Volumetric, acoustic and spectroscopic study of 1-butyl-3-methylimidazolium trifluoromethanesulfonate with alkoxyalkanols at different temperatures

Accepted Manuscript Volumetric, acoustic and spectroscopic study of 1-butyl-3-methylimidazolium trifluoromethanesulfonate with alkoxyalkanols at different temperatures

P. Suneetha, T. Srinivasa Krishna, M. Gowrisankar, D. Ramachandran PII: DOI: Reference:

S0167-7322(17)30821-8 doi: 10.1016/j.molliq.2017.04.129 MOLLIQ 7285

To appear in:

Journal of Molecular Liquids

Received date: Revised date: Accepted date:

23 February 2017 ###REVISEDDATE### 28 April 2017

Please cite this article as: P. Suneetha, T. Srinivasa Krishna, M. Gowrisankar, D. Ramachandran , Volumetric, acoustic and spectroscopic study of 1-butyl-3-methylimidazolium trifluoromethanesulfonate with alkoxyalkanols at different temperatures, Journal of Molecular Liquids (2016), doi: 10.1016/j.molliq.2017.04.129

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Volumetric, acoustic and spectroscopic study of 1-Butyl-3-methylimidazolium trifluoromethanesulfonate with Alkoxyalkanols at Different Temperatures

a

Department of chemistry, Acharya Nagarjuna University, Nagarjuna Nagar- 522 510, Andhra Pradesh, India

Department of Chemistry, J.K.C College, Guntur-522 006, Andhra Pradesh, India

M

c

US

Department of Physics, Vignan Institute of Technology & Science, Hyderabad-508284, Telangana, India.

AN

b

CR

IP

T

P Suneethaa, T.Srinivasa Krishnab,*, M.Gowrisankarc, D Ramachandrana,¥

AC

CE

PT

ED

*Corresponding author: Tel.: +91 903200399 E-mail addresses: ¥[email protected] *[email protected]

ACCEPTED MANUSCRIPT ABSTRACT: In the present investigation, densities (ρ), speeds of sound (u) and refractive index (nD) for the binary blends of 1-Butyl-3-methylimidazolium trifluoromethanesulfonate[Bmim][OTf], an ionic liquid, with diethylene glycol monomethyl ether (DEGMME) and diethylene glycol monoethyl ether (DEGMEE)

T

are reported over the entire range of composition, at temperatures ranging from 298.15 to 323.15 K

IP

and at 0.1MPa pressure. From the experimental data, various excesses function like excess molar

CR

volume ( VmE ), excess isentropic compressibilities (  sE ), excess molar isentropic compressibilities (

US

K sE,m ), excess speed of sound (uE), and deviation in refractive index ( nD ) are calculated. Excess functions are fitted with Redlich-Kister polynomial equation to obtain the binary coefficients and the

AN

E

E

standard errors. Excess partial molar volumes ( V m,1 and V m,2 ) and their limiting values at infinite 0, E

0, E

E

M

dilution ( V m,1 and V m,2 ) are calculated from the experimental density measurements. Excess partial E

0, E

0, E

ED

molar isentropic compression, K s ,m,1 and K s ,m,2

of both components and their respective limits at

PT

infinite dilution, K s ,m,1 and K s ,m,2 , are obtained. The nature of molecular interactions in the binary mixtures are investigated adopting FT-IR spectroscopic data especially from the view point of the

CE

associations and disassociations of intramolecular H-bondings in the alkoxyalkanol molecules by the

AC

progressive addition of the ionic liquid in the blends.

Key words: 1-Butyl-3-methylimidazolium trifluoromethanesulfonate [Bmim][OTf]∙ Alkoxyalaknols∙ Density∙ Speed of sound∙ Excess properties∙

ACCEPTED MANUSCRIPT Introduction The recent literature shows that increasing scientific interest is being envisaged on Ionic liquids as a substitute for volatile hazardous Organic Compounds in developing green methodologies of synthesis [1,2]. These ionic liquids are endowed with negligible vapor pressure, high thermal stability,

T

ability to dissolve various classes of organic, inorganic and polymeric materials and very attractive

CR

this behavior makes them to be known as the ‘designer solvents’.

IP

solvation power. These properties can be tuned by altering the cations and/or anions of the ILs and

ILs are finding applications in various industries including: in separation industry, in nuclear

US

waste treatment processes, in energy driven processes, in various chemical synthesis, as catalysts in

AN

various chemical reactions, as electrolytes in electrochemistry, in fuel and solar cells, as support for the immobilization of enzymes in separation technologies, as liquid crystals or templates for the synthesis

M

of mesoporous, nanomaterials and ordered films to name a few [3,4]. Investigations are being aimed to

ED

get better ‘tailor made’ properties by combining various cations and anions. Among the anions, halides are strongly hygroscopic and have several limitations for specific applications [5-8]. In order to

PT

overcome such limitations, much work have been focused on salts based on [BF4]- or [PF6]-anions, but

CE

in the presence of moisture these anions are hydrolyzed forming HF [9,10]. Complex anions, such as bis(trifluoromethanesulfonyl)amide [NTf2]-, trifluoromethanesulfonate [OTf]-, dicyanamide, tosylate,

AC

or n-alkylsulfates are relatively stable in hydrolyzing condition and can be used as the best alternatives[11,12]. Apart from changing the constitutional parts, i.e. cations and anions, an addition of co-solvent to improve the physicochemical properties of these designer solvents is also gaining scientific attention [13]. In the present investigation, the thermo-physical properties of mixtures of 1-Butyl-3methylimidazolium trifluoromethanesulfonate[Bmim][OTf] with diethylene glycol monomethyl ether

ACCEPTED MANUSCRIPT (DEGMME) and diethylene glycol monoethyl ether (DEGMEE) for the entire range of compositions at various temperatures and at 0.1 MPa pressure, are studied. DEGMME and DEGMEE are chosen as they are interesting amphiphilic organic solvents and are used in several organic reactions and further, there are hardly few attempts using them as constituent solvents with ILs [14-16]. Moreover, in the

T

present work, the molecular interactions of the said two alkoxyalkanols with IL, 1-butyl-3-

IP

methylimidazolium trifluoromethanesulfonate [Bmim][OTf] in their blends using volumetric, acoustic,

CR

spectroscopic and derived properties have been investigated emphatically. Further, we compared the experimental results with the published results with different anions and check the role of anion on the

AN

between IL and alkoxyalkanols at molecular levels.

US

discussed properties. FTIR spectroscopic data was also used to determine the specific interactions

2. Experimental section

M

(a) Materials:

ED

1-butyl-3-methylimidazolium trifluoromethanesulfonate [Bmim][OTf], (CAS No. 174899-662), acquired from Iolitec GmbH, Germany (≥ 99%; H2O ≤ 250ppm; halides <100ppm). Due to its

PT

hygroscopic character purity was checked through 1H-NMR on an advance DPX200 Bruker and FTIR

CE

[17] and found good agreement with literature Table 1S and Figure 1S (supplementary material). So, [Bmim][OTf] was utilized without further purification. H-NMR (200 MHz, DMSO–d6) : 9.09 (1H, s, NCHN), 7.76 (1H, s, CH3NCHCHN), 7.69 (1H, s,

AC

1

CH3NCHCHN), 4.15 (2H, t, J=7.4 Hz, NCH2(CH2)2CH3), 3.86 (3H, s, NCH3), 1.80 (2H, m, NCH2CH2CH2CH3), 1.31 (2H, m, N(CH2)2CH2CH3), 0.90 (3H, t, J=7.3 Hz, N(CH2)3CH3). The purity of the analyte Px was calculated using the following Equation Px 

AI x N std MWx mstd . . . .Pstd .100% AI std N x MWstd mx

(1)

ACCEPTED MANUSCRIPT Subscripts ‘x’ and ‘std’ relate to the test analyte and standard reference compound. AI is the absolute integral for a signal or set of signal, and N in the corresponding number of nuclides (or) number of spins. MW is the molecular weight (or, more correctly, the molar mass in kg/mol), and m is the weighed mass of material (g) and found ≥99%.

T

The alkoxyalkanols (> 99%, Sigma Aldrich, India) were purified by vacuum distillation over calcium

IP

oxide. The final mass fraction purity of DEGMME and DEGMEE was determined through gas

CR

chromatography (Figure 2S - supplementary material). Before estimation, all specimens were dried for not less than 24 h under vacuum (0.1 MPa) and moderate temperature (starting from room temperature

US

and expanding steadily to 333 K over a time of 6 h), and constantly stirred to lessen the nearness of

AN

water or other volatile substances. This process was performed systematically before and amid the physicochemical properties measurements. The source, final purities and other specifications of

M

solvents used in this work are listed in Table 1. The purities of pure liquids were further ascertained by

ED

comparing the obtained values of densities, speeds of sound and refractive indexes with the corresponding literature values [13,15,16,18-32] (vide Table 2) and found that they were in good

PT

agreement.

CE

(b) Apparatus and Procedure

An Anton Paar DSA-5000 M digital vibrating-tube densimeter was used to measure

AC

density and speed of sound of the pure liquids and their binary mixtures. Calibration of the densimeter before carrying out experimental measurements was done with degassed water, which was triply distilled and with dry air at atmospheric pressure in the experimental temperature range. All the solutions used in the measurements were made fresh on electronic Sartorius balance CPA 225D precisely within ±0.01 mg. The uncertainty for the mole fraction was estimated to be 1∙10-4. The operating frequency for speed of sound measurements was 3 MHz.

