OH Bond Length Research Articles

Correlations between the Structures and Spectra of Protonated Water Clusters.

Badger's rule-like correlations between OH stretching frequencies and intensities and the OH bond length are used to develop a spectral mapping procedure for studies of pure and protonated water clusters. This approach utilizes the vibrationally averaged OH bond lengths, which were obtained from diffusion Monte Carlo simulations that were performed using the general potential developed by Yu and Bowman. Good agreement is achieved between the spectra obtained using this approach and previously reported spectra for H+(H2O)n clusters, with n = 3, 4, and 5, as well as their perdeuterated analogues. The analysis of the spectra obtained by this spectral mapping approach supports previous work that assigned the spectrum of H+(H2O)6 to a mixture of Eigen and Zundel-like structures. Analysis of the calculated spectra also suggests a reassignment of the frequency of one of the transitions that involves the OH stretching vibration of the OH bonds in the hydronium core in the Eigen-like structure of H+(H2O)6 from 1917 cm-1 to roughly 2100 cm-1. For D+(D2O)6, comparison of the measured spectrum to those obtained by using the spectral mapping approach suggests that the carrier of the measured spectrum is one or more of the isomers of D+(D2O)6 that contain a four-membered ring and two flanking water molecules. While there are several candidate structures, the two flanking water molecules most likely form a chain that is bound to the hydronium core.

Nitriding-reduction fabrication of coralloid CoN/Ni/NiO for efficient electrocatalytic overall water splitting

The introduction of nitride in Ni/NiO-based catalytic system for electrocatalystic water splitting via a skillful strategy remains a great challenge. Herein, we proposed a one-step urea nitriding-reduction strategy for the fabrication of novel CoN/Ni/NiO electrocatalyst on carbon cloth (CC). The combination of CoN and Ni/NiO could construct CoN/Ni interface and expose more active sites, thus exhibiting excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline media. Consequently, CoN/Ni/NiO catalyst exhibited remarkable HER/OER performance with an overpotential of 92 mV/114 mV at 10 mA cm−2 in 1.0 M KOH, along with a low cell voltage of 1.56 V to enhance overall water splitting. In addition, when CoN was introduced in Ni/NiO system, CoN/Ni/NiO displayed high conductivity, large active surface areas, high Faradic efficiency (FE) and remarkable stability. Density functional theory (DFT) calculations demonstrated that CoN/Ni/NiO possessed a decreased d-band center beneficial for optimizing the energy barrier of intermediates. Specifically, the ΔGH2O (0.088 eV) and ΔGH* (0.18 eV) in HER and the ΔGOOH* (1.4 eV) of rate determining step (O*→OOH*) in OER of CoN/Ni/NiO catalyst were optimized to achieve high water splitting activity. Simultaneously, for adsorbed H2O on CoN/Ni/NiO, the OH bond length extended from 0.975 to 1.110 Å, and the bond angle enlarged from 104.271 to 109.471°, thereby directly demonstrating the excellent HER/OER performance of CoN/Ni/NiO.

Exploring the change of hydrogen bond evolution in NMP-H2O solution through 2D Raman-COS spectra analysis

The transitions of Hydrogen Bond (HB) structure with in the cluster structures of NMP-H2O solutions was conducted by combining Density Functional Theory (DFT) calculations and Two-dimensional Correlation Raman Spectroscopy (2D Raman-COS). When VNMP < 20 %, NMP molecule is incorporated into the tetrahedral structure of water through an "insertion" mechanism, by displacing some H2O molecules and establishing HB. This interaction strengthens the tetrahedral arrangement in water, causing the free OH bond length to be compressed. When VNMP > 20 %, large amounts of NMP molecules were self-assembled through dipole-dipole alignment, and the NMP·2H2O, NMP·H2O, and 2NMP·H2O clusters gradually substitute the tetrahedral structure of water, leading to the disruption of the HB network in water. Furthermore, it was observed that the pulsed laser beam accelerated the transition point of the HB structure in the NMP-H2O solution. This research provides references for the application of NMP in the fields of aqueous batteries from the view of HB with electrolyte.

Exploring the Origins of the Intensity of the OH Stretch-HOH Bend Combination Band in Water.

