We report the anisotropic terahertz response of oxalic acid and sucrose crystals in the 0.2–3.0 THz range using terahertz time domain spectroscopy on large, single crystals. We compare the observed ...anisotropic response with the response calculated using solid-state density functional theory and find good agreement in the orientation dependence and relative intensities of the crystal phonons. It was found that oxalic dihydrate can be reversibly converted to anhydrous by controlled relative humidity. In addition, oxalic acid was found to have a large birefringence with Δn = 0.3, suggesting the material may be useful for terahertz polarization manipulation. Sucrose has a smaller birefringence of Δn = 0.05, similar to that of x-cut quartz. The anisotropic measurements provide both mode separation and symmetry determination to more readily achieve mode assignment for the more complex sucrose spectrum.
In the paper by Kamiński et al. J. Appl. Cryst. (2014), 47, 17651768, Jason B. Benedict is missing from the list of authors. The complete list of authors should be Radosław Kamiński, Jason B. ...Benedict, Gary Nottingham and Philip Coppens.
2D molecular entities build next-generation electronic devices, where abundant elements of organic molecules are attractive due to the modern synthetic and stimuli control through chemical, ...conformational, and electronic modifications in electronics. Despite its promising potential, the insufficient control over charge states and electronic stabilities must be overcome in molecular electronic devices. Here, we show the reversible switching of modulated charge states in an exfoliatable 2D-layered molecular conductor based on bis(ethylenedithio)tetrathiafulvalene molecular dimers. The multiple stimuli application of cooling rate, current, voltage, and laser irradiation in a concurrent manner facilitates the controllable manipulation of charge crystal, glass, liquid, and metal phases. The four orders of magnitude switching of electric resistance are triggered by stimuli-responsive charge distribution among molecular dimers. The tunable charge transport in 2D molecular conductors reveals the kinetic process of charge configurations under stimuli, promising to add electric functions in molecular circuitry.
A series of novel nonlinear optical (NLO) chromophores 1−4 incorporating the ferrocenyl (Fc) group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran (TCF) derivatives as ...electron acceptors are presented. The use of a constant Fc donor and varied acceptors and bridges makes it possible to systematically determine the contribution of the conjugated bridge and the acceptor strength to chromophore nonlinear optical activity. The X-ray crystal structures of all four chromophores allow for the systematic investigation of the structure−property relationship for this class of molecules. For example, the crystal structures reveal that both cyclopentadienyl groups in the ferrocenyl donor contribute to the electron donating ability. The first-order hyperpolarizabilities β of these chromophores, measured by hyper-Rayleigh scattering (HRS) relative to p-nitroaniline are reported. These β values are compared to those calculated by density functional theory (DFT). The excellent agreement between the theoretical and experimental β values demonstrates that a linear relation exists between the hyperpolarizability and the bond length alternation. An electrooptic coefficient, r 33, of ∼25 pm/V at 1300 nm, for compound 4, incorporated into a polymer matrix, is competitive with organic chromophores. Moreover, this r 33 is more than 30 times larger than the previously reported value for an organometallic chromophore in a poled polymer matrix. This work not only underscores the potential for Fc donor moieties, which have been underutilized, but also demonstrates that experimental characterization and theoretical simulations are now congruent, viable methods for assessing potential performance of NLO materials.