ACCEPTED MANUSCRIPT The refractive indices of pure components and binary mixtures were measured with an automatic using a digital precision refractometer Dr. Krenchen Abbemat HP (RXA170 Heavy duty, Anton Paar, Austria) as described elsewhere [33]. (C) Pure Compound Properties

T

The standard uncertainty of the estimation for these properties, u(Xi) was computed from Eq. (1) with

 X i )2

i

N ( N  1)

(2)

US

u( X i ) 

i

CR

N

(X

IP

the biggest standard deviation among the deliberate temperature ranges and components.

where Xi is the experimental values of the component i, is the mean of multiple exploratory data points,

AN

and N is the quantity of experimental data points. The standard uncertainty detailed in this work is

M

absolute standard uncertainty and very alluding to the level of repeatability, and the level of confidence k =1(68%). The uncertainties associated with the measurements for temperature, density and speed of

PT

temperature 0.02K respectively.

ED

sound were estimated to be within 0.01 K, 0.04 kg·m−3, 0.3 m·s−1 and for refractive index 0.0001,

Uc ( ) 

1 2 S   u2  ui2  uT2 N

(3)

AC

CE

The combined expanded uncertainty (Uc(ρ)) for N density measurements can be expressed as:

where Sρ, u??,ui and uT are the uncertainties because of the average standard deviation, instrument resolution,

instrument’s fluctuated reaction with density range and the uncertainty in measured

temperature respectively. The calculated Sρ = 0.04 kg·m−3, uγ = 0.005 kg·m−3, ui = 0.04 kg·m−3 and uT was 0.01 kg·m−3 in this work. Therefore, the combined expanded uncertainty (Uc(ρ)) was less than u(ρ)= 0.04 kg·m−3 from Eq. (2). According to Chirico et al. [34] the impurity of sample makes the standard uncertainty much larger. Therefore, when accounting combined expanded uncertainty of

ACCEPTED MANUSCRIPT measured density including the impurity of ionic liquids, in this work would be 0.7 kg·m−3. Similarly combined expanded uncertainty for measured speed of sound 0.5m.s-1 and refractive index is 0.0004. All molar quantities used were based on the IUPAC relative atomic mass table [35]. Proper care was taken to avoid the water adsorption during the preparation of the mixture by mixing the

T

components in the dry box. The chemicals were put away in tightly sealed 8ml amber colored glass

IP

vials with screw caps having PFE septa, and a safe fixed with parafilm and sufficient precautionary

CR

measures were taken to limit losses through evaporation, and absorption of moisture.

US

FT-IR measurements of pure [Bmim][OTf], DEGMME, DEGMEE and 0.1- 0.9 (except 0.6 and 0.8) mole fractions of [Bmim][ OTf] + DEGMME/DEGMEE mixtures were carried out with FT-IR

AN

Spectrometer (Alpha FT-IR, Bruker, Germany) with accessory Alpha E by using ATR technique (400-

M

4000) cm−1 with 4.0 cm−1 resolution to investigate the presence of hydrogen bonding and strength of molecular associations in these mixtures. All spectrums were recorded at room temperature. The IR

ED

data were analyzed using OPUS 6.5 software.

3.1 Excess properties

PT

3. Theory

CE

To understand the molecular interactions of [BMIM][OTf] + DEGMME/+DEGMEE

the

AC

thermophysical properties such as density, ρ, speed of sound, u, and refractive index, nD, are determined over the whole mole fraction range at temperature range from 298.15 K to 323.15 K under atmospheric pressure 0.1 MPa with an uncertainty of ±0.1kPa. Excess molar volume ( VmE ), excess isentropic compressibility (  sE ), excess molar isentropic compressibility ( K sE,m ), excess speed of sound ( u E ) and deviation refractive index ( nD ) were calculated from the density, speed of sound and refractive index measurement by the relationships [36-38]:

ACCEPTED MANUSCRIPT VmE  Vm  Vmid

(4)

 sE   s   sid

(5)

K SE,M  K S ,M  K Sid,M

(6)

u E  u  u id

(7)

T

The values of Vm, id and Vmid were calculated using the relations

IP

Vm  ( x1Vm,1  x2Vm,2 ) /  id

x1M1

1



(1  x2 ) M 2

US

Vmid 

CR

 id  x11  x2 2

2

(8) (9) (10)

AN

where x1 and x2 refer to mole fraction, M1 and M2 represent molar mass, Vm,1 and Vm,2 the molar volume

M

of DEGMME/DEGMEE (1) + [BMIM][OTf] (2) and ‘id’ represents ideal mixture respectively. The thermodynamic properties for which values derived directly from the experimental measurements

ED

were density ρ, molar volume Vm, molar heat capacity at constant pressure Cp, and the coefficient of

1 Vm 1   ln  ( ) p   ( ) p  ( )p Vm T  T T

(11)

CE

p 

PT

thermal expansion, αp, and the isentropic compressibility, κS.

In this work, αp values are obtained from a linear dependence of ρ with T. The isentropic

AC

compressibility are calculated using the Newton-Laplace equation from experimental values of density and speed of sound,

S 

1 u2

K S , M   SVm

(12) (13)

ACCEPTED MANUSCRIPT Excess isentropic compressibility  sid and excess molar isentropic compressibility K sid,m are calculated by using the following relations

(14)

 x1 (Vm,1 p ,1 )2 x2 (Vm,2  p,2 )2 (Vmid idp )2   x1K s ,m,1  x2 K s ,m,2  T     C p ,1 C p ,2 C idp  

id s ,m

T

K

  V  2  V  2 V id  id 2  m p 1 m ,1 p ,1 2 m ,2 p ,2   1 K s ,1  2 K s ,2  T    id   C p ,1 C p ,2 Cp  

(15)

IP



id S

Vmid  p and C p were calculated using the following relations:

xV

i m ,i 2 i 1 i m ,i

 xV

AN

i 

id

US

id

CR

where T the absolute temperature,  the volume fraction, αp the isobaric expansivity. The values of i,

M

 idp  1 p,1  2 p,2

ED

Vmid  x1Vm,1  x2Vm,2

PT

C idp  x1C p,1  x2C p,2

[36]:

CE

uE, was estimated in binary mixtures by using the thermodynamically rigorous ideal mixing expression

AC

u E  u  u id  u  (  id sid )1/ 2

(16)

The deviation in refractive index, nD was calculated by using the following expression nD  nD  nDid

(17)

Reis et al. [39] have proposed the following expression for the “ideal” refractive index

nDid  [1nD2 ,1  2 nD2 ,2 ]1/2

ACCEPTED MANUSCRIPT The values of VmE ,  sE K sE,m , u E and nD as functions of mole fraction, x1 of [Bmim][OTf] and temperature for both the systems are presented in Table 3S (Supplementary material). The excess values of the above parameters for the mixtures have been fitted to the Redlich-Kister [40] polynomial equation n

T

Y E  x1 x2  Ai (1  2 x1 )i

(18)

IP

i 1

CR

where YE is VmE ,  sE , K sE,m and uE and nD . The volume fraction  is used in place of x for fitting of

US

 sE and nD . The equation coefficients, Ai, obtained by the method of least squares with equal weights

assigned to each point were calculated along with the standard deviation  (YE). The coefficients were

AN

adjustable parameters for a better fit of the excess functions.



2

1/ 2

   

(19)

ED



E E   Yexp t  Ycal  (Y )    ( m  n)  E

M

The standard deviation σ(YE) is calculated using,

PT

where m equal to the number of experimental points, n is the number of Ai coefficients considered (n + 1 in the present study). The optimal number of Ai coefficients has been determined statistically by

CE

performing F-test. The coefficients, Ai and corresponding standard deviations, σ fit of VmE ,  sE K sE,m ,

AC

E u E and nD values for the mixtures are listed in, Table 5. The variations of VmE ,  sE , Ks,m , u E and nD

with mole fraction, x1 along with smoothed values from Eq. (18) at studied temperatures are shown graphically in Figure 15, respectively. 3.2 Partial molar properties

ACCEPTED MANUSCRIPT In addition to other volumetric properties, (partial molar volumes and partial molar compressibility)

Ym ,1 and Ym ,2 of IL and alkoxyalkanols over the entire concentration range in investigated system have been determined using following equations

YsE  x1 ( )T , p x1

(21)

CR

* m ,2

(20)

IP

Y m,2  Y  Y E s

YsE )T , p x1

T

Y m,1  YsE  Ym*,1  x2 (

US

where Y is V or K s where Ym*,1 and Ym*,2 are the molar components of pure components IL and alkoxyalkanols, respectively. The derivative (YsE / x1 )T , p in equations (20) and (21) was obtained by

AN

differentiation, which lead to the following equations for Y m,1 and Y m,2 . j

j

i 0

i 0

j

j

*

M

Y m,1  Y m,1  x22  Ai (1  2 x1 )i  2 x1 x22  Ai (1  2 x1 )i 1 *

ED

Y m,2  Y m,2  x12  Ai (1  2 x1 )i  2 x2 x12  Ai (1  2 x1 )i 1 i 0

(22)

(23)

i 0

PT

Ym*,1 and Ym*,2 are the molar properties of pure components, and the excess partial molar properties were

E

YmE

xi

)

(24)

AC

Y m,i  YmE  (1  x1 )(

CE

calculated by following relations,[41,42]