While the intensity of the OH stretching fundamental transition is strongly correlated to hydrogen-bond strength, the intensity of the corresponding transition to the state with one quantum of excitation in both the OH stretching and HOH bending vibrations in the same water molecule shows a much weaker sensitivity to the hydrogen-bonding environment. The origins of this difference are explored through analyses of the contributions of terms in the expansion of the dipole moment to the calculated intensity. It is found that the leading contribution to the stretch-bend intensity involves the second derivative of the dipole moment with respect to the OH bond length and HOH angle. While this is not surprising, the insensitivity of this derivative to the hydrogen-bonding environment is unexpected. Possible contributions of mode mixing are also explored. While mode mixing leads to splittings of the energies of nearly degenerate excited states, it does not result in significant changes in the sum of the intensities of these transitions. Analysis of changes in the partial charges on the hydrogen atoms upon displacement of the HOH angles shows that these charges generally increase with increasing HOH angle. This effect is partially canceled by a decrease in the charge of the hydrogen atom when a hydrogen bond is broken. The extent of this cancellation increases with the hydrogen bond strength, which is reflected in the observed insensitivity of the intensity of the stretch-bend transition to hydrogen-bond strength.

Biocompatible AlOOH-based memristor with biomimicking synaptic functions for artificial nociceptor applications

Electronic devices with biomimetic synaptic characteristics are one of the most critical components in health monitoring and artificial intelligence. The design of neuromorphic responsive devices, however, yet remains a ground challenge. Herein, a biocompatible and electrically responsive boehmite material (γ-AlOOH) is utilized to fabricate artificial memristors to realize mimicking biological synapsefunctions. The obtained AlOOH memristor is flexible, highly transparent, and biocompatible, exhibiting nonvolatile resistive switching behaviours with low threshold voltages, high ON-OFF ratios (>103), good switching durability (>104 cycles), and long retention time (>104 s). Specifically, the device can mimic the biosynaptic functions, such as paired-pulse facilitation (PPF), long-term potentiation/depression (LTP/LTD), amplitude-dependent plasticity (SADP), and spike time dependent plasticity (STDP), and the typical sensitization, desensitization, hyperalgesia, and allodynia behaviours of the biological nociceptors. This study reveals that the AlOOH memristor with excellent artificial synapses is resulted by the high proton mobility along with the OH bond length variation of AlOOH subjected to applied stimuli, such as voltages, pulse width, and pulse intervals. Therefore, the biocompatible AlOOH-based memristors with artificial synapse behaviour have promising potential for the applications in high-performance neuromorphic devices and future artificial intelligence.

Spectroscopic Signatures of Internal Hydrogen Bonds of Brønsted‐Acid Sites in the Zeolite H‐MFI

AbstractThe location of Brønsted‐acid sites (bridging OH groups, b‐OH) at different crystallographic positions of zeolite catalysts influences their reactivity due to varying confinement. Selecting the most stable b‐OH conformers at each of the 12 T‐sites (T=Si/Al) of H‐MFI, a representative set of 26 conformers is obtained which includes free b‐OH groups pointing into the empty pore space and b‐OH groups forming H‐bonds across five‐ or six‐membered rings of TO4 tetrahedra. Chemically accurate coupled‐cluster‐quality calculations for periodic models show that the strength of internal H‐bonds and, hence, the OH bond length vary substantially with the framework position. For 11 of the 19 H‐bonded b‐OH groups examined, our predictions fall into the full width at half maximum range of the experimental signals at 3250±175 cm−1 and 7.0±1.4 ppm which supports previously debated assignments of these signals to H‐bonded b‐OH sites.

Spectroscopic Signatures of Internal Hydrogen Bonds of Brønsted-Acid Sites in the Zeolite H-MFI.

The location of Brønsted-acid sites (bridging OH groups, b-OH) at different crystallographic positions of zeolite catalysts influences their reactivity due to varying confinement. Selecting the most stable b-OH conformers at each of the 12 T-sites (T=Si/Al) of H-MFI, a representative set of 26 conformers is obtained which includes free b-OH groups pointing into the empty pore space and b-OH groups forming H-bonds across five- or six-membered rings of TO4 tetrahedra. Chemically accurate coupled-cluster-quality calculations for periodic models show that the strength of internal H-bonds and, hence, the OH bond length vary substantially with the framework position. For 11 of the 19 H-bonded b-OH groups examined, our predictions fall into the full width at half maximum range of the experimental signals at 3250±175 cm-1 and 7.0±1.4 ppm which supports previously debated assignments of these signals to H-bonded b-OH sites.

