Proton NMR Spectra Research Articles

13C Saturation-Transfer Difference (STD)-NMR Experiments Using INEPT Polarization Transfer

Saturation-transfer difference (STD)-NMR spectroscopy has been widely used to screen potential ligands for binding to large receptor molecules. The STD-NMR experiment is typically based on a proton NMR spectrum, which can suffer from spectral overlap, leading to missing information in STD-based epitope mapping. Two-dimensional STD-NMR experiments can alleviate spectral overlap, but are time consuming. Here, we examine the feasibility of saturating protons in a receptor molecule and observing the STD effect on nearby carbon nuclei after transferring polarization from protons to carbons using the insensitive nuclei enhanced by polarization transfer (INEPT) pulse sequence. We show that under favorable conditions, a 1H→13C STD-INEPT experiment can give information similar to that obtained from a two-dimensional heteronuclear experiment, but in significantly less time. The STD-INEPT experiment could be especially useful when studying mixtures of ligands in which the peak positions in the proton and HSQC spectrum change significantly, and in particular, when using high-throughput, automated methods to analyze the data.

Synthesis, Spectroscopic and Computational Studies of Some Metals Chelates with Chromene-2-one and Pyrazine-Based Ligands

The present paper deals with the synthesis of cobalt(II), nickel(II), copper(II) and cadmium(II) complexes with two bidentate ligands, L1 (3-(quinoxaline-2-yl)-coumarin) and L2 (2-methylene-2H-chromene-3-(methyl carbonimidic)thioanhydride). The L1 ligand was prepared by treating w-bromo-3-acetylcoumarin with 1,2-phenylenediamine whereas the ligand L2 was prepared through substitution reaction ofw-bromo-3-acetylcoumarin with potassium thiocyanate in ethanol medium. The confirmation of the structures for L1 and L2 were done by (C.H.N.S.) elemental analysis, FT-IR, NMR and mass spectra. The metal complexes of cobalt(II), nickel(II), copper(II) and cadmium(II), with L1 and L2, were prepared and isolated in the solid state then characterized by (C.H.N.M) elemental analysis, proton and carbon-13 NMR, FT-IR and mass spectra. Furthermore, the thermal analysis (TG-DSC) for some complexes assisted us in the elucidation of the suggested structures of complexes and confirmed their thermal stability. The results obtained from elemental analysis, magnetic susceptibility and thermal analysis confirmed that all metal complexes were formed in 2:1 molar ratio of ligand to metal with octahedral structures except cadmium(II) complexes which were in a tetrahedron geometry with 1:1 mole ratio. The complexes are found to be soluble in DMF and DMSO. The results obtained from TG-DSC analysis revealed that the metal complexes were thermally stable with point decomposition over 350 °C. The DFT/TDDFT calculations were carried out to provide the electronic structures and spectra of the compounds.

Isatin Derived Mixed Ligand Metal Complexes as Antimicrobial, Antioxidant Agents and Catalyst for Oxidation of Styrene

A novel series of mixed ligand transition metal complexes of Cu(II), Zn(II), Ni(II) and Co(II) have been synthesized from the Schiff base ligand, 3-(naphthalen-1-ylimino)indolin-2-one (achieved by the condensation of isatin and naphthylamine) and 1, 10-phenonthroline. The structural features were corroborated by means of elemental analyses, molar conductance, IR, UV-Vis, 1H NMR and mass spectral studies. The data displays that these complexes have the composition of [MLX] type where X = 1, 10-phenonthroline. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion. The IR spectral data of the ligand exhibits the presence of iminic group and its complexes manifest that the imine group of the Schiff base coordinate with the metal ion and decreased value of carbonyl group indicates which coordinate to the metal. The proton NMR spectrum of the ligand shows the presence of imine group. The mass spectral data also confirms the metal complexes as [MLX] type. Molar conductance values of the complexes have been found in the range of 5–14 ohm−1cm2mol−1, suggesting the non-electrolytic nature of the complexes. The antimicrobial study reveals that copper and cobalt complexes are better antimicrobial agents than the standard drug streptomycin and Nystatin. The copper and cobalt complexes exhibit remarkable antioxidant potential than the other complexes. The catalytic oxidation of styrene by H2O2 was carried out in acetonitrile in the presence of mixed ligand metal complex as catalyst. The result of the catalytic study reveals that the zinc complex effectively catalyses the oxidation of styrene.

