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A novel imide compound (DH-MC) and polyimides (DH-PIs) that form multiple intramolecular hydrogen bonds (H-bonds) were synthesised from 2,2′-dihydroxybenzophenone-3,3′,4,4′-tetracarboxylic dianhydride (DHBA) to investigate the effects of distinct H-bond structures on the photoluminescence properties of these compounds. The DHBA moiety, which contains two proton donors and three proton acceptors, can form three types of H-bond structures (MC-0, MC-1, and MC-2). DFT calculations have predicted that the most energetically stable conformation is MC-1, forming an asymmetric H-bond structure, which is consistent with the FT-IR spectroscopy and single-crystal XRD analysis results. A colourless toluene solution of DH-MC exhibited orange fluorescence with a large Stokes shift (ν = 11 905 cm−1), and DH-MC and the DH-PIs exhibited yellow fluorescence with a large ν of >10 000 cm−1 in the solid state, with both originating from excited-state intramolecular proton transfer (ESIPT). In addition, these compounds exhibit small-Stokes-shifted fluorescence from the anionic form of the DHBA moiety, resulting in yellow coloration of the DH-PI film and the DH-MC powder. To reduce coloration, a polyimide copolymer (CoPI) film was prepared using DHBA and 4,4′-oxydiphthalic anhydride (ODPA) in which the molar ratio of DHBA was set at 3%. Owing to the dilution effect and efficient energy transfer from the blue-fluorescent ODPA to the DHBA moiety in the excited state, the colourless and transparent CoPI film exhibited prominent yellow fluorescence with a quantum yield of 0.14. The wavelength-converting spectrum demonstrated that the CoPI film absorbs a wide range of UV radiation from a xenon light source and significantly enhances the yellowish light component via ESIPT emission. The CoPI film is a promising candidate for solar spectral conversion applications.

The recently developed reversibly interlocked polymer networks are made from two-pre-formed crosslinked polymers containing reversible covalent bonds via topological rearrangement. Unlike interpenetrating polymer networks, the resultant is rather homogeneous regardless of the miscibility between the parent single networks, and can be repeatedly self-healed and unlocked/re-locked. The present work focuses on revealing the critical role of the hydrogen bonds between the single networks in construction of the interlocked networks, cooperating with dissociation and re-association of the built-in reversible covalent bonds. Based on the systematic investigations of the small molecules, single networks and interlocked networks, the inter-component hydrogen bonds of the interlocked networks are found to be able to be built-up, which are more stable than the intra-molecular hydrogen bonds of the single networks. They help to pull the chains from different single networks together, preventing the occurrence of phase separation during interlocking and implementing the valuable forced miscibility. Besides, the abundant but weak inter-component hydrogen bonds are preferred. The outcomes not only show the hitherto unknown part of the mechanism involved in the formation of the interlocked networks, but also benefit the design of new members of interlocked networks.

The synthesis of a series of trans-heteroleptic paddlewheel diruthenium(II, II) complexes with various hydroxy-substituted benzoate ligands, [Ru2((OH)xPhCO2)2(2,6-(CF3)2PhCO2)2(THF)2] ([Ru2II,II]) as tetrahydrofuran (THF) adducts is reported, where (OH)xPhCO2− stands for o-hydroxybenzoate (o-OH), m-hydroxybenzoate (m-OH), p-hydroxybenzoate (p-OH), 2,3-dihydroxybenzoate (2,3-(OH)2), 2,4-dihydroxybenzoate (2,4-(OH)2), 2,5-dihydroxybenzoate (2,5-(OH)2), 2,6-dihydroxybenzoate (2,6-(OH)2), or 3,4-dihydroxybenzoate (3,4-(OH)2), and 2,6-(CF3)2PhCO2− represents 2,6-bis(trifluoromethyl)benzoate. In this heteroleptic series, the redox potential (E1/2) of the [Ru2II,II]/[Ru2II,III]+ couple in THF varies over a wide range, from −18 mV (vs. Ag/Ag+) for p-OH to 432 mV for 2,6-(OH)2. The redox properties are linearly dependent on the acidity (pKa) of the OH-substituted benzoic acids, but do not depend on the number of ortho-substituted hydroxy (o-OH) groups. This indicates that the steric effect of o-substituents is irrelevant in the case of hydroxyl groups, owing to the formation of intramolecular hydrogen bonds between the o-OH group and carboxylate oxygens. The value of the Hammett constant o for the o-OH substituent was determined to be 0.667, indicating a strongly electron-withdrawing character, contrary to the expectation of electron-donating character for an OH group. The redox properties of the compounds were well explained in a framework of Hammett analyses and were also consistent with their HOMO energy levels evaluated by DFT calculations based on the atomic coordinates. The unexpected electron-withdrawing character of the o-OH groups could be attributed to the direct effect of intramolecular hydrogen bonding on the charge density on the carboxylate oxygen.

Exploiting novel TADF emitters for highly efficient orange-red non-doped organic light-emitting devices (OLEDs) is a research hotspot. Nevertheless, serious non-radiative transitions of the electrogenerated excitons significantly hinder the pace of the development. Herein, two novel donor–π–acceptor (D–π–A) type TADF emitters 10-(4-(2,6-di(pyridin-3-yl)pyrimidin-4-yl)phenyl)-10H-phenoxazine (PyPmP) and 10-(4-(2-(pyridin-3-yl)-[4,5′-bipyrimidin]-6-yl)phenyl)-10H-phenoxazine (PmPmP) were designed and synthesized. In their crystals, suitable intermolecular hydrogen bonding interactions are observed that enable head-against-tail 3D supramolecular frameworks. Such frameworks not only prefer a high horizontal molecular orientation but also strictly restrict the non-radiative process in non-doped conditions. Their non-doped OLEDs realize decent orange-red electroluminescence with maximum current efficiencies (CE), power efficiencies (PE), and external quantum efficiencies (EQE) of 50.5 cd A−1, 53.5 lm W−1, and 18.8% for PyPmP, 23.2 cd A−1, 22.1 lm W−1, and 11.3% for PmPmP, respectively. Moreover, both devices can still retain high efficiencies as luminance increases, and exhibit a neglectable efficiency roll-off at 1000 cd m−2. These results are among the best of ever reported orange-red non-doped OLEDs. These results demonstrate that intermolecular hydrogen bonding interactions can play important roles in exploiting TADF emitters for high-performance orange-red non-doped OLEDs.

The aim of the current research article is to present the supramolecular features in the crystal structure of seven novel coumarin derivatives, their structural modification due to the addition of various functional groups and the results of spectroscopic investigations as well as theoretical calculations. The compounds were characterized by NMR, FTIR, UV-vis, mass spectroscopy, and single crystal X-ray diffraction studies. The structural analysis revealed that the coumarin moiety exhibits planarity in all the compounds with average dihedral angles of 1.71(2)° between the pyran and fused benzene rings and 9.40(9)° between the benzopyran and terminal benzene rings. Various supramolecular architectures formed due to the intermolecular interactions significantly contribute to the crystal packing of the molecules. The intermolecular interactions and their contributions were quantified using 2D fingerprint plots. The structural aspects of the compounds were examined based on their optimized geometry, intramolecular hydrogen bonding and chemical reactivity using density functional theory. Theoretical FTIR calculations were performed using VEDA4 software and the TD-DFT method was used to study the electronic transitions of the compounds. The theoretical FTIR and UV data were compared with the experimental data. Natural bond orbital (NBO) analysis revealed the presence and the importance of non-covalent and hyperconjugative interactions for the stability of the molecules in their solid state. The charge distribution and nucleophilic and electrophilic regions of the molecules were identified by molecular electrostatic potential (MEP) mapping. A quantum theory of atoms in molecules (QTAIM) study was carried out to investigate the nature and strength of the hydrogen bonding interactions.

