Synthesis, photophysical and electrochemical properties of symmetric silicon-linked diphenyl 1,3,4-oxadizole derivatives

Tetrahedron 71 (2015) 2680e2685

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Synthesis, photophysical and electrochemical properties of symmetric silicon-linked diphenyl 1,3,4-oxadizole derivatives Dongfeng Li a, Zhuo Huang a, Xiaohong Shang a, Yan Xia a, Yuandong Zhang a, Min Li c, Bao Li d, *, Ruibin Hou a, b, * a

School of Chemistry and Life Science, Changchun University of Technology, Changchun 130012, China Advanced Institute of Materials Science, Changchun University of Technology, Changchun 130012, China College of Materials Science Engineering, Jilin University, Changchun 130012, China d State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 December 2014 Received in revised form 12 February 2015 Accepted 9 March 2015 Available online 19 March 2015

A series of novel, symmetric, silicon-linked, V-shaped, organic fluorescent compounds 1aec with an electron-deficient 1,3,4-oxadizoles unit and a diphenyl moiety were successfully synthesized. We show that the Si atom possesses a special V-shaped structure that weakens pep stacking resulting in aggregation-induced emission. This new type of compound may show tunable light emission in solution and in a solid-state thin film. Theoretical calculations were used to analyze the frontier molecular orbitals of the two compounds. The HOMO and LUMO energy levels of the studied compounds range from
1.55 to
1.78 eV and from
5.70 to
6.15 eV, indicating that they will function well as electron transport materials. Ó 2015 Elsevier Ltd. All rights reserved.

Keywords: 1,3,4-Oxadizoles Electron-transporting materials Theoretical calculation

1. Introduction Fluorescent organic molecules are widely used as the active elements in organic light-emitting diodes, bioprobes, and chemosensors.1e5 However, most of these compounds only have reasonable emission in dilute solution and their emission in condensed phases such as thin films or aggregates is far weaker or nonexistent owing to the notorious effect of aggregation-caused quenching.6 Tang’s group and others have separately reported an intriguing phenomenon wherein aggregated molecules are able to fluoresce more intensely than their dilute solutions.7,8 Propellershaped molecules such as tetraphenylethene, hexaphenylsilole and quinolinemalononitrile as well as their derivatives are nonemissive when molecularly dissolved,9e12 but they are induced to emit efficiently upon aggregate formation. Recently, a new V-shaped compound has displayed a new phenomenon where tunable light emission was obtained in solution and in the solid state.13 Discussions about whether intermolecular distance and molecular shape affects fluorescence are rare. This gap in knowledge strongly encouraged us to develop a new V-shaped dye molecule with tunable light emission both in solution and in the solid state.

* Corresponding authors. Tel./fax: þ86 43185716671; e-mail addresses: libao@ jlu.edu.cn (B. Li), [email protected] (R. Hou). http://dx.doi.org/10.1016/j.tet.2015.03.039 0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

We studied the relationship between structure and optical properties. Recently, organosilicon compounds have become the focus of several research efforts after several recent reports indicated that organosilicon compounds, especially siloles, have excellent emission properties.7,8,10 Si-based tetrahedral organic molecules and polymers have been intensively investigated as luminescent materials. For example, Liu and co-workers recently reported a series of tetrahedral luminescent materials comprising SiAr4 cores. They found that their fluorene derivatives were efficient blue lightemitting materials and that Si-centered materials were superior with regard to film formation ability and quantum efficiency. A noteworthy feature of Si-centered tetrahedral materials is their high photoluminescence (PL) efficiency (nearly 100%) in the condensed state.14 Herein, we report the development of V-shaped Si-based luminescent materials. We show that Si possesses a special V-shaped structure, which weakens pep stacking. We chose 1,3,4oxadiazoles as building units because they are classic heterocyclic compounds that have attracted significant interest for use in organic light-emitting diodes. They are well-known electronic transmission materials. We found that the new V-shaped molecule shows strong and tunable light emission in solution and as a solidstate film.

D. Li et al. / Tetrahedron 71 (2015) 2680e2685

O HO C

CH3 Si CH3 2

O C OH

C2H5OH H2SO4

(1) R

O H2NHN C

CH3 Si CH3

O C NHNH2

O EtO C

2681

CH3 Si CH3 3

O C OEt

NH2NH2/H2O

COCl

5 (2) POCl3

CH3 Si CH3

N N R

O

4

1a -1c

N N O

R

a: R = H b: R = OC4H9 c: R = OC6H13

Scheme 1. The synthetic route of 1aec.

