Blue-shifting Hydrogen Research Articles

Interactions between Paracetamol and Formaldehyde: Theoretical Investigation and Topological Analysis.

In this work, noncovalent interactions including hydrogen bonds, C···C, N···O, and van der Waals forces between paracetamol and formaldehyde were investigated using the second-order perturbation theory MP2 in conjunction with the correlation consistent basis sets (aug-cc-pVDZ and aug-cc-pVTZ). Two molecular conformations of paracetamol were considered. Seven equilibrium geometries of dimers were found from the result of the interactions with formaldehyde for each conformation of paracetamol. Interaction energies of complexes with both ZPE and BSSE corrections range from -7.0 to -21.7 kJ mol-1. Topological parameters (such as electron density, its Laplacian, and local electron energy density at the bond critical points) of the bonds from atoms in molecules theory were analyzed in detail. The natural bond orbital analysis showed that the stability of complexes was controlled by noncovalent interactions including O-H···O, N-H···O, C-H···O, C-H···N, C-H···H-C, C···C, and N···O. The red- and blue-shifted hydrogen bonds could both be observed in these complexes. The properties of these interactions were also further examined in water using a polarized continuum model. In water, the stability of the complex was slightly reduced as compared to that in the gas phase.

A Study on Structure, Stability, Cooperativity and Hydrogen Bond in the Complexes of nHCHO and nH2O (n=1-3) by Quantum Chemical Method

Eight stable structures of nHCHO∙∙∙nH2O (n=1-3) were observed on potential surface energy at the MP2/aug-cc-pVDZ level of theory. All complexes were mainly stabilized by O-H∙∙∙O hydrogen bond and an additional contribution of Csp2-H∙∙∙O one. The larger positive cooperativity when adding H2O as compared to HCHO molecule is the most important factor in complex stabilization. The obtained results show that the O-H∙∙∙O is red-shifting hydrogen bond while Csp2-H∙∙∙O belongs to blue-shifting hydrogen bond. It is remarkable that an addition of H2O/HCHO into the binary system leads a Csp2-H bond contraction and an increase of its stretching frequency in Csp2-H∙∙∙O hydrogen bond, in which the larger marnitude of its blue-shifting enhancement is found as adding H2O molecule. This result is mainly governed by a decrease of electron density at σ*(Csp2-H) orbital and an increase in the s-character percentage of the Csp2 (Csp2-H).

Probable detection of an eruptive filament from a superflare on a solar-type star

Solar flares are often accompanied by filament/prominence eruptions (~104 K and ~1010−11 cm−3), sometimes leading to coronal mass ejections that directly affect the Earth’s environment1,2. ‘Superflares’ are found on some active solar-type (G-type main-sequence) stars3–5, but the filament eruption–coronal mass ejection association has not been established. Here we show that our optical spectroscopic observation of the young solar-type star EK Draconis reveals evidence for a stellar filament eruption associated with a superflare. This superflare emitted a radiated energy of 2.0 × 1033 erg, and a blueshifted hydrogen absorption component with a high velocity of −510 km s−1 was observed shortly afterwards. The temporal changes in the spectra strongly resemble those of solar filament eruptions. Comparing this eruption with solar filament eruptions in terms of the length scale and velocity strongly suggests that a stellar coronal mass ejection occurred. The erupted filament mass of 1.1 × 1018 g is ten times larger than those of the largest solar coronal mass ejections. The massive filament eruption and an associated coronal mass ejection provide the opportunity to evaluate how they affect the environment of young exoplanets/the young Earth6 and stellar mass/angular momentum evolution7.

