Different Types Of Hydrogen Bonds Research Articles

Chemical bonds and hair behaviour-A review.

When undertaking any review of the structure of the hair and its mechanical properties it becomes apparent that the overall behaviour of keratin fibres is commonly attributed to the presence of hydrogen, disulfide and ionic bonds. The action of physico-chemical agents used during various cosmetic treatments is viewed as the result of an interaction with these bonds. Thus, the breaking of bonds by chemical agents, or via mechanical or thermal stresses, affects the relative balance of disulfide and hydrogen bonds and the contribution of hydrophobic interactions, which are all important factors that may alter hair behaviour. Generally, these chemical bonds are considered as responding homogeneously to the environmental and cosmetic factors. This unitary image is challenged, however, by evaluating the results of chemical, nanomechanical, tensile and thermal measurements, which suggest that disulfide bonds may be grouped into several types, according to their location within the fibre and the way they respond to various agents. A compensatory effect of newly formed hydrogen bonds for broken disulfide bonds may also be seen, and additionally involves different types of hydrogen bonds. As a result, the picture of chemical bonding in hair appears to be far from a homogeneous one. In addition, it is apparent that further investigation is required for clarifying the action of ionic bonds and hydrophobic interactions within the hair fibre. The present review aims, thus, at offering a deeper background for understanding how the hair behaves under various conditions.

Intermolecular Forces Regulating the Phase-Transition Temperatures in Organic-Inorganic Hybrid Materials.

Organic-inorganic hybrid phase-transition materials have attracted widespread attention in energy storage and sensor applications due to their structural adaptability and facile synthesis. However, increasing the phase-transition temperature (Tc) effectively remains a formidable challenge. In this study, we employed a strategy to regulate intermolecular interactions (different types of hydrogen bonds and other weak interactions), utilizing bismuth chloride as an inorganic framework and azetidine, 3,3-difluoro azetidine, and 3-carboxyl azetidine as organic components to synthesize three compounds with different Tc values: [C3H8N]2BiCl5 (1, 234 K), [C3H6NF2]3BiCl6 (2, 256 K), and [C4H8O2N]3BiCl6 (3, 350 K). 1 is a one-dimensional chain structure and 2 and 3 are zero-dimensional structures. Analysis of the crystal structure and the Hirshfeld surface and 2D fingerprints further suggests that the intermolecular forces are efficiently modulated. These findings emphasize the efficacy of our strategy in enhancing Tc and may facilitate further research in this area.

Quantum chemical study of tautomeric equilibriums, intramolecular hydrogen bonds, and π-electron delocalization in the first singlet and triplet excited states of 2-selenoformyl-3-thioxo-propionaldehyde

In the present study, the tautomeric process, intramolecular hydrogen bonding (IMHB), and π-electron delocalization (π-ED) of 2-selenoformyl-3-thioxo-propionaldehyde (STP) in the first singlet and triplet excited states were investigated by CIS and TD-DFT methods. The relative energies of hydrogen-bonded tautomers in both excited states indicate that the thiol/enol conformers are the most/least stable forms. In this regard, a detailed analysis of various tautomeric equilibriums, different types of hydrogen bonds, and π-electron delocalization was performed. The electronic energies of different tautomers indicate the thermodynamic preference of thiol with respect to the other forms. Furthermore, the low activation energy barriers of thione⇄thiol equilibrium also show the kinetic preference of thiol. On the other hand, the estimation of different hydrogen bond energies emphasizes the stronger IMHB of enol. Moreover, the evaluation of π-ED by the structural parameter of Gilli (λ) represents the significance of electron mobility in the enol conformers. Consequently, the duality between the IMHB and π-ED with the thermodynamic stability order of tautomers indicates that the tautomeric phenomenons play a dominant role in determining the stability of the benchmark structures in both singlet and triplet excited states.

