Ab Initio Calculations, Preferential Solvation, and Investigation of

Article pubs.acs.org/jced

Surfactant Binary Systems: Ab Initio Calculations, Preferential Solvation, and Investigation of Solvatochromic Parameters Mona Kohantorabi, Hadi Salari,* Mostafa Fakhraee, and Mohammad Reza Gholami* Department of Chemistry, Sharif University of Technology, Tehran 11365-11155, Iran ABSTRACT: Solvatochromic UV−vis shifts of three probes 4-nitroaniline, 4-nitroanisol, and Reichardt’s dye in binary mixtures of polyethylene glycol p-(1,1,3,3tetramethylbutyl)-phenyl ether (Triton X-100 or TX-100) with methanol, ethanol, 1propanol, and water have been investigated at 298 K. Structural and intermolecular interactions of solvatochromic probes were determined in these systems. Solvatochromic parameters, including normalized polarity (ENT ), dipolarity-polarizability (π*), hydrogenbond donor (α), and hydrogen-bond acceptor (β) abilities, were measured at a wide range of mole fraction (0 ≤ X ≤ 1) with 0.1 increment. Interestingly, a similar behavior of ENT and α is observed in alcohols/TX-100 mixtures. The ENT parameters obtained from absorbance of Reichardt’s dye within various mixtures of surfactant were observed to be lower than predicted values from ideal additive behavior. A negative deviation from ideality is shown by ENT parameter in all alcohols/TX-100 mixtures, while a fluctuated behavior for other probes can be seen. The optimized geometries exhibit that the hydroxyl (−OH) group on the side chain of TX-100 significantly affects the arrangement of the selected solvents around TX-100. All binary systems show complex behavior for chosen probes. The results demonstrate that 4-nitroanisole and Reichardt’s dye have stronger interactions with binary mixtures of alcohols/TX-100 systems. Synergistic solvation behavior for water/TX-100 was observed. Preferential solvation model was applied for the first time in the surfactant binary mixtures and from this model information solute−solvent and solvent−solvent interactions were interpreted. Preferential solvation (specific solute−solvent interactions) or the solvent−solvent interaction is the reason for deviation from ideal behavior of probes. As a main result, alkyl chain length of alcoholic solvents does not have impressive effects on predicted trends of solvatochromic parameters. Ab initio calculations of solvents/TX-100 mixtures demonstrate the following trend for magnitude order of interactions: water > methanol > ethanol >1-propanol. Electrostatic potential map is another confident evidence for predicted order.

1. INTRODUCTION

implementation of their binary mixtures in order to produce microemulsions.9 Diverse interactions in mixed solvents are more complex than in pure solvents when the solute is surrounded preferentially by the mixture of components or the complex that is formed by the interaction of both components. The strong negative Gibbs energy of solvation is the main result of such arrangement.10,11 A profound understanding of solute− solvent interactions is required to achieve more information regarding periphery behavior of the solvation in chemical processes. Indeed, solvatochromism is an appropriate and simple method for perusing solute−solvent interactions that exhibit the specific and nonspecific solute−solvent interactions.12,13 Solvatochromism is dependent on the electronic spectrum of solutes. Intensity, position, and the shape of absorption bands of dissolved chromophores are remarkably influenced by the choice of different solvents due to the different stabilization of their electronic ground and excited states. Solvatochromic dyes indicate significant shifts in absorption wavelength when dissolved in the different

Surfactants are amphiphilic compounds that can reduce surface and interfacial tensions by virtue of the cumulative and increase the solubility, mobility, and pursuant biodegradation of hydrophobic or organic compounds.1,2 In the formulation of technical processes, such as wetting, foaming, solubilization, and detergency, surfactants are the principal components. Surfactants can be classified by their chemical structures such as cationic, anionic, or nonionic.3,4 Nonionic surfactants, which is the target in this study, do not have any electrical charges. The hydrophilic part in nonionic surfactants contain the derivatives of polyoxyethylene, polyoxypropylene, or polyol. Solution properties of nonionic surfactants are significantly different from those of the ionic surfactants.5 Moreover, the nonionic surfactants have less sensitivity than the ionic surfactants. Also, the binary mixtures of nonionic surfactant separate to two phases when exposed to heat-treatment. The temperature that phase separation occurs is called the cloud point (CP) temperature.6,7 The micellar properties of nonionic surfactants, such as the critical micelle concentration (CMC), the micelle aggregation number, and liquid−liquid equilibrium, can be altered in the presence of solutes.8 In addition, alcohols hold a special place among additives to surfactant solutions due to © XXXX American Chemical Society

Received: June 23, 2015 Accepted: November 16, 2015

A

DOI: 10.1021/acs.jced.5b00522 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Figure 1. ESP of selected molecule in which blue color is the area with the lowest negative charge and red color shows the region with the highest negative charge.

