The Correlation between the Zeroth-Order General Randic Indices and the π-Electronic Energies of Hexagonal Systems

A formula was proved for computing the zeroth-order general Randic index of a hexagonal system to explore the correlation between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.As a consequence,the extremal hexagonal systems with minimum or maximum zeroth-order general Randic index were completely characterized.Moreover,by using the least-square fit method and regression analysis,a new and close relation was found between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.So the zeroth-order general Randic index is a good measure of the π-electronic energies for benzenoid hydrocarbons.

Increasingπ-electron availability in benzene ring incorporated graphitic carbon nitride for increased photocatalytic hydrogen generation

Increasing the availability ofπ-electron in graphitic carbon nitride(g-C_(3)N_(4))can reduce the band gap and thus enhance the photocatalytic hydrogen(H_(2))generation activity upon exposure to visible light,However,such strategy has not yet been largely applied to increase the H_(2)generation of g-C_(3)N_(4).Herein,we succes s fully increased the amount ofπ-electron in g-C_(3)N_(4)by incorporatingπ-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air.The incorporation of benzene rings not only extends the light absorption of g-C_(3)N_(4)to 650 nm,but also improves the electrical conductivity due to delocalization ofπelectrons in benzene rings.As a result,a 3.4 times enhancement of photocatalytic H_(2)generation was achieved from the g-C_(3)N_(4)with benzene ring incorporation in comparing with that of pristine g-C_(3)N_(4).More interestingly,H_(2)generation still occurs under irradiation of the light ofλ≥490 nm,above the absorption edge of pristine g-C_(3)N_(4)(~460 nm),illustrating the positive effectiveness of incorporated benzene rings on enhancing the H_(2)generation capacity of g-C_(3)N_(4).The present work manifests the advantages of increasingπ-conjugated electrons on designing highly active g-C_(3)N_(4)photocatalysts.

AN IMPLICIT ANALYTIC ENERGY FUNCTION FOR 1-ELECTRON SYSTEM

In this work, an implicit analytic energy function for an electron in a many-center system is derived. The formalism is based on the concept of LCAO in the direct space and the representation of wave functions in the momentum space. In principle, any order of accuracy can be accomplished by iteration. The implicit analytic energy function is discussed thoroughly with a presentation concerning its potential application to molecular problems which are related to the variation of bond angles and lengths.

Aromatic alcohols oxidation and hydrogen evolution over π-electron conjugated porous carbon nitride rods

Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.

P-glycoprotein(ABCB1)-weak dipolar interactions provide the key to understanding allocrite recognition,binding,and transport

P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy of ATP binding and hydrolysis.Here,we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1.In combination with our previous molecular dynamics simulations,these data lead to a new model for allocrite transport by ABCB1.In contrast to previous models,we take into account that the transporter was evolutionarily optimized to operate within a membrane,which dictates the nature of interactions.Hydrophobic interactions drive lipid-water partitioning of allocrites,the transport process’s first step.Weak dipolar interactions(including hydrogen bonding,π-π stacking,and π-cation interactions)drive allocrite recognition,binding,and transport by ABCB1 within the membrane.Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1.Allocrite flopping(or reorientation of the polar part towards the extracellular aqueous phase)occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side.Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane.The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions,as well as to the dielectric constant of the membrane,points to a flopping process,which occurs to a large extent at the membrane-transporter interface.The proposed unidirectional ABCB1 transport cycle,driven by weak dipolar interactions,is consistent with membrane biophysics.

Furan-containing Conjugated Polymers for Organic Solar Cells

Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.

Application of molecular orbital graph theory——A cutting vertex method for evaluating E_π

Just as Tang and Jiang pointed out in ref. [1], the total π-electron energy Eπ of a conjugate molecule is of significance for understanding the stability and aromatic character of molecule or the reaction route. They also proposed the expanded formula for evaluating Eπ by using molecular moment μ1.

Pendant Group Effect of Polymeric Dielectrics on the Performance of Organic Thin Film Transistors

Polymer dielectric is superior to its inorganic counterparts due to not only the low cost and intrinsic flexibility,but also the readily tunable dielectric constant,surface charge trap density,charge ejection and releasing ability and dipole moment,and all these properties play decisive roles in regulating the characteristic and performances of organic thin film transistors(OTFT).However,systematical studies on the relationship between structure and properties of polymeric dielectrics are rare.To this end,a series of polymeric dielectrics with well-defined linkages(ester or amide bonds)and predesigned pendant groups(alkyl-and aromatic-groups)are synthesized in high yields.Detailed studies show that the polyamide dielectrics exhibit higher dielectric constant,surface charge trapping density,and better charge storage capability than corresponding polyester dielectrics.Further,increasing theπelectron delocalization of the pendant groups generally benefits the charge storage property and transistor memory behavior.Theoretical calculation reveals that the hydrogen bonding between the linkage groups and the energy alignment between polymeric dielectric and semiconductor are responsible for the observed performance differences of OTFT with different polymeric dielectrics.These results may shine light on the design of polymeric dielectrics for OTFTs with different applications.