Computational investigation of the conformer selective complexes of 1,2,3,4-tetrahydroisoquinoline: Ammonia (THIQ: NH3) in S0

Three low-energy conformations are identified in 1,2,3,4-tetrahydroisoquinoline (THIQ): NH3 complexes. The lone pairs on N atoms strongly affects the conformational landscape. Both density functional theory (DFT) and MP2 levels of computations yield consistent results. Multiple PESs corresponding to different types of hydrogen bonds are drawn to account for all possible complexes. Ten complexes are identified. The global minimum contains a strong N-H⋅⋅⋅N and a weak N-H⋅⋅⋅π hydrogen bonds where NH3 is an H bond acceptor. In the remaining two complexes ammonia acts as a donor. All the low-energy complexes which can show intermolecular proton transfer were studied in detail although none shows PT with a single NH3 molecule. The intermolecular vibrational modes are critically analyzed and the relative shifts in the characteristic modes of ammonia are explained. Types and sites for H-bonding can be ascertained from the vibrational analyses. Changes in molecular electrostatic potentials (MEP) on complex formation are explained and confirm our computational results. We suggest further experiments to confirm our key observations.

Green preparation of robust hydrophobic bio-based epoxy resin with low dielectric constant

Epoxidized soybean oil (ESO) thermosets show poor performance owing to the low cross-linking density and flexibility of their backbone structure. Herein, fully bio-derived benzoxazine (GD) cured ESO thermosets (PGEs) with high-performance were prepared through a green process. As a curing agent, GD improved the cross-linking density and rigidity of ESO resins. Moreover, different types of hydrogen bonds formed in the PGEs, further strengthening the intermolecular interactions. Therefore, the glass transition temperature (Tg) and tensile strength of PGEs attained 93 °C and 34 MPa, respectively, which are higher than those reported for conventional ESO resins. Additionally, PGEs exhibited substantial hydrophobicity and a low dielectric constant, which can be associated with complex intermolecular and intramolecular hydrogen bonds within the thermoset network. Furthermore, as the GD content in PGE increased, the dielectric constant and water absorption of the polymer reduced to 2.72 % and 0.52 %, respectively. Herein, the preparation of novel all-biological ESO thermosets using GD as the curing agent is reported, providing a green and convenient strategy for the design of high-performance ecological materials.

Energetic Ordering of Hydrogen Bond Strengths in Methanol-Water Clusters: Insights via Molecular Tailoring Approach.

In this work, we examine the strength of various types of individual hydrogen bond (HB) in mixed methanol-water Mn Wm , (n+m=2 to 7) clusters, with an aim to understand the relative order of their strength, using our recently proposed molecular tailoring-based approach (MTA). Among all the types of HB, it is observed that the OM -H…OW HBs are the strongest (6.9 to 12.4 kcal mol-1 ). The next ones are OM -H…OM HBs (6.5 to 11.6 kcal mol-1 ). The OW -H…OW (0.2 to 10.9 kcal mol-1 ) and OW -H…OM HBs (0.3 to 10.3 kcal mol-1 ) are the weakest ones. This energetic ordering of HBs is seen to be different from the respective HB energies in the dimer i. e., OM -H…OM (5.0 to 6.0 kcal mol-1 )>OW -H…OM (1.5 to 6.0 kcal mol-1 )>OM -H…OW (3.8 to 5.6 kcal mol-1 )>OW -H…OW (1.2 to 5.0 kcal mol-1 ). The plausible reason for the difference in the HB energy ordering may be attributed to the increase or decrease in HB strengths due to the formation of cooperative or anti-cooperative HB networks. For instance, the cooperativity contribution towards the different types of HB follows: OM -H…OW (2.4 to 8.6 kcal mol-1 )>OM -H…OM (1.3 to 6.3 kcal mol-1 )>OW -H…OW (-1.0 to 6.5 kcal mol-1 )>OW -H…OM (-1.2 to 5.3 kcal mol-1 ). This ordering of cooperativity contribution is similar to the HB energy ordering obtained by the MTA-based method. It is emphasized here that, the interplay between the cooperative and anti-cooperative contributions are indispensable for the correct energetic ordering of these HBs.

