Kind Of Weak Interaction Research Articles

How the Length of Through‐Space Conjugation Influences the Clusteroluminescence of Oligo(Phenylene Methylene)s

AbstractThe length and mode of conjugation directly affect the molecular electronic structure, which has been extensively studied in through‐bond conjugation (TBC) systems. Corresponding research greatly promotes the development of TBC‐based luminophores. However, how the length and mode of through‐space conjugation (TSC), one kind of weak interaction, influence the photophysical properties of non‐conjugated luminophores remains a relatively unexplored field. Here, we unveil a non‐linear relationship between TSC length and emission characteristics in non‐conjugated systems, in contrast to the reported proportional correlation in TBC systems. More specifically, oligo(phenylene methylene)s (OPM[4]‐OPM[7]) exhibit stronger TSC and prominent blue clusteroluminescence (CL) (≈440 nm) compared to shorter counterparts (OPM[2] and OPM[3]). OPM[6] demonstrates the highest solid‐state quantum yield (40 %), emphasizing the importance of balancing flexibility and rigidity. Further theoretical calculations confirmed that CL of these oligo(phenylene methylene)s was determined by stable TSC derived from the inner rigid Diphenylmethane (DPM) segments within the oligomers instead of the outer ones. This discovery challenges previous assumptions and adds a new dimension to the understanding of TSC‐based luminophores in non‐conjugated systems.

How the Length of Through-Space Conjugation Influences the Clusteroluminescence of Oligo(Phenylene Methylene)s.

The length and mode of conjugation directly affect the molecular electronic structure, which has been extensively studied in through-bond conjugation (TBC) systems. Corresponding research greatly promotes the development of TBC-based luminophores. However, how the length and mode of through-space conjugation (TSC), one kind of weak interaction, influence the photophysical properties of non-conjugated luminophores remains a relatively unexplored field. Here, we unveil a non-linear relationship between TSC length and emission characteristics in non-conjugated systems, in contrast to the reported proportional correlation in TBC systems. More specifically, oligo(phenylene methylene)s (OPM[4]-OPM[7]) exhibit stronger TSC and prominent blue clusteroluminescence (CL) (≈440 nm) compared to shorter counterparts (OPM[2] and OPM[3]). OPM[6] demonstrates the highest solid-state quantum yield (40 %), emphasizing the importance of balancing flexibility and rigidity. Further theoretical calculations confirmed that CL of these oligo(phenylene methylene)s was determined by stable TSC derived from the inner rigid Diphenylmethane (DPM) segments within the oligomers instead of the outer ones. This discovery challenges previous assumptions and adds a new dimension to the understanding of TSC-based luminophores in non-conjugated systems.

Crystal structure of bis(1,8-dibenzoyl-7-methoxynaphthalen-2-yl)terephthalate: Terephthalate phenylene moiety acts as bidentate hydrogen acceptor of bidirectional C-H···π non-classical hydrogen bonds

The title compound lies about a crystallographic inversion centre located at the terephthalate moiety. The two peri-benzoylnaphthalene units having atrope chirality are also situated centrosymmetrically. In the two peri-benzoylnaphthalene moieties, two benzoyl groups are substituted at 1 and 8 carbons of the naphthalene ring in anti-orientation. Then two absolute configurations of peri-benzoylnaphthalene moieties are consequently assigned as complementary to each other, i.e., one unit has R,R-configuration and the other S,S-one, respectively. The two benzoyl groups in peri-benzoylnaphthalene moiety and the terephthalate phenylene ring are non-coplanarly located against the naphthalene ring. The dihedral angles of each benzene ring of two benzoyl groups and terephthalate unit with the naphthalene ring are 73.73 and 75.96, and 71.79°. In molecular packing, several kinds of weak interactions are responsible to induce three-dimensional molecular network. Especially, the synergetic effect realized through the bidentate hydrogen acceptor function in bidirectional C-H···π non-classical hydrogen bonds by the terephthalate phenylene ring moiety plausibly plays the determining role.

