Position Of OH Group Research Articles

Temperature dependence of structural evolution and fragility of glass-forming monohydroxy alcohols

The dynamic, structural, and thermodynamic properties of thirty-four monohydroxy alcohols with varying molecular architectures, including differences in alkyl chain length, OH group position, and presence/type of carbon ring, were investigated. Results of dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and X-ray diffraction, were analyzed to verify correlations between the glass transition temperature (Tg), molar mass (M), boiling temperature (Tb), dynamic and thermodynamic fragility (mα and m), and the structurally related parameter (S). The collected data revealed that primary and secondary alcohols generally adhere to the correlations Tg ∝ M0.51 and Tb = 132 + 2.2Tg, while alcohols with phenyl ring deviate from these trends. Moreover, it was found that the changes in the width of the main diffraction peak normalized by the peak position ΔQM/QM over temperature scaled by Tg correspond to the variable m. However, the extent and course of this relationship varies across alcohols belonging to different structural groups. The weakest correlation and largest scatter between S and m occur for phenyl alcohols exhibiting the greatest structural heterogeneity. This study underscores the challenges of establishing universal correlations between physical variables within the diverse group of monohydroxy alcohols and emphasizes the importance of considering specific molecular features in predicting glass-forming behaviour.

Natural flavonoids as promising lactate dehydrogenase A inhibitors: Comprehensive in vitro and in silico analysis.

The inhibitory potential of 17 flavonoids on lactate dehydrogenase A (LDHA), a key enzyme in the downstream process of aerobic glycolysis in cancer cells, is investigated. Fisetin exhibited excellent inhibitory activity (IC50 = 0.066 µM). Quercetin 3-β-D-glucoside, quercetin 3-galactoside, luteolin, neoeriocitrin, and luteolin 7-O-β-D-glucoside showed good inhibitory activity (IC50 = 1.397-15.730 µM). Biochanin A, baicalein, quercetin, scutellarein-7-glucuronide, diosmetin, baicalein 7-O-β-D-glucuronide, and apigenin 7-apioglucoside demonstrated moderate inhibitory activity (IC50 = 33.007-86.643 µM). Eriodictyol, quercetin 7-O-β-D-glucoside, apigenin 7-O-β-D-glucoside, and epicatechin were inactive. The Lineweaver-Burk plot showed that fisetin competitively inhibits NADH binding (Ki = 0.024 µM). Ki values for other compounds were calculated using the Cheng-Prusoff equation (Ki = 0.2799-2.1661 µM). The study revealed that the inhibitory effect of flavonoids varies with the number and position of OH groups and bound sugars. Molecular docking analyses indicated that flavonoids exhibited strong interactions with the NADH binding site of LDHA through hydrophobic interactions and hydrogen bonds. Molecular dynamic simulations tested the stability of the fisetin-LDHA complex over 100 ns and showed fisetin's high binding affinity to LDHA, maintaining strong hydrogen bonds. The binding energy of fisetin with LDHA was -33.928 kcal/mol, indicating its effectiveness as an LDHA inhibitor. Consequently, flavonoids identified as strong inhibitors could be potential cancer treatment sources through LDHA inhibition.

Effect of hydroxyl position on antioxidant ability of hydroxycoumarin derivatives: A theoretical investigation

Effect of the OH group position on the antioxidant ability of hydroxycoumarin derivatives (HOC) was investigated by quantum chemical computation. Frontier molecular orbitals, molecular electrostatic potential, and thermodynamic parameters were analyzed in detail. The results indicate that 3-HOC, 6-HOC, and 7-HOC exhibit as the best reactants with free radicals through analysis of global reactivity descriptor values, meanwhile H (in OH groups) of 4-HOC, 5-HOC, 6-HOC, and 7-HOC molecules are the most preferable sites for nucleophilic attacks. Besides, thermodynamic and kinetic studies reveal hydrogen atomic transfer is the primary mechanism when hydroxycoumarin derivatives react with HOO• free radical in the gas phase and pentyl ethanoate. Hydrogen atomic transfer products account for over 97 % of the total products of hydrogen atomic transfer and radical adduct formation mechanisms. According to the study, 6-HOC is the most effective scavenger of free radicals when compared to other derivatives, with a rate constant of 1.38 × 104 M−1s−1 in the gas phase and 6.5 × 103 M−1s−1 in pentyl ethanoate. The interaction of O20∙∙∙H21 in the transition state of 6-HOC is crucial in stabilizing its structure. This finding suggests that 6-HOC can be a potential candidate for developing antioxidants for various applications in the medical and industrial fields. The results of this study provide valuable insights into the mechanisms by which antioxidants can scavenge free radicals and protect against oxidative stress.

