Spectral properties of bisphenol F based on quantum chemical calculations

Vacuum 128 (2016) 198e204

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Spectral properties of bisphenol F based on quantum chemical calculations H. Wang a, b, Y.P. Zhao c, Y.J. Zhu d, J.Y. Shen a, * a

Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, Jiangsu, PR China New Energy Chemicals Inc., Yancheng 224300, Jiangsu, PR China c School of Petrochemical Engineering, Changzhou University, Changzhou 213164, Jiangsu, PR China d School of Chemistry and Chemical Engineering, Anhui University, Hefei 230601, Anhui, PR China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 13 January 2016 Received in revised form 22 March 2016 Accepted 23 March 2016 Available online 31 March 2016

The quantum chemical calculation method is used in this paper to study the energy difference between the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of three bisphenol F (BPF) isomers. The results show that the minimum energy difference occurs at 4,4'-dihydroxydiphenylmethane (4,40 -BPF); the middle energy difference occurs at 2,4'-dihydroxydiphenylmethane (2,40 -BPF); and the maximum energy difference occurs at 2,2'-dihydroxydiphenyl- methane (2,20 -BPF). Based on these results, the electron transition in 4,40 -BPF is easier than that in 2,40 -BPF, while the electron transition in 2,20 -BPF is the most difficult. This paper investigates the effect of the hydroxyl group, specifically concerning the spectroscopic properties of BPF isomers by observing the solvent effect, hydroxyl group amount and the element substitution of an oxygen atom in the hydroxyl group. The solvent effect results show that infrared spectroscopy intensity increases significantly for 4,40 -BPF in the polar solvent (methanol and water), but does not increase proportionally to the electric constant increase of the polar solvent. The multi hydroxyl substitution of BPF isomers results show that with an increase in the hydroxyl group amount, new characteristic peaks occur in FTIR spectra and Raman spectra, while the characteristic peaks in UV spectra are smoother in the range of 240e300 nm. The element substitution results show that the red shifts occur in a different element substituted 4,40 -BPF isomer in UV spectra, and the red shifts order is opposite of that involving substitution element electronegativity. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Bisphenol F Quantum chemical calculation Isomer distribution Spectroscopic properties

1. Introduction Bisphenol F (BPF) is an important chemical intermediate used in synthesizing epoxy resin and polycarbonate. Its chemical name is dihydroxydiphenylmethane and it is composed of three isomers including 4,4’-dihydroxydiphenylmethane (4,40 -BPF), 2,4’-dihydroxydiphenylmethane (2,40 -BPF), and 2,2’-dihydroxydiphenylmethane (2,20 -BPF) as shown in Fig. 1. The common characteristic of isomer distribution in the synthetic products is that the relative content of 4,40 -BPF is the highest while that of 2,20 -BPF is the least. Currently, the research on BPF focuses on two fields. One is the development of new acid catalysts [1e5], and the other is the optimization of BPF isomers product distribution, especially to increase the relative content of 4,40 -BPF [6,7]. Chen et al. [6]

* Corresponding author. E-mail addresses: [email protected] (H. Wang), [email protected] (J.Y. Shen). http://dx.doi.org/10.1016/j.vacuum.2016.03.024 0042-207X/© 2016 Elsevier Ltd. All rights reserved.

synthesized two types of BPF with different isomer contents. The corresponding diglycidylethers (BPFEP-a and BPFEP-b) were also derived. They studied the effect of isomer content in relation to the curing reaction characteristic of BPFEP with 4,4’-diaminodiphenylmethane (DDM) hardener. Their work shows that the reactivity of BPFEP is low with a higher content of 4,40 -BPF, which is good for the functional group to fully react to form a complete network structure. In US Pat. No. 4,400,554, phosphoric acid is used as the catalyst for phenol and formaldehyde to synthesize BPF. The study shows that water has a significant effect on BPF isomer distribution during the synthesis process. First, phenol and formaldehyde react to form 2-(hydroxymethyl)phenol and 4-(hydroxymethyl)phenol in the presence of Hþ. Next, 4-(hydroxymethyl)phenol and phenol react continuously to produce 4,40 -BPF and 2,40 -BPF; whereas 2(hydroxymethyl)phenol and phenol react continuously to produce 2,40 -BPF and 2,20 -BPF. The most noticeable effect of water is the inhibition of the 2-(hydroxymethyl)phenol and phenol reaction,

H. Wang et al. / Vacuum 128 (2016) 198e204

199

wavelength of 240e800 nm and a resolution ratio of 0.1 nm.

