# Structural and Surface Characterization of Newly Synthesized D-π-D Type Schiff Base Ligand: (1E,2E)-3-[4-(Dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine

Authors: Gulsah Gumrukcu; Serkis Garikyan; Gulnur Keser Karaoglan; Dolunay Sakar
Journal: Journal of Chemistry
 (2013)

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## Abstract

A new Schiff base with D-π-D type, (1E,2E)-3-[4-(dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine, has been successfully synthesized using the reaction of (2E)-3-[4-(dimethylamino)phenyl]acrylaldehyde with aniline. The Schiff base ligand has been characterized by FTIR, UV-visible, and 1H NMR as well as TG/DTA, SEM, BET, and elemental analyses and mass spectra. Surface properties and acid-base constants of Schiff base ligand were determined by IGC measurements.


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## Body

## 1. Introduction

The coordination compounds including the Schiff base ligands are of significantly important and play a pivotal role in industry, technology, and life processes. Due to their potential applications in various fields, it has always fascinated and inspired chemists in the world. This can be evidenced by the vast prolificity and scope of research papers on the subject in recent times and also by the diversity in which it has found applications. Some Schiff bases and their derivatives represent an interesting class of compounds possessing a wide spectrum of biological activities, such as analgesic, antiviral, antifungal, and anticancer activities. The Schiff base ligands and their complexes have been a fascinating area of research, due to their biological relevance. These compounds can act as pro- or antioxidants. The published opinions on the structure and antioxidant activity relationships are, however, quite inconsistent. It can be assumed from several scientific works that the quality of antioxidant action depends on the type of ligands forming the bioactive complexes [1, 2].In the past few decades, very fast development in the field of organic-based conjugated materials was observed [3, 4]. Schiff bases and their metal complexes have many applications in medicinal, industrial, pharmaceutical, biological, and chemical fields. For example, they are industrially used as dyes and pigments in textile besides their application in pharmacology for the synthesis of antibiotics, antiallergic, and antitumor substances. The Schiff bases can also exhibit thermochromic and photochromic properties [5–7]. Moreover, the Schiff base compounds have been regarded as excellent fluorescent materials because of their ability to achieve high thermal stability as well as high photoluminescent efficiency. The conjugated Schiff base systems that contain electronically coupled photo- and/or redox-active sites across an unsaturated organic bridge are of considerable current interest [8–13].Many complicated factors can affect the two-photon excitation (TPE) properties of organic materials. So it is important to investigate the structure and the TPE effect relationships of organic materials. However, most of these compounds employ C=C bonds as the conjugation bridge; the compounds with C=N structure such as the Schiff bases are less studied to our knowledge [14, 15].In the present work, a new Schiff base ligand with D-π-D type which is N,N-dimethyl-4-[(1E,3E)-3-phenylimino)prop-1-en-1-yl]aniline{(1E,2E)-3-[4-(dimethylamino) phenyl]prop-2-en-1-ylidene) phenylamine (SBL) has been successfully synthesized using the reaction of (2E)-3-[4-(dimethylamino)phenyl]acrylaldehyde with aniline. It can be used as a pigment in some applications because of excellent yellow colour. The structure of the SBL was determined by elemental analysis, FTIR, UV-visible, 1H NMR, TG/DTA, and LC-MS spectrometry. In addition, IGC was applied to the investigation of adsorption properties of the SBL. The relation of SBL with used polar and nonpolar solvents was tested at temperatures between 30°C and 60°C under melting point of SBL. The goals of this paper were (1) to synthesize ad characterize new D-π-D type Schiff base ligand, (2) to figure out the surface free energy of SBL, (2) to calculate adsorption thermodynamic parameters of SBL, (3) to determine the acid-base quantity of SBL.


## 2. Experimental

### 2.1. Materials

All reagents and solvents were of reagent grade quality, obtained from commercial suppliers (Merck, USA). Aniline and (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde were used as supplied commercially from Merck. The progress of the reaction was monitored by TLC (SiO2). IR spectra were recorded on a Perkin Elmer Spectrum One FTIR (ATR sampling accessory) spectrophotometer; electronic spectra in the UV-Vis region were recorded with an Agilent 8453 UV/Vis spectrophotometer. 1H NMR spectrum was recorded in CDCl3-d6 on a Varian UNITY INOVA 500 MHz spectrophotometer using TMS as internal reference. Mass spectra were performed on a Thermo Finnigan LCQ Advantage Max LC/MS/MS. Melting point was determined on Perkin Elmer model: TG/DTA 6300 under nitrogen atmosphere. Elemental analysis was performed on a Thermo Flash EA 1112.