Synthesis of Azulitriphyrins(1.2.1) and Related Benzocarbatriphyrins.

Bis(pyrrolylmethyl)azulene dialdehydes underwent intramolecular McMurry coupling, and following oxidation with DDQ and addition of trifluoroacetic acid, gave aromatic azulitriphyrin cations. The proton NMR spectra for these contracted carbaporphyrinoids showed the internal CH upfield at ca. 2 ppm, while the bridging methine units appeared downfield between 8 and 10 ppm, demonstrating that the macrocycles possess significant 14π electron diamagnetic ring currents. Although protonated azulitriphyrins(1.2.1) proved to be very stable, the free base forms were unstable and could not be isolated. Treatment of an azulitriphyrin with KOt-Bu-t-BuOOH gave rise to oxidative ring contractions that afforded the first examples of benzocarbatriphyrins. These contracted porphyrinoids also exhibit aromatic ring currents, and the internal CH resonances shifted upfield to 0.5-0.7 ppm. Protonation afforded cations with slightly enhanced diatropic properties. Nucleus independent chemical shift and anisotropy of induced current density calculations confirmed that benzocarbatriphyrins are 14π electron delocalized aromatic systems that bypass the fused arene units.

Ring inversion in cyclohexane: a textbook example

ABSTRACT The ring inversion of cyclohexane is a classic textbook example in organic chemistry of large-scale intramolecular interconversion. Early work by Luz using deuterated cyclohexane has shown how the interconversion rate can be studied. Here the complex proton NMR spectrum of cyclohexane is reported. We apply liquid-crystal 1H NMR spectroscopy as a function of temperature to study the interconversion rate process. For low temperatures interconversion is slow, at higher temperatures the fast interconversion limit is approached. For intermediate temperatures significant line broadening is observed as the signature of the interconversion process.

Azulichlorins and Benzocarbachlorins Derived Therefrom.

Acid-catalyzed condensation of azulidipyrrane aldehydes with a dihydrodipyrrin carbaldehyde afforded the first examples of azulichlorins. These macrocyclic products were isolated in a monoprotonated form, and the free bases proved to be somewhat unstable. The monocations were strongly diatropic, and proton NMR spectroscopy showed the internal C-H at ca. -2 ppm. Addition of TFA gave the related dications, but these exhibited significantly reduced aromatic ring currents. Reaction of an azulichlorin with tert-butyl hydroperoxide and KOH in dichloromethane/methanol gave a benzocarbachlorin and two related aldehydes. The UV-vis spectrum for the benzocarbachlorin showed a split Soret band at 414 and 430 nm, together with a strong chlorin-like absorption at 684 nm. The proton NMR spectrum indicated that the carbachlorin is strongly aromatic and the internal C-H was observed at -4.64 ppm. Addition of TFA afforded a C-protonated dication with a significantly increased diatropic ring current. The proton NMR spectrum, NICS calculations, and AICD plots indicated that the system favors a 22π electron delocalization pathway that runs through the fused benzo unit. Addition of TFA to the benzocarbachlorin aldehydes primarily led to the formation of monocations, and the generation of C-protonated dications was no longer favored due to the presence of electron-withdrawing formyl moieties.