Quantum‐Chemical Insight into Self‐Organization of Complex Molecules from Acetylene and Anilines Catalyzed by Superbase KOH/DMSO: One‐Pot Cascade Assembly of 1,3‐Bis(arylamines)

AbstractThe self‐organization of functionalized diamines, 1‐acetyl‐1,3‐bis(haloarylamines), from three molecules of acetylene and two molecules of haloanilines in the KOH/DMSO superbase medium, has been analyzed quantum chemically in some detail in the framework of the B2PLYP(D3)/6‐311+G**//B3LYP/6‐31+G* approach. We have established that the diamines are constructed in a cascade manner via the sequential alternating additions of haloaniline anions to acetylene. The reaction sequence is catalyzed by a superbase pentacoordinated complex, KOH ⋅ 5DMSO, where the hydroxide ion is significantly separated from the potassium cation (the K−OH bond length is by 0.4–0.5 Å longer than in the bare KOH molecule). The latter imparts pronounced superbasicity to the complex and provides for a shuttle‐like proton transfer (H++OH−=H2O) during the whole cascade process.

Real-time equation-of-motion CC cumulant and CC Green's function simulations of photoemission spectra of water and water dimer.

Newly developed coupled-cluster (CC) methods enable simulations of ionization potentials and spectral functions of molecular systems in a wide range of energy scales ranging from core-binding to valence. This paper discusses the results obtained with the real-time equation-of-motion CC cumulant (RT-EOM-CC) approach and CC Green's function (CCGF) approaches in applications to the water and water dimer molecules. We compare the ionization potentials obtained with these methods for the valence region with the results obtained with the coupled-cluster with singles, doubles, and perturbative triples formulation as a difference of energies for N and N - 1 electron systems. All methods show good agreement with each other. They also agree well with the experiment with errors usually below 0.1eV for the ionization potentials. We also analyze unique features of the spectral functions, associated with the position of satellite peaks, obtained with the RT-EOM-CC and CCGF methods employing single and double excitations, as a function of the monomer OH bond length and the proton transfer coordinate in the dimer. Finally, we analyze the impact of the basis set effects on the quality of calculated ionization potentials and find that the basis set effects are less pronounced for the augmented-type sets.

Effect of electrical stimulation on red meat Neu5Gc content reduction: a combined experimental and DFT study

The hazardous substance Neu5Gc (N-glycolylneuraminic acid), which is rich in red meat, is related to chronic inflammation but is hard to eliminate. Here, electrical stimulation, as a food-friendly nonthermal processing technology, was applied to red meat samples to reduce the Neu5Gc content. To explore the Neu5Gc structure changes during this process, electronic structure parameters were evaluated, and AIM (atom in molecules) theory and DFT (density function theory) calculations were further used. The results showed that the content of Nue5Gc in red meat can be reduced by (74.24 ± 0.69)% at 120V for 50s, with little impact on the meat texture and color. Theoretical calculations indicated that the Neu5Gc molecule becomes very unstable under electrical stimulation by increasing the OH bond length, reactive activity, strength of intermolecular dipole forces and total energy through reducing the values of bond dissociation energy and strength of intramolecular hydrogen bonds. Overall, this research provides an economical method to effectively control red meat safety.

Theoretical OH stretching vibrations in dravite

Abstract. Density functional theory is used to investigate the vibrational stretching properties of OH groups in ideal and chemically disordered dravite models. Different schemes of cationic occupancy are considered, including the occurrence of vacancies at the X site and Mg–Al inversion between the Y and Z sites. The harmonic coupling between different OH groups is found to be smaller than 1 cm−1, indicating that the OH stretching dynamic in dravite can be described by considering a collection of nearly independent single OH oscillators. Their harmonic stretching frequency is linearly correlated with the corresponding OH bond length and most of the bands observed in the experimental vibrational spectra can be interpreted as consequences of the cationic occupancy of the sites coordinated to the OH group. The V(OH) and W(OH) stretching frequencies are affected by the Mg–Al inversion and by the presence of vacancies at the X site. In this last case, the frequencies depend on the isolated or more concentrated character of the X vacancy distribution along the c axis. Based on theoretical stretching frequencies, new interpretations are proposed for some of the bands experimentally observed in synthetic samples of dravite and magnesio-foitite.