On the Dynamic Mechanical Behavior and Importance of Weak Interactions in PS/PVME Blends

AbstractIn this work, the dynamic mechanical behavior and weak interactions in a miscible blend of polystyrene/poly (vinyl methyl ether) (PS/PVME) with a mass ratio of 3 : 1 (PS/PVME 75/25) were studied using DMA detection and solid‐state NMR methods. The results showed the miscibility of the blend and the evidence of the weak C−H to O hydrogen bonding between the aromatic H in PS and O of the methoxyl group in PVME. The 1H‐13C correlation spectrum indicated the diffusion time between 13C in OCH/OCH3 of PVME and Aromatic 1H of PS was at about millisecond level which confirmed the space affinity between the Aromatic 1H and OCH/OCH3 group in this mixture. Quantum calculations were made with four model systems in solutions by comparing the solvent toluene with CHCl3. In this way it was shown that the binding energy between PVME and CHCl3 was larger than the one between PVME and toluene, explaining why PVME and PS were miscible when using toluene as a solvent but not in CHCl3. The detailed components of the binding energy between PVME and solvent molecules were also analyzed with different methods which showed the similar result. These results reported here allows opportunities for finding new blend dependent on this kind of weak interaction or design of special polymers to enhance such weak interactions.

Electrochemical investigation of the intermolecular hydrogen bond on the surface of self-assembled monolayer

Intermolecular hydrogen bond, as a kind of weak interaction, plays a fundamental and important role in the molecular recognition process on cell membrane surface. Based on the complexity of the cell membrane and its microenvironment, the self-assembled monolayer with clear structure is used to simulate the cell membrane to construct the simulation system. The intermolecular hydrogen bond on the surface of the self-assembled is explored at the molecular level, which provided a new perspective for the study of molecular recognition on the cell membrane surface. In this paper, combined with the advantages of scanning electrochemical microscopy, the progress on the intermolecular hydrogen bond on the surface of self-assembled monolayer is introduced from the electrochemical viewpoint.

Mn2Cl4 Cluster Based Two-Dimensional Coordination Polymer for Dichromate Sensing Property

The new coordination polymer of {Mn2Cl4(L1)2}n (1, 1′ and 1′′ for different synthesis conditions) [L1 = 1,3,5-tris(4′-pyridyloxadiazole)-2,4,6-triethylbenzene] has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy and powder X-ray diffraction. As revealed by the single crystal X-ray diffraction, there exist two kinds of L1 ligands and one kind of Mn2Cl4 dimer cluster in complex {Mn2Cl4(L1)2}n. L1 and the Mn2Cl4 dimer form a 3 × 6 two-dimensional layer structure. Each 2D net is composed of Mn2Cl4 linking Mn2-organic cycles. The 2D nets are packed into 3D frameworks through kinds of weak interactions including C-H···N and C-H···Cl hydrogen bonds in the AB fashion. As the assembly reaction can be conducted at room temperature or 90 °C giving rise to 1 and 1′ respectively, the micro-sized products 1′′ can be easily obtained under open solvothermal condition. Finally, the photo-luminescence of the coordination polymer is applied to the harmful dichromate anion sensing in aqueous media. And a fast respond to Cr2O72− at low concentration is realized. The CCDC number of 1 and 1′ are 1977023 and 1977024, respectively.

Room-Temperature Ionic Liquid System Converting Fructose into 5-Hydroxymethylfurfural in High Efficiency

This report describes a dehydration of fructose into 5-hydroxymethylfurfural (HMF) promoted by ionic liquids [Bmim]Cl and [HNMP][CH3SO3] in ethanol solvent. Two intermediates captured in time-dependent HPLC determinations are identified and structurally characterized by in situ 1H NMR and online ESI(+)-MS/MS. Studies on the influence of the ionic liquids (ILs) on the formation and transformation of the intermediates indicate that [HNMP][CH3SO3] promotes the formation of the intermediates, while [Bmim]Cl promotes their transformation. The contribution of the component ions of the ILs to the dehydration originates from their activation toward the leaving of OH on fructose or the intermediates via the formation of multiple hydrogen bonds. This kind of weak interaction appears only at low temperature. On the basis of the present study and the related literature, we propose a concerted mechanism for the binary IL-promoted conversion of fructose into HMF at room temperature.

Conceptual quantum chemical analysis of bonding and noncovalent interactions in the formation of frustrated Lewis pairs.

The contributions of covalent and noncovalent interactions to the formation of classical adducts of bulky Lewis acids and bases and frustrated Lewis pairs (FLPs) were scrutinized by using various conceptual quantum chemical techniques. Significantly negative complexation energies were calculated for fourteen investigated Lewis pairs containing bases and acids with substituents of various sizes. A Ziegler-Rauk-type energy decomposition analysis confirmed that two types of Lewis pairs can be distinguished on the basis of the nature of the primary interactions between reactants; dative-bond formation and concomitant charge transfer from the Lewis base to the acid is the dominant and most stabilizing factor in the formation of Lewis acid-base adducts, whereas weak interactions are the main thermodynamic driving force (>50 %) for FLPs. Moreover, the ease and extent of structural deformation of the monomers appears to be a key component in the formation of the former type of Lewis pairs. A Natural Orbital for Chemical Valence (NOCV) analysis, which was used to visualize and quantify the charge transfer between the base and the acid, clearly showed the importance and lack of this type of interaction for adducts and FLPs, respectively. The Noncovalent Interaction (NCI) method revealed several kinds of weak interactions between the acid and base components, such as dispersion, π-π stacking, C-H⋅⋅⋅π interaction, weak hydrogen bonding, halogen bonding, and weak acid-base interactions, whereas the Quantum Theory of Atoms in Molecules (QTAIM) provided further conceptual insight into strong acid-base interactions.

