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The Influence of Ceramic Far-Infrared Ray (cFIR) Irradiation on Water Hydrogen Bonding and its Related Chemo-physical Properties
摘要： The property of water is highly related to the earth's environment and climate change. The fundamental dynamical process of water is include formation and breaking of hydrogen bonds. This dynamic process, so far, is still poorly understood. We investigated weakening of the hydrogen bonds of water after ceramic Far-Infrared Ray (cFIR) irradiation and the resulting effects on physical and chemical properties of water. In this study, the Fourier transform infrared spectroscopy (FT-IR) was used to explore hydrogen bonding change of cFIR-irradiated water; in addition, capillary viscometers, Gas Chromatographs (GC), Differential Scanning Calorimetry (DSC), contact angles, Franz cells, High-Performance Liquid Chromatography (HPLC), and capillary electrophoresis analysis were used to evaluate its physical characteristics, such as viscosity, volatility, temperatures of water crystallization, surface tension, diffusion, hydrogen peroxide dissociation, solubility of solid particles, and changes in pH of acetic acid. The cFIR treated water decreased in viscosity and surface tension (contact angles), but increased in the solubility of solid particles, hydrogen peroxide dissociation, temperatures of water crystallization, and acidity of acetic acid. The weakening of water hydrogen bonds caused by cFIR irradiation is correspondent with our previous medical-biological studies on cFIR.
关键词： Hydrogen bonds,Fourier transform infrared spectroscopy (FT-IR),Contact angle,Ceramic far infrared ray (cFIR),Irradiation water,Solubility,Volatility
更新于2025-09-23 15:23:52
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Photophysical Properties of Phthalimide and Pyromellitic Diimide Tethered Imidazolium Nitrophenolate Salts
摘要： Structural aspects of the salt of 2-(3-(1H-imidazol-1-yl)propyl) isoindoline-1,3-dione (L1) with 2,4,6-trinitrophenol as well as the salts of N,N’-bis(3-imidazol-1-yl-propyl)-pyromelliticdiimide (L2) with 2,4-dinitrophenol (H24dnp) and 2,4,6-trinitrophenol (H246tnp) are reported along with the solid and solution studies on the photophysical properties of these salts. The fluorescence emission of the L1 and L2 are quenched by H24dnp and H246tnp both in solid and in solution. In solution the L1 has comparable binding constant with H24dnp and H246tnp but the relative ability to quench the fluorescence emission of L1 by H24dnp is less than the quenching abilities of the H246tnp. These two nitrophenols independently do not distinguish the L1 from L2 but the extent of quenching caused independently by the H24dnp or H246tnp on L1 or L2 make them easily distinguishable. Addition of water quenches the fluorescence emission of L1 and L2; but the addition of water to solution of the nitrophenolate salts result in the recovery of fluorescence emissions from the quenched states. The salts in solid state have short emission life-times. The PET effect prominently caused by mineral acids on L1 or L2 is not observed in the nitrophenolate salts. In solid state the O-π interactions contributed to stacking of the aromatic in the 2,4,6-trinitrophenolate salt of L2, hence it is non-fluorescent.
关键词： Binding of imidazole,Charge-assisted hydrogen bonds,Fluorescence,Cyclic imide,Nitrophenol derivatives
更新于2025-09-23 15:23:52
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Molecular Identification, Bond Order Discrimination, and Apparent Intermolecular Features in Atomic Force Microscopy Studied with a Charge Density Based Method
摘要： We introduce an efficient method to simulate high-resolution atomic force microscopy (HR-AFM) images with CO probes. Our model explicitly takes into account the charge densities of the sample and the probe for the calculation of the short-range (SR) interaction and retains ab initio accuracy with only two parameters, that are essentially universal, independent of the number of chemical species and the complexity of the bonding topology. The application to molecular images shows a strong dependence on the stoichiometry and bonding configuration that precludes the chemical identification of individual atoms based on local force–distance curves. However, we have identified features in the 2D images and 3D force maps that reflect the highly anisotropic spatial decay of the molecular charge density and provide a way towards molecular identification. The model treats SR and electrostatics interactions on an equal footing and correctly pinpoints the Pauli repulsion as the underlying interaction responsible for the bond order discrimination in C60. Finally, we settle the controversy regarding the origin of the intermolecular features, discarding the effect of the charge redistribution associated with the H bonds, and linking them with the overlap of the wave functions of the atoms that constitute the bond. This overlap creates saddle regions in the potential energy landscape that are sensed by the probe.
