3.23, N 36.90;found(%)：C 7.01,H 3.24,N 36.87.

Caution： Although not encountered in our experiment, azide and complexes of metal ions are potentially explosive，the materials should be handled with care and only small amount of materials should be prepared.

1.3 X-ray data collection and structure determination of 1

The crystallographic data collection of 1 was carried out on a Bruker Smart APEX-Ⅱ CCD diffractometer at 296(2) K, using graphite-monochromatized Mo Kα radiation(λ=0.071 073 nm). Empirical absorption correction was applied by SADABS program.The structure was solved by direct methods and refined by full-matrix least-squares procedure based on F2in SHELX-97 program. All non-hydrogen atoms were refined anisotropically, hydrogen atoms were placed by the calculated positions and refined isotropically. The crystal data, details on data collection and refinement, are summarized in Table 1 and selected bond lengths and angles are given in Table 2.

Table 1 Crystallographic data and refinement parameters for 1

Table 2 Selected bond lengths (nm) and angles (°) for 1

2 Results and discussion

2.1 Crystal structure of 1

Fig.1 Atomic labeling diagram of 1(30% thermal ellipsoids)

Complex 1 crystallizes in the triclinic system with space group.Each unit of 1 consists of two Sm3+ions,three BTA2-anions and fifteen water molecules. Fig.1 gives the atomic labeling diagram of 1.Both Sm (1)and Sm (2) ions exhibit a distorted tetragonal antiprism structure with each Sm (1) ion coordinating to two chelated N atoms of one BTA anion and six oxygen atoms from six water molecules and each Sm(2) ion coordinating to two BTA anions and four water molecules. The main Sm-N bond lengths are Sm(1)-N(19)0.250 5(3),Sm(1)-N(24)0.251 5(3)nm and Sm(2)-N(1)0.251 9,Sm(2)-N(6)0.252 1,Sm(2)-N(10)0.252 2,Sm(2)-N(15)0.258 9 nm.The Sm-O bond lengths are in the range of 0.237 8(3)～0.248 9(3) nm(table 2). Three different intermolecular hydrogen bonding interactions of O-H…N, O-H…O and N-H…N are observed in 1(Fig.2)： (a)hydrogen bonds between coordinated water molecules and uncoordinated nitrogen atoms with O…N distance range of 0.267 2 to 0.298 0 nm (Fig.2a); (b)hydrogen bonds between coordinated and uncoordinated water molecules with O …O distance range of 0.257 4 to 0.292 0 nm (Fig.2b); (c)hydrogen bonds between uncoordinated amine N atom and tetrazole N atoms with N…N distance range from 0.287 5 to 0.288 9 nm. A 3D supermolecular structure is formed by these O-H…N, O-H…O and N-H…N intermolecular hydrogen bonds linking the Sm3+complex units and uncoordinated water molecules.

Fig.2 (a) Intermolecular hydrogen bond in 1 and (b) The O-H…O hydrogen bonds in 1

2.2 Luminescent spectrum

The luminescent spectrum of aqueous solution of 1 with the concentration of 10-4mol·L-1at room temperature is shown in Fig.3. The aqueous solution of 1 exhibits the excitation peak at 315 nm and the emission maximum at 405 nm. The luminescence of 1 should be attributed to the π-π transitions of BTA anion.The emission spectrum for Sm3+ion has not been observed. The fluorescence spctrum of 1 is calculated on the basis of TDDFT/6～31g(d) and PCM model using Gaussian 09 program package. The calculated wavelength (312 nm) is in accordance with the experimental value(315 nm).

Fig.3 (a) Excitation spectrum and (b) Emission spectrum for aqueous solution of 1 (10-4 mol·L-1)at room temperature (c) calculated excitation spectrum

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