Tuning interionic interaction for highly selective in vivo analysis.

The development of highly selective methodologies to enable in vivo recording of chemical signals is of great importance for studying brain functions and brain activity mapping. However, the complexity of cerebral systems presents a great challenge in the development of chem/(bio)sensors that are capable of directly and selectively recording bioactive molecules involved in brain functions. As one of the most important and popular interactions in nature, interionic interaction constitutes the chemical essence of high specificity in natural systems, which inspires us to develop highly selective chem/(bio)sensors for in vivo analysis by precisely engineering interionic interaction in the in vivo sensing system. In this tutorial review, we focus on the recent progress in the tuning of interionic interaction to improve the selectivity of biosensors for in vivo analysis. The type and property of the interionic interaction is first introduced and several strategies to improve the selectivity of the biosensors, including enzyme-based electrochemical biosensors, aptamer-based electrochemical biosensors, and the strategies to recruit recognition molecules are reviewed. We also present an overview of the potential applications of the biosensors for in vivo analysis and thereby for physiological investigations. Finally, we present the major challenges and opportunities regarding the high selectivity of in vivo analysis based on tuning interionic interaction. We believe that this tutorial review provides critical insights for highly selective in vivo analysis and offers new concepts and strategies to understand brain chemistry.

A Systematic Investigation and Insight into the Formation Mechanism of Bilayers of Fatty Acid/Soap Mixtures in Aqueous Solutions

Vesicles are the most common form of bilayer structures in fatty acid/soap mixtures in aqueous solutions; however, a peculiar bilayer structure called a "planar sheet" was found for the first time in the mixtures. In the past few decades, considerable research has focused on the formation theory of bilayers in fatty acid/soap mixtures. The hydrogen bond theory has been widely accepted by scientists to explain the formation of bilayers. However, except for the hydrogen bond, no other driving forces were proposed systematically. In this work, three kinds of weak interactions were investigated in detail, which could perfectly demonstrate the formation mechanism of bilayer structures in the fatty acid/soap mixtures in aqueous solutions. (i) The influence of hydrophobic interaction was detected by changing the chain length of fatty acid (C(n)H(2n+1)COOH), in which n = 10 to 18, the phase behavior was investigated, and the phase region was presented. With the help of cryogenic transmission electron microscopy (cryo-TEM) observations, deuterium nuclear magnetic resonance ((2)H NMR), and X-ray diffraction (XRD) measurements, the vesicles and planar sheets were determined. The chain length of C(n)H(2n+1)COOH has an important effect on the physical state of the hydrophobic chain, resulting in an obvious difference in the viscoelasticity of the solution samples. (ii) The existence of hydrogen bonds between fatty acids and their soaps in aqueous solutions was demonstrated by Fourier transform infrared (FT-IR) spectroscopy and molecule dynamical simulation. From the pH measurements, the pH ranges of the bilayer formation were at the pKa values of fatty acids, respectively. (iii) Counterions can be embedded in the stern layer of the bilayers and screen the electrostatic repulsion between the COO(-) anionic headgroups. FT-IR characterization demonstrated a bidentate bridging coordination mode between counterions and carboxylates. The conductivity measurements provided the degree of counterion binding (β = 0.854), indicating the importance of the counterions.

On the Covalent Character of Rare Gas Bonding Interactions: A New Kind of Weak Interaction

At the averaged quadratic coupled-cluster (AQCC) level, a number of selected rare gas (Rg) containing systems have been studied using the quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and several other analysis methods. According to the criteria for a covalent bond, most of the Rg-M (Rg = He, Ne, Ar, Kr, Xe; M = Be, Cu, Ag, Au, Pt) bonds in this study are assigned to weak interactions instead of van der Walls or covalent ones. Our results indicate that the rare gas bond is a new kind of weak interaction, like the hydrogen bond for example.