### 2.2. Synthesis of (1E,2E)-3-[4-(Dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine (SBL)

A solution of aniline (1) (0.79 g, 8.56 mmol) in 20 mL dry ethanol was added dropwise to a solution of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde and (2) (1.50 g, 8.56 mmol) in 10 mL dry ethanol, and the mixture was stirred under argon for 12 h at 90°C. The solvent was evaporated to 1/2 of the initial volume, and petroleum ether was added at room temperature. A yellow precipitate was obtained when the solution was cooled to room temperature. It was filtered off and then recrystallized from 2 : 1 n-hexane/ethylacetate (Figure 1). Yield 81%, m.p. 138.8°C, FTIR νmax/cm−1: 3033 (Ar, w), 2899–2809 (–CH3–, m), 1662 (HC=N, s). 1H NMR (CDCl3-d6) δ, ppm: 8.1 (d, H, HC=N) (disappeared with D2O), 6.6–7.6 (m, 4H, Ar–H), 7.0 (m, 2H, –CH=CH–), 2.92 (s, 6H, N–(CH3)2). LC-MS (APCI) m/z(100%): 250.937 [M]+. Anal. Calc. for C17H18N2 (%): C, 81.56; H, 7.25; N, 11.19. Found (%): C, 81.59; H, 7.23; N, 11.18.Figure 1
The UV-Vis spectra of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde (line) and the Schiff base ligand (dashed line) in ethanol at room temperature.


### 2.3. BET and SEM Analyses

BET analysis was carried out to determine the BET surface area and pore size of SBL. The surface area and pore size are very important application parameters as the surface contributes to the potential for interaction between the pigment and the polymer matrix [16]. Quantachrome Ins. Quadrasorb SI model BET was used in this study. The measurements were carried out under nitrogen atmosphere. SEM analysis was carried out to determine the shape of SBL with Zeiss model: EVO LS 10.


### 2.4. Inverse Gas Chromatography (IGC) Measurements

A Hewlett-Packard 6890 Model, series II, gas chromatograph with a thermal conductivity detector was used to measure the retention time of the solvents in this study. The column was stainless steel tubing with 3.2 mm o.d. and 0.5 m in length. The SBL was coated on the support by slow evaporation of chloroform as stirring the Chromosorb W in the SBL solution. Trace amount of solvent was injected into the chromatograph. The column was conditioned at 110°C for 24 h under helium atmosphere. The probes were of high purity graden-alkanes such as n-hexane (Hx), n-heptane (Hp), n-octane (O), n-nonane (N), and other acidic, basic, and amphoteric probes such as tetrahydrofurane (THF, basic), dichloromethane (DCM, acidic), chloroform (TCM, acidic), acetone (AC, amphoteric), and ethyl acetate (EA, amphoteric) were used without further purification. The all studied solvents and support materials being Chromosorb W (AW-DMCS-treated, 80/100 mesh) were supplied from Merck AG. Inc. Silane treated glass wool used to plug the ends of the column was obtained from Alltech Associates, Inc.


