Increasing Alkyl Chain Length Research Articles

Study ofn-Alkanethiol Self-Assembly Behavior on Iron Particles: Effect of Alkyl Chain Length and Adsorption Solvent on Resulting Iron-Based Magnetorheological Fluids

Self-assembled monolayers (SAMs) of organic molecules on metal surfaces are a type of inexpensive surface coating often used to improve metal substrate properties for sensors, electrochemistry, and nanofabrication applications. Iron, specifically, is one of the most commonly used metals, both as a pure metal and as an alloy due to its high conductivity, strong ferromagnetism, and low cost. However, magnetorheological fluids, which have shown impressive energy dampening in fields from civil infrastructure to biomedical devices utilizing iron dispersions, have suffered from low reliability and efficiency due to iron particle oxidation, corrosion, and settling. To understand the effect of self-assembled monolayers on iron and both the adsorbed particle's resistance against aggregation and performance impact, this work performs an in-depth study on alkanethiol-based self-assembled monolayers on iron particles. Adsorption of alkanethiols and the generation of SAMs on micron-sized iron particles were evaluated as a function of adsorption solvent polarity and alkanethiol chain length. Maximum alkanethiol loading, determined from appropriate isotherms, was found to strongly be a function of both parameters. Alkanethiol adsorption increased with increasing alkyl chain length and increasing solvent log P values in polar solvents. With respect to magnetorheologically relevant parameters, alkanethiol adsorption did not show any significant effect on both the magnetic properties of iron (as particles) and fluid on-state yield stress. The colloidal stability of n-alkanethiol adsorbed iron-based magnetorheological fluids (MRFs) was a function of both n-alkanethiol chain length and the iron particle adsorption solvent. MRFs composed of hexadecanethiol adsorbed iron prepared in polar solvents like methanol and ethanol showed excellent sedimentation stability compared to all other MRFs prepared in this study.

Effect of sodium alkyl sulfate chain length on foam stability: A molecular dynamics study

The alkyl chain length of surfactant plays an important role on its own performance. In this paper, the effect of sodium alkyl sulfate (SAS) with different alkyl chain lengths on the stability of foam film was studied by molecular dynamics (MD) method. The results showed that the increase of alkyl chain length enhances the interaction between SAS molecules, and increases the thickness of hydrated shell around the polar head. To investigate the effect of alkyl chain length on the drainage and rupture process of foam film, the steered molecular dynamics (SMD) study of foam liquid film with two external forces was also carried out. One external force is parallel to Z-axis and perpendicular to the liquid film, which can reflect the difficulty of foam drainage. The other is parallel to the horizontal direction of X-axis, which represents the stability of foam film. It was found that the longer the alkyl chain of SAS, the greater the external force required to destroy the foam surface. In addition, the free energy change profile of SAS from aqueous phase to SAS layer further indicates that the growth of alkyl chain can enhance the stability of foam film. This work aims to further understand the mechanism of foam film rupture and explore industrial methods to control foam stability.

(Invited) Effects of Halide Anion Type and Alkyl Chain Length on Hydrogen Bonding in Eutectic Solvent System

Deep eutectic solvent (DES), formed by the intermolecular hydrogen bonding between its components of an H–bond acceptor (HBA) and an H–bond donor (HBD), has been extensively studied in the area of material synthesis, catalysis, electrochemistry, etc. The properties of DES including melting point, color, density, viscosity, conductivity, etc. are closely related to the H-bond network. Establishing an understanding of the H-bond structure offers an opportunity to fine-tune these properties.Hence, in this study, we systematically investigated the effects of halide anion type and alkyl chain length on the hydrogen bond network of a series of eutectic solvent systems and attempted to establish an unambiguous H-bond correlation with the conductivity. We varied the halide anion from Cl− to I− (Cl−, Br−, I−) and the alkyl chain length from methyl to butyl (n c = 1, 2, 4), and performed FTIR and conductivity measurements. Results show that the OH stretching peak exhibits a blue shift with the halide anion varies in the order of Cl−, Br−, I− when compared with the neat ethylene glycol (Figure 1a), indicating an increase in H-bond strength. A similar trend can be found with the increasing alkyl chain length as well. A stronger H-bond network inhibits the mobility of these halide anions in the eutectic system, as a result, the conductivity will decrease as shown in Figure 1b. Further probing the H-bond network with ultrafast spectroscopy is currently underway. Figure 1. (a) FTIR spectrum of neat EG and TBAX:EG(1:10) sample, X= Cl−, Br−,I−. (b) Trend between the OH stretching peak shift (vs. neat EG) and conductivity of these investigated samples.AcknowledgememtsThis work was supported as part of the Breakthrough Electrolytes for Energy Storage (BEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0019409 Figure 1