Study of the structural features and solvent effects using ab initio molecular dynamics and energy decomposition analysis of atogepant in water and ammonia

Atogepant is a new drug developed for treating migraine in adults, marking it active with a calcitonin gene-related peptide (CGRP) receptor antagonist, which can be used to prevent migraine. The main objective of this manuscript is to study the structure and interaction of atogepant with solvents like water and ammonia. We optimized the molecule using the DFT method and did the conformational analysis. A potential energy scan was conducted to ascertain the conformation preference of the compound and found that global minima are at the angles 60, 180, and 300 0 with respect to the C30-C38 bond. The electronic spectra were produced using RCAM-B3LYP functional and identical basis sets with different polar and nonpolar solvents. Methanol showed excellent solvation energy –33.5448 kcal/mol and more interactions in implicit studies. Qualitative studies indicated that the compound has more non-covalent interactions with water when compared to ammonia. Local energy decomposition analysis using DLPNO/CCSD(T) level revealed the exact type of interaction between the drug and water/ammonia. Later we studied the interaction between the molecule and explicit solvent molecules using ab initio molecular dynamics simulations and found that the drift velocity is more complex with water. Physico-chemical properties like reactive sites, bioactivities, stabilities, solvation energy, occupancies of electrons in atomic and bonding orbitals, different types of hydrogen bonds, the steric force of interactions, delocalization of electrons, and reactive sites of nucleophiles, and electrophiles are also reported.

Ultra-robust, self-healable and recyclable polyurethane elastomer via a combination of hydrogen bonds, dynamic chemistry, and microphase separation

Flexibility, robustness, transparency, and recyclability are critical to the application of self-healing polymer materials in the field of flexible electronics. However, integrating all the above properties remains a huge challenge to date. In this work, we put forward a facile strategy to prepare polyurethane (PU) elastomer with ultra-high strength and self-healing performance based on hydrogen bonds, disulfide dynamic chemistry, and microphase separation at the same time. Three different self-healing PUs were obtained by introducing disulfide bonds and different types of hydrogen bonds. A robust, transparent, and recyclable PU with amino-terminated chain extender (PUA) with fast and efficient self-healing performance was prepared. The mechanical and self-healing properties of the PUA were effectively balanced by the synergistic effect of reversible interaction of disulfide bonds and the formation of microphase separated structure. The results indicated that the PUA exhibited high transparency up to 90% and excellent mechanical property, e.g. the tensile strength and elongation at break can reach 37.10 MPa and 1080%, respectively. Meanwhile, it can achieve a high self-healing efficiency of 96.8% at 80 °C for 4 h and maintain 84% of the initial mechanical strength even after four times of recycling. Moreover, the colloid graphite/PUA flexible strain sensor was prepared by the combination of colloid graphite and PUA, which can accurately detect both large and tiny scale deformations.

Hybrid Nafion Membranes of Ionic Hydrogen-Bonded Organic Framework Materials for Proton Conduction and PEMFC Applications.

As the high-power density and environmentally friendly energy resources, proton exchange membrane fuel cells (PEMFCs) have a promising future in portable power generation. Herein, the hybrid Nafion membranes of ionic hydrogen-bonded organic frameworks (iHOFs) for PEMFC applications are demonstrated. By adjusting the position of sulfonic groups on naphthalene disulfonic acid compounds, four iHOFs with different types of hydrogen bonds were synthesized successfully based on 1,1'-diamino-4,4'-bipyridylium and naphthalene disulfonic acid. The formation of hydrogen bond interactions between amino and sulfonate groups provides a rich hydrogen bond network, which makes such iHOFs have high conductivity, and the maximum value is 2.76 × 10-3 S·cm-1 at 100 °C and 98% RH. Besides, composite membrane materials were obtained by mixing Nafion and iHOFs, and the maximum proton conductivity values can achieve 1.13 × 10-2 S·cm-1 for 6%-iHOF-3/Nafion and 2.87 × 10-3 S·cm-1 for 6%-iHOF-4/Nafion membranes at 100 °C under 98% RH. Through the H2/O2 fuel cell performance test by using iHOF/Nafion as the solid electrolyte, the maximum power and current density values of hybrid membranes are 0.36 W·cm-2 and 1.10 A·cm-2 for 6%-iHOF-3/Nafion and 0.42 W·cm-2 and 1.20 A·cm-2 for 6%-iHOF-4/Nafion at 80 °C and 100% RH. This work provides a practicable approach for establishing high-performance proton exchange hybrid membranes by doping high proton-conducting iHOFs into the Nafion matrix.

