Increasing Alkyl Chain Length Research Articles

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.

Investigating bolalipids as solubilizing agents for poorly soluble drugs: Effects of alkyl chain length on solubilization and cytotoxicity

Synthetic single-chain bolalipids with symmetrical headgroups have shown potential in various pharmaceutical applications, such as the stabilization of liposome bilayers. Despite their amphiphilic character, synthetic bolalipids have not yet been investigated for their suitability as solubilizing agents for poorly soluble drug compounds. In this study, three synthetic single-chain bolalipids with increasing alkyl chain lengths (C22, C24 and C26) were investigated. All three bolalipids were able to achieve an increased solubility of the model drug, mefenamic acid, by approximately 180% in a pH 7.4 buffer compared to only a 102–105% increase achieved by sodium dodecyl sulfate (SDS) or the non-ionic surfactant pegylated hydroxystearate (PEG-HS). Subsequently, interfacial activity of bolalipids and their ability to destabilize liposomal bilayers were investigated. The C22 bolalipid exhibited a consistently lower interfacial activity, which was consistent with its significantly lower cytotoxicity in the macrophage-like cell line, J774. A1, compared to C24 and C26 counterparts. The mean IC50 values of the bolalipids tested (0.035–0.093 mM) were approximately 4–100-fold lower than that of SDS (0.401 mM) or PEG-HS (0.922 mM), with the mechanism of toxicity linked to increased cell membrane permeability, as is expected for surfactants. In summary, evidence from this study shows that decreasing the length of the bolalipid alkyl linker from C26 to C22 resulted in a significantly decreased cytotoxicity with no loss in drug solubilization efficiency.

Intercalation of montmorillonite with dialkylammonium cationic surfactants

Three montmorillonite (Mt) clays with different cation exchange capacity (CEC) were intercalated by a series of dialkyl ammonium cations with carbon numbers (Nc=) 8, 10, 12 and 18 in each alkyl chain. The intercalated clays were characterized by X-ray Diffraction, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy. The basal spacing of intercalated Mts increased gradually with increasing chain length. Interlayer arrangement of dialkyl surfactant cations in the intercalated clay gallery changed from flat bilayer to paraffinic and reached as high as 3.57 nm for the highest CEC clay intercalated with cations having Nc= 18 in each alkyl chain. For dialkylammonium intercalants, the increase in basal spacing was predominantly guided by the intercalant's structure and organic loading values lacked such direct correlation. Mt with low CEC showed large expansion in the clay interlayer with increasing alkyl chain length even with marginal increment in the organic loading. The highest basal spacing was observed always with the highest CEC clay for every intercalant irrespective of alkyl chain length. The wide expansion of clay gallery for the longest dialkyl intercalant in this series for all clays might be attributed to presence of intercalated surfactant molecules along with physically adsorbed surfactant cations in the clay interlayer. The change in conformations of intercalated dialkyl ammonium intercalants with increasing alkyl chain length was analyzed from FTIR study. With increasing alkyl chain length, methylene symmetric and asymmetric stretching frequency shifted to lower wavenumber for all Mt clays- which indicated greater ordered conformations obtained with increasing alkyl chain length.

Implementation of Artificial Neural Networks in the assessment of CO2 solubility in deep eutectic and ionic liquid solvents – Performance and cost comparison

In order to counteract the economic and environmental issues presented by Ionic Liquids (ILs) for carbon capture in post-combustion processes, Deep eutectic solvents (DESs) are being researched as potential absorbents. These are an emerging class of ILs that have a strong contribution from hydrogen bonding and have shown promising trends in CO 2 absorption in recent times. In this study, three hydrogen bond acceptors (HBA), along with 2-hydroxypropanoic acid (Lactic Acid (LA)) as the hydrogen bond donor (HBD), have been identified and analyzed as CO 2 absorbents. Considering their structural properties, thermodynamic behavior, and experimental conditions as input parameters, a backpropagation neural network (BPNN) has been implemented to analyze and predict the extent of CO 2 solubility within each of the DES mixtures. BPNN successfully predicted trends in the solubility as a function of the alkyl chain length, temperature, and pressure. It was observed that the solubility of CO 2 increased with increasing alkyl chain length and pressure but decreased with increasing values of temperature. DES is found to be more economical than other ionic liquid solvents used for CO 2 absorption.