Hydrophobic Material: Effect of Alkyl Chain Length on the Surface Roughness

The clean technologies of self-cleaning surfaces are expanding rapidly. Highly hydrophobic coatings with strong adhesion, high durability, and dirt-free surfaces have been prepared via sol-gel deposition of SiO2-TiO2-alkylsilane. The influence of the effects of the alkyl chain length of silane on surface roughness was investigated. This deposition involved a one-layer technique to produce the rough surfaces. The bimetal oxide of SiO2-TiO2 created a high level of surface roughness. As a result, the water contact angle of the coatings increased with the increasing alkyl chain length of silane (up to C=8). However, the water contact angle decreased when the C=16 of alkylsilane was applied. It was predicted that the longer alkyl chain would cause the molecules to collapse. The higher hydrophobicity was produced by SiO2-TiO2-OTMS coatings with a water contact angle of about 140.67 ± 1.23°. The effect of the dip-coating technique (one layer and layer-by-layer) on hydrophobicity was also discussed. The results showed that coatings produced by the one-layer technique had a higher contact angle than coatings made by the layer-by-layer technique. The coatings were stable under outdoor exposure and able to hinder dirt attachment to their surfaces.

Effect of ammonium hydroxide-based ionic liquids' freezing point and hydrogen bonding on suppression temperature of different gas hydrates

The study presents the effect of freezing point depression and hydrogen bonding energy interaction on four ammonium hydroxide-based ionic liquids (AHILs) of gas hydrate systems. The AHILs investigated are tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. The considered hydrate system includes methane (CH4), carbon dioxide (CO2), and three binary mixed gas hydrates (70-30 CO2 + CH4, 50-50 CO2 + CH4, 30–70 CO2 + CH4), which are often encountered in the flow assurance pipelines. The experimental temperature range is between 274.0 and 285.0 K, corresponding to pipeline pressures for different gas systems. The thermodynamic influence, i.e., average suppression temperature (ΔŦ) of the studied system, was reported for different mass concentrations (1, 5, and 10 wt%) and correlated with the freezing point depression and hydrogen bonding energy interaction of AHILs. The study also covers the structural impact of AHILs (in the form of alkyl chain variation) on the thermodynamic hydrate inhibition (THI) behaviour via freezing point and hydrogen bonding energy interactions. Findings revealed that the increased alkyl chain length of AHILs reduced the ΔŦ due to a decrease in hydrogen bonding ability. The highest THI inhibition (ΔŦ = 2.27 K) is attained from the lower alkyl chain AHIL, i.e., TMAOH (10 wt%) for the CO2 hydrate system. The freezing point depression of AHILs is a concentration-dependent phenomenon. Increased concentration of the AHILs in the system yielded lower freezing point temperature, positively influencing hydrate mitigation. Although the study provided the initial insight between the freezing point tendency and hydrogen bonding energies of AHILs on thermodynamic inhibition (ΔŦ). Based on the freezing point depression and hydrogen bonding energy interaction, a more generalized correlation should be developed to predict any potential ionic liquids regarded as promising hydrate inhibitors.

