Symmetric Hydrogen Bonds Research Articles

Raman spectroscopic constraints on compression and metastability of the amphibole tremolite at high pressures and temperatures

Amphiboles, containing up to 2 wt% water in the form of hydroxyl units, contribute significantly to water transport into the deep lithosphere and upper mantle in subduction zones, where dehydration reactions make the water available for metasomatic processes and flux melting of the overlying mantle wedge. Here, we investigate the high-pressure and temperature behavior of the calcic end-member amphibole Ca2Mg5Si8O22(OH)2-tremolite. Tremolite is characterized by Raman spectroscopy at pressures to ~ 49 GPa at room temperature, and at temperatures up to 540 K at ambient pressure. The behavior of the hydroxyl stretching vibration, concordant with previous infrared spectroscopic results, implies that the role of Davydov splitting in this amphibole is small, and the monotonically increasing mode shift of the hydroxyl peak under pressure indicates no approach toward hydrogen-bond symmetrization. As with a range of other hydroxyl-bearing minerals, the hydroxyl librations have slightly negative pressure-induced mode shifts. Intensity trends of Raman peaks that involve Ca–O displacements suggest changes in the calcium cation bonding environment above 10 GPa. The peak shifts of 18 modes are used to determine their isothermal and isobaric mode-Gruneisen parameters (γiT and γiP). The intrinsic mode anharmonicities, calculated from the Gruneisen parameters, indicate largely quasi-harmonic internal mode vibrations while the lower frequency vibrations associated with cations display significant anharmonicity. The general topology of the tremolite structure remains metastable to ~ 50 GPa, and our work provides constraints on the metastability of amphiboles in subduction zones and the upper mantle, as well as the intrinsic crystallographic stability of the monoclinic amphibole structure.

Can HHe+ exist at high pressure: Exploration of high pressure induced HF–He compounds

HHe+ is considered as the strongest acid and most powerful proton donor known to human. Whether HHe+ exists at planetary high pressure environment is a quite important problem in physics, chemistry and planetary sciences. Here, using the ab initio evolutionary algorithm USPEX package, we searched HF–He system, which was reported as the most possible candidate to contain HHe+. The calculation proved HHe+ cannot form at pressure <1000 ​GPa, due to a conflict between the covalent component in symmetric hydrogen bond and ionic HHe+. Although He atoms have no chemical bonding with other elements, they can supply a chemical pressure, leading to two new phases He2(HF)4 and He(HF). With coplanar (HF)4 rings, He2(HF)4 have an aromaticity-like electronic behavior while He(HF) has a new type of chiral HF chain. The formation of He2(HF)4 and He(HF) prove that the chemical pressure from He, on par with external pressure, have ability to control the structural and electronic configuration and induce some new familiars of compounds include H and He elements which are fundamental planetary materials in giant planets.

An unusually short inter-molecular N-H⋯N hydrogen bond in crystals of the hemi-hydro-chloride salt of 1-exo-acetamido-pyrrolizidine.

The title compound [systematic name: (1R*, 8S)-2-acetamidoocta-hydro-pyrrol-izin-4-ium chloride-N-[(1R, 8S)-hexa-hydro-1H-pyrrolizin-2-yl)acetamide (1/1)], 2(C9H16N2O)·HCl or C9H17N2O+·Cl-·C9H16N2O, arose as an unexpected product when 1-exo-acetamido-pyrrolizidine (AcAP; C9H16N2O) was dissolved in CHCl3. Within the AcAP pyrrolizidine group, the unsubstituted five-membered ring is disordered over two orientations in a 0.897 (5):0.103 (5) ratio. Two AcAP mol-ecules related by a crystallographic twofold axis link to H+ and Cl- ions lying on the rotation axis, thereby forming N-H⋯N and N-H⋯Cl⋯H-N hydrogen bonds. The first of these has an unusually short N⋯N separation of 2.616 (2) Å: refinement of different models against the present data set could not distinguish between a symmetrical hydrogen bond (H atom lying on the twofold axis and equidistant from the N atoms) or static or dynamic disorder models (i.e. N-H⋯N + N⋯H-N). Computational studies suggest that the disorder model is slightly more stable, but the energy difference is very small.

Thermally Activated Transient Dipoles and Rotational Dynamics of Hydrogen-Bonded and Charge-Transferred Diazabicyclo [2.2.2]Octane Molecular Rotors.