Kinetics and thermodynamics of adsorption of cadusafos on soils

Laboratory batch experiments were designed to study the adsorption of cadusafos on two types of soils: clay loamy and sandy, collected from two regions around the Nile Delta in Egypt. The adsorption process is fast reaching equilibrium in 60 min, decreases with increasing soil mass and independent on pH in the range 3–11. The experimental results were well fitted to linear partition model, and to a lesser extent to Freundlich non-linear model, Temkin and Dubinin–Radushkevich models. However, the 1/ n parameter of Freundlich relation being of value around one supported the linear partition model. The K d values obtained from the linear model were 4.20 and 2.74 L/g for sandy and clay soils, respectively. The energy of adsorption calculated from D–R equation was 4.36 and 5.04 kJ/mol for clay and sandy soils, respectively, in the range assigned to physical forces. This kind of weak interaction, together with pH-independence implies that for the studied soils the organic content (that is higher in the clay soil) is not a major parameter in the adsorption of cadusafos. Water movement taking place more readily in sandy soil caused increased uptake relative to the case of clay soil. The higher uptake in sandy soil denotes that cadusafos may be mobile with a potential to leach and eventually pollutes ground water and surface water. The kinetics of adsorption was well fitted by the pseudo-second order equation. The intraparticles diffusion is of lower significance in case of sandy soil than in clay soil. Thermodynamic parameters indicated that the adsorption is spontaneous, endothermic accompanied by increase in entropy.

Long-range corrected density functional study on weakly bound systems: Balanced descriptions of various types of molecular interactions

The long-range correction scheme for the density functional theory, combined with a van der Waals functional, is examined for its applicability to a wide variety of weakly bonded complexes including dispersion, dipole-induced dipole, dipole-dipole, and hydrogen-bonded complexes. The present method is able to describe geometries and binding energies of all these complexes accurately. Explicit inclusion of the long-range exchange and dispersion interactions is found to be important for the balanced description of various kinds of weak interactions. The present method is a promising alternative for high-level ab initio methods in calculations of large and complex systems, because it gives equally correct descriptions for various types of molecular interactions with much less computational cost.

Derivation of the thermodynamic parameters involved in the elucidation of protein thermal profiles

Figure 3 (A) fo as a function of urea concentration. The arrows indicate the points that were used for calculating Ko and AGo. (B) Plot of AGo versus urea molarity for calculation of AGo(H20) References i Robinson, C Vet al (1994) Nature 372,646-651 2Anfinsen, C B (1973) Science 181,223-230 3Creighton, T E (1990) Biochem J 270, 1-16 4Lowry, O H, Rosebrough, N J, Farr, A L and Randall, R J (1951) J Biol Chem 193, 265-275 5Edward, F B , Rombauer, R B and Campbell, B J (1969) Biochim Biophys Acta 194, 234-245 6Tanford, C (1968) Adv Prot Chern 3, 121-282 7pace, C N (1975) Crit Rev Biochem 3, 1-43 8Pace, C N (1986) Methods Enzymol 131,266-280 0307-4412(95)00049-6 Derivation of the Thermodynamic Parameters Involved in the Elucidation of Protein Thermal Profiles A A SABOURY and A A MOOSAVI-MOVAHEDI* Institute of Biochemistry and Biophysics* University of Tehran and Department of Chemistry Terbiat-Modares University Tehran, Iran Introduction Globular proteins are large molecules. They contain typically 102-103 amino-acid residues ie 103-104 atoms. The total covalent bond energy is hence of the order of 105 joules per mole. In dramatic contrast, the forces which determine the three- dimensional structure are small. The total energy involved in the folding process for an entire protein molecule is comparable with that involved in one single covalent bond. Furthermore, this represents the resultant of a large number of different kinds of weak interactions, both intra-molecular and between the protein and the surrounding solvent. [This is not unrelated to the difficulties involved in predicting the secondary and tertiary structure from the primary sequence]. The equilibrium state of the native folded protein must therefore be regarded as representing a delicate balance between a large number of weak interactions each of which is sensitive to temperature and the state of the surrounding solvent (ie pH, ionic strength, presence of hydrogen bond breaking solutes such as urea, presence of amphiphilic compounds which affect the balance of hydrophobic and hydrophilic interactions.) Disruption of the tertiary structure to the extent that there is loss of biochemical activity is known as denaturation. Clearly on the basis of what has been said above this may involve very minor energy changes. The main purpose of denaturation studies has always been to provide additional information on the structure, properties, and function of proteins. 1-3 Denaturation can be brought about in many ways. These include thermal denaturation (by raising the temperature), 4'5 chemical denatur- ation (by urea or ~guanidinum chloride)'

A Possible Existence of the Second Kind of Weak Interaction

A Possible Existence of the Second Kind of Weak Interaction