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Optical properties of C60-derived star-burst oligoanilines
ELSEVIER
Synthetic
Optical
properties
Metals
101 (1999)
791-792
of ChO-derived star-burst
oligoanilines
Vijayaraj Anantharaj, Edna Ho, Lee Y. Wang, and Long Y. Chiang* Cerzter for Cortderzsed Matter Sciences, Taiwan Univemly, Taipei, Taiwan
Abstract A fluorescence peak, centered at 415-418 nm, of hexa(tetranilino)fullerenes and hexa(hexadecaanilino)fullerenes was attributed to the energy relaxation of oligoaniline arms upon photo-excitation, The second fluorescence peak at 350 nm, contributed from the excited C& moiety, was detected in a much lower intensity. Keywords; hexa(dianilino)fullerenes,
hexa(tetranilino)fullerenes,
Aniline oligomers and polymers exhibit several reversible oxidation and reduction states which are rich in optical absorption, showing sharp changes of color upon treatment with stoichiometric redox reagents [1,2]. By incorporation of a C60 cage as a molecular core in linking multiple aniline oligomers together to form the corresponding star-burst semirigid polymers, the intramolecular coupling of the zelectrons between conjugated oligoaniline arms may be enhanced via the terminal Ccc moiety. Applications of the fullerenic redox chemistry involving multiple electrons in conjunction with that of oligoanilines may also allow one to investigate the intramolecular photoactivated electron-transfer phenomena between oligoaniline donors and the C60 acceptor. Thus optical absorption properties of these novel Ceo-derived starburst oligoanilines become crucial in determining efficiency of the photo-activation processes. Synthesis of star-burst &-based oligoanilines was carried out by nucleophilic hexa-substitution reaction of hexanitro[60]fullerenes [3] with either aniline, dianiline, tetraniline or hexadecaaniline [4], leading to products of hexanilino[60]fullerenes 1, hexa(dianilino)[60]fullerenes 2, hexa(tetranilino)[60]fullerenes 3, or hexa(hexadecaanilino)[60]fullerenes 4, respectively. 0379-6779/99/$ - see front matter 0 1999 Elsevier PII: SO379-6779(98)00793-O
hexa(hexadecaanilino)fullerenes
In cases of star oligoanilines 3 and 4, an emeraldine base form of the compound was used in this study.
7 (n =O)and
2(n = 1)
3(n=l)and4(n=4) 1I
I
400
500
Wavenumber
600
700
600
inm)
Figure 1. UV-Vis spectra of (a) polyaniline, hexadecaaniline, (c) 4, (d) 3, (e) 2, and (I) 1.
(b)
The maximum optical absorption of anilinated fullerene cages occurs at 250-273 nm with a shoulder
Science S.A. AI1 rights reserved.
L.Y. Chiang
792
band centered at 340 nm. As the oligoaniline arms increases from shift of the absorption band to was detected at 556 and 575 nm respectively. The latter is 13 nm
et al. I Synthetic
conjugation length of 1 to 16 aniline units, a longer wavelength for 3 and 4 (Fig. l), longer in wavelength
----uv0f1x104En -----~.WL=250nm _._.-.- EC ‘NL=30Q _.._.1-_. 2. ‘NL=3SO .. . .._..- &. ‘JvL~ll ----Ex. ‘fvL450 . . . . i5.x. WL=jGO sx. WL=55U
I
! ml
2m
m
m Wavelength
300
ml
M Wavelength
SW
nm nm nm nm nm
7w
ecu
(nm)
-UVoflX1&6M ----63. wL=250 -.-.-.- a. \flL=ZlJO _..-..-.. & INt=SW .-Ex. WLAOO Ex. WL=-%O ._...... a. Ifi=Em Ex. WL=550
Figure 2. Fluorescence (b) 3, and (c) 4.