We are interested to evaluate the partial molar properties of [Bmim][OTf] at infinite dilution (x1=0) in DEGMME/DEGMEE, and the partial molar properties of DEGMME/DEGMEE at infinite 0

dilution(x2=0) in [Bmim][OTf]. Therefore, Y m,1 is obtained by setting x1=0 which leads to n

Y m,1  Ym*,1   Ai (1)i 0

i 0

Similarly setting x2=0, leads to

(25)

ACCEPTED MANUSCRIPT n

Y m,2  Ym*,2   Ai 0

(26)

i 0

0

0

here Y m,1 and Y m,2 represent the partial molar properties of [Bmim][OTf] at infinite dilution in DEGMME/ DEGMEE and the partial molar properties of DEGMME/ DEGMEE at infinite dilution in

T

[Bmim][OTf], respectively. 0, E

were evaluated through relations 0, E

0

0, E

0

US

Y m,1  Y m,1  Ym*,1

CR

IP

Excess partial molar properties at infinite dilution Y m,i for each component in binary liquid mixtures

(28)

AN

Y m,2  Y m,2  Ym*,2

(27)

In another way the values of the partial excess volume of solute and solvents at infinite dilution 0, E

0, E

M

Y m,1 and Y m,2 can be calculated from the adjustable parameters of Redlich−Kister smoothing equation

ED

when x1 → 0 and x2 → 1. Under such circumstances, the presentations for partial excess volumes were

PT

deduced as shown in equations (27) to (28), and their calculated values were shown in Table 6,

Redlich−Kister: E ,

CE

respectively:

E ,

AC

Y m,1  A0  A1  A2  A3  A4

Y m,2  A0  A1  A2  A3  A4

(29) (30)

4. Result and Discussion The experimental values of densities (ρ), speeds of sound (u) and refractive index (nD) for both studied binary mixtures over the entire composition range and at 298.15 to 323.15 K temperatures are listed in Tables 3 and 4. The variation of pure values of , u and nD with temperature is found to be linear whereas variation of , u and nD with mole fraction is found to be non-linear.

ACCEPTED MANUSCRIPT For both of the systems, the calculated excess molar volume ( VmE ), isentropic compressibility (  sE ), excess molar isentropic compressibility ( K sE,m ), excess speed of sound (uE) and deviation in refractive index ( nD ) were reported in Table 3S (Supplementary material).

T

The dependence of VmE for both the mixtures was graphically represented as Figs. 1 and 2. In both

IP

systems, VmE was found to be negative and became more negative with increasing experimental

CR

temperature, i.e. VmE / T is negative. Negative VmE / T reveals, formation of associated species

US

between the ILs and alkoxyalkanols with increasing temperature, which results in a contraction in volume of the mixture, and hence negative VmE [15,16]. In the present investigation, the notable

AN

difference in the molar volumes of [Bmim][OTF] (molar volume Vm= 222.15 x10-6 m3mol-1) and

M

alkoxyalkanols (DEGMME, Vm =118.28 x 10-6 and for DEGMEE, Vm = 136.43 x10-6 m3mol-1) makes it possible for the relatively small alkoxyalknaol molecules to enter into the interstices of the

ED

[Bmim][OTF] upon mixing. This is very well supported by the molecular dynamics simulation study

PT

[43], which shows that the smaller molecules are fitted into the voids of the ILs, made up of

CE

asymmetric cations and anions, as a result, and contributes to the negative VmE . A minimum in VmE is reached near 0.4 and 0.5 mole fraction of IL in DEGMME and DEGMEE binary systems respectively.

AC

Several authors discussed the formation of liquid clathrates or quasi-clathrates, which appears as an unusual structure to be responsible for similar minima around 0.4 and 0.5 mole fraction of IL with molecular solvents [44,45]. It is observed that VmE decreases in the sequence of MEE > MME (Fig. 3). Thus, on increasing the alkyl group VmE became more negative. Similar results were observed from the literature, where Pal et al., observed the VmE for [Bmim][BF4] + DEGMME (-1.191)[12], [Bmim][PF6] + DEGMME (-1.231) [46] and [Bmim][PF6] + DEGMEE (-1.573)[16]. We graphically compared our

ACCEPTED MANUSCRIPT VmE results with the mixtures of ILs with different anions (BF4 and PF6) in Fig 4 at 298.15 K. The observed variations in VmE of IL mixtures with molecular solvents are attributed to the formation of hydrogen bond, ion - dipole interaction and geometrical fitting with [Bmim][OTf]. Speed of sound can be used to analyze molecular interactions of solvent–solvent, solute–solute

IP

T

and solute–solvent. As discussed in our previous paper [47], a third-order polynomial was used to fit

CR

speed of sound as a function of concentration (bi), for pure substances and its binary mixture of [Bmim][OTf] with DEGMME, were listed in Table 2S and Fig 3S (Supplementary material).

US

u  b3 x13  b2 x12  b1 x1  b0

AN

The behavior of  sE and K sE,m as a function of composition were depicted in Figs. 5 and 6 at 298.15K. Strong molecular interactions occur through charge transfer, ion-dipole, and ion-ion

M

interactions, interstitial accommodation, and oriental ordering and all lead to a more compact structure,

ED

which makes  sE negative[48]. A perusal of Figs. 5 and 6, excess isentropic compressibility decreases

PT

and becomes increasingly negative as the strength of the interaction between the components increases, due to a closer approach of unlike molecules leading to reductions in compressibility [49]. But in the

CE

case of DEGMME,  sE and K sE,m values exhibit sigmoid trend with negative values at low mole

AC

fractions of [Bmim][OTf] and then become positive as the concentration of [Bmim][OTf] increases in this binary mixture in the investigated temperature range. At low volume fraction ( < 0.3) of [Bmim][OTf], the hydroxyl oxygen and alkyl hydrogen of DEGMME are able to form hydrogen bonds with imidazolium aromatic C-H hydrogen (at C2 position) and oxygen/fluorine atoms of triflate [OTf] anion[50]. But at rich region [Bmim][OTf] ions are unable to form/breaking of hydrogen bond with DEGMME may be likelihood formation, i.e., between IL-IL (or) MME-MME.

ACCEPTED MANUSCRIPT The values of  sE and K sE,m become more negative with increasing the alkyl group in alkoxyalkanol (i.e. MEE> MME) similar to VmE . As expected, the uE values also exhibit sigmoid trend with positive uE values at low mole fractions of [Bmim][OTf] and then uE values become positive as the concentration of [Bmim][OTf]

IP

T

increases in [Bmim][OTf] and DEGMME binary mixtures in the investigated temperature range. In the case of [Bmim][OTf] and DEGMEE uE values exhibit positive trend. Positive deviation in uE indicates

CR

strong interaction whereas negative deviation in uE indicates weak interactions between the unlike

US

component molecules [51]. Thus, the trends of uE vs. x1 (Fig. 7) strongly support the behavior of  sE for

AN

these mixtures.

The refractive index is one of tool to measure of the electronic polarizability of a molecule and

M

can give valuable data regarding the strengths between different segment molecules in the liquid

ED

mixtures. Deviation in refractive index data is positive over the entire composition range for the present two binary systems (Fig.8). In general, the positive deviation in ΔnD values on basis of volume fraction

PT

indicates for the presence of significant interaction in mixtures whereas negative deviation in Δn D

CE

values indicates presence of weak interactions. Refractive index decreases with increase of temperature whereas increase with molefraction in [Bmim][OTf] with DEGMME/DEGMEE mixtures. As the mole

AC

fraction of the [Bmim][OTF] increases VmE becomes more negative as the free volume available decreases in the mixtures and hence speed of light travel with lesser velocity than that in the ideal mixtures. Positive values of ΔnD corresponded to negative VmE values and vice versa and are in good agreement with the view of Brocco et al.[52] 4.1 Partial molar properties The properties of partial molar volumes are well reflected on the existing molecular interactions in the present investigated systems. The partial molar volumes are arising due to the contributions such

ACCEPTED MANUSCRIPT as intrinsic volume of the ion, electrostriction volume of the solvent and structural contribution. Partial molar volumes of [BMIM] [OTf] and aloxyalkanols for all compositions were calculated using Redlich-Kister coefficients from Table 5 keeping in Eq. (19) and (20). We focused our attention here 0

for partial molar volumes of [BMIM][OTf] at infinite dilution in an alkoxyalkanols ( V m,1 ) and the 0

IP

T

partial molar volumes of an alkoxyalkanols at infinite dilution in IL ( V m,2 ) from Eq (25) and (26). The E

E

CR

values of partial molar volumes ( V m,1 and V m,2 ), excess partial molar volumes ( V m,1 and V m,2 ) as functions of mole fractions of IL and temperature were given in Table 4S and 5S and the variations of E

E

0

*

0, E

0

*

US

V m,1 and V m,2 with composition at 298.15K were presented in Fig 9. The values of V m,1 , V m,1 , V m,1 , V m,2 0, E

AN

, V m,2 and V m,2 for both the binary systems at the investigated temperatures were listed in Table 6. E

E

M

From this, we observed the excess partial molar volumes of V m,1 and V m,2 are negative for the entire

ED

composition range. This suggests that the molar volumes of each component in the mixture are less than their respective molar volume in the pure state, i.e., there is a decrease in the volume on mixing

PT

[Bmim][OTf] with alkoxyalkanols. This reflects the breaking of the self-association of alkoxyalkanols