Ruthenium Complexes with Protic Ligands: Influence of the Position of OH Groups and π Expansion on Luminescence and Photocytotoxicity

Protic ruthenium complexes using the dihydroxybipyridine (dhbp) ligand combined with a spectator ligand (N,N = bpy, phen, dop, Bphen) have been studied for their potential activity vs. cancer cells and their photophysical luminescent properties. These complexes vary in the extent of π expansion and the use of proximal (6,6'-dhbp) or distal (4,4'-dhbp) hydroxy groups. Eight complexes are studied herein as the acidic (OH bearing) form, [(N,N)2Ru(n,n'-dhbp)]Cl2, or as the doubly deprotonated (O- bearing) form. Thus, the presence of these two protonation states gives 16 complexes that have been isolated and studied. Complex 7A, [(dop)2Ru(4,4'-dhbp)]Cl2, has been recently synthesized and characterized spectroscopically and by X-ray crystallography. The deprotonated forms of three complexes are also reported herein for the first time. The other complexes studied have been synthesized previously. Three complexes are light-activated and exhibit photocytotoxicity. The log(Do/w) values of the complexes are used herein to correlate photocytotoxicity with improved cellular uptake. For Ru complexes 1-4 bearing the 6,6'-dhbp ligand, photoluminescence studies (all in deaerated acetonitrile) have revealed that steric strain leads to photodissociation which tends to reduce photoluminescent lifetimes and quantum yields in both protonation states. For Ru complexes 5-8 bearing the 4,4'-dhbp ligand, the deprotonated Ru complexes (5B-8B) have low photoluminescent lifetimes and quantum yields due to quenching that is proposed to involve the 3LLCT excited state and charge transfer from the [O2-bpy]2- ligand to the N,N spectator ligand. The protonated OH bearing 4,4'-dhbp Ru complexes (5A-8A) have long luminescence lifetimes which increase with increasing π expansion on the N,N spectator ligand. The Bphen complex, 8A, has the longest lifetime of the series at 3.45 μs and a photoluminescence quantum yield of 18.7%. This Ru complex also exhibits the best photocytotoxicity of the series. A long luminescence lifetime is correlated with greater singlet oxygen quantum yields because the triplet excited state is presumably long-lived enough to interact with 3O2 to yield 1O2.

Synthesis of tetraalkoxyaryldihydrobenzo[g]indazoles from metabolites of dill and parsley seeds essential oil

An efficient method for the conversion of available plant allylpolyalkoxybenzenes into unsubstituted and arylsubstituted polymethoxylated aryldihydrobenzo[g]indazoles, analogues of combretastatin A4, has been developed. The selective demethylation of target compounds resulted in indazoles with different position of OH-group. Their structure was confirmed by X-ray analysis. A sea urchin embryo assay revealed the lack of tubulin-related antimitotic activity of aryldihydrobenzo[g]indazoles with systemic toxicity of a compound featuring OH group and 1-unsubstituted pyrazole ring.

Synthesis, Crystallographic, Quantum Chemical, Antitumor, and Molecular Docking/Dynamic Studies of 4-Hydroxycoumarin-Neurotransmitter Derivatives.