We present here dielectric properties and rotational dynamics of cocrystals formed with either triphenylacetic acid (cocrystal I) or 9,10-triptycene dicarboxylic acid (cocrystal II), as hydrogen-bonding donors, and diazabicyclo[2.2.2]octane (DABCO), as a ditopic hydrogen-bond acceptor. While cocrystal I forms discrete 2:1 complexes with one nitrogen of DABCO hydrogen bonded and the other fully proton transferred, cocrystal II consists of 1:1 complexes forming infinite 1-D hydrogen-bonded chains capable of exhibiting a thermally activated response in the form of a broad asymmetric peak at ca. 298 K that extends from ca. 200 to 375 K in both the real and imaginary parts of its complex dielectric. The state of protonation in cocrystal II at 298 and 386 K was established by CPMAS 15N NMR, which showed signals typical of a neutral hydrogen-bonded complex. Taken together, these observations suggest a dielectric response that results from a small population of transient dipoles thermally generated when acidic protons are transiently transferred to either side of the DABCO base. A potential order-disorder transition further explored by taking advantage of the highly sensitive rotational dynamics of the DABCO group using line-shape analysis of solid-state spin echo 2H NMR and 1H NMR T1 spin-lattice relaxation showed no breaks in the Arrhenius plot or Kubo-Tomita 1H T1 fittings, indicating the absence of large structural changes. This was confirmed by variable-temperature single-crystal X-ray diffraction analysis, which showed a fairly symmetric hydrogen bond in cocrystal II at all temperatures, suggesting that both nitrogen atoms may be able to adopt a protonated state.

Heavy metal complexes of 4-chlorodipicolinic acid - structural, spectral and thermal correlations

The ligand, 4-chloro-2,6-dipicolinic acid (H2PDA-Cl), and its two heavy metal complexes, [Ag(HDPA-Cl)(H2DPA-Cl)·2H2O] (1) and {[Cd(μ2-H2O)(H2O)(PDA-Cl)]}n (2), were prepared and then characterized by single-crystal X-ray diffraction. In addition, spectral and thermal correlations with structural results complete their solid-state description and facilitate complex 3 ([Pb(DPA-Cl)]) composition determinations. Complex 1 crystallizes in a monoclinic space group C2/c and each DPA-Cl ligand is tridentate to Ag(I) through the pyridine N and two monodentate carboxyl O atoms. The carboxy group with carbonyl C1 is semideprotonated and forms a symmetric hydrogen bond with a carboxy group of a neighboring complex. Complex 2 crystallizes in a triclinic lattice with space group P The Cd(II) ions are seven-coordinate and the coordination polyhedra can be described as a distorted pentagonal bipyramid. IR data are consistent with monodentate coordination of the carboxylate to Ag(I), Cd(II), and Pb(II) and observed wavenumber shifts confirm PDA-Cl ligand coordination to Pb(II) in 3. Thermal stability of anhydrous complexes indicates the metal–ligand interactions. The thermal stability of prepared compounds is reflected by the strength of interaction between metal–ligand and hydrogen bonds.

Structure of Na3[Al(L-Lactate)3]2·6H2O Crystallized from Lohtragon AL 250—A Commercial Cement Adjuvant

Aqueous aluminum(III) solutions at medium pH are used for industrial applications such as cement adjuvants. The necessary high Al3+ concentrations are achieved by using complexing ligands, such as lactic acid, to prevent precipitation. Here, we grew crystals from commercially available neutralized aluminum lactate solutions to derive an understanding of the underlying aluminum lactate chemistry. Using X-ray diffraction in combination with multinuclear NMR spectroscopy and quantum mechanical calculations, we found that the crystals have a stoichiometry of Na3[Al(l-lactate)3]2·6H2O and consist of negatively charged [Al(l-lactate)3]23– bis-clusters. The remarkable stability of these clusters is achieved by linking both Al(l-lactate)3 subunits via three very short symmetrical hydrogen bonds between the α-hydroxy groups with half of them being deprotonated. The trends for both the 27Al chemical shift and the spin–spin relaxation for the Lohtragon-type solutions as a function of pH suggest the bis-cluster to be...

The role of water in Earth's mantle.