Imidazolium-based ionic liquids with increasing alkyl chain length of cations decrease the stability and fibrillation propensity of lysozyme

Imidazolium ionic liquids with longer alkyl side chains show a larger destabilization effect on lysozyme. Increased hydrophobicity of the IL increases its binding affinity and inhibits the fibril formation of lysozyme.

Solubility of carbon dioxide in some imidazolium and pyridinium-based ionic liquids and correlation with NRTL model

In this study, the solubility of carbon dioxide gas in a series of 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids with various anions, viz. thiocyanate ([SCN]−), chloride ([Cl]−) and bromide ([Br]−) was investigated using a quartz crystal microbalance at 298.15 K and pressures up to 0.4 MPa. CO2 solubility in the ionic liquids correlates well with the non-random two-liquid (NRTL) model. The results indicate that the cation alkyl chain length and the type of anion have the main effects on the solubility of carbon dioxide in ionic liquids. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased with increasing alkyl chain length of the cation. Also, CO2 solubility was strongly dependent on the selection of the anion. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased as follows: [SCN]− > [Cl]− > [Br]−.

Effect of alkyl chain length on the corrosion inhibition of mild steel in a simulated hydrochloric acid medium by a phosphonium based inhibitor

The corrosion inhibiting effect of three synthesised phosphonium containing ionic liquids of varying alkyl chain length, namely, butyltriphenyl phosphonium bromide (BTPPB), hexyltriphenyl phosphonium bromide (HTPPB) and hexadecyltriphenyl phosphonium bromide (HDTPPB) on mild steel, was evaluated in 1 M HCl medium. The corrosion inhibition performance was studied by gravimetric method, potentiodynamic polarization studies, electrochemical impedance spectroscopy and quantum chemical studies (DFT). However, the results of the SEM, AFM and contact angle tests confirmed that the protective layer formed on the mild steel. Furthermore, assessed the theoretical calculations for exploring the inhibition mechanism. A maximum of 95.77% inhibition efficiency was achieved using 250 ppm of HDTPPB. The obtained results showed that HDTPPB has greater inhibition ability than BTPPB and HTPPB. Adsorption studies obeyed the Langmuir adsorption isotherm. Moreover, the increased alkyl chain length of ionic liquids did increase their inhibition efficiency.

Transition from antagonistic to synergistic interaction in mixed micellar system by increase in alkyl chain length of alkyl trimethylammonium bromide

Herein, the electrical conductivity technique used to measure the critical micelle concentration (cmc) for pure cationic surfactants (Dodecyl/cetyltrimethylammonium bromides) and phenothiazine drug (Promethazine hydrochloride), as well as their different mole fractions in 10−3 ​mol/kg 1-methyl-3-octylimidazolium chloride (C8mim.Cl) at different temperatures. By using the cmc values the regular solution theory used to evaluate the micellar mole fraction for DTAB/CTAB-PMT mixed systems. The clint's model used to calculate the ideal critical micelle concentration (cmc∗) that helps to evaluate the ideal micellar mole fraction for studied mixed systems, both explain the deviation from ideality. In addition, interaction parameter βm helps to confirm the nature of interaction (either antagonistic or synergistic) for the studied systems. The calculated parameters confirm a transition in the binding nature from antagonistic to synergistic with the increase in alkyl chain length of cationic surfactant i.e., component of the binary mixed system. The ease of micellization for the studied systems discussed by the standard Gibb's energy of micellization (ΔGm0), as well as the standard enthalpy and standard entropy of micellization were (ΔHm0) and (ΔSm0), respectively to discuss the stability of the studied systems.

