Wavenumbers Of Stretching Vibrations Research Articles

Application of Quantum–Chemical Methods in the Forensic Prediction of Psychedelic Drugs’ Spectra (IR, NMR, UV–VIS, and MS): A Case Study of LSD and Its Analogs

Lysergic acid diethylamide (LSD) and its analogs are commonly encountered substances at crime scenes due to their misuse as hallucinogenic compounds. Modern methods have led to synthesizing different LSD analogs with pronounced physiological effects. Theoretical methods can be a valuable tool for predicting the spectra and stability of novel substances, especially when experimental data are partially available. The current work describes the application of theoretical methods in predicting IR, NMR, UV–VIS, and MS spectra of LSD based on the optimized structure at the M05-2X/6-311++G(d,p) level of theory. A suitable functional has been determined by comparison of the theoretically obtained geometrical parameters with the experimental ones based on the crystallographic structure. The MAE values for the structure optimized at M05-2X/6-311++G(d,p) level of theory were 0.0436 Å (bond lengths) and 2.70° (bond angles). The IR spectra of LSD and LSD tartrate have been described in detail, with the prominent bands being well reproduced (the difference between experimental and theoretical C=O stretching vibration wavenumbers was lower than 11 cm−1). Detailed assignment of 13C NMR spectra led to a high correlation factor (0.999) and low mean absolute error (2.0 ppm) between experimental and theoretical chemical shifts. Optimizing the ground and excited states allowed for the calculation of the energy difference of 330 nm, which reproduced the observed band position in the UV–VIS spectrum of LSD. The most abundant fragments in the experimental mass spectrum (at 323, 221, 207, 181, and 72 m/z) have been optimized, and their stability has been discussed from the structural point of view. This methodology has been validated by comparison with the experimental GC-MS spectra of sample seized at the crime screen and by structure optimization and computation of NMR spectra of common LSD analogs. The theoretical methods for the structure determination and prediction of spectra show great potential in the fast-developing world of new psychedelics.

Raman spectroscopy and ab initio quantum chemical calculations of ion association behavior in calcium nitrate solution

AbstractIn this work, microscopic Raman spectroscopy and component analysis were used to study a calcium nitrate solution with molar water‐to‐salt ratio (WSR) values of 4–320. The results showed that the symmetrical stretching vibration wavenumber of the nitrate ion (v1‐NO3−) in the solution blue shifted from 1,048 to 1,053 cm−1, and the full width at half maximum increased from 9.7 to 11 cm−1 when the WSR was reduced from 320 to 4. The component analysis of v1‐NO3− showed that the first concentration region was for WSR ≥ 16.3. In this region, solvent‐shared ion pairs (SIPs) were the main species, and contact ion pairs (CIPs) and free‐hydrated ions were the secondary species. For 8.4 ≤ WSR < 16.3, the main species were CIPs; the amount of complex structures in this region increased rapidly, whereas the amount of SIPs decreased rapidly. For WSR < 8.4, the main species were the complex structures, and the amount of CIPs and SIPs dropped rapidly. Ab initio quantum chemical calculations showed that the SIPs in the first concentration range were composed of 2 hexahydrate calcium ions and 1 nitrate ion that formed a shared ion pair, SIP‐SIP. The calcium ions were directly bonded with water molecules, and the nitrate ions formed hydrogen bonds with the water molecules. In the second concentration region, the CIPs were each formed by 2 hydrated calcium ions and 1 nitrate ion via monodentate or bidentate coordination with a CIP‐CIP structure. When the WSR was further reduced, a large number of the complex structures such as Comp5 and Comp6 formed in the solution, which were the complex structures [(H2O)nCa2+(NO3−)Ca2+(H2O)m] clustered by C5 or C6.

Spectroscopic and theoretical studies of dalbergin and Methyldalbergin

Molecular structure and vibrational analysis of methyldalbergin (MDLBG) and dalbergin (DLBG) are presented using vibrational spectroscopy (infrared and Raman) and quantum chemical calculations. Difference in the OH stretching vibration wavenumber of two conformers of DLBG was observed as in one conformer this bond is making an intramolecular H-bond while in other it is free. The spectral calculations, ground state geometry and electronic structure calculations were performed based on the density functional theory (DFT) using the standard B3LYP/6–311++G(d,p) methodology. FT-Raman and FT-IR spectra were recorded in the solid phase, and interpreted in terms of potential energy distribution analysis. The UV–visible absorption spectrum was examined in DMSO solvent and compared with one calculated in gas phase as well as in solvent environment using TD-DFT/6-311G++(d,p) basis set. HOMO-LUMO energy gap results show chemical reactivity of conformers of DLBG and MDLBG.