### 2.5. IGC Theory

The IGC technique provides a means of gaining information concerning the surface polarity of particulates and the acid-base nature of particulates. It provides a basis for determining the potential for chemical interaction between the pigment and its medium (polymer matrix or paint solutions, etc.). The material to be investigated is immobilised within a chromatographic colomn which is flushed through with inert gas such as helium or nitrogen. The stationary phase characterisation is achieved by utilising the partitioning of the sample between the mobile phase and the stationary phase, indicated by the time taken to elute the sample. The probe-probe interactions in IGC experiments are negligible because of being carried out in infinite dilution. The theory and the technique are now quite well described in the literature [16, 17].The adsorbate net retention volumesVN were calculated from the following expression:
(1)VN=Q*J*(tR-tA)*T(Tf),
where tR is the adsorbate retention time, tA is the retention time of air, Q is volumetric flow rate measured at column outlet and at ambient temperature Tf (K), T is the column temperature (K), and J the is James-Martin gas compressibility correction factor [18].The dispersive component of surface energy was determined using both the Dorris-Gray and the Fowkes methods. The adsorption energy for then-alkanes increases with the number of carbon atoms in the chain. According to Dorris & Gray (1980), the increment, corresponding to the adsorption energy of a methylene group, ΔGA[CH2] is given by [19]
(2)ΔGA[CH2]=-RTln(VN,nVN,n+1),
where VN,n and VN,n+1 are the retention volumes of two n-alkanes having n and n+1 carbon atoms in their chain. This parameter is independent of the chosen state of the adsorbed molecule. Thus, at constant temperature, for a series of alkane probes, a plot RTlnVN versus the number of carbon atoms should give a straight line from which ΔGA[CH2] can be found.The methylene adsorption energy can also be defined as [19]
(3)ΔGA[CH2]=2NAa[CH2]γSDγL[CH2],
where NA is Avagodro’s number, a[CH2] is the surface area covered by one methylene group (0.06 nm2), and γL[CH2] is the surface free energy of a surface consisting of methylene groups, that is, polyethylene, given by
(4)γL[CH2]=35.6+0.058(293-T).
Thus, using (2)–(4) and the experimentally determined values of VN,n and VN,n+1, the dispersion component of the surface free energy, γSD may be calculated.The free energy of adsorptionΔGA may also be defined in terms of the retention volume of the probes [20]:
(5)ΔGA=-RTln(VN)+K.T is the column temperature and K is a constant for a given column.Consequently, the equations may be combined to give the Fowkes equation [21]:
(6)-ΔGA=RTln(Vn)=2Na(γSD)0.5(γLD)0.5+K′′.
Thus, for a series of n-alkane probes, a plot of RTlnVN against a(γLD)0.5 will give a slope of 2N(γSD)0.5. Values of a(γLD)0.5and boiling point Tb(°C) of apolar solvents are found in the literature [22, 23].The specific component of the free energy is determined from then-alkane plot of RTln(VN) against a(γLD)0.5. The distance between the ordinate values of the polar probe datum point and the n-alkane reference line gives the specific component of the surface free energy, -ΔGAS.An equation may be written for this procedure,(7)-ΔGAS=RTln(VN,nVN,ref),
where VN,n and VN,ref are the retention volume for the polar probe and the retention volume for the n-alkanes’ reference line, respectively.The adsorption of a polar probe onto the adsorbent surface leads to a change in the enthalpy of the system and the entropy of the system. These factors are related to the energy of adsorption by the following:(8)ΔGAS=ΔHAS-TΔSAS.
Here, ΔHAS is the adsorption enthalpy by the Lewis acid-base interactions, ΔSAS is the adsorption entropy the Lewis acid-base interactions, and T is the column temperature. For each polar probe, ΔHAS and ΔSAS can be determined from a plot of -ΔGAS/T against 1/T.The surface Lewis acidity and basicity constants,KA and KD, may be calculated from the follwoing,
(9)-ΔHAS=KADN+KDAN*.
Here, DN and AN* are Gutmann’s donor and modified acceptor numbers, respectively. Values of a(γlD)0.5, boiling point, Tb(°C), Gutmann’s modified acceptor number, AN*, and donor number, DN, of the polar probes used in this study are taken from [23, 24].K
A and KD are obtained from a plot of -ΔHAS/AN* versus DN/AN* with KA as the slope and KD as the intercept. Parameters KA and KD reflect the ability of the examined surface to act as an electron acceptor and electron donor, respectively [20].


## 2.1. Materials

All reagents and solvents were of reagent grade quality, obtained from commercial suppliers (Merck, USA). Aniline and (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde were used as supplied commercially from Merck. The progress of the reaction was monitored by TLC (SiO2). IR spectra were recorded on a Perkin Elmer Spectrum One FTIR (ATR sampling accessory) spectrophotometer; electronic spectra in the UV-Vis region were recorded with an Agilent 8453 UV/Vis spectrophotometer. 1H NMR spectrum was recorded in CDCl3-d6 on a Varian UNITY INOVA 500 MHz spectrophotometer using TMS as internal reference. Mass spectra were performed on a Thermo Finnigan LCQ Advantage Max LC/MS/MS. Melting point was determined on Perkin Elmer model: TG/DTA 6300 under nitrogen atmosphere. Elemental analysis was performed on a Thermo Flash EA 1112.