In this contribution, four new compounds synthesized from 4-hydroxycoumarin and tyramine/octopamine/norepinephrine/3-methoxytyramine are characterized spectroscopically (IR and NMR), chromatographically (UHPLC-DAD), and structurally at the B3LYP/6-311++G*(d,p) level of theory. The crystal structure of the 4-hydroxycoumarin-octopamine derivative was solved and used as a starting geometry for structural optimization. Along with the previously obtained 4-hydroxycoumarin-dopamine derivative, the intramolecular interactions governing the stability of these compounds were quantified by NBO and QTAIM analyses. Condensed Fukui functions and the HOMO-LUMO gap were calculated and correlated with the number and position of OH groups in the structures. In vitro cytotoxicity experiments were performed to elucidate the possible antitumor activity of the tested substances. For this purpose, four cell lines were selected, namely human colon cancer (HCT-116), human adenocarcinoma (HeLa), human breast cancer (MDA-MB-231), and healthy human lung fibroblast (MRC-5) lines. A significant selectivity towards colorectal carcinoma cells was observed. Molecular docking and molecular dynamics studies with carbonic anhydrase, a prognostic factor in several cancers, complemented the experimental results. The calculated MD binding energies coincided well with the experimental activity, and indicated 4-hydroxycoumarin-dopamine and 4-hydroxycoumarin-3-methoxytyramine as the most active compounds. The ecotoxicology assessment proved that the obtained compounds have a low impact on the daphnia, fish, and green algae population.

Influence of structural changes of cation and anion on phytotoxicity of selected surface active ionic liquids

In this study, the influence of the structural modifications of 10 surface active ionic liquids (SAILs), on toxicity towards wheat and barley germination and early growth was examined. First, SAILs containing 1,3-dialkylimiadzolium cation (1-dodecyl-3-methylimidazolium bromide, 1-dodecyl-3-ethylimidazolium bromide and 1-butyl-3-dodecylimidazolium bromide) were studied, followed by the study of SAILs containing methyl-pyridinium cation with the different position of the methyl group on pyridinium ring (N-dodecyl-2-methylpyridinium bromide, N-dodecyl-3-methylpyridinium bromide and N-dodecyl-4-methylpyridinium bromide). Furthermore, for the 1-dodecyl-3-methylimidazolium cation, the anion was changed from bromide to benzoate and hydroxybenzoate anions and the –OH group position on benzoate ring was varied (1-dodecyl-3-methylimidazolium benzoate, 1-dodecyl-3-methylimidazolium ortho-hydroxybenzoate, 1-dodecyl-3-methylimidazolium meta-hydroxybenzoate, 1-dodecyl-3-methylimidazolium para-hydroxybenzoate). The results showed that germination of both wheat and barley was decreased intensively with the increase in SAILs concentration. Moreover, the results demonstrated that the length of the longer alkyl substituent on the cation head has the most important role in toxicity, while change of the cation ring as well as the change in anion structure of the studied SAILs did not show a significant influence on germination of wheat and barley seeds and biomass reduction of young plants.

Effect of position of OH group in isomeric butanediols on intermolecular interaction with Choline Acetate: A thermodynamic study at different temperatures

The prominent effect of the position of hydroxyl groups in isomeric butanediols i.e.1,3-butanediol (1,3-BTD), 1,2-butanediol (1,2-BTD) and 2,3-butanediol (2,3-BTD) on intermolecular interactions with Choline Acetate has been investigated using various thermophysical parameters such as density ρ, speed of sound u, refractive index nD and specific conductivity κ over different concentration range and at temperatures varying from 293.15 to 323.15 K at atmospheric pressure. To gain further insight the derived parameters such as apparent molar volumes Vϕ, apparent molar isentropic compressibilities Ksϕ, and their infinite parameters mainly limiting apparent molar volumes at infinite dilution Vϕo, limiting apparent molar expansibilities Eϕo, limiting isentropic compression Kϕo, molar refraction Rm and infinite molar conductance ̂mo values have been calculated. The least values obtained for apparent molar volumes and compressibilities in case of 1,3-BTD mixtures are attributed to its highest ability to form intramolecular hydrogen bonding among isomeric butanediols and thus lesser availability to interact with Choline Acetate molecules. However for 2,3-BTD and 1,2-BTD binary mixtures the results have been explained on the basis of hydrophobic or iceberg effect where alkyl groups are present either on one end (1,2-BTD) or at both ends (2,3-BTD) while OH groups are located at vicinal carbon atoms.

