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1.
Chem Asian J ; 17(14): e202200266, 2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35608795

RESUMO

Herein, three hydroxy-tetraphenylimidazole (HPI)-based fluorophores (HPI-TPA, HPI-PCz, and HPI-CzP) are designed and synthesized by disubstituted HPI core with arylamine units of triphenylamine (TPA), phenyl carbazole (PCz), and carbazole phenyl (CzP) at 3,5-positions of the N-phenyl ring of HPI, respectively. Their photophysical properties are theoretically and experimentally examined. HPI-TPA shows a hybridized local and charge transfer (HLCT) excited state characteristic and emits deep blue color via an HLCT mechanism, while both HPI-PCz and HPI-CzP exhibit excited-state intramolecular proton transfer (ESIPT) property and display pure keto form emissions. They possess high thermal stability and are successfully fabricated as emitters in organic light-emitting diodes (OLEDs). All devices exhibit intense blue color emissions with low turn-on voltages (3.5-3.7 V). Particularly, HPI-TPA-based OLED emits light in the deep-blue region with a high maximum external quantum efficiency (EQEmax ) of 3.77% and a decent efficiency roll-off.

2.
Polymers (Basel) ; 13(24)2021 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-34960841

RESUMO

In this work, we successfully synthesized high thermal stable 1,n-bis(N-(N'-butylimidazolium)alkane bishexafluorophosphates (1,n-bis[Bim][PF6], n = 4, 6, 8, and 10) catalysts in 55-70% yields from imidazole which were applied as non-toxic DILs catalysts with 1-butanol as initiator for the bulk ROP of ε-caprolactone (CL) in the varied ratio of CL/nBuOH/1,4-bis[Bim][PF6] from 200/1.0/0.25-4.0 to 700/1.0/0.25-4.0 by mol%. The result found that the optimal ratio of CL/nBuOH/1,4-bis[Bim][PF6] 400/1.0/0.5 mol% at 120 °C for 72 h led to the polymerization conversions higher than 95%, with the molecular weight (Mw) of PCL 20,130 g mol-1 (D~1.80). The polymerization rate of CL increased with the decreasing linker chain length of ionic liquids. Moreover, the mechanistic study was investigated by DFT using B3LYP (6-31G(d,p)) as basis set. The most plausible mechanism included the stepwise and coordination insertion in which the alkoxide insertion step is the rate-determining step.

3.
J Phys Chem A ; 125(24): 5314-5325, 2021 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-34125551

RESUMO

The detailed excited-state intermolecular proton transfer (ESInterPT) mechanism of 2,7-diazaindole with water wires consisting of either one or two shells [2,7-DAI(H2O)n; n = 1-5] has been theoretically explored by time-dependent density functional theory using microsolvation with an implicit solvent model. On the basis of the excited-state potential energy surfaces along the proton transfer (PT) coordinates, among all 2,7-DAI(H2O)n, the multiple ESInterPT of 2,7-DAI(H2O)2+3 through the first hydration shell (inner circuit) is the most easy process to occur with the lowest PT barrier and a highly exothermic reaction. The lowest PT barrier resulted from the outer three waters pushing the inner circuit waters to be much closer to 2,7-DAI, leading to the enhanced intermolecular hydrogen-bonding strength of the inner two waters. Moreover, on-the-fly dynamic simulations show that the multiple ESInterPT mechanism of 2,7-DAI(H2O)2+3 is the triple PT in a stepwise mechanism with the highest PT probability. This solvation effect using microsolvation and dynamic simulation is a cost-effect approach to reveal the solvent-assisted multiple proton relay of chromophores based on excited-state proton transfer.

4.
Molecules ; 26(4)2021 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-33562757

RESUMO

The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with γ-cyclodextrin (γ-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to γ-CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S0) and the first excited (S1) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the γ-CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and γ-CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S1 state confirmed by the shorter interHB and intraHB distances and the red-shift of O-H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S1 state, the keto form of 3HF is stabilized by γ-CD, explaining the increased quantum yield of keto emission of 3HF when complexing with γ-CD in the experiment. In the other word, ESPT of 3HF is more favorable in the γ-CD hydrophobic cavity than in aqueous solution.


