Abstract
The synthesis and molecular structure of a dimeric, mono-aluminum complex composed of two tri-lacunary α-Dawson polyoxometalates, [H14Al(B-α-P2W15O56)2]7− (1), is described herein. The tetra-n-butylammonium salt of 1, [(n-C4H9)4N]7[H14Al(B-α-P2W15O56)2] (TBA-1) was prepared by passing an aqueous solution of K6[B-α-H3P2W15O59{Al(OH2)}3]⋅14H2O through an ion-exchange resin column (H+-form), followed by addition of tetra-n-butylammonium bromide. Analytically pure and colorless crystals of TBA-1 were obtained via vapor diffusion from acetonitrile/methanol at ~25 °C. Single-crystal X-ray structure analysis revealed that a six-coordinate aluminum ion was sandwiched between two tri-lacunary α-Dawson-type units, resulting in an overall C2h symmetry. The characterization of TBA-1 was accomplished by elemental analyses, thermogravimetric/differential thermal analyses, Fourier-transform infrared spectroscopy, and solution 31P nuclear magnetic resonance spectroscopy. The photochromic properties of TBA-1 were also characterized in methanol under light irradiation (λ = 365 nm and ≥400 nm).
Highlights
Aluminum and its derivative alloys, oxides, organometallics, and inorganic compounds have been used in many fields due to their unique properties including high reactivity, acidity, hardness, and electroconductivity [1,2]
Since the properties and activities of aluminum species strongly depend on the aluminum site structures, the synthesis of aluminum compounds with structurally well-defined aluminum sites is important for the development of useful aluminum-based materials
X-ray crystal structure, and photochromic properties of TBA-1
Summary
Aluminum and its derivative alloys, oxides, organometallics, and inorganic compounds have been used in many fields due to their unique properties including high reactivity, acidity, hardness, and electroconductivity [1,2]. Even when conditions are carefully controlled during preparation, the construction of well-defined aluminum structure is often difficult [2,3,4]. Polyoxometalates have attracted much attention in the fields of catalytic chemistry, surface science, and materials science because of their controllable shape, size, composition, and structural diversity [5,6,7,8,9]. Various techniques for functionalization of polyoxometalates have been reported, the synthetic technology of introducing metal ions into vacant sites using lacunary polyoxometalates as inorganic ligands is an effective technique for constructing stable and well-defined active metal centers. In terms of polyoxometalates containing aluminum ions as heteroatoms, various aluminum compounds have been synthesized and structurally characterized [10,11,12,13,14,15,16,17]
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