HYDROGEN BONDS IN THE FORMATION OF COPPER(II) 1,10-PHENANTHROLINE HYDROXYCARBOXYLATOGERMANATE CRYSTALS USING HIRSHFELD SURFACE ANALYSIS

This article is dedicated to the investigation of crystalline structure in the complex cation-anionic compounds Cu(Phen)2Cl]2[Ge(HCit)2]⋅6H2O (I), [Cu(Phen)3]2[Ge2(OH)(HTart)(μ-Tart)2]·11H2O (II), [CuCl(Phen)2]4[{Ge2(OH)2(μ-Tart)2}Cl2]·4Н2О (III), [Cu(Phen)3]2[(OH)2Ge2(μ-HXylar)4Ge2(μ-OH)2]·8H2O (IV), [CuCl(Phen)2]4[(OH)2Ge2(μ-HXylar)4Ge2(μ-OH)2]·8H2O (V) using Hirshfeld surface analysis. This method has showed itself as an effective tool for analysis of intermolecular interactions, such as hydrogen bonds or weaker C…H and С…Н…p connections. Three-dimensional picture of close interactions in the crystal was built for each of the compounds I–V, where short connections are red-colored, while others – weaker and shorter – are light areas and small spots. It was established that in the structures of all compounds different types of hydrogen bonds are presented: bifurcate connections, symmetrical О-Н…О, С-Н…С and asymmetrical ones with water molecules. Two-dimensional histograms – 2D-fingerprint plots, allowed to evaluate quantitively connections in the crystals and establish that H…O/O…H and H…H interactions make the biggest contribution to the total surface area. The presence of the big number of crystallization water molecules is determinant for the formation of complex system of hydrogen bonds and strengthening of the structure, that otherwise would be unstable because of the big size of cations and anions. Due to the fact, that all compounds have the same complexing agent Ge(IV), structure of the anion is determined by polydentate ligand. Obtained results are important for the further development of the water role in the processes of crystallization, crystal formation, electrical dissociation and, especially, dissolving of coordination compounds in biological systems.

Mechanisms on the stability and instability of water-in-oil emulsion stabilized by interfacially active asphaltenes: Role of hydrogen bonding reconstructing

Chemical demulsification is the most commonly used demulsification method for the separation of oil–water emulsions (W/O) in petroleum industry. Previous experiments demonstrate that the interfacially active asphaltenes (IAA) play the key role in stabilizing the heavy oil–water emulsions. Herein, the molecular dynamic simulation has been applied to reveal the molecular mechanisms on the stability and instability of the IAA-stabilized oil–water emulsions. It is found that IAA could accumulate at the oil–water interface and self-aggregate to form viscoelastic interfacial film through π-π stacking, hydrogen bonds (intermolecular and intramolecular) and other non-covalent bonds. Different types of hydrogen bonds (i.e., S = O…H-O, R-OH…H-O, N-H…N-R, S-H…S = O, S-H…S-R) are found between the IAA molecules due to the presence of heteroatoms (e.g., N, O, S) in IAA. Increasing the IAA concentration would increase the thickness of the IAA film which plays the key roles in stabilizing the emulsions. When the newly synthesized demulsifier (i.e., MJTJU-2) was added into the oil–water emulsion system, the oxygen groups (i.e., hydroxyl, ester groups, carboxyl groups, ether group) in demulsifier could weaken (at least 50%) or even break the hydrogen bonds and π-π stacking between IAAs and form new stronger hydrogen bonds with water molecules. This hydrogen bond reconstruction facilitates the breaking of the IAA film at the oil–water interface, allowing the coalescence of the water droplets in oil phase. This work would provide fundamental understanding for developing new way to efficiently demulsify the petroleum or similar oil–water emulsions.

