Solid‐State and Solution Structural Studies of 4‐{[C(E)]‐1H‐Azol‐1‐ylimino)methyl}pyridin‐3‐ols

The new N‐salicylideneheteroarenamines 1 – 4 were prepared by reacting the biologically relevant 3‐hydroxy‐4‐pyridinecarboxaldehyde ( 5 ) with 1H‐imidazol‐1‐amine ( 6 ), 1H‐pyrazol‐1‐amine ( 7 ), 1H‐1,2,4‐triazol‐1‐amine ( 8 ), and 1H‐1,3,4‐triazol‐1‐amine ( 9 ). Solution ¹H‐, ¹³C‐, and ¹⁵N‐NMR were used to establish that the hydroxyimino form A is the predominant tautomer. A combination of ¹³C‐ and ¹⁵N‐CPMAS‐NMR with X‐ray crystallographic studies confirms that the same form is present in the solid state. The stabilities and H‐bond geometries of the different forms, tautomers and rotamers, are discussed by using B3LYP/6‐31G** calculations.     

Quantum‐chemical,IR, NMR,and X‐ray diffraction studies on 2‐(4‐chlorophenyl)‐1‐methyl‐ 1H‐benzo[d]imidazole

The title molecule, 2‐(4‐chlorophenyl)‐1‐methyl‐1H‐benzo[d]imidazole (C₁₄H₁₁ClN₂), was prepared and characterized by ¹H NMR, ¹³C NMR, IR, and single‐crystal X‐ray diffraction. The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) ¹H and ¹³C NMR chemical shift values of the title compound in the ground state have been calculated by using the Hartree‐Fock (HF) and density functional theory (DFT/B3LYP) method with 6‐31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies and GIAO ¹H and ¹³C NMR chemical shifts show good agreement with experimental values. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6‐31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, and nonlinear optical (NLO) properties of the title compound were investigated by theoretical calculations. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Synthesis,structural analysis,spectral investigations,and DFT calculations of 1‐(3‐amino‐4‐thia‐1,2‐diazaspiro[4.11]hexadec‐2‐en‐1‐yl)ethan‐1‐one

1‐(3‐amino‐4‐thia‐1,2‐diazaspiro[4.11]hexadec‐2‐en‐1‐yl)ethan‐1‐one was synthesized and experimentally characterized by using FT‐IR, ¹H NMR, ¹³C NMR, and UV–Vis spectroscopy. The structure of the compound was confirmed by single‐crystal X‐ray diffraction. In the crystal structure, the molecules are linked by pairs of N‐H⋯N hydrogen bonds, forming centrosymmetric dimers with the graph‐set motif. The water molecule also plays an important role in the stabilization of the crystal structure, bridging the dimers to form a two‐dimensional supramolecular network. The molecular geometry, frontier molecular orbitals, vibrational frequencies, electronic properties, and molecular electrostatic potential were calculated using density functional theory (DFT) with the B3LYP/6‐311G(d,p) basis set. Geometric parameters, vibrational assignments, and electronic properties such as calculated energies, excitation energies, and oscillator strengths were compared with the experimental data, and it was seen that the theoretical results support the experimental parameters.     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

The Studies of Structure of 2N‐(3‐phenyl‐allyl‐)(5‐phenyl‐[1,3,4] Thiadiazol‐2‐yl) Amine in Solution

2N‐(3‐phenyl‐allyl‐)(5‐phenyl‐[1,3,4] thiadiazol‐2‐yl) amine was studied by means of the ¹H, ¹³C, ¹⁵N NMR spectroscopy and DFT calculations. On the basis of the one‐dimensional ¹H, ¹³C, ¹⁵N‐NMR and two‐dimensional ¹H‐¹³C HMQC, ¹H‐¹³C HMBC, ¹H‐¹⁵N HMQC, ¹H¹H NOESY, ¹H¹H COSY correlation spectra the amine‐type and the imine‐type tautomers have been determined in the solution. Variety of structural forms including: biradical, ionic–biradical, and ionic structures of the amine‐type a and of the imine‐type b , c tautomers exist in the solution. According to the DFT computations the differences in the total energy between a and b , a and c , and b and c tautomers are equal to 1.5 kJ/mol, 1.2 kJ/mol, and 0.3 kJ/mol, respectively.     