Crystal data were measured using a Rigaku SCX minidiffractometer with Mo-Ka radiation (l¼0.71073  A) in u scan mode at 296(2) K. Ultraviolet-visible (UVevis) spectra were recorded on a Lambda 25 spectrophotometer in CHCl3 (10
5 M). Fluorescence spectra were obtained from a Shimadzu RF-5301PC fluorescence spectrophotometer. Cyclic voltammetric studies were carried out using a CHI 852C instrument with DMF as the solvent (10
3 M) and 0.1 M Bu4ClO4 as the supporting electrolyte. Counter and working electrodes consisted of a Pt wire and a Pt disk, respectively, and the reference electrode was Ag/AgCl. The thermal stability of the target compounds was characterized using a Shimadzu DTG-60H thermogravimetric analyzer.

illustrated in Fig. 1c and d, the symmetry unit of compound 1c also consists of one crystallographically molecules with the dihedral of 89.6(1) between two diphenyl 1,3,4-oxadizole moieties. Different from the compound 1a, compound 1c has more abundant hydrogen bonds. The strong intermolecular CeH$O hydrogen bonds link two molecules into dimer with the distance between C13 and O2 of 3.432(3)  A. The intermolecular CeH$N hydrogen bonds link the molecular into 2D network along ac direction with distances between C24 and N1, C2 and N1, C18 and N3 of 3.552(4)  A, 3.592(4)  A and 3.580(4)  A, respectively. The 2D networks are further linked by the dimers and form a three-dimensional supramolecular network. Crystallographic data for the structures of 1a and 1c have been deposited with the Cambridge Crystallographic Data Centre as supplemental publications CCDC 924401 and CCDC 924497.

2.1. Synthesis and crystal structures

2.2. Photophysical and electrochemical properties

The synthetic procedures for target compounds 1aec are summarized in Scheme 1. 4,40 -dihydrazidediphenyldimethylsilane 4 was prepared from 4,40 -dicarboxylesterdiphenyldimethylsilane 3 with excess hydrazine hydrate in ethanol. The reaction mixture was heated slowly to 80  C and refluxed overnight. The final target compounds 1aec were obtained by condensation reactions between 4,40 -dihydrazidediphenyldimethylsilane 4 and benzoyl chloride in phosphoryl chloride (POCl3) as the refluxing solvent. Compounds 1aec were all white crystals and their yields ranged from 68 to 71%. The structures of 1aeb were characterized by 1H and 13C NMR spectroscopy, mass spectra, and elemental analysis. Colorless crystals of target compounds 1a and 1c were obtained by slowly evaporating acetone solutions of 1a and 1c at room temperature. Their crystal structures were determined by X-ray crystallography at room temperature revealing that compound 1a crystallizes in the monoclinic system with a space group of P21/c (Table 1). As shown in Fig. 1a and b, the asymmetric unit of compound 1a consists of one crystallographically independent molecule. In the crystal structure of compound 1a, the two diphenyl 1,3,4-oxadizole moieties are both nearly planar and form a dihedral angel of 74.9 (1) . Additionally, the molecule is composed of a Vshaped building unit separated by a silicon atom. The overall structure of compound 1a can be described, as a two-dimensional (2D) supramolecular network. Intermolecular CeH$N hydrogen bonding interactions link two molecules into a dimer with a C22 to N2 distance of 3.414(3)  A and corresponding angle of 145.8(2) . The dimers are further assembled into a 2D supramolecular network through CeH$p stacking interactions. In compound 1a, the distance from H16B to the center of C25 to C30 is 2.704(3)  A and the distance from H16c to the center of C1 to C6 is 3.053(3)  A. These distances indicate strong intermolecular CeH$p interactions. Similar to compound 1a, compound 1c also crystallizes in monoclinic system with space group of P21/c (Table 1). As

The UVevis absorption properties of compounds 1aec are described in Fig. 2, which shows the normalized UVevis absorption of compounds 1aec in CHCl3 solution. The absorption spectra of compounds 1aec in solutions of CHCl3 contain one broad absorption band. The peak in the region of 292e304 nm originates from the pep* absorption of the conjugated diphenyl 1,3,4-oxadizole moiety. The absorption spectra of compounds 1b and 1c that contain a substituted alkoxy group gave bathochromic shifts of 11 nm

