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Planarity of cis - and trans -3-chlorostyrene is discussed in the light of new data from infrared/Raman and inelastic neutron scattering ( INS ) spectroscopies and theoretical calculations. Molecular structures have been optimized at different levels of theory, ab initio and DFT, with an assortment of basis sets, 6-31G*, 6-311G** and 6-311++G** concluding that Hartree–Fock and MP2 results predict a non-planar structure while DFT predicts a planar geometry regardless of the basis set. Vibrational spectra have been calculated and compared with experimental data as obtained from IR , Raman and, for the first time, Inelastic Neutron Scattering ( INS ) providing evidence for the planarity of this system in its ground electronic state. Molecular force fields for the cis and trans conformers of 3-chlorostyrene using the scaled and refinement formalisms are reported. For easier visualisation the valence force constants have also been converted to a so-called pure vibrational force field. These results together with the barrier height calculations to vinyl internal rotation allows conclusions about the extent of localisation of the vinyl double bond.

SnO 2 and Mn-doped SnO 2 single-phase tetragonal crystal structure quantum dots (QDs) of uniform size with control over dopant composition and microstructure were synthesized using the high pressure microwave synthesis technique. On a broader vision, we systematically investigated the influence of dilute Mn ions in SnO 2 under the strong quantum confinement regime through various experimental techniques and density functional theoretical (DFT) calculations to disclose the physical mechanism governing the observed ferromagnetism. DFT calculations revealed that the formation of the stable (001) surface was much more energetically favorable than that of the (100) surface, and the formation energy of the oxygen vacancies in the stable (001) surface was comparatively higher in the undoped SnO 2 QDs. X-ray photoelectron spectroscopy (XPS) and first-principles modeling of doped QDs revealed that the lower doping concentration of Mn favored the formation of MnO-like (Mn 2+ ) structures in defect-rich areas and the higher doping concentration of Mn led to the formation of multiple configurations of Mn (Mn 2+ and Mn 3+ ) in the stable surfaces of SnO 2 QDs. Electronic absorption spectra indicated the characteristic spin allowed ligand field transitions of Mn 2+ and Mn 3+ and the red shift in the band gap. DFT calculations clearly indicated that only the substitutional dopant antiferromagnetic configurations were more energetically favorable. The gradual increase of magnetization at a low level of Mn-doping could be explained by the prevalence of antiferromagnetic manganese-vacancy pairs. Higher concentrations of Mn led to the appearance of ferromagnetic interactions between manganese and oxygen vacancies. The increase in the concentration of metallic dopants caused not just an increase in the total magnetic moment of the system but also changed the magnetic interactions between the magnetic moments on the metal ions and oxygen. The present study provides new insight into the fundamental understanding of the origin of ferromagnetism in transition metal-doped QDs.

Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc 2 S@C n have similar cage geometries from C 70 to C 84 and form a close-knit family of structures related by Endo–Kroto insertion/extrusion of C 2 units and Stone–Wales isomerization transformations. The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations, have implications for the formation of metallofullerenes, and will aid structural identification from within the combinatorially vast pool of conceivable isomers.

Recent experimental data point to an asymmetric ground-state electronic distribution in the special pair (P) of purple bacterial reaction centers, which acts as the primary electron donor in photosynthesis. We have performed a density functional theory investigation on an extended model including the bacteriochlorophyll dimer and a few relevant surrounding residues to explore the origin of this asymmetry. We find strong evidence that the ground-state electron density in P is intrinsically asymmetric due to protein -induced distortions of the porphyrin rings, with excess electron charge on the P M bacteriochlorophyll cofactor . Moreover, the electron charge asymmetry is strongly modulated by the specific orientation of the C3 1 acetyl group, which is hydrogen bonded to His168. The electronic excitation has a significant charge transfer character inducing a displacement of electron charge from P L to P M , in agreement with experimental data in the excited state. These results are relevant for the understanding of the unidirectional electron transfer path in photosynthesis.

Changes in the local structure and magnetic properties at Fe sites due to defects were addressed in a detailed manner in Co 2 FeAl by 57 Fe M?ssbauer spectroscopy. Based on the systematic correlation of these results a comprehensive understanding of the defects and hence of the different types of disordering that occur in Co 2 FeAl subjected to different non-equilibrium treatments have been obtained in this study. As high as 35% of the Fe atoms were deduced to be associated with the A2 type of disordering in Co 2 FeAl, which provides a basic understanding of the observed much lower value of spin polarization as observed in this system against the high value predicted theoretically. Also this study revealed a striking linear correlation between the valence electron concentration and the effective magnetic hyperfine fields as deduced at different sites of occupation of 57 Fe atoms.