Elucidation of Interactions between l‐Ascorbic Acid and Mixed Micellar Aggregates of Catanionic {Sodium Dodecylsulfate + Cetyltrimethylammonium Bromide} Surfactants via Physicochemical and Spectroscopic Studies

AbstractSurfactant micelles mimic the microenvironment present in biological systems and can act as a medium for antioxidant studies. Moreover, the thermodynamic profile of micellization and spectroscopic studies provides very good information about interactions in these systems. Thus, the mixed micellar behavior of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) at varying mole fractions of SDS was studied in (0.01, 0.02, and 0.03) mol kg−1 ʟ‐ascorbic acid(aq) solutions with the aid of various techniques viz., conductivity, density and sound velocity, and spectroscopy. From the CMC values of the mixed surfactants, the degree of ionization (β) and thermodynamic parameters (, , and ) were evaluated at 298.15, 308.15, and 318.15 K. The UV absorption spectra were recorded in (1–3) × 10−4 mol kg−1 ʟ‐ascorbic acid(aq) solutions at various mole fractions of SDS. The proton (1H) NMR spectra of mixed (SDS + CTAB) surfactants were studied in (0.01–0.03) mol kg−1 ʟ‐ascorbic acid solutions. Hydrodynamic diameters (Dh) of mixed micellar aggregates were obtained from the dynamic light scattering (DLS) studies. The present studies suggest the predominance of ionic‐hydrophilic interactions between the ionic head groups {O‐SO3− or N+ (CH3)3} of surfactants and the polar (–OH, –C=O and –O–) sites of ʟ‐ascorbic acid.

Anti-HIV-1 activity of quinic acid isolated from Helichrysum mimetes using NMR-based metabolomics and computational analysis

Helichrysum species are widely used in traditional medicine with potential against infectious diseases. Extraction of the aerial parts of 32 Helichrysum species was done using polar (methanol:water (1:1)) and non-polar (hexane, dichloromethane and acetone) solvent systems. Anti-human immunodeficiency virus (HIV) bioassays revealed that polar extracts of H. mimetes and H. chrysargyrum (2.5 μg/mL), polar and non-polar extracts of H. cephaloideum (25 μg/mL) and polar and non-polar extracts of H. zeyheri, H. setosum, H. platypterum and H. kraussii at (2.5 μg/mL), had greater than 90% inhibitory activity. The polar extract of H. mimetes (100 μg/mL) exhibited 55.93% reverse transcriptase (RT) inhibition as a possible indication of the mechanism of action. Proton NMR spectra of the polar extracts exhibited the presence of aromatic compounds and carbohydrate moieties. Principal component analysis (PCA) of the polar extracts showed clustering related to the activity of the extracts with good predictability scores (Q2 > 0.5). However, orthogonal projections to latent structures discriminant analysis (OPLS-DA) predictability of the model was low based on the Q2 at approximately 0.25. Quinic acid (QA) isolated from H. mimetes showed promising anti-RT activity (IC50 = 53.82 μg/mL) comparable to the positive drug control, doxorubicin (IC50 = 40.31 μg/mL). A molecular docking study revealed the probable binding site and conformation of QA within cavity 4, with a docking score of −8.03. The docking score of doxorubicin within cavity 4 was −7.87. These are the first reports of QA's HIV-1-RT activity, as well as doxorubicin's docking characteristics on this enzyme.

Ortho-Quinone Methide Driven Synthesis of New O,N- or N,N-Heterocycles.

To synthesize functionalized Mannich bases that can serve two different types of ortho‐quinone methide (o‐QM) intermediates, 2‐naphthol and 6‐hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o‐QM and aza‐o‐QM were also synthesized by mixing 2‐naphthol, 2‐nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio‐ and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o‐QMs/aza‐o‐QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H‐benzo[a]xanthen‐12‐one (11), formed via o‐QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low‐field position of proton H‐1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)‐C(1)‐C(12b)‐C(12a)‐C(12)=O structural fragment.

A First Step Toward Unraveling the Energy Metabolism in Endurance Horses: Comparison of Plasma Nuclear Magnetic Resonance Metabolomic Profiles Before and After Different Endurance Race Distances.