## 2.2. Synthesis of (1E,2E)-3-[4-(Dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine (SBL)

A solution of aniline (1) (0.79 g, 8.56 mmol) in 20 mL dry ethanol was added dropwise to a solution of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde and (2) (1.50 g, 8.56 mmol) in 10 mL dry ethanol, and the mixture was stirred under argon for 12 h at 90°C. The solvent was evaporated to 1/2 of the initial volume, and petroleum ether was added at room temperature. A yellow precipitate was obtained when the solution was cooled to room temperature. It was filtered off and then recrystallized from 2 : 1 n-hexane/ethylacetate (Figure 1). Yield 81%, m.p. 138.8°C, FTIR νmax/cm−1: 3033 (Ar, w), 2899–2809 (–CH3–, m), 1662 (HC=N, s). 1H NMR (CDCl3-d6) δ, ppm: 8.1 (d, H, HC=N) (disappeared with D2O), 6.6–7.6 (m, 4H, Ar–H), 7.0 (m, 2H, –CH=CH–), 2.92 (s, 6H, N–(CH3)2). LC-MS (APCI) m/z(100%): 250.937 [M]+. Anal. Calc. for C17H18N2 (%): C, 81.56; H, 7.25; N, 11.19. Found (%): C, 81.59; H, 7.23; N, 11.18.Figure 1
The UV-Vis spectra of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde (line) and the Schiff base ligand (dashed line) in ethanol at room temperature.


## 2.3. BET and SEM Analyses

BET analysis was carried out to determine the BET surface area and pore size of SBL. The surface area and pore size are very important application parameters as the surface contributes to the potential for interaction between the pigment and the polymer matrix [16]. Quantachrome Ins. Quadrasorb SI model BET was used in this study. The measurements were carried out under nitrogen atmosphere. SEM analysis was carried out to determine the shape of SBL with Zeiss model: EVO LS 10.


## 2.4. Inverse Gas Chromatography (IGC) Measurements

A Hewlett-Packard 6890 Model, series II, gas chromatograph with a thermal conductivity detector was used to measure the retention time of the solvents in this study. The column was stainless steel tubing with 3.2 mm o.d. and 0.5 m in length. The SBL was coated on the support by slow evaporation of chloroform as stirring the Chromosorb W in the SBL solution. Trace amount of solvent was injected into the chromatograph. The column was conditioned at 110°C for 24 h under helium atmosphere. The probes were of high purity graden-alkanes such as n-hexane (Hx), n-heptane (Hp), n-octane (O), n-nonane (N), and other acidic, basic, and amphoteric probes such as tetrahydrofurane (THF, basic), dichloromethane (DCM, acidic), chloroform (TCM, acidic), acetone (AC, amphoteric), and ethyl acetate (EA, amphoteric) were used without further purification. The all studied solvents and support materials being Chromosorb W (AW-DMCS-treated, 80/100 mesh) were supplied from Merck AG. Inc. Silane treated glass wool used to plug the ends of the column was obtained from Alltech Associates, Inc.