The presence of water in organic systems usually inhibits the activity of the reaction. In the biphasic system composed of water-decane, the distribution of lignin-derived m-cresol hydrodeoxygenation (HDO) products catalyzed by Ni-Sn was affected with the presence of water. Water can facilitate the hydrogenation process by the dissociating water to produce H protons. However, the formation of complete deoxidation products may be inhibited because of the catalyst surface reconstruction and the low solubility in aqueous system. The DFT calculation theoretically revealed that the existence of water can lower the barrier and stabilize the transition state, but also affect the rupture of the CAr-O bond. Also, the significant characteristics of solvent action were explained by the hydrogenation and the solvatochromic parameters. Among them, m-cresol has a good performance in hydrocarbon solvents (CnH2n) and hydrogen bond donor (HBD) solvents. However, the catalytic activity decreases in alcohols due to the synergistic effects like H-bond and competitive adsorption between solvent and the substrate. The mechanism of the solvent effects with different properties can provide reference for the subsequent expansion of the system in a wide range. Therefore, the synergy between solvent and the catalyst provides a promising method for upgrading reclaimed chemicals from lignin.

We present a first-principle molecular dynamics study on the uptake and hydration of sulfur dioxide on the dry and wet fully hydroxylated surfaces of (0001) alpha-quartz, which are a proxy for suspended silica dust in atmosphere. The average adsorption energy for SO2 is ~10 kcal/mol on both dry and wet surfaces. The adsorption is driven by hydrogen bonds formation between SO2 and the interfacial hydroxyl groups (on dry silica), or with water molecules (in the wet case). In the dry system, we report an additional electrostatic interaction between the interfacial hydroxyl oxygen and the sulfur atom, which further stabilize the adsorbate. On dry silica, the interfacial hydroxyl group coordinates SO2 yielding to a surface bounded bisulfite (Si-SO3H) complex. On the wet surface, SO2 reacts with water forming bisulfite (HSO3-), and the latter remains solvated inside the adsorbed water layer. The hydration barrier for sulfur oxide is 1 kcal/mol and 3 kcal/mol on the dry and wet silica, respectively, while for the backward reaction (i.e., bisulfite to SO2) the barrier is 6 kcal/mol on both surfaces. The modest backward barrier rationalizes earlier experimental findings showing no SO2 uptake on silicates. These results underline the importance of the surface hydroxylation and/or of adsorbed water layers for the SO2 uptake and its hydration on silica. Moreover, the hydration to bisulfite may prevent direct SO2 photochemistry and be an additional source of sulfate: this is especially relevant in atmosphere subject to high level of suspend mineral dust, intense solar radiation and atmospheric oxidizers.

Global warming is becoming a challenging issue due to the emission of a large number of greenhouse gases, mainly CO2. The transformation of CO2 into chemicals with high additional value is considered a promising and sustainable way to solve the “greenhouse effect”. Herein, a series of polyamine-functionalized imidazolyl poly(ionic liquid)s (PILs) modified by triethylenetetramine (TETA) were synthesized as heterogeneous catalysts to convert CO2 into cyclic carbonates. The synergistic effect of nucleophile (bromide anions) and polyamine groups in promoting CO2 conversion was explored by density functional theory (DFT) calculations, which is critical to improve the catalytic performance. When the anions of ionic liquids acted as nucleophiles to attack the epoxide from the C–O bond with less steric hindrance, the substrate epoxide and CO2 can be activated by hydrogen bonding with amine group protons. Therefore, PILs modified by TETA (N4-PIL-x) have been verified to possess high efficiency and stable reusability for the cycloaddition of epoxides with CO2 without solvent, metal, and co-catalyst, of which N4-PIL-2 can achieve 98.0% conversion of epichlorohydrin (ECH) with a turnover frequency (TOF) value as high as 42.4 h−1 under ambient pressure; moreover, the complete conversion of epichlorohydrin is obtained in only 4 h at 1.0 MPa CO2 pressure.

The present work investigates the effects of cis and trans butenedioic acid isomers (maleic acid and fumaric acid) on the crystallinity and pharmaceutical behavior of lumefantrine. Differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), attenuated total reflectance infrared spectroscopy (ATR-IR), solid-state nuclear magnetic resonance spectroscopy (ss-NMR), and single-crystal X-ray diffraction (SC-XRD) studies were employed. Lumefantrine–fumaric acid crystallized as a salt in the monoclinic space group P21/c. In comparison, DSC and PXRD showed the formation of a co-amorphous solid with maleic acid. Complete proton transfer with a strong ionic interaction led to crystalline salt formation with the trans isomer, whereas weaker/fewer hydrogen bonds with the cis isomer of butenedioic acid led to a co-amorphous salt. The in vitro dissolution of both salts resulted in a similar 2.6–2.7-fold improvement in dissolution rate when compared to that of the crystalline lumefantrine. The crystalline and co-amorphous salts were stable under accelerated stability conditions (40 ± 2 °C and 75 ± 5% RH) for one month.

Sheet-liked organic semiconductor crystals with two-dimensional (2D) packed structures play an essential role in practical applications of high-property optoelectronic devices. Here, we report a practical example in combination with chemical structures and crystallization engineering to construct a balanced 2D network for organic thin sheet-shaped crystals. The introduction of the cyano group enabled the formation of hydrogen bonds, promoting the in-plane 2D network construction both in strength and direction with π⋯π (or C–H⋯π) interactions. Through changing the chamber pressure and growth temperature, we realized a macroscopic morphology adjustment from rods to sheets with the same single crystal structure, ascribed to the relative strength changes of different facet energies. Such a macroscopic dimension control combined with supramolecular chemistry and crystal engineering offers a new perspective for boosting further developments for 2D stacked organic semiconductor crystals.

Over the recent decades, tremendous interest has been developed involving the transformation of complex substrates by the C–H activation and functionalization. In particular, the palladium-catalyzed directing and non-directing group-assisted C-H functionalization has been emerged as a powerful avenue to access C-branched glycosides. Due to the extreme complexity, delicate functionalities, and high stability of C-H bonds, site-selective functionalization of carbohydrate under mild conditions are highly desirable. The purpose of this review is to cover most of the recent advances on palladium-catalyzed C(sp3) and C(sp2)-H bond functionalizations for the synthesis of C-branched glycosides along with future directions.

In this work we report on new heteroleptic coordination compounds [Pb2(LI)2](NO3)2∙2MeOH (1), [Pb2(LII)2](NO3)2 (2), [Pb2(LIII)2](NO3)2∙MeOH∙H2O (3) and [Pb2(LIII)2(H2O)](NCS)2 (4), which were obtained through self-assembling of 2-(amino(pyridin-2-yl)methylene)hydrazine-1-carbothioamide (HLI), 2-(amino(pyrazin-2-yl)methylene)hydrazine-1-carbothioamide (HLII) or 2-(amino(pyridin-2-yl)methylene)-N-methylhydrazine-1-carbothioamide (HLIII) with Pb(NO3)2 or a mixture of Pb(ClO4)2 and KNCS, respectively. In all the obtained complexes the lead(II) cation is N,N',S-chelated by the tridentate pincer type monodeprotonated ligand LI–III. In addition to the thiosemicarbazone chelation, the sulfur atom in each structure acts as bridging to connect two [Pb(LI–III)]+ units to form a dinuclear dimeric species having a centrosymmetric geometry, so that the ligands are directed either at different, in 1 and 2, or the same, in 3 and 4, side of the coplanar Pb2S2 core. In the latter structures two metal centers are additionally linked with each other through the oxygen atom of the bridging water molecule. The dimeric units in 1–4 are further linked through the Pb–N tetrel bonds, yielding 1D supramolecular polymeric chains, which, in turn, are interlinked though a myriad of other intermolecular noncovalent inetaractions, including tetrel bonds, hydrogen bonds and π-stacking. Counterions (NO3– and NCS–) as well as co-crystallized solvent molecules (MeOH and H2O) are also responsible in further stabilization of the overall crystal packing of the obtained complexes as a source of either tetrel and/or hydrogen bonds. The observation of the recurrent tetrel bonds in compounds 1–4 has been rationalized using DFT calculations and molecular electrostatic potential (MEP) surface plots. Moreover, coordination bonds (covalent character) and tetrel bonds (noncovalent character) between the complexes and their conterions (and water moelcule) have been differentiated using the quantum theory of «atoms-in-molecules» (QTAIM) and the noncovalent interaction index (NCI index) computational methods.

