Theoretical Study on the Structural and Optoelectronic Properties of the Linear Perfluorooctane Sulfonate （PFOS）

The perfluoroalkyl substances(PFS) have attracted considerable attention in recent years as a persistent global pollutant to be able to bioaccumulate in higher organisms.In this paper,theoretical analysis on electronic structures,optoelectronic properties and absorption spectra properties of the perflurooctane sulfonate(PFOS) in gas phase have been investigated by using the DFT/TD-DFT method.The geometric structures,electrostatic potentials,energy gaps,ionization potentials,electron affinities,frontier molecular orbital,excitation energies and absorption spectra for the ground state of PFOS were calculated.The result indicates that the ability of accepting electron of neutral PFOS is larger than that of anionic PFOS,while the electron excited by UV irradiation from HOMO to LUMO in the anionic PFOS is easier than that in the neutral PFOS.     

UV-Vis Spectrum and the Third-order Nonlinear Optical Properties of the Chiral Camphorderived β-diketonate Platinum Complexes

UV-Vis spectrum and the third-order nonlinear optical properties of the chiral camphor-derived β-diketonate have been studied at the B3LYP/6-31G* level. The results showed that the introduction of electron-drawing group-CF3 and-C3F7 on β-diketonate made the strongest absorption peak red-shift and the lowest energy absorption blue-shied. Introduction of-OC2H5 on the benzene or pyridine ring made the lowest energy absorption blue-shift. When the-C2H3 was introduced on the benzene or pyridine ring, the lowest energy absorption was red-shifted. Introduction of electron-donating group on β-diketonate can enlarge their nonlinear optical properties. On the contrary, the introduction of electron-drawing group dropped it down.     

Influence of Molecular Structure on the Dimerization Reactivity of Germaaromatic Compounds： a Theoretical Study

Density functional theory (DFT) calculations, at the B3LYP/6-311G** level of theory, were performed to study the reaction mechanism and potential energy surface of the [2 + 2], [4 + 2] and [4 + 4] dimerization reactions of some germaaromatic compounds. The influence of reactant's molecular structure and benzene solvent on the potential energy surface of the studied reactions was investigated. Our calculation results show that [2 + 2] and [4 + 4] reactions are concerted and synchronous processes; while [4 + 2] reactions proceed via a concerted but asynchronous way in general. [2 + 2] and [4 + 2] reactions of germabenzenes and 1-germana- phthalene proceed much more easily than the corresponding [4 + 4] reaction, both thermo- dynamically and kinetically; while most [4 + 2] paths have lower activation barrier than the corres- ponding [2 + 2] ones. As the number of six-membered aromatic rings in reactant molecules becomes larger, [2 + 2], [4 + 2] and [4 + 4] reactions become easier to proceed. The influence of substituents at the Ge atom of germabenzenes on the potential energy surface of [2 + 2] and [4 + 2] reactions correlates with their electronic properties and volume. Solvent effect is not crucial for the potential energy surfaces of the studied reactions.     

First-principles characterization of formate and carboxyl adsorption on stoichiometric CeO2（111）and CeO2（110） surfaces

Molecular adsorption of formate and carboxyl on stoichiometric CeO₂（111） and CeO₂（110） surfaces was studied using periodic density functional theory（DFT+U） calculations.Two distinguishable adsorption modes（strong and weak） of formate are identified.The bidentate configuration is more stable than the monodentate adsorption configuration.Both formate and carboxyl bind at the more open CeO₂（110） surface are stronger.The calculated vibrational frequencies of two adsorbed species are consistent with the experimental measurements.Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO₂ surfaces were investigated.We found that the geometrical configurations of two adsorbed species are not affected by different U parameters（U=0,5,and 7）.However,the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes（<0.2 eV）. The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge while the adsorbed carboxyl is positively charged.Interestingly,with the increasing U parameter,the amount of charge is also increased.     

Theoretical Investigations on the Electronic and Optical Properties of Luminescent Poly（alkylthiophene-co-pyridine）

Quantum-chemical techniques were applied to investigate a series of conjugated polymers： poly（3-octylthien-2,5-ylene-co-pyrid-2,6-ylene） （pl）, poly[pyrid-2,6-ylenebis（3-octylthien-2,5-ylene）] （p2） and poly[pyrid-2,5-ylenebis（3-octylthien-2,5-ylene）] （p3） comprising alternating n-excessive 3-alkylthiophene and n-deficient meta- or para-linked pyridine moieties. Their ground state and excited state structures were optimized with density functional theory B3LYP method, and the optical properties were calculated by the time-dependent density functional theory （TD-DFT） and ZINDO/S methods. Their HOMO-LUMO gaps （An-L）, the lowest excitation energies （Eex）, ionization potentials （IP） and electron affinities （EA） were obtained by extrapolating those of the polymers to the inverse chain length equal to zero （1/n=0）. The calculated results showed that the decrease of pyridylene content increased the HOMO level and decreased the LUMO level while the para-linkage further contributed to it. The IP are in the order： p1〉p2〉p3 but EA are： p1〈p2〈p3. In addition, the decrease of the pyridylene content and the para-linked pyridylene in the backbone of the polythiophene resulted in a narrowed energy gap and bathochromic absorption and emission peaks.     

