Intramolecular Hydrogen Bond Improved Durability and Kinetics for Zinc‑Organic Batteries

Organic compounds have the advantages of green sustainability and high designability,but their high solubility leads to poor durability of zinc-organic batteries.Herein,a high-performance quinone-based polymer(H-PNADBQ)material is designed by introducing an intramolecular hydrogen bonding(HB)strategy.The intramolecular HB(C=O⋯N-H)is formed in the reaction of 1,4-benzoquinone and 1,5-naphthalene diamine,which efficiently reduces the H-PNADBQ solubility and enhances its charge transfer in theory.In situ ultraviolet-visible analysis further reveals the insolubility of H-PNADBQ during the electrochemical cycles,enabling high durability at different current densities.Specifically,the H-PNADBQ electrode with high loading(10 mg cm^(-2))performs a long cycling life at 125 mA g^(-1)(>290 cycles).The H-PNADBQ also shows high rate capability(137.1 mAh g^(−1)at 25 A g^(−1))due to significantly improved kinetics inducted by intramolecular HB.This work provides an efficient approach toward insoluble organic electrode materials.

A DFT Study on Intramolecular Hydrogen Bond in Substituted Catechols and Their Radicals

Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.

Study on the Intramolecular Hydrogen Bonds of Dibenzofurans, Xanthones and Anthraquinones with One or Two Positions Substituted by Hydroxyls

The thermodynamic properties of dibenzofurans （DFs）, xanthones （XTs） and an-thraquinones （AQs） with one and two positions substituted with hydroxyls in the ideal gas state at 298.15 K and 1.013×10^5 pa were calculated at the B3LYP/6-311G^＊ level using Gaussian 03 program. The isodesmic reactions were designed to calculate the standard free energy of formation （△fG^θ）. Three types of hydrogen bonds exist in the three kinds of chemicals and their bond energies were ascertained as 7-15, 15-23 and 49-58 kJ·mo1^-1 respectively by comparing the △fG^θ values. Electronic density topology analysis was applied to validate the strength of bond.

A^1HNMR STUDY ON THE FORMATION AND BREAKING OF INTRAMOLECULAR HYDROGEN BONDS OF BILIRUBIN IN CDCl_3-DMSO-d_6 BINARY SOLVENT

The formation and breaking of intramolecular hydrogen bonds of bilirubin in CDCl_3-DMSO-d_6 binary solvent have been investigated by means of NMR spectroscopy.The chemical shifts of protons at dipyrrinone lactam C=O and N-H,Pyrrole N-H,C-5,C-15 and methylene groups of 8,12-propionic acid side-chains changed markedly as a function of composition of the binary solvent.The hydrogen bond formation is dependent on the conformation of propionic acid side-chains.

Estimation of Intramolecular Hydrogen-bonding Energy via the Substitution Method

The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96. Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds. Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.

Effective exciplex system with high emission efficiency via intramolecular hydrogen bonding for efficient solution processable OLEDs

Exciplex system is a charming candidate for thermally activated delayed fluorescence(TADF)due to its intrinsic small energy difference between the lowest singlet state and triplet excited state(ΔEST).However,high emission efficiency and fast radiative decay rate are still a formidable task for the exciplex emission.Herein two novel tri(triazolo)triazine-based TADF emitters,named TTT-HPh-Ac and TTTMePh-Ac,are synthesized and characterized.Using such TADF emitters as the donor molecule and(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-dial)tris(diphenylphosphine oxide)(PO-T2T)as the acceptor molecule,the exciplex system of TTT-HPh-Ac:PO-T2T and TTT-MePh-Ac:PO-T2T are prepared,which show a tinyΔEST of 40±20 meV and fast reverse intersystem crossing rate.As a result,very high emission efficiency(97%)and a small non-radiative decay rate are detected for the exciplex TADF system.The solution processable organic light-emitting diode using the exciplex system as the emitter achieves a maximum external quantum efficiency(EQE_(max))of 17.0%.When using the exciplex as the host matrix,the TTT-MePh-Ac:PO-T2T based solution processable device shows a better performance with an EQE_(max)of 20%with a very small efficiency roll-off of 6%at 1000 cd m^(−2).This work proves that the molecule with both intramolecular hydrogen bonding and proper twisted molecular geometry in exciplex is more favorable to enhance its emission efficiency and suppress the non-radiative transition,which provides a new way to develop efficient and stable exciplex emitters.

Density Functional Theoretical Studies on Effect of Intramolecular Hydrogen Bonds on Reduction of Nitrophenols

Intramolecular hydrogen bonds（IMHBs） can lead to different physicochemical characteristics of nitro- phenols（NPs） that determine their environmental behavior. In the present work, to reveal the relationship between IMHB and nitrophenol reduction, the effects of IMHB on the molecular geometries and properties of a series of ni- trophenols were investigated with density functional theory（DFT） calculations. The results of the geometry optimiza- tion and atoms-in-molecules（AIM） analysis indicate relatively strong IMHBs in ortho-substituted nitrophenols, whose stability could be significantly improved. In comparing the ELUMO and adiabatic electron affinities（AEA） of the nitrophenol isomers, the presence of IMHBs benefited the reductive degradation of NPs, consistent with a previous study. To gain an insight into the effect mechanism of IMHBs on the reductive degradation behavior of these mole- cules, the condensed electrophilicity Fukui index（f-）, natural charges and Wiberg bond orders of these nitrophenol isomers were calculated. The calculations indicate that the electrophilic reactivity activity of the O atom on the nitro group could be significantly improved due to the formation of IMHBs, which results in the enhanced reductive degradation of ortho-substituted NPs.