Synthesis, characterization, DNA binding ability, in vitro cytotoxicity, electrochemical properties and theoretical studies of copper(II) carboxylate complexes

Four copper(II) carboxylate complexes, namely [Cu2(μ-3,5-dinitrobenzoate-O,O')4(4-(dimethylamino)benzaldehyde)2] (1), [Cu2(μ-benzoate-O,O')4(benzoic acid)2] (2), [Cu2(μ-benzoate-O,O')4(H2O)2] [Cu(benzoate-O,O')2(imz)2].2H2O (3) and [Cu(benzoate-O,O')2(2-Me-imz)2] (4) (imz = imidazole, 2-Me-imz = 2-methyl-imidazole), were synthesized and comprehensively characterized by elemental analysis, spectroscopic methods, single crystal X-ray diffraction, cyclic voltammetry (CV), topological analysis as well as theoretical studies. Single crystal X-ray diffraction revealed that products 1 and 2 are dinuclear paddle-wheel complexes, compound 3 is a co-crystal containing mononuclear and dinuclear blocks, while compound 4 is a mononuclear complex. Hirshfeld surface analysis of the compounds rationalized different types of hydrogen bonds, which also lead to the generation of H-bonded networks in 3 and 4. Their topological analysis disclosed a uninodal 4-connected 2D layer with sql topology in 3 and a uninodal 2-connected 1D chain with 2C1 topology in 4. The interaction of 1–4 with calf thymus DNA was investigated by UV–visible and fluorescence spectroscopy, revealing a moderately strong non-intercalative mode of interaction. In vitro cytotoxicity study of the complexes on HepG2 (human liver hepatocellular carcinoma) cell lines revealed a significant inhibition activity. Electrochemical study of the complexes in CH3CN (1–3) and DMSO (4) solution showed a one electron transfer corresponding to Cu(III)Cu(II)/Cu(II)Cu(II) and Cu(II)Cu(II)/Cu(I)Cu(II) redox couples. The ΔE and Ipa/Ipc values suggest that the redox couples are quasireversible. The DFT study was performed to further rationalize the crystal structures and nuclearity of the obtained copper(II) complexes.

A theoretical study of hydrogen-bonded molecular clusters of sulfuric acid and organic acids with amides

Amides, a series of significant atmospheric nitrogen-containing volatile organic compounds (VOCs), can participate in new particle formation (NPF) throught interacting with sulfuric acid (SA) and organic acids. In this study, we investigated the molecular interactions of formamide (FA), acetamide (AA), N-methylformamide (MF), propanamide (PA), N-methylacetamide (MA), and N,N-dimethylformamide (DMF) with SA, acetic acid (HAC), propanoic acid (PAC), oxalic acid (OA), and malonic acid (MOA). Global minimum of clusters were obtained through the association of the artificial bee colony (ABC) algorithm and density functional theory (DFT) calculations. The conformational analysis, thermochemical analysis, frequency analysis, and topological analysis were conducted to determine the interactions of hydrogen-bonded molecular clusters. The heterodimers formed a hepta or octa membered ring through four different types of hydrogen bonds, and the strength of the bonds are ranked in the following order: SOH•••O > COH•••O > NH•••O > CH•••O. We also evaluated the stability of the clusters and found that the stabilization effect of amides with SA is weaker than that of amines with SA but stronger than that of ammonia (NH3) with SA in the dimer formation of nucleation process. Additionally, the nucleation capacity of SA with amides is greater than that of organic acids with amides.

