Theoretical study of the vibrational spectra of the hydrogen-bonded systems between pyridine-3-carboxamide (nicotinamide) and DMSO

The vibrational characteristics (vibrational frequencies and infrared intensities) for the hydrogen-bonded systems of nicotinamide (NA(Z) and NA(E)) with dimethyl sulfoxide (DMSO) have been predicted using ab initio SCF/6-31G(d,p) and DFT (BLYP/6-311++G(d,p)) calculations. The changes in the vibrational characteristics from free monomers to a complex have been calculated. The ab initio and BLYP calculations show that the complexation between nicotinamide (NA(Z) and NA(E)) and DMSO leads to large red shifts of the stretching vibrations for the hydrogen-bonded N-H bonds of nicotinamide and very strong increase in their IR intensity. The results from the BLYP/6-311++G(d,p) calculations show that the predicted red shifts of the nu(s)(NH) and nu(as)(NH) vibrations for the complex NA(E)-DMSO (1:2) (Deltanu(as)(NH)=-186 cm(-1) and Deltanu(s)(NH)=-198 cm(-1)) are in better agreement with the experimentally measured. The magnitudes of the wavenumber shifts are indicative of strong NH...O hydrogen-bonded interactions in both complexes. The calculations predict an increase of the IR intensity of nu(s)(NH) and nu(as)(NH) vibrations in the complexes up to 14 times. Having in mind that in more cases the predicted changes in the vibrational characteristics for the complexes studied are very near, it could be concluded that both conformers of nicotinamide, Z-conformer and E-conformer, are present in the solution forming the hydrogen-bonded complexes with DMSO.     

Spectral investigations of preferential solvation and solute-solvent interactions of 1,4-dimethylamino anthraquinone in CH2Cl2/C2H5OH mixtures

The optical absorption and IR spectra of 1,4-dimethylamino anthraquinone (1,4-DMAAQ) in CH(2)Cl(2)/C(2)H(5)OH mixtures have been investigated. The preferential solvation of 1,4-DMAAQ in CH(2)Cl(2)/C(2)H(5)OH mixed solvents has been studied by monitoring the charge transfer band of 1,4-DMAAQ. The optical absorption spectral study indicates that 1,4-DMAAQ is preferentially solvated by CH(2)Cl(2) in CH(2)Cl(2)/C(2)H(5)OH mixtures. This can be confirmed by the observed index of preferential solvation value (delta(s1)) as well as higher mole fraction of CH(2)Cl(2) in the solvation microsphere (x(1)(L)) than in the bulk solvent (x(1)). The CH(2)Cl(2) molecules become more available to enter the solvation shell of 1,4-DMAAQ because of the hydrogen bonded clusters formed by ethanol molecules. This is also evident from the non-linear behavior of the transition energy (E(12)) as well as the absence of synergistic behavior. IR spectral studies show that the observed shifts in the nu(CO) and nu(NH) of 1,4-DMAAQ are due to the dipole-dipole interaction between the 1,4-DMAAQ and the associated ethanol.     

Infrared action spectroscopy and dissociation dynamics of the HOOO radical

The HOOO radical has long been postulated to be an important intermediate in atmospherically relevant reactions and was recently deemed a significant sink for OH radicals in the tropopause region. In the present experiments, HOOO radicals are generated in a pulsed supersonic expansion by the association of O(2) and photolytically generated OH radicals, and the spectral signature and vibrational predissociation dynamics are investigated via IR action spectroscopy, an IR-UV double resonance technique. Rotationally resolved IR action spectra are obtained for trans-HOOO in the fundamental (nu(OH)) and overtone (2nu(OH)) OH stretching regions at 3569.30 and 6974.18 cm(-1), respectively. The IR spectra exhibit homogeneous line broadening, characteristic of a approximately 26-ps lifetime, which is attributed to intramolecular vibrational redistribution and/or predissociation to OH and O2 products. In addition, an unstructured feature is observed in both the OH fundamental and overtone regions of HOOO, which is likely due to cis-HOOO. The nascent OH X(2)Pi, v = 0 or v = 1, products following vibrational predissociation of HOOO, nu(OH) or 2nu(OH), respectively, have been investigated using saturated laser-induced fluorescence measurements. A distinct preference for population of Pi(A') Lambda-doublets in OH was observed and is indicative of a planar dissociation of trans-HOOO in which the symmetry of the bonding orbital is maintained.     