Endurance racing places high demands on energy metabolism pathways. Metabolomics can be used to investigate biochemical responses to endurance exercise in humans, laboratory animals, and horses. Although endurance horses have previously been assessed in the field (i.e., during races) using broad-window Nuclear Magnetic Resonance metabolomics, these studies included several different race locations, race distances, age classes, and race statuses (finisher or elimination). The present NMR metabolomics study focused on 40 endurance horses racing in three race categories over 90, 120, or 160 km. The three races took place in the same location. Given that energy metabolism is closely related to exercise intensity and duration (and therefore distance covered), the study's objective was to determine whether the metabolic pathways recruited during the race varied as a function of the total ride distance. For each horse, a plasma sample was collected the day before the race, and another was collected at the end of the race. Sixteen, 15, and 9 horses raced over 90, 120, and 160 km, respectively. Proton NMR spectra (500 MHz) were acquired for these 80 plasma samples. After processing, the spectra were divided into bins representing the NMR variables and then classified using orthogonal projection on latent structure models supervised by the sampling time (pre- or post-race) or the distance covered. The models revealed that the post-race metabolomic profiles are associated to the total ride distance groups. By combining biochemical assay results and NMR data in multiblock models, we further showed that enzymatic activities and metabolites are significantly associated to the race category. In the highest race category (160 km), there appears to be a metabolic switch from carbohydrate consumption to lipid consumption in order to maintain glycaemia. Furthermore, signs of protein breakdown were more apparent in the longest race category. The metabolic shift seen in the different racing categories could be related to a mixture of three important factors that are the ride distance, the training status and the inherited endurance capacity of the various horses competing.

Benzoxazine Containing Fluorinated Aromatic Ether Nitrile Linkage: Preparation, Curing Kinetics and Dielectric Properties.

Benzoxazine containing fluorinated aromatic ether nitrile linkage (FAEN-Bz) had been synthesized from 2,6-dichlorobenzonitrile, 4,4’-(hexafluoroisopropylidene)diphenol (bisphenol AF), 3-Aminophenol, formaldehyde, phenol by condensation polymerization and Mannich ring-forming reaction. Structures of the monomer were verified by Proton NMR spectrum (1H-NMR) and Fourier transform infrared spectroscopy (FTIR). Curing behaviors and curing kinetics of designed monomers were investigated and discussed. The activation energy was calculated and possible polymerization mechanisms were also proposed. Then, properties of cured polymers including crosslinking degrees, thermal decomposition, surface wettability and energy, and dielectric properties were studied and discussed. Additionally, programmed integral decomposition temperature (IPDT) was also used to evaluate the thermal stability of final polymers. Results indicated that the incorporation of benzoxazine and nitrile resulted in increased thermal stability and char yields. Moreover, the surface wettability and dielectric properties of poly(FAEN-Bz) can be easily controlled by tuning the curing temperatures and time.

Thiazoline-pyrene selective and sensitive fluorescence "turn-on" sensor for detection of Cu2.

A thiazoline and pyrene containing sensor 1 was synthesized via one-pot reaction and utilized as a highly selective and sensitive fluorescence "turn-on" sensor for Cu2+ detection, via the fluorescence enhancement of pyrene monomer emission. The 2:1 stoichiometry of 1 and Cu2+ was calculated from Job's plots based on fluorescent titrations, and the complexation of 1 with Cu2+ was also supported by mass spectra, Fourier transform infrared spectra, proton NMR spectra and density functional theory analysis. The fluorescence intensity of 1 at 389 nm and 410 nm increased significantly upon the addition of Cu2+. Limit of detection and association constant value of 1-Cu2+ were calculated using standard deviations and linear fittings, respectively. Results showed that 1 was active for Cu2+ detection in the wide pH range of 2.0-11.0.

Low-Temperature Magnetism of Gold Nano Particles Contained in Electrochemical Sugar Recognition System

Low-temperature magnetic properties were investigated on the gold nano particles (GNPs) with an average size of 11.5 nm, assembled with molecules of ruthenium complex (Ru0), and phenylboronic acid (B0) by the proton nuclear magnetic resonance ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> H-NMR) and susceptibility measurements. The temperature dependence of the NMR shift and the uniform susceptibility was described as the sum of the Curie-Weiss term and a positive constant term. From the former, the average number of Ru0 on each GNP was estimated to be 118, which is 23% of the calculation. The finite positive constant term shows a clear contrast with the well-known fact that the bulk gold is diamagnetic. Finally, a disappearance of the motional narrowing effect in the proton NMR spectra below 60 K indicates that the wavering motion of Ru0 complexes on GNP at room temperature is frozen at low temperatures.