solvents.14,15 polyethylene glycol p-(1,1,3,3-tetramethylbutyl)phenyl ether (Triton X-100 or TX-100) is a nonionic surfactant with extensive application, which forms a hydrophilic poly(ethylene oxide) chain and aromatic hydrocarbon hydrophobic group. High-purity, moderate foaming properties and solubility in water at 298 K makes it compatible with ionic surfactants. TX-100 is a suitable wetting agent with a CMC of 106−160 mg/L.16,17 Solvatochromic parameters, α, β, and π* were introduced by Kamlet−Taft for homogeneous media. The obtained values of these parameters can be used as a criterion to describe three basic modes of interaction in homogeneous media.18 In the present work, after checking the charge distribution on the TX-100 and four molecular solvents such as methanol, ethanol, 1-propanol, and water, two most stable geometries of their mixtures were optimized and the interaction energies for these mixtures were calculated. Four solvatochromic parameters (ENT , normalized solvent polarity parameter; π*, dipolarity/ polariability; β, hydrogen-bond acceptor (HBA) basicity; α, hydrogen-bond donor (HBD) acidity) were measured in aforesaid mixtures. Furthermore, in order to obtain more details of the nonideal behavior of the selected mixtures and prediction of their binary features, the preferential solvation model was applied for analyzing solvents interactions in these mixtures. To the authors’ knowledge, this is the first estimation of Kamlet−Taft parameters for these mixtures.

minimum through the frequency calculations to ensure the absence of imaginary frequencies. 2.2. Experimental Section. 2.2.1. Materials. 4-Nitroanisol and 4-nitroaniline (Merck, 99%) were recrystallized from water/ethanol and water/acetone, respectively. 2,6-Diphenyl-4(2, 4, 6-triphenylpyridinium-1-yl) phenolate (Reichardt’s dye 30) was obtained from Aldrich (>99%). Polyethylene glycol p(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100), methanol, ethanol, and 1-propanol were purchased from Merck. 2.2.2. Experimental Methods. UV−vis spectroscopic analysis was performed at 298 K in GBC UV−vis Cintra 40 spectrophotometers, a pair of quartz analytical cells of 1 cm path length were used in all measurements, and temperature was controlled. The mixtures of TX-100 with molecular solvents (methanol, ethanol, 1-propanol, and water) were carefully prepared by mass in an accuracy balance with an uncertainty in mass of ±0.1 mg. All indicator stock solution was prepared in ethanol and stored in dark glass at ∼4 °C. An appropriate amount of the indicator solution from the stock was transferred to the quartz cuvette, and its solution was evaporated by vacuum. Each solvatochromic probe was dissolved in the mixtures, the concentration was adjusted to 1 × 10−4 mol dm−3, and then the solution was stirred with a magnetic stirrer.

3. RESULTS AND DISCUSSION 3.1. Ab Initio Results. 3.1.1. Electrostatic Potential Map (ESP). ESP of each isolated molecule was computed at B3LYP/ 6-311++G(d,p) level of theory.20,21 Figure 1 demonstrates a conventional color pattern of ESP in which blue color is a region with the lowest negative charge and red color shows the area with the highest negative charge. As can be seen from Figure 1, the most value of charge separation is attributed to the water molecule, followed by TX-100, and the lowest corresponding value belongs to the 1-propanol molecule. Consequently, it can be predicted that the strongest

2. METHODS 2.1. Ab Initio Calculations. In order to gain a first insight into the orientation patterns of chosen solvents around Triton X-100 (TX-100), each target mixture was optimized at the B3LYP/6-311++G(d,p) level of theory using the Gaussian 03 package of programs.19 In this regard, the two most stable configurations of TX-100/solvents mixtures were examined. Each optimized structure was also checked to be a true local B



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Figure 2. Most stable configurations of solvent/Triton X-100 mixtures, calculated at B3LYP/6-311++G(d,p) theoretical level. The hydrogen bonds are shown by dot line and distances are in angstrom. The interaction energies are labeled under each configuration.

interactions are ascribed to the water/TX-100 mixtures, followed by methanol/TX-100, and the weakest interactions are attributed to the 1-propanol/TX-100 mixtures. 3.1.2. Interaction Energies. Two most stable geometries were optimized at B3LYP/6-311++G(d,p) level of theory with their interaction energies are exhibited in Figure 2. The basis set super position error (BSSE)22,23 of optimized structures was removed by using the counterpoise correction.24 The optimized geometries (Figure 2) exhibit that the hydroxyl (−OH) group on the side chain of TX-100 significantly effects on the solvents/TX-100 arrangement. As it can be seen from Figure 2, the highest interaction energy between solvents and TX-100 is related to the water/TX-100 mixture. Steric hindrance of larger solvent, especially in 1-propanol, seems to be responsible for the reduction in their interaction energies. 3.2. Experimental Results. 3.2.1. Water/TX-100 Mixtures. Four solvatochromic parameters (SP) have been measured at 298 K over the whole range of solvents by UV−vis absorption spectra. The ET (30) parameter was normalized by using of two reference solvents: tetramethylsilane (TMS) with (ENT = 0) and water (ENT = 1). Behavior of ENT (Dimorth−Reichardt polarity) is strongly affected by HBD acidity of solvent.25−28 The relationship between solvatochromic parameters and experimental values are demonstrated in eqs 1−4 in which νB, νANI, and νANS are the maximum wavenumbers of betaine dye, 4nitroaniline, and 4-nitroanisole, respectively, based on kilo Kaser (kK) unit, where 1 kK = 103 cm−1.29,30 α = 0.186(10.91 − νB) − 0.72π *