Assuntos
Flavonoides/química , Prótons , Solventes/química , Água/química , gama-Ciclodextrinas/química , Modelos Moleculares , Conformação Molecular
5.
Inorg Chem ; 59(24): 18253-18263, 2020 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-33289543

RESUMO

The interplay between noncovalent interactions involving metal complexes may lead to the formation of aggregates (i.e., ground state dimers, trimers, n-mers, etc.), and this is often linked to dramatic changes in their physical and chemical properties as compared to the original properties of the isolated units. Dimers and trimers can also be formed in the excited state potential energy surfaces, i.e., excimers. Excimers are short-lived but are also often characterized by different optical properties from those of the isolated units. Understanding the nature of noncovalent interactions and the presence or not of cooperativity effects in both aggregates and excimers is thus extremely important to rationalize these variations. In this study, we present computational investigations on isoquinolinyl pyrazolate Pt(II) complexes. Our results highlight that cooperativity effects between noncovalent interactions, which are modulated by sterically demanding substituents and metallophilic Pt···Pt interactions, are present only on certain investigated excimers. We use density functional theory (DFT) calculations to examine the cooperativity effects and the changes in the photophysical properties. Different descriptors of cooperativity effects between noncovalent interactions, including the synergetic, genuine nonadditive, and total interaction energies, were evaluated for a series of Pt(II) aggregates and excimers. In addition, energy decomposition analysis (EDA) calculations were performed to rationalize the origins of the cooperative effects. The cooperative effects in trimer excimers (in their lowest triplet excited state, i.e., T1) led to shortened Pt···Pt contacts as compared to the trimer aggregates. Furthermore, this synergy between noncovalent interactions is ultimately responsible for the formation of the excimers and the striking changes in the measured photophysical properties. More in detail, we report a change in the character of the lowest-lying triplet excited state when going from dimer excimers (i.e., of mixed triplet ligand-centered and triplet metal-to-ligand charge transfer (3LC/3MLCT) character) to trimer excimers (i.e., of triplet metal-metal-to-ligand charge transfer (3MMLCT) character). The EDA reveals that the total interaction energy on trimer excimers is subtly controlled by the electrostatic and dispersion terms.

6.
Phys Chem Chem Phys ; 22(35): 19877-19887, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32852020

RESUMO

Hydrogen sulfide (H2S) leads to corrosion in transport lines and poisoning of many catalysts. Meanwhile, H2S is an inexhaustible potential source of hydrogen, which is a very valuable chemical reagent and an environmentally friendly energy product. Therefore, removal of H2S and producing hydrogen gas using potential catalysts has been intensively studied, according to the equation: H2S(g) + CO(g) → COS(g) + H2(g). In this study, hydrogen sulfide (H2S) decomposition in the presence of CO over transition metal-doped ZSM-12 clusters (TM-ZSM-12) has been investigated based on DFT calculations at the B3LYP-D3/6-31G(d,p) level. The calculation results reveal that the proposed reaction mechanism is controlled by 4 key steps, (i) hydrogen dissociation (Ea1 = +0.04 eV for the 1st hydrogen and Ea2 = +0.22 eV for the 2nd hydrogen), (ii) COS desorption (the rate-determining step of this H2S removal process, Edes = +1.18 eV), (iii) hydrogen diffusion to the transition metal with an energy barrier (Ea3) of +0.62 eV, and (iv) the H2 formation step (Ea4 = +0.94 eV). Our results indicate that in the presence of CO, the Cu-ZSM-12 cluster has a potential application as a highly active catalyst for H2S removal together with hydrogen production.

