Structural Phase Transition Behavior Observed for a Single Crystal of the Tetrabutylammonium Salt of a Mo18 Polyoxometalate

Abstract

Ionic single crystals of the polyoxometalate [Mo V 2 Mo VI 16 O 54 (SO 3 ) 2 ] 6salted with tetrabutylammonium were found to exhibit dielectric anomalies at 235 and 302 K. The clear DSC peak at 235 K indicates the first-order nature of transition. The next transition at 302 K was concluded to be secondorder in nature, demonstrating the existence of three different phases (α, , and γ). Temperature-dependent single-crystal X- [a]

Structural Phase Transitions of a Molecular Metal Oxide

“…Only 20 examples are known of single‐crystal–single‐crystal (SCSC) transformations [17, 18] . A first‐order reversible phase transition was reported in the tetrabutylammonium (TBA) salt of [Mo V 2 Mo VI 16 O 54 (SO 3 ) 2 ] 6− , although the phase transition occurred via orientational changes in the alkyl chains of the countercation, and the structure of the POM was unchanged [19] . Infinite metal oxides of Mo VI , W VI , V V and Nb V exhibit dynamic structural transitions by distorting MO 6 octahedrons; however, POMs exhibit few macroscopic and dynamic transition events [17b] …”

Molecular motion of halogenated ethylammonium/[18]crown-6 supramolecular ions in nickel dithiolate magnetic crystals

“…Although rare, order-disorder type molecular motion of alkyl chains has been observed to take place in closely packed crystals, and to play an important role in governing unique functions such as ferroelectricity. [1][2][3][4][5][6][7][8][9][10][11][12][13] For example, ethyl groups in C2H5NH3 + moieties in (C2H5NH3 + )2[BiBr5] crystals at room temperature 11 display orientational disorder between two sites. In the frozen state at 160 K, the crystals undergo a phase transition associated with a change of the crystal space group from non-polar Aeam to polar Pca21.…”

Structural Phase Transitions of a Molecular Metal Oxide

“…[17,18] A first-order reversible phase transition was reported in the tetrabutylammonium (TBA) salt of [Mo V 2 Mo VI 16 O 54 (SO 3 ) 2 ] 6À , although the phase transition occurred via orientational changes in the alkyl chains of the countercation, and the structure of the POM was unchanged. [19] Infinite metal oxides of Mo VI , W VI , V V and Nb V exhibit dynamic structural transitions by distorting MO 6 octahedrons; however, POMs exhibit few macroscopic and dynamic transition events. [17b] In this work, we observed a first-order phase transition in a new organic hybridized basket POM, [Na@(SO 3 ) 2 (n-BuPO 3 ) 4 Mo V 4 Mo VI 14 O 49 ] 5À (Molecule 1; Figure 1), by deforming the molecular metal oxide.…”