Geophysical observations suggest that the transition zone is wet locally. Continental and oceanic sediment components together with the basaltic and peridotitic components might be transported and accumulated in the transition zone. Low-velocity anomalies at the upper mantle–transition zone boundary might be caused by the existence of dense hydrous magmas. Water can be carried farther into the lower mantle by the slabs. The anomalous Q and shear wave regions locating at the uppermost part of the lower mantle could be caused by the existence of fluid or wet magmas in this region because of the water-solubility contrast between the minerals in the transition zone and those in the lower mantle. δ-H solid solution AlO2H–MgSiO4H2 carries water into the lower mantle. Hydrogen-bond symmetrization exists in high-pressure hydrous phases and thus they are stable at the high pressures of the lower mantle. Thus, the δ-H solid solution in subducting slabs carries water farther into the bottom of the lower mantle. Pyrite FeO2Hx is formed due to a reaction between the core and hydrated slabs. This phase could be a candidate for the anomalous regions at the core–mantle boundary.

Unprecedented hydrophobic stabilizations from a reverse wobble T·T mispair in DNA minidumbbell

Minidumbbell (MDB) is a newly found non-B DNA structure formed by short single-strand sequences. Up to now, three MDBs have been reported to form at neutral pH by sequences containing two repeats of TTTA, CCTG and CTTG. Among them, the thermodynamically less stable TTTA and CCTG MDBs have been proposed to be the structural intermediates that cause TTTA and CCTG repeat expansions during DNA replication in Staphylococcus aureus pathogen and myotonic dystrophy type 2 patients, respectively. Although the CTTG MDB has a melting temperature of at least 13 °C higher than those of the other two, no CTTG repeat expansion has ever been reported in any genomes. In this study, we successfully determined the solution structure of the CTTG MDB and observed for the first time the formation of a reverse wobble T·T mispair with two symmetric hydrogen bonds. More importantly, we identified unprecedented hydrophobic interactions between the two methyl groups of this T·T mispair and the four 2′-methylene groups of their nearby loop-closing base pair residues. These stabilizations account for the substantial increase in the MDB thermodynamic stability which may govern the occurrence of repeat expansions.Communicated by Ramaswamy H. Sarma

Structure and disorder in ice VII on the approach to hydrogen-bond symmetrization

We have collected neutron-diffraction data of sufficient quality for structural refinement from deuterated ice VII to over 60 GPa. At these pressures, we are approaching the onset of molecular dissociation where the water molecule should be significantly distorted. We fitted our data with both the conventional structural model for ice VII and a recently proposed ``interstitial'' model. We found these to be statistically indistinguishable and, therefore, adopted the conventional model in this work. Our refinements yield the first direct experimental determination of the molecular structure in this pressure regime. They show a clear elongation of the covalent bond, the rate of which rapidly increases with pressure, indicating we have entered a distinct regime on the approach to ice X. In addition, we have directly measured the pressure dependence of the separation of the two equivalent deuteron sites along the hydrogen bonds, which provides an upper bound on the hydrogen-bond centering pressure.

A Novel Sodium and Chromium Borophosphate Na{Cr[BP2O7(OH)3]}: Synthesis, Crystal Structure, Hydrogen Bonding, and Comparative Crystal Chemistry

A novel sodium and chromium borophosphate, obtained by hydrothermal synthesis in the Na2O–P2O5–B2O3–Cr2O3–Н2О system, has been investigated using X-ray diffraction and IR spectroscopy. The monoclinic cell parameters are found to be a = 10.4220(3) A, b = 8.2468(2) A, c = 9.2053(3) A, β = 116.568(4)°, and V = 707.63(4) A3; sp. gr. С2/с. The structure is interpreted and refined to the final reliability factor R1 = 2.23% in the anisotropic approximation of atomic displacements using 1311 reflections, I > 2σ(I). The novel compound is relative to the family of alkaline borophosphates with the general formula A{M[BP2O7(OH)3]} (A is an alkaline or alkaline-earth element; M is a transition метал) and is described by the crystallochemical formula (Z = 4) Na{Cr[BP2O7(OH)3]}, where the compositions of borophosphate anion and microporous framework are in square brackets and braces, respectively. The presence of alternative systems of strong symmetric hydrogen bonds is established; the localization of all hydrogen atomic sites has made it possible to analyze them in detail. An additional electron density peak is found, which can be interpreted as a statistically distributed proton H+. The IR spectrum is characteristic of compounds with strong hydrogen bonding; it confirms the statistical proton distribution over subsites around the inversion center. It is suggested that representatives of this family may possess proton conductivity.

