Crystallization of Anderson-Evans Type Chromium Molybdate Solids Incorporated with a Metal Pyrazine Complex or Coordination Polymer

摘要

Five new metal pyrazine complex templated Anderson-Evans cluster based solids, (Hpyz)[{Co(pyz)_2(H_2O)_2}{CrMo _6(OH)_6O_(18)}]?_2H_2O (7), (Hpyz)[{Zn(pyz)_2(H_2O)_2}{CrMo _6(OH)_6O_(18)}]?_2H_2O (8), [{Ni(pyz)(H_2O)_4}_2{CrMo_6(OH) _6O_(18)}](CH_3COO)_2?6H _2O (9) (pyz = pyrazine), [Na(CrMo_6(OH)_8O _(16))]?10H_2O (10), and (Hpyz)[{Ni(pyz) _2(H_2O)_2}{CrMo_6(OH)_6O _(18)}]?_2H_2O (11) were crystallized from aqueous solution by reacting sodium molybdate, chromium chloride, metal chloride, and pyrazine at room temperature. The crystal structure, phase purity, and thermal stability of the crystals were established by single-crystal and powder X-ray diffraction, elemental analysis, FTIR, TGA, and magnetic measurements. 7, 8, and 11 are isostructural and show covalently linked 1D anionic chains of alternating Anderson-Evans cluster and cationic complex, {M(pyz) _2(H_2O)_2O_(2/2)} (M = Co, Ni, and Zn); free protonated pyrazinium moieties provide additional counter-charge and further stability through nonbonding interactions. 9 is a rare example of a 1D coordination polymer of the composition {Ni(pyz)(H_2O) _4}~(2+) that supramolecularly aggregates with two counter anions, the discrete molybdate cluster and acetate, along with water molecules. 10 is a new pseudopolymorph of a sodium based chromium molybdate cluster exhibiting 2D layers; the sheets are held together by corrugated water sheets made of decameric water clusters. This paper discusses how weak interactions between aggregating tectons induce different supramolecular assemblies that eventually result in the nucleation of a crystal. The retrosynthetic analysis proposed here provides molecular insights to interpret the crystal engineering of these complex solids and directions for designing new solids in the system.