HO HO

OH

OH 4,4'-BPF

OH

OH

2,4'-BPF

2,2'-BPF

Fig. 1. Chemical structural formula of three BPF isomers.

resulting in the formation of a predominant amount of 4,40 -BPF, a minor amount of the 2,40 -BPF and a negligible amount of the 2,20 BPF. It is believed that this is because the reaction of 2-(hydroxymethyl)phenol with phenol and BPF is inhibited. Wang et al. [8] studied the effect of solvent to BPF isomer distribution. By investigating polar nonprotic and protic solvents, the work shows that using one or two more mixture of polar nonprotic solvent in the BPF synthesis process can significantly increase the relative content of 4,40 -BPF isomer. All of the studies above confirms that there is some relationship between BPF isomer distribution and the reaction solvent. One of our objectives in this paper is to describe the common characteristics of BPF isomer distribution in a molecular scale and compare the reaction solvent effect to spectroscopic properties of BPF isomers. The work will also provide some theoretical instruction to optimize the BPF isomer distribution in engineering. Quantum chemistry and related calculations provide a useful way for researchers to study the microcosm. Previous research on BPF based on the quantum chemistry calculation method has generally moved in three directions, including: (1) thermodynamic properties and the mechanism of phase transitions [9]; (2) metabolic mechanism, formation mechanism and toxicity [10]; (3) and spectroscopic properties [11,12]. The research on spectroscopic properties mostly focuses on common spectroscopic characteristics from a macroscopic perspective of bisphenol (bisphenol A, bisphenol S, bisphenol E, bisphenol F and bisphenol AP). Currently, there is little research on the effect of a hydroxyl group on spectroscopic properties of BPF isomers from the hydroxyl group perspective. In this paper, the FTIR spectra, Raman spectra and UV spectra of 4,40 -BPF, 2,40 -BPF, and 2,20 -BPF were tested and analyzed. The reliability of the quantum chemistry calculation model was validated by comparing the simulation spectra and the measured spectra. The electron population and transition properties of BPF isomers were studied using the simulation calculation method. Additionally, the hydroxyl group's effects on spectroscopic properties of BPF isomers were investigated by evaluating the solvent effect, the hydroxyl group amount, and using element substitution of the oxygen atom in the hydroxyl group.

2. Experimental procedure

2.2. Calculation model and parameters DMol3 Module was used in the simulation process. GGA (Generalized Gradient Approximation) and PW91 [13,14] were chosen to simulate the spectral properties. Effective Core Potentials standards were used for Core treatment, whereas DNP was utilized to establish a Basis set, which used 4.4 as a value for the Basis file. The cut-off radius is 3.7 A. The convergence accuracy of SCF is 106. The effects of a hydroxyl group on the spectroscopic properties of BPF isomers were investigated by observing the solvent effect, the hydroxyl group amount, and by using element substitution of an oxygen atom in the hydroxyl group. The solvent effect model used was the Conductor-like Screening Model (COSMO) of Polarizable Continuum Model (PCM) [15]. In the solvent effect model simulation, different solvents are established by setting different electric constants. The electric constant is 78.54 for water and is 32.63 for methanol medium. For comparison purposes, the electric constant in vacuum was set as 1. Fig. 2 and Fig. 3 show the chemical structural formula of multi-hydroxyl substituted BPF isomers and elements substituted 4,40 -BPF, respectively. Note that the quantum chemistry calculation method is the same for studies on spectroscopic properties of multi-hydroxyl substituted BPF isomers, elements substituted 4,40 -BPF, and the solvent effect of the hydroxyl group. 3. Results and discussion 3.1. Spectral analysis of BPF and validation of quantum chemistry calculation model Fig. 4 shows the FTIR spectra, Raman spectra and UV spectra of the BPF isomers based on experiments. The results of the FTIR spectra, as demonstrated in Fig. 4(a), indicate that the positions of the BPF isomers' characteristic peaks show little variation; however, the strength of the BPF isomers' characteristic absorption peaks vary significantly. The stretch vibration absorption characteristic peak of the OeH is at 3350 cm1. Moreover, the comparisons show that the strength of the stretch vibration characteristic peak of the OeH at 2,20 -BPF is higher than that at 2,40 -BPF and 4,40 BPF. One possible explanation is that the distance between the OeH groups at 2,20 -BPF is relatively smaller; therefore, electron transition and electronic coupling occurs more easily, which enhances the strength of the stretch vibration characteristic peak of the OeH. As down in Fig. 4(b), the Raman spectra indicates that the strength of the stokes peak of the 2,20 -BPF is higher than that of the 2,40 -BPF and 4,40 -BPF in the high wavelength range, which is similar to the results found in the FTIR spectra. The FTIR spectra indicates that dipole moment variation or electron distribution variation occurs, due to molecule vibration. Furthermore, the Raman spectra indicates the presence of temporary polarization due to the transient deformation of the chemical bonds in the electron cloud