Structure effect in the demulsification performance of cationic surfactants

In this study, various cationic surfactants and MgO nanoparticles were used for dehydration of crude oil. The results of bottle tests exhibited that in demulsification of crude oil in the serious of alkyl trimethyl ammonium bromide homologs (CnTAB, n = 12, 14, and 16) with the increase of alkyl chain length, the optimum concentration level decreased and speed of dehydration decreased. Also, for surveying the role of head group, two cetrimonium bromide and cetylpyridinium bromide surfactants were used. Evaluation of the counter ion effect indicated in the high concentration of surfactants the counter ion can greatly influence the demulsification performance. Moreover, for enhancing demulsification, MgO nanoparticles were mixed with cetrimonium bromide (CTAB) surfactant. The mixture of MgO nanoparticles and CTAB (in ratio 1:3) could dehydrate crude oil in 300s. For better understanding of asphaltene-demulsifier interaction, was used the quantum calculation. The results demonstrate MgO interacts with asphaltene strongly.As well as the result of asphaltene adsorption on MgO indicate the asphaltene adsorption flow from Freundlich model. Finally, the interaction energy between surfactants or MgO and asphaltene were estimated by quantum calculation.

Quantum chemical calculations of formation enthalpies of cations and anions of ionic liquids

The development of advanced ionic-liquid-based applications requires accurate thermochemical data for both ionic liquids and their constituent ions. Herein, the formation enthalpies of alkylimidazolium cations ([CnMIm+], n = 2, 4, 6, 8, 10) and various anions (trifluoromethanesulfonate ([TfO−]), ethyl sulfate ([ES−]), dicyanamide ([DCA−]), and bis(trifluoromethane)sulfonylimide ([NTf2−])) in the ideal gas state were obtained by quantum chemical calculations using density functional theory (DFT: B3LYP, B98, M06, M06-2X) and composite (G4) thermochemical models in the framework of the isodesmic reaction approach. The enthalpies of heterolytic dissociation of neutral ion pairs (NIPs) for the [CnMIm+][X−] series (n = 2, 4, 6, 8, 10; X− = [TfO−], [ES−], [NTf2−], [DCA−], [BF4−], [PF6−], [Cl−], [Br−], [I−]) were derived using the obtained data and literature formation enthalpies (ΔfH°) of NIPs. Analysis of the thermochemical property trends revealed that the formation enthalpies of [CnMIm+] decrease linearly as the alkyl chain length increases. In addition, the use of the isodesmic reaction approach improved the reliability of the computed data. Furthermore, owing to its internal self-consistency, the G4 method was found to be the most appropriate for describing the thermodynamic quantities of the cations and anions of ionic liquids.

Recovery of Gold by Solvent Extraction and Direct Electrodeposition Using Phosphonium-Based Ionic Liquids

In this study, phosphonium-based ionic liquids (IL), i.e., triethyl-n-pentyl, triethyl-n-octyl, and triethyl-n-dodecyl phosphonium bis(trifluoromethyl-sulfonyl)amide, [P222X][NTf2], (X = 5, 8, and 12) were investigated for Au(III) extraction. The IL–Au complex was identified as [P2225][AuCl4] using UV–Vis–NIR and Raman spectroscopic analyses. Slope analyses with the concentration dependence of [P222X +] confirmed the anion-exchange mechanism of Au(III) extraction by [P222X +] (X = 5, 8, and 12). The enthalpy, entropy, and Gibbs free energy for Au(III) extraction were determined using thermodynamic analysis, indicating that lower temperatures had a positive effect on the Au(III) extraction. Electrochemical analysis revealed that extracted Au(III) can be reduced in two steps: (i) Au(III) + 2e− → Au(I), (ii) Au(I) + e− → Au(0)]. The diffusion coefficients of the extracted Au(III) species in [P222X][NTf2] (X = 5, 8, and 12) were evaluated from 323 to 373 K using semi-integral and semi-differential analyses. Because of the viscosity of the IL medium, the diffusion coefficient of the extracted Au(III) increases with increasing alkyl chain length. The 4f 7/2 spectrum based on X-ray photoelectron spectroscopy revealed that the Au electrodeposits obtained after 10 cycles of continuous extraction and electrodeposition were in the metallic state.

