UV-vis, IR and (1)H NMR spectroscopic studies of some Schiff bases derivatives of 4-aminoantipyrine

Five Schiff bases derived from 4-aminoantipyrine and benzaldehyde derivatives (I) are prepared and their UV-vis, IR, (1)H NMR and fluorescence spectra are investigated and discussed. The electronic absorption spectra of the hydroxy 4-aminoantipyrine Schiff bases Ib and Ie as well as the fluorescence spectra of Ie are studied in the organic solvents of different polarity. The UV-vis absorption spectra of 4-aminoantipyrine Schiff bases Ib, Id and Ie are investigated in aqueous buffer solutions of varying pH and utilized for the determination of pK(a) and DeltaG of the ionization process. The reactions of the hydroxy compounds Ib and Ie with Ni(II) and Cu(II) ions are also studied. The results of spectral studies are supported by some molecular orbital calculations using an atom superposition and electron delocalization molecular orbital theory for a compound Ib.     

Fluorophenylantimony carboxylates(II): synthetic and spectroscopic studies (UV, IR, H, F and C NMR) of pentafluorophenylantimony(V) di- and tetracarboxylates

Pentafluorophenylantimony(V) di- and tetracarboxylates of the molecular formula C₆F₅SbX₂L₂ (when X=L=OCOR (R=CH₃, CH₂Cl, CHCl₂, CCl₃, CF₃, CH₂OC₆H₃Cl₂-2,4, CH₂OC₆H₂Cl₃-2,4,5) and when X=Cl; L=OCOCH_3, OCOCHCl₂) have been synthesized by the metathetical reaction of pentafluorophenylantimony(V) tetrachloride and (dibromide)dichloride with corresponding sodium salt of carboxylic acids in appropriate molar ratio using 15-crown-5 as phase transfer catalyst. The van’t Hoff factor ‘i’ and molar conductance data of the compounds revealed them to be monomeric and non-conducting in nature. Elemental analysis, UV, IR and NMR (¹H, ¹⁹F and ¹³C) were used to characterize the derivatives. Compounds are tentatively assigned as a pentacoordinated square pyramidal structure in which carboxylate ligand behaving as a monodentate ligand.     

UV/Vis,IR and 1H NMR spectroscopic studies of bisazo-dianil compounds based on 5-(2-carboxyphenyl azo)-salicylaldehyde and primary diamines

The electronic absorption and emission spectra of the titled biazo-dianils are studied in organic solvents of different polarity as well as in aqueous buffer solutions of varying pH. The important bands in the IR spectra as well as the main signals of the 1H NMR spectra are assigned. The observed UV/Vis absorption bands are assigned to the corresponding electronic transitions. The fluorescence quantum yield and pK(a)(-) values in the ground and excited states are determined.     

Synthesis, IR, UV/vis-, (1)H NMR and DFT study of chelatophore functionalized 1,3-benzoxazinone spiropyrans

Six novel functionalized spiropyran's derivatives of 2H-1,3-benzoxazinone series were synthesized by introducing the substituents with chelating ability into 2H-chromene part of the 8'-formyl-7'-hydroxy-3-methyl-4-oxo-3,4-dihydro-2H-1,3-benzoxazine-2-spiro-2'-[2H]-chromene (I) by condensation with 2-aminophenol, 2-amino-4-methylphenol, 2-amino-4-nitrophenol, 2-amino-1-methylbenzimidazole, 4-amino-4H-1,2,4-triazole, N-(4-aminophenyl)acetamide. (1)H NMR, UV/vis, IR spectroscopy combined with quantum-chemical calculations employing density functional theory (DFT) were used to study their structure. All substances, except 2-amino-4-nitrophenol derivative exist in solid state and in solution solely in closed spiroform, while the mentioned one undergoes partial spiropyran ring opening. In DMSO solution NMR spectra show ratio of 2:1 of closed and opened form, correspondingly.     

