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IR Cavity Ringdown Spectroscopy and Density Functional Theory for Jet-Cooled Pyrrolea??Cyclopentanone Binary Clusters: Effect of Pseudorotation on Na??H?·?·?·Oa??C Hydrogen Bonds
摘要： The geometry and energetics of the N-H…O=C hydrogen bond (H-bond) are important to understand the stability and flexibility of biomolecules, such as protein and DNA. Jet-cooled pyrrole-cyclopentanone (Py-Cp) binary clusters are appropriate models to investigate the N-H…O=C H-bond from a microscopic point of view. In this study, NH stretching vibrations of the Py-Cp binary clusters were observed by IR cavity ringdown spectroscopy. Furthermore, density functional theory calculations revealed geometric structures, harmonic vibrations, intermolecular energies, and donor-acceptor interactions for various sizes of binary clusters. The IR spectra of the Py-Cp binary clusters were measured under various conditions of the vapor pressures of Py and Cp in He buffer gas for a supersonic expansion. The dependence of the IR band intensities on the vapor pressure provides vibrational assignments of the NH stretching vibrations, which were reproduced by calculated frequencies of Py1-Cp1, Py1-Cp2, and Py2-Cp1. An admixture of Ar in He buffer gas for a supersonic expansion was also applied to produce Py1-Cp2 in order to differentiate several NH stretches of isomeric structures due to the pseudorotation of Cp molecules. Py1-Cp1 is formed by the N-H…O=C H-bond. Py1-Cp2 has a cyclic structure that is formed by the N-H…O=C H-bond and stacking interactions among Py and two Cp molecules. Py2-Cp1 also has a cyclic structure that is formed by not only the N-H…O=C H-bond, but also a N-H…π H-bond between two Py molecules and a stacking interaction between Py and Cp. A comparison of the H-bond geometries between Py2-Cp1 and the corresponding pyrrole-acetone binary cluster reveals that the stacking interaction between Py and Cp strengthens the N-H…O=C and N-H…π H-bonds through a cooperative effect.
关键词： Density Functional Theory,Cyclopentanone,Spectroscopy,Quantum Chemistry,Pyrrole,IR Cavity Ringdown Spectroscopy,Hydrogen Bonds,Molecular Structure,Pseudorotation
更新于2025-09-19 17:13:59
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Hydrogen Bonds and Molecular Orientations of Supramolecular Structure between Barbituric Acid and Melamine Derivative at the Air/Water Interface Revealed by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
摘要： We studied the supramolecular structure between barbituric acid (pyrimidine-2,4,6(1H,3H,5H)-trione, BA) and an amphiphilic melamine derivative at the air/water interface by heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy. HD-VSFG measurements in situ showed a positive broad band from 2300 to 2950 cm?1. By comparing the experimental results with ab initio molecular dynamics (AIMD) simulations, we assigned the broad band to the NH stretching modes of BA strongly hydrogen-bonded to the melamine derivative. In addition, we report in situ HD-VSFG spectra of the interfacial supramolecular structure in the CO stretching region. Two CO stretching bands were identified. On the basis of the signs of the C=O bands, we uniquely determined the orientation of BA. The strong hydrogen bonds and the molecular orientations are direct evidence for the supramolecular structure based on complementary hydrogen bonds at the air/water interface.
关键词： Supramolecular Structure,Molecular Orientations,Barbituric Acid,Melamine Derivative,Hydrogen Bonds,Air/Water Interface,Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
更新于2025-09-19 17:13:59
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Micro-Mechanism of Silicon-Based Waveguide Surface Smoothing in Hydrogen Annealing
摘要： The micro-mechanism of the silicon-based waveguide surface smoothing is investigated systematically to explore the effects of silicon-hydrogen bonds on high-temperature hydrogen annealing waveguides. The effect of silicon-hydrogen bonds on the surface migration movement of silicon atoms and the waveguide surface topography are revealed. The micro-migration from an upper state to a lower state of silicon atoms is driven by silicon-hydrogen bonding, which is the key to ameliorate the rough surface morphology of the silicon-based waveguide. The process of hydrogen annealing is experimentally validated based on the simulated parameters. The surface roughness declines from 1.523 nm to 0.461 nm.