(1)

31.10 − 3.14π * − νANI 2.79

(2)

β=

π* =

34.12 − ν ANS = 0.427(34.12 − νANS) 2.343

E TN =

E T(Solvent) − E T(TMS) E (Solvent) − 30.7 = T E T(Water) − E T(TMS) 32.4 (4)

Actually, the α and β parameters are criteria of specific solute− solvent interaction. To be more precise, β parameter is related to the HBA basicity characteristics of the solvent, while α parameter depends to the solvent’s HBD acidity characteristics.31,32 The π* parameter is a scale of solvent dipolarity/ polarizability that can be utilized for computing all nonspecific solute−solvent interactions.33 The O−H group in TX-100 can act as HBD and HBA. Poly(ethylene oxide) chain in hydrophilic group can be participating as HBA. The β-value in TX-100 is greater than α. These values indicate the high acceptor power of TX-100. α and β parameters in water/TX-100 mixtures would diminish by the addition of water to TX-100 in initial mole fraction, while at the higher mole fraction these parameters increase moderately (Table 1). The α-parameter exhibits a negative deviation from Table 1. Solvatochromic Parameters for Binary Mixtures of Water with Triton X-100

(3) C

XWater

α

β

π*

ENT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.31 0.28 0.27 0.35 0.34 0.39 0.39 0.41 0.49 0.59 1.30

0.57 0.55 0.52 0.62 0.60 0.65 0.62 0.59 0.67 0.63 0.49

0.87 0.90 0.93 0.87 0.88 0.87 0.88 0.91 0.87 0.88 1.08

0.46 0.46 0.46 0.48 0.48 0.50 0.51 0.52 0.55 0.60 1.00



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Figure 3. SP and excess solvatochromic parameters (SPE) versus XWater for water/TX-100 mixtures. (A) α, (B) β, (C) π*, and (D) ENT .

Figure 4. SP and SPE versus XMethanol for methanol/TX-100 mixtures. (A) α, (B) β, (C) π*, and (D) ENT .

for diphenyl ether to λmax∼ 453 nm for water.25,34,35 Because of low solubility of Richardt’s dye in water, ET (30) or ENT could not be measured in pure water; for this reason, the literature value was used.36 The ENT parameter is a blend of dipolarity/ polarizability and HBD acidity of the media. Interestingly, an ascending trend of ENT and α-values can be observed by increasing the mole fraction of water, which was previously confirmed by the yielded results of ESP and also interaction energies of this mixture.

ideal behavior with a minimum in XWater = 0.9. A positive deviation from ideality is observed for β-parameters. In water/ TX-100, the β-values confirm solvent−solvent interactions and synergetic effect in this media that is related to hydrogen bonding interactions between water and TX-100. This effect leads to a complex structure production that has higher hydrogen-bond acceptor ability. The π* values show the same deviation that has a negative deviation (0.3 < XWater < 0.9) from ideality (Figure 3). Reichardt’s dye (30) exhibits an unusually high solvatochromic absorbance band shift from λmax ∼ 810 nm D



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3.2.2. Methanol/TX-100 Mixtures. Notably, α-value of pure TX-100 is significantly lower than this parameter in neat methanol. This may be caused by the higher steric hindrances of voluminous side chains in TX-100. By addition of methanol to TX-100, α and ENT parameters increased (Figure 4A,D) with a negative deviation from ideality (Table 2), highlighting the

solvated by the two components of the binary systems and therefore “preferential solvation” of the probe is observed. 3.2.3. Ethanol/TX-100 Mixtures. By adding ethanol to TX100, α-parameter was enhanced with a negative deviation from ideal behavior (Figure 5A). The β-values (Table 3) in initial Table 3. Solvatochromic Parameters for Binary Mixtures of Ethanol with Triton X-100

Table 2. Solvatochromic Parameters for Binary Mixtures of Methanol with Triton X-100 XMethanol

α

β

π*

ENT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.31 0.32 0.33 0.37 0.43 0.50 0.54 0.59 0.67 0.83 1.17

0.57 0.57 0.56 0.55 0.57 0.59 0.59 0.58 0.60 0.65 0.84

0.87 0.86 0.88 0.88 0.89 0.86 0.88 0.86 0.84 0.80 0.55

0.46 0.46 0.48 0.50 0.53 0.55 0.57 0.60 0.62 0.69 0.76

XEthanol

α

β

π*

ENT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.31 0.31 0.34 0.35 0.43 0.48 0.46 0.54 0.61 0.66 0.98

