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1.
J Mol Graph Model ; 89: 131-138, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30884450

RESUMO

The iridium(III) complexes could be excellent second-order nonlinear optical (NLO) switch materials due to various advantages including abundant valence states, the diversity of coordination forms and rich electrochemical properties. In this work, the substituent effect and the multi-state switchable response of a series of novel Ir(CˆN)2ADC complexes (CˆN = cyclometalated ligands and ADC = diaminocarbene), induced by electrochemical behavior, have been calculated by density functional theory. The results show that the introducing strong electron-withdrawing groups on ADC ligands significantly enhanced the static first hyperpolarizabilities (ßtot). Moreover, a distinct improvement of the ßtot values can be found from the neutral complexes to the corresponding redox states. By this way, the remarkable multi-state NLO switch can be achieved. Remarkably, the ßtot values of the one-electron-oxidized complex 1+ and the one-electron-reduced complex 1- are ∼5.4 and ∼12.7 times larger than the corresponding neutral complex 1, respectively. The larger ßtot values are attributed to the lower transition energy and remarkable bathochromic shift of maximal absorption wavelength, which can be further illustrated by the separate distribution of ß density. We envision that these studied iridium complexes can be seen as versatile and novel second-order NLO switching materials.

2.
J Mol Graph Model ; 77: 363-371, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28946068

RESUMO

Ru metal acetylide electron donor-acceptor complexes have important applications in the field of nonlinear optics. Herein, in this work, a series of half-sandwich ruthenium-based Cp*(dpe)Ru ([Ru*]) metal complexes with the dihydroazulene/vinylheptafulvene (DHA/VHF) have been investigated by density functional theory (DFT) calculations. The results showed that the position of the [Ru*] acetylide functionality, either para or meta on the phenylene ring to the DHA/VHF core (1c/1o and 2c/2o), and additional a p-phenylene spacer (3c/3o) had a great influence on the second-order nonlinear optical (NLO) responses. The systems 1 and 3 can significantly increased second-order NLO responses compared with system 2. It was attributed to the more obvious charge transfer along y-axis, which is from [Ru*] acetylide functionality to DHA, accompanied by a significant decrease of the transition energy according electron density difference maps and time-dependent DFT calculations. The ßvec values of the open-ring complexes were larger than the corresponding closed-ring complexes owing to the smaller HOMO-LUMO gap in the open-ring complexes. It was also because of the smaller BLA values in open-ring complexes, which had stronger π-conjugation. Especially, the change ratio of ßvec value of system 2 was the largest due to the fact that their charge transfers degree varied greatly. In addition, the frequency-dependent NLO properties of the studied complexes were evaluated at 0.0239 a.u. and 0.0340 a.u. The calculation results demonstrated that the magnitude of the frequency-dependent first hyperpolarizability increased with the increasing frequency. We believe that our present work will be beneficial for further theoretical and experimental studies on large second-order NLO responses of metal complexes.


Assuntos
Azulenos/química , Complexos de Coordenação/química , Teoria Quântica , Rutênio/química , Elétrons , Estrutura Molecular , Óptica e Fotônica
3.
Phys Chem Chem Phys ; 19(3): 2322-2331, 2017 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-28054686

RESUMO

To reveal a new structure-property relationship regarding the nonlinear optical (NLO) properties of fullerenes that are associated with gamma (γ) density, fullerenes I (C40, C50, C60 and C70), whose heights range from 4.83 to 7.96 Å, and II (C24, C36, C48 and C72), whose widths range from 4.45 to 8.22 Å, have been the research objects. Calculation of their geometric and electronic structures, absorption spectra, and the second hyperpolarizability (γ) and the γ density analysis have been performed. It is found that the electronic spatial extent and the polarizability (α) value increase linearly as the fullerenes increase by every 12 carbon atoms. Similarly, the γ values are also proportional to the fullerene size. It is worth noting that the relative magnitude of γxxxx and γzzzz was exactly consistent with that of the width and height of fullerenes. The analysis of γ density provides the essential reason for this result, that is, the magnitude of the contribution to γ values associated with γ densities is proportional to the density amplitudes multiplied by the distance between them. Larger fullerenes possess larger density amplitudes and longer distances, resulting in larger γ values with respect to smaller fullerenes. This work presents a new structure-property interplay between the width and height of the fullerenes and their second hyperpolarizability γ. Moreover, the γ density analysis provides a new insight to explore the nature of the relationship between the structure and the NLO properties.

