- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Hydrogen bonding between ethynyl aromates and triethylamine: IR spectroscopic and computational study
摘要： Ethynylpyridines (EPs) and ethynylbenzene (EB) are multifunctional systems able to participate in hydrogen-bonded complexes as both donors and acceptors of the H-atom. Their structures and stabilities are mainly a function of the hydrogen-bonding properties of the partner in the complex and the surroundings in which the complexation occurs. In this paper, IR spectroscopy and quantum chemical calculations are employed to characterize hydrogen-bonded complexes of 2- and 3-EP and EB with triethylamine (TEA) in tetrachloroethene (C2Cl4) solution. The formation of ≡C?H···N hydrogen bonds is experimentally confirmed by the appearance of TEA concentration-dependent signals in the IR spectra of the EPs and EB. Along with the signals due to unassociated ≡C?H and C≡C oscillators (2-EP: 3308 cm–1 and 2120 cm–1; 3-EP: 3308 cm–1 and 2116 cm–1; EB: 3313 cm–1 and 2113 cm–1) weak, red-shifted signals arise at ~3215 ± 5 cm–1 and ~2105 ± 5 cm–1 which are assigned to the stretching vibrations of hydrogen-bonded ≡C?H··· and C≡C··· oscillators, respectively. This result is at variance with those of previous investigations of EB and TEA in the gas phase. In the 2-EP···TEA complex these bands remain at the same position with increasing TEA concentration. However, in the 3-EP···TEA and EB···TEA complexes the ≡C?H··· stretching band demonstrates a slightly reduced red-shift as the TEA concentration increases, whereas the C≡C··· stretching band absorbs at the same wavenumber in the investigated TEA concentration range. The results of B3LYP-D3 calculations indicate that complexes with more or less linear ≡C?H···N intermolecular hydrogen bonds are more stable than other, dispersion-driven complexes. Complexes with the Cs symmetrical TEA conformer are predicted to have larger binding energy than those formed with the C3 and C1 symmetrical conformers. The predicted IR spectral shifts are slightly different for complexes with the three different TEA conformers. Association constants of hydrogen-bonded complexes at 26 °C are estimated to be ~0.1 mol–1 dm3.
关键词： triethylamine,hydrogen bonding,ethynyl aromates,IR spectroscopy,B3LYP-D3 calculations
更新于2025-09-23 15:21:01
-
The role of interfacial H-bonding in electrical properties of UV-cured resin filled with hydroxylated Al2O3 nanoparticles
摘要： Surface hydroxylation of crude Al2O3 (c-Al2O3) nanoparticles by H2O2 was conducted to tailor the electrical properties of UV-cured resin. The hydroxyl groups on Al2O3 particles were designed to establish hydrogen bonding between hydroxyl and carboxyl with that of UV/c-Al2O3 composites at the same filler content. It was found that the addition of 0.5 wt % h-Al2O3 increases the AC breakdown strength and volume resistivity by 15.5 % and 367.9 %, respectively. Our results suggest that the hydroxylation is an efficient way to improve the electrical properties of UV-cured resin nanocomposites, thus promoting stereolithography 3D printing in application of electrical and electronic field.
关键词： Stereolithography,Interfacial region,Hydrogen bonding,Nanocomposites,Interfacial strength,Trap levels,Electrical properties
更新于2025-09-23 15:19:57
-
Understanding the effects of chlorine ion on water structure from a Raman spectroscopic investigation up to 573?K
摘要： The OH stretch band features on Raman spectra of aqueous KCl?H2O solutions have been investigated at temperatures (T) up to 573 K. KCl greatly reduces the relative intensity of the shoulder at ~3245 cm–1 and the band width, but these effects are slightly reversed at temperatures over ~513 K. Also, KCl causes a blue shift (T < 433 K) but a red shift (T > 433 K) of the main peak. These spectral features are interpreted that Cl? breaks the tetrahedral hydrogen bonding (HB) structure and bonds to water molecules with the non-tetrahedral HB configurations. The single donor is likely the preferred configuration between the water molecules in the Cl? hydration shells. Cl? tends to promote the HB degree in solutions at T > 433 K.
关键词： Temperature,Chlorine ion,Hydrogen bonding,Raman spectroscopy,Water structure
更新于2025-09-19 17:15:36
-
Hydrogen bonding promoted simple and clean photo-induced reduction of C–X bond with isopropanol
摘要： We herein report a simple and clean photo-induced metal-free reduction of C–X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C–I, C–Br and C–Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C–X···H–O hydrogen bonding to decrease the activation energy.