Theoretical studies on the spectroscopic properties and the substituent effects of pyridyl triazole Os(Ⅱ) complexes

To explore the spectroscopic properties of pyridyl triazole Os(Ⅱ) complexes and how the substituent effects affect the spectroscopic properties of [Os(ptz)2L2] (L=PH3; ptzH=(2-pyridyl)-1,2,4-triazole) (1), [Os(bptz)2L2] (bptzH=3-tert-butyl-5-(2-pyridyl)-1,2,4-triazole) (2), [Os(fptz)2L2] (fptzH=3- (trifluoreomethyl)- 5-(2-pyridyl)-1,2,4-triazole) (3), and [Os(fbtz)2L2] (fbtzH=3-(trifluoreomethyl)-5-(4-tert-butyl- 2-pyridyl)-1,2, 4-triazole) (4), the density functional theory (DFT) method at the B3LYP level ...     

Theoretical studies on phosphoraniminato derivatives of Keggin-type polyoxometalates [PW11O39{MVNPPh3}]3− (M = Fe,Ru): Electronic structures and bonding features

Transition metal phosphoraniminato derivatives of Keggin-type polyoxometalates(POMs) are important intermediates in N-transfer reactions.Density functional theory(DFT) has been employed to calculate the electronic structures,bonding features and redox properties of the iron and ruthenium phosphoraniminato derivatives of Keggin-type POMs,[PW11O39{MVNPPh3}] 3-(M = Fe,Ru).Our DFT calculations show that both anions have the same qualitative M-N single bond features.However,the calculations predict that the FeN system possesses a lower energy and more accessible metalnitrogen antibonding orbital than the RuN system.This results in a greater weakening of the Fe-N bond in the reduction process,and thus enhances its N-transfer reactivity.     

Studies on the Electronic Structures and Spectra of C78（CH2）3

The structures and spectra of 20 possible isomers of C78(CH2)3 have been studied by using AM1,INDO/CIS and DFT methods. The results show that the most stable isomer is 1,2,3,4,5,6-C78(CH2)3 (A) with annulene structures,where three -CH2 groups are added to the 6/6 bonds located at the same hexagon passed by the shortest axis of C78 (C2v). Compared with that of C78 (C2v),the first absorption in the electronic spectrum of C78(CH2)3 (A) is blue-shifted because of its wider LUMO-HOMO energy gap. While the IR frequencies of the C–C bonds on the carbon cage are red-shifted owing to the formation of annulene structures and the extension of the conjugated system. The chemical shifts of the carbon atoms in 13C NMR spectra are moved upfield upon the addition.     

Theoretical Study on the Structural and Electronic Properties of the Reduced SnO2 （110） Surface

The reduced SnO2(110) surface has been investigated by using first-principles method with a slab model. By examining the vacancy formation energy of three kinds of reduced SnO2(110) surfaces, the most energetically favorable defect surface is confirmed to be the surface with the coexistence of bridging and in-plane oxygen vacancies, which is different with the traditional model by only removing bridging oxygen. The results of band structure calculations indicate that the electronic structure of this defect surface is similar to the SnO surface.     

Theoretical Studies on the Binding of Cd~（2＋） to Uracil and Its Thio-derivatives

The interaction of Cd2+ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory(DFT) calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2+ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2+ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2+ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2+ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2+,all tautomers are energetically accessible and should be observed in the gas phase.     

TD-DFT Study on the Electronic Spectrum Properties of 2,7＇-（Ethylene）- bis-8-hydroxyquinoline and Its Derivatives

The structures of 2,7＇-（ethylene）-bis-8-hydroxyquinoline and its derivatives were optimized at the ground states using ab initio HF and B3LYP methods. At the same time, the molecular structures of the first singlet excited state for 2,7＇-（ethylene）-bis-8-hydroxyqulnoline and its derivatives were optimized by CIS/6-31G（d）. The absorption and emission spectra based on the above structures were obtained by the time-dependent density functional theory （TD-DFT） by the B3LYP method with the 6-31G（d） basis set. The calculated results of luminescence originate from the electronic transition from the hydroxphenol ring of 8-hydroxyquinoline A to the pyridine ring of 8-hydroxyquinoline B. Their luminescence wave bands can be tuned by different substituents on the ligand of 8-hydroxyquinoline.     

QSPR Studies on lgK_(ow) and lgK_(oc) of Fluorobenzenes and Property Parameters Based on HF and DFT Calculations

1 INTRODUCTION Quantitative structure-activity relationship (QSAR) equation could be employed to predict the biological activities of unknown compounds, which is signifi- cant for initial screening and evaluation of toxic compounds[1]. Soil sorption coeff…     

Theoretical Investigation on the Luminescent Properties of Polyfluorene and Poly（fluorene-co-thiophene）

The density functional theory was employed to study the structures, ionization potentials(IPs), electron affinities(EAs), and HOMO-LUMO gaps(ΔH-L) of the oligomers. The time-dependent density functional theory(TD-DFT) and ZINDO were employed to study the lowest excitation energies(Egs) and the absorption and emission spectra of the oligomers of polyfluorene(PF) and poly(fluorene-co-thiophene)(PFT). By extrapolating ΔH-L and Egs to those of infinite chain length, band gaps and effective conjugation lengths o...     