7.
Inorg Chem ; 59(9): 6176-6186, 2020 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-32314584

RESUMO

A novel Cd(II) supramolecular coordination framework containing mixed functionalized luminophore ligands, namely, [Cd(AS)2(phen)2]EtOH or 1 (where AS = 4-aminosalicylate, phen = 1,10-phenanthroline, EtOH = ethanol), was successfully synthesized as a solid-state luminescent sensor for the detection of amine vapors. The single-crystal X-ray diffraction analysis revealed that 1 possesses a three-dimensional (3D) supramolecular framework enclosing ethanol molecule in the lattice. The supramolecular structure is well-stabilized by various noncovalent intermolecular interactions through functional groups of ligands. Compound 1 shows an intense yellow solid-state emission and displays a reversibly discriminative luminescent response to NH3 and ethylenediamine (EDA) vapors through very large blue-shifted luminescent spectra with distinguishable emission colors under UV light. This work reports the first time for selective luminescent sensing of NH3 and EDA vapors with considerably different emission color change. A sensing mechanism has been confirmed by density functional theory and time-dependent density functional theory calculations that agrees well with the experimental results. Also, 1 exhibits a good recyclability over five cycles for sensing of NH3 and EDA vapors.

8.
Sci Rep ; 9(1): 18996, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31813932

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

9.
J Phys Chem A ; 123(50): 10685-10693, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31769683

RESUMO

Applications of the B3LYP and LC-BLYP functionals with the 6-311+G(d,p) basis set for predicting absorption and fluorescence spectra of benzothiazole and 11 [1,3]thiazolo[4,5-b]pyrazine (TPy) derivatives in implicit solvents (cyclohexane and methanol) were tested and compared with experimental results. The damping parameter of LC-BLYP was tuned for simulating absorption and fluorescence spectra of each compound. For the 11 TPy derivatives, four and seven compounds are small- and medium-sized TPy derivatives, respectively. From this calculation, TD-B3LYP can be used to simulate the absorption spectra of the small-sized compounds in cyclohexane and methanol, but it gives poor results for the fluorescence spectra in cyclohexane and methanol. Contrarily, the LC-BLYP functional with the optimal damping parameter can reproduce the absorption and fluorescence spectra of all compounds in cyclohexane and methanol. The values of the damping parameter of LC-BLYP depend on the types of substituents and solvents. Moreover, the conformations of the compounds do not affect the spectra, and the molecular size and molecular dipole moment do not affect the damping parameter. In addition, types and the number of substitutions attached to the phenyl rings of TPy as well as solvent polarity play the key roles in the long-wavelength fluorescence emission and fluorescence brightness of the compounds. The intramolecular charge transfer of the compounds containing the -NMe2 and -CN groups is predominant in methanol, resulting in a large Stokes shift and oscillator strength.

10.
Sci Rep ; 9(1): 10205, 2019 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-31308429

RESUMO

The human T1R2-T1R3 sweet taste receptor (STR) plays an important role in recognizing various low-molecular-weight sweet-tasting sugars and proteins, resulting in the release of intracellular heterotrimeric G protein that in turn leads to the sweet taste perception. Xylitol and sorbitol, which are naturally occurring sugar alcohols (polyols) found in many fruits and vegetables, exhibit the potential caries-reducing effect and are widely used for diabetic patients as low-calorie sweeteners. In the present study, computational tools were applied to investigate the structural details of binary complexes formed between these two polyols and the T1R2-T1R3 heterodimeric STR. Principal component analysis revealed that the Venus flytrap domain (VFD) of T1R2 monomer was adapted by the induced-fit mechanism to accommodate the focused polyols, in which α-helical residues 233-268 moved significantly closer to stabilize ligands. This finding likely suggested that these structural transformations might be the important mechanisms underlying polyols-STR recognitions. The calculated free energies also supported the VFD of T1R2 monomer as the preferential binding site for such polyols, rather than T1R3 region, in accord with the lower number of accessible water molecules in the T1R2 pocket. The E302 amino acid residue in T1R2 was found to be the important recognition residue for polyols binding through a strongly formed hydrogen bond. Additionally, the binding affinity of xylitol toward the T1R2 monomer was significantly higher than that of sorbitol, making it a sweeter tasting molecule.