Mechanism responsible for the reduction of interfacial tension by extended surfactants

The dynamic interfacial tensions (IFTs) of four extended surfactants (S-C12PO13S, L-C12PO4S, L-C16PO4S and L-C12PO11S) with different alkyl chain length and polypropylene oxide (PO) group against hydrocarbons were investigated. The mechanism responsible for the IFT reduction for extended surfactant has been detected. According to experimental results, we found that only when the size of hydrophobic part is enlarged to match the size of anionic head, the ultralow IFT will appear at optimized hydrophilic-lipophilic balance. For extended surfactants, with an increase of PO number, the curled PO chains occupy larger spaces at interface and match the size of anionic head. As a result, the ultralow IFT appears against alkanes when PO number is 13. The increase of alkyl chain length shows little effect on the size of hydrophobic part and ability of reducing IFT. Moreover, with an increase of n-alkane carbon number (ACN), the size of hydrophobic part increases as a function of ACN. Therefore, the increase of size of hydrophobic part compensates the decrease of adsorbed amount when ACN is higher than nmin value (the n-alkanes carbon number when the IFTs reach the minimum), which results in the “L” shape of IFT curve with a function of ACN.

Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent.

Two-dimensional infrared (2D-IR) spectroscopy is used to measure the spectral dynamics of the metal carbonyl complex cyclopentadienyl manganese tricarbonyl (CMT) in a series of linear alkyl nitriles. 2D-IR spectroscopy provides direct readout of solvation dynamics through spectral diffusion, probing the decay of frequency correlation induced by fluctuations of the solvent environment. 2D-IR simultaneously monitors intramolecular vibrational energy redistribution (IVR) among excited vibrations, which can also be influenced by the solvent through the spectral density rather than the dynamical friction underlying solvation. Here, we report that the CMT vibrational probe reveals solvent dependences in both the spectral diffusion and the IVR time scales, where each slows with increased alkyl chain length. In order to assess the degree to which solute-solvent interactions can be correlated with bulk solvent properties, we compared our results with low-frequency dynamics obtained from optical Kerr effect (OKE) spectroscopy-performed by others-on the same nitrile solvent series. We find excellent correlation between our spectral diffusion results and the orientational dynamics time scales from OKE. We also find a correlation between our IVR time scales and the amplitudes of the low-frequency spectral densities evaluated at the 90-cm-1 energy difference, corresponding to the gap between the two strong vibrational modes of the carbonyl probe. 2D-IR and OKE provide complementary perspectives on condensed phase dynamics, and these findings provide experimental evidence that at least at the level of dynamical correlations, some aspects of a solute vibrational dynamics can be inferred from properties of the solvent.

N-Butane, iso-Butane and 1-Butene Adsorption on Imidazolium-Based Ionic Liquids Studied with Molecular Beam Techniques.

The interaction of molecules, especially hydrocarbons, at the gas/ionic liquid (IL) surface plays a crucial role in supported IL catalysis. The dynamics of this process is investigated by measuring the trapping probabilities of n‐butane, iso‐butane and 1‐butene on a set of frozen 1‐alkyl‐3‐methylimidazolium‐based ILs [C n C1Im]X, where n=4, 8 and X−=Cl−, Br−, [PF6]− and [Tf2N]−. The decrease of the initial trapping probability with increasing surface temperature is used to determine the desorption energy of the hydrocarbons at the IL surfaces. It increases with increasing alkyl chain length n and decreasing anion size for the ILs studied. We attribute these effects to different degrees of alkyl chain surface enrichment, while interactions between the adsorbate and the anion do not play a significant role. The adsorption energy also depends on the adsorbing molecule: It decreases in the order n‐butane>1‐butene>iso‐butane, which can be explained by different dispersion interactions.