TD-DFT Study on the Electronic Spectrum Properties of 2,7′-(Ethylene)-bis-8-hydroxyquinoline and Its Derivatives

The structures of 2,7′-(ethylene)-bis-8-hydroxyquinoline and its derivatives were optimized at the ground states using ab initio HF and B3LYP methods. At the same time, the molecular structures of the first singlet excited state for 2,7′-(ethylene)-bis-8-hydroxyquinoline and its derivatives were optimized by CIS/6-31G(d). The absorption and emission spectra based on the above structures were obtained by the time-dependent density functional theory (TD-DFT) by the B3LYP method with the 6-31G(d) basis set. The calculated results of luminescence originate from the electronic transition from the hydroxphenol ring of 8-hydroxyquinoline A to the pyridine ring of 8-hydroxyquinoline B. Their luminescence wave bands can be tuned by different substituents on the ligand of 8-hydroxyquinoline.     

Exploring the H-abstraction reactions of CHCl·-/CCl2·- with CX3H（X = F,Cl,Br and I） using the density functional theory method

Gas-phase hydrogen abstraction reactions have been compared using the popular density functional theory(DFT) functional BHandHLYP/aug-cc-pVTZ/RECP level of theory,on the basis of the model reaction CHCl·-/CCl2·-+ CX3H(X = F,Cl,Br and I).Our theoretical findings suggest the efficiency of the H-abstraction reactions induced by either CHCl·-or CCl2·-increases as the substrate is changed from CF3H to CI3H,and that CHCl·-has a higher activity in hydrogen abstraction than CCl2·-for a given substrate.The entropy effect at 298 K does not significantly change the trend in reactivity of the various reactions,which is in general controlled by the heights of activation energies △E≠.Therefore,we have explored the origin of the energy barriers △E≠ of the reactions using the activation strain model of chemical reactivity.     

Theoretical Studies on the Third-order Nonlinear Optical Properties and Two-photon Absorption of Stilbene Derivatives

Different types of stilbene derivatives (D-π-D, A-π-A, D-π-A) were investigated with AM1, and specially, equilibrium geometries of symmetrical stilbene derivatives (D-π-D) were studied using of PM3. With the same method INDO/CI, the UV-vis spectra were explored and the position and strength of the two-photon absorption were predicated by Sum-Over-States expression. The relationships of the structures, spectra and nonlinear optical properties have been examined. The influence of various substituents on two photon absorption cross-sections was discussed micromechanically.     

Theoretical Studies on Electronic Structures and Spectra for C80^n （D5d,C2v） Singlet

1INTRODUCTIONC80iscalledthemissingfullereneduetoitsinstabilityinkineticsandlowerLUMO-HOMOenergygap[1],aswellasthelowerabundanceintheexperimentandthedifficultyinsynthesis[1~5].However,thestableexistenceofcomplexLa2@-C80[2]stimulatestheresearchinterestinionsofC80.Zhang[3]performedtheoreticalstudiesonthestabi-lityandNMRspectraforC80isomers.Nakao[4]cal-culatedtheLUMO-HOMOenergygapofC80byusingabinitiomolecularorbital.Hennrich[5]syn-thesizedC80(D5)fromfullerenesootextractionbydHPLC.…     

Detection and Theoretical Study of Fukui Function of Nitroaromatics by Carbazole-Based Iridium（Ⅲ）Phosphorescent Probe北大核心CSCD

A room temperature phosphorescent Ir（Ⅲ）complex Ir（ppyCz）3 is synthesized by a two-step synthesis method with a carbazole modified organic ligand. The high-efficiency luminescent detection strategy of six familiar nitroaromatics including 1,3-dinitrobenzene,etc. is developed using Ir（ppyCz）3 as the luminescent probe. The highest detection efficiency of 1,3-dinitrobenzene by Ir（ppyCz）3 is demonstrated with the quenching content KSV of（26. 38±1. 05）L/mmol,and minimum detection limit of 2. 50×10−6 mmol/L. Density functional theory calculations and spectral overlap experiments show that the detection mechanism of Ir（ppyCz）3 for the six nitroaromatics is assigned to electron transfer. The sequence of the orbital weighted Fukui function for the six nitroaromatics dovetails with the corresponding detection efficiency sequence of nitroaromatics by Ir（ppyCz）3. © 2022, Science Press (China). All rights reserved.     

Theoretical Studies on the Thermodynamic Properties and Detonation Performances of Bicyclic Nitramines： TNAD Isomers

1 INTRODUCTION Nowadays, HEDMs have been receiving heated attention because of their superior explosive per- formances to the currently used materials. Searching for novel HEDMs to meet the future demands has become one of the most activated regions and seems to be never ending. As is well known, nitramines have important applications in both civilian and military fields for a long time. This group of com- pounds is still a source of explosives or propellants that possess predominantl…