2. Results and discussion

Table 1 Crystal data and structure refinement of complexes 1a and 1c Compd

1a

1c

Formula weight Temperature (K) l ( A) Crystal system Space group a ( A) b ( A) c ( A) a (deg) b (deg) g (deg) Volume ( A3) Z Dcalcd (g/cm3) Abs coeff. (mm
1) Rint F(000) GOF on F2 R [I>2s(I)]a Rw (all data)b (Residues)max(e/ A3) (Residues)min(e/ A3)

500.62 297(2) 0.71073 Triclinic P-1 9.128(4) 11.240(6) 13.412(9) 82.89(2) 75.95(2) 87.15(2) 1324.4(13) 2 1.255 0.123 0.034 524 0.977 0.046 0.146 0.300
0.208

700.93 297(2) 0.71073 Monoclinic P21/c 9.3852(19) 17.367(3) 25.626(7) 90 109.22(3) 90 3944.0(15) 4 1.180 0.105 0.054 1496 0.965 0.058 0.167 0.177
0.143

a b

R¼kFoj
jFck/jFoj. Rw¼[w(F2o
F2c )2/w (F2o)2]1/2.

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D. Li et al. / Tetrahedron 71 (2015) 2680e2685

Fig. 1. (a) View of the dimer connected by CeH$N hydrogen bonding of 1a; (b) View of the 2D network containing CeH$p interactions of compound 1a; (c) View of the dimer connected by CeH$O hydrogen bonding of 1c; (d) View of the 2D network containing CeH$N hydrogen bonding of compound 1c.

compared with that of compound 1a without a substituent. The long alkoxy chain decreases the energy of the pep* transition. The optical band gaps (Eopt g ) were calculated from the relevant absorption onsets and found to be 4.42 eV, 4.21 eV, and 4.21 eV15 (Table 2). Fig. 3 shows the PL spectra of compounds 1aec in CHCl3 solution and the film that was spin coated from CHCl3 solution. The emission spectrum of compound 1a in CHCl3 contains three emission bands between 305 and 495 nm as shown in Fig. 3a. The emission spectra of compounds 1bec in CHCl3 contain one broad emission band for each compound and they are nearly identical. Interestingly, the maximum emission of compounds 1b and 1c red-shifted to 365 nm compared with that of 1a because of the alkyl chain substituent. The fluorescence quantum yields (QY) of 1ae1c measured at room temperature in dilute CHCl3 are moderate compared with the PL intensity of a standard solution of quinine sulfate (QY¼0.54). They range from 0.68 to 0.81 (Table 2). However, the emission spectra are

1a 1b 1c

Absorbance(Normalized)

1.0

quite different between the solution and film samples with regard to the two main emission peaks shown in Fig. 3b. According to this figure, the wavelength of emission for compounds 1b and 1c was red-shifted as the length of the alkyl chain increased. The intensity of one of the emission peaks increased while the other decreased. This phenomenon may come from the dihedral angle of the molecules increasing because of the length of the alkyl chain substituent. The molecules tend to be flat in the solid state. The electrochemical properties of 1aec in DMF were investigated by cyclic voltammetry (CV). All three V-shaped luminescent compounds exhibited similar electrochemical behavior and their CV curves had a similar pattern (Fig. 4 and Table 2). Fig. 4 shows representative CV traces for the oxidation and reduction of 1a and 1c. CV analyses reveal that 1ae1c undergo a single process of irreversible reduction at the cathodic potential associated with the reduction of the electron-deficient oxadizole moiety to form an anion radical. 1ae1c exhibit two irreversible oxidation processes. In all cases, the first oxidation peak corresponds to the removal of electrons from the peripheral phenyl group resulting in radical cations.