The acetonitrile solvate of a Schiff base molecule (HL) with acetonitrile (HL·2CH3CN) and its Cd(II) complex (Cd(HL)2Cl2, 1) were designed and synthesized. The different conformation of HL in HL·2CH3CN is adjusted by the hydrogen bonding O-H···O between HL molecules, together with N-H···N between HL molecules and acetonitrile molecules. While the conformation of HL in complex 1 is adjusted by coordination interactions between Zn ions and atoms O and N, together with hydrogen bonding N-H···Cl. The presence of the triphenylamine group makes HL·2CH3CN and complex 1 loosely packed. Upon grinding, HL·2CH3CN and complex 1 both showed high-contrast mechanochromic luminescence (MCL) change from blue to green and cyan to yellow, respectively. These changes can be eliminated by fumigation with organic vapor. The results of powder X-ray diffraction (PXRD) show that their MCL is due to the phase transformation from crystalline to amorphous state. In addition, HL·2CH3CN and complex 1 also exhibited high-contrast acidochromism upon exposure to HCl and NH3 vapor. X-ray photoelectron spectroscopy (XPS) and PXRD studies show that the protonation of the -NH- group together with a phase transformation from crystalline to amorphous state is attributed to the fluorescence switching. For HL·2CH3CN, the protonation process was accompanied by the departure of acetonitrile molecules. The emission of HL was restored to the amorphous state rather than the original crystalline state emission after further exposure to NH3 vapor, while 1-HCl could restore to the original crystalline state emission. In addition, HL·2CH3CN and complex 1 have been successfully used to produce writable and acid-responsive test papers.

The attachment of electrons is known to significantly influence some chemical and biological processes. The chemical differences between Schiff and Mannich bases are characterized by strong intramolecular hydrogen bonds, resulting from the presence of, respectively, single or double carbon–nitrogen bonds in the chelate rings. Differences are especially visible in the hydrogen transfer processes from molecular (O–H⋯N) to the proton transfer (O⋯H–N) forms. The reaction in a Schiff base occurs as an ordinary hydrogen transfer from a donor to an acceptor, while in a Mannich base the transfer of hydrogen occurs simultaneously with a C–N bond scission leading to an intermolecular complex. The attachment of electrons preserves the overall structural topology of the reactants; however, due to differences in electron affinities, reactions switch from endothermic to exothermic and reaction rates in the anionic systems are significantly higher. The difference in electron affinities for particular reactants comes from the fundamental differences in electron binding mechanisms, leading to the valence-bound or dipole-bound states. The observed mechanisms are closely related to the nature and size of the LUMOs of the parent molecules. The transition state of the Mannich base corresponds to the σ and π orbital conversion and possesses the characteristics of the valence-bound state and the dipole-bound electronic state.

Coordination polymers have received immense attention for proton conduction owing to their highly tunable and designable structures. Herein, based on the flexible ligand 5-(4-pyridine)-methoxyisophthalic acid (H2L), two novel highly chemically stable indium coordination polymers (In-CPs), InL(H2O)Cl·H2O (In–L–Cl) and InL(H2O)(NO3) (In–L–NO3), were synthesized through solvothermal methods. In–L–Cl and In–L–NO3 are isostructural, in which every individual In(III) atom connects to L2− to form a single layer, and coordinated Cl− and NO3− are inserted into the windows of the interlayers. Both of them possess high water and chemical stability. More importantly, the abundant Cl− and NO3− exposed in the interlayer can act as hydrogen bond acceptors to facilitate the formation of a dense hydrogen bonding network, thus improving proton transfer efficiently. Electrochemical impedance spectroscopy shows that In–L–Cl and In–L–NO3 display optimized proton conductivities of 1.88 × 10−3 and 1.00 × 10−3 S cm−1 at 100% relative humidity (RH) and 80 °C, respectively. The difference in proton conductivity of In–L–Cl and In–L–NO3 likely stems from the variations in the hydrogen bonding networks formed by lattice water and the different electronegativities of the coordinated anionic functional sites. This study provides an alternative way to prepare highly proton-conductive CPs.

The safety of animal-origin foods has a major influence on human health. Although the use of veterinary drug additives (VDAs) significantly promotes the normal growth and development of animals against diseases, the excessive consumption of VDAs is always the most worrying part. Thus, realizing a direct and prompt detection of solid VDAs is highly desirable. In this study, we incorporated a functional unit of triazolo [4,5-c] pyridine (TP) in polymer semiconductors. The theoretical simulation demonstrates that TP can effectively form hydrogen bonding with the VDA molecules. Furthermore, highly sensitive polymeric field-effect transistors (PFETs) are fabricated through the configurational design of low-dimensional polymer networks (LDPNs). The conducting channel and hydrogen bonding sites of the LDPN-based PFETs could be directly exposed to the analytes, thereby effectively capturing VDA molecules and converting the stimuli into electrical signals. The obtained PFET-based solid sensors showed highly sensitive and stable detection of melamine powders at a low operation voltage of −5 V. The detection limit realized is lower than the international standards in animal feeds (2.5 ppm). These results demonstrate the promising applications of PFETs for high-efficiency and low-power-consumption sensors for solid detection or biological diagnosis.

(E)-4-(3,5-Bis(benzo[d]oxazol-2-yl)-2,6-dihydroxystyryl)-1-ethylpyridin-1-ium iodide (3) with extended conjugation was synthesized by coupling a styryl substituent into the bis(HBO) 1 structure. Probe 3 exhibited bright red emission (λem ≈ 600 nm) with a large Stokes shift (Δλ ≈ 210 nm), attributing to strong ICT enhanced by ESIPT. The role of the styryl substituent was further evaluated with the aid of low temperature fluorescence. Probe 3 exhibited excellent selectivity towards fluoride anions in solution by generating a near infrared emission peak at λem ≈ 720 nm. Probe 3 was found to be a useful tool for quantifying fluoride content in solution by both absorbance and emission measurements. The fluoride binding of 3 was assumed to occur via strong intermolecular hydrogen bonding with the F− anion (K = 3413). The association stoichiometry for the 3-F complex was found to be (1 : 1) according to the Benesi-Hildebrand method.

Using the method of molecular Voronoi–Dirichlet polyhedra all types of atomic interactions in ten known polymorphs of the drug galunisertib (GAL) – one of the most prolific polymorphic systems – were analyzed quantitatively in detail. It was shown that every polymorph of GAL is characterized with a unique set of intra- and intermolecular noncovalent interactions. A new type of diagram – the (RF, d) distribution – was introduced for highlighting the differences in noncovalent interactions of polymorphic modifications and for visual support of the previously introduced k–Φ criterion. Hydrogen bonding motifs in GAL polymorphs in comparison with nine polymorphs of pharmaceutical aripiprazole (another prolific polymorphic system) are discussed.