2.1. Material and analysis method Standard samples of 4,40 -BPF, 2,40 -BPF, and 2,20 -BPF (not less than 99 wt%) were purchased from TCI (Shanghai) Development Co., Ltd. The FTIR spectra was obtained from a Thermo Fisher Scientific Nicolet-370 spectrometer. The samples were palletized with KBr within a scanning range from 450 to 4000 cm1. The Raman spectra was tested on a Renishaw inVia spectrometer. The wavelength of the incident light was 532 nm, and the exposure time was 5 s, with a cycling time of 3 s at 100% strength. The UV spectra was obtained on a UV-3600 ultraviolet spectrophotometer with a

OH HO

OH

HO OH

2,4,4'-BPF

OH

OH

HO OH

OH OH

2,4,4',6-BPF

OH 2,2',4,4',6-BPF

Fig. 2. Chemical structural formula of the multi-hydroxyl substituted BPF isomers.

200

H. Wang et al. / Vacuum 128 (2016) 198e204

3.2. Molecule orbitals and electron distribution of BPF isomers

HO

HO

HO PH2

SH 4,4'-BPFS

The highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) were hybridized by the 2p orbital of the C atom and 2p orbital of the O atom. The energy difference (DE) between the HOMO and LUMO values reflects the level of difficulty for an electron transition. Table 1 shows the energy difference of the three BPF isomers. The DE of the 2,20 -BPF is the largest value, followed by the DE of the 2,40 -BPF, and finally, the

NH2

4,4'-BPFP

4,4'-BPFN

Fig. 3. Chemical structural formula of the elements substituted 4,40 -BPF.

2,2'-BPF

100

120

Intensity (arb.units)

Intensity (km. mol-1)

90

2,4'-BPF

90 60 120

4,4'-BPF

80 40 0 0

1000

2000

3000

Wavenumber (cm-1)

4000

0.6

50 2,2'-BPF 40 30 20 10 0 25 2,4'-BPF 20

0.2 0.6

15 10 5 0 25 20 4,4'-BPF 15 10 5 0 -5 0 1000

2,4'-BPF

0.4 0.2 0.20

4,4'-BPF

0.15 0.10

2000

3000

Wavenumber (cm-1)

(a)

2,2'-BPF

0.4

Osc. strength

110

(b)

4000

0.05 240

260

280

300

Wavelength (nm)

(c)

Fig. 4. The FTIR spectra (a), Raman spectra (b), and UV spectra (c) of three BPF isomers based on experiments.

distribution, resulting in a change in polarizability. In terms of the 2,20 -BPF, the decrease in the distance between the OeH groups changes the resulting dipole moment and polarizability, which might explain the increase in strength of the stokes peak in the high wavelength range. The comparisons of the UV spectra of BPF isomers in Fig. 4(c) show that the shapes of the UV absorption peaks are similar for all three isomers in the range of 240e300 nm. The maximum absorption wavelength is 270 nm for the three isomers, which is consistent with the existing literature [16]. Fig. 5 compares experimental data and simulation data for the FTIR spectra, Raman spectra, and UV spectra of the 4,40 -BPF. Fig. 5(a) indicates that the spectra that was obtained from the simulation and experimental data agree well for low frequency. However, in terms of the high frequency range, the positions of the BPF characteristic peaks in the simulation data vary significantly from those in the experimental data. One possible explanation for this difference is that the GGA cannot accommodate the stretching vibration of the CeH bond under high frequency. However, it is important to note that the selection of GGA does not have a significant impact on the spectroscopic properties of the BPF isomer. The aforementioned results show that the simulation data obtained by the quantum chemistry calculation method and the experimental data are in accordance with one another. Therefore, the quantum chemistry calculation results as provided here are reliable substitute of experimental tests.