Isotope effect on hydrogen bond symmetrization in hydrogen and deuterium fluoride crystals by molecular dynamics simulation

The isotope effect on the collective proton/deuteron transfer in hydrogen and deuterium fluoride crystals has been investigated at 100 K by ab initio quantum-thermal-bath path-integral molecular dynamics (QTB-PIMD) simulation. The deuterons within a planar zigzag chain of the orthorhombic structure simultaneously flip between covalent and hydrogen bonds due to the barrier crossing through tunnelling. The height of the corresponding static barrier normalized for one deuteron is 29.2 meV. In the HF crystal, all the protons are located at the center of the heavy-atom distance. This evidences the symmetrization of the H-bonds, and indicates that the proton zero-point energy is above the barrier top. The decrease of the heavy-atom distance due to quantum fluctuations in both HF and DF crystals corresponds to a large decrease and an increase of the hydrogen and covalent bond lengths, respectively. Upon deuteration, the increase of the heavy-atom distance (Ubbelohde effect) is in agreement with experimental data.

Direct observation of symmetrization of hydrogen bond in \u03b4-AlOOH under mantle conditions using neutron diffraction

At ambient pressure, the hydrogen bond in materials such as ice, hydrates, and hydrous minerals that compose the Earth and icy planets generally takes an asymmetric O-H···O configuration. Pressure significantly affects this configuration, and it is predicted to become symmetric, such that the hydrogen is centered between the two oxygen atoms at high pressure. Changes of physical properties of minerals relevant to this symmetrization have been found; however, the atomic configuration around this symmetrization has remained elusive so far. Here we observed the pressure response of the hydrogen bonds in the aluminous hydrous minerals δ-AlOOH and δ-AlOOD by means of a neutron diffraction experiment. We find that the transition from P21nm to Pnnm at 9.0 GPa, accompanied by a change in the axial ratios of δ-AlOOH, corresponds to the disorder of hydrogen bond between two equivalent sites across the center of the O···O line. Symmetrization of the hydrogen bond is observed at 18.1 GPa, which is considerably higher than the disorder pressure. Moreover, there is a significant isotope effect on hydrogen bond geometry and transition pressure. This study indicates that disorder of the hydrogen bond as a precursor of symmetrization may also play an important role in determining the physical properties of minerals such as bulk modulus and seismic wave velocities in the Earth’s mantle.

IR photodissociation spectra of SixH4x-4+ (x = 4–8): Evidence for Si[sbnd]H[sbnd]Si proton bridges

Although silane-type cations of the form SixHy+ are thought to play a significant role in plasma chemistry and astrochemistry, their structural and energetic properties are largely unexplored in the size range x ≥ 3. Herein, infrared photodissociation (IRPD) spectra of mass-selected SixHy+ ions (specifically SixH4x-4+ with x = 4–8, Si4H12+-Si8H28+) are recorded in the SiH stretch range and analyzed by dispersion-corrected density functional calculations at the B3LYP-D3/aug-cc-pVDZ level. The SixH4x-4+ ions are produced in a SiH4/H2/He plasma molecular beam expansion. The IRPD process leads to the loss of SiH4 ligands, which corresponds to the lowest-energy fragment channel. Spectral analysis of the IRPD spectra reveals that all SixH4x-4+ ions have at least one SiHSi bridge. The characteristic fingerprint of these three-center two-electron (3c-2e) bonds is the highly IR active antisymmetric stretch fundamental of the SiHSi bridge (σ SiHSi) occurring in the 1600–2100 cm−1 range, whose frequency strongly depends on the structural and energetic details of the SiHSi bridge. Although the investigated SixH4x-4+ ions can formally be described by the formula Si2H4+(SiH4)x-2, the cluster growth is more complex. The appearance of the σSiHSi bands confirms that all considered SixH4x-4+ ions with x ≤ 5 are formed by polymerization reactions. Larger clusters (x ≥ 6) show evidence for the additional presence of weakly-bonded SiH4 ligands attached to smaller chemically-bonded core ions. Correlations of the properties of the SiHSi bridges (bond distances, bond angles, binding energies, SiH stretch frequencies), which vary between strong symmetric 3c-2e chemical bonds and weak hydrogen bonds, are discussed.