Synthesis and Theoretical Study of Intramolecular Hydrogen Bond at Two Possible Positions in Pyrazolo[1,2-b]phthalazine

Properties of dimethyl 3-（alkylamino）-5,10-dioxo-5,10-dihydro-1H-pyraolo[1,20b]phthalazine-1,2-dicarboxy-late and its derivatives were studied by means of ab initio method. NO2 derivative of title compound was synthe- sized and the nature of its intramolecular hydrogen bond （HB） was investigated. Furthermore, the topological prop- erties of the electron density distributions for N--H＇＂O intramolecular bridges were analyzed in terms of the Bader theory of atoms in molecules （AIM）. The electron density （p） and Laplacian （V2p） properties, estimated by AIM calculations, indicated that O＇--H bond possesses low P and positive VZp values which are in agreement with elec- trostatic character of the HBs, whereas N--H bonds have covalent character （V2p〈0）. Moreover, steric effect of the t-Bu group on structure and topological parameters of pyrazolo[1,2-b]phthalazine conformers was studied. Fi- nally, the powerful method of Espinosa was used to obtain the H-bond energy.

ESIPT-regulated Mechanoresponsive Luminescence Process by Introducing Intramolecular Hydrogen Bond in Naphthalimide Derivatives

Herein,two compounds,4-2′-hydroxybenzylidenehydrazinyl-N-butyl-1,8-naphthalimide(BN-1)and 4-benzylidenehydrazinyl-N-butyl-1,8-naphthalimide(BN-2),were synthesized to explore the hydrogen bonding effect on mechanoresponsive luminescent(MRL).The results showed that compound BN-1 exhibited strong emission in solution and solid-state compared with compound BN-2.After grinding,the emission intensity of compound BN-1 sharply decreased by as much as 15 times with an obvious red-shift from 552 nm to 577 nm.The control compound BN-2,by contrast,did not change so much before and after grinding.Single crystal analysis suggests that BN-1 molecule formed strong intramolecular interaction via-N=N⋯H-O hydrogen bond with a distance of 0.2632 nm.An excited-state intramolecular proton transfer(ESIPT)based fluorophore featured this intramolecular hydrogen bond.The intramolecular hydrogen bond as well as other intermolecular interactions can rigidify the molecular conformation of compound BN-1 in solid-state,and thus suppress the nonradiative pathways,resulting in strong emission.These intra-and intermolecular interactions were destroyed by mechanical stimuli,accompanied by molecular conformation change that decreases the luminescence and blocks the ESIPT process.The MRL process was also demonstrated by scanning electron microscopy and powder X-ray diffraction.The molecular stacking mode changed from crystalline to a disordered amorphous state after grinding.

Stability and Intramolecular Hydrogen Bond of the Free Radicals of Gallic Acid and Its Esters

Gallic acid and its alkyl and phenyl gallate usually exist in gall and tea. They have very good properties in antioxygenation, antisepsis, astringency, etc., there-fore they are generally used in the industries of grease, dyestuff, spinning and weaving, metallurgy, chemistry, petroleum, food, medicine, etc. It has been known

Intramolecular Resonance-assisted Hydrogen Bonds in N-Salicylidene-anilines

In the crystal structures of N-salicylidene-anilines, the ortho-OH group with the central N atom forms a planar six-membered ring through intramolecular hydrogen bonds (Fig. 1). The pseudo-aromatic ring is coplanar with its attached phenyl ring. The resonance strengthens the H-bond through proton transfer between the O and N atoms (Fig. 1, I II): dCO and dCC become shorter and dCN longer significantly. The d1～d6 are also changed regularly. According to the geometries obtained from X-ray analysis and retrieved from the Cambridge Structural Database (CSD, version 5.21)[1], we believe that the main resonance, at least in solid state, is the molecular keto form (II, Fig. 1) instead of the zwitterionic one (III, Fig. 1).

Tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester

Interesting and diverse tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester are described and rationally interpreted.

Structure and Vibrational Spectroscopy of 2-Methylallyl Alcohol

The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.

线性氨基醇分子内氢键相互作用的溶剂效应

采用受激拉曼光谱技术测量4种线性氨基醇NH_(2)(CH_(2))_nOH(n=2,3,4,5)的气相拉曼光谱,同时采用自发拉曼光谱技术测量其液相拉曼光谱.结果表明:气相状态下,除n=5外,n=2,3,4的线性氨基醇分子中观察到显著的O—H…N分子内氢键相互作用;在纯液相和水溶液(摩尔分数为0.5)状态下,由于分子间氢键相互作用的竞争,4种线性氨基醇的分子内氢键相互作用均消失;在非极性CCl4溶液(摩尔分数为0.001)中,除n=2中可观察到微弱的分子内氢键外,其余线性氨基醇中均未观察到分子内氢键相互作用.因此,不管极性还是非极性溶剂均显著影响线性氨基醇的分子内氢键相互作用.