dW
7w
-uvofiXlO-SM -----~.WL=25O”m -._.-.- 3. WL=3DO _. - .._. Er. WL=350 . . .. .. .. . E.7. WL=400 --Ex. wL=450 ._...... e. y&=juO
@I
2w
3x (nm)
nm nm nm ilm nm “i-n
nm “m “m nm nm nm nm
and UV spectra of (a) 1,
than that of hexadecaaniline (562 nm) and 25 nm shorter in wavelength than that of polyaniline. These
Met&
IO1 (I999)
791-732
optical data are indicative of a rather small difference in optical absorption in the visible region between 4 and high molecular weighted polyanilines. We found that all compounds l-4 exhibit appreciable fluorescence characteristics upon photoexcitation. In the case of compound 1 (Fig. 2a), a major UV band centered at 255 nm arises from absorption of the C6o moiety. Thus, the fluorescence peaks of 1 centered at 349 and 362 nm can be attributed to the energy relaxation of photo-excited C&o cages at 250 and 300 nm, respectively. With-the application of irradiation at a longer wavelength than 300 nm, only a fluorescence band at 425 nm in a low intensity was observed.~__~-As - the _.number of aniline units in each arms increases to 4 and 16, optical absorption of the oligoaniline moiety, in its emeraldine base form, at 300-320 nm dominates- the UV spectrum of 3 (Fig. 2b) and 4 (Fig. 2~). Consequently, the observed fluorescence peaks centered at 415 (Fig. 2b) and 418 nm (Fig. 2c) were derived from the photo-excitation of oligoanilines under irradiation at either 250, 300, or 350 nm. These fluorescence maxima are in the same range as that (420 nm) of the emeraldine base reported [5]. The corresponding fluorescence z peak contributed from relaxation of the excited ChD moiety of 3 and 4 was detected at 350 nm in a much lower intensity. Acknowledgment. NSC of Republic
This work was supported by the of China (NSC 87-22 16E002-02 1).
References and A.G. [ll W.S. Huang, B.D. Humphrey MacDiarmid, J. Chem. Sot., -Faraday Trans. I 82 (1986) 2385. PI A.M. Kenwright, W.J. Feast, P. Adams, A.J. Milton, A.P. Monkman and B.J. Say, PolJ’mer 33 ( 1992) 4292. t31 L.Y. Chiang, J.B. Bhonsle, L.Y. Wang, S.F. Shu, T.M. Chang and J.R. Hwu, Tetraheciron 52 (1996) 4963. 141 W.J. Zhang, J. Feng, A.G. MacDiarmid and A.J. Epstein, S’nth. hlet. 83 (1997) 119. J.R.G. Thorne, J.G. Masters, S.A. Williams, A.G. IIs1 MacDiarmid, Sy&. Met. 49 (1992) 159.
Synthetic
Optical
properties
Metals
101 (1999)
791-792
of ChO-derived star-burst
oligoanilines
Vijayaraj Anantharaj, Edna Ho, Lee Y. Wang, and Long Y. Chiang* Cerzter for Cortderzsed Matter Sciences, Taiwan Univemly, Taipei, Taiwan
Abstract A fluorescence peak, centered at 415-418 nm, of hexa(tetranilino)fullerenes and hexa(hexadecaanilino)fullerenes was attributed to the energy relaxation of oligoaniline arms upon photo-excitation, The second fluorescence peak at 350 nm, contributed from the excited C& moiety, was detected in a much lower intensity. Keywords; hexa(dianilino)fullerenes,
hexa(tetranilino)fullerenes,
Aniline oligomers and polymers exhibit several reversible oxidation and reduction states which are rich in optical absorption, showing sharp changes of color upon treatment with stoichiometric redox reagents [1,2]. By incorporation of a C60 cage as a molecular core in linking multiple aniline oligomers together to form the corresponding star-burst semirigid polymers, the intramolecular coupling of the zelectrons between conjugated oligoaniline arms may be enhanced via the terminal Ccc moiety. Applications of the fullerenic redox chemistry involving multiple electrons in conjunction with that of oligoanilines may also allow one to investigate the intramolecular photoactivated electron-transfer phenomena between oligoaniline donors and the C60 acceptor. Thus optical absorption properties of these novel Ceo-derived starburst oligoanilines become crucial in determining efficiency of the photo-activation processes. Synthesis of star-burst &-based oligoanilines was carried out by nucleophilic hexa-substitution reaction of hexanitro[60]fullerenes [3] with either aniline, dianiline, tetraniline or hexadecaaniline [4], leading to products of hexanilino[60]fullerenes 1, hexa(dianilino)[60]fullerenes 2, hexa(tetranilino)[60]fullerenes 3, or hexa(hexadecaanilino)[60]fullerenes 4, respectively. 0379-6779/99/$ - see front matter 0 1999 Elsevier PII: SO379-6779(98)00793-O
hexa(hexadecaanilino)fullerenes
In cases of star oligoanilines 3 and 4, an emeraldine base form of the compound was used in this study.