Molecular insertion regulates the donor-acceptor interactions in cocrystals for the design of piezochromic luminescent materials

Developing a universal strategy to design piezochromic luminescent materials with desirable properties remains challenging. Here, we report that insertion of a non-emissive molecule into a donor (perylene) and acceptor (1,2,4,5-tetracyanobezene) binary cocrystal can realize fine manipulation of intermolecular interactions between perylene and 1,2,4,5-tetracyanobezene (TCNB) for desirable piezochromic luminescent properties. A continuous pressure-induced emission enhancement up to 3 GPa and a blue shift from 655 to 619 nm have been observed in perylene-TCNB cocrystals upon THF insertion, in contrast to the red-shifted and quenched emission observed when compressing perylene-TCNB cocrystals and other cocrystals reported earlier. By combining experiment with theory, it is further revealed that the inserted non-emissive THF forms blue-shifting hydrogen bonds with neighboring TCNB molecules and promote a conformation change of perylene molecules upon compression, causing the blue-shifted and enhanced emission. This strategy remains valid when inserting other molecules as non-emissive component into perylene-TCNB cocrystals for abnormal piezochromic luminescent behaviors.

From Intermolecular Interaction Energies and Observable Shifts to Component Contributions and Back Again: A Tale of Variational Energy Decomposition Analysis

Quantum chemistry in the form of density functional theory (DFT) calculations is a powerful numerical experiment for predicting intermolecular interaction energies. However, no chemical insight is gained in this way beyond predictions of observables. Energy decomposition analysis (EDA) can quantitatively bridge this gap by providing values for the chemical drivers of the interactions, such as permanent electrostatics, Pauli repulsion, dispersion, and charge transfer. These energetic contributions are identified by performing DFT calculations with constraints that disable components of the interaction. This review describes the second-generation version of the absolutely localized molecular orbital EDA (ALMO-EDA-II). The effects of different physical contributions on changes in observables such as structure and vibrational frequencies upon complex formation are characterized via the adiabatic EDA. Example applications include red- versus blue-shifting hydrogen bonds; the bonding and frequency shifts of CO, N2, and BF bound to a [Ru(II)(NH3)5]2 + moiety; and the nature of the strongly bound complexes between pyridine and the benzene and naphthalene radical cations. Additionally, the use of ALMO-EDA-II to benchmark and guide the development of advanced force fields for molecular simulation is illustrated with the recent, very promising, MB-UCB potential. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

An ab initio study of some hydrogen-bonded complexes of chloroform and bromoform: red-shifted or blue-shifted hydrogen bonds?

The properties of the hydrogen-bonded complexes of chloroform and bromoform with ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride were studied by means of ab initio calculations. The properties of interest were the molecular structures, the interaction energies, the vibrational spectra and the nature of the orbital interactions involved in the formation of the complexes. Of particular interest was the determination of whether the various interactions exhibited red-shifted or blue-shifted hydrogen bond behaviour. The complexes optimized in three distinct structural models, singly bonded, cyclic and cage. The interaction energies, in the main, varied systematically with changes of the haloform and of the partner molecules. Changes of the CH or YH (Y = N, O, F, P, S and Cl) bond lengths correlated in most cases with the interaction energies, subject to some inconsistencies, with opposite behaviour being shown by the two sets. Similarly, the CH and YH stretching wavenumber shifts also displayed a dependence on the interaction energies, tracking with the bond length changes. Based on the diagnostic utility of these structural and spectroscopic properties, the complexes were found to be almost exclusively red-shifted, for binding through both the CH and YH groups. The orbital interactions responsible for the stability of the complexes were determined to be donation from a Y atom lone pair orbital of the partner molecule to a CH σ antibonding orbital and from a X lone pair orbital (X = Cl and Br) of the haloform to a YH σ antibonding orbital.

Blue-Shift Hydrogen Bonds in Silyltriptycene Derivatives: Antibonding σ* Orbitals of the Si-C Bond as Effective Acceptors of Electron Density.