CE

molecules and formation of hydrogen bond due to unlike molecules. The values of excess partial molar volumes increase with the increase in temperature of the mixture for each system investigated, which

AC

indicates the breaking of donor-acceptor interactions between unlike molecules to rise in temperature leading to an expansion in volume. E

E

The values of K s ,m,1 , K s ,m,2 and K s ,m ,1 , K s ,m ,2 as functions of mole fraction of [Bmim][OTf] and E

E

temperature were given in Table 6S and 7S and the variations of K s ,m ,1 and K s ,m ,2 with composition at T 0

*

0, E

0

0,*

0, E

= 298.15 K were presented in Fig 10. The values of K s ,m ,1 , K s ,m ,1 , K s ,m ,1 , K s ,m ,2 , K s ,m ,2 and K s ,m ,2 for the binary systems at each investigated temperature are listed in Table 7. A close perusal of Fig 10

ACCEPTED MANUSCRIPT E

E

indicates that the values of K s ,m ,1 are negative and those K s ,m ,2 are negative and positive with increase of temperature. This suggests that the molar isentropic compressibility of each component in the mixture is less than their respective molar isentropic compressibility in the pure state, i.e., there is a decrease in the molar isentropic compressibility on mixing [BMIM][OTf] with alkoxyalkanols. In general, the E

E

E

IP

T

negative K s ,m ,1 and K s ,m ,2 values indicate the presence of significant (solute + solvent) interactions E

CR

between unlike molecules, whereas the positive K s ,m ,1 and K s ,m ,2 values indicate the presence of solute +

mixture. The magnitude of

E

K s ,m ,1 and

E

K s ,m ,2

US

solute/solvent + solvent (or weak solute + solvent) interactions between like molecules [53] in the at equimolar compositions follows the order:

AN

DEGMME
E

M

decreases with the position of methyl groups. Further, the K s ,m ,1 and K s ,m ,2 values can be analyzed in terms of structural and geometrical compressibility as suggested by Hall and others[54,56].The

ED

structural compressibility results from the breakdown of associated structure (on mixing [BMIM][OTf]

PT

with alkoxyalkanols) while geometrical compressibility is due to simultaneous compression of the molecules (due to specific interactions between [BMIM][OTf] with alkoxyalkanols molecules) leading

E

CE

to contraction in volume and decrease in the average intermolecular distances. The observed positive E

E

AC

values of K s ,m ,1 and K s ,m ,2 indicates that the structural compressibility factor dominates in these mixtures. E

Also, the K s ,m ,1 and K s ,m ,2 values increase with an increase in temperature (Table 7S) for each binary E mixtures under study. These trends further support the conclusions drawn from VmE ,  sE , u E , Ks,m , 0E

0E

 nD , V m,1 and V m,2 values of these binary mixtures.

ACCEPTED MANUSCRIPT 5. Spectral studies The nature and extent of interactions between the ILs and organic solvents are well documented through thermodynamic studies and are not sufficient to derive the exact nature of solute-solvent interactions between the interacting components [15,16].

T

To achieve this goal, here we examined the intermolecular interactions between the ionic liquid

IP

[Bmim][OTf] and alkoxyalkanols at molecular level over the whole composition range using FTIR

CR

spectroscopy. It is an important tool for identification of small change in dipole moments [57,58]. Additionally, it gives the clear understanding about the interpreting of hydrogen bond in both intra- and

US

intermolecular interactions based on the sharpness of the O-H stretching frequency in the mixture.

AN

The infrared spectra for pure alkoxyalkanols, [Bmim][OTf] with their binary mixtures were shown as Fig. 11 and 12. In 1-Butyl-3-methylimidazolium cation the CH stretching region between

M

2800 cm-1 and 3600 cm-1 was analyzed. For [Bmim][triflate], the signals in this region can be split into

ED

two parts: (1) The signals between 2800 cm-1 and 3000 cm-1 result from aliphatic CH groups in the ethyl and methyl moieties (2) signals between 3000 cm-1 and 3200 cm-1 can be assigned to CH modes

PT

predominantly originating from the aromatic imidazolium ring, from C2-H and C4,5-H stretching

CE

frequencies. In the present binary mixtures, no change was observed in the CH stretching frequencies (Fig. 13) of the cation at all mole fractions. As shown in the spectra there appears a broad O-H

AC

stretching vibration in the 3200–3600 cm-1 range suggesting the possible intramolecular hydrogen bonding between the alkoxyalkanol and [OTf] molecules. Similar results were reported with Water- IL and ethylene glycol- IL mixtures [59,60]. Fig. 13 reveals the FTIR spectra for the studied binary mixtures between the frequency range 2800-3600cm-1. As the concentration of IL increases, (i) the absorbance decreases indicating the disruption in the hydrogen-bond of alkoxyalknaols and (ii) The - OH stretching band positions are blue-shift in the spectra of both the binary mixtures. These characteristics of the spectra indicates the

ACCEPTED MANUSCRIPT qualitative change in intermolecular hydrogen bonding between the components of the mixture, which is a result of increase in force constant due to strengthening of the O - H bond via weak electrostatic interaction between the protons of IL cation and the lone pair electrons of the - O - in alkoxylalkanols [56]. Blue shift in O – H stretching frequencies is higher in DEGMME than DEGMEE, which is

thermodynamics data.

CR

6. Calculation of excess molar volume ( VmE ) with the PFP theory

IP

T

indicative of the higher interaction between the [Bmim][OTf] and DEGMME as observed by the

Several reports have been found in the literature for the prediction of excess molar volume of the

US

liquid mixtures having one component as the IL through the Prigogine-Flory-Patterson (PFP) statistical theory. According to the PFP theory, VmE is divided into three contributional terms: (i) the free volume

AN

VmE ( fv) , (ii) the characteristic pressure VmE (ip) , and (iii) the energy of interaction VmE (int) . These three

M

contributions together can be expressed as:

(31)

PT

(V1  V2 )( P1*  P2* ) 1 2 P1* 2  P2*1

ED

 12  (V1  V2 )2 [(14 / 9)V 1/ 3  1]1 2 VmE (V 1/ 3  1)V 2 / 3 +     1 2 *  x1V1*  x2V2* [(4 / 3)V 1/ 3  1] [(4 / 3)V 1/ 3  1)V  P1 

CE

Here xi, Pi * , Vi * , V i , i, andi are the mole fraction, characteristic pressure, characteristic volume, reduced volume, segment fraction and contact energy fraction of component i, respectively and

AC

outlined previously [33]. 12 is the Flory’s contact interaction parameter. The PFP parameters for the pure components are reported in Table 8. The only adjustable parameter of the PFP theory, the contact interaction parameter 12 is obtained by experimental VmE values as the values for the experimental excess molar enthalpy ( H mE ) are not available. 12 for both of the mixtures are found to be negative. E E Fig 14 shows the comparison between them VExp and VPFP for the investigated binary mixtures over a

full range of concentrations at 298.15 - 323.15 K. The values of three contributions: VmE ( fv) , VmE (ip) ,

ACCEPTED MANUSCRIPT E E and VmE (int) to VPFP at equimolar composition and corresponding standard deviations  between VExp E and VPFP are summarized in Table 9.

In the present investigation, for both of the mixtures, VmE (int) and VmE ( fv) was found negative and increases negatively with temperature (Table 9), which shows that with increasing temperature, more

T

spaces becomes available in the ILs molecules to accommodate the smaller alkoxyalkanol molecules.

IP

Characteristic pressure VmE (ip) term, which is dependent on the structure-breaking effect is

CR

proportional to ( P1*  P2* )( V 1  V 2 ) and can have both the negative and positive sign depending upon

~ the magnitude of P* and V of unlike components [11,20,61]. In the current study, VmE (ip) is positive

US

for both of the mixtures. The interaction term VmE (int) , representing the energy of interaction is negative and increases negatively with temperature for both of the systems. Analysis of three contribution terms

AN

VmE ( fv) , VmE (ip) and VmE (int) reveals that free volume contribution VmE ( fv) and VmE (int) play dominant

M

role in the overall negative values of the VmE . We can conclude that, it is possible to describe the

ED

volumetric behavior of present mixtures by the application of the PFP theory quite successfully.

Conclusions

PT

Densities, , speed of sound, u, refractive index, nD of pure and its binary mixtures of [Bmim][OTf] and alkoxyalkanols at different temperatures (T/K = 298.15-323.15) and at atmospheric pressure

CE

0.1Mpa measured over entire composition range experimentally. The excess/deviation properties such as VmE ,  sE , K sE,m , u E and nD have been fitted with Redlich – Kister smoothing polynomial

AC

equation. The observed negative values of VmE ,  sE and K sE,m and positive values of u E and nD clearly indicating the dominance of strong attractive forces. Our data additionally confirm the strong interactions take place between [Bmim][OTf] and alkoxyalkanol, and less stronger than other anions such as [BF4] and [PF6]. The measured values of partial molar volumes and partial molar isentropic compressibilities follows the same order of VmE /  sE . In the present study, FTIR spectral data supported the existence of strong molecular interactions between [Bmim][OTf] and alkoxyalkanol.

ACCEPTED MANUSCRIPT Acknowledgement P Suneetha is thankful to the CSIR, India for the award of Junior Research Fellowship. The authors are also thankful to Arvind kumar, Principal Scientist, CSMCRI, India for providing the research facilities.

References

T

[1] A. Pratap Singh, R. Gardas, S. Senapati, Phy. Chem. Chem. Phy. 17 (2015) 25037-25048.

