In recent years, hydrothermal synthesis and structural characterization of open-framework metal phosphates templated with organic diamines have attracted the attention of scientists because they represent the interaction between organic and inorganic chemistry and can be applied in lots of branches of chemistry with their different characteristic properties. In this study, a novel open-framework polyoxometal phosphate compound (4,4'-bpyH2)2(4,4'-bpyH)[PCoW11O39].H2O was synthesized with hydrothermal method as red crystals. The compound crystallizes in the space group P2(1)/n of the monoclinic system with four formula units in a cell. The crystal is a Keggin polyoxometalate structure and contains free 4,4'-bipyridine groups and water molecule between the clusters. In addition to this novel compound, three known compounds were synthesized. Co(4,4'-bpy)2(VO2)2(HPO4)2 red crystals were synthesized hydrothermally and the compound crystallizes in the space group C2/c of the monoclinic system with four formula units in a cell. The crystal consists of [(VO2)(HPO4)]∞ helical chains and [Co(4,4'-bpy)2]2+ frameworks. Also, NaCo3(PO4)(HPO4)2 pink crystals were obtained with using hydrothermal synthesis. The compound crystallizes in the space group C2/c of the monoclinic system with four formula units in a cell. In the structure, CoO6 chains connect to the PO4 and HPO4 groups. Lastly, (enH2)3[CoW4P4O28] blue crystals were synthesized with hydrothermal method and crystallizes in the space group I4(1)/a of the tetragonal system with four formula units in a cell. The crystal consists of a [Co3W4P4O28]6- anion and three free ethylenediaminium (N2H10C2)2+ cations.

Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids. Most of them are based upon oxygen containing materials especially phosphates, and they exhibit fascinating architectures with unusual bonding and coordination environment. Besides metal phosphates and phosphites, inorganic-organic hybrids constitute an important family of open-framework structures. In this thesis, results of investigations of a variety of open-framework metal phosphates, metal phosphites, as well as a new family of phosphite-oxalates are presented. More importantly, studies directed towards the synthesis and understanding of the magnetic properties of various transition metal phosphates, phosphites, phosphite-oxalates and the upconversion behavior of uranium phosphites are discussed at length. In Chapter 1 of the thesis an overview of inorganic open-framework materials is presented. In Chapter 2 and 3, the synthesis, structure of open-framework zinc (Part A of both Chapters) and synthesis, structure and magnetic properties of open-framework iron (Part B of both Chapters) are presented. Some of these compounds show unusual structure and interesting properties. For example, two-dimensional iron phosphate exhibits ferrimagnetism whereas three-dimensional iron phosphate with SBU-6 and SBU-2 is antiferromagnetic. The three-dimensional iron phosphite exhibits small polarization at low field. In Chapter 4, we present a new family of organically templated hybrid materials synthesized by partially substituting the phosphite by the oxalate ion in manganese, iron and cobalt phosphites. These exhibit a wide range of structures in which the oxalates play an unusual dual role. Some of these compounds show interesting magnetic properties. For e.

Crystalline nanoporous materials like zeolites and metal phosphates (e.g. AlPOs) are used commercially for catalysis, adsorption, molecular sieving, and ion exchange. Their properties are related to both their porous architectures and chemical compositions. Materials that incorporate tin(II) and antimony(III), with stereochemically active lone electron pairs, could impart properties different from those of materials based on aluminum, cobalt, zinc, iron, and other metals that adopt [MO4] tetrahedra. Exploratory hydrothermal synthesis resulted in thirty new tin(II) and antimony(III) materials, including the first open-framework antimony(III) phosphate. Structure determination was by single crystal X-ray diffraction. Some materials incorporate a three-ring chain motif observed in other metal phosphates. Previously proposed metal phosphate formation mechanisms are shown not to adequately describe its formation. A new mechanism is proposed, adapting the Partial Charge Model of Livage, et al. to tin(II) and antimony(III) phosphates. This mechanism, starting from open chain metal phosphate 'wires' (with M-O-P bonds), is then extended to other metal phosphates.

The synthesis of new manganese phosphate compound, Sr2MnP3O11, by hydrothermal reaction of Mn2O3, SrCO3 and H3PO4 in presence of water at 230 for 5 days is reported. The compound crystallizes in the space group P 21/c of the monoclinic system with three formula units in a cell of dimensions a=6.6410(13) b=6.8341(14) c=19.055(14) =99.22(3) V=853.6(3) The structure is composed of MnO6, PO4 and P2O7 groups and Sr cations. It has three dimensional structure including channels n which the Sr cations are placed.The pale pink single crystals of the Hureaulite mineral, Mn5(H2O)4[PO3(OH)]2[PO4]2, were synthesized hydrothermally via the reaction of SrCO3, MnCl2, H3PO4 and H2O at 180C for 3 days. The compound is in the crystal system of monoclinic with unitcell parameters a=17.600(4), b=9.1214(18), c=9.4786(19) and =96.52(3)and in the space group C2/c. The structure possesses a three-dimensional architecture containing channels and is made up of MnO6 and PO4, which are joined with others by sharing corners.All detailed structural information of the synthesized materials was done via commercial software programs SHELX and Crystal Structure.

Prof. CNR Rao is a living legend. Einstein paid a compliment to Mahatma Gandhi on his 70th birthday. He said, “Generations to come, it may well be, will scarce believe that such a man as this one ever in flesh and blood walked upon this earth”. On Prof. Rao’s birthday, I would repeat these words. Prof. Rao is not an individual, he is an institution, he is a phenomenon. I feel lucky that our generations could see him, touch him, feel him, experience him, learn from him and get inspired by him. I have watched Prof. Rao as a scientist, as a science leader, as a science institution builder and indeed as a leader of leaders of science. I have also watched him as a wonderful, warm-hearted human being with abundant empathy. I have seen his childlike enthusiasm. I have watched him as `courage personified’. What follows is more anecdotal but solely based on my personal viewpoint. Professor Rao has had a tremendous influence on my life. He has been my guru, guide, friend and philosopher. I met him for the first time when he was the Chairman of the Research Advisory Council of the National Chemical Laboratory (NCL) in the nineteen eighties. I was then in my late thirties. Professor Rao has an uncanny ability to spot talent among the young. He was the President of the Indian Science Congress in the year 1988, which was held in Pune University. Mr. Rajiv Gandhi was the Prime Minister and he inaugurated the Science Congress. Later on, during the lunch that followed, Prof. Rao made a special point to introduce me to Rajiv Gandhi. I still remember his words. He said, `Mr. Prime Minister, meet a rising young star of Indian science’. Little did I then know that within the next couple of months, he would make me a member of the Science Advisory Council to the Prime Minister, which he was chairing. At 42, I was the youngest member and I remember people calling me the `baby’ of the team. Getting that huge exposure at such a young age was something very special for me – I got a helicopter view of India at large. It helped me enormously as I moved on in life. 'Padma Vibhushan' Dr. Raghunath Anant Mashelkar