Synthesis and Characterisation of New Copolymer Resin Derived from 4-Hydroxybenzoic Acid and Adipamide

Abstract A new copolymer 4-hydroxybenzoic acid – Adipamide –Formaldehyde resin was synthesized using 2M HCl as a catalyst by condensation of 4-hydroxybenzoic acid and adipamide with formaldehyde. The copolymer resin composition has been determined on the basis of elemental analysis. The number average sub-atomic mass of the resin was dictated by conductometric titration in a non-aqueous medium, viscometric estimations in dimethyl suphoxide were done to ascertain the trademark capacities and constants. The copolymer has been portrayed by uv-obvious, I.R., proton NMR spectra and thermo gravimetric examination. The structure of the copolymer was affirmed based on otherworldly information. The morphological element of the 4-HBAF copolymer was built up by examining electron microscopy (SEM). Thermogravimetric analysis of copolymer resin in present study has been carried out by non-isothermal thermogravimetric analysis technique. Thermal study of the resins was carried out to determine their mode of decomposition and relative thermal stabilities.

Synthesis, Characterization and Anticancer Activity of Isonicotinylhydrazide Metal Complexes

This study focuses characterization of iron (II), iron (III), cobalt (II), copper (II) and nickel (II) complexes of Isoniazid (INH) and studying their spectroscopic as well as physiochemical properties. FTIR studies showed that INH binds the metal from oxygen of carbonyl group and nitrogen of amino group. The proton NMR spectra of the metal complexes confirmed the conversion of ligand molecules into their respective metal complexes. However, pattern of splitting and shapes of peaks was observed but the protons resonated in the expected region. XRD patterns may be concluded that the complexes are mostly comprised of nano-sized particles behaving like amorphous materials. Scanning electron microscopy (SEM) revealed marked changes in the morphology of complexes, and their degradation at higher temperature strengthens the hypothesis of the successful formation of complexes. The MTT cytotoxicity assay was used for the screening these complexes against four human cell lines but the results did not prove significant.

Interaction of β-cyclodextrin with tosyl chloride in an aqueous alkaline medium

The regioselective functionalisation of the cyclodextrin matrix provides the possibility of purposefully altering the ability of cyclodextrins to form inclusion compounds, as well as to ensure their solubility, thus expanding the scope of their practical application [1, 2]. The most significant and promising trend in the selective modification of β-cyclodextrins consists in the preparation of tosyl derivatives, given that the substitution of such nucleophilic reagents as iodide, azide, thioacetate, hydroxylamine, alkylamide or polyalkylamide for the tosyl group results in the corresponding monosubstituted derivatives. In this study, we impl emented a method for the synthesis of mono-6-O-(p-toluenesulphonyl)-β-cyclodextrin, which was improved by β-cyclodextrin reacting with tosyl chloride in an aqueous medium in the presence of a base. The reaction of β-cyclodextrin with tosyl chloride in an aqueous alkaline medium produced a 58% yield of mono -6- O-(p-toluenesulphonyl)-β-cyclodextrin not requiring additional purification. The optimal concentrations of β-cyclodextrin and tosyl chloride were found to be 0.0032 mol/l and 0.0015 mol/l, respectively. It was shown that a decrease in the rate of filtering the unreacted tosyl chloride out of the reaction mixture is acc ompanied by an increase in the proportion of ditosyl derivatives and mono(3,6-anhydro)-β-cyclodextrin resulting from the intramolecular cyclisation of mono-6-O-(p-toluenesulphonyl)-β-cyclodextrin at room temperature under alkaline conditions. The structure of the obtained mono-6-O-(p-toluenesulphonyl)-β-cyclodextrin was confirmed using Proton NMR Spectroscopy. The proton NMR spectrum of the product resulting from the reaction of β-cyclodextrin with tosyl chloride contains signals corresponding to a tosyl radical: a singlet (2.42 ppm) and two doublets (7.41–7.43 ppm) produced by hydrogens of the benzene ring having radicals in the para position. Monosubstitution was confirmed by comparing the integrated intensities of signals produced by the protons of the cyclodextrin skeleton and the protons from the aromatic part of the reaction product. Their ratio indicated that only one of the seven primary hydroxyl groups of β-cyclodextrin was substituted.