Assuntos
Receptores Acoplados a Proteínas G/metabolismo , Percepção Gustatória/fisiologia , Paladar/fisiologia , Sítios de Ligação , Membrana Celular/metabolismo , Dimerização , Humanos , Ligantes , Modelos Moleculares , Receptores Acoplados a Proteínas G/fisiologia , Sorbitol/metabolismo , Álcoois Açúcares/metabolismo , Edulcorantes/metabolismo , Xilitol/metabolismo
11.
Polymers (Basel) ; 11(1)2019 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-30960130

RESUMO

2-Hydroxypropyl-ß-cyclodextrin (HPßCD) has unique properties to enhance the stability and the solubility of low water-soluble compounds by inclusion complexation. An understanding of the structural properties of HPßCD and its derivatives, based on the number of 2-hydroxypropyl (HP) substituents at the α-d-glucopyranose subunits is rather important. In this work, replica exchange molecular dynamics simulations were performed to investigate the conformational changes of single- and double-sided HP-substitution, called 6-HPßCDs and 2,6-HPßCDs, respectively. The results show that the glucose subunits in both 6-HPßCDs and 2,6-HPßCDs have a lower chance of flipping than in ßCD. Also, HP groups occasionally block the hydrophobic cavity of HPßCDs, thus hindering drug inclusion. We found that HPßCDs with a high number of HP-substitutions are more likely to be blocked, while HPßCDs with double-sided HP-substitutions have an even higher probability of being blocked. Overall, 6-HPßCDs with three and four HP-substitutions are highlighted as the most suitable structures for guest encapsulation, based on our conformational analyses, such as structural distortion, the radius of gyration, circularity, and cavity self-closure of the HPßCDs.

12.
J Mol Graph Model ; 89: 122-130, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30884449

RESUMO

Hepatitis C has become an important health problem that requires expensive treatment and leads to liver tumorigenesis. Hepatitis C virus (HCV), which is the main cause of hepatitis C, has a high mutation rate due to the lack of proofreading activity of the RNA polymerase enzyme. The NS3/4A serine protease is an important target for anti-HCV drug discovery and development because of its crucial role in the cleavage of the polypeptides involved in viral replication. In the present study, all-atom molecular dynamics simulation was performed to elucidate the effect of the single point mutations R155K and D168A in the HCV genotype 1 NS3/4A protease on the structural dynamics, molecular interactions and susceptibility of asunaprevir (ASV), a second-generation NS3/4A protease inhibitor. Principal component analysis indicated that these two mutations converted the direction of motion of residues 123, 155 and 168 in the binding pocket to significantly point outwards from ASV, resulting in a loss of the hydrogen bond network of residues R123···R155···D168. The free energy calculations based on different semiempirical QM/MM-GBSA methods revealed that the binding affinity of ASV with the two mutant forms of the NS3/4A protease was significantly decreased in the order of wild-type < R155K < D168A. This work provided useful structural information regarding the atomistic understanding of acquired drug resistance against ASV caused by the R155K and D168A mutations.


Assuntos
Antivirais/química , Antivirais/farmacologia , Hepacivirus/efeitos dos fármacos , Hepacivirus/genética , Isoquinolinas/química , Isoquinolinas/farmacologia , Mutação , Sulfonamidas/química , Sulfonamidas/farmacologia , Proteínas não Estruturais Virais/genética , Alelos , Substituição de Aminoácidos , Farmacorresistência Viral , Humanos , Ligação de Hidrogênio , Ligantes , Conformação Molecular , Simulação de Dinâmica Molecular , Inibidores de Proteases/química , Inibidores de Proteases/farmacologia , Ligação Proteica , Relação Quantitativa Estrutura-Atividade , Eletricidade Estática , Proteínas não Estruturais Virais/metabolismo , Replicação Viral/efeitos dos fármacos
13.
Sci Rep ; 9(1): 745, 2019 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-30679605