IP

[2] A. S. M. C. Rodrigues, M. A. A. Rocha, H. F. D. Almeida, C. M. S. S. Neves, J.A. Lopes-da-Silva, M.

CR

G. Freire, J. A. P. Coutinho, L. M. N. B. F. Santos, J. Phys. Chem. B 119 (2015) 8781-8792. [3] M. A. Iglesias-Otero, J. Troncoso, E. Carballo, L. Romani, J. Chem. Eng. Data 53 (2008) 1298-1301.

US

[4] N. I. Malek, S. P. Ijardar, S. B. Oswal, J. Chem. Eng. Data 59 (2014) 540−553

AN

[5] Y. Chauvin, H. Olivier-Bourbigou, CHEMTECH 25 (1995) 26–30. [6] J. D. Holbrey and K. R. Seddon, Clean Prod. Proc., 1 (1999) 223–236.

M

[7] R. Sheldon, Chem. Commun., 23 (2001) 2399-2407.

ED

[8] C. M. Gordon, Appl. Catal. A, 222 (2001) 101–117. [9] V. Najdanovic-Visak, J. M. S. S. Esperanca, L. P. N. Rebelo, M. N. da Ponte, H. J. R. Guedes, K. R.

PT

Seddon , J. Szydlowski, Phys. Chem. Chem. Phys.4 (2002) 1701-1703.

CE

[10] R.P.Swatloski, J.D. Rogers, R.D. Rogers, Green Chem. 5 (2003) 361-363. [11] E. I. Cooper, Eugene J. M. O'Sullivan, Proc. Electrochem. Soc. 16 (1992) 386-396.

AC

[12] S. A. Forsyth, J. M. Pringle, D. R. MacFarlane, Aust. J. Chem. 57(2004) 113-119. [13] R. L. Gardas, M. G. Freire, P. J. Carvalho, I. M. Marrucho, I. M. A. Fonseca, A. G. M. Ferreira, J. A. P. Coutinho, J. Chem. Eng. Data 52 (2007) 80-88. [14] A. Kumar, Tejwant Singh, R. L. Gardas, J. A.P. Coutinho, J. Chem. Thermodyn. 40 (2008) 32–39. [15] A. Pal and B. Kumar, J. Chem. Eng. Data. 57(2012) 688-695. [16] A. Pal, B. Kumar, J. Mol. Liq. 163 (2011) 128–134. [17] B. Schwenzer, S. N. Kerisit, M. Vijayakumar, RSC Adv., 4 (2014) 5457–5464.

ACCEPTED MANUSCRIPT [18] G. Garcia-Miaja, J.Troncoso, L. Romani, J. Chem. Thermodyn., 41 (2009) 161–166. [19] O. Zech, A. Stoppa, R. Buchner, W.Kunz, J. Chem. Eng. Data. 55 (2010) 1774 – 1778. [20] E. Vercher, P. J. Miguel, F. J. Llopis, A. V. Orchilles, A. M.Andreu, J. Chem. Eng. Data. 57 (2012) 1953−1963.

T

[21] Gonzalez, E. J, Calvar, N, Dominguez, A, Macedo, E. A, J. Chem. Thermodyn. 61 (2013) 64-73.

IP

[22] Xin-Xue Li, Wei-Dong Zhou, Xiao-Ya Li, Jian-Ling Sun, Wei Jiang, J. Mol. Liq. 148 (2009) 73-76.

CR

[23] R. Francesconi, C. Castellari, F. Comelli, J. Chem. Eng. Data 44 (1999) 1373-1378. [24] Harsh Kumar, Meenu Singla, Akanksha Khosla, J. Sol. Chem. 42 (2013) 428-440.

US

[25] Li Xinxue, Xu Guomin, Wang Yanwei, and Hu Yijiang, Chinese J. Chem. Eng 17 (2009) 1009-1013. [26] C. M. Kinart, Anetawikliska and W. J. Kinart, J. Therm. Anal. Calorim., 84 (2006) 535–542.

AN

[27] E. R. Lopez, L. Lugo, M. J. P. Comunas, J. Garcıa, J. Fernandez, J. Chem. Eng. Data 49 (2004) 376-

M

379.

[28] R. G. Seoane, S. Corderi, E. Gomez, N. Calvar, E. J. Gonzalez, E. A. Macedo, A. Dominguez, Ind.

ED

Eng. Chem. Res. 51 (2012) 2492−2504.

PT

[29] A. N. Soriano, B. T. Doma Jr. b, Meng-Hui Li, J. Chem. Thermodyn. 41 (2009) 301–307. [30] G. Garcia-Miaja, J. Troncoso, L. Romani, Fluid Phase Equilibria 274 (2008) 59–67.

CE

[31] Yu-Ming Tseng, A. R. Thompson, J. Chem. Eng. Data 7 (1962) 483.

AC

[32] P. Goralski, M. Tkaczyk, J. Chem. Eng. Data 60 (2015) 2240-2247. [33] P. Suneetha, T. S. Krishna, M. Gowrisankar, K. Ravindhranath, D.Ramchandran, J. Chem. Thermodyn. 108 (2017) 181–192.

[34] R.D. Chirico, M. Frenkel, J.W. Magee, V. Diky, C.D. Muzny, A.F.Kazakov, K. Kroenlein, I. Abdulagatov, G.R. Hardin, W.E. Acree, J. F. Brenneke, P. L. Brown, P.T. Cummings, T.W. de Loos, D. G. Friend, A.R. Goodwin, L.D. Hansen, W. M. Haynes, N. Koga, A. Mandelis, K.N. Marsh, P.W. Mathias, C. McCabe, J.P. O.Connell, A. Padua, V. Rives, C. Schick, J.P. Trusler, S. Vyazovkin, R.D. Weier and J. Wu, J. Chem. Eng. Data, 58 (2013) 2699-2716.

ACCEPTED MANUSCRIPT [35] International Union of Pure and Applied Chemistry. Inorganic Chemistry Division, Commission on Atomic Weights and Isotopic Abundances. Pure Appl. Chem. 58 (1986) 1677−1692. [36] G. Douheret, M.I. Davis, J.C.R. Reis, M.J. Blandamer, Chem Phys Chem 2 (2001) 148 –161. [37] G. Douheret, M.I. Davis, J.C.R. Reis, Fluid Phase Equilib. 231 (2005) 246–249.

T

[38] G.C. Benson, O. Kiyohara, J. Chem. Thermodyn. 11 (1979) 1061–1064.

CR

[40] O. Redlich, A.T. Kister, Ind. Eng. Chem. 40 (1948) 345–348.

IP

[39] J. Reis, I. Lampreia, A. Santos, M. Moita, G. Douheret, Chem. Phys. Chem. 11(2010) 3722–3733.

[41] H. Iloukhani1, R. Ghorbani, J. Sol. Chem. 27(2) (1998) 141-149.

US

[42] M. I. Davis, G. Douheret, Joao Carlos R. Reisand Michael J. Blandamer, Phys. Chem. Chem. Phys. 3

AN

(2001) 4555-4559.

[43] P. Assarson, F. R. Eirich, J. Phys. Chem. 72 (1968) 27102719.

M

[44] J. D. Holbrey, K. R. Seddon, J. Chem. Soc., Dalton Trans. 1999, 2133-2139. [45] H.Gao, F. Qi, H. Wang, J. Chem. Thermodyn. 2009, 41, 888–892.

ED

[46] A. Pal, Rekha Gaba, Tejwant Singh, Arvind Kumar, J. Mol. Liq. 154 (2010) 41-46.

PT

[47] M. Srilakshmi, T. S. Krishna, K. Narendra, Ranjan Dey, A. Ratnakar, J. of Mol. Liq. 211 (2015) 854– 867.

CE

[48] A. Pal, H. Kumar, R.M. Maan, H.K. Sharma, J. Chem. Eng. Data. 58 (2013) 3190−3200.

AC

[49] R. J. Fort and W.R. Moore, Trans. Faraday Soc., 61 (1965) 2102-2111. [50] J.M Crosthwaite, S.N.V.K Aki, E.J Maginn, J.F Brennecke J. Phys. Chem. B. 108 (2004) 5113–5119. [51] F. Kawaizumi, M. Ohno, Y. Miyahara, Bull. Chem. Soc. Jpn. 50 (1977) 2229–2236. [52] P. Brocos, A. Pineiro, R. Bravo, A. Amigo, Phys. Chem. Chem. Phys. 5 (2003) 550–557. [53] F. Kermanpour, T. Sharifi, Thermochim. Acta, 527 (2012) 211– 218. [54] L. Hall, Phys. Rev. 73 (1948) 775–784. [55] A. Cipiciani, G. Onori, G. Savelli, Chem. Phys. Lett. 143 (1988) 505–509. [56] B. Hawrylak, K. Gracie, R. Palepu, J. Sol. Chem. 27 (1998) 17–31.

ACCEPTED MANUSCRIPT [57] K. Muller-Dethlefs, P. Hobza, Chem. Rev. 100 (2000) 143–167. [58] H. Yui, K. Kanoh, H. Fujiwara, T. Sawada, J. Phys. Chem. A 106 (2002) 12041–12044. [59] T. Singh, K.S. Rao, A. Kumar, Chem. Phys. Chem. 12 (2011) 836–845. [60] T. Singh, A. Kumar, Vib. Spectrosc. 55 (2011) 119–125.