Self-Assembly and Solid-State Polymerization of Butadiyne Derivatives with Amide and Trialkoxyphenyl Groups

Abstract Three butadiyne derivatives with amide and tri(dodecyloxy)phenyl (TDP) groups were synthesized, and four solidification methods were applied to obtain their self-assembling states in various conditions. The solids obtained were characterized by the solid-state polymerization behaviors, stretching vibration wavenumbers of N–H bonds of amide groups, powder X-ray diffraction, the thermal behaviors, and scanning electron microscope (SEM) observations. We found that all compounds had at least two polymorphs. Property differences between two polymorphs depended on the compounds. Two compounds showed clear differences in UV–vis spectra of the photopolymerized solids, i.e., the polydiacetylene (PDA) structure, and irregularly polymerized form, or two PDA structures. The remaining compound showed the same PDA absorption but the monomer melting points were different. All compounds gave the gels in various organic solvents because of the molecular design with amide and TDP groups. SEM observation clarified the relationship between gel appearance and the nanostructures.

Correlation between the local OH stretching vibration wavenumber and the hydrogen bonding pattern of water in a condensed phase: Quantum chemical approach to analyze the broad OH band

A study of the chemical origin of the broad IR absorption band of the O–H stretching vibration (νOH) of liquid water is mentioned. The study is performed by measuring the local νOH mode of the half-deuterated water (HDO) dissolved in deuterated water (D2O) with an aid of quantum chemical calculation. The band position of a local νOH mode is analyzed as a function of hydrogen (H)-bond coordination pattern, which is taken into account by using a useful index of MOH based on the DA3 pattern method. The DA3 method focuses on a HDO–D2O (donor–accepter; DA) molecular pair, and the hydration about the DA pair is categorized into 36 patterns with respect to the H-bond coordination pattern. The MOH index summarizes the patterns by considering the positive and negative contributions of the hydration to the H-bond in the DA pair. The calculated band position of the H-bonded νOH in the pair is readily grouped by using the MOH index, which can also be used as an index for evaluating H-bonding energy. This paper demonstrates the potential of the DA3 method to analyze the νOH band and H-bonding energy of liquid water and ice by referring to QC calculation results for relatively small water clusters.

A low-temperature IR spectroscopic investigation of the H2O molecules in the zeolite mesolite

IR powder spectra of the zeolite mesolite (Na 16 Ca 16 [Al 48 Si 72 O 240 ]·64H 2 O) were recorded at temperatures between 10 K and 300 K in order to better determine the local behavior of the H 2 O molecules in the channel ways. The low-temperature IR spectra show well-resolved OH stretching vibrations of the H 2 O molecules between 3100 and 3600 cm −1 and bending vibrations between 1500 cm −1 and 1700 cm −1 . Five OH stretching modes are observed at room temperature and eight at 10 K. Three H 2 O bending vibrations were observed at all temperatures. Using published crystal-structural data for mesolite and IR/Raman results on structurally similar natrolite, Na 16 [Al 16 Si 24 O 80 ]·16H 2 O, and scolecite, Ca 8 [Al 16 Si 24 O 80 ]·24H 2 O, a first attempt was made to assign the internal H 2 O stretching and bending modes. The two OH stretching modes originating from H 2 O in the natrolite-like units in mesolite appear to be red-shifted compared to their equivalents in the spectrum of natrolite. This could be due to slightly stronger H-bonding in mesolite. The OH modes related to H 2 O in the scolecite-like units of mesolite appear to show less change in wavenumber compared to their equivalents in the IR spectrum of scolecite. The average OH stretching vibration wavenumbers for natrolite, scolecite and mesolite are approximately similar being around 3420 (±10) cm −1 . This is not far removed from the value of 3400 cm −1 observed for liquid H 2 O, while values for the various polymorphs of ice lie between 3220 and 3250 cm −1 .

Remarkable effect of hydrogen bonding between ring and axle components on deslipping reactions of rotaxanes

A series of rotaxanes 1· 5, 2· 5, 3· 5, and 4· 5 bearing a different substituent (X = NO 2, Br, H, and OMe, respectively) at para position on the phenol moiety of the ring component exhibit clear difference in deslipping behavior. The difference in the deslipping rates is consistent with the difference in intercomponent hydrogen bonding strength estimated from the O–H stretching vibration wavenumbers. The para substituent dictates the relative strength of the intra- and intermolecular hydrogen bonds. Thus the incorporation of an intramolecular hydrogen bond allows for tunability of the strength of the intercomponent interaction.

