Inorganic-Organic Hybrid Materials with Novel Framework Structures: Synthesis, Structure, and Magnetic Properties of [Ni(py) 4 ] 2 V 10 O 29 and [Ni 2 (py) 5 (H 2 O) 3 ]V 4 O 12 M. Ishaque Khan,* ,† Renata C. Nome, † Sangita Deb, † James H. McNeely, † Brant Cage, † and Robert J. Doedens* ,‡ Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, Chicago, Illinois 60616, and Department of Chemistry, UniVersity of California, IrVine, California 92697 ReceiVed February 3, 2009; ReVised Manuscript ReceiVed March 25, 2009 ABSTRACT: Inorganic-organic hybrid materials [Ni(py) 4 ] 2 V 10 O 29 (1) and [Ni 2 (py) 5 (H 2 O) 3 ]V 4 O 12 (2) have been synthesized and characterized by infrared spectroscopy, thermogravimetry, magnetometry, and complete single crystal structure analysis. The crystal structures of 1 and 2 exhibit novel three-dimensional covalent networks. The framework structure in 1 contains polyoxometallate groupings of stoichiometry {V 10 O 29 } which are constructed from two cyclic {V 4 O 12 } units bound to centrosymmetric {V 2 O 7 } species. V-O-Ni bridges in the a- and b-directions join these units to two crystallographically independent trans-[Ni(py) 4 O 2 ] octahedra. The nickel- and vanadium-based moieties occupy alternating channels along the c-direction. The structure of 2 consists of octahedral species [Ni(py) 3 (H 2 O)O 2 ] and [Ni(py) 2 (H 2 O) 2 O 2 ] which are linked into a three-dimensional covalent network by the sharing of oxygen atom vertices with tetrahedral {VO 4 } groups. Compounds 1 and 2 are thermally stable up to 200 and 175 °C, respectively. Both compounds show Curie-Weiss type magnetic behavior over the temperature range 1.9-300 K. The effective magnetic moment in both cases is 3.0 µ B , revealing the presence of significant orbital contribution. Single ion magnetization as a function of magnetic field showed linear behavior for 1 and 2 over the range of 0-1 T. At a magnetic field of 9 T, 1 approaches saturation at 2 µ B per Ni 2+ ion, whereas 2 does not approach saturation well. Introduction Inorganic-organic hybrid materials are of current interest. 1-9 A variety of these materials have been reported in recent years. Many exhibit interesting host-guest chemistry, 10 separation, 11-14 catalytic, 15-17 and optical properties. 18 Some of these systems have been also reported to show promising gas absorption properties for H 2 , CH 4 , and CO 2 . 19-24 The properties of the hybrid materials can, in principle, be modified and improved by the amalgamation of the appropriate building blocks with desirable functionalities. However, despite the significant amount of ongoing research efforts in this field which has yielded an impressive array of materials, the rationalized approach for the design and synthesis of hybrid materials with desirable and predictable properties remains underdeveloped. In view of the rich redox chemistry associated with vanadium and the structural variety exhibited by oxovanadates, 25,26 we have been interested in developing strategies for the synthesis of vanadium oxide-based hybrid materials. For this purpose, we have employed discrete oxovanadate motifs, vanadium oxide chains, and layered structures in combination with metal-organic complexes of the first row transition metals to prepare hybrid materials composed of mixed metal oxide {V/O/M/O} (M ) Mn, Fe, Co, Ni, Cu, etc.) framework incorporating organic functionalities. In this approach, metal-organic cationic com- plexes can serve both as cross-linkers for vanadium oxide building units and provide charge balance to generate neutral framework structures. This effort has led to the synthesis and characterization of a series of new materials. 27-37 Here we report the synthesis of two new open-framework hybrid materials [Ni(py) 4 ] 2 V 10 O 29 (1) and [Ni 2 (py) 5 (H 2 O) 3 ]V 4 O 12 (2) (py ) pyridine) with a novel covalent network structure which have been characterized by infrared spectroscopy, thermogravimetry, elemental analysis, magnetometry, and complete single crystal X-ray structure analyses. Experimental Section Materials and Methods. Reagent grade materials from commercial sources were used without further purification in the syntheses of 1-2. The hydrothermal reactions were performed in 23 mL Parr Teflon- lined acid digestion bombs. Of the several preparation methods, only those which produced high purity and X-ray quality single crystals in decent yield are reported here. Infrared spectra (KBr pellet: 4000-400 cm -1 ) were recorded as KBr pellets using a Nexus 470 spectrometer from Thermonicolet and were evaluated by Thermonicolet’s OMNIC software. A Mettler Toledo TGA/SDTA 851E thermogravimetric analyzer (TGA) was used to obtain TGA curves in N 2 atmosphere. The TGA results were analyzed by Mettler Toledo STAR 7.01 software. 38 Approximately 10 mg samples were placed in a 70 µL alumina pan and heated over the temperature range of 25-1000 °C at a rate of 5 °C per minute in nitrogen atmosphere with a flow rate of 70 mL/min. The residues from TGA studies were examined by IR spectroscopy. The ac and dc magnetic measurements were obtained using a Quantum Design Physical Properties Measurement System (PPMS). Sample sizes were between 20-40 mg measured in a standard gelcap contained within a drinking straw. Samples were cooled to 1.9 K at zero field, a static field of 0.1 T (T) was set, and the temperature was swept from 1.9 to 300 K. No hysteresis in the field-cooled data was observed. The  ac magnetization was done at 0.1 T with a 10 Oe alternating field. The estimates given for  D in Table 1 were not corrected for the sample holder assembly. The results of the  dc and  ac were in agreement. The parameters and data for temperature dependent studies in Table 1 are from  ac due to the superior signal- to-noise. Crystal Structure Analyses. Crystallographic data were collected at low temperature on a Bruker SMART-1K CCD diffractometer. Crystals were immersed in hydrocarbon oil and mounted on a thin glass fiber in a cold nitrogen stream. Preliminary unit cell parameters and crystal orientation were determined by standard procedures. 39 A full sphere of diffraction data was collected in frames separated by 0.3° increments in ω. The first 50 frames were remeasured at the end of * Corresponding author: E-mail: khan@iit.edu (M.I.K.); rdoedens@uci.edu (R.J.D.). † Illinois Institute of Technology. ‡ University of California. CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 6 2848–2852 10.1021/cg9001237 CCC: $40.75  2009 American Chemical Society Published on Web 04/24/2009