A short hydrogen bond investigation by polarized Raman spectra of Co2+ and Zn2+ salts of pyromellitic acid

Cobalt and zinc salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C(6)H(2)(COO)(4)H(4)], have been synthesized and investigate by polarized Raman spectroscopy. These compounds present short intramolecular hydrogen bonds (SHB) between adjacent carboxyl groups. Raman spectra indicate the presence of this interaction in both salts. Three specific vibrational of SHB modes have been investigated: O-H-O symmetric [nu(sym)(OHO)] and asymmetric [nu(asym)(OHO)] stretching modes and O-H stretching mode [nu(O-H)], which they were observed around 300, 850 and 2500 cm(-1), respectively. In crystallographic point of view, the cobalt salt presents a symmetric SHB while the zinc salt presents an asymmetric SHB. In cobalt salt all three vibrational modes of O-H-O groups in polarized Raman spectra occur in A(g) orientation although in zinc salts two of them are observed in A(g) orientation and one in B(g). Spectra analysis indicate that nu(sym)(OHO) mode is observed as A(g) to cobalt salt and B(g) to zinc salt. This mode occurs in a crowded spectral region and its identification was made by deconvolution techniques. Comparing spectra of the two salts, it is observed a small difference in relative intensity and wavenumber shift of nu(sym)(OHO) (deviance of 43 cm(-1)) and nu(OH) (deviance of 21 cm(-1)) modes due probably to differences in O...O distance between salts and in orientation of pyromellitate anion in unit cell. The nu(asym)(OHO) mode does not present significant wavenumber shift due difference in SHB. The nu(OH) band presents a great potential for hydrogen bond studies due to the fact that in its vibrational region (around 2500 cm(-1)) it is not observed other vibrational modes of these compounds.     

The interaction of formohydroxamic acid with carbon monoxide: FTIR matrix isolation and quantum chemistry studies

Argon matrix infrared spectra of the complexes formed between formohydroxamic acid (HCONHOH) and carbon monoxide have been recorded. The experimental results indicate formation of three isomeric complexes. In two complexes the NH or OH groups of formohydroxamic acid are attached to the carbon atom of the CO molecule and in the third complex the NH group interacts with the oxygen atom of CO. The formohydroxamic acid complex with two CO molecules is also trapped in the matrix. One of the two CO molecules interacts with the NH group and the second one with the OH group of HCONHOH, in both cases the site of interaction is the carbon atom of CO. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the DFT(B3LYP)/6-311++G(2d,2p) level. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data. The calculations show also an additional potential energy minimum corresponding to the complex in which the OH group of formohydroxamic acid is attached to the oxygen atom of carbon monoxide.     

Infrared spectroscopic study of the carbon dioxide adsorption on the surface of Ga2O3 polymorphs

The adsorption of CO(2) over a set of gallium (III) oxide polymorphs with different crystallographic phases (alpha, beta, and gamma) and surface areas (12-105 m(2) g(-1)) was studied by in situ infrared spectroscopy. On the bare surface of the activated gallias (i.e., partially dehydroxylated under O(2) and D(2) (H(2)) at 723 K), several IR signals of the O-D (O-H) stretching mode were assigned to mono-, di- and tricoordinated OD (OH) groups bonded to gallium cations in tetrahedral and/or octahedral positions. After exposing the surface of the polymorphs to CO(2) at 323 K, a variety of (bi)carbonate species emerged. The more basic hydroxyl groups were able to react with CO(2), to yield two types of bicarbonate species: mono- (m-) and bidentate (b-) [nu(as)(CO(3)) = 1630 cm(-1); nu(s)(CO(3)) = 1431 or 1455 cm(-1) (for m- or b-); delta(OH) = 1225 cm(-1)]. Together with the bicarbonate groups, IR bands assigned to carboxylate [nu(as)(CO(2)) = 1750 cm(-1); nu(s)(CO(2)) = 1170 cm(-1)], bridge carbonate [nu(as)(CO(3)) = 1680 cm(-1); nu(s)(CO(3)) = 1280 cm(-1)], bidentate carbonate [nu(as)(CO(3)) = 1587 cm(-1); nu(s)(CO(3)) = 1325 cm(-1)], and polydentate carbonate [nu(as)(CO(3)) = 1460 cm(-1); nu(s)(CO(3)) = 1406 cm(-1)] species developed, up to approximately 600 Torr of CO(2). However, only the bi- and polydentate carbonate groups still remained on the surface upon outgassing the samples at 323 K. The total amount of adsorbed CO(2), measured by volumetric adsorption (323 K), was approximately 2.0 micromol m(-2) over any of the polymorphs, congruent with an integrated absorbance of (bi)carbonate species proportional to the surface area of the materials. Upon heating under flowing CO(2) (760 Torr), most of the (bi)carbonate species vanished a T > 550 K, but polydentate groups remained on the surface up to the highest temperature used (723 K). A thorough discussion of the more probable surface sites involved in the adsorption of CO(2) is made.     