关键词： surface smoothing,silicon-based waveguide,silicon-hydrogen bonds,hydrogen annealing,surface roughness
更新于2025-09-16 10:30:52
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Electro-active nanofibers of a tetrathiafulvalene derivative with amide hydrogen bonds as a dopant-free hole transport material for perovskite solar cells
摘要： A tetrathiafulvalene derivative containing two amide units for intermolecular hydrogen bonds (Bis-amide-TTF) was found to form supramolecular assemblies, in which intermolecular TTF cores were stacked with each other. The electrical conductivity of Bis-amide-TTF-based film was 1.28 × 10?5 S cm?1, which was greater than that of spiro-OMeTAD doped with lithium salt and t-butylpyridine (8.37 × 10?6 S cm?1). Bis-amide-TTF was applied as a hole transport material (HTM) for perovskite solar cells (PSCs). The Bis-amide-TTF film has a deeper HOMO level than that of spiro-OMeTAD, leading to an increased open-circuit voltage of the PSCs. The power conversion efficiency of 14.5% with a short-circuit current density (Jsc) of 19.8 mA cm?2, an open-circuit voltage (Voc) of 1.11 V, and a fill factor (FF) of 66% was achieved for PSCs fabricated with the dopant-free Bis-amide-TTF-based HTM, which was comparable to that obtained with spiro-OMeTAD with the dopants (15.5%).
关键词： Hole transport materials,Nanofibers,Hydrogen bonds,Tetrathiafulvalene,Dopant free,Perovskite solar cells
更新于2025-09-12 10:27:22
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Perylene Diimide‐Based Nonfullerene Polymer Solar Cells with over 11% Efficiency Fabricated by Smart Molecular Design and Supramolecular Morphology Optimization
摘要： A series of perylene diimide (PDI) derivatives, TPP-PDI, TPO-PDI, and TPS-PDI, are developed for nonfullerene polymer solar cells (NF-PSCs) by flaking three PDI skeletons around 3D central cores with different configurations and electronic states, such as triphenylphosphine (TPP), triphenylphosphine monoxide (TPO), and triphenylphosphine sulfide (TPS). These small-molecule acceptors have a “three-wing propeller” structure due to their similar backbones. By changing the electron density of phosphorus atoms through oxidation and sulfuration, the “folding-back” strength is decreased, resulting in a less twisted molecular conformation. The stronger electron-withdrawing ability of the oxygen atom affords TPO-PDI the least twisted conformation, which enhances the crystallinity of this complex. NF-PSCs based on PTTEA:TPO-PDI exhibit a high power conversion efficiency (PCE) of 8.65%. Ultimately, the joint “molecular lock” effect arising from OH???F and OH???OP supramolecular interactions is achieved by introducing 4,4′-biphenol as an additive, which successfully promotes fibril-like phase separation and blend morphology optimization to generate the highest PCE of 11.01%, which is currently the highest value recorded for NF-PSCs based on PDI acceptors.
关键词： triphenylphosphine oxide cores,nonfullerene polymer solar cells,molecular locks,hydrogen bonds,perylene diimide acceptors
更新于2025-09-11 14:15:04
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Controlled Growth of Ag Nanocrystals in a H‐Bonded Open Framework
摘要： A procedure that enabled rational access to the first example of hybrid material made of NPs grown within a H-bonded framework is reported. To avoid competitive reactions with the framework units, the metal precursor was chemically trapped in the porous structure and subsequently photo-reduced to afford the hybrid material Ag@SPA-2, which consists of Ag NPs of nanometric sizes (< 15 nm) homogeneously distributed in the crystals of the host material. In a subsequent step, taking advantage of the porous matrix the silver NPs have been transformed in situ to Ag2S NP by simple infiltration of H2S. The supramolecular network is shown to play an important role in stabilizing the inorganic nanomaterials and thus in controlling their growth.