7 (n =O)and
2(n = 1)
3(n=l)and4(n=4) 1I
I
400
500
Wavenumber
600
700
600
inm)
Figure 1. UV-Vis spectra of (a) polyaniline, hexadecaaniline, (c) 4, (d) 3, (e) 2, and (I) 1.
(b)
The maximum optical absorption of anilinated fullerene cages occurs at 250-273 nm with a shoulder
Science S.A. AI1 rights reserved.
L.Y. Chiang
792
band centered at 340 nm. As the oligoaniline arms increases from shift of the absorption band to was detected at 556 and 575 nm respectively. The latter is 13 nm
et al. I Synthetic
conjugation length of 1 to 16 aniline units, a longer wavelength for 3 and 4 (Fig. l), longer in wavelength
----uv0f1x104En -----~.WL=250nm _._.-.- EC ‘NL=30Q _.._.1-_. 2. ‘NL=3SO .. . .._..- &. ‘JvL~ll ----Ex. ‘fvL450 . . . . i5.x. WL=jGO sx. WL=55U
I
! ml
2m
m
m Wavelength
300
ml
M Wavelength
SW
nm nm nm nm nm
7w
ecu
(nm)
-UVoflX1&6M ----63. wL=250 -.-.-.- a. \flL=ZlJO _..-..-.. & INt=SW .-Ex. WLAOO Ex. WL=-%O ._...... a. Ifi=Em Ex. WL=550
Figure 2. Fluorescence (b) 3, and (c) 4.
dW
7w
-uvofiXlO-SM -----~.WL=25O”m -._.-.- 3. WL=3DO _. - .._. Er. WL=350 . . .. .. .. . E.7. WL=400 --Ex. wL=450 ._...... e. y&=juO
@I
2w
3x (nm)
nm nm nm ilm nm “i-n
nm “m “m nm nm nm nm
and UV spectra of (a) 1,
than that of hexadecaaniline (562 nm) and 25 nm shorter in wavelength than that of polyaniline. These
Met&
IO1 (I999)
791-732
optical data are indicative of a rather small difference in optical absorption in the visible region between 4 and high molecular weighted polyanilines. We found that all compounds l-4 exhibit appreciable fluorescence characteristics upon photoexcitation. In the case of compound 1 (Fig. 2a), a major UV band centered at 255 nm arises from absorption of the C6o moiety. Thus, the fluorescence peaks of 1 centered at 349 and 362 nm can be attributed to the energy relaxation of photo-excited C&o cages at 250 and 300 nm, respectively. With-the application of irradiation at a longer wavelength than 300 nm, only a fluorescence band at 425 nm in a low intensity was observed.~__~-As - the _.number of aniline units in each arms increases to 4 and 16, optical absorption of the oligoaniline moiety, in its emeraldine base form, at 300-320 nm dominates- the UV spectrum of 3 (Fig. 2b) and 4 (Fig. 2~). Consequently, the observed fluorescence peaks centered at 415 (Fig. 2b) and 418 nm (Fig. 2c) were derived from the photo-excitation of oligoanilines under irradiation at either 250, 300, or 350 nm. These fluorescence maxima are in the same range as that (420 nm) of the emeraldine base reported [5]. The corresponding fluorescence z peak contributed from relaxation of the excited ChD moiety of 3 and 4 was detected at 350 nm in a much lower intensity. Acknowledgment. NSC of Republic
This work was supported by the of China (NSC 87-22 16E002-02 1).
References and A.G. [ll W.S. Huang, B.D. Humphrey MacDiarmid, J. Chem. Sot., -Faraday Trans. I 82 (1986) 2385. PI A.M. Kenwright, W.J. Feast, P. Adams, A.J. Milton, A.P. Monkman and B.J. Say, PolJ’mer 33 ( 1992) 4292. t31 L.Y. Chiang, J.B. Bhonsle, L.Y. Wang, S.F. Shu, T.M. Chang and J.R. Hwu, Tetraheciron 52 (1996) 4963. 141 W.J. Zhang, J. Feng, A.G. MacDiarmid and A.J. Epstein, S’nth. hlet. 83 (1997) 119. J.R.G. Thorne, J.G. Masters, S.A. Williams, A.G. IIs1 MacDiarmid, Sy&. Met. 49 (1992) 159.