Low-lying electronic states of ethanol investigated by theoretical and synchrotron radiation methods

We investigate the ethanol absorption spectrum in the range 5.64–10.78 eV (220–115 nm), by combining ab initio theoretical and experimental methods in order to provide the most accurate and up-to-date information about the electronic state spectroscopy of ethanol. In particular, absolute cross-section values are reported from high-resolution vacuum ultraviolet (VUV) photoabsorption measurements. The present VUV spectrum reveals several new features not previously reported in the literature, with particular reference to the Rydberg (ndσ, ndσ′ ← (3a′′/13a)), n ≥ 3 members of the Rydberg (ndπ′(a′) ← (3a′′/13a)) and n = 3 members of the Rydberg (npσ′ ← (10a′/12a)) transitions. The experimental absolute photoabsorption cross sections have subsequently been used to calculate the photolysis lifetime of ethanol in the Earth's atmosphere (0–50 km), showing that solar photolysis is expected to be a weak sink at altitudes lower than 40 km to ●OH radical reactions. Potential energy curves for the lowest-lying excited electronic states, as a function of the O–H and the C–OH coordinates, are also obtained employing the equation of motion coupled cluster single and doubles (EOM-CCSD) and time dependant density functional theory (TD-DFT) methods. These show clear dissociation character at inter-nuclear distances greater than 2.0 Å for the RO–H and 2.2 Å for the RC–OH bond lengths, indicating the rather complex multidimensional character of the potential energy surfaces involved.

Competitive nuclear quantum effect and H/D isotope effect on torsional motion of H2O2: An ab initio path integral molecular dynamics study

Ab initio path integral molecular dynamics (PIMD) simulations were performed to understand the nuclear quantum effect and thermal effect on the torsional motion of H2O2 (D2O2). A broad distribution of geometrical parameters (OH and OO bond lengths [ROH and ROO] and HOO bond angle [∠HOO]) was obtained in quantum ab initio PIMD simulations, rather than in classical MD simulations. However, a modest distribution around the trans-configuration TS (∠HOOH = 180°) was found in the quantum ab initio PIMD simulations of H2O2 at low temperatures. Thus, the nuclear quantum effect slightly enhanced the HOOH torsional motion at low temperatures. A series of simulations also revealed that the thermal effect enhanced the HOOH torsional motion. However, it was restrained by the primary nuclear quantum effect on the ROH in quantum simulations at high temperatures. Therefore, an interesting competitive nuclear quantum effect on the torsional motion of H2O2 was observed.

High accuracy ab initio potential energy surface for the H2O-H van der Waals dimer.

A representation of the three-dimensional potential energy surface (PES) of the H2O-H van der Waals dimer is presented. The H2O molecule is treated as a rigid body held at its experimentally determined equilibrium geometry, with the OH bond length set to 1.809 650 34 a0 and the HOH bond angle set to 1.824 044 93 radians. Ab initio calculations are carried out at the coupled-cluster single, double, and perturbative triple level, with scalar relativistic effects included using the second-order Douglas-Kroll-Hess approximation. The ab initio calculations employ the aug-cc-pVnZ-DK series of basis sets (n = D, T, Q), which are recontracted versions of the aug-cc-pVnZ basis sets that are appropriate for relativistic calculations. The counterpoise method is used to reduce the basis set superposition error; in addition, results obtained using the aug-cc-pVTZ-DK and aug-cc-pVQZ-DK basis sets were extrapolated to the complete basis set (CBS) limit. The PES is based on calculations carried out at 1054 symmetry-unique H2O-H geometries for which the distance R between the H-atom and the H2O center of mass ranges from R = 2.5-9.0 Å. The reproduction of the PES along the orientational degrees of freedom was performed using Lebedev quadrature and an expansion in spherical harmonics. The mean absolute error of the reproduced PES is <0.02cm-1 for R ≥ 3.0 Å and <0.21cm-1 for R between 2.5 and 3.0 Å. The global minimum for the CBS PES is a coplanar H2O-H geometry, with R = 3.41 Å, in which the angle formed between the H2O C2 symmetry axis and the H-atom is 122.25°; the CBS binding energy for this geometry is 61.297cm-1. In addition, by utilizing the symmetry of the H2O molecule, the spherical harmonic expansion was simplified with no loss in accuracy and a speedup of ∼1.8 was achieved. The reproduced PES can be used in future molecular dynamics simulations.