UV-vis, IR and 1H NMR spectroscopic studies of some 6-chloro,2-pyridyl hydrazones

The electronic absorption spectra of some 6-chloro,2-pyridyl hydrazones are studied in seven organic solvents of different polarity. The absorption bands are assigned to the corresponding electronic transitions and the effect of solvent parameters on the charge transfer energy (E(CT)) is investigated. The spectra in buffer solutions of varied pH are also studied and utilized for the determination of the acid dissociation constants of the compounds under study. The fluorescence spectra were recorded for one of the studied compounds in six solvents, the solvent effect on the photoquantum yield and spectral pattern are also studied. Bands of diagnostic importance in the IR spectra and signals in the (1)H NMR spectra are assigned. The results of the present investigation are supported by some MO calculations using the atom super position and electron delocalization molecular orbital theory (ASED-MO) and Gaussian 94 program. The geometry is optimized using the PM3 method.     

Theoretical approach to the molecular structure,chemical reactivity,molecular orbital analysis,spectroscopic properties (IR,UV, NMR), and NBO analysis of deferiprone

In this investigation, the structural, electronic properties, ¹³C and ¹H NMR parameters and the first hyperpolarizability of deferiprone are computed in the gas phase and various solvents at the M062X/6-311++G(d,p) level of theory. The solvent effect on the structural parameters, frontier orbital energies, ¹³C and ¹H NMR parameters is also explored based on a polarizable continuum model. These consequences specify that the polarity of solvents affects the structures and spectroscopic properties of deferiprone. ¹H and ¹³C NMR chemical shifts are evaluated by employing the gauge-invariant atomic orbital method. NBO analysis is exploited to examine the hybridization of atoms, atomic charges, and their second order stabilization energy within the molecule.     

UV/vis, 1H, and 13C NMR spectroscopic studies to determine mangiferin pKa values

The acid constants of mangiferin (a natural xanthonoid) in aqueous solution were determined through an UV/vis spectroscopic study employing the SQUAD program as a computational tool. A NMR study complements the pK(a) values assignment and evidences a H-bridge presence on 1-C. The chemical model used was consistent with the experimental data obtained. The pK(a) values determined with this procedure were as follows: H(4)(MGF)=H(3)(MGF)(-)+H(+), pKa1 (6-H)=6.52+/-0.06; H(3)(MGF)(-)=H(2)(MGF)(2-)+H(+), pKa2 (3-H)=7.97+/-0.06; H(2)(MGF)(2-)=H(MGF)(3-)+H(+), pKa3 (7-H)=9.44+/-0.04; H(MGF)(3-)=(MGF)(4-)+H(+), pKa4 (1-H)=12.10+/-0.01; where it has been considered mangiferin C(19)H(18)O(11) as H(4)(MGF). Mangiferin UV/vis spectral behavior, stability study in aqueous solution as well as NMR spectroscopy studies: one-dimensional (1)H,(13)C, 2D correlated (1)H/(13)C performed by (g)-HSQC and (g)-HMBC methods; are also presented. pK(a) values determination of H(4)(MGF) in aqueous solution is a necessary contribution to subsequent pharmacokinetic study, and a step towards the understanding of its biological effects.     

Investigation of silyl-substituted alkylthioacetates by IR and UV spectroscopy,1H and29Si NMR,and mass spectrometry

Conclusions The IR, UV, NMR, and mass spectra of silyl-substituted alkylthioacetates have been investigated. Intramolecular coordination of the carbonyl group with the silicon atom has been shown to exist in molecules of trifluoroaeetylthiomethylsilane in the condensed state and in a polar solvent (acetonitrile).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2224–2228, October, 1985.     

Reversed-phase chiral HPLC and LC/MS analysis with tris(chloromethylphenylcarbamate) derivatives of cellulose and amylose as chiral stationary phases