Insight into the physicochemical properties and bioactivities of therapeutic deep eutectic solvents based on matrine and fatty acids

• THEDESs based on matrine and fatty acids were developed. • Physicochemical properties of THEDESs were investigated. • Antibacterial and anti-cancer activities and cytotoxicity of THEDESs were studied. Deep eutectic solvents (DESs), as a new type of green solvent, have shown great advantages of easy preparation, no purification needed after synthesis and great potential for application in various fields. Recently, a new type of drug delivery system called therapeutic deep eutectic solvent (THEDES) was developed when combining active pharmaceutical ingredients (APIs) into DES. Herein, we have constructed a series of new THEDES based on matrine (API) and fatty acids. Their physicochemical properties and bioactivities were investigated. In a temperature range from 298.15 K to 338.15 K, both density and viscosity declined with the increasing temperature. Besides, the density of THEDES decreased with the increasing alkyl chain length of fatty acids due to the enhancement of free volume, while the alkyl chain length displayed no influence on the viscosity of THEDES. Moreover, THEDESs showed better antibacterial activity on S. aureus as compared with matrine and the mixture solution of matrine and fatty acids at the same concentration. THEDESs also displayed better cell antiproliferative activities and higher cytotoxicity than that of matrine. Therefore, the results presented herein provides important basis for the further applications of matrine in the form of THEDES.

Utilization of phosphonic acid compounds by marine bacteria of the genera Phaeobacter, Ruegeria, and Thalassospira (α-Proteobacteria).

Phosphonic acid (phosphonate) that possesses a carbon-phosphours bond is a chemically stable form of organic phosphorus. Various phosphonic acids are widely distributed in oceanic waters; in particular, methylphosphonic acid (namely methylphosphonate) is believed to be responsible for global methane production. To discuss the microbial degradation of phosphonic acids, we investigated the utilization of phosphonic acid compounds by cultures of marine bacteria, Phaeobacter sp., Ruegeria sp. (Rhodobacterales), and Thalassospira sp. (Rhodospirillales). These bacterial cultures were able to grow on methylphosphonic acid as well as on the tested alkyl-, carboxy-, aminoalkyl-, and hydroxyalkyl-phosphonic acid compounds. Cell yields and growth rates of Ruegeria and Thalassospira cultures grown on methyl-, ethyl-, propyl-, and butyl-phosphonic acid compounds tended to decrease with increasing alkyl chain length. In contrast, Phaeobacter sp. grew well on such alkyl-phosphonic acids. Our results suggest that these marine bacteria, which exhibit varied utilization, are involved in microbial degradation of various phosphonic acid compounds.

Ionic Liquids: Emerging Antimicrobial Agents.

Antimicrobial resistance has become a serious threat to global health. New antimicrobials are thus urgently needed. Ionic liquids (ILs), salts consisting of organic cations and anions with melting points less than 100°C, have been recently found to be promising in antimicrobial field as they may disrupt the bacterial wall and membrane and consequently lead to cell leakage and death. Different types of antimicrobial ILs are introduced in the review, including cationic, polymeric, and anionic ILs. Being the main type of the antimicrobial ILs, the review focuses on the structure and the antimicrobial mechanisms of cationic ILs. The quantitative structure-activity relationship (QSAR) models of the cationic ILs are also included. Increase in alkyl chain length and lipophilicity is beneficial to increase the antimicrobial effects of cationic ILs. Polymeric ILs are homopolymers of monomer ILs or copolymers of ILs and other monomers. They have great potential in the field of antibiotics as they provide stronger antimicrobial effects than the sum of the monomer ILs. Anionic ILs are composed of existing anionic antibiotics and organic cations, being capable to enhance the solubility and bioavailability of the original form. Nonetheless, the medical application of antimicrobial ILs is limited by the toxicity. The structural optimization aided by QSAR model and combination with existing antibiotics may provide a solution to this problem and expand the application range of ILs in antimicrobial field.