关键词： metal-free,isopropanol,DFT calculation,hydrogen bonding,photo-induced reduction,C–X bond
更新于2025-09-19 17:15:36
-
Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2
摘要： The first event of the channelrhodopsin-2 (ChR2) photocycle, i.e. trans-to-cis photoisomerization, is studied by means of quantum mechanics/molecular mechanics, taking into account the flexible retinal environment in the ground state. By treating the chromophore at the ab initio multiconfigurational level of theory, we can rationalize the experimental findings based on pump–probe spectroscopy, explaining the different and more complex scenario found for ChR2 in comparison to other rhodopsins. In particular, we find that depending on the hydrogen bonding pattern, different excited states are involved, hence making it possible to suggest one pattern as the most productive. Moreover, after photoisomerization the structure of the first photocycle intermediate, P500, is characterized by simulating the infrared spectrum and compared to available experimental data. This was obtained by extensive molecular dynamics, where the chromophore is described by a semi-empirical method based on density functional theory. The results clearly identify which counterion is responsible for accepting the proton from the retinal Schiff base: the side chain of the glutamic acid E123.
关键词： FTIR spectroscopy,quantum mechanics/molecular mechanics,retinal Schiff base,photoisomerization,channelrhodopsin-2,hydrogen bonding,excited states,molecular dynamics
更新于2025-09-19 17:15:36
-
Association of 1-hexanol in mixtures with n-hexane: Dielectric, near-infrared and DFT studies
摘要： Association of 1-hexanol in n-hexane has been studied by measurements of nonlinear dielectric effect (NDE) and near-infrared (NIR) spectroscopy. Besides, the dipole moments of selected open and cyclic associates were determined by DFT (density functional theory) calculations. All measurements were performed in the whole range of mole fractions with a step of 0.1. From numerical fitting of the dielectric data we obtained populations of all species present in the mixture. Our results do not support common opinion about the exceptional role of cyclic tetramers. The most abundant cyclic species are trimers and population of the cyclic associates rapidly decreases with increasing size of associates. The variations in population of open associates are more complex and for mole fractions of 1-hexanol greater than 0.1 the relationships have a maximum, which shifts towards higher associates. In pure 1-hexanol this maximum is close to seven. From analysis of the dielectric data it results that at lower alcohol content dominate the cyclic species. When the concentration of 1-hexanol increases the equilibrium shifts towards formation of the linear associates. From NIR spectra we determined the overall population of the free OH in monomers and open associates. Next, these values were used for estimation of an average length of the open associates. It appears that an averaged size of the open associates determined from NIR spectra is higher than that from the dielectric data and these differences are more pronounced when the concentration of 1-hexanol increases. We discuss possible explanations of this observation. Assuming that the actual size of the open associates is between those obtained from both methods, one can estimate that the size of open associates is ranging from 3 to 15 in pure 1-hexanol. It seems that the higher associates are stabilized by interaction of the aliphatic chains.
关键词： NIR spectroscopy,1-hexanol,DFT,hydrogen bonding,associations,non-linear dielectric effect
更新于2025-09-19 17:15:36
-
New perspective on the fluorescence and sensing mechanism of TNP chemosensor 2-(4,5-bis(4-chlorophenyl)-1H-imidazol-2-yl)-4-chlorolphenol
摘要： For TNP chemosensor 2-(4,5-Bis(4-Chlorophenyl)-1H-Imidazol-2-yl)-4-Chlorolphenol (HPICI), previous thought with no theoretical basis was that excited-state intramolecular proton transfer (ESIPT) process and the ground-state HPICI-TNP complex are mainly responsible for its fluorescence emission and the detection of TNP. However, this interpretation has been proved to be wrong by the present theoretical DFT/TDDFT explorations. Actually, the strong fluorescence of HPICI is mainly induced by the local excitation of the enol form HPICI(E) without ESIPT, and the fluorescence quenching by TNP is due to the photo-induced electron transfer (PET) process together with the cooperative effect of hydrogen-bonding interaction and π-π stacking interaction coexisting in the HPICI-TNP complex. The strengthened excited-state hydrogen bond promotes the PET process, thus facilitates the fluorescence quenching. This mechanism is proposed on the basis of the theoretical analyses on molecule geometry, binding energy, Gibbs free energy, electronic transitions, and frontier molecular orbitals (FMOs).