Structural, textural, and chemical controls on the OH stretching vibrations in serpentine-group minerals

Abstract. The OH stretching vibrational properties of eight serpentine samples from veins of the New Caledonian ophiolite have been investigated by Fourier-transform infrared spectroscopy (FTIR) in the mid-infrared and near-infrared ranges and by Raman spectroscopy. The samples were selected for their monophasic composition (Lz: lizardite; Ctl: chrysotile; and Atg: antigorite) making them representative of the three serpentine species. Comparison of fundamental and overtone spectra allowed us to interpret most of the observed bands and to propose consistent spectral decomposition in individual components. The OH stretching bands related to intrinsic vibrational properties of the minerals are distinguished from those associated with chemical substitutions in octahedral sites (mainly Fe and Ni for Mg substitutions). Observations made on the most symmetric Lz are consistent with previous interpretations and underline the effect of macroscopic parameters on OH stretching bands in the FTIR spectra. The major importance of the distribution of OH bond lengths in the broadening of the vibrational signals of the less symmetric and more distorted Atg is confirmed. The combination of the three spectroscopic methods makes it possible to unravel the occurrence of two different types of interlayer OH environments in Ctl nanotubes. One corresponds to the features observed at 3684 and 7171 cm−1 in the fundamental and overtone spectra, respectively, and is similar to the local OH environment observed in Lz. The other corresponds to broader signals observed at 3693 and 7200 cm−1 in the fundamental and overtone spectra, respectively. It reflects a distribution of OH bond lengths likely related to local structural misfits between adjacent layers in the tubular structure of Ctl.

Hydrogen-bond network distortion of water in the soft confinement of Nafion membrane.

A Compton spectroscopy investigation is carried out in hydrated Nafion membranes, enabling identification of distortions in the hydrogen-bond distribution of the polymer hydrating water by means of the subtle changes reflected by the Compton profiles. Indeed, deformations of the Compton profiles are observed when varying hydration, and two different bonding kinds are associated with the water molecules: at low hydration, water surrounds the sulfonic groups, while on increasing hydration, water molecules occupy the interstitial cavities formed upon swelling of the membrane. The analysis is proposed in terms of averaged OH bond length variation. A sizable contraction of the OH distance is observed at low hydration (∼0.09 Å), while at higher hydration levels, the contraction is smaller (∼0.02 Å) and the OH bond length is closer to bulk water. An evaluation of the electron kinetic energy indicates that the spatial changes associated with the water distribution correspond to a consistent binding energy increase. Distinct temperature dependences of each water population are observed, which can be straightly related to water desorption into ice on cooling below the freezing point.

Реакции пентафенилсурьмы и пента-пара-толилсурьмы с каликсареном [4-t-BuC6H2OH(S-2)

Pentaphenylantimony and penta-para-tolylantimony react with calixarene [4-t-BuC6H2OH(S-2)]4 (СArH) by way of arene elimination and formation of the [Ph4Sb]+[СAr]- × TolH (1), [p-Tol4Sb]+[CAr]- × H2O (2) ionic products with a yield up to 96%. The compound has been identified by IR spectroscopy and X-ray diffraction analysis. According to the X-ray diffraction data, compounds 1 and 2 are ionic complexes with solvate molecules of toluene (1) and water (2). The cation has a tetrahedral coordination of the antimony atom with aryl ligands at the polyhedron vertices; the anion is represented by the deprotonated form of p-tert-butylthiacalix[4]arene. The three tert-butyl groups, the phenyl ring and solvated toluene in the structure of compound 1, and two tert-butyl fragments in the structure of compound 2 are disordered over two positions. The tetrahedral coordination of antimony atoms in the cations of compounds 1 and 2 is slightly distorted. The CSbC angles deviate from the theoretical value and vary within 106.0(4)−117.7(4)° (1), 105.75(15)−112.84(15)° (2). The average Sb–C bond lengths are 2.101(3) and 2.106(4) Å in structures 1 and 2, respectively. The [СAr]- anion is in the cone conformation, the upper rim of which is represented by the tert-butyl groups in the para-position, while the lower one is represented by hydroxy groups, one of which is deprotonated. The СAr–O– bond length (1.318(4) (1) and 1.326(4) (2) Å) is less than the average value of the СAr–OH bond lengths (1.338(4) (1) and 1.343(4) (2) Å), which indicates increasing multiplicity of the bond and localization of a negative charge on the oxygen atom. Intramolecular hydrogen bonds with the neiboring O atom are observed. The H∙∙∙O distances are 2.16, 1.69, 1.77 Å in 1 and 1.92, 1.79, 1.76 Å in 2. Dihedral angles between opposite phenoxide rings are 60.64° and 87.07° (1) and 83.85° and 80.42° (2), which indicates somewhat less symmetric anion in structure 1 than in structure 2. The formation of the crystal spatial structure is due to the formation of hydrogen bonds between ions with participation of oxygen and sulfur atoms, as well as СН∙∙∙π–interactions, while the ions form chains in the crystal of compound 1, and layers in the crystal of compound 2. Complete tables of atom coordinates, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 1850118 (1); No. 2013220 (2); deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif).