Tautomer‐Specific Resonant Photoelectron Imaging of Deprotonated Cytosine Anions

Tautomers of the nucleobases play fundamental roles in spontaneous mutations of DNA. Tautomers of neutral cytosine have been studied in the gas phase, but much less is known about charged species. Here, we report the observation and characterization of three tautomers of deprotonated cytosine anions, [trans‐keto‐amino‐N3H‐H8b] (tKAN3H8b^?), [cis‐keto‐amino‐N3H‐H8a] (cKAN3H8a^?) and [keto‐amino‐H] (KAN1^?), produced by electrospray ionization. Excited dipole‐bound states (DBSs) are uncovered for the three anions by photodetachment spectroscopy. Excitations to selected DBS vibrational levels of cKAN3H8a^? and tKAN3H8b^? yield tautomer‐specific resonant photoelectron spectra. The current study provides further insight into tautomerism of cytosine and suggests a new method to study the tautomers of nucleobases using electrospray ionization and anion spectroscopy.     

Molecular structure and vibrational assignment of α‐chloro acetylacetone: A density functional theory study

The intramolecular hydrogen bond, molecular structure, and vibrational frequencies of α‐chloro acetylacetone have been investigated. Fourier transform infrared and Fourier transform Raman spectra of this compound and its deuterated analogue were recorded in the regions 400–4,000 cm^?1 and 50–4,000 cm^?1, respectively. Rigorous normal coordinate analysis has been performed at the B3LYP/6‐311++G** level of theory for purposes of comparison. The complete vibrational assignment for TFAA has been made on the basis of the calculated potential energy distribution. We also applied the atoms in molecules theory and natural bond orbital method for the analysis of the hydrogen bond in α‐Chloro acetylacetone and acetylacetone. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

The Effects of Microenvironment Polarity and Dendritic Branching of Aliphatic Hydrocarbon Dendrons on the Self‐Assembly of 2‐Ureido‐4‐pyrimidinones

Two series of aliphatic hydrocarbon‐based G1–G3 dendritic 2‐ureido‐4‐pyrimidinones (UPy) ( S‐Gn )₂ and ( L‐Gn )₂, differing from one another by the distance between the branching juncture to the urea end, were prepared and characterized. These hydrocarbon dendrons were also appended to a p‐aminonitrobenzene solvatochromic chromophore in order to probe their microenvironment polarity. While positive solvatochromism was observed which indicated the chromophore was solvent accessible, there was no significant difference between the microenvironment polarities on going from the G1 to the G3 dendrons. The self‐assembling behavior and tautomeric preference of the dendritic UPy derviatives were examined by ¹H NMR spectroscopy. The dimerization constants (K_dim*) of the DDAA tautomers were unchanged at 10⁷ M ^?1 in CDCl₃ at both 25 and 50 °C, which were comparable to those of UPy compounds bearing other nonpolar substitutents. Furthermore, the lower limits on the K′_dim* of the DADA tautomeric forms of the ( S‐Gn )₂ and ( L‐Gn )₂ series were determined to be 10⁶ and 10⁵ M ^?1 in CDCl₃, respectively. It was found that a closer proximity of the dendron branching juncture to the UPy unit could lead to a destabilization effect on the dimeric states. Hence, the ( L‐Gn )₂ dimers are more stable than those of ( S‐Gn )₂ in the DDAA form, but the latter are more stable than the former in the tautomeric DADA state. This study showed that both the highly nonpolar microenvironment and the proximity of the dendritic branching juncture to the UPy motif could alter the strength and profile of the hydrogen bond‐mediated self‐assembling process.     

An X‐ray crystallographic and density functional theory study of (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one

The Schiff base enaminones (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₃H₁₇NO₄S, (I), and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₅H₂₁NO₂, (II), were studied by X‐ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C—C=C—N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino–phenol group canted relative to the rest of the molecule; the twist about the N(enamine)—C(aryl) bond leads to dihedral angles of 40.5 (2) and −116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N—H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one‐dimensional hydrogen‐bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H—O hydrogen bond, and consequently also forms a one‐dimensional hydrogen‐bonded chain. The DFT‐calculated structures [in vacuo, B3LYP/6‐311G(d,p) level] for the keto tautomers compare favourably with the X‐ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol⁻¹ lower in energy than the enol tautomers for (I) and (II), respectively.     

Experimental and Theoretical Study on New Zn(II) Halide Complexes of 3,5-Diazaindole

3,5-Diazaindole — zinc(II) halide complexes (halogen: Cl, Br, I) are synthesized for the first time. Experimental mid-IR spectra of the compounds were recorded in the range 4000–550 cm^–1, and far-IR spectrum of the zinc(II) chloride complex is recorded in range 700–40 cm^–1. The structural features of the zinc(II) halide complexes of 3,5-diazaindole (ICPY) are studied by quantum chemical methods. The optimized geometry and vibrational frequencies of the ICPY — zinc(II) halide complexes are calculated using the B3LYP/DFT method with the LANL2DZ basis set in the ground state. Vibrational assignments of the most important bands are made with the help of the vibrational energy distribution analysis. The frontier molecular orbital energies, NBO charges, and dipole moments are presented. ¹H and ¹³C NMR spectra of the zinc(II) chloride complex is also given.     