Surface Activity of Amines Provides Evidence for the Combined ESI Mechanism of Charge Reduction for Protein Complexes.

Charge reduction reactions are important for native mass spectrometry (nMS) because lower charge states help retain native-like conformations and preserve noncovalent interactions of protein complexes. While mechanisms of charge reduction reactions are not well understood, they are generally achieved through the addition of small molecules, such as polyamines, to traditional nMS buffers. Here, we present new evidence that surface-active, charge reducing reagents carry away excess charge from the droplet after being emitted due to Coulombic repulsion, thereby reducing the overall charge of the droplet. Furthermore, these processes are directly linked to two mechanisms for electrospray ionization, specifically the charge residue and ion evaporation models (CRM and IEM). Selected protein complexes were analyzed in solutions containing ammonium acetate and selected trialkylamines or diaminoalkanes of increasing alkyl chain lengths. Results show that amines with higher surface activity have increased propensities for promoting charge reduction of the protein ions. The electrospray ionization (ESI) emitter potential was also found to be a major contributing parameter to the prevalence of charge reduction; higher emitter potentials consistently coincided with lower average charge states among all protein complexes analyzed. These results offer experimental evidence for the mechanism of charge reduction in ESI and also provide insight into the final stages of the ESI and their impact on biological ions.

Thermodynamic analysis of nucleation of alcohol molecules with the varied alkyl chain length in nanoconfined solution

Combining the molecular dynamics (MD) simulations and the free-energy-based thermodynamic analysis, we analyze the role of alkyl chain length on the nucleation of alcohol molecules with the mono-hydroxyl in nanoconfined solution. The free energy formulae and thermodynamic equilibrium equation are parameterized by fitting the theoretical equilibrium equation to MD simulation results. We find that alcohol molecules with the varied alkyl chain length show different nucleation states, i.e., dispersion, reversible and aggregation states, corresponding to the total free energy Gconfine(n, N) with a single minimum at n∼ 1, two minima at n∼ 1 and N separated by a maximum, and a local minimum at n∼N, respectively. The alcohol molecule with a longer alkyl chain tends to aggregate into a cluster at a lower solute number in nanoconfined solution. Besides, the free energy of cluster formation in nanoconfined solution Gcluster(n) also depends on the alkyl chain length, and three regions can be identified: For the shorter alkyl chain, such as ethanol, there is no local maximum on Gcluster(n), indicating that alcohol molecules tend to be dispersed in water; For the intermediate alkyl chain length, such as 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol, the critical nucleation number nc and nucleation barrier Gb monotonically decrease with the increase of alkyl chain length; For the longer alkyl chain, nc∼ 1 and Gb∼0kBT suggest that alcohol molecules, such as 1-heptanol, can aggregate into clusters easily. Our work deepens the understanding of the alkyl chain length effect on the nucleation behavior of alcohol molecules in nanoconfined solution.

Effect of alkyl chain length on the antioxidant activity of alkylresorcinol homologs in low-moisture crackers

Alkylresorcinols (ARs) are a naturally occurring homologous series of phenolipids extracted from rye bran which have previously shown antioxidant activity in lipid-containing foods. This study extends previous work to consider their use in low-moisture foods using crackers as a model system. ARs (153 μmol) were capable of inhibiting lipid oxidation reactions based on the delayed generation of lipid hydroperoxides and headspace hexanal compared to a control treatment and were more effective than α-tocopherol which displayed prooxidant behavior. The antioxidant activity of ARs was observed to increase as a function of increasing alkyl chain length, with optimum activity at an alkyl chain length of C23:0; however, ARs were lost at a rate independent of alkyl chain length. A mixture of ARs displayed comparable antioxidant activity to the C23:0 and C25:0 homologs, all of which exerted stronger activity than butylated hydroxytoluene providing an effective alternative to synthetic antioxidants. These findings suggest that ARs are effective antioxidants in low-moisture foods likely because of their hydrophobicity, which allowed them to localize in the lipid phase, the purported site of lipid oxidation in the model cracker system.