DE of the 4,40 -BPF is the smallest value. Therefore, the electron

transition in the 4,40 -BPF is easier than that in the 2,40 -BPF, whereas the electron transition in the 2,20 -BPF is the most difficult. For all three BPF isomers, the electrophilic reaction easily occurs around the O atoms, while the nucleophilic reaction easily occurs around the C atoms and H atoms. As shown in Table 2, the oxygen Mulliken electric charges are 0.460, 0.470, and 0.490 for the 4,40 -BPF, 2,40 -BPF, and 2,20 -BPF, respectively. The OeH Mayer bond order is 1.072, 1.079, and 1.077 for the 4,40 -BPF, 2,40 -BPF, and 2,20 -BPF, respectively. These results further proved that the OeH bond in the 4,40 -BPF is easier to break than that in the 2,40 -BPF and 2,20 -BPF. 3.3. Effect of hydroxyl group to spectroscopic properties of BPF isomers

3.3.1. Solvent effect Fig. 6 shows the FTIR spectra, Raman spectra, and UV spectra of the 4,40 -BPF in solvents (methanol and water) and in vacuum based on simulation. Fig. 6(a) shows that the strength of the FTIR absorption peak in methanol and water significantly increases in comparison with that in vacuum, which may be due to molecule vibration enhancement. In addition, the strength of the hydroxyl stretching vibration characteristic peak increases significantly in the high frequency area, which is possibly due to hydroxyl vibration enhancement in the polar solvent. However, in different polar solvents, the strength of the infrared absorption peak does not proportionally increase along with the increase in the electric

Intensity (km. mol-1)

H. Wang et al. / Vacuum 128 (2016) 198e204

120 100 Experiment 80 60 40 20 0 500 1000 1500 240 Simulation 200 160 120 80 40 0 -40 500 1000 1500

Table 1 The HOMO and LUMO energy level of three BPF isomers.

4,40 -BPF 2,40 -BPF 2,20 -BPF

2000

2000

2500

2500

3000

3000

Wavenumber (cm-1)

3500

3500

4.0x10-4

4000

Experiment

Intensity (arb.units)

3.0x10-4 -4

2.0x10

1.0x10-4 0.0 500 1000 3.0x10-3 Simulation 2.0x10-3

1500

2000

2500

3000

3500

4000

1500

2000

2500

3000

3500

4000

1.0x10-3 0.0 -1.0x10-3 500

1000

Wavenumber (cm-1)

(b) 0.20

Experiment

Osc.strength

0.15 0.10 0.05 240 250 0.15 Simulation

260

270

280

290

300

260

270

280

290

300

0.10 0.05 0.00 240

250

HOMO energy level (a.u.)

LUMO energy level (a.u.)

DE (a.u.)

0.189 0.194 0.202

0.043 0.046 0.045

0.146 0.148 0.157

4000

(a) 5.0x10-4

201

Wavelength (nm)

(c) Fig. 5. Comparison with experimental data and simulation data in the FTIR spectra (a), Raman spectra (b), and UV spectra (c) of the 4,40 -BPF.

constant of the solvent. The results in Fig. 6(b) demonstrate that the variation in the stokes peaks and anti-stokes peaks of the Raman spectra is limited for the 4,40 -BPF in the polar solvent (water and