Triptycene derivatives are widely utilized in different fields of chemistry and materials sciences. Their physicochemical properties, often of pivotal importance for the rational design of triptycene-based functional materials, are influenced by noncovalent interactions between substituents mounted on the triptycene skeleton. Herein, a unique interaction between electron-rich substituents in the peri position and the silyl group located on the bridgehead sp3 -carbon is discussed on the example of 1,4-dichloro-9-(p-methoxyphenyl)-silyltriptycene (TRPCl) which exists in solution in the form of two rotamers differing by dispositions, syn or anti, of the Si-CPh (the CPh atom is from the p-methoxyphenyl group) bond against the peri-Cl atom. For the first time, substantial differences between the Si-CPh bonds in these two dispositions are identified, based on indirect experimental and direct theoretical evidence. For these two orientations, the experimental 1 J(Si,CPh ) values differ by as much as 10 percent. The differences are explained in terms of effective electron density transfer from the peri-Cl atom to the antibonding σ* orbitals of the Si-X bonds (X=H, CPh ) oriented anti to that atom. The electronic effects are revealed by an NBO analysis. Connections of these observations with the notion of blue-shifting hydrogen bonds are discussed.

Comprehensive study on the topological properties of 5-Amino-2-Methyl Benzene Sulfonamide involving inter and intra molecular hydrogen bonds

Abstract Density functional calculations with Becke’s three parameter hybrid method using the correlation functional of Lee, Yang and Parr were carried out for the molecule 5-Amino-2-Methyl Benzene Sulfonamide with 6-311G++(d,p) basis set. Attention has been paid to explain one of the most fascinating observation of C–H⋯O and C–H⋯N intra molecular hydrogen bonds. Effect of C–H⋯O hydrogen bond interactions on the C–H bond length was analyzed. The network of inter and intra molecular hydrogen bonds was systematically investigated. Bader’s AIM theory was used to perform the topological study of electron density. Criteria for hydrogen bonding are comprehensively reviewed for each hydrogen bond revealed, and the concept of improper blue shift hydrogen bonding is addressed.

DMSO hydration redefined: Unraveling the hydrophobic hydration of solutes with a mixed hydrophilic–hydrophobic characteristic

Hydrophobic hydration of solutes with a mixed hydrophilic–hydrophobic characteristics is still poorly understood. This is because both experimental and theoretical methods find it difficult to see the ice-like water structure around the nonpolar solute groups, unlike hydrogen bonds with the hydrophilic groups. In order to unravel this problem, we have investigated DMSO hydration by means of infrared spectroscopy and theoretical methods, namely DFT, ONIOM calculations and AIMD simulations, which allowed us to redefine its hydration. In dilute DMSO solutions the clathrate-like water is formed around the DMSO molecule, supported by interactions of water molecules with the methyl hydrogens (the blue-shifted hydrogen bonds). The cage is constructed by water molecules that form hydrogen bonds of the comparable energy and length with the SO group and between water molecules. When the construction of the cage is completed, DMSO molecule partially regains its rotational freedom inside. Strong hydrogen bonds within the frame are masked by the relatively small population of weakened hydrogen bonds of water molecules in the vicinity of the SO group, due to the improper fit to the bulk water of water molecules hydrogen bonded to the oxygen atom of DMSO. We also propose a new explanation of the highly non-ideal mixing behavior of aqueous DMSO solutions at the eutectic point, as the positive excess entropy of the equimolar amounts of molecular complexes distinguished in the system.

Single-walled carbon nanotubes in tetrahydrofuran solution: microsolvation from first-principles calculations

The molecular interactions between the commonly used solvent tetrahydrofuran (THF) and single-walled carbon nanotubes (SWCNT) are studied using density functional theory calculations and Car–Parrinello molecular dynamics simulations. The competitive interplay between THF–THF and THF–SWCNT interactions via C-H⋯O and C-H⋯π hydrogen bonds is analyzed in detail. The binding energies for different global and local energy minima configurations of THF monomers, dimers, trimers, and tetramers on SWCNT(10,0) were determined. The adsorbed species are analyzed in terms of their coordination to the surface via weak hydrogen bonds of the C-H⋯π type and in terms of their ability to form intermolecular C-H⋯O hydrogen bonds, which are responsible for the self-aggregation of THF molecules and a possible dimerization or tetramerization process. A special focus is put on the pseudorotation of the THF molecules at finite temperatures and on the formation of blue-shifting hydrogen bonds.

