Electronic structure and second-order nonlinear optical properties of lemniscular [16]cycloparaphenylene compounds.

Chiral organic compounds are excellent second-order nonlinear optical (NLO) materials due to their inherent non-symmetric electronic structures combined with the advantages of organic compounds. At present, density functional theory (DFT) has become a powerful tool for predicting the properties of novel materials. In this paper, based on chiral lemniscular [16]cycloparaphenylene, three novel compounds are designed by introduction of donor/acceptor units and their combinations. The geometrical/electronic structure, electronic absorption, and the second-order NLO properties of these compounds have been systematically investigated by DFT/TDDFT theory. The simulated UV-Vis/CD spectra of compound 1 are in good agreement with the experimental ones, enabling us to assign their electronic transition characteristics and absolute configuration with high confidence. The investigations show that energy gaps, absorption wavelength and second-order NLO response may be effectively tuned by the introduction of the donor or acceptor units or their combinations. For instance, the second-order NLO value of compound 4 is about 207 times as large as the average second-order polarizability of the organic molecule urea. Thus, the studied compounds are expected to be potential large second-order NLO materials.

Theoretical study on the electronic structure and second-order nonlinear optical properties of benzannulated or selenophene-annulated expanded helicenes.

Currently, discovering new materials with superior second-order nonlinear optical (NLO) performance has become a very hot research topic in the fields of chemistry and materials science. Now, density functional theory (DFT) has become a powerful tool to predict the performance of novel materials. In this paper, based on benzannulated and selenophene-annulated expanded helicenes, twenty-six helicenes are designed by introduction donor/acceptor moieties and their combinations at different substituent positions. The geometrical/electronic structures, electronic transition, and second-order NLO properties of these helicenes are full investigated by DFT/TDDFT theory. The investigations show that these helicenes have large first hyperpolarizability values (ß HRS). For instance, the ß HRS value (29.95 × 10-30 esu) of helicene H24 is about 7 times larger than that of the highly π-delocalized phenyliminomethyl ferrocene complex. In addition, the introduction of acceptor NO2 unit at R7 and R8 positions for helicenes H1 and H15 can obtain the largest ß HRS value, which is attributed to the enhancement of electron acceptor ability. In view of large NLO response and intrinsic asymmetric structures, the studied helicenes have the possibility to be excellent second-order NLO materials.

[Effects and mechanism of hypoxia exposure on related genes in brown fat tissue of obese mice based on mRNA expression profile microarray].

OBJECTIVE: This study intended to screen differentially expressed genes and pathways in Brown Adipose Tissue (BAT) of obese mice after the intervention of hypoxia by mRNA expression profile microarray, exploring the mechanism of hypoxia activated BAT. METHODS: Thirty C57BL/6J male mice were divided into the normal diet control group (N, n=8), high-fat diet control group (OB, n=8) and high-fat diet hypoxia group (H, n=8). Group H was intervened by hypoxia exposure in the oxygen concentration of 11.2% of the normal oxygen and hypoxia for 8 h/d, 6 d/w of 4 weeks. Blood lipid and blood glucose were detected after intervention; RNA microarray scan and bioinformation analysis were done of BAT from scapula. Genes significantly (P ≤ 0.05) regulated more than 1.5 fold were chosen to do Gene Ontology and enrichment analysis by KOBAS 2.0, and confirmation of genes participating in key biological process (BP) and pathway was done by real time qPCR. RESULTS: After intervention, the body weight and blood lipid and glucose levels in group H were significantly lower than those of group OB. Comparing with group N, 802 genes were significantly up-regulated and 1 175genes were down-regulated. The BP of these genes mainly concerned with glucose and lipid metabolic process and inflammatory reaction. Comparing with group OB, 297 genes were significantly up-regulated and 228 genes were down-regulated. These genes participated in glucose and lipid metabolic process, lipid transport, muscle system process and cardiovascular system development. The pathways of regulating BAT by hypoxia exposure mainly concentrated on the HIF-1, PI3K-AKT, FoxO and ErbB signaling pathways. CONCLUSIONS: A series of genes and pathways in BAT could be adjusted by hypoxia exposure, so that hypoxia could improve the activity of BAT, promoting obese organism to lose weight.

Application of classical models of chirality to optical rectification.

Classical models of chirality are used to investigate the optical rectification effect in chiral molecular media. Calculation of the zero frequency first hyperpolarizabilities of chiral molecules with different structures is performed and applied to the derivation of a dc electric-dipole polarization. The expression of second-order nonlinear static-electric-dipole susceptibilities is obtained by theoretical derivation in the isotropic chiral thin films. The microscopic mechanism producing optical rectification is analyzed in view of this calculation. We find that optical rectification is derived from interaction between the electric field gradient (spatial dispersion) and chiral molecules in optically active liquids and solution by our calculation, which is consistent with the result given by Wozniak and Wagniere [Opt. Commun. 114, 131 (1995)]: The optical rectification depends on the fourth-order electric-dipole susceptibilities.

Optical rectification at isotropic chiral film composed of tripod-like molecules.

In the paper, the three-coupled-oscillator model presented by us is used to study the optical rectification in isotropic chiral films. The zero frequency hyperpolarizabilities of chiral molecules with a tripod-like structure are calculated. The expressions of the static-electric polarization and the relations between the optical rectification and the microscopic parameters of chiral medium are obtained by theoretical derivation. Furthermore, the relations of the dc electric-dipole polarization with the wavelength of incident light and microscopic parameters of chiral molecules have been simulated numerically.