Experimental and DFT studies on foam performances of lauryl ether sulfate-based anionic surface active ionic liquids

Three lauryl ether sulfate-based anionic surface active ionic liquids (SAILs), 1-butyl-3-methylimidazolium lauryl ether sulfate ([Bmim][C12H25O(C2H4O)2SO3]), 1-hexyl-3-methylimidazolium lauryl ether sulfate ([Hmim][C12H25O(C2H4O)2SO3]), and 1-octyl-3-methylimidazolium lauryl ether sulfate ([Omim][C12H25O(C2H4O)2SO3]) were synthesized. Physicochemical properties (surface properties, micellization, adsorption, and aggregation parameters) of three anionic SAILs and sodium lauryl ether sulfate (SLES) were determined. The critical micelle concentration (CMC) values of [Bmim][C12H25O(C2H4O)2SO3], [Hmim][C12H25O(C2H4O)2SO3], and [Hmim][C12H25O(C2H4O)2SO3] (from surface tension) were 0.569 mmol/L, 0.361 mmol/L, and 0.190 mmol/L, respectively. Micellization of three SAILs were spontaneous, endothermic, and entropy-driven. Foaming performances (foaming ability, foam stability, and foam composite index) of three anionic SAILs and SLES were determined using Ross-Miles methods. The foaming abilities of three SAILs followed: [Hmim][C12H25O(C2H4O)2SO3] > [Bmim][C12H25O(C2H4O)2SO3] > [Omim][C12H25O(C2H4O)2SO3]. While the foam stabilities and foam composite index (FCI) of three SAILs followed: [Omim][C12H25O(C2H4O)2SO3] > [Hmim][C12H25O(C2H4O)2SO3] > [Bmim][C12H25O(C2H4O)2SO3]. The structure effect of SAILs on foam performances were analyzed using density functional theory (DFT) calculations. Binding energy values of three SAIL hydrates followed the trend: [Omim][C12H25O(C2H4O)2SO3](H2O)n > [Hmim][C12H25O(C2H4O)2SO3](H2O)n > [Bmim][C12H25O(C2H4O)2SO3](H2O)n. DFT results showed the increase of alkyl chain length of imidazolium cation was beneficial for the stability of SAIL hydrates, which resulted in higher foam performances. The information will shed light on screening of novel SAILs for surfactant foam enhanced oil recovery (EOR).

Molecular ordering dependent charge transport in [formula omitted]-stacked triphenylene based discotic liquid crystals and its correlation with dielectric properties

We investigate the charge transport in triphenylene core based homologous series of discotic mesogens (HATn) by the time-of-flight method. HAT5, HAT6 and HAT8 exhibit Colh phase whereas HAT4 shows Colhp phase. For the investigated homologous series, we have observed a single transit in the transient photocurrent curves corresponding to positive charge carriers having the mobility in order of 10-2 to 10-4 cm2/vs. The hole mobility decreases with increasing the number of carbon atoms (n) in the alkyl chain attached to the triphenylene core, which follows the empirical exponential relationship: μ≈a.exp(-b/n). Furthermore, the dielectric measurement has been done on these compounds to bring a correlation between the molecular ordering by varying the alkyl chain of the HATn compounds. In the light of structure-property correlation, we have noticed that the hole mobility and permittivity vary according to the length of alkyl chain attached to the triphenylene core. The molecular ordering is also discussed via phase behaviour of compounds and confirmed by polarized optical textures. The change in entropy also decreases with increasing alkyl chain length of the HATn compounds rendering an agreement with that of the mobility and dielectric measurements. The HATn compounds show their potential applications in opto-electronics and could serve as organic semiconductors; however, the poor conductivity remains as a futuristic challenge.

Effect of Alkyl Chain Length on the Photophysical, Photochemical, and Photobiological Properties of Ruthenium(II) Polypyridyl Complexes for Their Application as DNA-Targeting, Cellular-Imaging, and Light-Activated Therapeutic Agents.