0.8

2.3. Computational methodology

0.6

All calculations were carried out using the Gaussian 09 (G09) package.17 Calculations on the electronic ground state of complexes 1aec were carried out using density functional theory (DFT)18 with

0.4 Table 2 Photophysical, physical, and electrochemical data

0.2

Compd

0.0 260

280

300

320

340

Wavelength(nm)

360

1a 1b 1c a b

Fig. 2. UVevis absorption spectra of compounds 1aec in CHCl3 solution.

c

a

Amax, (nm) 292.5 304.1 304.4

Abs

a

lmax, em

FF

b

Ered/peak/V

Eox/peak /V 1

Eox/peak /V 2

c

0.68 0.78 0.81


1.71
1.91
1.90

0.76 0.91 0.90

1.29 1.41 1.39

4.42 4.21 4.21

Eopt g

(nm) 340.2 363.3 364.1

Measured in CHCl3. Measured in CHCl3 with quinine sulfate as the standard (QY¼0.54).16 Calculated using Eg¼1240/labsonset.

D. Li et al. / Tetrahedron 71 (2015) 2680e2685

PL Intensity(Normalized)

1.0

2683

(a) 1a 1b 1c

0.8

0.6

0.4

0.2

0.0 300

350

400

450

500

Wavelength(nm)

PL Intensity(Normalized)

1.0

(b) 1a 1b 1c

0.8

0.6

0.4

0.2

0.0 350

400

450

500

Fig. 4. Cyclic voltammetry showing the oxidation (A) and reduction (B) of 1a and 1c.

Wavelength(nm) Fig. 3. Normalized PL spectra of compounds 1aec in (a) CHCl3 and (b) as films.

Becke’s LYP (B3LYP) exchange-correlation functional19,20 together with the 6-31G basis set.21 GaussView 5.0.8 was used for the interface of the structures and for orbital manipulations. To gain insight into the photophysical behavior of all of the studied complexes, density functional theory (DFT) was used for molecular orbital studies. To understand the charge carrier injection barriers, we investigated the changes that took place upon frontier orbital substitution. The HOMO and LUMO orbitals that are mostly involved in the lowest-lying transitions are shown in Fig. 5. These results, especially the calculated energy gaps, agree satisfactorily with the experimental photophysical data suggesting that the DFT calculations can to a certain degree predict the photophysical behavior of these complexes. As shown in Fig. 5, alkyl substitution destabilized both the HOMO and LUMO energy levels of the 1,3,4-oxadiazole molecule because of its electron donating ability. The HOMO energy increased by about 0.4 eV while the LUMO energy level increased by about 0.2 eV. The calculated vertical IP (IPv), adiabatic IP (IPa), vertical EA (EAv), and adiabatic EA (EAa) are listed in Table 3. To the best of our knowledge the reorganization energy (l) can be used to estimate the charge transport rate and the balance between holes and electrons. These results are listed in Table 2. The reorganization energy for electron transport is le¼EEP
EAv. EEP represents the electron extraction potential, which is the energy difference between M and MM
(anionic) when considering M


geometry. We found that complex 1a had the worst electron transfer ability and the lowest le value. The nearly identical le values of 1b and 1c indicated that they may have comparable electron transfer abilities. Thus, 1b and 1c should be good electron transport materials.22

2.4. Thermal properties The thermal stability of a material is important for device longevity. Fig. 6 shows a thermogravimetry analysis (TGA) of compounds 1aec. The TGA analysis revealed relatively high thermal stability with an initial weight loss (5%) temperature of 361  C that extended to 403  C. The thermal stabilities of the compounds progressively improved because of the substituent alkoxy chain. An increase in chain length affected their thermal stability (compounds 1b or 1c) as shown in Fig. 6.

3. Conclusions We developed a facile and effective method for the synthesis of novel, V-shaped organic fluorescent compounds. These materials do not aggregate in the condensed state as shown by their spectral similarities in the solution and film state. These novel emitters are solution processable and exhibit good film-forming ability, high thermal stability, and a good electron transport ability.

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D. Li et al. / Tetrahedron 71 (2015) 2680e2685

-1

-1.78

Energy/eV

-2

-3 -5

-1.55

-1.55

4.16

4.16

-5.71

-5.70

4.37

-6.15

-6

-7

1a

1b

1c

Fig. 5. Contour plots of the HOMO and LUMO for complexes 1aec.

Table 3 Ionization potentials, electron affinities, electron extraction potential, and the reorganization energy for electron transport in the complexes Comp.