Coupled High Spin CoII Ions Linked by Symmetrical Double Hydrogen Bonds: Role of a Slowly Relaxing CuII Impurity in Interrupting the CoII–CoII Exchange Interaction

CoII and CuII ions are two paramagnetic transition metal ions showing different relaxation rates (ν), with νCoII &gt;&gt; νCuII. To measure the isotropic exchange constant (J) between high spin CoII ions and between CuII ions and high spin CoII ions, we performed magnetic and EPR measurements complemented with computational calculations on pure trans‐diaqua‐bis(picolinato‐N,O)‐cobalt(II) dihydrate (1), on the CuII ion doped compound of 1 (2), and on the CuII ion doped compound in a ZnII matrix isomorphous to 1. The temperature dependence of the CuII EPR resonance lines of 2 induced by the fast relaxing CoII ion host as well as the evaluation of the temperature‐independent CoII–CoII and CuII–CoII isotropic exchange interaction are analyzed. We determined an antiferromagnetic interaction [JCo–Co = –1.07(1) cm–1] associated with a double symmetrical hydrogen bond bridge and another one [|J|Co–Cu = 0.0015(2) cm–1] associated with a double but asymmetrical hydrogen bond bridge, which are in line with the values obtained from computational calculations. This work shows that EPR spectroscopy can advantageously be used to evaluate weak exchange interactions between distinct metal ions with different relaxation rates by using the fact that those metal–metal interactions that broaden the EPR resonance line, which are described by matrices with a trace of zero, are averaged out at high temperatures.

Pressure-induced superconducting ternary hydride H3SXe: A theoretical investigation

In general, heavy elements contribute only to acoustic phonon modes, which are less important for the superconductivity of hydrides. However, it was revealed that the heavier elements could enhance the phonon-mediated superconductivity in ternary hydrides. In the H3S–Xe system, a novel H3SXe compound was discovered by first-principle calculations. The structural phase transitions of H3SXe under high pressures were studied. The R-3m phase of H3SXe was predicted to appear at pressures above 80 GPa, which transitions to C2/m, P-3m1, and Pm-3m phases at pressures of 90, 160, and 220 GPa, respectively. It has been anticipated that the Pm-3m-H3SXe phase with a similar structural feature as that of Im-3m-H3S is a potential high-temperature superconductor with a Tc of 89 K at 240 GPa. The Tc value of H3SXe is lower than that of H3S at high pressure. The “H3S” host lattice of Pm-3m-H3SXe is a crucial factor influencing the Tc value. The Xe atoms could accelerate the hydrogen-bond symmetrization. With the increase of the atomic number, the Tc value linearly increases in the H3S–noble-gas-element system. This indicates that the superconductivity can be modulated by changing the relative atomic mass of the noble-gas element.

Thermal equation of state of MgSiO4H2 phase H determined by in situ X-ray diffraction and a multianvil apparatus

Phase H (MgSiO4H2) is the high-pressure form of dense hydrous silicate that could deliver surface water into the lower mantle. In this study, we determined the thermal equations of the state of phase H using in situ X-ray diffraction measurements, under conditions ranging from 34 to 62 GPa and 300 and 1300 K, using a multianvil apparatus. Analysis of the data, based on the Mie–Gruneisen–Debye model using third-order Burch–Murnaghan equations at a reference pressure of 35 GPa, yielded the following results Vref = 49.61 ± 0.01 A3, Kref = 344.6±4.1 GPa, $$K_{{{\text{ref}}}}^{\prime }$$ = 3.05 ± 0.32, θref = 974 ± 146 K, γref = 1.8 ± 0.1, and q = 1.79 ± 0.55. The compressibility of phase H observed in this study agrees well with that derived from theoretical calculations in pressure regions where hydrogen bond symmetrization is predicted. It was also found that the volume and compressibility of phase H and δ-AlOOH were similar.

28p-YD-13 高圧氷VII相における水素結合対称化

28p-YD-13 高圧氷VII相における水素結合対称化

Synthesis and structural characterization of lithium, sodium and potassium complexes supported by a tridentate amino-bisphenolate ligand