Probing Blue-Shifting Hydrogen Bonds with Adiabatic Energy Decomposition Analysis.

The physical origin of blue-shifting hydrogen bonds remains a subject of debate, although many plausible explanations have been proposed. Using a molecular property decomposition analysis based on absolutely localized molecular orbitals, we investigated several representative F3CH···Y (Y = H2O, NH3, Cl-) complexes. We reveal that features of a blue-shifting H-bond already appear on the frozen surface where both polarization and charge transfer (CT) are "turned off", and that the final frequency shift observed depends on the strength of CT. Further decomposition of forces at the frozen level shows that Pauli repulsion is the only component that shortens the C-H bond in the short-range, while both permanent electrostatics and dispersion lengthen the bond. The effects of these forces from the medium to long-range are also discussed. Our analysis provides a complete picture for blue-shifting H-bonds and suggests two necessary conditions for their features to be observed at equilibrium structures: (i) stronger Pauli repulsion than the combination of electrostatic and dispersion forces; (ii) relatively weak CT that is insufficient to compensate for the blue-shifting effect of the frozen interaction.

On the interaction of propynal with HNO, HF, HCl, H2O, CH3OH, and NH3: Red- and blue-shifting hydrogen bonds and tetrel bonds

The potential energy surfaces of the complexes of propynal, (propiolaldehyde, propargyl aldehyde, HCCCOH), with a series of small molecules (HNO, HF, HCl, H2O, CH3OH, and NH3) have been investigated theoretically at the MP2 and CCSD(T) levels using several extended basis sets. Thirty low-lying minima have been detected, eight for HCCCOH-HNO, four for each of the dimers HCCCOH-HF, HCCCOH-HCl, and HCCCOH-H2O, seven for the HCCCOH-CH3OH complex, and three for HCCCOH-NH3. The most stable HCCCOH-HNO complex has a non-planar, orthogonal structure with a tetrel bond and a hydrogen bond. In most cases the calculated intramolecular bond length changes as induced by complex formation are allegeable on the basis of the intramolecular harmonic force fields of propynal and the partner molecules. The vibrational frequency shifts, typical for formyl groups engaged in hydrogen bonding, red shifts of CO stretches and blue shifts of CH stretches, occur in most of the dimers, whereas the acetylenic CH and CC stretches are red-shifted when this CH bond is involved in hydrogen bonding. In almost all HCCCOH-HNO complexes, the NH stretching frequency is also blue-shifted. However, in case of the most stable HCCCOH-HNO complex a red-shift of the harmonic NH stretch is calculated. Inclusion of anharmonic contributions reduces this red shift substantially and even converts it to a blue shift. Conventional red shifts of X-H (X = F, Cl, O) stretching frequencies and blue shifts for formyl CH stretches are calculated for most of the complexes with HF, HCl, H2O, CH3OH, and NH3.

Proton acceptor response in hydrogen-bonded XH…WZ (X = F, Cl, Br, FAr, FKr, NC, FCC; WZ = CO, FH, N2) complexes

Abstract An MP2/6-311++G(3df,3pd) computational study of the model complexes XH…WZ (X = F, Cl, Br, FAr, FKr, NC, FCC; WZ = CO, FH, N2), which involve both red- and blue-shifting hydrogen bonds, was undertaken. The response of the hydrogen bond acceptors WZ, as gauged from their bond length change and the frequency shifts of their stretching modes, was investigated. The W-Z bond length change (extension or compression) depends on the sign of the WZ dipole moment derivative with respect to bond extension. The hydrogen bond strength and the WZ bond length change/frequency shift were found to be strongly correlated.