FTIR spectral studies of methyltestorone in single and binary solvent systems

The studies on the solvent effects of methyltestorone (MT) in 19 different organic solvents and n-C 6H 14/CHCl 3 binary solvents were undertaken by FTIR spectroscopy. The wavenumbers of carbonyl stretching vibration for MT ( ν(C O)) in individual solvents were correlated with the empirical solvent parameters such as Schleyer's linear free energy equation ( G-value), the solvent acceptor number (AN) and the linear solvation energy relationships (LSER), respectively. The solvent-induced carbonyl stretching vibration wavenumber shifts of MT exhibited a better correlation with the LSER than the other solvent parameters. With the increase of the volume fraction of chloroform ( X CHCl3) in the n-C 6H 14/CHCl 3 binary solvents, two kinds of ν(C O) of MT were observed and assigned. The formation constant ( K 0) of the interaction between MT and CHCl 3 and the free energy change (Δ G 0) of the system were calculated in the binary solvents by Nash's method.

FTIR spectroscopy investigation of the crystallisation process in an iron rich glass

The crystallisation behaviour of an iron rich glass, obtained by recycling zinc hydrometallurgy waste, was investigated by FTIR spectroscopy. The transformations occurring in the glass subjected to different thermal cycles, i.e. liquid–liquid separation and crystallisation, were investigated by FTIR, XRD and TEM. The asymmetric Si O Si stretching vibration wave-number, 1016 cm −1 in the FTIR spectrum of the glass, increased with the heat treatment temperature and was related to the variation of the coefficient of thermal expansion and density of the glass-ceramic. The magnetite and pyroxene crystalline phase peak, at 638 cm −1, was utilised for determining the degree of crystallisation of the glass-ceramic by measuring the area of the peak as a function of the thermal treatment time; the results were compared with the same evaluation carried out by density measurements.

Evidence of photoluminescence related to subsurface Si–O–Si bonds in sputtered silicon nanoparticles

We have prepared silicon nanoparticles by depositing the dc sputtered Si material on the cooled surface of a liquid-nitrogen-cooled trap. The photoluminescence in the region of 300–550 nm is found to be independent of the surface chemical structure of the particles. FTIR investigations suggest that the photoluminescence peak is related to the Si–O–Si bonds whose stretching vibration wavenumber is about 1080 cm −1. The results show a definite correspondence between the photoluminescence intensities and the 1080 cm −1 FTIR peaks for the different annealed samples. Moreover, this 1080 cm −1 FTIR vibration species arises not from the surface layer but from the deeper subsurface layer of the particles, which explains why the photoluminescence is stable and fairly independent of the oxidation of the surface Si bonds through aging or annealing in the atmosphere.

Correlation between stretching mode absorptions and asymmetry of the V(O 2) group in peroxo complexes of vanadium (V)

Stretching vibration wavenumbers have been estimated for (NH 4) 2[VO(O 2) 2F] and (NH 4) 3[VO(O 2) 2F 2] based on normal coordinate calculations employing a valence force field derived from bond length—force constant correlations. The results bear out the recently suggested re-assignment of the vanadium—ligand stretching vibrations. The effect of ligands on the asymmetry of the ▪ group is discussed using structural data for 19 vanadium (V) peroxo complexes. The asymmetry of the ▪ group is different in compounds with different coordination numbers. This difference is accompanied by characteristic shifts of the vanadium—peroxo oxygen stretching mode absorptions.

Acid–base properties of silica–alumina samples derived from NaX zeolites. Part 1.—Physical characterization and an infrared study of the adsorption of acetone

Amorphous SiO2/Al2O3 samples have been prepared from NaX zeolite and have been compared with partially ammonium-exchanged NaX zeolites. The specific surfaces and the composition of the oxides have been determined. An increasing TO antisymmetric stretching vibration wavenumber has been found for decreasing Na+ and Al3+ content in the oxide. This is interpreted as being due to an increasing degree of covalency of the cation–oxygen bond and an increasing ‘maximum acceptor strength’. The latter is defined as the electron-pair acceptor strength a fully accessible cation would exhibit towards an electron-pair donor molecule. Adsorption of acetone caused perturbed OH bands, with their wavenumbers decreasing with higher relative content of silica. Zeolitic oxides were able to form highly unsaturated surface species from acetone. All the oxides exhibited weakly bound, perpendicularly adsorbed acetone as well as acetone adsorbed parallel to the surface. This adsorbate is thought to be a precursor of carboxylate formation. Carboxylate groups were only found with one of the acid-treated samples, ASX3.