FeII, CoII and NiII complexes of two tetraazamacrocycles (1,4,8,11‐tetrakis(carbamoylmethyl)‐1,4,8,11‐tetraazacyclotetradecane (L1) and ...1,4,7,10‐tetrakis(carbamoylmethyl)‐1,4,7,10‐tetraazacyclododecane (L2) show promise as paraCEST agents for registration of temperature (paraCEST=paramagnetic chemical exchange saturation transfer). The FeII, CoII and NiII complexes of L1 show up to four CEST peaks shifted ≤112 ppm, whereas analogous complexes of L2 show only a single CEST peak at ≤69 ppm. Comparison of the temperature coefficients (CT) of the CEST peaks of Co(L2)2+, Fe(L2)2+, Ni(L1)2+ and Co(L1)2+ showed that a CEST peak of Co(L1)2+ gave the largest CT (−0.66 ppm oC−1 at 4.7 T). NMR spectral and CEST properties of these complexes correspond to coordination complex symmetry as shown by structural data. The Ni(L1)2+ and Co(L1)2+ complexes have a six‐coordinate metal ion bound to the 1‐, 4‐amide oxygen atoms and four nitrogen atoms of the tetraazamacrocycle. The Fe(L2)2+ complex has an unusual eight‐coordinate FeII bound to four amide oxygen atoms and four macrocyclic nitrogen atoms. For Co(L2)2+, one structure has seven‐coordinate CoII with three bound amide pendents and a second structure has a six‐coordinate CoII with two bound amide pendents.
Changes in coordination affect MRI contrast: The remarkably different chemical exchange saturation transfer (CEST) spectra of CoII, FeII or NiII complexes of amide‐appended macrocycles is based on the different coordination geometries for complexes of the two ligands. The complexes with the most highly shifted CEST peaks show promise for the development as magnetic resonance imaging (MRI) temperature probes for thermometry.
The two review articles nicely summarize the evolution of structure-based research involving Photoactive Yellow Protein and the critical role of microfluidics in the crystallization and structure ...determination of proteins. Sui and Perry: Review of microfluidic technologies applied to protein crystal growth and sample delivery in serial crystallography experiments.
Understanding guest exchange processes in metal–organic frameworks is an important step toward the rational design of functional materials with tailor-made properties. The dehydration of the flexible ...metal-organic framework Co(AIP)(bpy)0.5(H2O)•2H2O was studied by novel in situ dynamic x-ray diffraction techniques. The complex mechanism of dehydration, along with the as-yet unreported metastable structures, was determined. The structural information obtained by the application of these techniques helps to elucidate the important guest–host interactions involved in shaping the structural landscape of the framework lattice and to highlight the importance of utilizing this technique in the characterization of functional framework materials.
The temperature dependence of the luminescent lifetime of a single crystal of Cu(I) phenanthroline, Cu(dmp)(PPh3)2BF4 (dmp=2,9-dimethyl-1,10-phenanthroline and PPh3=triphenylphosphine), was measured ...using a fluorescence lifetime imaging microscope utilizing time-gated CCD detection. At all temperatures between 100K and 292K, the single crystals exhibited biexponential luminescent decay as well as non-linear Arrhenius luminescent decay kinetics. Variable temperature single-crystal XRD measurements revealed that the observed behavior is likely not the result of a crystallographic phase transition.
21,23-Ditelluraporphyrins 3, 9, and 16−18 bearing phenyl, 4-methoxyphenyl, and/or 3,4,5-trimethoxyphenyl meso substituents were prepared by the condensation of 2,5-dihydroxy(aryl)methyltellurophenes ...12 with 2,5-di2-pyrrolo(aryl)methyltellurophenes 15 in the presence of BF3−etherate followed by oxidation with p-chloranil. Compounds 15 were prepared from tellurophenes 12 with pyrrole and BF3−etherate. Tellurophenes 12 were prepared in 44−72% isolated yield by the addition of 1,6-diarylhexa-2,4-diyn-1,6-diols 13 to the reduction product of Te powder and LiBHEt3. No additional Lewis acid was necessary in these reactions. Coupling of 1-aryl-2-propyn-1-ols (14) with CuCl, pyridine, and air in MeOH gave diyndiols 13. 26,28-Ditellurasapphyrin 10 was isolated in 0.6% yield from the reaction mixture that produced 9 in 12% isolated yield. The X-ray structure of 10 showed a nearly planar sapphyrin core with the Te atoms of both tellurophene rings pointing to the center of the core. 30,33-Ditellurarubyrin 11 was isolated in 32% yield by the reaction of two equivalents of trifluoroacetic acid with tellurophene dipyrrane 15c. 125Te NMR spectra were recorded for the compounds of this study.
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