IP(v)

IP(a)

EA(v)

EA(a)

EEP

le

1a 1b 1c

7.211 6.693 6.684

7.068 6.566 6.558

0.718 0.515 0.515

0.844 0.656 0.656

0.958 0.783 0.785

0.240 0.268 0.269

4. Experimental NMR spectra were recorded in CDCl3 with a Bruker AV-400 Spectrometer and chemical shifts were referenced relative to

120

Weight(%)

1a 1b 1c

60

40

20

0 100

200

300 o

Temperature( C) Fig. 6. TGA thermogram of compounds 1aec.

4.1. General procedure Starting compounds 2e5 were synthesized according to literature method.23,24 A stirred solution of hydrazide compounds (13.5 g, 58.0 mmol) in SOCl2 (200 mL) was refluxed at 80  C for 5 h under nitrogen. After excess SOCl2 was distilled off, the residue was slowly poured into 500 mL of H2O to give precipitation. After filtration, the filtrate was dried in vacuo. The products were purified by column chromatography on silica gel (n-hexane: EA¼3:1; v/v) to give a white solid. The solid was recrystallized from acetone obtained 1aec. 4.1.1. Dimethylbis[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]silane (1a). White solid (Yield: 69%). 1H NMR (400 MHz, CDCl3): d: 0.67 (s, 6H), 7.54e7.56 (m, 6H), 7.69 (d, J¼8.4 Hz, 4H), 8.13e8.16 (m, 8H); 13 C NMR (100 MHz, CDCl3): d: 164.75, 164.62, 142.37, 134.83, 131.81, 129.15, 127.04, 126.22, 124.78, 124.04,
2.62; LC-MS (ESI): C30H24N4O2Si calcd for [M]þ 500.2, found 500.1; FTIR (KBr, cm
1): 2958, 1608,1551, 1446, 1445, 1441, 1401, 1276, 1252, 1120, 1069, 1019, 965, 829, 818; Anal. Calcd for C30H24N4O2Si: C, 71.97; H, 4.83; N, 11.19. Found: C, 72.11; H, 4.89; N, 11.29.

100

80

tetramethylsilane (dH/dC¼0). Mass spectra was performed on Agilent 1100 LC/MSD Trap SL. IR spectra were recorded on a Perkin Elmer 2400 instrument (KBr pressed disc method).

400

4.1.2. Bis{4-[5-(4-butoxyphenyl)-1,3,4-oxadiazol-2-yl]phenyl}dimethylsilane (1b). White solid (Yield: 68%). 1H NMR (400 MHz, CDCl3): d: 0.66 (s, 6H), 1.00 (t, J¼7.2 Hz, 6H), 1.49e1.58 (m, 4H), 1.78e1.85 (m, 4H), 4.05 (t, J¼6.8 Hz, 4H), 7.02 (d, J¼8.8 Hz, 4H), 7.68 (d, J¼8.0 Hz, 4H), 8.06 (d, J¼8.8 Hz, 4H), 8.11 (d, J¼8.0 Hz, 4H); 13C NMR (100 MHz, CDCl3): d: 164.74, 164.09, 162.09, 142.07, 134.77, 128.75, 126.06, 124.89, 116.19, 115.06, 68.03, 31.21, 19.25, 13.85,
2.63; LCMS (ESI): C38H10N4O4Si calcd for [MþH]þ 645.3, found 645.2; FTIR (KBr, cm
1): 2958, 1613, 1496, 1258, 1068, 840, 814; Anal. Calcd

D. Li et al. / Tetrahedron 71 (2015) 2680e2685

for C38H40N4O4Si: C, 70.78; H, 6.25; N, 8.69. Found: C, 70.91; H, 6.39; N, 8.59. 4.1.3. Bis(4-{5-[4-(hexyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl)dimethylsilane (1c). White solid (Yield: 71%). 1H NMR (400 MHz, CDCl3): d: 0.66 (s, 6H), 0.92 (t, J¼7.2 Hz, 6H), 1.31e1.41 (m, 8H), 1.43e1.55 (m, 4H), 1.77e1.86 (m, 4H), 4.04 (t, J¼6.8 Hz, 4H), 7.02 (d, J¼8.0 Hz, 4H), 7.68 (d, J¼8.0 Hz, 4H), 8.06 (d, J¼8.0 Hz, 4H), 8.11 (d, J¼8.0 Hz, 4H); 13C NMR (100 MHz, CDCl3): d: 164.76, 164.10, 162.10, 142.07, 134.77, 128.75, 126.06, 124.88, 116.19, 115.06, 68.37, 31.60, 29.15, 25.72, 22.63, 14.06,
2.62; LC-MS (ESI): C42H48N4O4Si calcd for [MþH]þ 701.3, found 701.2; m/z (%) (Mþ, 100); FTIR (KBr, cm
1): 2960, 1612, 1496, 1258, 1068, 836, 813; Anal. Calcd for C42H48N4O4Si: C, 71.97; H, 6.90; N, 7.99. Found: C, 72.08; H, 6.98; N, 6.79.