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

DFT studies have been carried out on 46 azuliporphyrin (AzP) and tropiporphyrin (TrP) tautomers, cations, and dications. The structures were minimized using DFT-B3LYP/6-311++G(d,p), and the relative stabilities of the tautomers for each series were computed with M06-2X and B3LYP-D3 functionals. Nucleus independent chemical shifts, both NICS(0) and NICS(1) zz, were calculated for both the center of the macrocycles and the individual pyrrolic and carbocyclic subunits. In addition, anisotropy of induced current density (AICD) plots were generated for all of the species under investigation. The results provided insights into the favored conjugation pathways and aromatic properties of these important carbaporphyrinoid systems. The π delocalization pathways for AzP were complex, and contrary to previous speculations, there was no evidence for tropylium characteristics in the favored free base structure. The global diatropicity of AzP was found to increase with increasing solvent polarity, in agreement with experimental observations. TrP was shown to be planar and to possess a large global diamagnetic ring current. However, NICS calculations and AICD plots indicated that the cycloheptatrienyl components of the two most favored TrP tautomers have paratropic characteristics. These results are not fully consistent with the proton NMR spectra for TrPs. A dihydroTrP and a Diels-Alder adduct were investigated, and these showed exceptionally large shielding effects with NICS(1) zz values of -36.53 and -36.92 ppm, respectively, in agreement with experimental results. A silver(III) complex of tropiporphyrin was also examined, and this showed no paratropic character for the seven-membered ring, although in this case, the system was found to be severely twisted. Overall, the results provide important information about the electronic properties of AzP and TrP tautomers, as well as for related protonated species, and complement the extensive experimental studies that have been conducted on these systems.

Spectroscopic (FTIR, FT-Raman, 1H NMR and UV–Vis) and DFT/TD-DFT studies on cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine

The density functional theory calculations and spectroscopic characterization (FTIR, FT-Raman, 1H NMR and ultraviolet–visible) of the pharmaceutically active compound Cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine (CHBT) have been carried out. The recorded Vibrational, proton NMR and electronic spectra have been compared with the simulated one and they are found in well agreement. The bands appearing in FTIR and FT-Raman spectra are assigned with great accuracy using animated modes. The ultraviolet–visible (UV–Vis) absorption bands are assigned using molecular orbitals data obtained by TD-B3LYP/PCM calculations with 6-311G(d,p) basis set. Proton NMR signal peaks have been assigned using GIAO-B3LYP/6-311G(d,p)/PCM method. The hyperconjugative interactions and charge delocalization within the molecule have been studied using natural bond orbital (NBO) analysis. The non-linear optical (NLO) behavior of the present compound has been investigated using theoretical dipole moment, polarizability and first static hyperpolarizability values. The thermodynamic functions (entropy, heat capacity and enthalpy) obtained from harmonic force field calculations for the range of temperature 100–1000 K are reported. Moreover, highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO-LUMO) analysis, molecular electrostatic potential (MEP) diagram, global reactivity descriptors and condensed or atomic Fukui Functions have been also presented.