Hydration Structure and Dynamics of the Favipiravir Antiviral Drug: A Molecular Modelling Approach

Abstract The hydration structure of the Favipiravir antiviral drug, at infinite dilution in water, was investigated by employing a systematic molecular modelling approach. An effective interaction potential model was employed for Favipiravir, using the intramolecular geometry and charge distribution from quantum chemical calculations performed in the present treatment and adopting well-established Lennard-Jones parameters. The hydration structure and related dynamics were further investigated by means of classical molecular dynamics simulations. These calculations have revealed the existence of different types of hydrogen bonds between Favipiravir and the surrounding water molecules, with continuous lifetimes in the sub picosecond range and intermittent lifetimes in the range of 0.8–5.4 ps. The self-diffusion coefficient of Favipiravir at 298.15 K was found to be three times lower than the value obtained for water in solution, while comparable to the values measured for other common painkillers, anti-inflammatory drugs, antibiotics and corticosteroids for asthma treatment. It was also revealed that the rotational motions of Favipiravir are more retarded in comparison with water and this is reflected in the calculated reorientational correlation times of specific intramolecular vectors. The results obtained could be useful for further pharmacokinetic and computer-aided docking studies to evaluate the efficiency of this antiviral drug.

Vibrational spectral, density functional theory and molecular docking analysis on 4-nitrobenzohydrazide

To understand the structural behavior of C-nitro compound 4-nitrobenzohydrazide (4NBH), a detailed spectroscopic study has been taken up. Spectral analyses of 4NBH molecule have been experimentally investigated in solid phase by FT-IR, FT-Raman, UV–visible and NMR techniques. The molecular structure has been optimized by using the B3LYP/6–311++G (d,p) calculations. Normal co-ordinate analysis (NCA) has been carried out to perform comprehensive vibrational spectral assignments. Natural bond orbital analysis (NBO) explains the stability and different types of hydrogen bonds with in the molecule. UV–Vis spectrum helps to found the band gap energy of 4NBH molecule and the electronic properties are computed with TD-DFT method. The 1H and 13C NMR chemical shifts are recorded and analyzed. The interpreted HOMO and LUMO energies indicate the chemical stability of the molecule. The chemical reactivity sites have been revealed by fukui function and molecular electrostatic potential (MEP) analysis. Docking studies have been conducted to predict 4NBH anti-tubercular activity against four transaminase-Bio A type PDB's. In-vitro analyses have been performed with fungal and bacterial pathogens Aspergillus niger and E.Coli.

The role of hydrogen bonds in TAG derivative-based oleogel structure and properties

Glycerol monosterate (GMS) and stearic acid (SA) share a similar carbon chain structure while SA has a carboxyl head group and GMS has two free hydroxyl groups. The current research focuses on the relationship between GMS and SA chemical structure, nano and mesoscale crystal structure, and the oleogel macroscopic characteristics. Molecular analysis revealed the formation of different types of hydrogen bonds, which disappear upon temperature increase at different temperatures. Nano-structural analysis exhibited tight and ordered lamellar structures for SA compared with loosely packed short lamellar structures in GMS oleogel, presumably due to its larger hydrophilic head group. Microstructure imaging revealed ordered anisotropically orientated needle-like crystals in SA and isotopically ordered braid-like crystals in GMS oleogels. Mechanical analysis revealed that gel strength is enhanced when crystal structure is isotropically oriented, similar behavior seen is composite materials, where the structuring agent crystals behave like a reinforcing agent within the oil matrix.

Freezing the Motion in Hydroxy-Functionalized Ionic Liquids-Temperature Dependent NMR Deuteron Quadrupole Coupling Constants for Two Types of Hydrogen Bonds Far below the Glass Transition.

We measured the deuteron quadrupole coupling constants (DQCCs) for hydroxy-functionalized ionic liquids (ILs) with varying alkyl chain length over the temperature range between 60 and 200 K by means of solid-state NMR spectroscopy. For all temperatures, the 2H spectra show two DQCCs representing different types of hydrogen bonds. Higher values, ranging from 220 to 250 kHz, indicate weaker hydrogen bonds between cation and anion (c-a), and lower values varying from 165 to 210 kHz result from stronger hydrogen bonds between the OD groups of cations (c-c), in agreement with recent observations in infrared, neutron diffraction, and NMR studies. We observed different temperature dependencies for (c-a) and (c-c) hydrogen bonding. From the static pattern of the 2H spectra at the lowest temperatures, we derived the true DQCCs being up to 20 kHz larger than recently reported values measured at the glass transition temperature. We were able to freeze the librational motions of the hydrogen bonds in the ILs. The temperature dependence of the (c-a) and (c-c) cluster populations in the glassy state is opposite to that observed in the liquid state, partly anticipating the behavior of ILs tending to crystallize.