methanol) and in vacuum, which may be due to the fact that the Raman spectra is a scattering spectra, and the solvent effect is too small to trigger a scattering effect. Fig. 6(c) shows a comparison between the UV absorption characteristic peaks in vacuum and in the polar solvent. In the polar solvent, the characteristic peak strength increases slightly between 200 and 240 nm, whereas the strength decreases slightly between 240 and 300 nm with a smoother characteristic peak. This smoother characteristic peak may have occurred because the hydroxyl group of the BPF isomers and the polar solvent generate the hydrogen bond. Since the hydroxyl vibration effect causes the detailed structure to disappear, the characteristic peak appears to be smoother. 3.3.2. Spectroscopic properties study of multi-hydroxyl substituted BPF isomers Fig. 7 shows the FTIR spectra, Raman spectra, and UV spectra of the multi-hydroxyl BPF isomers based on simulation. Along with the increase of hydroxyl group amount, two, new absorption characteristic peaks occur at high frequencies of 3545 and 3598 cm1 as shown in Fig. 7(a). The two, new hydroxyl stretching vibration characteristic peaks are in the C-2 and C-6 positions of the BPF at 3598 cm1. In particular, the hydroxyl stretching vibration characteristic peak in the C-20 position of the BPF is at 3545 cm1. Since there are two symmetric hydroxyl groups in the C-2 and C-6 positions, the hydroxyl group amount is larger than that in the C-20 position. Therefore, the strength of the characteristic peak at 3598 cm1 is higher than that at 3545 cm1. The Raman spectra in Fig. 7(b) shows that two, new Raman scattering peaks occur at 3550 and 3575 cm1 along with an increase in the hydroxyl group amount. The two, new symmetric hydroxyl characteristic scattering peaks in the C-2 and C-6 positions of the BPF occur at 3575 cm1. To be more specific, the hydroxyl characteristic scattering peak in the C-20 position of the BPF is at 3550 cm1. The variations of the characteristic peak strength in the Raman spectra is similar to that in the FTIR spectra. The UV spectra in Fig. 7(c) indicates that the absorption peak strength decreases between the 200 and 240 nm range and between the 240 and 300 nm range, along with the hydroxyl group amount increase. The characteristic peaks between 240 and 300 nm range become smoother, possibly because the interactions among the hydroxyl groups are more intense and the red shifts become more obvious as the hydroxyl group amount increases. However, the 2,20 ,4,40 ,6-BPF is a special case, because it shares a similar UV absorption peak shape with the 2,20 -BPF. 3.3.3. Spectroscopic properties study of elements substituted 4,40 BPF Fig. 8 shows the FTIR spectra, Raman spectra, and UV spectra of the elements substituted 4,40 -BPF based on simulation. As shown in Fig. 8(a), two, new absorption peaks occur at 2350 and 2390 cm1 for the 4,40 -BPFP, while no significant peaks occur at these positions for the 4,40 -BPFN and 4,40 -BPFS. One possible explanation for this difference is the fact that the -PH2 are perpendicular to the phenyl ring in the 4,40 -BPFP, while the -SH and -NH2 are parallel to the phenyl ring in the 4,40 -BPFN and 4,40 -BPFS. Thus, with the exception of the PeH bond stretching vibration absorption peaks, there are PeH bond bending vibration peaks in the 4,40 -BPFP. Fig. 8(b)

202

H. Wang et al. / Vacuum 128 (2016) 198e204 Table 2 The Oxygen atom mulliken charges and OeH mayer bond order of three BPF isomers.

4,40 -BPF 2,40 -BPF 2,20 -BPF

1.072 1.079 1.077

60

Methanol

0

400

60

Intensity (arb. units)

Intensity (km. mol-1)

0

Water

200 100 0

Vacuum

100

20

0

0 2000

3000

-20 0

4000

0.4

Water

0

40

1000

0.0

20

200

-100 0

0.1

40

60

Wavenumber (cm-1)

Vacuum

15

2,2',4,4',6-BPF

10

2,4,4',6-BPF

Intensity (arb. units)

Intensity (km. mol-1)

0 15

200 0

2,4,4'-BPF

200 0 300 200

4,4'-BPF

100 0 -100 0

1000

2000

0.0 0.4 0.3

Vacuum

0.0

1000

2000

3000

-0.1 200

4000

220

240

3000

Wavenumber (cm-1)

4000

10

300

in solvents (methanol and water) and in vacuum based on simulation.

0.08 2,2',4,4',6-BPF 0.06 0.04 0.02 0.00 0.3 2,4,4',6-BPF 0.2

2,2',4,4',6-BPF

2,4,4',6-BPF

0 10

280

(c)

4,40 -BPF

5 15

260

Wavelength (nm)

5

600

400

0.1

(b)

0

600

0.2

Wavenumber (cm-1)

200

400

Water

0.1

Fig. 6. The FTIR spectra (a), Raman spectra (b), and UV spectra (c) of the

400

0.3

0.2

(a)

600

Methanol

0.2

20

100

300

0.3

40

200

300

0.4

Methanol

Osc. strength

300

Mayer bond order of the OeH bond

0.460 0.470 0.490

Osc. strength

400

Mulliken charges of the oxygen atom

2,4,4'-BPF

5 0

0.1 0.0 0.3 0.2

2,4,4'-BPF

0.1 0.0

20 15 4,4'-BPF 10 5 0 -5 0 1000

2000

3000

Wavenumber (cm-1)

(a)

(b)