0.57 0.57 0.58 0.57 0.62 0.66 0.56 0.60 0.62 0.62 0.90

0.87 0.86 0.86 0.88 0.84 0.80 0.87 0.83 0.80 0.82 0.54

0.46 0.46 0.48 0.48 0.51 0.52 0.53 0.56 0.58 0.61 0.67

mole fraction are invariant with a negative deviation from ideal behavior. The positive deviation from ideality can be viewed for π* in this mixture. To be more precise, the maximum change for the corresponding parameter is centered at 0.6 < XEthanol < 1. The same behavior of Reichardt’s dye in methanol/TX-100 is also seen for ethanol/TX-100 mixtures. The ENT parameter gradually increased with increasing mole fraction of ethanol. Interestingly, a direct relation between ENT and α in this mixture can be observed. 3.2.4. 1-Propanol/TX-100 Mixtures. Figure 6 depicts the variations of solvatochromic parameters in 1-propanol/TX-100 mixtures. Numerical values of Figure 6 are summarized in Table 4. By addition of 1-propanol to TX-100, ENT values linearly increased with slight deviation from ideality (Figure 6D). This behavior is due to the weak interaction between two

strong H bond formation between two compounds. In initial mole fraction (0 ≤ XMethanol ≤ 0.4), β-parameter value is constant. The −OH site on methanol is stronger in HBA ability than the corresponding site on TX-100, whereas with increasing of methanol (0.6 ≤ XMethanol ≤ 1), β-parameter increased smoothly with a negative deviation from ideality (Figure 4B). Eventually, the π* parameter for this mixture is slightly constant (Figure 4C) with a positive deviation from ideality. Ideal mixtures have a linear relationship between the solvatochromic parameters and the solvent composition when the solvatochromic probe is equally solvated by two constituents of the solvent mixture. In regard to the predicted results, it can be concluded that the probe is not equally

Figure 5. SP and SPE versus XEthanol for ethanol/TX-100 mixtures. (A) α, (B) β, (C) π*, and (D) ENT . E



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Figure 6. SP and SPE versus X1‑Propanol for 1-propanol/TX-100 mixtures. (A) α, (B) β, (C) π*, and (D) ENT .

mixtures40−44 that include experimental studies based on thermodynamic, NMR, IR, and UV−vis measurements.45−51 Becausee of the simplicity of UV−vis method, it has attracted the most attention of experimental scientist. The preferential solvation model was developed by Skwierczynsi et al. and later extended by Bosch and Roses.52,53 This model is based on a two-step process, represented by the given formula (eqs 5 and 6)

Table 4. Solvatochromic Parameters for Binary Mixtures of 1-Propanol with Triton X-100 X1‑Propanol

α

β

π*

ENT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.31 0.31 0.33 0.38 0.41 0.50 0.47 0.55 0.56 0.66 0.84

0.57 0.57 0.57 0.61 0.60 0.66 0.58 0.60 0.58 0.72 0.95

0.87 0.88 0.88 0.85 0.86 0.83 0.86 0.85 0.88 0.71 0.59

0.46 0.46 0.48 0.49 0.51 0.54 0.54 0.57 0.59 0.57 0.62

I(S1)2 + IS 2 ↔ I(S 2)2 + 2S1

(5)

I(S1)2 + S 2 ↔ I(S12)2 + S1

(6)

Where I represent the indicator, S1 and S2 refer to the pure solvents, and S12 is utilized for the mixed solvents. I (S1) exhibits the indicator fully solvated by the S1 solvent, I (S2) exhibits the indicator fully solvated by the S2 solvent, and I (S12) exhibits the indicator fully solvated by the S12 solvent. Equation 5 shows the total exchange of solvent 1 by solvent 2 in the solvation sphere of the indicator, and eq 6 indicates the exchange with the mixed solvents. The equilibrium constants, f 2/1 and f12/1, which are attributed to eq 5 and eq 6, respectively, can be evaluated by the following expressions (eqs 7−10)

compounds that was previously proved by ab initio results (Figure 2). In this mixture, α-parameter indicates increasing behavior with negative deviation from ideality, whereas βparameter is nearly held constant. In initial mole fraction of 1propanol, the π* parameter is nearly fixed and maximum variations were observed in 0.8 < X1‑Propanol < 1. The ascending behavior of measured ENT parameter in methanol/TX-100 and ethanol/TX-100 can be explained by the stronger interaction energies of these mixtures than 1propanol/TX-100 mixture (Figure 2). This result is in excellent agreement with the yielded findings of ESP. As a main result, alkyl chain length of alcoholic solvents does not remarkable effect on the predicted trends of solvatochromic parameters in this study. 3.3. Preferential Solvation. Solutes can preferentially interact with one solvent or mixed solvents in their solvation sphere. This phenomenon is known as preferential solvation.37,38 The preferential solvation is an appropriate and easy method for studying solvent−solvent and solute−solvent interactions in which these interactions can explicate many equilibrium and kinetic phenomena.25−28,39 This approach is a widely used method for investigating the binary solvent

f2/1 =

f12/1 =

f12/2 =

x 2s x1s x 20

2

( ) x10

(7)

s x12 x1s x 20 x10

(8)

f12/1 f2/1

(9)

xsi

where is the mole fraction of the solvent I in the solvation sphere of the indicator and x0i indicates the bulk mole fraction. F



