Neutron diffraction studies of Gd2Zr2O7 pyrochlore

The structure of Gd₂Zr₂O₇ pyrochlore over the temperature range 4-300 K has been refined from powder neutron diffraction data. The sample was enriched in ¹⁶⁰Gd to avoid the high neutron absorption of naturally occurring Gd. The diffraction pattern showed well resolved superlattice reflections indicative of the pyrochlore structure and no evidence is found for anion-disorder from the structural refinements.     

Pyridin-2-yl guanidine derivatives: conformational control induced by intramolecular hydrogen-bonding interactions

The synthesis and conformational analysis of a series of pyridin-2-yl guanidine derivatives using NMR, X-ray crystallography, and B3LYP/6-31+G** theoretical studies are reported. A remarkable difference was observed in the (1)H NMR spectra of the guanidinium salts as compared with their N,N'-di-Boc protected and neutral analogues. This difference corresponds to a 180° change in the dihedral angle between the guanidine/ium moiety and the pyridine ring in the salts as compared to the Boc-protected derivatives, a conclusion that was supported by theoretical studies, X-ray data, and NMR analysis. Moreover, our data sustain the existence of two intramolecular hydrogen-bonding systems: (i) between the pyridine N1 atom and the guanidinium protons in the salts and (ii) within the tert-butyl carbamate groups of the Boc-protected derivatives. To verify that the observed conformational control arises from these intramolecular interactions, a new series of N-Boc-N'-propyl-substituted pyridin-2-yl guanidines were also prepared and studied.     

Pipette-tip selective extraction of glycoproteins with lectin modified gold nano-particles on a polymer monolithic phase

The in situ preparation of ethylene dimethacrylate porous polymer monoliths within 20 μL polypropylene pipette tips, bound via surface grafted methacrylate anchor sites, is reported. Gold nano-particles (AuNPs) were immobilised onto the monolith pore surface utilising azlactone chemistry and coverage verified using field emission scanning electron microscopy. Erythrina cristagalli lectin (ECL) was immobilised upon the attached AuNPs via a bio-functional linker. The ECL-modified tip was successfully applied for the enrichment of galactosylated protein (desialylated transferrin) versus a non-galactosylated protein (ribonuclease B) due to the specificity of ECL. Reversed-phase capillary HPLC was used to validate the efficiency and selectivity of the developed micro-extraction phase which resulted in an increase in extraction recovery of ～95% due to the AuNP enhanced surface area. Further specificity of the ECL-modified tip was demonstrated with a complex mixture of non-glycosylated and glycosylated proteins with differing terminal sugar structures. Finally, the lectin affinity phase was applied to a galactosylated glycoproteins spiked Escherichia coli cell lysate to successfully demonstrate matrix tolerance.     

The acoustic and visual factors influencing the construction of tranquil space in urban and rural environments tranquil spaces-quiet places?

Prior to this work no structured mechanism existed in the UK to evaluate the tranquillity of open spaces with respect to the characteristics of both acoustic and visual stimuli. This is largely due to the fact that within the context of "tranquil" environments, little is known about the interaction of the audio-visual modalities and how they combine to lead to the perception of tranquillity. This paper presents the findings of a study in which visual and acoustic data, captured from 11 English rural and urban landscapes, were used by 44 volunteers to make subjective assessments of both their perceived tranquillity of a location, and the loudness of five generic soundscape components. The results were then analyzed alongside objective measurements taken in the laboratory. It was found that the maximum sound pressure level (L(Amax)) and the percentage of natural features present at a location were the key factors influencing tranquillity. Engineering formulas for the tranquillity as a function of the noise level and proportion of the natural features are proposed.     

A Heterometallic Porphyrin Dimer as a Potential Quantum Gate: Magneto-Structural Correlations and Spin Coherence Properties

In the development of two-qubit quantum gates, precise control over the intramolecular spin-spin interaction between molecular spin units plays a pivotal role. A weak but measurable exchange coupling is especially important for achieving selective spin addressability that allows controlled manipulation of the computational basis states |00⟩ |01⟩ |10⟩ |11⟩ by microwave pulses. Here, we report the synthesis and Electron Paramagnetic Resonance (EPR) study of a heterometallic meso-meso (m-m) singly-linked V^IVO−Cu^II porphyrin dimer. X-band continuous wave EPR measurements in frozen solutions suggest a ferromagnetic exchange coupling of ca. 8 ⋅ 10⁻³ cm⁻¹. This estimation is supported by Density Functional Theory calculations, which also allow disentangling the ferro- and antiferromagnetic contributions to the exchange. Pulsed EPR experiments show that the dimer maintains relaxation times similar to the monometallic Cu^II porphyrins. The addressability of the two individual spins is made possible by the different g -tensors of V^IV and Cu^II-ions, in contrast to homometallic dimers where tilting of the porphyrin planes plays a key role. Therefore, single-spin addressability in the heterometallic dimer can be maintained even with small tilting angles, as expected when deposited on surface, unlocking the full potential of molecular quantum gates for practical applications.     

Phase Transition-Promoted Rapid Photomechanical Motions of Single Crystals of a Triene Coordination Polymer

Molecular crystals with the ability to transform light energy into macroscopic mechanical motions are a promising class of materials with potential applications in actuating and photonic devices. In regard to such materials, coordination polymers that exhibit dynamic photomechanical motion, associated with a phase transition, are unknown. Herein, we report an intriguing photoactive, one-dimensional Zn^II coordination polymer, 1 , derived from 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and 3,5-difluorobenzoate. Single crystals of 1 under UV light irradiation exhibit rapid shrinking and bending, violent bursting-jumping, splitting, and cracking behavior. Single-crystal X-ray diffraction analysis and ¹H NMR spectroscopy reveal an unusual photoinduced phase transition involving a single-crystal-to-single-crystal [2+2] cycloaddition reaction that results in photomechanical responses. Interestingly, crystals of 1 , which are triclinic with space group , are transformed into a higher symmetry, monoclinic cell with space group C2/c. This process represents a rare example of symmetry enhancement upon photoirradiation. The photomechanical activity is likely due to the sudden release of stress associated with strained molecular geometries and significant solid-state molecular movement arising from cleavage and formation of chemical bonds. A composite membrane fabricated from 1 and polyvinyl alcohol (PVA) also displays interesting photomechanical behavior under UV light illumination, indicating the material's potential as a photoactuator.     

Photopolymerization-Driven Macroscopic Mechanical Motions of a Composite Film Containing a Vinyl Coordination Polymer

We report a unique vinyl coordination polymer (CP), [Zn(4-Fb)₂(tkpvb)]_n ( 1 , 4-HFb=4-fluorobenzoic acid, tkpvb=1,2,4,5-tetrakis(4-pyridylvinyl)benzene) that undergoes a rare photopolymerization reaction to form a two-dimensional CP integrated with a one-dimensional linear organic polymer. Upon light irradiation at different wavelengths, 1 exhibits an unprecedented phenomenon of photoinduced nonlinear lattice expansion. 1 can be uniformly dispersed in polyvinyl alcohol (PVA) to form the composite film of 1-PVA . When this film is exposed to UV light, internal minute stresses within crystallites are released by lattice expansion, resulting in a variety of photopolymerization-driven macroscopic mechanical motions. The findings provide new insights into the conversion of small lattice expansions of CPs into macroscopic mechanical motions based on photopolymerization reactions, which can promote the development of CPs-based smart photoactuators in the burgeoning field of microrobotics.