RESUMO

The association of systemic sclerosis with anti-Topoisomerase 1 antibody (ATASSc) with specific alleles of human leukocyte antigen (HLA)-DR has been observed among various ethnics. The anti-Topoisomerase 1 antibody is a common autoantibody in SSc with diffuse cutaneous scleroderma, which is one of the clinical subtypes of SSc. On the other hand, an immunodominant peptide of topoisomerase 1 (Top1) self-protein (residues 349-368) was reported to have strong association with ATASSc. In this study, molecular dynamics simulation was performed on the complexes of Top1 peptide with various HLA-DR subtypes divided into ATASSc-associated alleles (HLA-DRB1*08:02, HLA-DRB1*11:01 and HLA-DRB1*11:04), suspected allele (HLA-DRB5*01:02), and non-associated allele (HLA-DRB1*01:01). The unique interaction for each system was compared to the others in terms of dynamical behaviors, binding free energies and solvation effects. Our results showed that three HLA-DR/Top1 complexes of ATASSc association mostly exhibited high protein stability and increased binding efficiency without solvent interruption, in contrast to non-association. The suspected case (HLA-DRB5*01:02) binds Top1 as strongly as the ATASSc association case, which implied a highly possible risk for ATASSc development. This finding might support ATASSc development mechanism leading to a guideline for the treatment and avoidance of pathogens like Top1 self-peptide risk for ATASSc.


Assuntos
DNA Topoisomerases Tipo I/genética , Cadeias HLA-DRB1/química , Cadeias HLA-DRB5/química , Escleroderma Sistêmico/genética , Alelos , Anticorpos Anti-Idiotípicos/química , Anticorpos Anti-Idiotípicos/genética , Anticorpos Anti-Idiotípicos/imunologia , DNA Topoisomerases Tipo I/química , DNA Topoisomerases Tipo I/imunologia , Epitopos/genética , Epitopos/imunologia , Predisposição Genética para Doença , Cadeias HLA-DRB1/genética , Cadeias HLA-DRB1/imunologia , Cadeias HLA-DRB5/genética , Cadeias HLA-DRB5/imunologia , Humanos , Simulação de Dinâmica Molecular , Peptídeos/química , Peptídeos/genética , Peptídeos/imunologia , Ligação Proteica/genética , Estabilidade Proteica , Fatores de Risco , Escleroderma Sistêmico/imunologia , Escleroderma Sistêmico/patologia
14.
J Enzyme Inhib Med Chem ; 34(1): 134-143, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30394113

RESUMO

Targeted cancer therapy has become one of the high potential cancer treatments. Human topoisomerase II (hTopoII), which catalyzes the cleavage and rejoining of double-stranded DNA, is an important molecular target for the development of novel cancer therapeutics. In order to diversify the pharmacological activity of chalcones and to extend the scaffold of topoisomerase inhibitors, a series of chalcones was screened against hTopoIIα by computational techniques, and subsequently tested for their in vitro cytotoxicity. From the experimental IC50 values, chalcone 3d showed a high cytotoxicity with IC50 values of 10.8, 3.2 and 21.1 µM against the HT-1376, HeLa and MCF-7 cancer-derived cell lines, respectively, and also exhibited an inhibitory activity against hTopoIIα-ATPase that was better than the known inhibitor, salvicine. The observed ligand-protein interactions from a molecular dynamics study affirmed that 3d strongly interacts with the ATP-binding pocket residues. Altogether, the newly synthesised chalcone 3d has a high potential to serve as a lead compound for topoisomerase inhibitors.


Assuntos
Chalconas/farmacologia , DNA Topoisomerases Tipo II/metabolismo , Ensaios de Seleção de Medicamentos Antitumorais , Simulação de Acoplamento Molecular , Neoplasias/tratamento farmacológico , Antineoplásicos/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Chalconas/síntese química , Chalconas/química , Desenho de Fármacos , Eletroforese em Gel de Poliacrilamida , Ativação Enzimática/efeitos dos fármacos , Células HeLa , Humanos , Concentração Inibidora 50 , Modelos Moleculares , Relação Estrutura-Atividade
15.
J Biomol Struct Dyn ; 37(13): 3354-3365, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30126341