Interactions of poly (vinyl alcohol) and poly (N-isopropylacrylamide) with tannic acid and pyrazole derivatives: The identification of H-bonds for revealing a “Two-Molecules” carrier system

The interactions between tannic acid (TA), a natural bioactive polyphenol, and two biodegradable polymers have been investigated in the presence and absence of a pyrazole derivative through their NMR and UV–Vis spectra as well as quantum chemical calculations. The role of H-bonding ability of organic molecules is studied for clarifying the molecule carrier capability of the polymers. TA uses its hydrogen bonding capability controversially depending on the functional groups of the polymers in solutions/mixtures in DMSO. In the mixtures with poly (vinyl alcohol) (PVA), the color of TA is darkened, which associates to the appearance of a new UV–Vis band, the disappearance of two one-dimensional proton NMR signals, and some differences in the heteronuclear multiple bond correlation (HMBC) NMR spectra. The H-bond interactions in the mixtures of TA and PVA are mainly between oxygen of the polymer backbone and proton of OH of TA in addition to hydrogen bonding interaction between O atom of aromatic rings of TA and OH moiety of PVA as revealed by UV–Vis spectroscopy and computational results. Association of the pyrazole derivative in the mixture introduces a weak interaction between protons of OH belonging to outer core of TA and oxygen of CO of the pyrazole derivative. In the mixtures of TA with poly (N-isopropylacrylamide) (PNIPAM), a noticeable change is not observed in the UV–Vis and one-dimensional proton NMR spectra irrespective of the addition of the pyrazole derivative. However, the weak interactions between TA and the pyrazole derivative in mixtures with PNIPAM are apparent in their HMBC NMR spectra. PNIPAM and TA interact mainly through the proton of OH in the outer core of TA and the oxygen of CO of PNIPAM backbone as in the case of TA and the pyrazole derivative. They also interact through the CO in the central core of TA and proton of OH of PNIPAM backbone. To assess the effect of the different H-bond environments on the UV–Vis and NMR spectra, we have performed quantum chemical calculations employing B3LYP density functional approach. The present calculations appear quite useful in explaining the source of spectral differences in different media. Based on the spectral analysis, we suggest that PVA is a better molecule carrier with respect to PNIPAM.

Synthesis and characterization of triruthenium carbonyl incorporating 4-pyridones as potential antitumor agents

Four new organometallic triruthenium carbonyl incorporating 4-pyridones: [Ru3(CO)8(2L-2H)] (1, L = N-benzyl-3-hydroxy-2-methyl-4-pyridone; 2, L = 3-hydroxy-2-methyl-N-phenyl-4-pyridone; 3, L = 3-hydroxy-N,2-dimethyl-4-pyridone; 4, L = 2-methyl-4-pyridone) were synthesized and characterized. Proton NMR spectrum of 1 shows doublets for the two-nonequivalent benzylic hydrogens due to restricted rotation around C-N bond upon bonding to Ru(2)---Ru(3) as opposed to a singlet in the unbound N-benzyl-3-hydroxy-2-methyl-4-pyridone. Compounds 1 and 3 were characterized by X-ray diffraction analyses. Compounds 1 and 3 consists of two ruthenium-ruthenium bonds Ru(1)-Ru(2), Ru(1)-Ru(3) and a non-bonded separation of two ruthenium atoms defined by Ru(2) … Ru(3), which is bridged by two 3 electron donar oxygen atoms through two-pyridinonato ligands above and below triruthenium plane, and 8 terminal CO groups. Atoms Ru(2) and Ru(3) ligated by two CO ligands each and Ru(1) with four. Antitumor activity of the compounds 1–4 has been evaluated against five types of human cancer cell lines. Compounds 1 and 2 show excellent antitumor activity due to lipophilic nature of N-substituted arene pyridinonato ligands than compounds 3 and 4. Structure-activity studies show that there is a correlation between the N-substituted arene pyridinonato ligands and an increase in activity following the order 1 > 2>3 > 4. The anticancer activity of compounds 1 and 2 is between 1–2 orders of magnitude more active than cisplatin. This is possibly due to substitution of CO ligands at Ru(1) by transferrin delivery vehicle transporting to cancer cells and lipophilic N-substituted arenes diffuse through lipophic membrane leading to apoptosis and other carbonyl groups under physiological conditions likely function as carbonyl releasing molecules (CORMs).