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Table 5. Parameters and Standard Deviation Obtained by Application of the Preferential Solvation Model solvents

Y1

Y2

Y12

f 2/1

f12/1

f12/2

N

R2

K

σ

water/TX-100 methanol/TX-100 ethanol/TX-100 1-propanol/TX-100 water/TX-100 methanol/TX-100 ethanol/TX-100 1-propanol/TX-100 water/TX-100 methanol/TX-100 ethanol/TX-100 1-propanol/TX-100

32.06 32.08 32.06 32.05 26.78 26.79 26.77 26.78 15.90 15.92 15.93 15.99

31.58 32.84 32.86 32.74 26.35 27.02 26.85 26.58 22.07 19.34 18.28 17.62

32.01 32.02 32.22 33.50 26.54 26.71 27.25 26.67 16.22 16.24 16.19 15.73

8.69 0.17 0.008 0.07 0.03 0.08 7.88 0.07 0.17 1.27 1.24 3.07

113.811 2.83 1.33 0.12 2.23 1.95 2.76 3.93 4.56 4.8 3.92 3.06

13.09 16.64 166.25 1.71 74.33 24.37 0.35 56.14 26.82 3.77 3.16 0.99

11 11 11 11 11 11 11 11 11 11 11 11

0.92 0.99 0.94 0.96 0.92 0.88 0.8 0.8 0.99 0.99 0.99 0.97

1.75 −0.41 −0.64 −2.42 0.18 −0.23 −1.29 2.75 −0.84 1.12 0.14 0.84

0.00322 0.00087 0.00516 0.00337 0.00249 0.00169 0.00079 0.0018 0.01063 0.01506 0.00775 0.02133

indicator 4-nitroanisole

4-nitroaniline

Reichardt’s dye

Thus, the solvatochromic mixture property (Y12) can be computed from those of pure solvents (Y1 and Y2) according to eq 10 Y=

Y1(1 − x 20)2 + Y2f2/1 (x 20)2 + Y12f12/1 (1 − x 20)x 20 (1 − x 20)2 + f2/1 (x 20)2 + f12/1 (1 − x 20)x 20 (10)

The model was corrected with ΔY term, as follows (eq 11):

ΔY =

⎡ Kf2/1 (x 20)2 ⎢(1 − x 20)2 + ⎣ [(1 −

x 20)2

+

f2/1 (x 20)2

f12/1 (1 − x 20)x 20 ⎤ 2

+ f12/1 (1 −

⎥⎦

x 20)x 20)]2 Figure 8. Maximum wavenumber of indicators’ absorbance in methanol/TX-100 mixtures. Reichardt’s dye (■), 4-nitroaniline (▲), and 4-nitroanisole (●).

(11)

where K is a proportionality constant. The wave numbers have been fitted to the proposed eq 10 and the parameters obtained are given in Table 5. Four binary systems expose a complex behavior for all three indicators. The obtained results from preferential solvation method for 4-nitroanisole show a descending behavior in water/TX-100 mixture and an ascending behavior in methanol/TX-100, ethanol/TX-100, and 1-propanol/TX-100 mixtures (Figures 7−10). The gained findings of preferential solvation indicate that the maximum values of 4-nitroanisole absorption in pure solvents are similar for all selected molecular solvents. According to the preferential solvation model, the observed maximum absorption is of the order ethanol ≈ methanol >1-

Figure 9. Maximum wavenumber of indicators’ absorbance in ethanol/ TX-100 mixtures. Reichardt’s dye (■), 4-nitroaniline (▲), and 4Nitroanisole (●).

propanol > water and for the mixed solvents of the order: 1propanol/TX-100 > ethanol/TX-100 > methanol/TX-100 ≈ water/TX-100. The Y12 value of mixed methanol/TX-100 is lower than Y1 and Y2 values; therefore the polarity/polarizability for this mixture is stronger compare to neat methanol and TX-100. The low value of f 2/1 parameter for 4-nitroanisole in alcohols/TX100 indicates that solvation does not occur preferentially. Likewise, preferential solvation can be easily comprehended from the f12/1 and f12/2 parameters in these mixtures. The 4-nitroaniline is preferentially solvated by ethanol in ethanol/TX-100 mixtures, while the high f12/1 and f12/2 values in

Figure 7. Maximum wavenumber of indicators’ absorbance in water/ TX-100 mixtures. Reichardt’s dye (■), 4-nitroaniline (▲), and 4nitroanisole (●). Continuous lines calculated using eq 11 from the SP in these mixtures. G



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are also confirmed by the predicted results from the preferential solvation model.