Evidence of CO(2) molecule acting as an electron acceptor on a nanoporous metal-organic-framework MIL-53 or Cr(3+)(OH)(O(2)C-C(6)H(4)-CO(2))

The adsorption mode of CO(2) at low coverage in the nanoporous metal benzenedicarboxylate MIL-53(Cr) or Cr(3+)(OH)(O(2)C-C(6)H(4)-CO(2)) has been identified using IR spectroscopy; the red shift of the nu(3) band and the splitting of the nu(2) mode of CO(2) in addition to the shifts of the nu(OH) and delta(OH) bands of the MIL-53(Cr) hydroxyl groups provide evidence that CO(2) interacts with the oxygen atoms of framework OH groups as an electron-acceptor via its carbon atom; this is the first example of such an interaction between CO(2) and bridged OH groups in a solid.     

Comprehensive investigation of vibrational relaxation of non-hydrogen-bonded water molecules in liquids

The vibrational dynamics of isolated water molecules dissolved in the nonpolar organic liquids 1,2-dichloroethane (C(2)H(4)Cl(2)) and d-chloroform (CDCl(3)) have been studied using an IR pump-probe experiment with approximately 2 ps time resolution. Analyzing transient, time, and spectrally resolved data in both the OH bending and the OH stretching region, the anharmonic constants of the bending overtone (v=2) and the bend-stretch combination modes were obtained. Based on this knowledge, the relaxation pathways of single water molecules were disentangled comprehensively, proving that the vibrational energy of H(2)O molecules is relaxing following the scheme OH stretch-->OH bend overtone-->OH bend-->ground state. A lifetime of 4.8+/-0.4 ps is determined for the OH bending mode of H(2)O in 1,2-dichloroethane. For H(2)O in CDCl(3) a numerical analysis based on rate equations suggests a bending overtone lifetime of tau(020)=13+/-5 ps. The work also shows that full 2-dimensional (pump-probe) spectral resolution with access to all vibrational modes of a molecule is required for the comprehensive analysis of vibrational energy relaxation in liquids.     

Quantum tunneling in the midrange vibrational fundamentals of tropolone

The Fourier transform infrared spectrum of tropolone(OH) vapor in the 1175-1700 cm(-1) region is reported at 0.0025 and 0.10 cm(-1) spectral resolutions. The 12 vibrational fundamentals in this region of rapidly rising vibrational state density are dominated by mixtures of the CC, CO, CCH, and COH internal coordinates. Estimates based on the measurement of sharp Q branch peaks are reported for 11 of the spectral doublet component separations DS(v) = |Delta(v) +/- Delta(0)|. Delta(0) = 0.974 cm(-1) is the known zero-point splitting, and three a(1) modes show tunneling splittings Delta(v) approximately Delta(0), four b(2) modes show splittings Delta(v) approximately 0.90Delta(0), and the remaining four modes show splittings Delta(v) falling 5-14% from Delta(0.) Significantly, the splitting for the nominal COH bending mode nu(8) (a(1)) is small, that is, 10% from Delta(0). Many of the vibrational excited states demonstrate strong anharmonic behavior, but there are only mild perturbations on the tautomerization mechanism driving Delta(0). The data suggest, especially for the higher frequency a(1) fundamentals, the onset of selective intramolecular vibrational energy redistribution processes that are fast on the time scale of the tautomerization process. These appear to delocalize and smooth out the topographical modifications of the zero-point potential energy surface that are anticipated to follow absorption of the nu(v) photon. Further, the spectra show the propensity for the Delta(v) splittings of b(2) and other complex vibrations to be damped relative to Delta(0).     