Three polysaccharide-derived chiral stationary phases (CSP) were evaluated for the resolution of more than 200 racemic compounds of pharmaceutical interest in the reversed-phase (RP) separation mode. The population of test probes was carefully evaluated in order to insure that it covers as completely as possible all structural diversity of chiral pharmaceuticals. RP showed the highest potential for successful chiral resolution in HPLC and LC/MS analysis when compared to normal phase and polar organic separation modes. Method development consisted of optimizing mobile phase eluting strength, nature of organic modifier, nature of additive and column temperature. The newer CSPs, cellulose tris(3-chloro-4-methylphenylcarbamate) and amylose tris(2-chloro-5-methylphenylcarbamate), were compared to the commonly used cellulose tris(3,5-dimethylphenylcarbamate) in regards to their ability to provide baseline resolution. Comparable success rates were observed for these three CSPs of quite complimentary chiral recognition ability. The same method development strategy was evaluated for LC/MS analysis. Diethylamine as additive had a negative effect on analyte response with positive ion mode electrospray (ESI⁺) MS(/MS) detection, even at very low concentration levels (e.g., 0.025%). Decreasing the organic modifier (acetonitrile or methanol) content in the mobile phase often improved enantioselectivity. The column temperature had only a limited effect on chiral resolution, and this effect was compound dependent. Ammonium hydrogencarbonate was the preferred buffer salt for chiral LC with ESI⁺ MS detection for the successful separation and detection of most basic pharmaceutical racemic compounds. Ammonium acetate is a viable alternative to ammonium hydrogencarbonate. Aqueous formic acid with acetonitrile or methanol can be successfully used in the separation of acidic and neutral racemates. Cellulose tris(3-chloro-4-methylphenylcarbamate) and amylose tris(2-chloro-5-methylphenylcarbamate) emerge as CSPs of wide applicability in either commonly used separation modes rivaling such well established CSPs as cellulose tris(3,5-dimethylphenylcarbamate). Screening protocols including these two new CSPs in the preferentially screened set of chiral columns have higher success rates in achieving baseline resolution in shorter screening time.     

Synthesis and spectroscopic characterization of indomethacin-Cd(II), Ce(III), and Th(IV) complexes: IR, 1H NMR,thermal, and biological studies

Solid complexes have been prepared and characterized by IR, UV-Vis, elemental analysis, and ¹H NMR. Indomethacin forms complexes with Cd(II), Ce(III), and Th(IV) ions in molar ratios (ligand: metal) (2: 1), (3: 1), and (4: 1), respectively. The IR spectra of the complexes suggest that the Indomethacin behaves as a monobasic monodentate ligand coordinated to the metal ions via the deprotonated carboxylate group. Prepared complexes exhibit higher antimicrobial activity against several microorganisms, compared to free ligand.     

UV/Vis, IR and 1H NMR spectrophotometric studies of some bisazo-dianil compounds based on bis-(hydroxy, formyl) phenylazo phenylene and anthranilic acid

The electronic absorption spectra of some bisazo-dianils are studied in organic solvents of different polarity and in buffer solutions of varied pH. The different absorption bands are assigned to the corresponding electronic transitions, the solvent effect on the CT band energy is also discussed. The spectral study in buffer solutions is utilized for the determination of the pKa of the phenolic OH-groups. The important bands in the IR spectra as well as the signals of the 1H NMR spectra are assigned and discussed in relation to molecular structure. The fluorescence spectra of the compounds are recorded. The fluorescence quantum yield and pK in the ground and excited states are determined.     

UV-vis, IR and 1H NMR spectroscopic studies of some mono- and bis-azo-compounds based on 2,7-dihydroxynaphthalene and aniline derivatives

The absorption spectra of mono- and bis-azo-derivatives obtained by coupling the diazonium salts of aromatic amines and 2,7-dihydroxynaphthalene have been studied in six organic solvents. The different absorption bands have been assigned and the effect of solvents on the charge transfer band is also discussed. The diagnostic IR spectral bands and 1H NMR signals are assigned and discussed in relation to molecular structure. Also, semi-empirical molecular orbital calculations using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory have been performed to investigate the molecular and electronic structures of these compounds. According to these calculations, an intramolecular hydrogen bonding is essential for stabilization of such molecules.     