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Tel: +98 216 616 5314. Fax: +98 216 600 5718. *E-mail: [email protected]. Tel: +98 216 616 5314. Fax: +98 216 600 5718. Notes

The authors declare no competing financial interest.

■

Figure 10. Maximum wavenumber of indicators’ absorbance in 1propanol/TX-100 mixtures. Reichardt’s dye (■), 4-nitroaniline (▲), and 4-nitroanisole (●).

REFERENCES

(1) Singh, A.; Van Hamme, J. D.; Ward, O. P. Surfactants in microbiology and biotechnology: Part 2. Application aspects. Biotechnol. Adv. 2007, 25, 99−121. (2) Abu-Ghunmi, L.; Badawi, M.; Fayyad, M. Fate of Triton X-100 application on water and soil enviroments: A review. J. Surfactants Deterg. 2014, 17, 833−838. (3) Tadros, T. Applied Surfactants: Principles and Application; WileyVCH: Verlag GmbH, 2005. (4) Rosen, M. J.; Kunjappu, J. T. Surfactant and Interfacial Phenomena; Wiley-VCH: Verlag GmbH, 2012. (5) Manisha Mishra, P.; Muthuprasanna, K.; Surya prabha, P.; Sobhita rani, I.; Satisbbabu, I.; Sarathchandiran, G.; Arunachalam; Shalini, S. Basic and potential applications of surfactants-a review. Int. J. Pharm. Technol. 2009, 1, 1354−1365. (6) Gu, T.; Galera-Gomez, P. A. The effect of different alcohols and other polar organic additives on the cloud point of Triton X-100 in water. Colloids Surf., A 1999, 147, 365−370. (7) Mustafina, A. R.; Elistratora, J. G.; Bochkora, O. D.; Burilove, V. A.; Fedorenko, S. V.; Konoralor, A. I.; Solovera, V. A. Temperature induced phase separation of luminescent silica nanoparticles in Triton X-100 solutions. J. Colloid Interface Sci. 2011, 354, 644−649. (8) Garcia-Blanco, F.; Elorza, M. A.; Arias, C.; Elorza, B.; GomezEscalonilla, I.; Civera, C.; Galera-Gomez, P. A. Interactions of 2,2,2trifluoroethanol with aqueous micelles of Triton X-100. J. Colloid Interface Sci. 2009, 330, 163−169. (9) Zana, R. Aqueous surfactant-alcohols systems: A Review. Adv. Colloid Interface Sci. 1995, 57, 1−64. (10) Boggetti, H.; Anunziata, J. D.; Cattana, R.; Silber, J. J. Solvatochromic study on nitroanilines. Preferential solvation vs dielectric enrichment in binary solvent mixtures. Spectrochim. Acta 1994, 50, 719−726. (11) Mancini, P. M. E.; Terenzani, A.; Adam, C.; Perez, A.; Vottero, L. R. Characterization of solvent mixtures. Part 8− preferential solvation of chemical probes in binary solvent systems of a polar aprotic hydrogen−bond acceptor solvent with acetonitrile or nitromethane. Solvent effects on aromatic nucleophilic substitution reactions. J. Phys. Org. Chem. 1999, 12, 207−220. (12) Lu, H.; Rutan, S. C. Solvatochromism studies on reversed-phase liquid chromatographic phases. 1. Synthesis and solvent effects of a new merocyanine dye, 4, 6-dichloro- 2-[2-(1-methyl-4-pyridinio) vinyl]-phenolate. Anal. Chem. 1996, 68, 1381−1386. (13) Rai, R.; Pandey, S. Solvatochromic probe response within ionic liquids and their equimolar mixtures with tetraethylene glycol. J. Phys. Chem. B 2014, 118, 11259−11270. (14) Lu, J.; Brown, J. S.; Boughner, E. C.; Liotta, C. L.; Eckert, C. A. Solvatochromic characterization of vear-critical water as a benign reaction medium. Ind. Eng. Chem. Res. 2002, 41, 2835−2841. (15) Moita, M. L.; Teodoro, R. A.; Pinheiro, L. M. Preferential solvation and solvatochromic behavior of quinolone in binary alkane1-ol/N, N-dimethylformamide solvent mixtures. J. Mol. Liq. 2007, 136, 15−21. (16) Doong, R.; Lei, W. lei, W. Solubilization and mineralization of polycyclic aromatic hydrocarbons by pseudomonas putida in the presence surfactant. J. Hazard. Mater. 2003, 96, 15−27.

the other mixtures demonstrate that the indicator is solvated preferentially by mixed solvents. An analysis of the preferential solvation parameters for Reichardt’s dye shows that this indicator is preferentially solvated by the mixed solvents in alcohols/TX-100 and water/ TX-100 mixtures. Preferential solvation of the corresponding indicator can be figured out according to the computed results of f12/1 and f12/2 of water/TX-100 that is more distinctive than the other mixtures. It may be caused by the highest interaction energy of water/TX-100 that was previously estimated by the ab initio calculations. The achieved f12/2 value of mixed 1propanol/TX-100 is lower than f 2/1 and f12/1 values that show solvated is preferential in both TX-100 and mixed solvents. As a main conclusion, the preferential solvation can be illustrated in the ascending behavior of ENT in all chosen mixtures.

