Theoretical investigation of fluorescence changes caused by methanol bridge based on ESIPT reaction

The different fluorescence behavior caused by the excited state proton transfer in 3-hydroxy-4-pyridylisoquinoline(2a)compound has been theoretically investigated.Our calculation results illustrate that the 2a monomer in tetrahydrofuran solvent would not occur proton transfer spontaneously,while the 2a complex in methanol(MeOH)solvent can undergo an asynchronous excited state intramolecular proton transfer(ESIPT)process.The result was confirmed by analyzing the related structural parameters,infrared vibration spectrum and reduced density gradient isosurfaces.Moreover,the potential curves revealed that with the bridging of single MeOH molecular the energy barrier of ESIPT was modulated effectively.It was distinctly reduced to 4.80 kcal/mol in 2a-MeOH complex from 25.01 kcal/mol in 2a monomer.Accordingly,the ESIPT process induced a fluorochromic phenomenon with the assistant of proton-bridge.The elucidation of the mechanism of solvent discoloration will contribute to the design and synthesis of fluorogenic dyes as environment-sensitive probes.

Theoretical study on the mechanism for the excited-state double proton transfer process of an asymmetric Schiff base ligand

Excited-state double proton transfer(ESDPT)in the 1-[(2-hydroxy-3-methoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol(HYDRAVH_(2))ligand was studied by the density functional theory and time-dependent density functional theory method.The analysis of frontier molecular orbitals,infrared spectra,and non-covalent interactions have crossvalidated that the asymmetric structure has an influence on the proton transfer,which makes the proton transfer ability of the two hydrogen protons different.The potential energy surfaces in both S_(0)and S_1 states were scanned with varying O-H bond lengths.The results of potential energy surface analysis adequately proved that the HYDRAVH_(2)can undergo the ESDPT process in the S_1 state and the double proton transfer process is a stepwise proton transfer mechanism.Our work can pave the way towards the design and synthesis of new molecules.

Free-standing Na_(2)C_(6)O_(6)/MXene composite paper for highperformance organic sodium-ion batteries

Sodium-ion batteries(SIBs)are regarded as the ideal low-cost choice for next-generation large-scale energy storage system.Carbonyl-based organic salt-disodium rhodizonate(Na_(2)C_(6)O_(6))with high theoretical specific capacity(501 mAh·g−1)is considered as a promising cathode material for SIBs.However,the dissolution of active material in electrolyte and low electronic conductivity lead to rapidly capacity decay and poor rate performance.Herein,a simple method is designed to construct free-standing and flexible Ti3C2Tx Na2C6O6/MXene paper via vacuum-assisted filtration and antisolvent approach.The MXene can form an electronic conductive network,adsorb the active materials,and offer additional active sites for Na storage.The binder-free Na_(2)C_(6)O_(6)/MXene paper delivers excellent electrochemical property with a high rate performance of 231 mAh·g−1 at 1,000 mA·g−1 and a high capacity of 215 mAh·g−1 after 100 cycles.This work provides an attractive strategy for designing high-performance organic electrode materials of SIBs.

CgVeA, a light signaling responsive regulator, is involved in regulation of chaetoglobosin A biosynthesis and conidia development in Chaetomium globosum

Cytochalasans,with diverse structures and pharmacological activities,are a class of compounds containing isoindolinone moieties fused to the tricyclic or tetracyclic ring system.Chaetoglobosin A(cheA),mainly produced by Chaetomium globosum,is the most abundant cytochalasan.However,limited understanding of transcriptional regulation of morphological development and cheA biosynthesis in C.globosum has hindered cheA application in agriculture and biomedical field.This study examined the regulatory role of CgVeA gene in C.globosum.CgVeA had significant effect on secondary metabolites production in C.globosum,similar to that reported in other filamentous fungi.Inactivation of CgVeA caused an obvious decrease in cheA production from 51.32 to 19.76 mg/L under dark conditions.In contrast,CgVeA overexpression resulted in a dramatic increase in cheA production,reaching 206.59 mg/L under light conditions,which was higher than that noted under dark condition.The RT-qPCR results confirmed that CgVeA,as a light responsive regulator,positively regulated cheA biosynthesis by controlling the expression of core genes of the cheA biosynthetic gene cluster and other relevant regulators.Electrophoretic mobility shift assays proved that CgVeA directly regulated LaeA,cheR,and p450,and indirectly regulated PKS.Moreover,CgVeA had a significant effect on the regulation of asexual spores production.When compared with wild-type C.globosum,CgVeA-silenced and CgVeA overexpression mutants presented remarkable differences in sporulation,irrespective of light or dark condition.Besides,CgVeA expression was speculated to negatively regulate spore formation.These findings illustrated the regulatory mechanism of a hypothetical global regulator,CgVeA,in C.globosum,suggesting its potential application in industrial-scale cheA biosynthesis.