Kinetically Equivalent Functionality and Reactivity of Commonly Used Biocompatible Polyurethane Crosslinking Agents

In this paper, the kinetics of the reaction of phenyl isocyanate with crosslinking agents such as sucrose, sorbitol, and glycerol are reported. Crosslinking agents were used in high molar excess to isocyanate to obtain pseudo-first-order rate dependencies, and the reaction products were separated by high-performance liquid chromatography and detected by UV spectroscopy and mass spectrometry. It was found that the glycerol’s primary hydroxyl groups were approximately four times reactive than the secondary ones. However, in the case of sorbitol, the two primary OH groups were found to be the most reactive, and the reactivity of hydroxyl groups decreased in the order of kOH(6)(8.43) > kOH(1)(6.91) > kOH(5)(1.19) > kOH(2)(0.98) > kOH(3)(0.93) > kOH(4)(0.64), where the numbers in the subscript and in the brackets denote the position of OH groups and the pseudo-first-order rate constants, respectively. The Atomic Polar Tenzor (APT) charges of OH groups and dipole moments of monosubstituted sorbitol derivatives calculated by density functional theory (DFT) also confirmed the experimental results. On the other hand, the reactions of phenyl isocyanate with crosslinking agents were also performed using high excess isocyanate in order to determine the number of OH-groups participating effectively in the crosslinking process. However, due to the huge number of derivatives likely formed in these latter reactions, a simplified reaction scheme was introduced to describe the resulting product versus reaction time distributions detected by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). Based on the results, the kinetically equivalent functionality (fk) of each crosslinking agent was determined and found to be 2.26, 2.6, and 2.96 for glycerol, sorbitol, and sucrose, respectively.

Aminomethylated Hydroxinaphthalenes: Synthesis and Application

The analysis of the literature is carried out and the results of the synthetic approaches to the aminomethylation of hydroxy derivatives of naphthalenes developed over the past 20 years are presented. Most of the described aminomethylation processes proceed as Mannich aminomethylation or, as a special case of a similar condensation --- aminobenzylation according to Betti. The results of all studies are grouped according to the nature of the amine used in the synthesis: primary, secondary, tertiary. Most of the examples were considered for 2-naphthol, however, as the analysis of literature data shows, similar methods are applicable to 1-naphthol and dihydroxynaphthalenes with different positions of OH groups in the ring --- often only the yields of the target product differ. Both the classical methods for the preparation of Mannich and Betti bases using the carbonyl component (formaldehyde, benzaldehyde and its derivatives, respectively) and special cases of synthesis, in which condensation is carried out by means of halogen derivatives, substituted azacrown ethers, etc., are presented. Particular attention is paid to the use of various catalysts and activators, allowing to significantly simplify the synthetic procedures and increase the yields of target compounds. The main fields of application of aminomethylated derivatives of hydroxynaphthalenes are presented

Congener-specific determination of hydroxylated polychlorinated biphenyls by polar-embedded reversed-phase liquid chromatography-tandem mass spectrometry.

This paper reports the development of an LC-ESI-MS2 method for the sensitive determination of hydroxylated polychlorinated biphenyls (OH-PCBs) in human serum samples. Congener-specific separation was achieved by using a polar-embedded stationary phase, previously optimized for the working group, which provided better separation of isobaric compounds than the common octadecylsilane phases. MS fragmentation patterns and energies showed differences among OH-PCB congeners, mainly depending on the position of OH-group and the number of chlorine atoms in the molecule, although the most intense transitions were always those corresponding to the neutral loss of an HCl group from the quasi-molecular ion cluster. The method allowed the determination of OH-PCBs with good linearity (dynamic linear range of four orders of magnitude with R2 higher than 0.995) and precision (relative standard deviations of absolute areas lower than 10%), and with better sensitivity than other similar methods previously described in the literature. Matrix effect has been evaluated and reduced to less than 10% by the addition of isotopically labeled standards and a 10-fold dilution of the final sample extract. The low iLODs provided by the developed method (from 1.2 to 5.4 fg µL-1 for all the OH-PCBs studied, except 4'-OHCB108, whose iLOD was 61 fg µL-1) allows dilution without losses of detected peaks. Finally, the applicability of the method has been demonstrated by analyzing human serum samples belonging to an interlaboratory exercise.