Reactions of methylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol) (1) with one or two equivalents of bulk Li, Na or K metals in THF or DMSO render mono or dialkali metal complexes depending on the stoichiometric ratio of the reactants. The metal-methylamino-N-(2-methylene-4,6-tert-butylphenol)N-(2-methylene-4,6-tert-butylphenolate) complexes, 2Li, 2Na and 2K, are generated upon the substitution of a single phenol hydrogen of 1. In the solid state, complex 2Na is a dimer due to the establishment of two symmetric hydrogen bonds between two adjacent molecules. The Na center also engages into the formation of a ten-membered metallacycle ring with a butterfly-like structure. Due to dimerization, an intermolecular six-membered core is formed involving two sodium and four oxygen atoms. The weakly coordinated nitrogen atom from the ligand is nearly perpendicular to the hexagonal core. The dimetal-methylamino-N,N′-bis(2-methylene-4,6-di-tert-butylphenolate) complexes, 3Li, 3Na and 3K result from metal substitution of the two phenol hydrogens from ligand 1. The SC-XRD structures of 3Li and 3Na are discreet, each incorporating two metal atoms in different coordination environments. Ten-membered rings with boat-boat conformations are also observed as are rhombic central M2O2 cores. The molecular structure of 3K in DMSO shows a higher degree of aggregation. It effectively comprises four K atoms, two ligand backbones and seven solvent molecules forming a central four-membered K2O2 ring perpendicular to an eight-membered structure formed also by K and O atoms spanning over the two ligand moieties.

First principles study of hydrogen bond symmetrization in δ-AlOOH

The high pressure behaviour of the hydrous mineral δ-AlOOH has been investigated by many experimental and theoretical studies, but the discrepancy in predicting the value of hydrogen symmetrization pressure was not resolved. Here, we investigated the high pressure behaviour of δ-AlOOH using first principles calculations and found that with proper optimization using pressure routine control, local density approximation (LDA) predicts the hydrogen symmetrization pressure as 15 GPa which is in good agreement with the experimentally predicted value which resolves the existing discrepancy and hence proving the validity of LDA in predicting the hydrogen symmetrization pressure. We further studied the compressibility behaviour of δ-AlOOH at low pressures and confirmed the P21nm to Pnnm transition of δ-AlOOH shown by the experimental work [Kuribayashi et al., Phys. Chem. Miner. 41, 303–312 (2014)]. We have also analysed the dependence of elastic constants, elastic moduli, sound velocities, and Raman spectrum of δ-AlOOH with pressure and found that a subtle change in the position of the hydrogen atom at hydrogen symmetrization pressure results into drastic changes in elastic and vibrational properties. Further, this study has been used to discuss the seismic anomalies observed in the upper mantle beneath the Deccan Volcanic Province in India and the Java subduction zone in the eastern flank of the Indian Ocean.

Estimating the energy of intramolecular bifurcated (three-centered) hydrogen bond by X-ray, IR and 1H NMR spectroscopy, and QTAIM calculations

The structure of a series of the 2-substituted pyrroles containing the intramolecular NH⋯OC hydrogen bond and the 2,5-disubstituted pyrroles having the three-centered intramolecular CO⋯H(N)⋯OC hydrogen bond was studied by X-ray, IR, NMR spectroscopy, and quantum chemical calculations, including calculations in terms of Quantum Theory of Atoms in Molecules (QTAIM). The X-ray diffraction data show that the intramolecular rH … O and RN … O distances increase upon conversion from a two-centered hydrogen bond to a three-centered hydrogen bond, indicating a weakening of the last interaction. The topological parameters of the hydrogen bond obtained from the QTAIM calculations (electron density ρBCP and potential energy density V at the critical point of the hydrogen bond) made it possible to quantify the hydrogen bond energy in the studied compounds. The energy of intramolecular NH⋯OC hydrogen bond in the 2-substituted pyrroles is in the range from 5.5 to 6.0 kcal mol−1 (moderate hydrogen bond), whereas the energy of the components of the three-centered intramolecular CO⋯H(N)⋯OC hydrogen bond in the 2,5-disubstituted pyrroles is reduced to 2.5–3.5 kcal mol−1 (weak hydrogen bond). For weak components of the three-centered hydrogen bond, the principle of the additivity of effects on the spectral parameters influenced by the hydrogen bond (change in the vibration frequency of the NH bond, ΔνN‒H, and the chemical shift of bridge proton, ΔδNH) was proposed. For this reason, the ½ΔνN-H and ½ΔδNH values also were used for estimating the energy of the two-centered components of the three-centered CO⋯H(N)⋯OC hydrogen bond. These estimates are in good agreement with those obtained from the ρBCP and V parameters. Consequently, the ½ΔνN-H and ½ΔδNH parameters can be used as an energy descriptor for two-centered components in the case of a symmetric intramolecular three-centered hydrogen bond.