Synthesis and structure investigation of the antibiotic amoxicillin complexes of d-block elements

The study of some transition metals (M) and amoxicillin trihydrate (ACT) ligand complexes (M-ACT) that formed in solution involved the spectrophotometric determination of stoichiometric ratios and their stability constants and these ratios were found to be M:ACT = 1:1, 1:2 and 2:1 in some instances. The calculated stability constants of these chelates, under selected optimum conditions, using molar ratio method have values ranging from K(f) = 10(7) to 10(14). These data were confirmed by calculations of their free energy of formation deltaG, which corresponded to their high stabilities. The separated solid complexes were studied using elemental analyses, IR, reflectance spectra, magnetic measurements, mass spectra and thermal analyses (TGA and DTA). The proposed general formulae of these complexes were found to be ML(H2O)w(H2O)x(OH)y(Cl)2, where M = Fe(II), Co(III), w = 0, x = 2, y = 1, z = 0; M = Co(II), w = 0, x = 1, y = 0, z = 1; M = Fe(III), w = 0, x = 1, y = 2, z = 0; M = Ni(II), Cu(II) and Zn(II), w = 2, x = 0, y = 1, z = 0, where w = water of crystallization, x = coordinated water, y = coordinated OH(-) and z = Cl- in the outer sphere of the complex. The IR spectra show a shift of nu(NH) (2968 cm(-1)) to 2984-2999 cm(-1) of imino group of the ligand ACT and the absence of nu(CO) (beta-lactame) band at 1774 cm(-1) and the appearance of the band at 1605-1523 cm(-1) in all complexes suggest that 6,7-enolization takes place before coordination of the ligand to the metal ions. The bands of M-N (at 625-520 cm(-1)) and of M-O (at 889-7550 cm(-1)) proved the bond of N (of amino and imino groups) and O of C-O group of the ligand to the metal ions. The reflectance spectra and room temperature magnetic measurements refer to octahedral complexes of Fe(II) and Fe(III); square planner form of Co(II), reduced Co(III), Ni(II) and Cu(II)-ACT complexes but tetrahedral form of Zn-ACT complex. The thermal degradation of these complexes is confirmed by their mass spectral fragmentation. These data confirmed the proposed structural and general formulae of these complexes.     

Revealing anharmonic couplings and energy relaxation in DNA oligomers by ultrafast infrared spectroscopy

The identification and characterization of NH 2 hydrogen-bonded stretching vibrations [nu(NH 2)] in DNA oligomers is usually hampered by the all-dominating absorption of the water stretching band in the spectral range of 3050-3600 cm(-1). Here, we use the two-color IR pump-probe technique to overcome the limitations of linear absorption spectroscopy by exciting adenine-thymine (A-T) oligomer vibrations in the fingerprint region and analyzing induced transient spectral changes in the nu(NH2) spectral region. These transient changes are related to anharmonic couplings to the modes excited in the fingerprint region and to modes populated by intra- and intermolecular energy redistribution and relaxation. The combination of calculated anharmonic coupling parameters and experimental transient IR data allows the assignment of a transition at 3215 cm(-1) to the nu(NH2) vibration of adenine in dA(20)-dT(20) DNA oligomers.     

Infrared absorption spectra of vinyl radicals isolated in solid Ne

Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.6, 2911.5, 1357.4, 677.1, 895.3, and 857.0 cm(-1). These features are assigned to alpha-CH stretching (nu(1)), CH(2) antisymmetric stretching (nu(2)), CH(2) symmetric stretching (nu(3)), CH(2)-bending (nu(5)), HCCH cis bending (nu(7)), CH(2) out-of-plane bending (nu(8)), and alpha-CH out-of-plane bending (nu(9)) modes of C(2)H(3), respectively, based on results of (13)C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP and PW91PW91/aug-cc-pVTZ) predict vibrational wavenumbers, IR intensities, and isotopic ratios of vinyl radical that agree satisfactorily with our experimental results.     