Dependence of the Enthalpy of Formation of Phenols on Molecular Structure – Semiempirical Study

The ability of three semiempirical methods (PM3, PM5, and PM7) in reproducing the enthalpy of formation (Δf H°) of polycyclic aromatic phenols (PAPs) was tested by comparing experimental and calculated values for 33 compounds. In addition, the results from the semiempirical methods were compared to those obtained from the suitable isodesmic reactions, performed using the B3LYP–D3 and M06–2X functionals in combination with the 6-311 + G(d,p) basis set. With an average absolute error less than 10 kJ mol−1, all five methodologies yielded mutually comparable results. Considering low computational cost of semiempirical methods, the influence of structural features on Δf H° of PAPs was investigated using the PM5 and PM7 methods. It was found that the greatest influence on Δf H° has the size of the molecules, while the effects of other properties, i.e., the position of the OH group, number of bay regions, and molecular branching are weaker. The influence of the OH group position decreases with its moving away from molecular ends, and eventually becomes insignificant. As branching and the number of bay regions are mutually dependent and respective molecules are often nonplanar, it is difficult to examine individual contributions of these two structural features. In general, Δf H° decreases with increasing number of bay regions and molecular branching.

Effect of temperature and position of OH group in isomeric butanediols in intermolecular interactions with 2-chloroaniline: A thermodynamic, DFT and molecular dynamics approach

The pronounced effect of the position of the hydroxyl groups in isomeric butanediols (1, 2-butanediol (12BDL), 1, 3-butanediol (13BDL) and 1, 4-butanediol (14BDL)) in the formation of hydrogen bonds with 2-chloroaniline (2CA) was investigated by using experimental and computational methods. The density (ρ) and speed of sound (u) in binary mixture was determined at T = (303.15–318.15) K and at atmospheric pressure p = 0.1 MPa. Values of excess molar volume (VmE), and excess isentropic compressibility (ksE) were determined by using experimental data. It was observed that these excess properties (VmEksE) departs negatively from the ideal mixture which indicates the formation of intermolecular hydrogen bonds. The volumetric properties like excess partial molar volume (V‾m,1EV‾m,2E), partial molar volume (V‾m,10,V‾m,20) and excess partial molar volume (V‾m,10EV‾m,20E) are derived at infinite dilutions. Quantum mechanical approach was used to study the intermolecular hydrogen bond interactions in self and cross-associated complexes of 2-chloroaniline and isomeric butanediols with the aid of DFT in the gas phase, while classical molecular dynamic simulations were carried out in the liquid phase. Experimental, quantum mechanical and classical molecular dynamic methods are used to investigate the formation of a hydrogen-bonded network between 2-chloroaniline and isomeric butanediols mixtures. The investigated results were further confirmed by the existence of hydrogen bonding evolution between 2-chloroaniline and isomeric butanediols through FT-IR Spectral studies. The Fourier transform Infrared spectroscopic data strongly confirms and support the existence of intermolecular hydrogen bonding and molecular associations between component molecules.

Catalytic properties of recombinant Thermomyces lanuginosus lipase immobilized by impregnation into mesoporous silica in the enzymatic esterification of saturated fatty acids with aliphatic alcohols

Immobilization of recombinant Thermomyces lanuginosus lipase (designated as rPichia/lip) was carried out by moisture capacity impregnation of mesoporous silica granules followed by drying, and forcible adsorption of enzyme occurred. Eventually prepared lipase-active heterogeneous biocatalysts were systematically studied for enzymatic esterification performed at ambient conditions (20 ± 2 °C, 1 bar) in unconventional anhydrous media of organic solvents such as hexane and diethyl ether. The saturated fatty acids differing in the number of carbon atoms (C2–C10, C18), and aliphatic alcohols differing in the structure of the molecules, namely both the number of carbon atoms (C2–12, C16), and the isomerism of the carbon skeleton (n- and iso-), and OH-group position (prim-, sec-, tert-) were studied as substrates for enzymatic esterification. The specificity of the heterogeneous enzymatic esterification was determined by comparing the reaction rates for various pairs of substrates; and the matrix of relative units of activities was composed. The immobilized on silica rPichia/lip was found to have sufficiently wide specificity toward saturated fatty acids and aliphatic alcohols. High reaction rates were measured in esterification of fatty acids and primary n- and iso-aliphatic alcohols possessing more than four carbon atoms in the molecules. The enanthic acid (heptanoic, C7:0) reacted with butanol (C4) with the highest rate; and the kinetic parameters such as Michaelis constant (KM) for acid and maximal reaction rate (Vmax) were determined under the studied conditions of esterification. Substrates containing aromatic residues did not participate in esterification. The lipase-active heterogeneous biocatalysts possessed considerably high operational stability, and the catalytic activity was completely retained for several tens of reaction cycles in a periodic batch process of low-temperature synthesis of various fatty acid esters.