Theoretical Study on Gas—phase Pyrolytic Reactions of N—Ethyl,Isopropyl and N—t—Butyl Substituted 2—Aminopyrazine

Density functional theory (DFT) and ab initio methods were used to study gas‐phase pyrolytic reaction mechanisms of iV‐ethyl, N‐isopropyl and N‐t‐butyl substituted 2‐aminopyrazine at B3LYP/6–31G* and MP2/6–31G*, respectively. Single‐point energies of all optimized molecular geometries were calculated at B3LYP/6–311 + G(2d,p) level. Results show that the pyrolytic reactions were carried out through a unimolecular first‐order mechanism which were caused by the migration of atom H(17) via a six‐member ring transition state. The activation energies which were verified by vibrational analysis and correlated with zero‐point energies along the reaction channel at B3LYP/6–311 + G(2d,p) level were 252.02 kJ. mo^?1 (N‐ethyl substituted), 235.92 kJ‐mol^?1 (N‐t‐isopropyl substituted) and 234.27 kJ‐mol^?1 (N‐t‐butyl substituted), respectively. The results were in good agreement with available experimental data.     

An experimental and theoretical approach to the molecular structure of 3‐{[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐ indol‐2‐one

The title molecule, 3‐{[4‐(3‐methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐indol‐2‐one (C₂₂H₂₀N₄O₁S₁), was prepared and characterized by ¹H NMR, ¹³C NMR, IR, UV–visible, and single‐crystal X‐ray diffraction. The compound crystallizes in the monoclinic space group P21 with a = 8.3401(5), b = 5.6976(3), c = 20.8155(14) Å, and β = 95.144(5)°. Molecular geometry from X‐ray experiment and vibrational frequencies of the title compound in the ground state has been calculated using the Hartree–Fock with 6‐31G(d, p) and density functional method (B3LYP) with 6‐31G(d, p) and 6‐311G(d, p) basis sets, and compared with the experimental data. The calculated results show that optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies values show good agreement with experimental data. Density functional theory calculations of the title compound and thermodynamic properties were performed at B3LYP/6‐31G(d, p) level of theory. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

CH⋅⋅⋅N Hydrogen‐Bonding Interaction in 7‐Azaindole:CHX3 (X=F,Cl) Complexes

The C?H???Y (Y=hydrogen‐bond acceptor) interactions are somewhat unconventional in the context of hydrogen‐bonding interactions. Typical C?H stretching frequency shifts in the hydrogen‐bond donor C?H group are not only small, that is, of the order of a few tens of cm^?1, but also bidirectional, that is, they can be red or blue shifted depending on the hydrogen‐bond acceptor. In this work we examine the C?H???N interaction in complexes of 7‐azaindole with CHCl₃ and CHF₃ that are prepared in the gas phase through supersonic jet expansion using the fluorescence depletion by infra‐red (FDIR) method. Although the hydrogen‐bond acceptor, 7‐azaindole, has multiple sites of interaction, it is found that the C?H???N hydrogen‐bonding interaction prevails over the others. The electronic excitation spectra suggest that both complexes are more stabilized in the S₁ state than in the S₀ state. The C?H stretching frequency is found to be red shifted by 82 cm^?1 in the CHCl₃ complex, which is the largest redshift reported so far in gas‐phase investigations of 1:1 haloform complexes with various substrates. In the CHF₃ complex the observed C?H frequency is blue shifted by 4 cm^?1. This is at variance with the frequency shifts that are predicted using several computational methods; these predict at best a redshift of 8.5 cm^?1. This discrepancy is analogous to that reported for the pyridine‐CHF₃ complex [W. A. Herrebout, S. M. Melikova, S. N. Delanoye, K. S. Rutkowski, D. N. Shchepkin, B. J. van der Veken, J. Phys. Chem. A­ 2005 , 109, 3038], in which the blueshift is termed a pseudo blueshift and is shown to be due to the shifting of levels caused by Fermi resonance between the overtones of the C?H bending and stretching modes. The dissociation energies, (D₀), of the CHCl₃ and CHF₃ complexes are computed (MP2/aug‐cc‐pVDZ level) as 6.46 and 5.06 kcal mol^?1, respectively.     