4. SUMMARY AND CONCLUSIONS Solvent−solvent and solute−solvent interactions in binary mixtures of Triton X-100 (TX-100) and molecular solvents such as methanol, ethanol, 1-propanol, and water were explored by solvatochromism combined with ab initio calculations. The obtained results of the ab initio calculations exhibit that the −OH group in the alkyl side chain of TX-100 plays an important role in the organization of the solvent/TX-100 mixtures. The computed interaction energies of these mixtures are varied in the following order: water/TX-100 > methanol/ TX-100 > ethanol/TX-100 > 1-propanol/TX-100. This trend is also confirmed by the results of the electrostatic potential map (ESP) of isolated solvents and TX-100. The calculated α parameter has an ascending trend for all investigated mixtures which related to the strong O···H hydrogen bonding between TX-100 and chosen solvents. The computed ENT value in water/TX-100 mixture demonstrates the highest deviation from ideal behavior. Ideal and linear variation for ENT parameter can be seen for alcohols/TX-100 mixtures. The strongest interaction of water/TX-100 is believed to be responsible for this observation, which was previously proved by the obtained results of ESP and interaction energies. All measured solvatochromic parameters of alcohols/TX-100 mixtures have nearly a similar order of magnitude. As a main result, alkyl chain length of alcoholic solvents does not significantly affect the predicted results of solvatochromic parameters. Solute−solvent and solvent−solvent interactions H



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and theoretical approach. Spectrochim. Acta, Part A 2014, 130, 208− 213. (34) Reichardt, C. Pyridinium N-phenolatebetaine dyes as empirical indicators of solvent polarity: Some new finding. Pure Appl. Chem. 2004, 76, 1903−1919. (35) Reichardt, C.; Asharin-Fard, S.; Blum, A.; Eschner, M.; Mehranpour, A. M.; Milart, P.; Neim, T.; Schafer, G.; Wilk, M. Solute/solvent interactions and their empirical determination by means of solvatochromic dyes. Pure Appl. Chem. 1993, 65, 2593−2601. (36) Garcia, B.; Aparicio, S.; Alcalde, R.; Ruiz, R.; Davila, M. J.; Leal, J. M. Characterization of lactam-containing binary solvents by solvatochromic indicators. J. Phys. Chem. B 2004, 108, 3024−3029. (37) Reichardt, C. Solvent and Solvent Effects in Organic Chemistry, 3rd ed.; Wiley-VCH: Weinheim, Germany, 2003. (38) Marcus, Y. Solvent Mixtures: Properties and Selective Solvation; Marcel Dekker: New York, 2002. (39) Nunes, N.; Ventura, C.; Martins, F.; Leitao, R. E. Modeling preferential solvation in ternary solvent systems. J. Phys. Chem. B 2009, 113, 3071−3079. (40) Wu, Y. G.; Tabata, M.; Takamuku, T. Preferential solvation in aqueous-organic mixed solvents using solvatochromic indicators. J. Solution Chem. 2002, 31, 381−395. (41) Marcus, Y. Preferential solvation. Part 3.− Binary solvent mixtures. J. Chem. Soc., Faraday Trans. 1 1989, 85, 381−388. (42) Da Silva, D. C.; Ricken, I.; Silva, M. A. R.; Machado, V. G. Solute-solvent and solvent-solvent interactions in the preferential solvation of Brooker’s merocyanine in binary solvent mixtures. J. Phys. Org. Chem. 2002, 15, 420−427. (43) Papadakis, R.; Tsolomitis, A. Solvatochromism and preferential solvation of 4-pentacyanoferrate 4′-aryl substituted bipyridinium complexes in binary mixtures of hydroxylic and non-hydroxylic solvents. J. Solution Chem. 2011, 40, 1108−1125. (44) Maksimovic, Z. B.; Reichardt, C.; Spiric, A. Determination of empirical parameters of solvent polarity ET in binary mixtures by solvatochromic pyridinium-N-phenol betaine dyes. Fresenius' Z. Anal. Chem. 1974, 270, 100−104. (45) Rauf, M. A.; Hisaindee, S. Studies on solvatochromic behavior of dyes using spectral techniques. J. Mol. Struct. 2013, 1042, 45−56. (46) Meade, M.; Hickey, K.; McCarthy, Y.; Waghorne, W. E.; Symons, M. R.; Rastogi, P. P. Solvation of solutes with SO or CO groups in the methanol- acetonitrile solvents systems: A combined calorimetric and spectroscopic study. J. Chem. Soc., Faraday Trans. 1997, 93, 563−568. (47) Naderi, F.; Farajtabar, A.; Gharib, F. Solvatochromic and preferential solvation of fluorescein in some water-alcoholic mixed solvents. J. Mol. Liq. 2014, 190, 126−132. (48) Bagno, A. Probing the solvation shell of organic molecules by intermolecular 1HNOSY. J. Phys. Org. Chem. 2002, 15, 790−795. (49) Mancini, P. M.; Adam, C.; Perez, A. D.; Vottero, L. R. Solvatochromism in binary solvent mixtures. Response models to the chemical properties of reference probes. J. Phys. Org. Chem. 2000, 13, 221−231. (50) Ghoneim, N. Study of the preferential solvation of some betaine dyes in binary solvent mixtures. Spectrochim. Acta, Part A 2001, 57, 1877−1884. (51) Salari, H.; Khodadadi-Moghaddam, M.; Harifi-Mood, A. R.; Gholami, M. R. Preferential solvation and behavior of solvatochromic indicators in mixtures of an ionic liquid with some molecular solvents. J. Phys. Chem. B 2010, 114, 9586−9593. (52) Skwierczynski, R. D.; Connors, K. A. Solvent effects on chemical processes. Part 7. Quantitative description of the composition dependence of the solvent polarity measure ET (30) in binary aqueous- organic solvent mixtures. J. Chem. Soc., Perkin Trans. 2 1994, 467−472. (53) Bosch, E.; Roses, M. Relationship between ET polarity and composition in binary solvent mixtures. J. Chem. Soc., Faraday Trans. 1992, 88, 3541−3546.