Effect of Side Chain Functional Groups on the DPPH Radical Scavenging Activity of Bisabolane-Type Phenols.

Methods for improving the antioxidant activity of phenolic compounds have been widely investigated; however, most studies have focused on the structure–activity correlations of substituents on the aromatic rings of catechols or flavonoids. We investigated the influence of side chain functional groups on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of xanthorrhizol and curcuphenol analogues. These compounds were synthesised by the side chain functional group conversion of curcumene, followed by direct oxidation of the aromatic ring. We determined the DPPH radical scavenging activity from the half-maximal effective concentration (EC50) obtained from a DPPH assay in methanol. The positional relationships of the side chain with the aromatic ring and phenolic OH group were determined using density functional theory calculations, and the stability of different conformations was compared. Electron transfer-proton transfer was determined to be the dominant mechanism in the DPPH reaction with xanthorrhizol analogues, based on the correlation between the EC50 and ionisation potential. The radical cation was greatly stabilised in the structure where the side chain functional group was close to the aromatic ring. Stabilisation also depended on the phenolic OH group position. In future antioxidant design, aromatic ring substituent conversion and the use of functional groups far from the OH group or ring should be explored.

The influence of hydroxy groups on the adsorption of three-carbon alcohols on Ni(111), Pd(111) and Pt(111) surfaces: a density functional theory study within the D3 dispersion correction.

Experimentally, steric and inductive effects have been suggested as key parameters in the adsorption and reactivity of alcohols on transition-metal (TM) surfaces, however, our atomistic understanding of the behavior of alcohols in catalysis is far from satisfactory, in particular, due to the role of hydroxy groups in the adsorption properties of C3 alcohols on TM surfaces. In this study, we investigated those effects through ab initio calculations based on density functional theory employing a semilocal exchange-correlation functional within van der Waals corrections (the D3 framework) for the adsorption of C3 alcohols with different numbers and positions of OH groups, namely, propane, 1-propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol and glycerol, on the compact Ni(111), Pd(111) and Pt(111) surfaces. As expected, we found that the adsorption energy is affected by the number of hydroxy groups with similar values for each pair of regioisomers, which clearly indicates the effect of the number of OH groups. Based on Bader charge analysis, we found an effective charge transfer from the C3 molecules to the substrates, which can explain the reduction in the work function due to adsorption. Upon adsorption, the alpha carbon to the OH group closest to the surface and the central carbon are the most positively charged atoms, which increases the lability of their bonded H atoms. In addition, the depletion of electron density between the C-H and O-H bonds closer to the surfaces corroborated their stretching, suggesting that the proximity of the adsorbates to the surfaces affects the acidity of these H atoms, as well as inductive effects within the molecules.

Concentration dependences of IR absorption spectra in the range of stretching vibrations of OH groups of congruent lithium-niobate crystals doped with zinc and magnesium

The concentration behavior of the parameters of spectral lines that correspond to stretching vibrations of OH groups in the IR absorption spectra of LiNbO3:Zn (0.04–4.46 mol % ZnO) and LiNbO3:Mg (0.19–5.91 mol % MgO) crystals has been studied. It has been found that, in the range of threshold concentrations of Zn2+ and Mg2+ doping cations, the line parameters experience a jump. In this case, the widths of some lines decrease, which indicates the ordering of OH groups in the crystal. It has been shown that nonstoichiometric crystals are characterized by the occurrence of different positions of OH groups and different values of the quasi-elastic constants of O–H bonds in the crystal structure. In the stoichiometric LiNbO3 crystal, all the positions of OH groups are the same, and the quasi-elastic constants of O–H bonds are identical.