复合物HNO···H2O2内N-H···O蓝移氢键的理论研究

A theoretical study on the blue-shifted H-bond N-H…O and red-shifted H-bond O-H…O in the complexHNO…H_2O_2 was conducted by employment of both standard and counterpoise-corrected methods to calculate thegeometric structures and vibrational frequencies at the MP2/6-31G(d),MP2/6-31 G(d,p),MP2/6-311 q G(d,p),B3LYP/6-31G(d),B3LYP/6-31 G(d,p) and B3LYP/6-311 G(d,p) levels.In the H-bond N-H…O,the calcu-lated blue shift of N-H stretching frequency is in the vicinity of 120 cm~(-1) and this is indeed the largest theoreticalestimate of a blue shift in the X-H…Y H-bond ever reported in the literature.From the natural bond orbital analy-sis,the red-shifted H-bond O-H…O can be explained on the basis of the dominant role of the hyperconjugation.For the blue-shifted H-bond N-H…O,the hyperconjugation was inhibited due to the existence of significant elec-tron density redistribution effect,and the large blue shift of the N-H stretching frequency was prominently due tothe rehybridization of sp~n N-H hybrid orbital.     

2‐(Dinitromethylene)‐1‐nitro‐1, 3‐diazacyclopentane‐Based Energetic Salts

Energetic salts that contain nitrogen‐rich cations and the 2‐(dinitromethyl)‐3‐nitro‐1, 3‐diazacyclopent‐1‐ene anion were synthesized in high yield by direct neutralization reactions. The resulting salts were fully characterized by multinuclear NMR spectroscopy (¹H and ¹³C), vibrational spectroscopy (IR), elemental analysis, density and differential scanning calorimetry (DSC), and elemental analysis. Additionally, the structures of the ammonium ( 1 ) and isopropylideneaminoguanidinium ( 9 ) 2‐(dinitromethyl)‐3‐nitro‐1, 3‐diazacyclopent‐l‐ene salts were confirmed by single‐crystal X‐ray diffraction. Solid‐state ¹⁵N NMR spectroscopy was used as an effective technique to further determine the structure of some of the products. The densities of the energetic salts paired with organic cations fell between 1.50 and 1.79 g · cm^–3 as measured by a gas pycnometer. Based on the measured densities and calculated heats of formation, detonation pressures and velocities were calculated using Explo 5.05 and found to to be 25.2–35.5 GPa and 7949–9004 m · s^–1, respectively, which make them competitive energetic materials.     

Theoretical study addressing the effects of tautomerism and explicit/implicit water molecules on NQR and NMR parameters of tetrazole‐5‐thione

DFT/B3LYP calculations were employed to study the effects of tautomerism and explicit/implicit water molecules on Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) tensors of nitrogen nuclei in tetrazole‐5‐thione structure. The obtained results revealed that nuclear quadrupole coupling constant (χ) and isotropic chemical shielding (σ_iso) values of nitrogen nuclei in tetrazole ring of five possible tautomeric forms of tetrazole‐5‐thione, i.e. two thione forms called tautomers A and E and three thiol forms called tautomers B, C, and D, were functions of resonance energy(E₂) values of nitrogen lone pairs. Furthermore, it was observed that by increasing participation of lone pairs of nitrogen atoms in the ring resonance interactions, the σ_iso values around them were increased, while their χ and q_zz values were decreased. However, the results indicated that with exception of tautomer B, the order of q_zz and χ values of nitrogen nuclei in tetrazole ring was exactly opposite of the order of resonance energy values for the same nitrogen nuclei in all tautomers and their mono‐hydrated complexes. In addition, a significant decrease was noticed in χ and q_zz values when a water molecule was put in different positions near the tetrazole ring in tautomers A–E. The mentioned result can be attributed to hydrogen bond formation between nitrogen nuclei and the oxygen of water. In mono‐hydrated complexes, the σ_iso values around nitrogen atoms acting as hydrogen donors in hydrogen bond formation (N―H….OH₂) were decreased, while its values were increased for nitrogen atoms acting as hydrogen acceptors in hydrogen bond formation(N….H―OH). Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental and Theoretical Studies of 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine: A Potential Antibacterial Agent