A family of isostructural heterometallic MOFs based on Fe2M clusters (MOF-Fe2M; M = Fe, Co and Ni, respectively) have been synthesized and serve as potential proton conductors and photocatalysts for CO2 photoreduction, exhibiting varied proton conductivities and photocatalytic performances. Among them, MOF-Fe3 exhibits the best proton conductive performance with a value of 3.39 × 10−2 S cm−1 at 70 °C and 98% RH. Furthermore, three proton conductive membranes based on MOF-Fe3 have been prepared, and the optimum membrane shows a high proton conductivity with σ = 5.46 × 10−3 S cm−1 at 60 °C and 98% RH. Additionally, all frameworks are employed as photocatalysts for converting CO2 into CO in the solid–gas mode without sacrificial agents and photosensitizers, where MOF-Fe2Ni exhibits the highest photocatalytic activity with a CO formation rate of 15.81 μmol g−1 h−1. It should be mentioned that MOF-Fe2M represent rare MOF based photocatalysts used for reducing CO2 in the solid–gas mode. Their great performances may be attributed to the following reasons: (i) appropriate structural features promote the formation of hydrogen bond networks and the adsorption of CO2; (ii) extensive Fe2M units can adsorb visible light and provide reaction active sites for CO2 photoreduction.

We report here the design, synthesis, and antiproliferative activity of three coordination complexes [Mn2(pydco)2(bpy)2(H2O)2]·2H2O (1), [Zn(bpy)(Hpydco)2] (2), and [Zn(bpy)Cl(Hpydco)]·2H2O (3) (H2pydco = pyridine-2,5-dicarboxylic acid N-oxide, bpy = 2,2′-bipyridine). Molecular structures of these complexes have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. According to the structural analysis, 1–3 are discrete complexes containing N- and O-donor ligands (bpy and pydco2−) in which pydco2− can be coordinated to the metal centres via the N-oxide oxygen and one carboxylate oxygen to generate a six-membered chelate ring. Also, these structures benefit from extensive intermolecular interactions such as hydrogen bonds and π-interactions which are the major forces to make them more stable in the solid state. The energetic features of the π-stacking interactions observed in compounds 1–3 have been computed and compared to the H-bonds. The interactions in the solid state have been also studied using the independent gradient model approach (IGM plot). The IGM-δg approach uses a new descriptor (δg) that locally represents the difference between a virtual upper limit of the electron density gradient and the true electron density gradient. This newly developed IGM methodology automatically extracts the signature of interactions between two given fragments. Finally, the antiproliferative properties of these complexes were tested on several cancer cell lines by MTT assay and flow cytometry. Also, to compare the antiproliferative activities of these complexes with common chemotherapy drugs, the antiproliferative property of cisplatin was evaluated as a reference and positive control.

Nanocapsule-based technologies constitute a unique and novel research field for the food and pharmaceutical industry. The potential benefits of applying these technologies include, for example, higher bioavailability, high shelf stability, and controlled release of active ingredients. Protecting hydrophilic ingredients in food or pharmaceutical applications is crucial but challenging because of their strong tendency to leak out of the capsules into the external aqueous phase. In this study, we developed nanocapsules synthesized by electrostatic interactions between chondroitin sulfate (CS) and egg white protein (EWP). The interactions were induced by acidic conditions and continuous ultrasonication because of the contribution of the hydrogen and amide bond formation. We optimized the preparation conditions at a CS : EWP ratio of 6 : 4, in which the CS–EWP nanocapsules had an average particle size of 133.2 ± 3.4 nm with a PDI of 0.2 and a zeta potential of −25.5 mV. Molecular docking analysis revealed that the linear helix chain of CS functioned as a skeleton structure by bonding with the random coil of EWP, confirming the formation of intermolecular hydrogen bonds between CS and EWP. Scanning electron microscopy and transmission electron microscopy images revealed that the microcapsules contained irregular spheres with a core and shell structure. The encapsulation efficiency and loading content of the nanocapsules demonstrated their potential to prevent leakage of the hydrophilic ingredients because of the dense shell. Nanocapsules formed via the CS–EWP interaction provide a green and sustainable method for efficiently encapsulating various hydrophilic food or pharmaceutical ingredients.

Although little is known about the reaction mechanism between cyclopentasilane (CPS: cyclic Si5H10) and borane (BH3), the reaction product is known to be a liquid precursor for p-type semiconducting Si. Therefore, investigation of the reaction mechanism enables more functional material design and contributes to the realization of printable Si semiconductors. Here, we investigated the interaction between CPS and BH3 using density functional theory (DFT) calculations. The calculations showed the occurrence of a dehydrogenative condensation reaction with an energy barrier less than 10 kcal mol−1. CPS and BH3 act as Lewis bases and acids, respectively, and form somewhat stable reactant complexes with monobridged hydrogen bonds through electrostatic interactions between the positively charged Si atoms and negatively charged B atoms. The monobridged hydrogen bonds initiate dehydrogenation because they abstract other hydrogen atoms in the compound. Eventually, liquid-phase hydrosilanes with Si–B bonds remain as the reaction product. This reaction model and reaction products were also evaluated experimentally using nuclear magnetic resonance spectroscopy, gas chromatography, and gel permeation chromatography. Characterization of the printed Si film also showed that the reaction product can be used as an effective liquid precursor for p-type semiconducting Si.

In terms of CO2 capture and storage (CCS), it is highly desired to substitute of high efficiency process for the applied one which is far from the ideal one. Physical processes cannot capture CO2 effectively, meanwhile CO2 desorption is energy-intensive in chemical processes. Herein, a depth-suitable and water-stable trap for CO2 capture was discovered. Carboxylates can react with polybasic acid roots by forming united hydrogen bonds. Carboxylate ionic liquid (IL) aqueous solutions can absorb one equimolar CO2 chemically under ambient pressure, and its CO2 desorption is easy, similar to that in physical absorption/desorption processes. When used as aqueous solutions, carboxylate ILs can replace alkanolamines directly in the applied CCS process, and the efficiency is enhanced significantly due to the low regenerating temperature. CO2 (or polybasic acids) can be used as a polarity switch for ILs and surfactants. A new method for producing carboxylate ILs is also proposed.

Supramolecular polymers have the combined properties of both traditional polymers and supramolecules. They are generally formed via the self-assembled polymerization driven noncovalent interactions such as hydrogen bonding, π-π stacking, metal coordination, and host-guest interaction between building blocks. The driving force for the formation of supramolecular polymers has changed from single noncovalent interactions to multiple noncovalent interactions. The advantages of multiple noncovalent interactions driving the formation of supramolecular polymers are reviewed from four aspects: polymer construction, the enhancement of bonding strength, properties and topological structure. The applications are illustrated with detailed examples including self-healing, drug delivery, bioimaging, biomedicine, environmental sensing and electronics.