RESUMO

Two important glycoproteins on the influenza virus membrane, hemagglutinin (HA) and neuraminidase (NA), are relevant to virus replication. As previously reported, HA has a substrate specificity towards SIA-2,3-GAL-1,4-NAG (3SL) and SIA-2,6-GAL-1,4-NAG (6SL) glycans, while NA can cleave both types of linkages. However, the substrate binding into NA and its preference are not well understood. In this work, the glycan binding and specificity of human and avian NAs were evaluated by classical molecular dynamics (MD) simulations, whilst the conformational diversity of 3SL avian and 6SL human glycans in an unbound state was investigated by replica exchange MD simulations. The results indicated that the 3SL avian receptor fits well in the binding cavity of all NAs and does not require a conformational change for such binding compared to the flexible shape of the 6SL human receptor. From the QM/MM-GBSA binding free energy and decomposition free energy data, 6SL showed a much stronger binding towards human NAs (H1N1, H2N2 and H3N2) than to avian NAs (H5N1 and H7N9). This suggests that influenza NAs have a substrate specificity corresponding to their HA, indicating the functional balance between the two important glycoproteins. Both linkages show distinct glycan topologies when complexed with NAs, while the flexibility of torsion angles between GAL and NAG in 6SL results in the various shapes of glycan and different binding patterns. Lower conformational diversities of both glycans when bound to NA compared to the unbound state were found, and were required in order to be accommodated within the NA cavity. Communicated by Ramaswamy H. Sarma.


Assuntos
Simulação de Dinâmica Molecular , Neuraminidase/metabolismo , Polissacarídeos/metabolismo , Receptores Virais/metabolismo , Sítios de Ligação , Humanos , Vírus da Influenza A Subtipo H1N1/enzimologia , Vírus da Influenza A Subtipo H3N2/enzimologia , Virus da Influenza A Subtipo H5N1/enzimologia , Subtipo H7N9 do Vírus da Influenza A/enzimologia , Influenza Humana/virologia , Neuraminidase/química , Ligação Proteica , Conformação Proteica , Receptores Virais/química , Especificidade por Substrato , Replicação Viral
16.
Org Biomol Chem ; 17(3): 541-554, 2019 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-30574639

RESUMO

New alternative chiral derivatizing agents, ß-keto-anthracene adducts (KAAs), were accomplished and the influence of aromatic moieties at the α-carbon position for elucidation of the absolute configuration of chiral secondary alcohols via NMR was studied. The α-benzoyl substituted KAAs strongly enhance the anisotropic effect which produced greater ΔδRS values than other conventional reagents. We propose a simplified model to describe the conformations and to assign the absolute configuration in several chiral alcohol samples.

17.
Phys Chem Chem Phys ; 20(32): 21194-21203, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30083668

RESUMO

We used density functional theory (DFT) to investigate hydrogen adsorption and diffusion on platinum-decorated carbon nanocones (Pt-CNCs). The curvature presented in the conical section of CNC materials affects the Pt binding stability. The role of Pt atoms as an active catalyst for H2 adsorption and dissociation has been investigated in perfect Pt-4CNC and defect Pt-v4CNC systems. Then, the spillover mechanism of dissociated hydrogen atoms in Pt-v4CNC is explored via two reaction steps: (i) H-migration from Pt to carbon atoms and (ii) H-diffusion via the C-C route throughout the CNC surface. Our results show that the presence of the hydrogen atom on the Pt catalyst can efficiently induce the H-diffusion process through the C-C surface, and the Pt-H bond significantly facilitates the H-migration from C-H bonds near to the active Pt catalyst to the adjacent carbon atom with an energy barrier <0.5 eV under ambient conditions. Altogether, the theoretical results support the concept of the spillover mechanism as a key process for enhancing the hydrogen storage capacity of metal-decorated CNCs. These results improve our understanding about the hydrogen spillover mechanism and the catalytic reactions which are very important for the development of highly efficient hydrogen storage materials.