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Acknowledgements This work was supported by the National Science Foundation of China (No. 21442004), the National Natural Science Foundation of Jilin Province (grant No. 20101548). Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.tet.2015.03.039. References and notes 1. Tang, C. W.; Vanslyke, S. A. Appl. Phys. Lett. 1987, 51, 913. 2. Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel-Razzaq, F.; Lee, H. E.; Adachi, C.; Buttows, P. E.; Forrest, S. R.; Thompson, M. E. J. Am. Chem. Soc. 2001, 123, 4304. 3. Yang, Y.; Zhao, Q.; Feng, W.; Li, F. Chem. Rev. 2013, 113, 192. 4. Li, H.; Wen, Z.; Jin, L.; Kan, Y.; Yin, B. Chem. Commun. 2012, 11659.

18. 19. 20. 21. 22. 23. 24.

2685

Feng, X.; Tian, P.; Xu, Z.; Chen, S.; Wong, M. J. Org. Chem. 2013, 78, 11318. Birks, J. B. Photophysics of Aromatic Molecules; Wiley: London, UK, 1970. Liu, J.; Lam, J. W. Y.; Tang, B. Chem. Rev. 2009, 109, 5799. Liu, X.; Xu, J.; Lu, X.; He, C. Org. Lett. 2005, 7, 2829. Wang, J.; Mei, J.; Yuan, W.; Lu, P.; Qin, A.; Sun, J.; Ma, Y.; Tang, B. J. Mater. Chem. 2011, 21, 4056. Chen, B.; Nie, H.; Lu, P.; Zhou, J.; Qin, A.; Qiu, H.; Zhao, Z.; Tang, B. Chem. Commun. 2014, 4500. Shi, C.; Guo, Z.; Yan, Y.; Zhu, S.; Xie, Y.; Zhao, Y.; Zhu, W.; Tian, H. ACS Appl. Mater. Interfaces 2013, 5, 192. Shao, A.; Guo, Z.; Zhu, S.; Zhu, S.; Shi, P.; Tian, H.; Zhu, W. Chem. Sci. 2014, 5, 1383. Gu, P.; Zhang, Y.; Liu, G.; Ge, J.; Xu, Q.; Zhang, Q.; Lu, J. Chem.dAsian. J. 2013, 8, 2161. Tang, X.; Yao, L.; Liu, H.; Shen, F.; Zhang, S.; Zhang, H.; Lu, P.; Ma, Y. Chem.dEur. J. 2014, 20, 7589. Kochapradist, P.; Sunonnamb, T.; Prachumrak, N.; Namuangruk S.; Keawin, T.; Jungsuttiwong, S.; Sudyoadsuk, T. Promarak V. 2014, 55, 6689. Kartens, T.; Kobs, K. J. Phys. Chem. 1980, 84, 1871. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. GAUSSIAN 09 (Revision B.01); Gaussian: Wallingford, CT, 2010. Hohenberg, P.; Kohn, W. Physiol. Rev. 1964, 136, 864. Lee, C.; Yang, W. T.; Parr, R. G. Phys. Rev. [Sect.] B 1988, 37, 785. Becke, A. D. J. Chem. Phys. 1993, 98, 5648. Hariharan, C.; Pople, J. A. Mol. Phys. 1974, 27, 209. Lin, B. C.; Cheng, C. P.; You, Z. Q.; Hsu, C. P. J. Am. Chem. Soc. 2005, 127, 66. Tang, H. Y.; Song, N. H.; Gao, Z. H.; Chen, X. F.; Fan, X. H.; Xiang, Q.; Zhou, Q. F. Polymer 2007, 48, 129. Ren, X. J.; Wang, L.; Gao, L.; Xie, Z. Y.; Li, D. F. Chin. J. Org. Chem. 2009, 29, 1147.