关键词： tip functionalization,DFT,chemical identification,CO molecule,hydrogen bonds,non–contact atomic force microscopy,bond order
更新于2025-09-23 15:23:52
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Enantioselective Visible Light-mediated Formation of 3-Cyclopropylquinolones via Triplet-sensitized Deracemization
摘要： 3-Allyl-substituted quinolones undergo a triplet-sensitized di-π-methane rearrangement to the corresponding 3-cyclopropylquinolones upon irradiation with visible light (λ = 420 nm). A chiral hydrogen bonding sensitizer (10 mol%) was shown to promote the reaction enantioselectively (88-96% yield, 32-55% ee). Surprisingly, it was found that the enantiodifferentiation does not occur at the state of initial product formation but that it is the result of a deracemization event. The individual parameters that control the distribution of enantiomers in the photostationary state have been identified.
关键词： enantioselectivity,small ring systems,photochemistry,hydrogen bonds,sensitizers,chiral resolution
更新于2025-09-23 15:22:29
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Incremental Introduction of Organocatalytic Activity into Conformationally Engineered Porphyrins
摘要： To study the correlation of macrocycle nonplanarity and catalytic activity of free base porphyrins in detail, a series of six tetraphenylporphyrins with graded degree of β-ethyl substitution ('H2EtxTPPs' 1–6; x = 0, 2, 4, 6, 8) was applied in organocatalyzed reactions. They display incrementally increasing nonplanarity due to repulsive peri-interactions. This creates an out-of-plane vector and better accessibility of the core amine and imine groups as the number of alkyl substituents increases. Following such a molecular engineering approach, the inner core system could be used to activate small molecules as a result of significant saddle distortion. The potential organocatalyst 'H2EtxTPPs' were used in benchmark sulfa-Michael reactions and we found a distinct relationship between nonplanarity and conversion. These observations were attributed to the combined effect of enhanced basicity and increased H-bonding potential that could facilitate bifunctional organocatalysis. Ultimately, density functional theory (DFT) calculations were performed on 1–6 to monitor some electronic properties of the title compounds.
关键词： porphyrins,organocatalysis,hydrogen bonds,molecular engineering,macrocycles
更新于2025-09-23 15:22:29
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Disentangling Coupling Effects in the Infrared Spectra of Liquid Water
摘要： A quantitative characterization of intermolecular and intramolecular couplings that modulate the OH-stretch vibrational band in liquid water has so far remained elusive. Here, we take up this challenge by combining the centroid molecular dynamics (CMD) formalism, which accounts for nuclear quantum effects, with the MB-pol potential energy function, which accurately reproduces the properties of water across all phases, to model the infrared (IR) spectra of various isotopic water solutions with different levels of vibrational couplings, including those that cannot be probed experimentally. Analysis of the different IR OH-stretch lineshapes provides direct evidence for the partially quantum-mechanical nature of hydrogen bonds in liquid water, which is emphasized by synergistic effects associated with intermolecular coupling and many-body electrostatic interactions. Furthermore, we quantitatively demonstrate that intramolecular coupling, which results in Fermi resonances due to the mixing between HOH-bend overtones and OH-stretch fundamentals, are responsible for the shoulder located at ～3250 cm?1 of the IR OH-stretch band of liquid water.
关键词： liquid water,nuclear quantum effects,infrared spectra,Fermi resonances,centroid molecular dynamics,hydrogen bonds,intramolecular coupling,intermolecular coupling,MB-pol potential energy function
更新于2025-09-23 15:21:21
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ON THE COOPERATIVITY EFFECT IN WATSON&CRICK AND WOBBLE PAIRS FOR A HALOURACIL SERIES AND ITS POTENTIAL QUANTITATIVE APPLICATION STUDIED THROUGH SERS
摘要： The nature of the cooperativity effect of hydrogen bonds in Watson & Crick and wobble base pairs formed with thymine, uracil and its 5-halogenated derivatives (5-fluoro, -chloro and -bromouracil) have been studied through SERS, and using chemometric tools to process data and extract relevant information. Remarkable differences between the two kinds of pairs were clearly observed and the behavior correlated to the withdrawing character of different substituents at the 5- position of uracil was verified. Multivariate analyses have also unveiled information about pair’s stability and a stronger cooperativity effect seems to rule the Watson & Crick pairs when compared to wobble pairs. Defined patterns in the behavior of Watson & Crick pairs allowed the design of an indirect methodology for quantifying 5-bromouracil using a PLS method with variable selection. LOD values of 0.037 and 0.112 mmol L-1 in absence and presence of structurally similar interferences were reached, while its direct SERS quantification is only possible at around 45 mmol L-1.