## 2.5. IGC Theory

The IGC technique provides a means of gaining information concerning the surface polarity of particulates and the acid-base nature of particulates. It provides a basis for determining the potential for chemical interaction between the pigment and its medium (polymer matrix or paint solutions, etc.). The material to be investigated is immobilised within a chromatographic colomn which is flushed through with inert gas such as helium or nitrogen. The stationary phase characterisation is achieved by utilising the partitioning of the sample between the mobile phase and the stationary phase, indicated by the time taken to elute the sample. The probe-probe interactions in IGC experiments are negligible because of being carried out in infinite dilution. The theory and the technique are now quite well described in the literature [16, 17].The adsorbate net retention volumesVN were calculated from the following expression:
(1)VN=Q*J*(tR-tA)*T(Tf),
where tR is the adsorbate retention time, tA is the retention time of air, Q is volumetric flow rate measured at column outlet and at ambient temperature Tf (K), T is the column temperature (K), and J the is James-Martin gas compressibility correction factor [18].The dispersive component of surface energy was determined using both the Dorris-Gray and the Fowkes methods. The adsorption energy for then-alkanes increases with the number of carbon atoms in the chain. According to Dorris & Gray (1980), the increment, corresponding to the adsorption energy of a methylene group, ΔGA[CH2] is given by [19]
(2)ΔGA[CH2]=-RTln(VN,nVN,n+1),
where VN,n and VN,n+1 are the retention volumes of two n-alkanes having n and n+1 carbon atoms in their chain. This parameter is independent of the chosen state of the adsorbed molecule. Thus, at constant temperature, for a series of alkane probes, a plot RTlnVN versus the number of carbon atoms should give a straight line from which ΔGA[CH2] can be found.The methylene adsorption energy can also be defined as [19]
(3)ΔGA[CH2]=2NAa[CH2]γSDγL[CH2],
where NA is Avagodro’s number, a[CH2] is the surface area covered by one methylene group (0.06 nm2), and γL[CH2] is the surface free energy of a surface consisting of methylene groups, that is, polyethylene, given by
(4)γL[CH2]=35.6+0.058(293-T).
Thus, using (2)–(4) and the experimentally determined values of VN,n and VN,n+1, the dispersion component of the surface free energy, γSD may be calculated.The free energy of adsorptionΔGA may also be defined in terms of the retention volume of the probes [20]:
(5)ΔGA=-RTln(VN)+K.T is the column temperature and K is a constant for a given column.Consequently, the equations may be combined to give the Fowkes equation [21]:
(6)-ΔGA=RTln(Vn)=2Na(γSD)0.5(γLD)0.5+K′′.
Thus, for a series of n-alkane probes, a plot of RTlnVN against a(γLD)0.5 will give a slope of 2N(γSD)0.5. Values of a(γLD)0.5and boiling point Tb(°C) of apolar solvents are found in the literature [22, 23].The specific component of the free energy is determined from then-alkane plot of RTln(VN) against a(γLD)0.5. The distance between the ordinate values of the polar probe datum point and the n-alkane reference line gives the specific component of the surface free energy, -ΔGAS.An equation may be written for this procedure,(7)-ΔGAS=RTln(VN,nVN,ref),
where VN,n and VN,ref are the retention volume for the polar probe and the retention volume for the n-alkanes’ reference line, respectively.The adsorption of a polar probe onto the adsorbent surface leads to a change in the enthalpy of the system and the entropy of the system. These factors are related to the energy of adsorption by the following:(8)ΔGAS=ΔHAS-TΔSAS.
Here, ΔHAS is the adsorption enthalpy by the Lewis acid-base interactions, ΔSAS is the adsorption entropy the Lewis acid-base interactions, and T is the column temperature. For each polar probe, ΔHAS and ΔSAS can be determined from a plot of -ΔGAS/T against 1/T.The surface Lewis acidity and basicity constants,KA and KD, may be calculated from the follwoing,
(9)-ΔHAS=KADN+KDAN*.
Here, DN and AN* are Gutmann’s donor and modified acceptor numbers, respectively. Values of a(γlD)0.5, boiling point, Tb(°C), Gutmann’s modified acceptor number, AN*, and donor number, DN, of the polar probes used in this study are taken from [23, 24].K
A and KD are obtained from a plot of -ΔHAS/AN* versus DN/AN* with KA as the slope and KD as the intercept. Parameters KA and KD reflect the ability of the examined surface to act as an electron acceptor and electron donor, respectively [20].