4.
J Mol Graph Model ; 72: 156-167, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28092834

RESUMO

The NO3-initiated reactions of CH3OCH3 and CH3OCH2CH3 have been investigated by the BHandHLYP method in conjunction with the 6-311G(d,p) basis set. Thermodynamic and kinetic data are further refined using the comparatively accurate CCSD(T) method. According to the values of reaction enthalpies (ΔHr,298θ) and reaction Gibbs free energies (ΔGr,298θ) from CH3OCH2CH3 with NO3 system, we find that H-abstraction pathway from the α-CH2 group is more exothermic. It is further confirmed by the calculated CH bond dissociation energy of CH3OCH2CH3 molecule. All the rate constants, computed through means of canonical variational transition state with small-curvature tunneling correction, are fitted to the three-parameter expressions k1=1.54×10-23T3.34exp(-1035.53/T) and k2=3.55×10-26T4.31exp(-281.24/T)cm3molecule-1s-1 and branching ratios are computed over the temperature range 200-600K. The branching ratios are also discussed. The atmospheric lifetimes of CH3OCH3 and CH3OCH2CH3 determined by the NO3 radical are about 270 and 29days, respectively.


Assuntos
Atmosfera/química , Éteres/química , Modelos Moleculares , Nitratos/química , Elétrons , Cinética , Conformação Molecular , Estereoisomerismo , Termodinâmica , Vibração
5.
J Phys Chem A ; 120(46): 9330-9340, 2016 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-27934245

RESUMO

Zwitterionic complexes have been the subject of great interest in the past several decades due to their multifunctional application in supramolecular chemistry. Herein, a series of internally stable charge-compensated carboranylated square-planar Pt(II) zwitterionic complexes have been explored by density functional theory aim to assessing their structures, the first hyperpolarizabilities, first hyperpolarizability densities, and electronic absorption spectra. It is found that the first hyperpolarizabilities of two-dimensional (2D) structure complexes are much larger with respect to the one-dimensional complex. It is ascribed to the lower transition energy and more obvious charge transfer, which can be further illustrated by their large amplitude and separate distribution of first hyperpolarizability density. In addition, the first hyperpolarizabilities of 2D complexes can be further significantly modified by introducing electron-donating/withdrawing groups on the carborane cage. As a consequence, we believe that these 2D zwitterionic complexes can behave as novel second-order nonlinear optical chromophore with a promising future.

6.
Environ Sci Pollut Res Int ; 23(23): 23467-23484, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27614635

RESUMO

Multichannel gas-phase reactions of CH3OCH2CH2Cl/CH3CH2OCH2CH2Cl with chlorine atom and hydroxyl radical have been investigated using ab initio method and canonical variational transition-state dynamic computations with the small-curvature tunneling correction. Further energetic information is refined by the coupled-cluster calculations with single and double excitations (CCSD)(T) method. Both hydrogen abstraction and displacement processes are carried out at the same level. Our results reveal that H-abstraction from the -OCH2- group is the dominant channel for CH3OCH2CH2Cl by OH radical or Cl atom, and from α-CH2 of the group CH3CH2- is predominate for the reaction CH3CH2OCH2CH2Cl with Cl/OH. The contribution of displacement processes may be unimportant due to the high barriers. The values of the calculated rate constants reproduce remarkably well the available experiment data. Standard enthalpies of formation for reactants and product radicals are calculated by isodesmic reactions. The Arrhenius expressions are given within 220-1200 K. The atmospheric lifetime, ozone depleting potential (ODP), ozone formation potential (OFP), and global warming potential (GWP) of CH3OCH2CH2Cl/CH3CH2OCH2CH2Cl are investigated. Meanwhile, the atmospheric fate of the alkoxy radicals are also researched using the same level of theory. To shed light on the atmospheric degradation, a mechanistic study is obtained, which indicates that reaction with O2 is the dominant path for the decomposition of CH3OCH(O•)CH2Cl, the C-C bond scission reaction is the primary reaction path in the consumption of CH3CH(O•)OCH2CH2Cl in the atmosphere. HIGHLIGHTS: Ab initio method and canonical variational transition-state theory are employed to study the kinetic nature of hydrogen abstraction reactions of CH3OCH2CH2Cl/CH3CH2OCH2CH2Cl with Cl atom and OH radical and fate of alkoxy radicals (CH3OCH(O•)CH2Cl/CH3CH(O•)OCH2CH2Cl).


Assuntos
Álcoois/química , Cloro/química , Hidrocarbonetos Clorados/química , Hidrogênio/química , Radical Hidroxila/química , Poluentes Atmosféricos/química , Poluição do Ar , Simulação por Computador , Hidrogênio/isolamento & purificação , Cinética , Modelos Químicos , Conformação Molecular , Termodinâmica
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