The current library of synthetic molecular sensors for small polar molecules is limited. In this work, we describe the synthesis of two diastereomeric mono-phosphonate calix[4]pyrrole cavitands, 1in and 1out, acting as fluorescent sensors for amino acids. The two isomeric cavitands differ in the relative orientation, in (1in) and out (1out), of their PO bridging group and the N-phenyl-naphthalamine fluorophore directly attached to it, with respect to their polar aromatic cavities. Using 1H and 31P NMR spectroscopy and non-fluorescent cavitand analogues (5in and 5out), we demonstrate the formation of 1 : 1 complexes with L-proline (L-Pro) and the relevance of the inwardly directed PO group in the binding of the amino acid. Only the L-Pro⊂5in complex establishes a charged hydrogen bonding interaction between the receptor PO group and the protonated amine of the bound zwitterionic amino acid. This interaction is responsible for an increase in the thermodynamic stability of the complex compared to the L-Pro⊂5out counterpart. We investigate the binding properties of the fluorescent cavitands, 1in and 1out, with L-Pro and L-pipecolic acid (L-Pip) at micromolar concentration using emission spectroscopy (direct binding-based sensing, BBS). The observed emission changes in the BBS experiments were small but evidenced the role of the cavitands as fluorescent sensors. In agreement with the millimolar concentration results (1H NMR experiments), the fluorescent 1in sensor displays a larger binding affinity for L-Pro than the 1out isomer. Conversely, the 1out isomer experienced larger emission changes upon amino acid binding. We developed FRET-based indicator displacement assays (IDA) owing to the small emission changes observed in the direct BBS experiments. At micromolar concentration, the competitive displacement of the quencher N-oxide 6 from the cavity of the 1 : 1 supramolecular ensemble (6⊂1in and 6⊂1out), by L-Pro, L-Pip, and L-phenylalanine (L-Phe) produced fluorescence “turn-on”. The results of the BBS and IDA experiments assigned a binding selectivity to the 1in isomer for L-Pro.

Identifying the special role of N-heterocyclic carbene (NHC) remains one of the most important challenges in the field of organocatalysis. Herein, we proposed a theoretical model for NHC-catalyzed decarboxylation reactions, and performed DFT calculations in two selected cases of NHC-mediated reactions involving possible decarboxylation processes. The calculation results indicate that NHC not only works as a Lewis base to promote cyclization, as NHC·H+ works as hydrogen bond donor to facilitate CO2 release, which is remarkably different from the proposed role of Lewis bases in previous reports. Further analysis indicates that C–H⋯O hydrogen bond interactions contribute significantly to controlling stereoselectivity in these kinds of reactions.

1,3-Dipolar cycloaddition constitutes a powerful means for the synthesis of five-membered heterocycles. Recently, the potential of this field of chemistry has been expanded by the employment of organocatalytic activation strategies. One group of substrates, namely imines derived from salicylaldehydes, is particularly useful. Additional activation via intramolecular H-bonding interactions offered by the presence of an ortho-hydroxyl phenolic group in their structure results in increased reactivity of these reactants. Furthermore, it can be utilized in subsequent reactions creating chemical and stereochemical diversity. This minireview provides a summary of the recent progress in this field of organocatalysis and indicates other important applications of hydroxyl-group-activated azomethine ylides in asymmetric organocatalysis.

In this study, we investigate the mechanism underlying the binding of SA with HSA by multiple spectroscopic and computational approaches. The topographic changes in the native HSA and HSA–SA structure and behaviours were explored by atomic force microscopy (AFM). Moreover, other advanced spectroscopic methods such as fluorescence, Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy should be used to investigate and understand the binding mechanism of the HSA–SA complex. The interaction of HSA and SA takes place via a static quenching mechanism as observed from fluorescence spectroscopy. After the interaction between SA and HSA, the complex (HSA–SA) molecular dimensions have been increased as confirmed from the AFM results. Different thermodynamic parameters, such as ΔH (−29.366 kJ mol−1) and ΔS (+108.149 J mol−1 K−1), were calculated to explore the binding nature of HSA–SA, which is mainly contributed by hydrophobic contacts and hydrogen bonds. The site marker displacement and molecular modelling studies suggested that the SA can bind on the site I of HSA. Slight conformational changes of HSA–SA were observed from the CD and IR spectra. Together, this study will provide insights for the food industry on the safety and biological action of SA in the human body.

Guanidinium (G+) and benzene-1,4-disulfonate (BDS2−) form a rigid electrostatic cation–anion crystal lattice, which undergoes an interesting dynamic structural reconstruction through guest adsorption–desorption processes with H2O, pyrrole (Pyrr), pyrazine (Pyz), thiophene (TP), pyridine (Py), 1,4-dioxane (Diox), or aniline (Ani). The host lattice of bis(guanidinium)benzene-1,4-disulfonate, (G+)2(BDS2−), which does not contain void spaces initially, changed to host–guest crystals of (G+)2(BDS2−)·(guest)x upon guest adsorption (x = 1, 2, and 3). The cation–anion electrostatic N–H+⋯−O3S– hydrogen bonds between the G+ cation and BDS2− dianion formed tightly bound two-dimensional (2D) structures. These layers are connected by perpendicular BDS2− dianions, forming the guest adsorption crystalline pores. The adsorption–desorption isotherm for Diox at 298 K indicated the formation of (G+)2(BDS2−)·(Diox)3, which was consistent with the single-crystal X-ray structural analysis. Single crystals of (G+)2(BDS2−)·(Py–H2O)2 consist of two hydrogen-bonded [(G+)2(BDS2−)]2 bilayers connected by the BDS2− dianions, forming crystalline pores that accommodate 2 Py guest molecules. The H2O molecules in (G+)2(BDS2−)·(Py–H2O)2 are lodged in the intralayer, leading to the [(G+)2(BDS2−)⋯(H2O)2⋯(G+)2(BDS2−)] hydrogen-bonded bilayer. The electrostatic cation–anion host lattice of (G+)2(BDS2−) responded to the guest adsorption–desorption cycle by a dynamic structural reconstruction. A guest adsorption of polar Ani into (G+)2(BDS2−) host changed the crystal symmetry from centric P to acentric P21 of (G+)2(BDS2−)·(Ani)3.

225Ac-based radiopharmaceuticals have the potential to become invaluable in designated cancer therapy. However, the limited understanding of the solution chemistry and bonding properties of actinium has hindered the development of existing and emerging targeted radiotherapeutics, which also poses a significant challenge in the discovery of new agents. Herein, we report the geometric and electronic structural properties of hydrated AcIII cations in the [AcIII(H2O)n]3+ (n = 4–11) complexes in aqueous solution and gas-phase using density functional theory. We found that nine water molecules coordinated to the AcIII cation is the most stable complex due to an enhanced hydration Gibbs free energy. This complex adopts a closed-shell 18-electron configuration (1S21P61D10) of a superatom state, which indicates a non-negligible covalent character and involves H2O → AcIII σ donation interaction between s-/p-/d-type atomic orbitals of the Ac atom and 2p atomic orbitals of the O atoms. Furthermore, potentially existing 10-coordinated complexes need to overcome an energy barrier (>0.10 eV) caused by hydrogen bonding to convert to 9-coordination. These results imply the importance of superatom states in actinide chemistry generally, and specifically in AcIII solution chemistry, and highlight the conversion mechanism between different coordination numbers., The stable 9-coordinated complex adopts a closed-shell 18-electron configuration of a 1S21P61D10 jellium state, while potential 10-coordinated complexes need to overcome an energy barrier (>0.10 eV) caused by hydrogen bonding to convert to 9-coordination.