A family of six Ru(II) polypyridyl complexes (1-6) which contain phenanthroline-based ligands functionalized with alkyl chains of different lengths (one methyl group, 10 and 21 carbon alkyl chains) and either 1,10-phenanthroline (phen) or 1,4,5,8-tetraazaphenanthrene (TAP) as ancillary ligands have been synthesized and characterized. The influence of the alkyl chain length on their photophysical and photochemical properties as well as in their photobiological applications has been elucidated by monitoring the changes in their MLCT-centered absorption and emission bands. The presence of one methyl group or 10 carbon alkyl chains does not seem to significantly affect the photophysical and photochemical properties of the resulting Ru(II) complexes when compared to the well-known [Ru(phen)3]2+ and [Ru(TAP)2phen]2+. However, an effect on their emission properties and in their ability to photosensitize singlet oxygen is observed for the Ru(II) complexes containing 21 carbon alkyl chains. The binding of these complexes to salmon testes DNA (stDNA) was investigated by observing the changes in the photophysical properties. Complexes 1, 2, 4, and 5 all showed changes in their MLCT bands that could be analyzed using conventional fitting methods, such as the Bard equation. In contrast, complexes 3 and 6, possessing long aliphatic chains, gave rise to nonclassic behavior. In addition to these analyses, both thermal denaturation and circular dichroism studies of 1-6 were carried out in the presence of stDNA which confirmed that these complexes bind to DNA. Confocal microscopy and viability studies in HeLa cervical cancer cells reveal an alkyl chain-length dependence on the cellular uptake and cytotoxicity of the resulting Ru(II) complexes due to an enhancement of their lipophilicity with increasing alkyl chain length. Thus, complexes containing 10 and 21 carbon alkyl chains are rapidly taken up into HeLa cells and, in particular, those with 21 carbon alkyl chains show a significant phototoxicity against the same cell line. Therefore, this study provides further insight into the possible modulation of the photophysical, photochemical, and photobiological properties of Ru(II) polypyridyl complexes by varying the length of the alkyl chains attached to the polypyridyl ligands coordinated to the Ru(II) center and the nature of the auxiliary groups, which we show has a significant effect on photophysical and biological properties.

Effect of alkyl chain length of imidazolium cations on foam properties of anionic surface active ionic liquids: Experimental and DFT studies

Two anionic surface active ionic liquids (SAILs), 1-hexyl-3-methylimidazolium dodecyl sulfate ([Hmim][C12H25SO4]) and 1-octyl-3-methylimidazolium dodecyl sulfate ([Omim][C12H25SO4]) were synthesized using imidazolium ionic liquids (ILs) and sodium dodecyl sulfate (SDS). The critical micelle concentration (CMC) values, thermodynamic properties, and aggregation parameters were determined using surface tension measurements, steady state fluorescence tests, and electrical conductivity measurements. CMC values (from surface tension) of [Hmim][C12H25SO4] and [Omim][C12H25SO4] were 1.075 mmol/L and 0.278 mmol/L, respectively. The micellization process of [Omim][C12H25SO4] and [Hmim][C12H25SO4] was spontaneous, endothermic, and entropy-driven. Foaming performances (foaming ability, foam stability, and foam composite index) of three SAILs ([Bmim][C12H25SO4], [Hmim][C12H25SO4], and [Omim][C12H25SO4]) were determined using Ross-Miles methods. The foaming abilities of SAILs followed the order: [Hmim][C12H25SO4] > [Bmim][C12H25SO4] > [Omim][C12H25SO4]. While the foam stabilities and foam composite index (FCI) of SAILs followed the order: [Omim][C12H25SO4] > [Hmim][C12H25SO4] > [Bmim][C12H25SO4]. The structure effect of three SAILs ([Bmim][C12H25SO4], [Hmim][C12H25SO4], and [Omim][C12H25SO4]) on foam performances were analyzed by density functional theory (DFT) calculations. Binding energy of three SAIL hydrates followed the trend: [Omim][C12H25SO4](H2O)n > [Hmim][C12H25SO4](H2O)n > [Bmim][C12H25SO4](H2O)n. DFT results showed the increase of alkyl chain length of imidazolium cation was beneficial to the stability of SAIL hydrates, which resulted in higher foam performances. The information will shed light on rapid screening of novel surface active ionic liquids for surfactant foam enhanced remediation (SFER).