T

[61] A. Pal, B. Kumar and Tejwant Singh, Fluid Phase Equilib. 358 (2013) 241-249.

IP

Figure Titles:

CR

Figure 1. Plots of excess molar volume, VmE vs. mole fraction, x1 of [Bmim][OTf] for [Bmim][OTf] +

US

DEGMME binary mixtures at temperatures, T/K = 298.15, ; At T/K = 303.15, ■; T/K = 308.15, ▲; T/K = 313.15, ; T/K = 318.15, ; T/K = 323.15, ∆. The points represent experimental values and lines represent values calculated from equation (17) using the coefficients given in Table 5. Figure 2. Plots of excess molar volume, VmE vs. mole fraction, x1 of [Bmim][OTf] for [Bmim][OTf] +

M

AN

DEGMEE binary mixtures at temperatures, T/K = 298.15, ; At T/K = 303.15, ■; T/K = 308.15, ▲; T/K = 313.15, ; T/K = 318.15, ; T/K = 323.15, ∆. The points represent experimental values and lines represent values calculated from equation (17) using the coefficients given in Table 5. Figure 3. Plots of excess molar volume, VmE vs. mole fraction, x1 of [Bmim][OTf] for [Bmim][OTf] +

ED

DEGMME, ; [Bmim][OTf] + DEGMEE, ■; binary mixtures at temperatures, T/K = 298.15.

CE

PT

Figure 4.a. Comparative excess molar volume of DEGMME for [BMIM][OTf] (▲); [BMIM][BF4] () ; [BMIM][PF6] ( ); at T/K=298.15. Figure 4.b. Comparative excess molar volume of DEGMEE for [BMIM][OTf] ( ); [BMIM][PF6] () ; at T/K=298.15. Figure 5. Plots of excess isentropic compressibility,  sE vs. volume fraction, 1 of [Bmim][OTf] for

AC

[Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■; binary mixtures at temperatures, T/K = 298.15. Figure 6. Plots of excess molar isentropic compressibility, K sE,m vs. mole fraction, x1 of [Bmim][OTf] for [Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■; binary mixtures at temperatures, T/K = 298.15. Figure 7. Plots of excess speed of sound, uE vs. mole fraction, x1 of [Bmim][OTf] for [Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■; binary mixtures at temperatures, T/K = 298.15. Figure 8. Plots of deviation in refractive index, nD vs. volume fraction, 1 of [Bmim][OTf] for [Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■; binary mixtures at temperatures, T/K = 298.15.

ACCEPTED MANUSCRIPT E

E

Figure 9. Variation of excess partial molar volumes, V m,1 and V m,2 of (a) [Bmim][OTf] and (b) alkoxyalkanol, respectively, against mole fraction, x1 of [Bmim][OTf] for the binary mixtures at T/K = 298.15. [Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■; E

E

T

Figure 10. Variation of excess partial molar volumes, K s ,m,1 and K s ,m,2 of (a) [Bmim][OTf] and (b) alkoxyalkanol, respectively, against mole fraction, x1 of [Bmim][OTf] for the binary mixtures at T/K = 298.15. [Bmim][OTf] + DEGMME, ; [Bmim][OTf] + DEGMEE, ■;

CR

IP

Figure 11. Infrared spectra between (500–4000) cm-1of (J) Pure IL [Bmim][OTf];(I) 0.9015; (H)0.6945;(G) 0.4904;(F) 0.3986; (E) 0.3064;(D) 0.2056;(C) 0.1000 and (B) Pure DEGMME. (B),(C),(D),(E),(F),(G),(H) represents mole fraction of [Bmim][OTf].

US

Figure 12. Infrared spectra between (500–4000) cm-1of (J) Pure IL [Bmim][OTf];(I) 0.8934; (H) 0.6950;(G) 0.4981;(F) 0.3934; (E) 0.2989;(D) 0.2046;(C) 0.0999 and (B) Pure DEGMME. (C),(D),(E),(F),(G),(H) and (I) represents mole fractions of [Bmim][OTf].

AN

Figure 13. IR spectra for [Bmim][OTF] + DEGMEE mixtures in the range 2800-3600 cm-1

M

Figure 14. Plots of excess molar volume, VmE vs. mole fraction, x1 of (a) [Bmim][OTf] and (b) DEGMME/DEGMEE, binary mixtures at temperatures, T/K = 298.15, ; At T/K = 303.15, ■; T/K = 308.15, ▲; T/K = 313.15, ; T/K = 318.15, ; T/K = 323.15, ∆. The lines represent experimental VmE

AC

CE

PT

ED

values and the markers represent VmE values calculated from PFP theory.

PT

ED

M

AN

US

CR

IP

T

ACCEPTED MANUSCRIPT

AC

CE

Figure 1

PT

ED

M

AN

US

CR

IP

T

ACCEPTED MANUSCRIPT

AC

CE

Figure 2

ACCEPTED MANUSCRIPT

List of Tables Table 1. Specification of chemical samples

(111-77-3) DEGMEE (111-90-0)

Degassed under vacuum

≥ 99

> 99

Fractional distillation

> 99

Fractional distillation

Sigmaaldrich, India Sigmaaldrich, India

AC

CE

PT

ED

* K.F= Karl Fisher Titrator, GC= Gas Chromatography

Water content

T

≥ 99

Analy sis metho d

IP

Iolitech, Germany

M

DEGMME

Final mole fraction purity

CR

(174899-66-2)

Purificatio n method

US

[Bmim][OTf]

Source

Initial mole fraction purity

AN

Chemical name (CAS number)

-

< 250 ppm

Water analysis method

-

≥ 99.5

GCa

< 175 ppm

KF

≥ 99.7

GCa

< 140 ppm

KF

ACCEPTED MANUSCRIPT Table 2. Comparison of experimental values of densities (ρ), speed of sound (u) and refractive index (nD) and heat capacity Cp of pure liquids with literature at different temperatures at 0.1Mpa.

323.15 DEGMME

298.15

303.15 308.15 313.15

T

IP

CR

AC

DEGMEE

318.15 323.15 298.15

US

313.15 318.15

AN

308.15

M

303.15

ED

[Bmim][OTf] 298.15

u /m·s-1 Refractive Index Cp ρ/kgm-3 EXPT LIT EXPT LIT EXPT LIT 1297.7 1297.6[18] 1392.8 1392.1[18] 1.4368 1.4375[28] 424.1[30] 1297.4[19] 1393.0[20] 1.4368[29] 1296.7[20] 1293.7 1293.7[18] 1381.7 1380.9[18] 1.4355 1.4362[28] 426.7[30] 1288.8[20] 1370.7[20] 1.4357[29] 1289.8 1289.7[18] 1370.4 1369.8[18] 1.4342 1.4347[28] 429.5[30] 1.4346[29] 1285.8 1285.8[18] 1359.5 1358.8[18] 1.4333 1.4333[28] 432.4[30] 1281.9 1281.9[18] 1348.6 1348.1[18] 1.4319 1.4320[28] 435.5[30] 1281.6[19] 1349.0[20] 1280.9[20] 1278.0 1279.9[21] 1337.9 1336.5[21] 1.4306 1.4305[28] 438.7 1278.4[13] 1015.8 1015.4[22] 1415.8 1416.0[23] 1.4254 1.4245[31] 267.4[32] 1015.9[23] 1416.4[24] 1015.8[15] 1416.0[15] 1011.4 1011.2[22] 1399.2 1399.0[15] 1.4233 1.4226[31] 268.7[32] 1011.4[15] 1006.9 1006.5[22] 1382.7 1382.5[24] 1.4212 270.1[32] 1006.9[15] 1002.5 1002.2[22] 1366.4 1366.0[15] 1.4191 1.4188[31] 271.6[32] 1002.5[15] 998.0 998.0 [15] 1349.9 1349.0[15] 1.4171 273.1[32] 993.5 993.5 [22] 1333.4 1.4150 274.7[32] 983.4 983.1 [16] 1374.8 1374.6[16] 1.4263 1.4254[31] 301.7[32] 984.2 [25] 1374.4[15] 984.3 [26] 979.1 978.9 [16] 1358.4 1356.9[16] 1.4243 1.4234[31] 303.1[32] 979.4 [23] 1356.6[15]

PT

T/K

CE

Liquid

303.15

308.15

974.6

313.15

970.1

979.7 974.5 975.3 970.1 970.8 970.9

[24] [16] 1340.9 [26] [16] 1323.4 [25] [26] 29

1339.5[16] 1.4224

304.6[32]

1322.4[16] 1.4204 1.4194[31] 306.2[32]

ACCEPTED MANUSCRIPT 318.15 323.15

965.6 961.1

965.6 [16] 1305.1 1305.1[16] 1.4183 307.9[32] 961.5 [25] 1288.8 1.4166 309.7[32] 961.5 [27] Standard uncertainties u are: u() = 0.04 kgm-3, u(u) = 0.3 ms-1, u(T) = 0.01 K, u(nD) = 0.0001, u(T)

AC

CE

PT

ED

M

AN

US

CR

IP

T

for nD = 0.02K and u(p) = 1kpa.