Conformer selective monohydrated clusters of 1,2,3,4 –tetrahydroisoquinoline in S0: I-Potential energy surface studies, vibrational signatures and NBO analysis

The global minima in the potential energy surface of 1, 2, 3, 4-tetrahydroisoquinoline (THIQ):(H2O) prefer the twisted equatorial orientation of the NH group. It is characterized by a strong OH⋅⋅⋅N and a weak O-H⋅⋅⋅π hydrogen bonds. The computations at the ab initio level and DFT methods with M06–2X and ωB97X-D functionals generated consistent results. The monohydrate with the axial orientation of NH having a single OH⋅⋅⋅N bond in the twisted configuration of THIQ is higher by 240 ± 40 cm−1. The N⋅⋅⋅H bond length is smaller in the latter. All the clusters are located in the potential energy surface of THIQ :(H2O) drawn with the variation of the dihedral angles of the saturated ring of THIQ. Various kinds of hydrogen bonds are observed. Binding energy of each structure is computed incorporating BSSE corrections. Interestingly, the largest of them correspond to a conformer of THIQ, where it was a transition state in the bare molecule. The vibrational analysis of the clusters indicates the reassignment of a number of bands in the observed IR spectra. The red-shifts observed in the different stretching modes of water in the two lowest energy clusters are suitably explained. This is further verified from NBO computations. The changes in s-character, NBO energies and OH bond lengths with the variation of hydrogen bond distances clearly signify the dominant nature of hyperconjugation mechanism. The natures of each OH bonds of water are investigated thoroughly. The bond which is not taking part in hydrogen bonding shows some apparently unexpected behaviors. HOMO and LUMO plots and their energy differences are employed to qualitatively explain the experimental results observed earlier. Changes in Molecular Electrostatic Potentials (MEP) on cluster formation are explained and confirm our computations. Maximum hardness principle (MHP) is followed by the most stable monohydrate only. Hardness values display a certain arrangement depending on the type of hydrogen bonding sites. We suggest further experiments to confirm our key observations.

Relative order of acidity among hydroxyl groups of oxyluciferin and emission light colors in aqueous solution

The magnitude of the acidity of the oxyluciferin in water in the ground and excited state is investigated, and it is found for the first time using computational approach that the enol group of the phenol-enol species is the most acidic in the ground state, but the deprotonation of the phenol of the phenol-keto form is the most favored in the excited state. The relative order of the acidity among the hydroxyl groups in the oxyluciferin is attributed to the sequence of the OH bond lengths in the enol and phenol group of the phenol-enol form, and the phenol group of the phenol-keto species. The mechanism of determining the dominant emissive species in the excited state is proposed, and the dependence of emission light colors on the photoexcitation energy is elucidated by the high relative concentration of six chemical forms in the ground state and the absorption efficiency.

Cis/Trans Energetics in Epoxide, Thiirane, Aziridine and Phosphirane Containing Cyclopentanols: Effects of Intramolecular OH⋯O, S, N and P Contacts.

A recent computational analysis of the stabilizing intramolecular OH⋯O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that electronic energies of the isomers are lowered by roughly 3 to 4 kcal mol−1 when the OH group of these cyclopentanol systems forms an intramolecular contact with the O, S, N or P atom on the adjacent carbon. The results also suggest that S and P can participate in these stabilizing intramolecular interactions as effectively as O and N in constrained molecular environments. The stabilizing intramolecular OH⋯O, OH⋯S, OH⋯N and OH⋯P contacts also increase the covalent OH bond length and significantly decrease the OH stretching vibrational frequency in every system with shifts typically on the order of −41 cm−1.