Crystals springing into action: metal-organic framework CUK-1 as a pressure-driven molecular spring.

Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction. The near-absence of hysteresis upon cycling exhibited by this robust MOF, akin to an ideal molecular spring, is associated with a constant work energy storage capacity of 40 J g-1. Molecular simulations were further deployed to uncover the free-energy landscape behind this unprecedented pressure-responsive phenomenon in the area of compliant hybrid porous materials. This discovery is of utmost importance from the perspective of instant energy storage and delivery.

Structural and Vibrational Study of CsSbGe3O9, a New Germanate in the ASbGe3O9 Family (A = Alkali Metal).

The germanate CsSbGe3O9, grown spontaneously via the high-temperature solution method from Cs2Mo4O13 used as a flux, crystallizes in the orthorhombic system with a = 12.3636(2), b = 13.8521(2), c = 31.4824(5) Å, and V = 5391.73(2) Å3. Its structure, determined from single-crystal X-ray diffraction data, is most probably noncentrosymmetric despite our choice to report it in the centrosymmetric maximal supergroup Pnma D2h16 (no. 62) in which agreement factors R1 = 0.0371 and wR2 = 0.0706 (all data) were obtained. The unit cell contains 24 formulas CsSbGe3O9. The three-dimensional network is built up with regular germanate tetrahedra at nine crystallographically independent Ge sites. The Sb atoms (four independent positions) adopt octahedral coordination with O atoms, and the Cs+ cations are located in the channels of the 3-D network. A more in-depth analysis of the structure of CsSbGe3O9 is carried out in the light of the structures previously determined for the compounds ASbGe3O9 (A = K, Rb) having the same chemical formula but significantly different atomic arrangements. The structural characteristics are discussed related to literature and the nature of the monovalent cation A+.

Room temperature magnetoelectric coupling in a molecular ferroelectric ytterbium(III) complex.

Magnetoelectric (ME) materials combine magnetic and electric polarizabilities in the same phase, offering a basis for developing high-density data storage and spintronic or low-consumption devices owing to the possibility of triggering one property with the other. Such applications require strong interaction between the constitutive properties, a criterion that is rarely met in classical inorganic ME materials at room temperature. We provide evidence of a strong ME coupling in a paramagnetic ferroelectric lanthanide coordination complex with magnetostrictive phenomenon. The properties of this molecular material suggest that it may be competitive with inorganic magnetoelectrics.

Lithium Hydrazinidoborane Ammoniate LiN2H3BH3·0.25NH3, a Derivative of Hydrazine Borane.

Boron- and nitrogen-based materials have shown to be attractive for solid-state chemical hydrogen storage owing to gravimetric hydrogen densities higher than 10 wt% H. Herein, we report a new derivative of hydrazine borane N2H4BH3, namely lithium hydrazinidoborane ammoniate LiN2H3BH3·0.25NH3. It is easily obtained in ambient conditions by ball-milling N2H4BH3 and lithium amide LiNH2 taken in equimolar amounts. Both compounds react without loss of any H atoms. The molecular and crystallographic structures of our new compound have been confirmed by NMR/FTIR spectroscopy and powder X-ray diffraction. The complexation of the entity LiN2H3BH3 by some NH3 has been also established by thermogravimetric and calorimetric analyses. In our conditions, LiN2H3BH3·0.25NH3 has been shown to be able to release H2 at temperatures lower than the parent N2H4BH3 or the counterpart LiN2H3BH3. It also liberates non-negligible amounts of NH3 at temperatures lower than 100 °C. This is actually quite detrimental for chemical H storage, but alternatively LiN2H3BH3·0.25NH3 might be seen as a potential NH3 carrier.

Metal-organic frameworks as potential shock absorbers: the case of the highly flexible MIL-53(Al).

The mechanical energy absorption ability of the highly flexible MIL-53(Al) MOF material was explored using a combination of experiments and molecular simulations. A pressure-induced transition between the large pore and the closed pore forms of this solid was revealed to be irreversible and associated with a relatively large energy absorption capacity. Both features make MIL-53(Al) the first potential MOF candidate for further use as a shock absorber.

Synthesis and characterization of crystalline structures based on phenylboronate ligands bound to alkaline earth cations.

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)(3)(-) coordinated to metal cations: [Ca(PhB(OH)(3))(2)], [Sr(PhB(OH)(3))(2)]·H(2)O, and [Ba(PhB(OH)(3))(2)]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution (1)H, (11)B, and (13)C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively "free" and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the (43)Ca NMR data that are critical to help identify the best model of the structure.

Sonochemical reactions with mesoporous alumina.

Herein, we report the sonochemical reactions with MSU-X mesoporous alumina (m-Al(2)O(3)) in aqueous solutions. Sonication (f=20 kHz, I=30 Wcm(-2), W(aq)=0.67 WmL(-1), T=36-38 degrees C, Ar) causes significant acceleration of m-Al(2)O(3) dissolution in the pH range of 4-11. Moreover, power ultrasound has a dramatic effect on the textural properties and phase composition of m-Al(2)O(3). Short-time sonication at pH = 4 leads to the formation of nanorods and nanofibers of boehmite, AlO(OH). Prolonged ultrasonic treatment causes high aspect morphology transformation to aggregated nanosheets in weakly acid solutions or plated nanocrystals in alkaline solutions. Sonochemical products in alkaline medium are composed principally from boehmite and small amounts of bayerite, Al(OH)(3). Silent hydrolysis of m-Al(2)O(3) yields boehmite at pH = 4 and bayerite at pH = 11. The effect of ultrasound on the textural properties of mesoporous alumina as well as on the transformation of nanosized bayerite to boehmite can be consistently attributed to the transient strong heating of the liquid shell surrounding the cavitation bubble which caused the chemical processes similar to those occurred during hydrothermal treatment.