Type IIn SN 2010jl: probing dusty line-emitting shell

I explore signatures of a possible dust formation in the late SN~2010jl that could be imprinted in the line blueshift and the radius evolution of the dusty infrared-emitting shell. I propose a simple model that permits one to reproduce emission lines of blueshifted hydrogen and helium emission lines. The model suggests that the hydrogen emission originates primarily from shocked fragmented circumstellar clumps partially obscured by the absorbing cool dense shell and by unshocked ejecta. In the He I 1.083 $\mu$m line on day 178 this component is significantly weaker compared to broad component from unshocked ejecta that is obscured by the absorprion produced by ejecta itself. Simulations of late time ($t > 400$ d) H$\alpha$ suggest that, apart from the dust in the cool dense shell, a significant amount of dust must form in the unshocked supernova ejecta. The supernova radius predicted by the interaction model coincides with the radius of the dusty shell recovered from late time (> 460 days) infrared data, which strongly support that infrared radiation indeed originates from supernova. The ejecta dust is presumably locked in opaque blobs.

Characterization of blue-shifting hydrogen bonds in small complexes

ABSTRACTThe so-called improper blue-shifting (BS) Hydrogen bond, characterising some small complexes, is theoretically investigated by first-principles calculations based on the Density Functional Theory. We compute structural, energetic, electronic and electrostatic properties not only of complexes with linear Hydrogen bonds but also of systems with multiple intermolecular contacts leading to the formation of ‘bifurcated’ or even ‘trifurcated’ Hydrogen bonds. In particular, Hydrogen bonds are characterised in terms of differential electron densities distributions and profiles, and of the shifts of the centres of Maximally localised Wannier Functions. The information from the latter quantities can be conveyed into simple geometric bonding parameters that are helpful in characterising the interatomic bonds. The effect of including dispersion corrections for describing BS Hydrogen bonds is also investigated. Our detailed comparison of the properties of systems with BS Hydrogen bonds to those of others, where more conventional red-shifting Hydrogen bonds are formed, supports the view that there is no fundamental difference between the two kinds of bonds.

An ab initio study of some binary complexes containing methyl fluoride and difluoromethane: red-shifting and blue-shifting hydrogen bonds

ABSTRACTThe properties of a number of hydrogen-bonded complexes of methyl fluoride and difluoromethane with a range of hydrides of the first two rows of the periodic table have been computed using ab initio molecular orbital theory. The aim of this work was to identify possible examples of blue-shifting hydrogen-bonded species analogous to those formed between fluoroform and ammonia, water, phosphine and hydrogen sulphide, reported earlier. The calculations were carried out using the Gaussian-09 program, at the second-order level of Møller–Plesset perturbation theory, and with the aug-cc-pVTZ basis sets of Dunning. The properties studied include the molecular structures, the hydrogen bond energies and the vibrational spectra. The results have been interpreted with the aid of natural bond orbital theory and the quantum theory of atoms in molecules.

Computational study of red- and blue-shifted C[sbnd]H⋯Se hydrogen bond in Q3C[sbnd]H⋯SeH2 (Q = Cl, F, H) complexes

This work presents CH⋯Se hydrogen bonding interaction at the MP2 level of theory. The system Q3CH⋯SeH2 (Q = Cl, F, and H) provides an opportunity to investigate red- and blue-shifted hydrogen bonds. The origin of the red- and blue-shift in CH stretching frequency has been investigated using Natural Bond Orbital analysis. A large amount of electron density is being transferred to the σ∗CH orbital in red-shifted Cl3CH⋯SeH2. Electron density transfer in the blue-shifted F3CH⋯SeH2 is primarily to the remote fluorine atoms. Further, due to polarization of the CH bond, the contradicting effects of rehybridization and hyperconjugation are important. The extent of hyperconjugation reigns predominant in explaining the nature of the CH⋯Se hydrogen bond in Q3CH⋯SeH2 complexes as the hydrogen bond acceptor remain same in this investigation. Red- and blue-shift in Q3CH⋯SeH2 (Q = Cl and F) complexes is best described by pro-improper hydrogen bond donor concept.