Molecular dynamics simulations study of the structure and dynamics of nimodipine confined in an ordered mesoporous silica matrix

The structural and dynamical properties of nimodipine (a drug from the family of derivatives of 1,4-dihydropyridine) confined in silica matrix were studied by means of molecular dynamics simulations as a function of pore filling. Nimodipine molecules are connected with the silica surface via different types of hydrogen bonds, which have different average lifetimes (from 20 to 80 ps). The interaction with the silica surface inhibits the translational diffusion, while for molecules situated in the center of the channel translational diffusion is clearly observed, even if slow. The silica surface and the presence of additional layers of molecules in the pore also influence significantly the internal mobility, as determined by the reorientation of the methyl groups and the molecular chains. As the different degree of pore filling cannot be easily explored experimentally, molecular dynamics simulations gave unique access to the analysis of how the structure and dynamics of confined nimodipine depend on this parameter.

Identification of normal modes responsible for ferroelectric properties in organic ferroelectric CBDC

Structure and dynamics of hydrogen bonded organic ferroelectric CBDC (1-cyclobutene-1,2-dicarboxylic acid, C6H8O4) have been investigated using inelastic neutron scattering (INS) spectroscopy and first principles lattice dynamics. Vibrational modes of O–H–O bending, related with two different types of hydrogen bonds, inter and intra-molecular, are manifested as two sets of doublets in the range of 900–1400 cm−1 in the INS spectrum. First principles density functional theory (DFT) is used to assign these doublets to out-of-the-plane and in-plane vibrations of these two types of O–H—O bending modes. Correlating structure and dynamics we find that although the local structures of the hydrogen bonded protons are similar, their medium range order may influence their vibrational frequencies. Vibrational modes of non-hydrogen bonded protons also are assigned separately in the spectrum. Comparing the calculated and the experimental INS spectra it is predicted that hydrogen bonded O–H bonds are more anharmonic than non-hydrogen bonded C–H bonds. From the calculated Born effective charge tensor it is predicted that inter-molecular hydrogen bonds contribute more to the ferroelectric polarisation of CBDC than intra-molecular ones. A large LO-TO splitting of the O–H stretching mode at 2471 cm−1 is identified with the mode that has significant contribution to the ferroelectric polarisation. As this mode is sensitive to long range Coulomb interactions and is responsible for ferroelectric properties of the material, vibrational spectroscopy combined with DFT calculations is proposed as a characterisation tool to investigate ferroelectric properties in the CBDC molecular crystal.

Density functional theory, spectroscopic and hydrogen bonding analysis of fenoxycarb–water complexes

Abstract The spectroscopic properties of Fenoxycarb (FC) and its water complexes were studied by adopting experimental and computational methods. The optimized geometrical parameters obtained from computational methods were compared with experimental studies. Density functional theory (DFT), Natural bond orbital analysis (NBO) is used to explain different types of hydrogen bonds in the molecule and its water complexes. The FT-IR and FT Raman spectra of FC were studied by vibrational energy distribution analysis (VEDA.4) using potential energy distribution (PED) analysis. Charge analysis explains the charge transfer within the molecule. Potential energy scan (PES) had been performed. The reactivity of the molecule using various descriptors such as Fukui function, local softness, electrophilicity, electronegativity, hardness, HOMO-LUMO energy gap were calculated and discussed. Intramolecular interactions were calculated by Hirshfeld surface analysis and fingerprint plots. The 1H, 13C NMR spectra were recorded and analysed. UV visible spectrum of the compound was recorded for the acetone solvent and electronic properties were computed by time dependent (TD-DFT) level with CAM B3LYP approach. FC was screened for its insecticidal activity. Molecular docking studies were conducted to predict its insecticidal activity.