Substituent effects on benzdiyne: a density functional theory study

Density functional theory (DFT) studies were performed to investigate the effect of substituents on the properties of benzdiyne derivatives. Twelve substituted benzdiynes-C(6)X(2), where X = F, Cl, Br, Me, CF(3), CN, OH, NO(2), NH(2), OMe, NMe(2), and Ph-were considered along with the unsubstituted 1,4-benzdiyne. The structures, vibrational frequencies, and IR intensities of these benzdiynes were studied with a popular three-parameter hybrid density functional (B3LYP) combined with the split-valence 6-31G(d) basis set and Dunning's correlation-consistent polarized triple-zeta (cc-pVTZ) basis set. The relative stabilities of the substituted benzdiynes were studied with the help of reaction energies of isodesmic reactions, which showed that the electron-withdrawing groups destabilized the benzdiynes more than they did the corresponding benzenes, whereas the electron-donating groups stabilized the benzdiynes more than they did their benzene counterparts. Correlation analyses revealed that field/inductive effects played a more important role than did resonance effects. The changes in atomic charges and spin populations due to the substituents were also studied. The asymmetric nu(Ctbd1;C) stretching modes obtained were close to the 1500-cm(-)(1) mark. Reinvestigation of the experimental results supported these results; a weak IR band at 1486 cm(-)(1) was assigned to this asymmetric stretching mode in C(6)(CF(3))(2) F. Some other benzdiynes also had large IR intensity values for their asymmetric nu(Ctbd1;C) vibrational modes due to the coupling with other vibrational modes. Heats of formation for the substituted benzdiynes were obtained from the reaction energies calculated at the B3LYP/cc-pVTZ level of theory.     

Investigation of nu(N-H) and nu(C-N) stretching modes of propylamine (C3H7NH2) in a binary system C3H7NH2 + CH3OH via concentration dependent Raman study and ab initio calculations

Raman spectra of propylamine (C3H7NH2) and its binary mixtures, C3H7NH2 + CH3OH with varying mole fractions of the reference system, C3H7NH2, C were recorded in two widely apart wavenumber regions, 3100-3600 cm(-1) and 1225-1325 cm(-1). In the former region, the two Raman bands at approximately 3305 and approximately 3326 cm(-1), obtained after the line shape analysis, which were assigned to symmetric nu(N-H) and anti-symmetric nu(N-H) stretching modes, respectively, show a downshift upon dilution. However, whereas the nu(N-H) anti-symmetric mode shows a shift of 18.6 cm(-1), the nu(N-H) symmetric mode shows a much smaller shift (5.7 cm(-1)) between neat liquid and high dilution, C = 0.1. This aspect has been explained using the optimized geometries calculated employing ab initio theory (MP2 level) for the neat C3H7NH2 and its different hydrogen-bonded complexes. The linewidth versus concentration plot for the nu(N-H) anti-symmetric stretching mode, however exhibits a distinct maxima at C = 0.4, which has been explained as a slight departure from the concentration fluctuation model. In the latter region, a symmetric peak is observed, which corresponds to nu(C-N) stretching mode, which shows an upshift upon dilution and an almost linear concentration dependence. This has also been explained in terms of the parameters obtained from the optimized geometries of the different hydrogen-bonded complexes.     

Mapping the OH + CO-->HOCO reaction pathway through IR spectroscopy of the OH-CO reactant complex

A hydrogen-bonded complex composed of the OH and CO reactants has been identified along the OH + CO-->HOCO reaction pathway. IR action spectroscopy in the OH overtone region has been used to examine the vibrational modes of the linear OH-CO complex, including intermolecular bending modes that probe portions of the reaction path leading to HOCO. The spectroscopic measurements have accessed highly excited intermolecular levels, with energies up to 250 cm-1 above the zero-point level, which lie in close proximity to the transition state for reaction. The OH-CO binding energy, D0 < or = 430 cm-1, has also been established from the quantum state distribution of the OH fragments following vibrational predissociation of the OH-CO complex. Complementary electronic structure calculations have been performed to characterize the OH-CO and OH-OC complexes, the transition state for HOCO formation, and the direct reaction path that connects the experimentally observed OH-CO complex to the HOCO intermediate.     