(17) Chen, P.; Pickard, M.; Gray, M. Surfactant inhibition of bacterial growth on solid anthracene. Biodegradation 2000, 11, 341−347. (18) Kamlet, M. J.; Abboud, J. L. M.; Abraham, M. H.; Taft, R. W. J. Linear solvation energy relationships. 23. A comprehensive collection of the solvatochromic parameters, pi*, alpha, and beta, and some methods for simplifying the generalized solvatochromic equation. J. Org. Chem. 1983, 48, 2877−2887. (19) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; and Pople, J. A. GAUSSIAN 03, revision C.02.; Gaussian: Wallingford, CT, 2004. (20) Lopes, J. N. A. C.; Padua, A. A. H. Nano structural organization in ionic liquids. J. Phys. Chem. B 2006, 110, 3330−3335. (21) Padua, A. A. H.; Gomes, M. F. C.; CanongiaLopes, J. N. Molecular solutes in ionic liquids: A structural perspective. Acc. Chem. Res. 2007, 40, 1087−1096. (22) Jansen, H. B.; Ros, P. Non-empirical molecular orbital calculations on the protonation of carbon monoxide. Chem. Phys. Lett. 1969, 3, 140−143. (23) Liu, B.; McLean, A. D. Accurate calculation of the attractive interaction of two ground state helium atoms. J. Chem. Phys. 1973, 59, 4557−4558. (24) Boys, S. F.; Bernardi, F. The calculation of small molecular interactions by the difference of separate total energies. Some procedures with reduced errors. Mol. Phys. 1970, 19, 553−566. (25) Reichardt, C. Solvatochromic dyes as solvent polarity indicators. Chem. Rev. 1994, 94, 2319−2358. (26) Reichardt, C. Solvent and Solvent Effects in Organic Chemistry; VCH: Weinheim, Germany, 1988. (27) Harifi-Mood, A. R.; Habibi-Yangjeh, A.; Gholami, M. R. Solvatochromic parameters for binary mixtures of 1-(1-butyl)-3methylimidazolium tetrafluoroborate with some protic molecular solvents. J. Phys. Chem. B 2006, 110, 7073−7078. (28) Herodes, K.; Leito, L.; Koppel, L.; Roses, M. Solute-solvent and solvent-solvent interactions in binary solvent mixtures. Part 8. The ET (30) polarity of binary mixtures of formamide with hydroxylic solvents. J. Phys. Org. Chem. 1999, 12, 109−115. (29) Muldoon, M. J.; Gordon, C. M.; Dunkin, I. R. Investigations of solvent-solute interactions in room temperature ionic liquids using solvatochromic dyes. J. Chem. Soc., Perkin Trans. 2 2001, 433−435. (30) Buhvestov, U.; Rived, F.; Rafols, C.; Bosch, E.; Roses, M. Solutesolvent and solvent-solvent interactions in binary solvent mixtures. Part 7. Comparison of the enhancement of the water structure in alcohol-water mixtures measured by solvatochromic indicators. J. Phys. Org. Chem. 1998, 11, 185−192. (31) Khodadadi-Moghaddam, M.; Habibi-Yangjeh, A.; Gholami, M. R. Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents. Monatsh. Chem. 2009, 140, 329−334. (32) Nunes, N.; Elvas-Leitao, R.; Martins, F. UV-Vis spectroscopic study of preferential solvation and intermolecular interactions in methanol/1-propanol/acetonitrile by means of solvatochromic probes. Spectrochim. Acta, Part A 2014, 124, 470−479. (33) Nowak, K. Solvatochromic study of N-[4-(9-acridinylamino)-3methoxyphenyl] methanesulfonamide hydrochloride: An experimental I


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