4000

0.4 0.3 4,4'-BPF 0.2 0.1 0.0 -0.1 200 220 240

260

280

300

320

Wavelength (nm)

(c)

Fig. 7. The FTIR spectra (a), Raman spectra (b), and UV spectra (c) of the multi-hydroxyl BPF isomers based on simulation.

demonstrates a comparison between the Raman spectra of 4,40 BPFN, 4,40 -BPFS, and 4,40 -BPFP. From the comparisons, we can see that a new Raman scattering peak occurs at 2680 cm1 in the 4,40 BPFS. Two, new Raman scattering peaks occur at 2350 cm1 in the 4,40 -BPFP and an additional two, new Raman scattering peaks occur

at 3500 cm1 in the 4,40 -BPFN. These differences may be based on the fact that element N has a maximum electronegativity, element S has the second maximum electronegativity, and element P has the minimum electronegativity. Different electronegativity values generate significant polarizability differences for the various

H. Wang et al. / Vacuum 128 (2016) 198e204

600

20

4,4'-BPFN

400

0.4 0.3 4,4'-BPFN 0.2 0.1 0.0 0.15 4,4'-BPFP 0.10

4,4'-BPFN

10

200

0 20

Intensity (arb. units)

4,4'-BPFP

200 100 0 300

4,4'-BPFS

200 100 0 300

0 20

4,4'-BPFS

10 0 20

4,4'-BPF

200

4,4'-BPFP

10

Osc. strength

0 300

Intensity (km. mol-1)

203

4,4'-BPF

10

100 0

0 -100 0

1000

2000

3000

Wavenumber (cm-1)

4000

-10 0

1000

2000

3000

4000

Wavenumber (cm-1)

(a)

0.05 0.00 0.4 0.3 4,4'-BPFS 0.2 0.1 0.0 0.4 4,4'-BPF 0.3 0.2 0.1 0.0 -0.1 200 220 240

260

280

300

320

Wavelength (nm)

(c)

(b)

Fig. 8. The FTIR spectra (a), Raman spectra (b), and UV spectra (c) of the elements substituted 4,40 -BPF based on simulation.

elements substituted BPF isomers. Thus, the scattering photons of the different elements substituted BPF isomers release different amount of energy when they return to a ground state, which results in the appearance of new anti-stokes peaks. Fig. 8(c) indicates that there are some red shifts in the different elements substituted BPF isomers, especially for the 4,40 -BPFP, which is closely related to the difference in electronegativity levels, directly changes the DE of the 4,40 -BPFN, 4,40 -BPFS, and 4,40 -BPFP, as shown in Table 3. These conclusions are consistent with those found by Sun et al. [17] and Shinde et al. [18] in previous studies.

Comparing the energy difference between the HOMO and LUMO for three BPF isomers reveals that the energy difference of the 2,20 BPF is the largest amount, followed by the 2,40 -BPF, and finally, the energy difference of the 4,40 -BPF is the smallest amount. Therefore, the electron transition in the 4,40 -BPF is easier than the electron transition in the 2,40 -BPF, whereas the electron transition in the 2,20 -BPF is most difficult. Based on the results of the solvent effect study, the FTIR absorption peak strength of the 4,40 -BPF increases significantly in a polar solvent; however, it does not proportionally increase along with the increase in the electric constant of the solvent. Additionally, the Raman spectra variation of the 4,40 -BPF in the polar solvent is limited compared to that found in vacuum. The spectroscopic properties study of the multi-hydroxyl substituted BPF isomers indicate that new characteristic peaks occur in the FTIR spectra and Raman spectra along with an increase in the hydroxyl group amount. The characteristic peaks in the UV spectra between 240 and 300 nm also become smoother. From the results of the spectroscopic properties study of various elements substituted

Table 3 The HOMO and LUMO energy level of the elements substituted 4,40 -BPF.

4,4 -BPFN 4,40 -BPFS 4,40 -BPFP

Acknowledgements The Technology Innovation Foundation of Jiangsu Province of China (BC2014193) is acknowledged. This work was also supported by Jiangsu Province Graduate Student Work Station. References

4. Conclusion

0

4,40 -BPF, the red shifts occur in the UV spectra. The order of the red shifts is the opposite of the order of the substitution element electronegativity values.

HOMO energy level (a.u.)

LUMO energy level (a.u.)

DE (a.u.)

0.174 0.199 0.189

0.037 0.056 0.049

0.137 0.143 0.140

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