## 3. Results and Discussion

The new Schiff base ligand was synthesized from the reaction of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde with aniline, in a good yield, as shown in Scheme 1. The IR spectrum of the SBL shows the characteristic Schiff base stretching band at 1662 cm−1. This intense band is assigned to the –C=N stretching frequency of the ligand and is characterized for the azomethine moiety of most of the Schiff base compounds. The absorption band of the C=O in (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde disappeared in the infrared spectrum of the ligands, which indicates that the condensation has occurred. The alkyl and aryl bands of the ligand are observed at 2809–2899, 1364–1448, and 1149–1151 cm−1, respectively.Scheme 1
Synthesis of the Schiff base ligand (SBL).Elemental analysis of the Schiff base ligand shows good agreement with the proposed structures. The1H NMR spectrum of the SBL in CDCl3-d6 confirmed the proposed structure showing one D2O-exchangeble proton at 8.1 ppm for the HC=N group. The assignments of the protons are highly complicated in the regions of 2.92 and 6.6–7.6 ppm, where the signals are due to the protons of the alkyl and aromatic groups.The SBL is stable at room temperature but hygroscopic. The SBL is soluble in common polar organic solvents, such as ethanol, methanol, and chloroform but partially soluble in nonpolar organic solvents, such as benzene and hexane.The UV-Vis spectral data for the SBL ligand show low-energy band at approximately 249 nm and high energy band at approximately 389 nm, due ton-π* and π-π* transitions of the azomethine group in the ligands [25, 26] (Figure 1).According to UV spectra, the peaks recorded in the spectrum are broadened and slightly red shifted (Figure1).In the mass spectra, the molecular ion peak of the L appeared atm/z(100%): 250.937 [M]+. Mass spectral data confirmed the proposed structure of the Schiff base ligand (Figure 2).Figure 2
Mass spectrum of SBL.According to BET results, the surface area and pore size of SBL were determined as 32.4 m2·g−1 and 3.056 nm, respectively. This ligand has a potential to be used in nanotechnology paint applications. The SEM micrograph of SBL was given in Figure 3.Figure 3
The SEM micrograph of SBL.The shape of SBL was determined as a rod-like structure from SEM micrograph. The retention diagrams of nonpolar and polar solvents on SBL were plotted net retention volumes,VN, of solvents on SBL which were calculated from IGC measurements between 30°C and 60°C by using (1) versus inverse temperature. According to (2), ΔGA[CH2] is independent of the chosen reference state of adsorbed molecule. The RTlnVN versus carbon number of n-alkanes were plotted in Figure 4.Figure 4
The plot ofRTlnVN versus carbon number of n-alkanes.The slope of the fitted line is equal toΔGA[CH2]. The variation of γSD according to the Dorris-Gray approach and γL[CH2] with temperature were calculated from (3) and (4), respectively. According to Fowkes, calculated values of RTlnVN were plotted against a(γLD)0.5. An example of the pattern of results obtained was given in Figure 5 for the isotherm at 303 K.Figure 5
A plot ofRTlnVN versus a(γLD)0.5 for n-alkanes and polar probes on SBL at 303 K.The results ofΔGA[CH2], γL[CH2], and γSD according to the Dorris-Gray and the Fowkes approaches were given in Table 1.Table 1
The adsorption energy of a methylene group,ΔGA[CH2], the surface free energy of a surface consisting of methylene groups, γL[CH2] and dispersion component of surface free energy, γSD, values  calculated by the Dorris-Gray and the Fowkes approaches for L determined at studied temperatures.
T (K)
γ
L
[
C
H
2
]  (mJ/m2)
Δ
G
A
[
CH
2
]  (106 mJ/mol)
Dorris-GrayγSD (mJ/m2)
Slope (×1024)
FowkesγSD (mJ/m2)
303
35.02
2.25
27.80
6.33
27.65
313
34.44
2.12
24.95
6.17
26.23
323
33.86
2.02
23.19
6.06
25.36
333
33.28
1.87
20.09
5.78
23.08The values ofγSD calculated according to the  Dorris-Gray and the Fowkes approaches are very close each to other at the studied temperature ranges. Compared to the values with the before published other Schiff base ligand γSD values, the γSD of (E)-N-((E)-3-(4-(dimethylamino)phenyl)allylidene)-4-(4-((E)-((E))-3-(4(dimethylamino)phenyl)allylidene) amino)-3-methylnaphthalen-1-yl)-2-ethylnaphthalen-1-amine as determined as 33.93 (mJ/m2) at 303 K according to the Dorris-Gray approach [7]. The values are different due to chemical nature difference between the two ligands. It can be said that when the phenyl ring is added to the Schiff base structure, γSDof ligand is increasing.The specific component of the surface free energy,-ΔGAS, is calculated using the difference between the calculated value of RTlnVN and that which was derived using the equation of the linear fit of the n-alkane reference line. By plotting the values of -ΔGAS/T against 1/T, the adsorption enthalpy, ΔHA,S and the adsorption entropy, ΔSAS were determined for each studied polar probe. The values of KA and KD were calculated using (9). The plotting -ΔHAS/AN* versus DN/AN* with KA as the slope and KD as the intercept (Figure 6).Figure 6
The plot of-ΔHAS/AN* versus DN/AN*.The values ofKA and KD are found to be 0.1 and 0.6, respectively. According to the values obtained for KA and KD, the surface of SBL is the basic character between 30–60°C.


## 4. Conclusions

In this study, a new Schiff base ligand with D-π-D type has been successfully synthesized using the reaction of (2E)-3-[4-(dimethylamino) phenyl]acrylaldehyde with aniline and characterized by FTIR, UV-visible, 1H NMR, elemental analysis, and mass spectrum for structural characterization and BET, SEM, and IGC for surface characterization. The big surface area and small pore size of SBL were determined from the BET result. It can be used in nanotechnology paint applications. In addition, IGC was applied to the investigation of adsorption properties of the SBL. The relation of SBL with used polar and nonpolar solvents was tested at temperatures between 30°C and 60°C in which SBL does not show any thermal transition. The base constant of newly synthesized SBL was determined as 0.64, while acid constant is 0.1.



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