30

ACCEPTED MANUSCRIPT Table 3. Experimental densities, ρ, speed of sound, u, and refractive index, nD, of DEGMME with IL at entire composition range at T = (298.15- 323.15) K and atmospheric pressure 0.1MPa. Density, kg∙m-3 298.15 303.15 308.15 313.15 318.15 323.15 0.0000 1015.8 1011.4 1006.9 1002.5 998.0 993.5 0.1000 1066.6 1062.3 1058.0 1053.6 1049.3 1045.0 0.2056 1111.4 1107.2 1102.9 1098.7 1094.5 1090.3 0.3064 1147.6 1143.4 1139.3 1135.1 1131.0 1126.9 0.3986 1176.1 1172.0 1167.9 1163.9 1159.8 1155.7 0.4904 1201.1 1197.0 1193.0 1188.9 1184.9 1180.8 0.5981 1226.7 1222.7 1218.6 1214.6 1210.6 1206.6 0.6945 1246.8 1242.8 1238.8 1234.8 1230.9 1226.9 0.7795 1262.8 1258.8 1254.8 1250.8 1246.8 1242.9 0.9015 1283.1 1279.1 1275.2 1271.2 1267.3 1263.3 1.0000 1297.7 1293.7 1289.8 1285.8 1281.9 1278.0 Speed of sound, u , m∙s-1 0.0000 1415.8 1399.2 1382.7 1366.4 1349.9 1333.4 0.1000 1423.6 1408.2 1392.4 1376.8 1361.2 1345.6 0.2056 1420.5 1406.1 1391.5 1376.9 1362.4 1348.0 0.3064 1415.5 1401.6 1387.8 1374.1 1360.5 1346.9 0.3986 1410.7 1397.5 1384.4 1371.3 1358.4 1345.5 0.4904 1406.3 1393.6 1381.0 1368.4 1356.0 1343.6 0.5981 1402.2 1390.0 1378.0 1365.9 1354.0 1342.1 0.6945 1398.8 1386.9 1375.4 1363.8 1352.2 1340.7 0.7795 1396.8 1385.5 1374.0 1362.6 1351.2 1340.0 0.9015 1394.5 1383.3 1372.0 1360.9 1349.9 1338.9 1.0000 1392.8 1381.7 1370.6 1359.6 1348.8 1338.0 Refractive index, nD 0.0000 1.4254 1.4233 1.4212 1.4191 1.4171 1.4150 0.1000 1.4284 1.4266 1.4248 1.4230 1.4212 1.4194 0.2056 1.4308 1.4291 1.4274 1.4257 1.4240 1.4223 0.3064 1.4325 1.4308 1.4292 1.4276 1.4259 1.4242 0.3986 1.4340 1.4324 1.4308 1.4294 1.4277 1.4261 0.4904 1.4349 1.4334 1.4320 1.4306 1.4291 1.4276 0.5981 1.4356 1.4343 1.4329 1.4317 1.4303 1.4289 0.6945 1.4359 1.4347 1.4334 1.4323 1.4309 1.4296 0.7795 1.4362 1.4351 1.4338 1.4328 1.4315 1.4302 0.9015 1.4365 1.4353 1.4341 1.4331 1.4317 1.4305 1.0000 1.4369 1.4357 1.4344 1.4334 1.4320 1.4306 -4 −3 Standard uncertainty u(x) =1x10 , Combined expanded uncertainties Uc() = ± 0.7 kg∙m , Uc(u) = ±0.5 m∙s-1 , Uc(nD) = ± 0.0004 (Uc=kuc where k=1)

AC

CE

PT

ED

M

AN

US

CR

IP

T

X1

31

ACCEPTED MANUSCRIPT

Table 4. Experimental densities, ρ, speed of sound, u, and refractive index, nD, of DEGMEE with IL at entire composition range at T = (298.15- 323.15) K and atmospheric pressure 0.1MPa. Density, , kg∙m-3 298.15 303.15 308.15 313.15 318.15 323.15 0.0000 983.4 979.1 974.6 970.1 965.6 961.1 0.0999 1033.4 1029.2 1024.9 1020.6 1016.2 1011.9 0.2046 1079.5 1075.3 1071.1 1066.9 1062.7 1058.5 0.2989 1116.2 1112.2 1108.1 1103.9 1099.9 1095.8 0.3934 1149.2 1145.2 1141.2 1137.1 1133.1 1129.1 0.4981 1182.0 1178.0 1174.0 1170.0 1166.0 1162.1 0.5951 1209.2 1205.2 1201.2 1197.3 1193.4 1189.4 0.6950 1234.4 1230.4 1226.5 1222.6 1218.7 1214.8 0.7978 1257.8 1253.9 1250.0 1246.0 1242.1 1238.3 0.8934 1277.6 1273.7 1269.7 1265.8 1261.9 1258.0 1.0000 1297.7 1293.7 1289.8 1285.8 1281.9 1278.0 -1 Speed of sound, u , m∙s 0.0000 1374.8 1358.4 1340.9 1323.4 1305.1 1288.8 0.0999 1383.7 1368.3 1352.0 1335.7 1318.7 1303.2 0.2046 1387.9 1373.3 1358.0 1342.9 1327.1 1312.7 0.2989 1389.1 1375.0 1360.5 1346.3 1331.4 1317.7 0.3934 1388.9 1375.3 1361.5 1348.1 1334.1 1320.9 0.4981 1388.3 1375.3 1362.2 1349.4 1336.3 1323.7 0.5951 1388.1 1375.5 1363.1 1350.8 1338.3 1326.1 0.6950 1388.6 1376.5 1364.6 1352.7 1340.7 1329.1 0.7978 1389.8 1378.3 1366.8 1355.2 1343.7 1332.5 0.8934 1391.3 1380.1 1368.9 1357.6 1346.4 1335.5 1.0000 1392.7 1381.6 1370.4 1359.5 1348.6 1337.9 Refractive index, nD 0.0000 1.4263 1.4243 1.4224 1.4204 1.4183 1.4166 0.0999 1.4288 1.4268 1.4249 1.4230 1.4208 1.4191 0.2046 1.4308 1.4288 1.4269 1.4251 1.4231 1.4214 0.2989 1.4324 1.4305 1.4286 1.4269 1.4249 1.4232 0.3934 1.4338 1.4320 1.4303 1.4287 1.4267 1.4251 0.4981 1.4349 1.4332 1.4315 1.4300 1.4282 1.4266 0.5951 1.4360 1.4343 1.4326 1.4313 1.4295 1.4280 0.6950 1.4366 1.4349 1.4333 1.4321 1.4304 1.4289 0.7978 1.4369 1.4353 1.4338 1.4326 1.4310 1.4295 0.8934 1.4370 1.4356 1.4341 1.4331 1.4316 1.4302 1.0000 1.4368 1.4355 1.4342 1.4333 1.4319 1.4306 -4 −3 Standard uncertainty u(x) =1x10 , Combined expanded uncertainties Uc() = ± 0.7 kg∙m , Uc(u) = ±0.5 m∙s-1 , Uc(nD) = ± 0.0004 (Uc=kuc where k=1)

AC

CE

PT

ED

M

AN

US

CR

IP

T

X1

32

AC

CE

PT

ED

M

AN

US

CR

IP

T

ACCEPTED MANUSCRIPT

33

ACCEPTED MANUSCRIPT

Table 5.Coefficients Ai of equation (17) along with standard deviations σ of binary mixture properties. T/K A1 A2 A3 σ [Bmim][OTf] + DEGMME -0.708 -0.739 -0.784 -0.834 -0.880 -0.944

-0.187 -0.208 -0.233 -0.257 -0.289 -0.325

-0.330 -0.336 -0.334 -0.334 -0.342 -0.347

298.15 303.15 308.15 313.15 318.15 323.15 uE 10-2 m.s-1 298.15 303.15 308.15 313.15 318.15 323.15 nD 10-2 298.15 303.15 308.15 313.15 318.15 323.15

-0.201 -0.236 -0.286 -0.331 -0.387 -0.452

1.216 1.278 1.321 1.372 1.416 1.455

0.0024 0.0010 0.0012 0.0011 0.0015 0.0016 0.0022 0.0022 0.0022 0.0021 0.0022 0.0022

-0.707 -0.732 -0.746 -0.761 -0.797 -0.830

0.010 0.002 -0.008 -0.017 -0.025 -0.038

0.0010 0.0010 0.0011 0.0011 0.0012 0.0014

0.628 0.629 0.620 0.610 0.617 0.620

0.104 0.102 0.102 0.101 0.100 0.101

0.0008 0.0008 0.0008 0.0008 0.0008 0.0007

-0.327 -0.182 0.016 0.164 0.370 0.570

0.0019 0.0013 0.0013 0.0020 0.0031 0.0041

-0.036

0.0021

M

AN

US

0.242 0.245 0.241 0.236 0.240 0.240

ED

PT

AC

CE

0.023 0.044 0.075 0.100 0.130 0.165

-0.192 -0.230 -0.247 -0.254 -0.259 -0.297

IP

-2.122 -2.217 -2.328 -2.436 -2.559 -2.689

CR

298.15 303.15 308.15 313.15 318.15 323.15 E 2 -1  s m .N 298.15 303.15 308.15 313.15 318.15 323.15 E K s ,m m5.N-1 .mol-1