The influence of the halogen substituent on crystal packing and redox properties is investigated in a series of heteroleptic complexes [Fe(qsal-X)(dipic)]MeOH (qsal-X = 4-halogen-2-[(8-quinolylimino)methyl]phenolate; dipic = 2,6-pyridinedicarboxylate; X = F 1, Cl 2, Br 3 and I 4).Compounds 1 and 2 exhibit triclinic symmetry (P1̅), whereas 3 and 4 crystallise in monoclinic P21/n. The crystal packing shows self-sorting of the ligands with - interactions between the qsal-X ligands and overlap of the dipic ligands to form a 1D chain, that is supported by C-H···O interactions. In 1 and 2, the cross-section of the 1D chain is square, while for 3 and 4, it is rectangular. In the former, the dipic ligands interact through C=O··· interactions, while - interactions are found in 3 and 4. Neighbouring chains are connected via - interactions involving the quinoline rings, but their relative position is driven by the preference of 1 and 2, for C-H···X interactions, whereas 3 and 4 form O···X halogen bonds. The nature and topology of the electron density of these interactions have been investigated using molecular electrostatic potential (MEP) mapping, quantum theory of atoms in molecules (QTAIM) and ‘non-covalent interactions’ (NCI) analysis. UV-Visible experiments show MLCT bands associated with the qsal-X ligands, confirming the structure is stable in solution. Electrochemical studies reveal slight tuning of the Fe3+/Fe2+ redox couple showing a linear relationship between E° and the Hammett parameter σp.

A series of combretastatin A-4 (CA-4) sulfamate derivatives were synthesized and their structure–activity relationship on tubulin, arylsulfatase and tumor cell antiproliferation inhibition was studied. Among them, compound 16a showed excellent potency as well as CA-4 under the same conditions against six tumor cells including HTC-116, HeLa, HepG2, MGC803, MKN45 and MCF-7 cells, respectively. Molecular docking revealed that several important hydrogen bond interactions were formed between the sulfamate group of 16a and the colchicine binding site of tubulin and steroid sulfatase respectively. Although compound 16a was less active than CA-4 in regard to its in vitro activity as an inhibitor of tubulin polymerization, it was effective as an inhibitor of arylsulfatase. This novel combretastatin A-4 sulfamate derivative has the potential to be developed as a dual inhibitor of tubulin polymerization and arylsulfatase for cancer therapy.

Two polymorphs and a solvatomorph of a new dimethylammonium polytungstate—decakis(dimethylammonium) dihydrogendodecatungstate, (Me2NH2)10(W12O42)·nH2O (n = 10 or 11)—have been synthesized. Their structures were characterized by single-crystal X-ray diffraction and solid-phase NMR methods. The shape of the dodecatungstate anions is essentially the same in all three structures, their interaction with the cations and water of crystallization, however, is remarkably variable, because the latter forms different hydrogen-bonded networks, and provides a highly versatile matrix. Accordingly, the N–H⋯O and C–H⋯O hydrogen bonds are positioned in each crystal lattice in a variety of environments, characteristic to the structure, which can be distinguished by solid-state 1H-CRAMPS, 13C, 15N CP MAS and 1H–13C heteronuclear correlation NMR. Thermogravimetry of the solvatomorphs also reflect the difference and multiformity of the environment of the water molecules in the different crystal lattices. The major factors behind the variability of the matrix are the ability of ammonium cations to form two hydrogen bonds and the rigidity of the polyoxometalate anion cage. The positions of the oxygen atoms in the latter are favourable for the formation of bifurcated and trifurcated cation–anion hydrogen bonds, some which are so durable that they persist after the crystals are dissolved in water, forming ion associates even in dilute solutions. The H atom involved in furcated hydrogen bonds cannot be exchanged by deuterium when the compound is dissolved in D2O. An obvious consequence of the versatility of the matrix is the propensity of these compounds to form multiple polymorphs.

The rotational spectrum of the 1:1 benzaldehyde-CO2 complex has been investigated by pulsed-jet Fourier transform microwave spectroscopy complemented with quantum chemical calculations. Two isomers, both characterized by one C···O tetrel bond (n → π* interaction) and one C-H···O hydrogen bond (n → σ* interaction), have been observed in the pulsed jet. Competition between tetrel bond and hydrogen bond has been disclosed by natural bond orbital analysis: Isomer I is characterized by one dominating CCO2···O tetrel bond (12.6 kJ mol-1) and a secondary (C-H)formyl···O hydrogen bond (2.2 kJ mol-1). On the contrary, the (C-H)···O hydrogen bond (7.6 kJ mol-1) becomes the dominant one in isomer II, while the CCO2···O tetrel bond (5.8 kJ mol-1) becomes much weaker with respect to that of isomer I. The relative population ratio of the two isomers was estimated to be NI/NII ≈ 2/1 by intensity measurements.

Supramolecular hydrogels attract extensive attention as waterborne biocompatible materials like biological tissues. Here we developed poly[N-(2-acetamidoethyl)acrylamide] (PAAE) supramolecular hydrogels with multiple hydrogen bonds, which exhibit ideal mechanical performances, such as strong resistance to compression and stretch, high stability in acidic or high ionic strength solution, excellent waterborne adhesiveness, self-healing and swelling behaviors. The small molecular precursor for PAAE hydrogels possesses great solubility up to 70 wt% in deionized water and superior infiltration capability to mouse brain tissues at 5 °C, and can be in situ polymerized at 30–45 °C and swollen in deionized water with a 1.75 times linear expansion factor. There is no noticeable loss of fluorescence intensity during the whole process from small molecular infiltration and polymerization to expansion. The mouse brain slices were embedded and used for expansion microscopy with enhanced optical resolution and preserved structure integrity.

In this study, two types of agricultural wastes, sugarcane bagasse (SB) and cassava root husks (CRHs), were used to fabricate biochars. The pristine biochars derived from SB and CRHs (SBB and CRHB, respectively) were modified using ZnO nanoparticles to generate modified biochars (SBB-ZnO and CRHB-ZnO, respectively) for the removal of Reactive Red 24 (RR24) from stimulated wastewater. Batch experiments were performed to evaluate the effects of ZnO nanoparticles' loading ratio, solution pH, contact time, and initial RR24 concentration on the RR24 adsorption capacity of biochars. The RR24 adsorption isotherm and kinetic data on SBB, SBB-ZnO3, CRHB, and CRHB-ZnO3 were analyzed. Results indicate that SB- and CRH-derived biochars with a ZnO nanoparticle loading ratio of 3 wt% could generate maximum adsorption capacities of RR24 thanks to the double growth on the BET surface of modified biochars. The RR24 adsorption capacities of CRHB-ZnO3 and SBB-ZnO3 reached 81.04 and 105.24 mg g−1, respectively, which were much higher than those of pristine CRHB and SBB (66.19 and 76.14, respectively) at an initial RR24 concentration of 250 mg L−1, pH 3, and contact time of 60 min. The adsorption of RR24 onto biochars agreed well with the pseudo-first-order model and the Langmuir isotherm. The RR24 adsorption capacity on modified biochars, which were reused after five adsorption–desorption cycles showed no insignificant drop. The main adsorption mechanisms of RR24 onto biochars were controlled by electrostatic interactions between biochars' surface positively charged functional groups with azo dye anions, pore filling, hydrogen bonding formation, and π–π interaction.

The isolable anionic oxoborane 3 and thioxoborane 4 have been assembled using a 1,2-bis(imino)acenaphthene ligand (Dip-BIAN). Structural characterization and DFT calculations confirmed that two compounds contain terminal doubly bonded B[double bond, length as m-dash]E (E = O, S) groups, respectively, in which only the B[double bond, length as m-dash]O group is associated with imidazolium via a hydrogen bond.

