Heteroatom-bridged heterofluorenes: a theoretical study on molecular structures and optoelectronic properties.

Heteroatom incorporation is highly effective in tuning the molecular structures and optoelectronic properties of conjugated organic molecules. Here, we performed systematic theoretical studies on heteroatom-bridged heterofluorenes (BXFs) constructed by double heteroatom bridges of biphenyl to reveal the effects of heavily incorporated heteroatoms on molecular architecture and π-conjugation for different optoelectronic properties. Nine novel BXFs in three series were investigated and all of them exhibit promising potential optoelectronic properties owing to their highly fused molecular structure with heavy π-conjugation, although the introduction of different types and numbers of heteroatoms will lead to varied properties. Moreover, spiropolymers of BSiF and BGeF polymerized at the bridging position were also designed for the first time and found to have attractive optoelectronic properties of poly(BXF)s inherited from their monomers, demonstrating further the effectiveness of the bis-heteroatom introduction strategy in the construction of high-performance optoelectronic polymers. This heteroatom introduction strategy in constructing highly rigid π-conjugated materials could be applicable to other systems, representing a new concept advance to design novel conjugated small molecules and polymers for high-performance optoelectronic applications.

Walnut Polyphenol Extract Protects against Fenitrothion-Induced Immunotoxicity in Murine Splenic Lymphocytes.

Fenitrothion (FNT), an organophosphate pesticide, exerts an immunotoxic effect on splenocytes. Dietary polyphenol compounds exert antioxidant, anticancer and antihypertensive effects. In this study, we investigated the effect of walnut polyphenol extract (WPE) on FNT-induced immunotoxicity in splenic lymphocytes in vitro. Treatment with WPE significantly increased the proliferation of FNT-exposed splenocytes, as evidenced by increases in the proportions of splenic T lymphocytes (CD3⁺ T cells) and T-cell subsets (CD8⁺ T cells), as well as the secretion of the T-cell-related cytokines interleukin (IL)-2, interferon-γ, IL-4 and granzyme B. These effects were associated with a reduction in oxidative stress, as evidenced by changes in the levels of hydroxyl radical, superoxide dismutase, glutathione peroxidase and malondialdehyde. Moreover, WPE decreased the FNT-induced overexpression of NADPH oxidase 2 and dual oxidase 1 by regulating Toll-like receptor 4 signaling in splenic T-cells. Taken together, these findings suggest that WPE protects against FNT-mediated immunotoxicity and improves immune function by inhibiting oxidative stress.

Resonance-Activated Spin-Flipping for Efficient Organic Ultralong Room-Temperature Phosphorescence.

Triplet-excited-state-involved photonic and electronic properties have attracted tremendous attention for next-generation technologies. To populate triplet states, facile intersystem crossing (ISC) for efficient exciton spin-flipping is crucial, but it remains challenging in organic molecules free of heavy atoms. Here, a new strategy is proposed to enhance the ISC of purely organic optoelectronic molecules using heteroatom-mediated resonance structures capable of promoting spin-flipping at large singlet-triplet splitting energies with the aid of the fluctuation of the state energy and n-orbital component upon self-adaptive resonance variation. Combined experimental and theoretical investigations confirm the key contributions of the resonance variation to the profoundly promoted spin-flipping with ISC rate up to ≈107 s-1 in the rationally designed NPX (X = O or S) resonance molecules. Importantly, efficient organic ultralong room-temperature phosphorescence (OURTP) with simultaneously elongated lifetime and improved efficiency results overcoming the intrinsic competition between the OURTP lifetime and efficiency. With the spectacular resonance-activated OURTP molecules, time-resolved and color-coded quick response code devices with multiple information encryptions are realized, demonstrating the fundamental significance of this approach in boosting ISC dynamically for advanced optoelectronic applications.

Promoting Singlet/triplet Exciton Transformation in Organic Optoelectronic Molecules: Role of Excited State Transition Configuration.

