Synthesis and vibrational analysis of N‐(2′‐Furyl)‐Imidazole

The N‐(2′‐furyl)‐imidazole ( 1 ) has been prepared and characterized using infrared, Raman and multidimensional nuclear magnetic resonance spectroscopies. Theoretical calculations have been carried out by employing the Density Functional Theory (DFT) method, in order to optimize the geometry of their two conformers in the gas phase and to support the assignments of the vibrational bands of 1 to their normal modes. For a complete assignment of the compound, DFT calculations were combined with Scaled Quamtum Mecanic Force Field (SQMFF) methodology in order to fit the theoretical wavenumber values to the experimental one. Furthermore, Natural Bond Orbital (NBO) and topological properties by Atoms In Molecules (AIM) calculations were performed to analyze the nature and magnitude of the intramolecular interactions. The result reveals that two conformers are expected in liquid phase. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural,vibrational spectra and normal coordinate analysis for two tautomers of 4(5)‐(2′‐furyl)‐imidazole

We have synthesized both the 4 and 5 tautomeric forms of 4(5)‐(2′‐furyl)‐imidazole (1) and investigated their molecular vibrations by infrared and Raman spectroscopies as well as by calculation based on the density functional theory (DFT) approach. Examination of the temperature dependence of IR intensity revealed the band characteristics of the 4 and 5 tautomers of (1). Comparison of experimental and calculated chemical shifts in nuclear magnetic resonance (NMR) spectroscopy was made in order to identify the two tautomeric forms. The assignment of vibrational normal modes was performed, and the force field obtained reproduced the experimental vibrational wavenumbers with a root mean‐square deviation (RMSD) value of ca. 13 cm⁻¹ for both tautomers. The natural bond orbital (NBO) study reveals the characteristics of the electronic delocalization of the two tautomeric structures. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and vibrational analyses of 2‐(2‐benzofuranyl)‐2‐imidazoline

We have studied 2‐(2‐benzofuranyl)‐2‐imidazoline (BFI) and characterized it by using infrared and Raman spectroscopies. The density functional theory (DFT) method together with Pople's basis set shows that two conformers exist for the title molecule as have been theoretically determined in the gas phase and that, probably, an average of both conformations is present in the solid phase. The harmonic vibrational wavenumbers for the optimized geometry of the latter conformer were calculated at the B3LYP/6‐31G* level in the proximity of the isolated molecule. For a complete assignment of the IR and Raman spectra in the compound in the solid phase, DFT calculations were combined with Pulay's scaled quantum mechanics force field (SQMFF) methodology in order to fit the theoretical wavenumbers to the experimental ones. Copyright © 2010 John Wiley & Sons, Ltd.     

Theoretical investigations on 4,4′,5,5′‐tetranitro‐2,2′‐1H,1′H‐2,2′‐biimidazole derivatives as potential nitrogen‐rich high energy materials

The ―NH₂, ―NO₂, ―NHNO₂, ―C(NO₂)₃ and ―CF(NO₂)₂ substitution derivatives of 4,4′,5,5′‐tetranitro‐2,2′‐1H,1′H‐2,2′‐biimidazole were studied at B3LYP/aug‐cc‐pVDZ level of density functional theory. The crystal structures were obtained by molecular mechanics (MM) methods. Detonation properties were evaluated using Kamlet–Jacobs equations based on the calculated density and heat of formation. The thermal stability of the title compounds was investigated via the energy gaps (?E_{LUMO ? HOMO}) predicted. Results show that molecules T5 (D = 10.85 km·s^?1, P = 57.94 GPa) and T6 (D = 9.22 km·s^?1, P = 39.21 GPa) with zero or positive oxygen balance are excellent candidates for high energy density oxidizers (HEDOs). All of them appear to be potential explosives compared with the famous ones, octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetraazocane (HMX, D = 8.96 km·s^?1, P = 35.96 GPa) and hexanitrohexaazaisowurtzitane (CL‐20, D = 9.38 km·s^?1, P = 42.00 GPa). In addition, bond dissociation energy calculation indicates that T5 and T6 are also the most thermally stable ones among the title compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Intermolecular H‐bond in propan‐2‐ol and its solutions with acetonitrile

Formation of propan‐2‐ol–acetonitrile dimers is manifested in the Raman spectra as an appearance of a band of aggregates in the high‐wavenumber side of the CN vibrational band of liquid acetonitrile (∼2 cm⁻¹). The intensity of the band of aggregates changes with a change in the concentration of the mixture (1–0.05 mole fraction). For propan‐2‐ol we carried out nonempirical calculations of a structure of isolated dimer aggregates. The formation of an intramolecular H‐bond between the H and the O atom of the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt \raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip‐1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group of length 2.045 Å is possible in the monomer molecule. The CH₃ groups of alcohol are not equivalent. In the dimer formation, intramolecular H‐bond in the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt \raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip‐1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group is preserved. An intermolecular H‐bond of length 2.045 Å and energy 15 kJ/mole is formed between the H atom of one molecule and the O atom of another molecule of the O H. The length and energy of the H‐bond for the propan‐2‐ol–acetonitrile dimer formations calculate to 2.27 Å and 12.9 kJ/mole, respectively. The H‐bond is formed by σ‐electrons of nitrogen. The experimental data and the results of calculations are in good agreement. Copyright © 2007 John Wiley & Sons, Ltd.     

Experimental and theoretical FT‐IR and FT‐Raman spectroscopic analysis of N1‐methyl‐2‐chloroaniline

In this work, the experimental and theoretical vibrational spectra of N1‐methyl‐2‐chloroaniline (C₇H₈NCl) were studied. FT‐IR and FT‐Raman spectra of the title molecule in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with the 6‐311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT‐IR and FT‐Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. ¹³C and ¹H NMR chemical shifts results were compared with the experimental values. The optimized geometric parameters (bond lengths and bond angles) were given and are in agreement with the corresponding experimental values of aniline and p‐methyl aniline. Copyright © 2008 John Wiley & Sons, Ltd.     

The Raman spectrum of the γ′‐V2O5 polymorph: a combined experimental and DFT study

Structure and vibrational dynamics of γ′‐V₂O₅ synthesized from a pristine γ‐LiV₂O₅ sample via a chemical oxidation route was studied by means of Raman spectroscopy and quantum‐chemical calculations. The calculations based on density functional theory reliably reproduce the experimental structure of the γ′‐V₂O₅ lattice. The calculated Raman spectrum agrees remarkably well with the experimental one. Making use of the agreement, a complete assignment of Raman bands to vibrations of particular structural units is proposed. The comparison of Raman spectra and structural features of α‐V₂O₅ and γ′‐V₂O₅ polymorphs allowed establishing reliable ‘structure–spectrum’ correlations and identifying Raman peaks characteristic for different structural units. Copyright © 2015 John Wiley & Sons, Ltd.     

Density functional theory calculations and vibrational spectra of 2‐bromo‐4‐chloro phenol and 2‐chloro‐4‐nitro phenol

FTIR and FT Raman spectra of 2‐bromo‐4‐chloro phenol (BCP) and 2‐chloro‐4‐nitro phenol (CNP) were recorded in the region 4000–400 and 4000–50 cm⁻¹, respectively. The molecular structure, geometry optimization, and vibrational wavenumbers were investigated. The spectra were interpreted with the aid of normal coordinate analysis based on density functional theory (DFT) using the standard B3LYP/6‐31G** method and basis set combination and was scaled using multiple scale factors, which yield good agreement between the observed and calculated wavenumbers. The results of the calculations are applied to simulate the infrared and Raman spectra of the title compounds, which showed excellent agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Identification of two Ag‐2,2′:6′,2″‐terpyridine surface species on Ag nanoparticle surfaces by excitation wavelength dependence of SERS spectra and factor analysis: evidence for chemical mechanism contribution to SERS of Ag(0)–tpy

Measurement and interpretation of the excitation wavelength dependence of surface‐enhanced Raman scattering (SERS) spectra of molecules chemisorbed on plasmonic, e.g. Ag nanoparticle (NP) surfaces, are of principal importance for revealing the charge transfer (CT) mechanism contribution to the overall SERS enhancement. SERS spectra, their excitation wavelength dependence in the 445–780‐nm range and factor analysis (FA) were used for the identification of two Ag‐2,2′:6′,2″‐terpyridine (tpy) surface species, denoted Ag⁺–tpy and Ag(0)–tpy, on Ag NPs in systems with unmodified and/or purposefully modified Ag NPs originating from hydroxylamine hydrochloride‐reduced hydrosols. Ag⁺–tpy is a spectral analogue of [Ag(tpy)]⁺ complex cation, and its SERS shows virtually no excitation wavelength dependence. By contrast, SERS of Ag(0)–tpy surface complex generated upon chloride‐induced compact aggregate formation and/or in strongly reducing ambient shows a pronounced excitation wavelength dependence attributed to a CT resonance (the chemical mechanism) contribution to the overall SERS enhancement. Both the resonance (λ_exc = 532 nm) and off‐resonance (λ_exc = 780 nm) pure‐component spectra of Ag(0)–tpy obtained by FA are largely similar to surface‐enhanced resonance Raman scattering (λ_exc = 532 nm in resonance with singlet metal to ligand CT (¹ MLCT) transition) and SERS (λ_exc = 780 nm) spectra of [Fe(tpy)₂]²⁺ complex dication. Copyright © 2014 John Wiley & Sons, Ltd.     

Mechanistic study on Mo(CO)6‐catalyzed intramolecular [2 + 2] or [2 + 2 + 1] cycloaddition reaction of 5‐allenyl‐1‐ynes

By means of density functional theory, the Mo(CO)₆‐catalyzed intramolecular [2 + 2] or [2 + 2 + 1] cycloaddition reaction of 5‐allenyl‐1‐ynes was investigated. All the intermediates and transition states were optimized completely at B3LYP/6‐311++G(d,p) level (LANL2DZ(f) for Mo). Calculations indicate that the complexation of 5‐allenyl‐1‐ynes with Mo(CO)₆ occurred preferentially at the triple bond to give the complex M1 and then the complexation with the distal double bond of the allenes generates the complex M5 . In this reaction, Mo(CO)₆‐catalyzed intramolecular [2 + 2] cycloaddition is more favorable than [2 + 2 + 1] cycloaddition. The reaction pathway Mo(CO)₆ + R → M5 → T7 → M12 → M13 → T11 → M18 → P4 is the most favorable one, and the most dominant product predicted theoretically is P4 . The solvation effect is remarkable, and it decreases the reaction energy barriers. Copyright © 2011 John Wiley & Sons, Ltd.     

Density functional theory calculation and vibrational spectral analysis of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one

The Fourier transform infrared (4000–400 cm⁻¹) and Fourier transform Raman (3500–500 cm⁻¹) spectra of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one (Warfarin) have been measured and calculated. The structure optimization has been made using density functional theory (DFT) calculations. Complete vibrational assignments of the observed spectra have been compared with theoretical wavenumbers. The wavenumber increasing in the methyl group shows the electronic hyperconjugation effect. The natural bond orbital (NBO) analysis reveals the hyperconjugation interaction and the intramolecular hydrogen bonding. The first‐order hyperpolarizability has been calculated. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and structural study of 2′‐ and 2′,6′‐positioned methyl‐ and nitro‐substituted 3‐(arylhydrazono)pentane‐2,4‐diones

A systematic series of ortho‐methyl‐ and nitro‐substituted arylhydrazones 2–6 formed by Japp–Klingemann reaction between pentane‐2,4‐dione and the respective aryldiazonium salts have been synthesized and studied by X‐ray crystal structure analysis, with added quantum chemical calculations. The optimized molecular geometries based on DFT calculations, enabling determination of relevant rotational barriers, and the calculated bond and ring critical points, using the method of ‘atoms in molecules’, were found to correspond with the experimental data, involving specific molecular conformations and hydrogen‐bonded ring structure dependent on the ortho‐substitution, thus making possible reliable structural prediction of this compound class. Copyright © 2007 John Wiley & Sons, Ltd.     

Crystal structures of 3‐methyl‐2(1H)‐quinoxalinone and three substituted derivatives

3‐Methyl‐2(1H)‐quinoxalinone and three derivatives (3,7‐dimethyl‐2(1H)‐quinoxalinone, 3‐methyl‐6,7‐dichloro‐2(1H)‐quinoxalinone and 3‐methyl‐7‐nitro‐2(1H)‐quinoxalinone) have been synthesised and analysed by ¹H NMR and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X‐ray single crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3‐Methyl‐2(1H)‐quinoxalinone crystallises in the P2₁/c monoclinic system, 3,7‐dimethyl‐2(1H)‐quinoxalinone in the Pbca orthorhombic system and the two others compounds in the P$\overline {1} $ triclinic system. For the nitro derivative, C? H$\cdots $ N short contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three other compounds N? H$\cdots $ O hydrogen bonds involve the atoms of the heterocyclic ring. Copyright © 2011 John Wiley & Sons, Ltd.     

A combined experimental and density functional study of 1‐(arylsulfonyl)‐2‐R‐4‐chloro‐2‐butenes reactivity towards the allylic chlorine

Nucleophilic substitution and dehydrochlorination reactions of a number of the ring‐substituted 1‐(arylsulfonyl)‐2‐R‐4‐chloro‐2‐butenes are studied both experimentally and theoretically. The developed synthetic procedures are characterized by a general rapidity, cheapness, and simplicity providing moderate to high yields of 1‐arylsulfonyl 1,3‐butadienes (48–95%), 1‐(arylsulfonyl)‐2‐R‐4‐(N,N‐dialkylamino)‐2‐butenes (31–53%), 1‐(arylsulfonyl)‐2‐R‐2‐buten‐4‐ols (37–61%), and bis[4‐(arylsulfonyl)‐3‐R‐but‐2‐enyl]sulfides (40–70%). The density functional theory B3LYP/6‐311++G(2d,2p) calculations of the intermediate allylic cations in acetone revealed their high stability occurring from a resonance stabilization and hyperconjugation by the SO₂Ar group. The reactivity parameters estimated at the bond critical points of the diene/allylic moiety display a high correlation (R² > 0.97) with the Hammett (σ_p) constants. 1‐Arylsulfonyl 1,3‐butadienes are characterized by a partly broken π conjugated system, which follows from analysis of the two‐centered delocalization (δ) and localization (λ) index values. The highest occupied molecular orbital energies of 1‐arylsulfonyl 1,3‐butadienes are lower than those of 1,3‐butadiene explaining their low reactivity towards the Diels–Alder condensation. Copyright © 2015 John Wiley & Sons, Ltd.     

DFT simulations and vibrational analysis of FTIR and FT‐Raman spectra of 2‐amino‐4,6‐dihydroxypyrimidine

This work deals with the vibrational spectroscopy of 2‐amino‐4,6‐dihydroxy pyrimidine (ADHP) by means of quantum chemical calculations. The mid‐ and far FTIR and FT‐Raman spectra were measured in the condensed state. The fundamental vibrational wavenumbers and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6‐311 + G** methods and basis set combinations, and were scaled using various scale factors, which yielded good agreement between the observed and calculated wavenumbers. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on the scaled density functional force field. The results of the calculations were applied to simulate the infrared and Raman spectra of the title compound, which showed excellent agreement with the observed spectra. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure and vibrational analysis of 1‐hydroxy naphthalene based on density functional theory calculations

The solid phase mid‐FTIR and FT‐Raman spectra of 1‐hydroxy naphthalene (HNP) were recorded in the regions 4000–400 and 4000–50 cm, respectively. The spectra were interpreted with the help of normal coordinate analysis following full structure optimization and force field calculations based on the density functional theory (DFT) using the standard B3LYP/6‐31G** method and basis set combination. The results of the calculations were applied to simulate infrared and Raman spectra of the title compound which showed excellent agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

1,1,1‐Trichloro‐3‐(1‐phenethylamino‐ethylidene)‐ pentane‐2,4‐dione—synthesis,spectroscopic, theoretical and structural elucidation

1,1,1‐Trichloro‐3‐(1‐phenethylamino‐ethylidene)‐pentane‐2,4‐dione is spectroscopically and structurally elucidated by means of linear‐polarized IR spectroscopy (IR‐LD) of oriented solids as a colloidal suspension in nematic liquid crystal. Structural information and IR‐spectroscopic assignment are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6‐311++G** basis set. The geometry is characterized with an inramolecular hydrogen bond of NH^…O?C with length of 2.526 Å and a NHO angle of 140.5(1)°. The NH? C(CH₃)C?C? C?O(CH₃) fragment is nearly flat with a maximal deviation of total planarity of 10.4°. Copyright © 2007 John Wiley & Sons, Ltd.     

Rotational disorder in 2‐piperidyl‐5‐nitro‐6 ‐methylpyridine: structural phase transition and its vibrational characteristics

X‐ray diffraction (XRD) studies have shown that 2‐piperidyl‐5‐nitro‐6‐methylpyridine, C₁₁H₁₅N₃O₂, undergoes a structural phase transition at T = 240 K. The room temperature structure is tetragonal, space group I4₁/a, with the unit‐cell dimensions a = 13.993(2) and c = 23.585(5) Å. The pyridine ring takes trans conformation with respect to the piperidine unit. While pyridine is well ordered, the piperidine moiety shows apparent disorder resulting from a libration about the linking N C bond. The low‐temperature phase is monoclinic, space group I2/a. Contraction of the unit‐cell volume by 2.3% at 170 K enables the C H···O linkage between the molecules of the neighbouring stacks. As result, the asymmetric unit becomes bi‐molecular. The thermal librations of the piperidine and methyl groups become considerably reduced at 170 K and nearly fully reduced at about 100 K. The IR spectra and polarised Raman spectra agree with the X‐ray structure and confirm the disorder effect on the piperidine ring. The assignment of the bands observed was made on the basis of DFT chemical quantum calculations. Copyright © 2008 John Wiley & Sons, Ltd.     

Validation of the mPW1PW Quantum chemical calculations for the vibrational study of organic molecules – re‐assignment of the isopropylamine vibrational spectra

The validity of the mPW1PW91 density functional theory (DFT) method coupled to the all‐electron basis set 6‐31G* (mPW1PW/6‐31G*) for the study of amines, using isopropylamine (iPram) as a case study, was evaluated. Validation was performed by comparing the calculated values with the corresponding experimental results obtained and/or reported in the literature. Moreover, the accuracy of that theoretical level was compared with that of other widely used theoretical levels, namely HF/6‐31G*, B3LYP/6‐31G* and MP2/6‐31G*. The effect of basis set improvement within the mPW1PW protocol was evaluated considering the widely used 6‐311G** basis set. On the whole, the results clearly show that the mPW1PW/6‐31G* calculations are a suitable tool for the prediction of the structural and vibrational features of iPram. The validation of the theoretical methodology allowed a complete revision of the vibrational assignments previously reported in the literature, being the result of several proposed re‐assignments. Copyright © 2010 John Wiley & Sons, Ltd.     

Solvent‐dependent structural dynamics of 2(1H)‐pyridinone in light absorbing S4(ππ*) state

The B‐band resonance Raman spectra of 2(1H)‐pyridinone (NHP) in water and acetonitrile were obtained, and their intensity patterns were found to be significantly different. To explore the underlying excited state tautomeric reaction mechanisms of NHP in water and acetonitrile, the vibrational analysis was carried out for NHP, 2(1D)‐pyridinone (NDP), NHP–(H₂O)_n (n = 1, 2) clusters, and NDP–(D₂O)_n (n = 1, 2) clusters on the basis of the FT‐Raman experiments, the B3LYP/6‐311++G(d,p) computations using PCM solvent model, and the normal mode analysis. Good agreements between experimental and theoretically predicted frequencies and intensities in different surrounding environments enabled reliable assignments of Raman bands in both the FT‐Raman and the resonance Raman spectra. The results indicated that most of the B‐band resonance Raman spectra in H₂O was assignable to the fundamental, overtones, and combination bands of about ten vibration modes of ring‐type NHP–(H₂O)₂ cluster, while most of the B‐band resonance Raman spectra in CH₃CN was assigned to the fundamental, overtones, and combination bands of about eight vibration modes of linear‐type NHP–CH₃CN. The solvent effect of the excited state enol‐keto tautomeric reaction mechanisms was explored on the basis of the significant difference in the short‐time structural dynamics of NHP in H₂O and CH₃CN. The inter‐molecular and intra‐molecular ESPT reaction mechanisms were proposed respectively to explain the Franck–Condon region structural dynamics of NHP in H₂O and CH₃CN.Copyright © 2015 John Wiley & Sons, Ltd.