Facile Fabrication of Nanorod‐Assembled Fluorine‐Substituted Hydroxyapatite (FHA) Microspheres

Nanorod‐assembled FHA microspheres with different F contents were for the first time prepared through a facile one‐step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self‐assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self‐assembled into sphere‐like sturctures at high pH conditions and rod‐like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca²⁺ release kinetics from EDTA‐Ca‐Na₂ at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self‐assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability.     

α- or β-Substituted functional phthalocyanines bearing thiophen-3-ylmethanol substituents: synthesis,characterization, aggregation behavior and antioxidant activity

The tetra α- or β-thiophene substituted metal and metal-free phthalocyanines (Pcs) M[Pc(α-OCH₂Thiopen)₄] and M[Pc(β-OCH₂Thiopen)₄] {(α-ThMet-MPc), (β-ThMet-MPc) [ThMet: Thiophene methoxy], M = Zn(II), Co(II) and, 2H} were synthesized from the corresponding 3’-(thiophen-3-ylmethoxy)phthalonitrile or 4’-(thiophen-3-ylmethoxy)phthalonitrile (ThMePN). The structural characterization, spectral, and antioxidant properties of a series of new Pcs were also presented. Both α- and β-substituted Pc complexes increased solubility in polar solvents, such as THF, DMF, and DMSO. FT-IR, ¹H-NMR, ¹³C-NMR, UV–vis, MALDI-TOF/MS spectral, and elemental analysis data were used to characterize the compounds. The aggregation behaviors of 3–8 were also investigated at different concentrations in THF. Antioxidant test methods, α,α-diphenyl-β-picrylhydrazyl radical scavenging activity, metal chelating activity, and reducing power, were used to determine the antioxidant activities. 6 showed very good ferrous ion chelating activity of 81 ± 1%. 6, 5, 4, and 3 showed better reducing power than trolox, ascorbic, acid and butylated hydroxytoluene, commercially used antioxidants.     

Organocatalytic Enantioselective Synthesis of Chiral Diarylmethylamines from Racemic Alcohols

An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethylamines is described. Different from the previously reported elegant “borrowing hydrogen” approach, the present process employs a distinct complementary formal S_N1 strategy. This approach enjoys excellent enantioselectivity, mild conditions, broad scope, and easy product derivatization. Mechanistically, control experiments also provided important insights into some notable features, such as substrate kinetic resolution and reversibility as well as the critical role of the ortho‐ hydroxy group in the substrate.     

Side chain effect on photovoltaic properties of dibenzo[a,c]phenazine based donor–acceptor polymers

The electron–donor polymers containing dibenzo[a,c]phenazine (BPz) derivatives with 2,7-alkyl and 11,12-alkoxy substituted, PBDT-BPzC and PBDT-OBPz, respectively, were synthesized to investigate the photovoltaic effect of different side chain substitutions. The polymers exhibit similar physical properties, except the HOMO and LUMO of PBDT-BPzC are 0.18 and 0.15 eV deeper than PBDT-OBPz, resulting in the V_oc of polymer solar cells (PSCs) based on PBDT-BPzC are above 0.1 V higher than that of PBDT-OBPz. With the contribution of the superior V_oc, polymer PBDT-BPzC showed preferable photovoltaic performances, and the PCE reached 4.44%, which is 0.49% higher than PBDT-OBPz. This research reveals a preferred side chain substituted way to modify BPz unit, and gives an optimally developing the dibenzo[a,c]phenazine derivatives based electron–donor polymers.     

Organic superalkalis with closed-shell structure and aromaticity

Benzene (C₆H₆) and polycyclic hydrocarbons such as naphthalene (C₁₀H₈), anthracene (C₁₄H₁₀) and coronene (C₂₄H₁₂) are well known aromatic organic compounds. We study the substitution of Li replacing all H-atoms in these hydrocarbons using density functional method. The vertical ionisation energy of such lithiated species, i.e. C₆Li₆, C₁₀Li₈, C₁₄Li₁₀ and C₂₄Li₁₂ ranges 4.24–4.50 eV, which is lower than the ionisation energy (IE) of Li atom. Thus, these species may behave as superalkalis due to their lower IE than alkali metal. However, these lithiated species possess planar and closed-shell structure, unlike typical superalkalis. Furthermore, all Li-substituted species are aromatic although their degree of aromaticity is reduced as compared to corresponding hydrocarbon analogues. We have further explored the structure of C₆Li₆ as star-like, unlike its inorganic analogue B₃N₃Li₆, which appears as fan-like structure. We have also demonstrated that the interaction of C₆Li₆ with a superhalogen (such as BF₄) is similar to that of a typical superalkali (such as OLi₃). This may further suggest that the proposed lithiated species may form a new class of closed-shell organic superalkalis with aromaticity.     

A tin-containing liquid crystalline polymer with two glass temperatures

A tin-containing liquid crystalline side group polymer was synthesized and characterized. Two glass transitions were detected by calorimetric investigations. The X-ray pattern corresponds to a smectic C order of the side groups and a disordered isotropic main chain. Dielectric measurements show two relaxation ranges which are influenced by the glass transitions and a fast local process. The low frequency mechanism can be related to the reorientation of the side groups and the higher glass transition temperature. The second is connected with the α-relaxation of the main chain and freezes in at lower temperatures.     

Lower bound for the ratios of eigenvalues of Schrödinger with nonpositive single‐barrier potentials

Horváth and Kiss (Proc. Amer. Math. Soc., 2005) proved the upper bound estimate for Dirichlet eigenvalue ratios of the Schrödinger problem ?y^′′ + q(x)y = λy with nonnegative and single‐well potential q. In this paper, we prove that if q(x) is a nonpositive, continuous, and single‐barrier potential, then for λ_n > λ_m≥ ? 2q^?, where . In particular, if q(x) satisfies the additional condition , then λ₁ > 0 and for n > m ≥ 1. For this result, we develop a new approach to study the monotonicity of the modified Prüfer angle function.