An NMR, IR and theoretical investigation of (1)H chemical shifts and hydrogen bonding in phenols

The change in (1)H NMR chemical shifts upon hydrogen bonding was investigated using both experimental and theoretical methods. The (1)H NMR spectra of a number of phenols were recorded in CDCl(3) and DMSO solvents. For phenol, 2- and 4-cyanophenol and 2-nitrophenol the OH chemical shifts were measured as a function of concentration in CDCl(3). The plots were all linear with concentration, the gradients varying from 0.940 (phenol) to 7.85 (4-cyanophenol) ppm/M because of competing inter- and intramolecular hydrogen bonding. Ab initio calculations of a model acetone/phenol system showed that the OH shielding was linear with the H...O=C distance (R) for R < 2.1 A with a shielding coefficient of - 7.8 ppm/A and proportional to cos(2)phi where phi is the H...O=C--C dihedral angle. Other geometrical parameters had little effect. It was also found that the nuclear shielding profile is unrelated to the hydrogen bonding energy profile. The dependence of the OH chemical shift on the pi density on the oxygen atom was determined as ca 40 ppm/pi electron. This factor is similar to that for NH but four times the value for sp(2) hybridized carbon atoms. The introduction of these effects into the CHARGE programme allowed the calculation of the (1)H chemical shifts of the compounds studied. The CHARGE calculations were compared with those from the ACD database and from GIAO calculations. The CHARGE calculations were more accurate than other calculations both when all the shifts were considered and also when the OH shifts were excluded. The calculations from the ACD and GIAO approaches were reasonable when the OH shifts were excluded but not as good when all the shifts were considered. The poor treatment of the OH shifts in the GIAO calculations is very likely due to the lack of explicit solvent effects in these calculations.     

Structure of N-(1-silatranylmethyl) and N-(trimethoxysilyl-methyl) derivatives of nitrogen-containing heterocycles according to data of NMR, IR, and UV spectroscopy

The ¹H, ¹³C, ¹⁵N, and ²⁹Si NMR, IR, and UV spectra of N-(1-silatranylmethyl) and N-(trimethoxysilylmethyl) derivatives of nitrogen heterocycles have been studied. The dependence and interrelation of the chemical shifts of ²⁹Si and ¹⁵N nuclei of the silatranyl group in the spectra of N-(1-silatranylmethyl)-substituted nitrogen heterocycles are determined by the nature of the heterocyclic system. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1857–1865, December, 2006.     

Quantum mechanical and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV) investigations of antiepileptic drug Ethosuximide

The Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of antiepileptic drug Ethosuximide (ETX) have been recorded and analyzed. In addition, the IR spectra in CCl(4) at various concentrations of ETX are also recorded. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of Density Functional Theory (DFT) method. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge Including Atomic Orbital (GIAO) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by Time-Dependent Density Functional Theory (TD-DFT) approach. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with observed spectra.     

Miniaturised method for the quantitation of stabilisers in microtome cuts of polymer materials by HPLC with UV, MS or MS2 detection

A method for quantitative depth profiling of polymer stabilisers in polypropylene materials is presented. Microtome cuts down to 10 μm thickness were prepared and an amount of as low as 10 mg was used for subsequent analysis. The sample preparation procedure included dissolution in toluene, followed by precipitation of the polymer by addition of methanol or acetonitrile, and subsequent analysis of the solution by reversed phase HPLC coupled with UV, MS and MS² detection. A comparison of the different detection techniques is given and their particular advantages are discussed. Depending on the stabiliser type, the presented method with MS detection can quantify stabiliser concentrations down to 0.007 mg?L^?1 (this corresponds to 0.0007 mg?g^?1 in the polymer sample) with repeatabilities better than 5 % relative standard deviation (n?=?3). This equals a quantitation of absolute stabiliser amounts at the 0.1-μg level and concentrations down to 0.1 mg?L^?1 in the corresponding polymer extracts. The developed method shows high sensitivity by the use of MS detection as well as good repeatabilities. Mainly due to the use of an appropriate internal standard, improved repeatability during sample extraction could be obtained. Furthermore, the applicability to real samples has been demonstrated.     

Synthesis and 1H, 19F NMR spectroscopic characterization of (pentafluorophenyl)3-n (pyrazol-1-yl-tetrafluorophenyl)n=1,2 porphyrins

Three new porphyrins bearing in the meso positions 4-(pyrazol-1-yl)-2,3,5,6-tetrafluorophenyl substituents have been prepared and characterized by nmr spectroscopy.