Exciton transformation, a non-radiative process in changing the spin multiplicity of an exciton usually between singlet and triplet forms, has received much attention recently due to its crucial effects in manipulating optoelectronic properties for various applications. However, current understanding of exciton transformation mechanism does not extend far beyond a thermal equilibrium of two states with different multiplicity and it is a significant challenge to probe what exactly control the transformation between the highly active excited states. Here, based on the recent developments of three types of purely organic molecules capable of efficient spin-flipping, we perform ab initio structure/energy optimization and similarity/overlap extent analysis to theoretically explore the critical factors in controlling the transformation process of the excited states. The results suggest that the states having close energy levels and similar exciton characteristics with same transition configurations and high heteroatom participation are prone to facilitating exciton transformation. A basic guideline towards the molecular design of purely organic materials with facile exciton transformation ability is also proposed. Our discovery highlights systematically the critical importance of vertical transition configuration of excited states in promoting the singlet/triplet exciton transformation, making a key step forward in excited state tuning of purely organic optoelectronic materials.

Controlling Intramolecular Conformation through Nonbonding Interaction for Soft-Conjugated Materials: Molecular Design and Optoelectronic Properties.

To address the intrinsic contradiction between high optoelectronic properties and good processability in organic π-conjugated molecules, we propose that soft-conjugated molecules (SCMs), conformationally locked by intramolecular nonbonding interactions, can benefit from both nonplanar molecular structures in solution for processing and rigid coplanar structures in the solid state for enhanced optoelectronic properties. Computational results reveal that nonbonding pairs of S···N, N···H, and F···S are strong enough to prevail over thermal fluctuations, steric effects, and other repulsive interactions to force the adjacent aromatic rings to be planar; thus, constructed SCMs display delocalized frontier molecular orbitals with frontier orbital energy levels, band gaps, reorganization energies, and photophyscial properties comparable to those of rigid-conjugated molecules because of their stable planar soft-conjugation at both ground and excited states. The understanding gained from the theoretical investigations of SCMs provides keen insights into construction and modification of soft-conjugations to harmonize the optoelectronic property and processability in conjugated molecules for advanced optoelectronic applications.

In vitro effect of 4-pentylphenol and 3-methyl-4-nitrophenol on murine splenic lymphocyte populations and cytokine/granzyme production.

Gasoline exhaust particles (GEP) and diesel exhaust particles (DEP) are considered to be some of the most important air pollutants. Among the many constituents in these pollutant particles, 4-pentylphenol (PP) and 3-methyl-4-nitrophenol (PNMC) are considered important phenolics in GEP and DEP, respectively. The aim of this study was to investigate the effect of in vitro exposure to commercially-supplied PP and PNMC on populations of, and production of interleukin (IL)-2, IL-4 and granzyme-B by, mouse splenic lymphocytes. After in vitro exposure to PP or PNMC for 48 h, splenocyte viability was measured, cell phenotypes, e.g. B-cell (CD19), T-cells (CD3), T-cell subsets (CD4 and CD8), were quantified by flow cytometry and production of IL-2, IL-4 and granzyme-B was assessed via ELISA. The oxidative toxicity of PP and PNMC toward the splenocytes was also evaluated using measures of hydroxyl radical and malondiadehyde production and changes in glutathione peroxidase and superoxide dismutase activities. Results showed that in vitro exposure to PP and PNMC inhibited splenic cell parameters in a dose-related manner. Exposure to PP and PNMC decreased splenic T-lymphocyte populations and splenocyte production of cytokines and granzyme B, as well as induced oxidative stress in the splenocytes. The results also showed that the percentages of CD3(+) T-cells overall and of CD4(+) and CD8(+) T-cells therein, among exposed splenocytes, were reduced; neither compound appeared to affect levels of CD19(+) B-cells. Overall, the suppressive effects of PP were stronger than PNMC. The data here provide support for the proposal that PP-/PNMC-induced toxicity in splenocytes may be due at least in part to oxidative damage and that PP and PNMC - as components of GEP and DEP - might significantly impact on splenic T-cell formation/release of cytokines/granzymes in situ.