18.
J Phys Chem A ; 122(37): 7284-7292, 2018 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-30160478

RESUMO

UV/vis absorption and emission spectra of recently synthesized chiral carbon nanorings were simulated using first-principles-based molecular dynamics and time-dependent density functional theory (TD-DFT). The chiral carbon nanorings are derivatives of the [ n]cycloparaphenylene ([ n]CPP) macrocycles, containing an acene unit such as naphthalene, ([ n]CPPN), anthracene ([ n]CPPA), and tetracene ([ n]CPPT), in addition to n paraphenylene units. In order to study the effect of increasing molecular size on absorption and emission spectra, we investigated the cases where n = 6 and 8. Frontier molecular orbital analysis was carried out to give insight into the degree of excitation delocalization and its relationship to the predicted absorption spectra. The lowest excited singlet state S1 corresponds to a HOMO-LUMO π-π* transition, which is allowed in all chiral carbon nanorings due to lack of molecular symmetry, in contrast to the forbidden HOMO-LUMO transition in the symmetric [ n]CPP molecules. The S1 absorption peak exhibits a blue-shift with increasing number of paraphenylene units in particular for [ n]CPPN and [ n]CPPA and less so in the case of [ n]CPPT. In the case of CPPN and CPPA, the transition density is mainly localized over a semicircle of the macrocycle with the acene unit in its center but is strongly localized on the tetracene unit in the case of CPPT. Molecular dynamics simulations performed on the excited state potential energy surfaces reveal red-shifted emission of these chiral carbon nanorings when the size of the π-conjugated acene units is increased, although the characteristic [ n]CPP blue-shift with increasing paraphenylene unit number n remains apparent. The anomalous emission blue-shift is caused by the excited state bending and torsional motions that stabilize the π HOMO and destabilize the π* LUMO, resulting in an increasing HOMO-LUMO gap.

19.
Sci Rep ; 8(1): 10089, 2018 07 04.
Artigo em Inglês | MEDLINE | ID: mdl-29973632

RESUMO

Two series of novel dyes were designed based on the multipolar structures of the red dye D35 and blue dye DB, by introducing the furan (F), benzene ring (B) and benzo[c]thiophene (BT) groups into the conjugated bridge of D35 in proper order and adjusting the position of diketopyrrolopyrrole(DPP) unit and the incorporation of fluorine in the conjugated bridge of DB, respectively. We performed the quantum chemistry calculation to investigate the ground state and excited properties in a direct correlation with the spectra properties and abilities of losing or accepting electron for the original and designed molecules. Furthermore, the absorption spectra characteristics in consideration of the aggregation of dyes on the TiO2 layer and intermolecular charge transfer rate of the dimers were calculated. The obtained results indicate that the larger intermolecular charge transfer rate leads to the poor photoelectrical properties of the dyes, and the designed dyes D35-3 and DB-2 would exhibit the best photoelectrical properties among the investigated dyes due to their lower energy gaps, widened absorption spectra and prominent charge transfer properties.

20.
Sci Pharm ; 86(1)2018 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-29385698

RESUMO

Pinostrobin (PNS) belongs to the flavanone subclass of flavonoids which shows several biological activities such as anti-inflammatory, anti-cancerogenic, anti-viral and anti-oxidative effects. Similar to other flavonoids, PNS has a quite low water solubility. The purpose of this work is to improve the solubility and the biological activities of PNS by forming inclusion complexes with ß-cyclodextrin (ßCD) and its derivatives, heptakis-(2,6-di-O-methyl)-ß-cyclodextrin (2,6-DMßCD) and (2-hydroxypropyl)-ß-cyclodextrin (HPßCD). The AL-type diagram of the phase solubility studies of PNS exhibited the formed inclusion complexes with the 1:1 molar ratio. Inclusion complexes were prepared by the freeze-drying method and were characterized by differential scanning calorimetry (DSC). Two-dimensional nuclear magnetic resonance (2D-NMR) and steered molecular dynamics (SMD) simulation revealed two different binding modes of PNS, i.e., its phenyl- (P-PNS) and chromone- (C-PNS) rings preferably inserted into the cavity of ßCD derivatives whilst only one orientation of PNS, where the C-PNS ring is inside the cavity, was detected in the case of the parental ßCD. All PNS/ßCDs complexes had a higher dissolution rate than free PNS. Both PNS and its complexes significantly exerted a lowering effect on the IL-6 secretion in LPS-stimulated macrophages and showed a moderate cytotoxic effect against MCF-7 and HeLa cancer cell lines in vitro.

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