Effect of electron-donating and electron-withdrawing atoms on the C–H…Y hydrogen bond in model X3CH…YZ (X = B, F; YZ = BF, CO, N2) complexes

ABSTRACTA computational study of model complexes X3CH…YZ (X = B, F; YZ = BF, CO, N2) was undertaken to assess the effect of electron-donating and electron-withdrawing X atoms on the properties of the C–H…Y hydrogen bond. Sequential substitution of the B atoms in B3CH by F atoms to produce F3CH allowed for the elucidation of interesting trends in the corresponding hydrogen-bonded complexes. The dipole moments and the dipole moment derivative with respect to C–H bond displacement for the proton donors and the chemical hardness of the Y atom of the proton acceptor YZ were found to be useful parameters for understanding these trends. It was found that a positive dipole derivative favours red-shifted hydrogen bonds, whereas a negative dipole derivative favours blue-shifted hydrogen bonds. However, decreasing hardness of Y (which correlates with increasing intermolecular attraction) modifies the interaction such that either greater C–H bond extensions/red shifts or smaller C–H bond compressions/blue shifts are obtained.

Exploring fundamental differences between red- and blue-shifted intramolecular hydrogen bonds using FAMSEC, FALDI, IQA and QTAIM

We have discovered, using developed by us recently FALDI and FAMSEC computational techniques, fundamentally distinct mechanisms of intramolecular red- and blue-shifted H-bond formation that occurred in different conformers of the same molecule (amino-acid β-alanine) involving the same heteroatoms (O–H⋅⋅⋅N and N–H⋅⋅⋅O). Quantitative topological, geometric and energetic data of both H-bonds obtained with well-known QTAIM and IQA methodologies agree with what is known regarding H-bonding in general. However, the FALDI charge and decomposition scheme for calculating in real space 3D conformational deformation densities provided clear evidence that the process of electron density redistribution taking place on the formation of the stronger red-shifted H-bond is fundamentally distinct from the weaker blue-shifted H-bond. Contributions made by atoms of the X–H⋅⋅⋅Y–Z fragment (IUPAC notation) as well as distinct atoms on the H-bond formation were fully explored. The FAMSEC energy decomposition approach showed that the atoms involved in formation of the red-shifted H-bond interact in a fundamentally different fashion, both locally and with the remainder of the molecule, as compared with those of the blue-shifted H-bond. Excellent correlations of trends obtained with QTAIM, IQA, FAMSEC and FALDI techniques were obtained. Commentary regarding IUPAC recommended definition of an H-bond and validity of observed AILs (or bond paths) of the two H-bond kinds is also discussed.

Solvation power of HFIP for the hydrophilic and the hydrophobic moieties of l-leucine studied by MD, IR, and NMR techniques

Abstract The solvation properties of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) in its aqueous binary solvents have been evaluated using l -leucine (Leu) as a probe molecule by both theoretical and experimental approaches. Thus, molecular dynamics (MD) simulations, infrared (IR) and 1 H and 13 C NMR spectroscopic experiments have been conducted on Leu-HFIP-water solutions with varying the HFIP mole fraction from x HFIP = 0 to 1. Spatial distribution functions (SDFs) obtained from the MD simulations showed that the Leu carboxylate group is gradually solvated by HFIP molecules with increasing x HFIP , instead of water molecules. Thus, the replacement of water by HFIP for the carboxylate group progresses as the x HFIP rises. This was proved by the C O stretching vibrations and the 13 C chemical shift of the carboxylate group. On the contrary, the Leu aminium group is preferentially solvated by water below x HFIP = 0.7. However, HFIP molecules begin to solvate the aminium group above this mole fraction. The trifluoromethyl groups of HFIP significantly enclose the alkyl group of Leu even at the low x HFIP . By surrounding the Leu alkyl group with the HFIP trifluoromethyl groups, the C H stretching vibrations of Leu blueshift with increasing x HFIP . Simultaneously, the hydrogen and carbon atoms of the Leu alkyl group are electronically shielded as the x HFIP rises. The MD pair correlation function g ( r ) HCLeu-FHFIP showed the H F interactions between the Leu alkyl hydrogen and the HFIP fluorine atoms with the distance of 2.75 A. Consequently, the present results proved that the HFIP trifluoromethyl groups may interact with the Leu alkyl group through the blueshift hydrogen bonds of C H ⋯ F C.