关键词： Fluorescence emission,Fluorescence quenching,Photo-induced electron transfer,Hydrogen-bonding interaction,Dynamical sensing mechanism,π-π stacking interaction
更新于2025-09-19 17:15:36
-
Selective fluorescence sensing of H <sub/>2</sub> PO <sub/>4</sub><sup>a??</sup> by the anion induced formation of self-assembled supramolecular polymers
摘要： The utilization of anions to induce the formation of self-assembled supramolecular polymers in solution is an undeveloped area of host–guest chemistry. We report in this manuscript a comparative study of two tripodal anion receptors by hydrogen or halogen bonding interactions to form self-assembled supramolecular structures induced by the presence of anions. DOSY NMR and DLS experiments provided evidence for the formation of supramolecular structures in solution in both halogen and hydrogen bond donors with H2PO4? anions. The nucleation and elongation constants obtained using the thermodynamic model indicate that the polymers grow following an isodesmic mechanism. Emission studies demonstrate that only the formation of the supramolecular polymer between the halogen bond donor receptor and H2PO4? anions results in the appearance of the excimer emission band.
关键词： halogen bonding,hydrogen bonding,DLS,anion receptors,DOSY NMR,excimer emission,supramolecular polymers
更新于2025-09-19 17:13:59
-
Photodetector Based on Spontaneously Grown Strongly Coupled MAPbBr3/N-rGO Hybrids Showing an Enhanced Performance
摘要： Recently, metal-halide perovskites have emerged as a candidate for optoelectronic applications such as photodetectors. However, the poor device performance and instability have limited their future commercialization. We herein report the spontaneous growth of perovskite/N-rGO hybrid structures using a facile solution method and their application for photodetectors. In the hybrid structures, perovskites were homogeneously wrapped by N-rGO sheets through strong hydrogen bonding. The strongly coupled N-rGOs facilitate the charge carrier transportation across the perovskite crystals, but also distort the surface lattice of the perovskite creating potential barrier for charge transfer. We optimize the addition of N-rGO in the hybrid structures to balance the interfacial structural distortion and the inter-crystal conductivity. A high-performance photodetection up to 3 × 104 A/W, external quantum efficiency (EQE) exceeding 105 % and detectivity up to 1012 Jones were achieved in the optimal device with the weight ratio between perovskites and N-rGO to be 8:1.5. The underlying mechanism behind the optimal N-rGO addition ratio in the hybrids has also been rationalized via time-resolved spectroscopic studies as a reference for future application.
关键词： hydrogen bonding,perovskite/N-rGO,hybrid material,photodetector,time-resolved spectroscopy
更新于2025-09-12 10:27:22
-
Fluorescence coupled with electrochemical approach at the bulk and the interface region of hydrogen-bonding self assemblies of urea derivatives with DDP dye in aqueous solution
摘要： Photophysical and electrochemical techniques were employed to hydrogen-bonding self assemblies forming solutes (Urea, Dimethylurea and Tetramethylurea) in the presence of 4-dicyanomethylene 2, 6-dimethyl-4H-pyran (DDP) dye. Addition of urea derivatives to DDP dye (Intramolecular Charge Transfer (ICT)) results in a fluorescence enhancement accompanied with a significant shift. Fluorescence lifetime behavior exhibits a tri-exponential decay with a large variation in the fluorescence lifetime and relative amplitude distribution. The co-existence of three different fluorescence lifetime components of DDP with urea derivatives signifies the existence of heterogeneous micro environment. The dye is surrounded by varying proportion of solute and water molecules are established from fluorescence lifetime studies. Urea derivatives govern the excited state characteristics of DDP dye resulting in the formation and promotion of different microenvironment which are clearly distinguishable. The existence of multi environment attributed to urea-water structural behaviour is authenticated by electrochemical impedance spectral studies (EIS). A large variation in the contour pattern, shape and intensity in 3D fluorescence contour spectra of dye with urea validate the existence of dye in a heterogeneous micro environment. The hydrophobicity of urea derivatives along with the hydrogen-bonding properties of urea-water and urea-urea influence the photophysical and electrochemical nature of dye is emphasized.
关键词： Hydrogen-bonding,Urea derivatives,Fluorescence lifetime,Electrochemical impedance spectra,Fluorescence emission,DDP dye
更新于2025-09-12 10:27:22