The title compound ( 1 ), 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine (C₂₀H₁₆Cl₂N₆), was synthesized and structurally characterized by elemental analysis, ¹H NMR and ¹³C NMR and single crystal X‐ray diffraction. The compound crystallizes as a colourless needle shaped in the triclinic system, space group P‐1 with cell constants: a = 10.7557(11) Å, b = 12.7078(17) Å, c = 15.511(2) Å, α = 68.029(4)0, β = 86.637(5)0, γ = 87.869(4)0; V = 1962.4 (4) ų, Z = 4. There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, which is linked via N‐H…Cl hydrogen bond. An intramolecular C‐H…N hydrogen also occurs in each molecule. In the crystal, each of independent molecules forms a centrosymmetric dimer with an R²₂(8) ring motifs through a pair of N‐H…N hydrogen bonds. These dimers are further connected by intermolecular N‐H…Cl and C‐H…Cl hydrogen bonds, forming an infinite two dimensional supramolecular network lying parallel to the [010] plane. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6‐311G (d, p) basis set and compared with the experimental data. Mulliken population analyses on atomic charges, HOMO‐LUMO energy levels, Molecular electrostatic potential and chemical reactivity of the title compound were investigated by theoretical calculations. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. The in vitro antibacterial activity has been screened against Gram‐positive (Bacillus cerus and Staphylococcus epidermidis) and Gram‐Negative (Escherichia coli, Acinetobacter baumannii and Proteus vulgaris). The results revealed that the compound exhibited good to moderate antibacterial activity.     

IR and Raman Vibrational Assignments for Metal-free Phthalocyanine from Density Functional B3LYP／6-31G（d） Method

Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.     

Applicability of density functional theory in reproducing accurate vibrational spectra of surface bound species

The structural equilibrium parameters, the adsorption energies, and the vibrational frequencies of the nitrogen molecule and the hydrogen atom adsorbed on the (111) surface of rhodium have been investigated using different generalized‐gradient approximation (GGA), nonlocal correlation, meta‐GGA, and hybrid functionals, namely, Perdew, Burke, and Ernzerhof (PBE), Revised‐RPBE, vdW‐DF, Tao, Perdew, Staroverov, and Scuseria functional (TPSS), and Heyd, Scuseria, and Ernzerhof (HSE06) functional in the plane wave formalism. Among the five tested functionals, nonlocal vdW‐DF and meta‐GGA TPSS functionals are most successful in describing energetics of dinitrogen physisorption to the Rh(111) surface, while the PBE functional provides the correct chemisorption energy for the hydrogen atom. It was also found that TPSS functional produces the best vibrational spectra of the nitrogen molecule and the hydrogen atom on rhodium within the harmonic formalism with the error of ?2.62 and ?1.1% for the N? N stretching and Rh? H stretching frequency. Thus, TPSS functional was proposed as a method of choice for obtaining vibrational spectra of low weight adsorbates on metallic surfaces within the harmonic approximation. At the anharmonic level, by decoupling the Rh? H and N? N stretching modes from the bulk phonons and by solving one‐ and two‐dimensional Schrödinger equation associated with the Rh? H, Rh? N, and N? N potential energy we calculated the anharmonic correction for N? N and Rh? H stretching modes as ?31 cm^?1 and ?77 cm^?1 at PBE level. Anharmonic vibrational frequencies calculated with the use of the hybrid HSE06 function are in best agreement with available experiments. © 2014 Wiley Periodicals, Inc.     

Ultrafast Vibrational Population Transfer Dynamics in 2‐Acetylcyclopentanone Studied by 2D IR Spectroscopy

2‐Acetylcyclopentanone (2‐ACP), which is a β‐dicarbonyl compound, undergoes keto–enol isomerization, and its enol tautomers are stabilized by a cyclic intramolecular hydrogen bond. 2‐ACP (keto form) has symmetric and asymmetric vibrational modes of the two carbonyl groups at 1748 and 1715 cm^?1, respectively, which are well separated from the carbonyl modes of its enol tautomers in the FTIR spectrum. We have investigated 2‐ACP dissolved in carbon tetrachloride by 2D IR spectroscopy and IR pump–probe spectroscopy. Vibrational population transfer dynamics between the two carbonyl modes were observed by 2D IR spectroscopy. To extract the population exchange dynamics (i.e., the down‐ and uphill population transfer rate constants), we used the normalized volumes of the cross‐peaks with respect to the diagonal peaks at the same emission frequency and the survival and conditional probability functions. As expected, the downhill population transfer time constant (3.2 ps) was measured to be smaller than the uphill population transfer time constant (3.8 ps). In addition, the vibrational population relaxation dynamics of the two carbonyl modes were observed to be the same within the experimental error and were found to be much slower than vibrational population transfer between two carbonyl modes.