Both alkyl chain length and V-amylose structure affect the structural and digestive stability of amylose-alkylresorcinols inclusion complexes

Alkylresorcinols (ARs) are a group of bioactive phenolic lipids and mostly concentrated in the bran of whole grains. In this study, the influences of alkyl chain length of ARs and V-amylose structure on the stability of V-amylose-ARs inclusion complexes were characterized. On the one hand, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and in vitro digestion studies of complexes showed that the crystallinity, thermo-stability, and digestion resistance of V-amylose-ARs inclusion complexes increased with increasing alkyl chain length of ARs. On the other hand, V6-amylose-ARs inclusion complexes displayed the strongest thermostability, the highest crystallinity, and the lowest digestibility compared to V7-amylose-ARs inclusion complexes and V8-amylose-ARs inclusion complexes. It could be concluded that both the helical structure of hydrated V6-amylose and ARs with longer alkyl chain stabilized the structure and stability of the inclusion complexes. This work could pave a way to develop bioactive cereal foods with high bioaccessibility of ARs.

Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry

Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n = 5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a γ-relaxation due to localized fluctuations as well as two glassy dynamics, the αcore- and αalkyl-relaxation, were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n = 8 from a rigid constrained (n = 5,6) to a softer system (n = 10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene-like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition.

Synthesis and properties of different alkyl alcohol polyethers as the defoamers for concrete

In this study, we report the synthesis and properties of different alkyl alcohol polyethers as the defoamers for concrete. A series of alkyl alcohol polyethers with the same ethylene oxide unit amount (8 EO) but different alkyl chain lengths (C14~22) were obtained. The surface activities and defoaming properties of them in aqueous solutions were studied. Using them as the concrete defoamers, the defoaming properties in both fresh and hardened cement mortars were investigated, and the structure-property relationships of the polyethers were fully discussed. The results indicate that the C14 polyether showed obvious air-entraining property and the C16~22 polyethers showed effective defoaming property. As the alkyl chain length increases, the HLB value of polyether decreases (hydrophobicity increases), and the defoaming effect of polyether increases in both solutions and mortars. The results also indicate that the polyether containing longer alkyl chain length improved the mechanical performance of the hardened mortar more effectively. The study found great potential of alkyl alcohol polyethers for the practical applications as high performance defoamers.

Complexation thermodynamics of UO22+/diglycolamide complex in a room temperature ionic liquid: A study by optical spectroscopy and microcalorimetry

Complexation thermodynamics of UO22+ and a series of N,N,N’,N’-tetraalkyl diglycolamide (TRDGA) ligands having alkyl chains –CH3 to –C6H13 were investigated in an ionic liquid (IL). The complexation constant for UO22+/DGA complex increased linearly with increasing alkyl chain length of DGA from tetramethyl (logβ1 = 4.52, logβ2 = 8.01) to tetrahexyl (logβ1 = 5.62, logβ2 = 10.3). There were two types of species recorded in the calorimetric titration for all the four ligands, one having endothermic complexation, and other exothermic. This observation was in contrast with those observed for aqueous medium, where both the stepwise complexation enthalpies were endothermic. The structural feature indicated the formation of [UO2L2]2+ type of complex without water or Tf2N− anion in the primary coordination sphere of the uranyl cation.

Delineating molecular interactions within surface active ionic liquids + tartrazine dye solutions: A comparative study with conventional surfactant-DTAC