Spectral and magnetic properties of phenylazo-6-aminouracil complexes

Complexes of Co(II), Ni(II) and Cu(II) with substituted phenylazo-6-aminouracils containing (-H, p-OH, p-CH(3), p-OCH(3) p-COOH) have been synthesized and characterized by elemental analysis, magnetic measurements and spectral measurements (IR, UV-Vis, ESR). Infrared spectra assigned the fundamental bands of the major groups, O-H, N-H, C-H, C=O, C=N, N=N, C-N and C-O (nu, delta and gamma modes of vibrations). The absence of nu(OH) and the appearance of nu(C=O) in the infrared spectra of the free ligands of 5-(p-tolyl and p-anisylazo)-6-aminouracil, assigned the keto structure, whereas in cases of 5-(phenyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracil ligands, the data showed strong nu(OH) and nu(C=O) bands to assign keto-enol tautomerisms. The modes of interactions between the ligands and the metals were discussed, where oxygen and nitrogen atoms (of amino-amide groups) are involved in chelation. The azo group was not involved in chelation for all the prepared complexes except those of copper complexes derived from 5-(phenyl, p-tolyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracils. The room temperature effective magnetic moment values, the Nujol mull spectra and ESR proved that all the prepared complexes were of octahedral geometry, except the nickel complex derived from 5-(phenylazo)-6-aminouracil and cobalt complex derived from 5-(p-carboxy-phenylazo)-6-aminouracil were square planar.     

Vibrational overtone spectroscopy of jet-cooled methanol from 5000 to 14 000 cm(-1)

Spectra of jet-cooled methanol in the overtone and combination region from 5000 to 14 000 cm(-1) have been obtained by means of infrared laser-assisted photofragment spectroscopy. Many of the observed features are assigned to combination bands of the type nnu(1)+nu(6), nnu(1)+nu(8), and nnu(1)+nu(6)+nu(8) (n=1,2,3), where nu(1) is the OH stretch, nu(6) is the OH bend, and nu(8) is the CO stretch. These bands show sharp torsion-rotation structure with features as narrow as 0.1 cm(-1). We also observe CH stretch overtones that are weaker than the OH containing combination bands and lack distinct torsion-rotation structure above v(CH)=2. The extent of observed structure on these bands allows us to place limits on the intramolecular vibrational energy redistribution decay rates in the upper vibrational states. We report a global fit of the observed band centers to a simple expression involving low-order anharmonicity constants.     

Infrared spectra and intensities of the H2O and N2 complexes in the range of the nu1- and nu3-bands of water

The IR spectra of complexes of water with nitrogen molecules in the range of the symmetric (nu(1)) and antisymmetric (nu(3)) bands of H(2)O have been studied in helium droplets. The infrared intensities of the nu(3) and nu(1) modes of H(2)O were found to be larger by factors of 1.3 and 2, respectively, in the N(2)-H(2)O complexes. These factors are smaller than those obtained in recent theoretical calculations. The conformation of the N(2)-H(2)O complex was estimated. Spectra and IR intensities of the (N(2))(2)-H(2)O and N(2)-(H(2)O)(2) complexes were also obtained and their structures are discussed.     

Comparative study of the hydrogen-bonded complexes of phenol and o-cyanophenol with CO Ab initio and DFT approachs

The structures, stability and vibrational spectra of the hydrogen-bonded complexes of carbon monoxide (CO) with phenol and o-cyanophenol (syn and anti) have been studied using ab initio and DFT calculations. Full geometry optimization has been performed for the studied complexes by DFT (BLYP/6-311++G(d,p)) calculations. The calculations show that the hydrogen-bond formation of carbon monoxide (CO) with phenol and o-cyanophenol (syn and anti) leads to the following stable structures: C6H5OH...CO (1A); C6H5OH...OC (1B); (syn) o-CNC6H4OH...CO (2A-syn); (syn) o-CNC6H4OH...OC (2B-syn); (anti) o-CNC6H4 OH...CO (2A-anti) and (anti) o-CNC6H4OH...OC (2B-anti). Having in mind the corrected values of the dissociation energy, the studied hydrogen-bonded complexes can be ordered according their stability as follows: 2A-anti>2A-syn>1A>2B-anti>1B>2B-syn. The predicted red-shifts for the nuOH vibration with the B3LYP/6-311++G(d,p) calculations for the structures 1A (-46 cm-1), 2A-syn (-60 cm-1) and 2A-anti (-73 cm-1) are in very good agreement with the experimentally observed. The magnitudes of the wavenumber shifts are indicative of relatively weak OH...C hydrogen-bonded interactions. The calculations predict an increase of the IR intensity of the nuOH vibration in the complexes 1A, 2A-anti and 2A-syn up to five times.