Growth of Copper Pyrazole Complex Templated Phosphomolybdates: Supramolecular Interactions Dictate Nucleation of a Crystal

Abstract

Five copper pyrazole complex based phosphomolybdates are self assembled at room temperature from an aqueous solution containing sodium molybdate, cupric chloride, and pyrazole acidified with phosphoric acid: one-dimensional (1D) chains in [{Cu(pz)(H2O)}{Cu(pz)3(H2O)}{Cu(pz)4}{P2Mo5O23}], 1, copper pyrazole complex intercalated two-dimensional (2D) sheets in {Cu(pz)2(H2O)4}[{Cu(pz)2(H2O)}2{Cu(pz)4}2{HP2Mo5O23}2]·6H2O, 2, hexadecameric water clusters incorporated between 1D chains in [{Cu(pz)4}3{Cu(pz)3(H2O)}2{HP2Mo5O23}2]·9H2O, 3, a water-mediated interpenetrated three-dimensional (3D) network in [{Cu(pz)4}2{H2P2Mo5O23}]·H2O, 4, and copper pyrazole complex pillared 2D phosphomolybdate sheets in [{Cu(pz)2}P2Mo2O12(H2O)2], 5. Detailed structural characterization of these solids was established by single crystal and powder X-ray diffraction techniques, FTIR, and thermal analysis. This paper proposes intuitive mechanisms to provide molecular insights into the role of in situ copper pyrazole complexes generated in solution in dictating a particular supramolecular assembly which eventually influences the nucleation of a crystal through a concerted condensation process. The role of the complexes as intercalant, pillaring unit, etc. has been demonstrated by these examples.