关键词： crystal engineering,nanoparticles,silver,hydrogen bonds,organic–inorganic hybrid composites
更新于2025-09-11 14:15:04
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A distorted lactam unit with intramolecular hydrogen bonds as the electron donor of polymer solar cells
摘要： A novel distorted lactam motif, namely 4,40-dialkyl-[6,60-bithieno[3,2-b]pyridine]-5,50(4H,40H)-dione (BTP), could lock itself by intramolecular hydrogen bonds. In view of the potential of the motif, two D–A conjugated polymers, PBDT-BTP-HD and PBDT-BTP-OD, with two different long side chains consisting of 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b0]dithiophene (BDT) as a donor unit and BTP as an acceptor unit were designed and synthesized. Furthermore, the photophysical, electrochemical and photovoltaic properties of both polymers were investigated. The morphologies and molecular ordering of the neat polymers and blend films were also probed to relate the side chain structures with aggregation states and device parameters. The device based on PBDT-BTP-OD with IT-M exhibited a power conversion efficiency of up to 9.54% thanks to the synergistic effect of the building blocks and side-chain engineering. As a result, it is successfully demonstrated that the novel distorted lactam BTP is a promising building block in organic solar cells.
关键词： side-chain engineering,intramolecular hydrogen bonds,electron donor,distorted lactam,polymer solar cells
更新于2025-09-11 14:15:04
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Infrared Spectra for Alfa Fibers Treated with Thymol
摘要： In this work, we attempt to analyze the hydrogen bond network of cellulose by comparing the 2nd derivative infrared spectra of alfa fiber treated with different concentrations of thymol. It was proved, from this study, that the 2nd derivative infrared spectrum is a useful method for identifying the least changes incurred in the cellulosic supramolecular structure. It can be considered as an effective method to gain further insight on OH bond system of cellulosic materials and to clarify some grey areas in terms of infrared band assignment. The careful analysis of 2nd derivative infrared spectra of untreated and thymol treated alfa fibers revealed an increase in band intensity related to both intermolecular and intramolecular hydrogen bonds and a decrease in bands related to free hydroxyl groups.
关键词： Alfa fiber,FTIR spectrum,Cellulose,Hydrogen bonds,Thymol
更新于2025-09-10 09:29:36
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Mapping corrosion with hyperspectral imaging
摘要： Hydrogen bonds are one reason for water’s unique boiling and freezing behavior and other properties. But scientists have debated for decades whether dimers of hydrogen sulfide, water’s smelly triatomic cousin, also sport hydrogen bonds. Now, Elangannan Arunan of the Indian Institute of Science and colleagues report they have found experimental evidence that hydrogen bonds do indeed hold H2S dimers together. Water’s four hydrogen bonds (via two H atoms and two lone electron pairs) are evident in ice’s tetrahedral structure, but in solid H2S, each molecule is surrounded instead by a shell of 12 others. That suggested to some that H2S does not hydrogen bond. Using microwave spectroscopy, Arunan’s group detected rotational energy barriers in the dimer below about 60 °C that they say indicate the presence of hydrogen bonds. Computational chemists have reached the same conclusion. Arunan explains that at higher temperatures, those bonds break and re-form too quickly to be detected via spectroscopy. He adds that the observation that the distance between the H and S atoms is smaller than their combined van der Waals radii and that the S–H–S angle is nearly 180° further confirms hydrogen bonding.
关键词： computational chemistry,microwave spectroscopy,Hydrogen bonds,H2S dimer
更新于2025-09-09 09:28:46
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Transient Glass Formation around a Quadrupolar Photoexcited Dye in a Strongly H-Bonding Liquid Observed by Transient 2D-IR Spectroscopy
摘要： A photoexcited quadrupolar dye is directly observed using transient 2D-IR spectroscopy. Upon solvent-induced symmetry breaking, the H-bond accepting abilities of the two nitrile end-groups change drastically, and in extreme protic (‘superprotic’) solvents, a tight H-bond complex forms at one end. The time evolution of the 2D C≡N lineshape in methanol points to rapid, 2-3 ps, spectral diffusion due to fluctuations of the H-bonding network. Similar behaviour is observed in a superprotic solvent shortly after photoexcitation of the dye. However, at later time, the completely inhomogeneous band does not exhibit spectral diffusion for at least 5 ps, pointing to a glass-like environment around one side of the dye. About half of the excited dyes show this behaviour attributed to the tight H-bond complex, whereas the others are loosely bound. A weak cross peak these excited state sub- indicates partial exchange between populations.
关键词： charge transfer,symmetry breaking,ultrafast spectroscopy,Hydrogen bonds,solvation dynamics
更新于2025-09-09 09:28:46