The substituent effect on the excited state intramolecular proton transfer of 3-hydroxychromone

The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on proton transfer.The mechanism of hydrogen bond enhancement is qualitatively elucidated by comparing the infrared spectra, the reduced density gradient, and the frontier molecular orbitals.The calculated electronic spectra are consistent with the experimental results.To quantify the proton transfer, the potential energy curves(PECs) of the four derivatives in S0 and S1 states are scanned.It is concluded that the ability of proton transfer follows the order: FM > BFM > BFBC > CCM.

Effects of π-conjugation-substitution on ESIPT process for oxazoline-substituted hydroxyfluorenes

Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory(DFT) and time-dependent DFT(TDDFT)are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals(FMOs) isosurfaces, and O–H stretching vibration frequency analysis demonstrate that PT processes are more active in S1state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole(NO–OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes(Oxa–OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.

Installing hydrogen bonds as a general strategy to control viscosity sensitivity of molecular rotor fluorophores Special Collection:Aggregation-Induced Processes and Functions

Molecular rotor-based fluorophores(RBFs)activate fluorescence upon increase of micro-viscosity,thus bearing a broad application promise in many fields.However,it remains a challenge to control how fluorescence of RBFs responds to viscosity changes.Herein,we demonstrate that the formation and regulation of intramolecular hydrogen bonds in the excited state of RBFs could modulate their rotational barrier,leading to a rational control of how their fluorescence can be activated by micro-viscosity.Based on this strategy,a series of RBFs were developed based on 4-hydroxybenzylidene-imidazolinone(HBI)that span a wide range of viscosity sensitivity.Combined with the AggTag method that we previously reported,the varying viscosity sensitivity and emission spectra of these probes enabled a dualcolor imaging strategy that detects both protein oligomers and aggregates during the multistep aggregation process of proteins in live cells.In summary,our work indicates that installing intracellular excited state hydrogen bonds to RBFs allows for a rational control of rotational barrier,thus allow for a fine tune of their viscosity sensitivity.Beyond RBFs,we envision similar strategies can be applied to control the fluorogenic behavior of a large group of fluorophores whose emission is dependent on excited state rotational motion,including aggregation-induced emission fluorophores.

芴羟甲基化合成9-芴甲醇过程中脱水产物生成的影响因素及机理

以多聚甲醛为羟甲基化试剂,在碱催化下芴一步生成9-芴甲醇过程极易发生单分子共轭碱消除,脱水生成富烯化合物,导致9-芴甲醇的选择性下降.为实现对该过程的调控,本文考察了温度、碱的种类、乙醇和多聚甲醛的添加等对9-芴甲醇脱水反应的影响,并结合动力学计算和同位素示踪,推测了芴羟甲基化合成9-芴甲醇过程中副产物生成的机理.结果表明,升高温度、增加碱性和添加甲醛有利于脱水反应发生.乙醇通过氢键作用促进脱水反应,添加量大时会导致芴负离子和9-芴甲醇负离子发生质子化作用.中间体可能会发生分子内氢传递或者夺取芴和9-芴甲醇的9位氢,促进脱水反应发生.

对苯并噻唑衍生物激发态分子内质子转移的理论研究

首先,通过研究苯并噻唑衍生物N-(3-(苯并[d]噻唑)-2-基)-4-(羟基苯基)苯甲酰胺荧光团(HBTBC)激发态分子在乙腈溶剂中氢键的几何参数变化发现,氢键在第一激发态(S1)时增强。其次,在光诱导激发下,通过乙腈溶剂中HBTBC主分子轨道的能隙以及质子受体和供体周围的电荷转移发现,电荷转移促进了HBTBC的质子转移反应。最后,通过分析势能曲线变化及过渡态数据明确了乙腈溶剂能够促进HBTBC化合物的激发态分子内质子转移(ESIPT)。

苯并双咪唑基多孔有机聚合物的制备及性能

利用三醛基间苯三酚和1,2,4,5-四胺四盐酸盐构筑了多羟基苯并双咪唑连接的多孔有机聚合物(POP-TT-TT)。通过傅立叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)以及恒流充放电等对聚合物的结构、形貌和电化学性能进行了表征和测试,进一步对结构影响电化学性能的机理进行了分析。电化学性能测试结果表明,该多孔有机聚合物显示优异的电化学性能,在电流密度为1 A/g时,比电容达到235 F/g。该性能可能归因于形成的多羟基苯并双咪唑结构,易于形成分子内氢键,引起电荷转移,进而提高电化学性能。同时,苯并双咪唑的氧化还原性提高了电化学反应动力学,引起赝电容效应,也有助于电化学性能的提高。