Studies of mixing properties of binary systems of di-n-butylamine with alkanols at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K

This article reports experimental density (ρ) and speed of sound (u) of binary mixtures containing di-n-butyl amine with 1-propanol, 1-butanol, 1-pentanol, 2-propanol over entire composition range at temperature ranging from 293.15K to 313.15K and at atmospheric pressure. Excess molar volume (VmE), excess isentropic compressibility (κsE), and deviation in speed of sound (uD) have been calculated using experimental densities and speeds of sound values at all temperatures. Along with these properties, apparent molar volume (Vφ,i), partial molar volume (V¯m,i), excess partial molar volume (V¯m,iE) and excess partial molar volume at infinite dilution (V¯m,iE,∞) have also been calculated. All the calculated excess properties are analyzed in terms of effect of chain length, position of OH group and effect of temperature on the intermolecular interactions. Redlich-Kister type polynomial is used to correlate the calculated excess and deviation properties to the composition. Correlation is done using method of least squares for the estimation of binary coefficients and standard errors. Further, PFP theory is also used to calculate VmE and have been compared with experimental results.

Investigation of the Electronic and pH-Sensing properties of Hydroxyl-Functionalized Imine-Linked Polymers via the UV-vis Absorption Spectra and the Density Functional Theory (DFT) Calculations

In this report, a synergetic computational and experimental studies were demonstrated on examples of poly-imine polymers; P(PI-IPI) and P(PIOH-IPI) to explore the role of hydroxyl substituent on their sensing and electronic properties. The polymer P(PIOH-IPI) bearing the OH-group on the ortho -position to the imine-bond, while the structure of the polymer P(PI-IPI) reveal the imine-bond only. The sensing property of the polymers was investigated via the UV-vis absorption in different solvents, acidic and basic solutions. Both polymers have shown significant sensing behavior in the acidic medium, while unpronounced behavior was noticed in the case of the polymer P(PI-IPI) in basic medium. Upon the incorporation of the OH-group, the polymer P(PIOH-IPI) has indistinguishable sensing behavior, a similar blue-shift in the acidic and basic medium, which can be attributed to the presence and the position of OH-group. The optical band gap of the polymers was determined experimentally and theoretically from the UV-vis absorption spectra and DFT calculations in the DMSO solvent. Other factors that affect the band gap values such as the structural conformation and length of conjugation were explored theoretically. In general, as the length of the optimized chain increased, the spectrum is red-shifted and the band gap decreased, which is attributed to the possible loss of chain planarity and conjugation beyond the monomer structure. Interestingly, the UV-vis spectra of the monomer-optimized structures were in a good match with the experimental UV-vis spectra. However, the band gap difference can be attributed to the method of band gap determination.

The coulometric approach to the superoxide scavenging activity determination: The case of porphyrin derivatives influence on oxygen electroreduction

The electrochemical and antioxidant properties of 5,10,15,20-tetrakis(3′-hydroxyphenyl)porphyrin ( H 2 T (m- OHPh ) P ) and 5,10,15,20-tetrakis(4′-hydroxyphenyl)porphyrin ( H 2 T (p- OHPh ) P ) were tested by the cyclic voltammetry (CV) method. It is shown that in dimethylsulfoxide (DMSO) the electroreduction processes of oxygen and porphyrins are under diffusion control. The electroreduction of H 2 T (m- OHPh ) P and H 2 T (p- OHPh ) P with potentials about -1 V are irreversible due to the chemical step (EC process) which leads to products with oxidation potentials about -0.5 V. Additionally in case of oxygen and porphyrin coreduction, both H 2 T (m- OHPh ) P and H 2 T (p- OHPh ) P influence the O 2•- electrosynthesis. The nonlinear dependence of the O 2•- peak current vs. porphyrin concentrations makes the available amperometric approach unsuitable for antioxidant activity estimation. To solve this problem, the coulometric parameters were calculated. The excellent linearity of the coulometric response of superoxide ion vs. porphyrins concentration was demonstrated for a wide concentration range. On the basis of coulometric responses, we constructed a parameter which separated the radical scavenging activity and variation of oxygen electroreduction. The superoxide scavenging activities of H 2 T (m- OHPh ) P and H 2 T (p- OHPh ) P were determined using the developed approach. The effect of OH group position on the superoxide scavenge activity is shown: H 2 T (p- OHPh ) P has a higher activity (slope = 0.75 L.mmol-1) than H 2 T (m- OHPh ) P (slope = 0.60 L.mmol-1).