关键词： SERS,5-halogenated derivatives,Watson & Crick pairs,wobble pairs,multivariate analyses,quantitative application,chemometric tools,cooperativity effect,hydrogen bonds
更新于2025-09-23 15:21:01
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Towards More Effective, Reversible pH Control by Visible Light Alone: a Thioindigo Photoswitch Undergoing a Strong pKa Modulation by Isomer Specific Hydrogen Bonding
摘要： We have synthesized and characterized a thioindigo photoswitch featuring phenolic residues forming an intramolecular H bond exclusively in the cis isomer. In acetone water mixtures, wavelength dependent photostationary states their extremes of up to 95 % and down to 11 % cis isomers at ca. 580 and 480 nm, respectively. Within a few hours, room temperature thermal isomerization is negligible in neutral and mildly acidic solutions. Protic media decrease trans→cis but increase cis→trans quantum yields. In CD3OD solution, in which light of any wavelength absorbed triggers the latter process almost exclusively, 19F NMR titration provides pKa values of 7.2 (trans) and 5.0 (cis; both rescaled to water) corresponding to a change in dissociation constant of 2.2 orders of magnitude. Future derivatives featuring solubility and reversible photochromism in plain water may provide pH modulation of similar amplitude in a range adjustable by the choice of phenolic substituents.
关键词： thioindigo,acidity,kinetics,hydrogen bonds,photochromism
更新于2025-09-23 15:21:01
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Achieving Dual-Emissive and Time-Dependent Evolutive Organic Afterglow by Bridging Molecules with Weak Intermolecular Hydrogen Bonding
摘要： It is discovered that “bridging” traditional persistent room-temperature phosphorescence (pRTP) dibenzofuran moieties by intermolecular hydrogen bonding can induce interesting photophysical properties. The light-emitting material 4-(4-((4-methoxyphenyl)sulfonyl)phenyl)dibenzo[b,d]furan (SOBF-OMe) is synthesized and excitingly shows novel dual-emissive afterglow material properties in which orange pRTP (at ≈580 nm, 627 ms) from the dibenzofuran moiety and another blue ultralong intermolecular charge transfer emission (≈476 nm, 204 ms, with TADF characteristics) can be detected. Due to the different decay lifetimes, the ratio of the two afterglow emission bands continuously changes. Accordingly, the emission colors are unusually tuned gradually from cold-white to orange during the afterglow decay process. The blue afterglow emission, which relates to intermolecular interactions, is sensitive to mechanical stimuli and the afterglow emission properties of SOBF-OMe (single-emissive or dual-emissive) can easily be manipulated by grinding/fuming. This single-component material is a rare example of a light-emitting compound showing dual-emissive and real-time changing afterglow properties in which a rational bridging strategy via weak intermolecular hydrogen bonding is utilized.
关键词： afterglow emission,dual-emissive,thermally activated delayed fluorescence,intermolecular charge transfer,hydrogen bonds
更新于2025-09-19 17:15:36
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Methyl Made Noncentrosymmetric Stacking: A Promising Organic Single Crystal for Highly Efficient Terahertz-wave Generation
摘要： Regulating secondary bonds in organic compounds is one of the important routes to design practical materials with excellent performances. However, it is still a great challenge to control molecular arrangement and spatial configuration by changing limited substituent groups. Herein, two indolium-based (C19H20NO)+ crystals, centric OHI-CBS and acentric OHI-T were synthesized and grown by evaporation method. An intriguing structural change from centrosymmetric (P21/c) to noncentrosymmetric (Cc) space group was obtained by a simple substitution from chloro- to methyl. Theoretical calculations demonstrate hydrogen bonds and π-π interactions make a dominated contribution to molecular spatial alignment. Meanwhile, OHI-T crystal exhibits prominent nonlinearity about 0.7 times that of the benchmark OH1 crystal, wide band gap (2.47 eV), wide transparency range (504 - 2100 nm), and remarkably efficient output energy among 0.1 - 20 THz region, suggesting it is a potential nonlinear optical media for THz-wave generation. This work realizes the rational crystal structural regulation by simple molecular subsitution and provides a feasible design strategy for other organic optoelectronic functional materials.
关键词： indolium-based crystals,π-π interactions,hydrogen bonds,THz-wave generation,nonlinear optical media
更新于2025-09-19 17:13:59