Anions perform several important functions in biological processes. Thus, structures that are able to interact with anions are of great relevance. Here, light is shed on the main characteristics of the bonds between the anions chloride (Cl−), bromide (Br−) and nitrite (NO2−) and the –CH groups of trioxane structures non-substituted and polarized by the ligands (i) –CH3, (ii) –CH2Cl, (iii) –CHCl2, and (iv) –CCl3. There is a less attractive recognition of the anions Cl−, Br− and NO2− using trioxane substituted by the –CH3 groups compared to the receptors non-substituted due to the destabilization of the electrostatic interactions C–H⋯(Cl−, Br− and NO2−). The presence of electron withdrawing groups in the receptor structure improves the interaction with the anions through more favorable σ bonds between the –CH groups and anions Cl−, Br− and NO2−. The anion NO2− is recognized with (i) more favorable and (ii) similar energy and rate by receptors containing (i) –CH3 and (ii) –CH2Cl, –CHCl2 or –CCl3, compared to anions Cl− and Br−. The lower values of the Pauli repulsion contribution in receptors⋯Cl− bonds when compared to the interactions receptors⋯Br− explain the more favorable recognition of the anion Cl− in relation to Br−. The larger recognition rate of the anion Cl− regarding to anion Br− is determined by more favorable electrostatic and orbital interactions. These data provide relevant information about the recognition of anions using C–H bonds and can be used to guide the development of new receptors.

A fundamental understanding of cyclodextrin-closo-dodecaborate inclusion complexes is of great interest in supramolecular chemistry. Herein, we report a systematic investigation on the electronic structures and intramolecular interactions of perhalogenated closo-dodecaborate dianions B12X122- (X = F, Cl, Br and I) binding to α-, β-, and γ-cyclodextrins (CDs) in the gas phase using combined negative ion photoelectron spectroscopy (NIPES) and density functional theory (DFT) calculations. The vertical detachment energy (VDE) of each complex and electronic stabilization of each dianion due to the CD binding (ΔVDE, relative to the corresponding isolated B12X122-) are determined from the experiments along α-, β- and γ-CD in the form of VDE (ΔVDE): 4.00 (2.10), 4.33 (2.43), and 4.30 (2.40) eV in X = F; 4.09 (1.14), 4.64 (1.69), and 4.69 (1.74) eV in X = Cl; 4.11 (0.91), 4.58 (1.38), and 4.70 (1.50) eV in X = Br; and 3.54 (0.74), 3.88 (1.08), and 4.05 (1.25) eV in X = I, respectively. All complexes have significantly higher VDEs than the corresponding isolated dodecaborate dianions with ΔVDE spanning from 0.74 eV at (α, I) to 2.43 eV at (β, F), sensitive to both host CD size and guest substituent X. DFT-optimized complex structures indicate that all B12X122- prefer binding to the wide openings of CDs with the insertion depth and binding motif strongly dependent on the CD size and halogen X. Dodecaborate anions with heavy halogens, i.e., X = Cl, Br, and I, are found outside of α-CD, while B12F122- is completely wrapped by γ-CD. Partial embedment of B12X122- into CDs is observed for the other complexes via multipronged B-XH-O/C interlocking patterns. The simulated spectra based on the density of states agree well with those of the experiments and the calculated VDEs well reproduce the experimental trends. Molecular orbital analyses suggest that the spectral features at low binding energies originated from electrons detached from the dodecaborate dianion, while those at higher binding energies are derived from electron detachment from CDs. Energy decomposition analyses reveal that the electrostatic interaction plays a dominating role in contributing to the host-guest interactions for the X = F series partially due to the formation of a O/C-HX-B hydrogen bonding network, and the dispersion forces gradually become important with the increase of halogen size.

Various factors, such as helical propensity and hydrogen bonds, control protein structures. A frequently used model protein, myoglobin (Mb), can perform 3D domain swapping, in which the loop at the hinge region is converted to a helical structure in the dimer. We have previously succeeded in obtaining monomer-dimer equilibrium in the native state by introducing a high α-helical propensity residue, Ala, to the hinge region. In this study, we focused on another factor that governs the protein structure, hydrogen bonding. X-ray crystal structures and thermodynamic studies showed that the myoglobin dimer was stabilized over the monomer when keeping His82 to interact with Lys79 and Asp141 through water moleclues and mutating Leu137, which was located close to the H-bond network at the dimer hinge region, to a hydrophilic amino acid (Glu or Asp). Molecular dynamics simulation studies confirmed that the number of H-bonds increased and the α-helices at the hinge region became more rigid for mutants with a tighter H-bond network, supporting the hypothesis that the myoglobin dimer is stabilized when the H-bond network at the hinge region is enhanced. This demonstrates the importance and utility of hydrogen bonds for designing a protein dimer from its monomer with 3D domain swapping.

The use of aliphatic amines as alkylating reagents in organic synthesis via C–N bond activation remains underdeveloped. We herein describe a novel ruthenium-catalysed and directing-group assisted protocol for the synthesis of meta-alkylated arenes via dual C–H and C–N activation. Bench-stable and easily handled redox-active Katritzky pyridinium salts derived from abundant amines and amino acid species were used as alkyl radical precursors. This catalytic reaction could accommodate a broad range of functional groups and provide access to various meta-alkylated products.

The conformational landscape of the monohydrated complex of N-allylmethylamine (AMA–w) was investigated for the first time using rotational spectroscopy from 8–20 GHz and quantum chemistry calculations. From a total of nine possible energy minima within 10 kJ mol−1, transitions for the two most stable conformers of AMA–w were detected, and assigned aided by DFT and ab initio MP2 predictions. The observed rotational transitions displayed characteristic hyperfine splittings due to the presence of the 14N quadrupolar nucleus. Quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) and natural bond orbital (NBO) analyses showed that the observed conformers of AMA–w are stabilized by two intermolecular interactions consisting of a dominant N⋯H–O and a secondary C–H⋯O hydrogen bond (HB) in which the water molecule acts simultaneously as a HB donor and acceptor. The HBs formed with water do not change the relative energy ordering of the most stable conformers of AMA but do affect the stability of higher energy conformations by disrupting the intramolecular forces responsible for their geometries. By comparing the intermolecular interaction energies with those of the monohydrates of the simplest primary (methylamine, MA), secondary (dimethylamine, DMA) and tertiary (trimethylamine, TMA) amines using symmetry-adapted perturbation theory (SAPT) calculations, we find that AMA forms the strongest bound complex with water. This is rationalized through the identification of subtle differences in stabilizing and destabilizing contributions across the amine–w series of complexes.

Herein, we first demonstrate a non-covalent strategy that extends the π-conjugation of fluorophores through bionic paired hydrogen-bond interactions. In well-designed molecular models, 1,8-naphtholactam (Np)-equipped molecules (TPE/HTPE-Np) exhibit highly efficient dual-state emission in a red-shifted region, whereas their acenaphthene (Ap)-equipped counterparts (TPE/HTPE-Ap) reserve typical AIE behaviors with short-wavelength emission. Single-crystal and theoretical analyses prove that these bionic hydrogen-bond interactions enable the facile formation of dimeric TPE/HTPE-Np, resulting in their larger delocalized π-electron conjugation, thereby playing a crucial role in their unique emission characteristics.

Porous materials bearing stepwise-controlled pore-shape change that are capable of executing sophisticated tasks are of considerable interest due to their fascinating features. In this work, we present a (3,4,6)-connected metal–organic framework built of 1D hinge-like zig–zag chain and tritopic ligand, formulated as (H3O)2[Zn3(dmtrz)2(tipa)2]·4H2O (MAC-20, Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole, H3tipa = 5-(2H-tetrazol-5-yl)isophthalic acid). By regulating the hinge angle and hydrogen bond interaction of 1D chain and tritopic ligand precisely, we realize a unique two-step pore-shape change in MAC-20 structure, which reveals that 1D chain and tritopic ligands have a synergistic effect on the structural transformation. Furthermore, the MAC-20 structure executes the sequential adsorption of indigo blue (ID) and sudan-I (SD-I) stepwise-controlled by trimethylamine and N,N-dimethylformamide, which offers the potential to exploit the flexible MOFs for smart multi-step stimuli-responsive applications.