A 1D organic redox-active material is combined with another 1D conductive material for rechargeable batteries. Poly(vinyl carbazole) (or PVK) and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (or PEDOT:PSS) are used as the redox-active and conductive 1D materials, respectively. Due to their extremely anisotropic geometry, the two polymers are expected to be inter-tangled with each other, showing a kinetically ideal model system in which each redox-active moiety of PVK is supposed to be directly connected with the conducting pathways of PEDOT:PSS. In addition to its role as a conductive agent providing kinetic benefits, PEDOT:PSS works as an efficient binder that guarantees enhanced electrochemical performances with only a tenth of the amount of a conventional binder (polyvinylidene fluoride or PVdF). The benefit of gravimetric energy density gain obtained using the conductive binder comes mainly from efficient spatial coverage of binding volume due to the low density of PEDOT:PSS. Towards realizing flexible all-polymer batteries, a quasi-all-polymer battery half-cell is designed using the PVK/PEDOT:PSS composite with a polymer gel electrolyte.

Aggregation kinetics and gel formation in aqueous suspensions that undergo heteroaggregation are studied by means of Brownian dynamics simulations. The simulated system, described in a previous paper [M. A. Piechowiak, A. Videcoq, F. Rossignol, C. Pagnoux, C. Carrion, M. Cerbelaud, R. Ferrando, Langmuir , 2010, 26 (15), 12540–12547.], is constituted of two kinds of synthesized, almost equally sized colloids: silica particles that are negatively charged and alumina-coated silica particles that are positively charged. The interactions between colloids are modeled by the DLVO potential. Several compositions are analyzed, from silica-rich to alumina-rich cases. The particle volume fraction ? is varied in the range 6–12%. The study of the aggregation kinetics allows us to clarify the effect of those variations on the clustering process. Gelation is analyzed by detection of spanning clusters in each x -, y -, z -direction of the cubic simulation box. Percolating networks start to be observed from ? = 7%, a low value of the volume fraction close to the solid volume fraction experimentally measured in sediments of those suspensions.

Spontaneously emerged supramolecular chirality and chiral symmetry breaking from achiral/racemic constituents remain poorly understood. We here report that supramolecular chirality may emerge from the structural flexibility of achiral aryl nitrogen centres which provide instantaneous chirality. Employing a naphthalimide–cyanostilbene dyad as a model, we explored the underlying mechanism of aggregation-induced chiral symmetry breaking and found that the conformations of the N -naphthylpiperazine and the N , N -dimethylaniline units facilitate the formation of ordered supramolecular structures and offer opposite handedness. Furthermore, chiral symmetry breaking of the monomers was amplified by the formation of dimers. The microscopic and the macroscopic observations from the theoretical simulations and experimental measurements are thus rationalized by connecting the population of the dihedral angles of the aryl nitrogen centres, the morphology of the self-assemblies, and the observed circular dichroism spectra.

The concept of aggregation-induced emission represents a means to rationalise photoluminescence of usually nonfluorescent excimers in solid-state materials. In this publication, we study the photophysical properties of selected diaminodicyanoquinone (DADQ) derivatives in the solid state using a combined approach of experiment and theory. DADQs are a class of high-dipole organic chromophores promising for applications in non-linear optics and light-harvesting devices. Among the compounds investigated, we find both aggregation-induced emission and aggregation-caused quenching effects rationalised by calculated energy transfer rates. Analysis of fluorescence spectra and lifetime measurements provide the interesting result that (at least) two emissive species seem to contribute to the photophysical properties of DADQs. The main emission peak is notably broadened in the long-wavelength limit and exhibits a blue-shifted shoulder. We employ high-level quantum-chemical methods to validate a molecular approach to a solid-state problem and show that the complex emission features of DADQs can be attributed to a combination of H-type aggregates, monomers, and crystal structure defects.

Thermal quenching seriously restricts the practical application of phosphors, particularly under high temperature and long-term working conditions. Here, we demonstrate that the as-obtained series of solid solutions of Ca 2? x Y x Al 2 Si 1? x Al x O 7 :Tb 3+ ( x = 0–1, Ca 2 Al 2 SiO 7 → CaYAl 3 O 7 ) phosphors exhibit an adjustable optical performance, where CaYAl 3 O 7 :Tb 3+ exhibits a greatly improved thermal stability with a shortened bond distance of the related polyhedron compared with Ca 2 Al 2 SiO 7 :Tb 3+ . The shrunken bond distance strengthens the pressure of the local structure and suppresses the non-radiative transition effectively, contributing to the prevention of the thermal degradation. The formed phosphor with excellent structural stability could be effectively incorporated with various lanthanide ions (Eu 3+ , Tb 3+ , Sm 3+ , Dy 3+ , and Pr 3+ ) to address a pleochroism output.