T

VmE /m3∙mol-1

-0.187 -0.204 -0.203 -0.206 -0.207 -0.224 [Bmim][OTf] + DEGMEE

VmE /m3∙mol-1 298.15

-2.672

-0.337 34

ACCEPTED MANUSCRIPT -2.821 -3.004 -3.201 -3.433 -3.648

-0.357 -0.398 -0.435 -0.451 -0.521

-0.043 -0.050 -0.064 -0.061 -0.093

A1

A2

A3

-1.062 -1.118 -1.191 -1.277 -1.369 -1.448

-0.205 -0.219 -0.222 -0.234 -0.243 -0.252

σ 0.0018 0.0022 0.0024 0.0024 0.0023 0.0029

-0.743 -0.782 -0.813 -0.874 -0.930 -0.981

-0.493 -0.560 -0.614 -0.638 -0.663 -0.719

0.001 0.000 0.001 0.001 0.001 0.001

1.353 1.376 1.420 1.473 1.525 1.559

0.723 0.722 0.708 0.715 0.712 0.704

0.491 0.526 0.542 0.533 0.520 0.531

0.0006 0.0006 0.0006 0.0006 0.0006 0.0005

0.967 0.915 0.870 0.819 0.770 0.721

-0.509 -0.497 -0.481 -0.460 -0.458 -0.439

0.358 0.292 0.200 0.166 0.127 0.105

0.0067 0.0056 0.0043 0.0036 0.0033 0.0027

AC

AN

M ED

PT

-1.831 -1.937 -2.080 -2.243 -2.421 -2.577

US

-0.116 -0.144 -0.168 -0.171 -0.176 -0.189

CE

2

298.15 303.15 308.15 313.15 318.15 323.15 uE 10-2 m.s-1 298.15 303.15 308.15 313.15 318.15 323.15 nD 10-2 m3.mol-1 298.15 303.15 308.15 313.15 318.15 323.15

IP

T/K  m .N-1 298.15 303.15 308.15 313.15 318.15 323.15 E K s ,m m5.N-1 .mol-1

CR

Contd., Table 5

E s

0.0009 0.0003 0.0003 0.0031 0.0010

T

303.15 308.15 313.15 318.15 323.15

35

ACCEPTED MANUSCRIPT

-1.606 -1.708 -1.791 -1.857 -1.938 -2.041

113.016 113.514 114.034 114.560 115.094 115.634

-2.372 -2.507 -2.656 -2.830 -3.043 -3.221

IP

320.115 320.932 321.698 322.449 323.206 323.892

118.283 118.800 119.325 119.854 120.390 120.936

CR

298.15 303.15 308.15 313.15 318.15 323.15

[Bmim][OTf] (1) + DEGMME (2) 222.152 -3.021 116.677 222.834 -3.187 117.093 223.520 -3.358 117.534 224.207 -3.524 117.998 224.895 -3.698 118.451 225.585 -3.930 118.895 [Bmim][OTf] (1) + DEGMEE (2) 323.161 -3.046 110.645 324.153 -3.221 111.007 325.150 -3.452 111.378 326.149 -3.700 111.731 327.151 -3.945 112.051 328.154 -4.262 112.413

US

219.131 219.648 220.162 220.683 221.197 221.655

AC

CE

PT

ED

M

AN

298.15 303.15 308.15 313.15 318.15 323.15

T

Table 6. The values Vm0,1 ,Vm,1 ,Vm0,1E ,Vm0,2 ,Vm,2 ,Vm0,2E of for the components for alkoxyalkanols with ILs at temperatures T = 298.15–323.15 K. 106Vm0,1m3  mol 1 106Vm0,1E 106Vm0,2 106Vm,2 106Vm0,2E 106Vm,1 T/K

36

ACCEPTED MANUSCRIPT

M ED PT CE AC

37

5.789 5.978 6.176 6.381 6.597 6.823

0.069 0.030 -0.027 -0.083 -0.122 -0.176

7.340 7.585 7.855 8.139 8.448 8.743

-0.701 -0.808 -0.926 -1.011 -1.092 -1.224

IP

6.539 6.558 6.562 6.547 6.528 6.628

CR

298.15 303.15 308.15 313.15 318.15 323.15

US

7.294 7.395 7.497 7.602 7.681 7.794

AN

298.15 303.15 308.15 313.15 318.15 323.15

[Bmim][OTf] (1) + DEGMME (2) 8.808 -1.514 5.858 9.004 -1.610 6.007 9.208 -1.711 6.149 9.415 -1.813 6.298 9.626 -1.944 6.475 9.842 -2.048 6.647 [Bmim] [OTf] (1) + DEGMEE (2) 8.826 -2.287 6.639 9.023 -2.465 6.777 9.228 -2.665 6.929 9.435 -2.888 7.128 9.646 -3.118 7.355 9.862 -3.234 7.519

T

Table 7. The values  s0,m,1 ,  s*,m,1 ,  s0,,mE,1 ,  s0,m,2 ,  s*,m,2 and s0,,mE,2 of for the components for alkoxyalkanols with ILs at temperatures T = 298.15–323.15 K.  s0,m,1dm3TPa 1mol 1  s*,m,1  s0,,mE,1  s0,m,2  s*,m,2  s0,,mE,2 T/K

ACCEPTED MANUSCRIPT

AC

CE

PT

ED

M

AN

US

CR

IP

T

Table 8. The values of reduced volume, , characteristic volume, V*, characteristic pressure, P*, characteristic temperature, T*, isothermal compressibility, , isentropic compressibility, ,and thermal expansion coefficient, α of pure liquids at temperatures, T = (298.15 to 323.15)K . Cp 1010 V* 106 P* 10-8 α 104 1010 T/K T*/K 2 -1 3 -1 -3 2 -1 -1 m .N m .mol J.cm m .N K [Bmim] [OTf] 298.15 1.2794 173.64 9.3162 4838 6.070 3.973 11.588 424.1 303.15 1.2855 173.34 9.4318 4852 6.220 4.049 11.710 426.7 305.15 1.2917 173.04 9.5463 4867 6.374 4.128 11.835 429.5 313.15 1.2980 172.73 9.6623 4881 6.531 4.208 11.961 432.4 318.15 1.3043 172.43 9.7798 4897 6.690 4.289 12.089 435.5 323.15 1.3106 172.12 9.8983 4912 6.852 4.372 12.219 438.7 DEGMME 298.15 1.2202 96.94 6.549 5668 5.890 4.894 8.689 267.4 303.15 1.2249 96.99 6.575 5680 6.060 5.032 8.761 268.7 305.15 1.2296 97.05 6.597 5692 6.238 5.176 8.833 270.1 313.15 1.2343 97.10 6.618 5704 6.420 5.324 8.906 271.6 318.15 1.2391 97.16 6.635 5717 6.611 5.480 8.979 273.1 323.15 1.2439 97.23 6.649 5729 6.808 5.642 9.054 274.7 DEGMEE 298.15 1.2396 110.07 6.644 5349 6.624 5.380 9.606 301.7 303.15 1.2446 110.11 6.668 5364 6.820 5.535 9.685 303.1 305.15 1.2496 110.17 6.680 5379 7.034 5.706 9.765 304.6 313.15 1.2547 110.23 6.689 5394 7.256 5.885 9.846 306.2 318.15 1.2598 110.29 6.688 5410 7.495 6.080 9.928 307.9 323.15 1.2649 110.36 6.701 5426 7.723 6.263 10.010 309.7

38

ACCEPTED MANUSCRIPT

AC

CE

PT

ED

M

AN

US

CR

IP

T

Table 9. Values of , , experimental and calculated (using PFP theory) and three PFP contributions for near equimolar composition at temperatures, T = (298.15 to 323.15)K. 106 m3.mol-1 10 10 T/K PFP contribution to J.mol-1 Expt PFP int. fv ip [Bmim][OTf] + DEGMME 298.15 0.3980 -0.451 -0.5450 -0.5347 -0.7184 -0.1704 0.3541 303.15 0.3979 -0.459 -0.5576 -0.5589 -0.7467 -0.1844 0.3722 305.15 0.3978 -0.468 -0.5853 -0.5863 -0.7780 -0.1993 0.3910 313.15 0.3977 -0.477 -0.6121 -0.6140 -0.8094 -0.2150 0.4104 318.15 0.3977 -0.485 -0.6429 -0.6446 -0.8419 -0.2316 0.4290 323.15 0.3976 -0.494 -0.6760 -0.6769 -0.8758 -0.2492 0.4481 [Bmim][OTf] + DEGMEE 298.15 0.4265 -0.566 -0.6672 -0.6691 -1.0307 -0.0719 0.4334 303.15 0.4268 -0.586 -0.7052 -0.7072 -1.0881 -0.0757 0.4567 305.15 0.4272 -0.609 -0.7513 -0.7525 -1.1557 -0.0797 0.4829 313.15 0.4276 -0.634 -0.8011 -0.8021 -1.2287 -0.0838 0.5105 318.15 0.4280 -0.663 -0.8576 -0.8587 -1.3117 -0.0880 0.5411 323.15 0.4284 -0.689 -0.9128 -0.9146 -1.3916 -0.0924 0.5695

39

ACCEPTED MANUSCRIPT

ED

M

AN

US

CR

IP

T

Graphical abstract

AC

CE

PT

IR spectra for [Bmim][OTF] + DEGMEE mixtures in the range 2800-3600cm-1

40

ACCEPTED MANUSCRIPT

Highlights



ρ, u, nD of pure and its binary mixtures of [Bmim][OTf] and DEGMME/DEGMEE have been measured. [Bmim][OTf] is less strong than other anions [BF4] and [PF6] with DEGMME and

T



IP

DEGMEE.

Partial molar properties were analyzed to understand the solute - solvent interactions.



FTIR analyses also confirmed the hydrogen bonding and interactions.

AC

CE

PT

ED

M

AN

US

CR



41