Surface active ionic liquids (SAILs) have been used in various technological fields. Moreover, the deep understanding of interactions exist in SAIL and dye systems will enhance their utility in various fields. In this study, the interactions of cationic Ionic liquids/surfactant 1-Methyl-3-octylimidazoilum chloride [C8mim][Cl], 1-Methyl-3-decylimidazolium chloride[C10mim][Cl], Dodecyl trimethylammonium chloride (DTAC) with anionic dye tartrazine were investigated by state of the art techniques i.e., conductivity, UV–visible spectroscopy, fluorescence spectroscopy and surface tension. The Critical micelle concentration (CMC) of tartrazine-added aqueous ILs/surfactant solutions were obtained, and a decrease is observed after addition of dye. Further, with the increase in alkyl chain length of ILs, the CMC is considerably reduced. Spectroscopic studies reveal a change in spectra of dye which hints ILs/surfactant dye interaction. The binding constant (Kb) is calculated by conductivity, UV-visible, fluorescence methods, which follows the order DTAC>[C10mim][Cl]>[C8mim][Cl]. Computational studies give an idea of the HOMO – LUMO energy gap between the donor and acceptor orbitals of ILs/surfactant and dye, which can be useful in the prediction of the feasibility of interaction between two entities.

INVESTIGATION OF THE INFLUENCE OF THE SUBSTITUTE IN THE THIRD POSITION ON THE ELECTRONIC STRUCTURE OF 1,3-THIAZOLO[2,3-c][1,2,4]TRIAZOLE

Condensed 1,2,4-triazole derivatives exhibit a wide range of biological activity. In particular, triazolam, alprazolam and estazolam, which contain [1,2,4]triazolo[4,3-a][1,4]benzodiazepine system, are used as tranquilizers. Brotizolam is another tranquilizer, a derivative of thieno[3,2-f][1,2,4]triazolo [4,3-a][1,4]diazepine. The oral hypoglycemic drug sitagliptin contains the [1,2,4]triazolo[4,3-a]pyrazine system. In addition, pesticides such as flumetsulam, metosulam, cloransulam, diclosulam, florasulam, are derivatives of [1,2,4]triazolo[1,5-a]pyrimidine, [1,2,4]triazolo[1,5-c]pyrimidine and [1,2,4]triazolo[4,3-a]pyrimidine. Also, the search for anticancer drugs is based on the nucleus of 1,2,4-triazole. The popularity of the use of 1,2,4-triazole derivatives is primarily due to the high pharmacological action and relatively low toxicity of these compounds.
 The calculations were performed in the software package ORCA 4.2.1, by the method of density functional theory using the B3LYP/def2-TZVP method. After optimizing the geometry, to confirm the finding of the true local minimum, we calculated the matrix of the second derived energy from the coordinates of the atoms - in all cases, no imaginary frequencies were detected, indicating the finding of the true minimum. The magnetic characteristics of the compounds were calculated by the GIAO method. Using the method of density functional theory, the geometric and electronic structures of five compounds of the [1,3]thiazolo[2,3-c][1,2,4]triazole class were simulated, namely: unsubstituted [1,3]thiazolo[2,3-c][1,2,4]triazole, 3-methyl-[1,3]thiazolo[2,3-c][1,2,4]triazole, 3-ethyl-[1,3]thiazolo[2,3-c][1,2,4]triazole, 3-butyl-[1,3]thiazolo[2,3-c][1,2,4]triazole, 3-hexyl-[1,3]thiazolo[2,3-c][1,2,4]triazole. It is established that the length of the alkyl substituent in the third position has almost no effect on the shape and localization of the frontal molecular orbitals. In all cases, the isosurfaces are localized on the condensed system [1,3]thiazolo[2,3-c][1,2,4]triazole. The length of the alkyl substituent in the third position affects the ionization energy and electron affinity of [1,3]thiazolo[2,3-c][1,2,4]triazoles. Moreover, both the ionization energy and the electron affinity decrease with increasing alkyl chain length. The change in aromaticity with the change in the length of the alkyl substituent in the third position of the [1,3]thiazolo[2,3-c][1,2,4]triazole system is irregular, but the change is insignificant. It is established that both triazole and thiazole cycles are more aromatic than benzene, and the aromaticity of the triazole cycle is greater than thiazole.
 Keywords: 1,2,4-triazole; 1,3-thiazole, thiazolo[2,3-c][1,2,4]triazole, frontal molecular orbitals; aromaticity.