Seven bent-bis(triazolyl)-based coordination polymers, [Zn(opbt)(nbdc)(H2O)]n (1, opbt = 1,1′-(oxybis(1,4-phenylene))-bis(1H-1,2,4-triazole), nbdc2− = 5-nitrobenzene-1,3-dicarboxylate), [Cd2(opbt)(cpa)2(H2O)]n (2, cpa2− = 2-carboxyphenylacetate), {[Cd(opbt)(sdb)(H2O)]·2H2O}n (3, sdb2− = 4,4′-sulfonyldibenzoate), [Co2(opbt)2(nbdc)2]n (4, nbdc2− = 5-nitrobenzene-1,3-dicarboxylate), {[Zn(opbt)(cydc)]·H2O}n (5, cydc2− = 5-cyano-1,3-benzenedicarboxylate), {[Zn(opbt)(mbdc)]·(G*)}n (6, mbdc2− = 5-methylbenzene-1,3-dicarboxylate, G* = 0.25DMF·0.5H2O·0.5H2mbdc) and {[Cd(opbt)(chdc)]·H2O}n (7, chdc2− = cis-1,2-cyclohexanedicarboxylate), were successfully synthesized in the presence of different auxiliary ligands. Compound 1 displays a 1D polymeric chain and the adjacent chains are further linked by hydrogen bonds to afford a 3D supramolecular architecture. Compound 2 is a 3D framework and exhibits a 3,3,3,3,3,5,7-connected 7-nodal net with the point symbol {3·4·5}{3·5·6}3{32·43·52·95·108·11}{4·62}2{43·5·62·94}. Compound 3 exhibits a three-fold interpenetrated 3D network with a 4-connected uninodal net with the point symbol {44·62}. Compound 4 is a 2D layer architecture. These layers are further regularly packed into a 3D supramolecular framework through π–π stacking interactions. Compound 5 reveals a four-fold interpenetrated 3D framework possessing a 4-connected dia network with the point symbol {66}. Compound 6 consists of 2D protuberant layers with the sql topology. These layers are further packed through π–π stacking interactions in an ABAB manner, resulting in the formation of a 3D supramolecular structure. Compound 7 possesses a 2D layer, which is further extended into a 3D supramolecular framework through interlayer π–π stacking interactions. These results indicate that the versatile coordination networks of opbt and the various dicarboxylate ligands play crucial roles in modulating the structural topologies of coordination networks. In addition, their thermal stabilities and photoluminescence properties were also investigated.

A highly efficient catalytic system was developed for the reaction between CO2 and propargylic alcohols for alkylidene cyclic carbonates. Ionic liquids (ILs) with different anions and cations were designed as cocatalysts, in order to find out the effect of the cation and the anion on this reaction. The results indicated that the effect of the cation was significant, especially the hydroxyl group on the cation played an important role due to the presence of a hydrogen bond. It was also found that the basicity of the anion was important for its catalytic activity, where the anion with moderate basicity gave the best activity. Moreover, this hydroxyl and azolate dual functionalized catalytic system showed excellent reusability and generality. It is worth mentioning that at a low concentration of CO2, this dual functionalized catalytic system showed excellent catalytic activity even in a gram-scale reaction, indicating its potential in carbon capture and utilization processes.

The excited-state intramolecular proton transfer (ESIPT) reaction of two phenol-quinoline molecules (namely PQ-1 and PQ-2) were investigated using time-dependent density functional theory. The five-(six-) membered-ring carbocycle between the phenol and quinolone moieties in PQ-1 (PQ-2) actually causes a relatively loose (tight) hydrogen bond, which results in a small-barrier (barrier-less) on an excited-state potential energy surface with a slow (fast) ESIPT process with (without) involving the skeletal deformation motion up to the electronic excitation. The skeletal deformation motion that is induced from the largest vibronic excitation with low frequency can assist in decreasing the donor-acceptor distance and lowering the reaction barrier in the excited-state potential energy surface, and thus effectively enhance the ESIPT reaction for PQ-1. The Franck-Condon simulation indicated that the low-frequency mode with vibronic excitation 0 → 1' is an original source of the skeletal deformation vibration. The present simulation presents physical insights for phenol-quinoline molecules in which relatively tight or loose hydrogen bonds can influence the ESIPT reaction process with and without the assistance of the skeletal deformation motion.

The inhibition mechanism of two homoisoflavonoids from Ophiopogon japonicus including methylophiopogonanone A (MO-A) and methylophiopogonanone B (MO-B) on tyrosinase (Tyr) was studied by multiple spectroscopic techniques and molecular docking. The results showed that the two homoisoflavonoids both inhibited Tyr activity via a reversible mixed-inhibition, with a half inhibitory concentration (IC50) of (10.87 ± 0.25) × 10−5 and (18.76 ± 0.14) × 10−5 mol L−1, respectively. The fluorescence quenching and secondary structure change of Tyr caused by MO-A and B are mainly driven by hydrophobic interaction and hydrogen bonding. Molecular docking analysis indicated that phenylmalandioxin in MO-A and methoxy in MO-B could coordinate with a Cu ion in the active center of Tyr, and interacted with amino acid Glu322 to form hydrogen bonding, occupying the catalytic center to block the entry of the substrate and consequently inhibit Tyr activity. This study may provide new perspectives on the inhibition mechanism of MO-A and MO-B on Tyr and serve a scientific basis for screening effective Tyr inhibitors.

Preorganization is a common strategy to align halogen bond (XB) donors to form two or more halogen bonds simultaneously. Previous approaches have utilized various non-covalent interactions such as steric interactions, π⋯π stacking, and hydrogen bond interactions. However, some of the introduced aligning interactions may compete with halogen bond interactions if the donors are employed in catalysis. To achieve thiourea-like properties, we have designed in silico several neutral bidentate halogen bond donors in whose structures the donor moieties are connected via covalent bonds. Compared to previous XB catalyst designs, the new design does not involve other potentially competitive non-covalent interactions such as hydrogen bonds. One of the designed XB donors can deliver strong halogen bonds, with a O–I distance as short as 2.64 A. Density functional theory (DFT) calculations predicted that our designed catalysts may catalyze important organic reactions on their own, particularly for those reactions that involve (developing) soft anions such as thiolates.

Multicomponent systems have been widely investigated to expand absorption spectra, ameliorate morphology and achieve high-performance organic solar cells (OSCs). Here, we reveal a novel quaternary OSC based on a PM6:Y6:SR197:PC71BM system with a power conversion efficiency (PCE) of up to 17.48%, one of the highest efficiencies in organic photovoltaics. The N–H bonds of SR197 react with the F atom of acceptor Y6 to form intermolecular hydrogen bonds that regulate the morphology of the blended film and inhibit bimolecular recombination, so that a PCE of 16.83% is achieved for the ternary OSC based on a PM6:Y6:SR197 system. However, the PCE of PM6:Y6:PC71BM-based devices is 16.72% due to the fullerene derivative PC71BM exhibiting strong isotropic transport ability. The quaternary OSC combines the advantages of the above two ternary devices, and it is noteworthy that SR197 can also form hydrogen bonds with PC71BM, which allows targeted morphology control and improved device stability while increasing photon utilization. Therefore, the efficiency of the quaternary device rose by 12% in contrast to the binary device (15.56%). Our results detail the use of a hydrogen bonding strategy to overcome the disadvantages of the difficult-to-control morphology of multiple component devices, which is a valid way to achieve high-performance quaternary OSCs.