Synthesis, crystal structure, luminescent property and DFT investigation on a novel metal–organic framework constructed from rigid tetrapodal ligand 1,2,3,4-tetra(4-pyridyl)thiophene Jian-Guo Lin a,b , Ling Qiu b , Fang-Ming Wang a , Chang-Sheng Lu a , Qing-Jin Meng a, * , Pei-Heng Wu c a Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China b Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Institute of Nuclear Medicine, Wuxi 214063, PR China c Research Institute of Superconductor Electronics, Department of Electronic Science and Engineering, Nanjing University, Nanjing 210093, PR China article info Article history: Received 30 September 2009 Accepted 13 November 2009 Available online 17 November 2009 Keywords: Cadmium(II) complex Crystal structure Tetradentate ligand Luminescence TDDFT abstract Employing the tetrapodal compound 1,2,3,4-tetra(4-pyridyl)thiophene (TPT) as a bridging ligand, a new metal–organic framework was obtained and characterized by single crystal X-ray diffraction, [Cd(TPT)(N 3 ) 2 Á(H 2 O)] (1). This polymer exhibits a 2D layer network and an unprecedented 3,4-connected topology, which is constructed from the three-connector TPT and EE azido bridges. It also displays good thermal stability and strong photoluminescence in the blue regionband thus may serve as a candidate of thermally stable blue-light-emitting electroluminescence material. The nature of electronic transitions in the photoluminescent process has also been investigated by means of time-dependent density functional theory (TDDFT) calculations and molecular orbital analyses, which shows that the luminescent property is ligand-based. Ó 2009 Elsevier B.V. All rights reserved. Recently, remarkable progress has been made in the area of metal–organic frameworks (MOFs) owing to their fascinating structural diversities and potential applications in materials and biomolecular sciences [1–3]. As well known, the most feasible strategy used to design and construct MOFs is to select suitable polyfunctional ligands that enable the control on structural motifs [4–6]. The compound 1,2,3,4-tetra(4-pyridyl)thiophene (TPT, Chart 1) is rigid and symmetric, which has four potential coordi- nating N-donor atoms. Therefore, it can serve as a versatile ligand and can coordinate to metal ions with diverse modes. In addition, TPT has been found to possess significant fluorescence potency not only in the solution but also in the solid state. Clearly, there are ample opportunities for the design of new MOFs from TPT with interesting structural diversity and applications in the field of opti- cal materials. However, as far as we know, studies on the MOFs assembled from the TPT ligand are still very rare until now, although some functional MOFs constructed from TPT have been investigated recently [7,8]. Therein, the tetradentate ligand TPT exhibited l 3 and l 4 -coordination modes to construct diverse 2D and 3D MOFs, respectively. For the purpose of preparing novel materials with interesting architecture and excellent luminescent properties, we started to elaborate new MOF from TPT in the pres- ence of N À 3 anion. In this paper, a novel MOF was reported, namely [Cd(TPT)(N 3 ) 2 Á(H 2 O)] (1). Its thermal stability and fluorescence property were also studied. The ligand TPT was synthesized according to the previous work [8,9]. Complex 1 was synthesized by adding TPT in ethanol solution to an aqueous solution of Cd(NO 3 ) 2 Á6H 2 O (0.1 mmol) mixed with NaN 3 (0.2 mmol) at room temperature [10]. The single crystal X- ray diffraction study [11] reveals that 1 crystallizes in a space group P  1 and features a 2D layer network built by TPT and N À 3 bridges. As depicted in Fig. 1a, the Cd1 exhibits a slightly distorted octahedral coordination sphere. The apical positions are occupied by two nitrogen atoms (N5, N8) from two azide anions, while the basal plane is completed by four nitrogen atoms from three pyrid- yls of three different TPT ligands (N1, N2A and N3B) and one azide nitrogen atom (N10C), respectively. The central metal ion Cd1 deviates from the basal plane by 0.0648 Å. The distances between the metal atom and different types of nitrogen atoms in the CdN 6 range from 2.239(5) to 2.361(3) Å, which are comparable to the re- ported values. The degrees of distortion from an ideal octahedral geometry are reflected from cisoid angles [83.00(13)–96.12(11)°] and transoid angles [172.40(11)–175.58(14)°]. The calculations using the hybrid B3LYP functional were per- formed on the related mononuclear species [Cd(TPT)(pyri- dyl) 2 (N 3 ) 3 ] À with the ground-state geometry adopted from the truncated X-ray data. Some selected single crystal X-ray diffraction data together with the optimized geometrical parameters at the B3LYP/LANL2DZ level are listed in Table 1. After careful 1387-7003/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2009.11.008 * Corresponding author. Tel.: +86 25 83597266; fax: +86 25 83314502. E-mail address: mengqj@nju.edu.cn (Q.-J. Meng). Inorganic Chemistry Communications 13 (2010) 175–178 Contents lists available at ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche