Vibrational spectroscopy and DFT calculations of di‐amino acid cyclic peptides. Part I: cyclo(Gly‐Gly), cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly) in the solid state and in aqueous solution

Investigations of the vibrational spectra of cyclo(Gly‐Gly), cyclo(L‐Ala‐L ‐Ala) and cyclo(L ‐Ala‐Gly) are reported. Raman scattering and Fourier transform infrared (FTIR) spectra of solid‐state and aqueous protonated samples, as well as their corresponding N‐deuterated isotopomers, have been examined. In addition, density functional theory (DFT) (B3‐LYP/cc‐pVDZ) calculations of molecular structures and their associated vibrational modes were carried out. In each case, the calculated structures of lowest energy for the isolated gas‐phase molecules have boat conformations. Assignments have been made for the observed Raman and FTIR vibrational bands of the cyclic di‐amino acid peptides (CDAPs) examined. Raman polarization studies of aqueous phase samples are consistent with C₂ and C₁ symmetries for the six‐membered rings of cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly), respectively. There is a good correlation between experimental and calculated vibrational bands for the three CDAPs. These data are in keeping with boat conformations for cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly) molecules, predicted by the ab initio calculations, in both the solid and aqueous solution states. However, Raman spectroscopic results might infer that cyclo(L‐Ala‐Gly) deviates only slightly from planarity in the solid state. The potential energy distributions of the amide I and II modes of a cis‐peptide linkage are shown to be significantly different from those of the trans‐peptides. For example, deuterium shifts have shown that the cis‐amide I vibrations found in cyclo(Gly‐Gly), cyclo(L‐Ala‐L‐Ala), and cyclo(L‐Ala‐Gly) have larger N‐H contributions compared to their trans‐amide counterparts. Compared to trans‐amide II vibrations, cis‐amide II vibrations show a considerable decrease in N H character. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopy of polyconjugated molecules with electronic and mechanical confinement: the spectrum of Corallium rubrum

The chemical nature of the red pigment of Corallium rubrum (CR) has not yet been clearly identified. We have recorded the Raman spectra of CR, canthaxantin, and parrot feather, and we propose an interpretation with the help of quantum chemistry and of the effective conjugation coordinate theory, which accounts for the main Raman lines (ν₁, ν₂, ν₃) as originating from the polyene backbone. In this study, two additional lines in the 1000 cm⁻¹ range (ν₄ and ν₅) are considered as well as a series of overtones and combinations in the second order Raman spectrum (2000–3000 cm⁻¹). Density Functional Theory calculations predict that, moving with successive methylation from a simple unsubstituted polyene chain with 9 C═C bonds (as psyttacofulvins) to a 9, 9′, 13, 13′ tetramethylated chain (as carotenoids), the geometric structures of the molecules and their Raman spectra show changes that can be rationalized if the effective conjugation coordinate theory is extended to account for mechanical confinement. This turns out to be a new concept that helps the interpretation of the Raman spectra of partially methylated conjugated oligoenes. Evidence is found that the main component of the pigment of CR does not posess a fully demethylated polyene chain (psyttacofulfine) nor a tetramethylated chain (carotenoid), thus indicating that the polyene chain is partially methylated. Because we consider resonance Raman spectra, the target of this study is the structure of the polyene backbone; no direct spectroscopic information can be obtained in this way on the chemical nature of the groups attached to both chain ends. Copyright © 2012 John Wiley & Sons, Ltd.     

Discrimination of carotenoid and flavonoid content in petals of pansy cultivars (Viola x wittrockiana) by FT‐Raman spectroscopy

Fourier Transform Raman spectroscopy (FT‐Raman) has been applied for the non‐destructive in‐situ analysis of pigments on differently colored flower petals of pansy cultivars (Viola x wittrockiana). The main target of the present study was to investigate how far the Raman mapping technique through FT‐Raman spectroscopy and cluster analysis of the Raman spectra is a potential method for the direct, in‐situ discrimination of flavonoids (flavonols against anthocyanins) and of carotenoids occurring in flowers, using intact and differently colored flower petal of Viola x wittrockiana for this case study. In order to get more information about the reliability of the direct in‐situ flavonoid detection by the Raman method, pigments extracts of the petals were separated by thin‐layer chromatography (TLC) and investigated by Raman spectroscopy. Hierarchical cluster analysis (HCA) of the Raman spectra from reference pigments (carotenoids, anthocyanins and flavonols), from areas of the flower petals, and from the TLC extracts allowed discriminating the various pigments, in particular flavonoids (flavonols against anthocyanins) and carotenoids. With a two‐dimensional Raman mapping technique, which provides a chemical image of the sample under investigation, we determined by cluster analysis the distribution of carotenoids, anthocyanins and flavonols from the outer layer of the petals, and by integrating through suitable spectral regions selected as characteristic markers for particular pigments their relative concentration could approximately be determined. We found a satisfactory correlation between the patterns seen on the visible images and the patterns on the chemical images obtained by Raman mapping. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopic characterization of a thiophene‐based active material for resistive organic nonvolatile memories

A combined theoretical and experimental Raman study is presented on a diphenyl bithiophene molecule known as a good candidate for the development of organic nonvolatile memory devices. Spectroscopic markers suitable to distinguish the different stable conformers of the molecule have been predicted and detected. The combined analysis of theoretical and experimental Raman spectra recorded in solution indicates that at room temperature a dynamical equilibrium, characterized by interconversion between the two more stable conformers (namely trans and cis), takes place and that the more populated species is the cis form. Referring to the solid phase instead, Raman spectra of single‐crystal samples show the presence of the only trans conformer, as confirmed by X‐ray measurements. Finally, Raman spectra of thin films, as those used for the memory device, were collected; samples just deposited from solution and after few hours from the deposition were analyzed. Following the evolution of selective spectroscopic Raman markers, an isomerization process from the abundant cis (as‐deposited) to the totally trans (after few hours) conformer in the solid phase was detected. These results open the way to the identification of the molecular isomers present in the thin film of the memory cell and finally of the active molecular species involved in the switching mechanism of the operating device. Copyright © 2009 John Wiley & Sons, Ltd.     

Calculation of absorption and resonance Raman cross sections of ClO2 in the gas‐phase and in solution: including Duschinsky effects

The time‐correlation function formalism has been used to calculate resonance Raman cross sections, excitation profiles, and electronic absorption spectra of the OClO molecule in the gas‐phase and in different solvents like cyclohexane, chloroform, and water. The multidimensional time domain integrals that arise in these calculations have been evaluated for the case in which an X²B₁ òA₁ electronic transition takes place between displaced‐distorted‐rotated harmonic potential energy surfaces. Ab initio calculations have been performed to provide the spectroscopic constants required for the evaluation of these integrals. The calculated absorption spectra and resonance Raman cross sections have been compared with the experimental results. Copyright © 2009 John Wiley & Sons, Ltd.     

FT‐IR and FT‐Raman investigations of the chemosensing material para‐hexafluoroisopropanol aniline

As an important chemosensing material involving hexafluoroisopropanol (HFIP) for detecting nerve agents, para‐HFIP aniline (p‐HFIPA) has been firstly synthesized through a new reaction approach and then characterized by nuclear magnetic resonance and mass spectrometry experiments. Fourier transform infrared absorption spectroscopy (FT‐IR) and FT‐Raman spectra of p‐HFIPA have been obtained in the regions of 4000–500 and 4000–200 cm⁻¹, respectively. Detailed identifications of its fundamental vibrational bands have been given for the first time. Moreover, p‐HFIPA has been optimized and vibrational wavenumber analysis can be subsequently performed via density functional theory (DFT) approach in order to assist these identifications in the experimental FT‐IR and FT‐Raman spectra. The present experimental FT‐IR and FT‐Raman spectra of p‐HFIPA are in good agreement with theoretical FT‐IR and FT‐Raman spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

A single‐crystal Raman and infrared study of the nonlinear optical crystal MBANP

Single‐crystal Raman and polycrystalline thin‐film infrared measurements have been obtained for the polar organic nonlinear optical material 2‐(α‐methylbenzylamino)‐5‐nitropyridine (MBANP). For comparison, thin‐film polycrystalline infrared measurements were also made on 2‐(α‐methylbenzylamino)‐3,5‐dinitropyridine (MBADNP). The long wavelength electronic absorption was measured in several solvents and as a thin solid film. The Raman spectra are dominated by three intense bands attributed to vibrations of the ring, the NO₂ substituent, and the N H bond. The most intense scattering and absorption arose from the α_bb component of the polarisability tensor. This implies that the most significant contribution to the transition polarisability arises from the electronic transition near 383 nm, polarised along the b‐axis of the crystal. The strongest bands in the infrared spectra are also associated with the same three bands, consistent with the predictions of the effective conjugation coordinate (ECC) theory, implying efficient electron–phonon coupling (or electronic delocalisation) in the conjugated system. DFT calculations of vibrational wavenumbers and eigenvectors were used to assign relevant vibrational features and to derive useful information about the molecular structure. This single‐crystal material is also a strong candidate for an efficient laser Raman converter with a large wavenumber shift of 3404 cm⁻¹ and a high damage threshold. Copyright © 2010 John Wiley & Sons, Ltd.     

X‐ray Raman spectroscopy of lithium‐ion battery electrolyte solutions in a flow cell

The effects of varying LiPF₆ salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium‐ion battery electrolyte solvents (ethylene carbonate–dimethyl carbonate and propylene carbonate) have been investigated. X‐ray Raman scattering spectroscopy (a non‐resonant inelastic X‐ray scattering method) was utilized together with a closed‐circle flow cell. Carbon and oxygen K‐edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li⁺ ion concentration in the solvent manifests itself as a blue‐shift of both the π* feature in the carbon edge and the carbonyl π* feature in the oxygen edge. While these oxygen K‐edge results agree with previous soft X‐ray absorption studies on LiBF₄ salt concentration in propylene carbonate, carbon K‐edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.     

Involvement of weak C?H···X hydrogen bonds in metal‐to‐semiconductor regime change in one‐dimensional organic conductors (o‐DMTTF)2X (X = Cl,Br, and I): combined IR and Raman studies

We report on the infrared (IR) and Raman studies of the three isostructural quasi‐one‐dimensional cation radical salts of 3,4‐dimethyl‐tetrathiafulvalene (o‐DMTTF)₂X (X = Cl, Br, and I), which all exhibit metallic properties at room temperature and undergo transitions to a semiconducting state in two steps: a soft metal‐to‐semiconductor regime change in the temperature region T_ρ = 5–200 K and then a sharp phase transition at about T_MI = 50 K. Polarized IR reflectance spectra (700–16 000 cm⁻¹) and Raman spectra (50–3500 cm⁻¹, excitation λ = 632.8 nm) of single crystals were measured as a function of temperature (T = 5–300 K) to assess the eventual formation of a charge‐ordered state below 50 K. Additionally, the temperature dependence of the IR absorption spectra of powdered crystals in KBr discs was also studied. The Raman spectra and especially the bands related to the CC stretching vibration of o‐DMTTF provide unambiguous evidence of uniform charge distribution on o‐DMTTF down to the lowest temperatures, without any modification below 50 K. However, the temperature dependence of Raman spectra indicates a regime change below about 200 K. Temperature dependence of both electronic dispersion and vibrational features observed in the IR spectra also clearly confirms the regime change below about 200 K and shows the involvement of C H···X hydrogen bonds in the electronic localization; some spectral changes can be also related with the phase transition at 50 K. Additionally, using density functional theory methods, the normal vibrational modes of the neutral o‐DMTTF⁰ and cationic o‐DMTTF⁺ species, as well as their theoretical IR and Raman spectra, were calculated. The theoretical data were compared with the experimental IR and Raman spectra of neutral o‐DMTTF molecule. Copyright © 2011 John Wiley & Sons, Ltd.     

Modeling red coral (Corallium rubrum) and African snail (Helixia aspersa) shell pigments: Raman spectroscopy versus DFT studies

Pigments from red coral (Corallium rubrum) and African snail (Helixia aspersa) shell were studied non‐invasively using Raman spectroscopy with 1064‐nm laser beam. The two observed bands because of organic pigments confined in biomineralized CaCO₃ matrix at about 1500 and 1100 cm⁻¹ were assigned to ν(CC) and ν(C―C), respectively. Both signals originate from polyene(s) of largely unknown structure, containing several conjugated CC bonds. The small peak at 1016 cm⁻¹ in the Raman spectrum of coral pigment was assigned to in‐plane ―CH₃ rocking or structural deformation of polyene chain because of spatial confinement in the mineral matrix. The organic pigments in red coral and snail shell were present in inorganic matrix containing aragonite (shell) and calcite (coral). In addition, using Raman spectroscopy, it was observed that aragonite was replaced by calcite as result of healing damaged parts of snail shell. This is an important finding which indicates a great potential of nondestructive Raman spectroscopy instead of X‐ray technique, as a diagnostic tool in environmental studies. To support analysis of the observed Raman spectra detailed calculations using density functional theory (DFT with B3LYP and BLYP density functionals) on structure and vibrations of model all‐trans polyenes were undertaken. DFT calculated CC and C―C stretching frequencies for all‐trans polyenes containing from 2 to 14 CC units were compared with the observed ν(CC) and ν(C―C) band positions of the studied coral and shell. Individual correction factors were used to better match theoretical wavenumbers with observed band positions in red coral and African snail. It was concluded that all‐trans polyene pigments of red coral and dark parts of African snail shell contain 11–12 and 14 CC double bond units, respectively. However, Raman spectroscopy cannot produce any clear information on the presence and nature of the end‐chain substituents in the studied pigments. Copyright © 2016 John Wiley & Sons, Ltd.     

Vibrational spectroscopic studies of the structure of di‐amino acid peptides. Part II: cyclo(L‐Asp‐L‐Asp) in the solid state and in aqueous solution

Solid‐state protonated and N,O‐deuterated Fourier transform infrared (IR) and Raman scattering spectra together with the protonated and deuterated Raman spectra in aqueous solution of the cyclic di‐amino acid peptide cyclo(L ‐Asp‐L ‐Asp) are reported. Vibrational band assignments have been made on the basis of comparisons with previously cited literature values for diketopiperazine (DKP) derivatives and normal coordinate analyses for both the protonated and deuterated species based upon DFT calculations at the B3‐LYP/cc‐pVDZ level of the isolated molecule in the gas phase. The calculated minimum energy structure for cyclo(L ‐Asp‐L ‐Asp), assuming C₂ symmetry, predicts a boat conformation for the DKP ring with both the two L ‐aspartyl side chains being folded slightly above the ring. The CO stretching vibrations have been assigned for the side‐chain carboxylic acid group (e.g. at 1693 and 1670 cm⁻¹ in the Raman spectrum) and the cis amide I bands (e.g. at 1660 cm⁻¹ in the Raman spectrum). The presence of two bands for the carboxylic acid CO stretching modes in the solid‐state Raman spectrum can be accounted for by factor group splitting of the two nonequivalent molecules in a crystallographic unit cell. The cis amide II band is observed at 1489 cm⁻¹ in the solid‐state Raman spectrum, which is in agreement with results for cyclic di‐amino acid peptide molecules examined previously in the solid state, where the DKP ring adopts a boat conformation. Additionally, it also appears that as the molecular mass of the substituent on the C^α atom is increased, the amide II band wavenumber decreases to below 1500 cm⁻¹; this may be a consequence of increased strain on the DKP ring. The cis amide II Raman band is characterized by its relatively small deuterium shift (29 cm⁻¹), which indicates that this band has a smaller N H bending contribution than the trans amide II vibrational band observed for linear peptides. Copyright © 2009 John Wiley & Sons, Ltd.     

Optical spectroscopy on Se clusters and chains confined in zeolites

The incorporation of selenium into the supercages of zeolite Y leads to the formation of Se ₈ rings and distorted Se chains in a ratio which is influenced by the nature of the zeolitic cations. Here we review Raman (including resonance Raman) and UV/vis absorption spectroscopy results on Se encapsulated into a number of cation-exchanged faujasite zeolites. Both rings and chains give rise to characteristic Raman bands. In particular, low-frequency Raman bands are attributed to localized vibrations in ordered segments of distorted chains. The UV/vis absorption spectra indicate an opening of the band gap of selenium upon confinement in these zeolites. This can be reversed through electronic interaction with zeolite cations.Received: 1 January 2003, Published online: 14 October 2003PACS: 78.30.-j Infrared and Raman spectra - 82.75.Mj Measurements and simulation of properties (optical, structural) of molecules in zeolites     

On the correlation between the X‐ray absorption chemical shift and the formal valence state in mixed‐valence manganites

Here the correlation between the chemical shift in X‐ray absorption spectroscopy, the geometrical structure and the formal valence state of the Mn atom in mixed‐valence manganites are discussed. It is shown that this empirical correlation can be reliably used to determine the formal valence of Mn, using either X‐ray absorption spectroscopy or resonant X‐ray scattering techniques. The difficulties in obtaining a reliable comparison between experimental XANES spectra and theoretical simulations on an absolute energy scale are revealed. It is concluded that the contributions from the electronic occupation and the local structure to the XANES spectra cannot be separated either experimentally or theoretically. In this way the geometrical and electronic structure of the Mn atom in mixed‐valence manganites cannot be described as a bimodal distribution of the formal integer Mn³⁺ and Mn⁴⁺ valence states corresponding to the undoped references.     

Resonance Raman and electronic absorption study of free‐base tetraphenylporphine diacid dispersed in polymethylcyanoacrylate

We report a resonance Raman study on free‐base tetraphenylporphine (H₂TPP) and its chemically prepared diacid dispersed in polymethylcyanoacrylate (PMCA). Photoexcitation of the neutral porphine by laser light leads irreversibly to the formation of the diacid, with the π‐cation radical as intermediate species. Resonance Raman (RR) spectra of the diacid dispersed in the polymer obtained with 441.6 nm in the wavenumber region of 100–1650 cm⁻¹ are recorded. Wavenumbers with other excitation lines are also reported for the diacid species. Some bands assigned to out‐of‐plane vibrational modes and forbidden under ideal D_2h symmetry are also observed in the resonance Raman spectra of the diacid. These bands arise from the out‐of‐plane distortions, which reduce the symmetry of the molecule. These findings are supported by the electronic absorption studies of the diacid in the polymer. Copyright © 2007 John Wiley & Sons, Ltd.     

IR/Raman spectroscopy and DFT calculations of cyclic di‐amino acid peptides. Part III: comparison of solid state and solution structures of cyclo(L‐Ser‐L‐Ser)

B3‐LYP/cc‐pVDZ calculations of the gas‐phase structure and vibrational spectra of the isolated molecule cyclo(L ‐Ser‐L ‐Ser), a cyclic di‐amino acid peptide (CDAP), were carried out by assuming C₂ symmetry. It is predicted that the minimum‐energy structure is a boat conformation for the diketopiperazine (DKP) ring with both L ‐seryl side chains being folded slightly above the ring. An additional structure of higher energy (15.16 kJ mol⁻¹) has been calculated for a DKP ring with a planar geometry, although in this case two fundamental vibrations have been calculated with imaginary wavenumbers. The reported X‐ray crystallographic structure of cyclo(L ‐Ser‐L ‐Ser), shows that the DKP ring displays a near‐planar conformation, with both the two L ‐seryl side chains being folded above the ring. It is hypothesized that the crystal packing forces constrain the DKP ring in a planar conformation and it is probable that the lower energy boat conformation may prevail in the aqueous environment. Raman scattering and Fourier‐transform infrared (FT‐IR) spectra of solid state and aqueous solution samples of cyclo(L ‐Ser‐L ‐Ser) are reported and discussed. Vibrational band assignments have been made on the basis of comparisons with the calculated vibrational spectra and band wavenumber shifts upon deuteration of labile protons. The experimental Raman and IR results for solid‐state samples show characteristic amide I vibrations which are split (Raman: 1661 and 1687 cm⁻¹, IR: 1666 and 1680 cm⁻¹), possibly due to interactions between molecules in a crystallographic unit cell. The cis amide I band is differentiated by its deuterium shift of ∼30 cm⁻¹, which is larger than that previously reported for trans amide I deuterium shifts. A cis amide II mode has been assigned to a Raman band located at 1520 cm⁻¹. The occurrence of this cis amide II mode at a wavenumber above 1500 cm⁻¹ concurs with results of previously examined CDAP molecules with low molecular weight substituents on the C^α atoms, and is also indicative of a relatively unstrained DKP ring. Copyright © 2009 John Wiley & Sons, Ltd.     

Some CNDO Calculations and Structural Spectroscopic Studies of Paracetamol Complexes

Through complete neglect of differential overlap (CNDO) calculations of the electronic energy among different possible structures of paracetamol (PA) molecule, it has been concluded that its structure has C_s point group symmetry of the cis‐form in which the methyl group has a restricted free rotation around its bond with the carbon atom of the amide group. The electronic spectra of PA compound were studied in different polar and nonpolar solvents. The temperature effect on the electronic spectra confirms the presence of one conformer only. The hydrogen bonding and the orientation energies of the polar solvents were determined from the studies of mixed solvents. Complexes of PA with metal ions M(II) (Cu⁺⁺, Zn⁺⁺, or Fe⁺⁺) of ratio 2:1, respectively, were prepared, and their structure has been confirmed by elemental analysis, atomic absorption spectra, IR spectra, and ¹H‐NMR spectra. It has been concluded that the structure of the complexes has C_2h point group symmetry in which two PA molecules are chelated to any one of the metal ions Cu⁺⁺, Zn⁺⁺, and Fe⁺⁺.     

Molecular structure,NMR and vibrational spectral analysis of 2,4‐difluorophenol by ab initio HF and density functional theory

Quantum chemical calculations of energies, geometries and vibrational wavenumbers of 2,4‐difluorophenol (2,4‐DFP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6‐311G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with related molecules. The best level of theory in order to reproduce the experimental wavenumbers is the B3LYP method with the 6‐311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of 2,4‐DFP is also reported. The entropy of the title compound was also performed at HF/6‐311G(d,p) and B3LYP/6‐311G(d,p) levels of theory. The isotropic chemical shift computed by ¹H, ¹³C NMR analyses also shows good agreement with experimental observations. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule have been constructed. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectra and crystal structure of the di‐amino acid peptide cyclo(L‐Met‐L‐Met): comparison of experimental data and DFT calculations

Experimental Raman and FT‐IR spectra of solid‐state non‐deuterated and N‐deuterated samples of cyclo(L ‐Met‐L ‐Met) are reported and discussed. The Raman and FT‐IR results show characteristic amide I vibrations (Raman: 1649 cm⁻¹, infrared: 1675 cm⁻¹) for molecules exhibiting a cis amide conformation. A Raman band, assigned to the cis amide II vibrational mode, is observed at ∼1493 cm⁻¹ but no IR band is observed in this region. Cyclo(L ‐Met‐L ‐Met) crystallises in the triclinic space group P1 with one molecule per unit cell. The overall shape of the diketopiperazine (DKP) ring displays a (slightly distorted) boat conformation. The crystal packing employs two strong hydrogen bonds, which traverse the entire crystal via translational repeats. B3‐LYP/cc‐pVDZ calculations of the structure of the molecule predict a boat conformation for the DKP ring, in agreement with the experimentally determined X‐ray structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecular structure,vibrational spectroscopic,first‐order hyperpolarizability and HOMO,LUMO studies of 3‐hydroxy‐2‐naphthoic acid hydrazide

The Fourier‐transform infrared spectrum of 3‐hydroxy‐2‐naphthoic acid hydrazide (3H2NAH) was recorded in the region 4000–400 cm⁻¹. The Fourier‐transform Raman spectrum of 3H2NAH was also recorded in the region 3500–10 cm⁻¹. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 3H2NAH were carried out by density functional theory (DFT/B3LYP) method with 6‐31G(d,p) as basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The values of the electric dipole moment (µ) and the first‐order hyperpolarizability (β) of the investigated molecule were computed using ab initio quantum mechanical calculations. The UV spectrum was measured in ethanol solution. The calculation results also show that the 3H2NAH molecule might have microscopic nonlinear optical (NLO) behavior with non‐zero values. A detailed interpretation of the infrared and Raman spectra of 3H2NAH is also reported based on total energy distribution (TED). The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The theoretical FT‐IR and FT‐Raman spectra for the title molecule have also been constructed. Copyright © 2009 John Wiley & Sons, Ltd.