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Порфирины Porphyrins
Макрогэтэроцмклы
http://macroheterocycles.isuct.ru
Статья Paper
DOI: 10.6060/mhc2012.121198z
Synthesis of Novel Fullerene-Porphyrin Conjugates for the Formation of Langmuir Monolayers
Ekaterina S. Zyablikova,a Natal'ya A. Bragina,a Andrey F. Mironov,a Daria A. Silant'eva,b and Sofia L. Selektorb
Dedicated to Academician Aslan Tsivadze on the occasion of his 70th Anniversary
aDepartment of Chemistry and Technology of Biologically Active Compounds, Lomonosov Moscow State University of Fine Chemical Technologies, 119571 Moscow, Russian Federation. E-mail: e.s.krutikova@gmail.com
hFrumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 119071 Moscow, Russian Federation E-mail: sofs@list.ru
The conjugates of C60fullerene and lipophilic meso-aryl substituted porphyrins with terminal long chains are prepared and used to form Langmuir monolayers at the air/water interface.
Keywords: Fullerenes, meso-aryl substituted porphyrins, fullerene-porphyrin conjugates, Langmuir monolayers.
Синтез новых фуллерен-порфириновых конъюгатов для формирования монослоев Ленгмюра
Е. С. Зябликова,а Н. А. Брагина,а А. Ф. Миронов,a Д. А. Силантьева,b С. Л. Селекторь
Посвящается академику А. Ю. Цивадзе по случаю его 70-летнего юбилея
Московский государственный университет тонких химических технологий имени М.В. Ломоносова, 119571 Москва, Россия E-mail: e.s.krutikova@gmail.com
ьИнститут физической химии и электрохимии имени А. Н. Фрумкина РАН, 119071 Москва, Россия E-mail: sofs@list.ru
Осуществлен синтез конъюгатов на основе фуллерена С60 и липофильных мезо-арилпорфиринов с длинноцеп-ными заместителями для получения на их основе монослоев Ленгмюра.
Ключевые слова: Фуллерены, мезо-арилзамещенные порфирины, фуллерен-порфирин конъюгаты, монослои Ленгмюра.
Introduction
In recent years there has been much research activity focused on the fUllerene-porphyrin conjugates known for unique electronic properties that allow using these assemblies in various optoelectronic and photoelectrical devices for diverse applications and particularly in photovoltaics, solar
batteries, in the construction of photosynthetic models.[1-5] The structures in which the conjugated porphyrin absorbs light in the UV-vis spectral range and acts as an electron donor while the fullerene having weak light absorption acts as an electron acceptor are of special importance.[6-7] Irradiation of such dyads yields a radical ion pair, the charge-separated state lifetime of which exceeds one of the known donor-acceptor systems by
Novel Fullerene-Porphyrin Conjugates for Langmuir Monolayers
several orders of magnitude.18-121 The energy of the charge-separated state can be converted into chemical or electrical energy through vectorial electron transfer. To accomplish this the donor-acceptor molecules must be assembled into a molecular monolayer with a unidirectional orientation. Desired arrangement of porphyrin-fullerene donor-acceptor dyads can be realized in the Langmuir monolayer.113-171
Since the formation of high ordered Langmuir monolayers at air/water interface are favored by using porphyrins substituted by long hydrophobic side chains, we have synthesized conjugates based on C60 fullerene and lypophilic meso-arylsubstituted porphyrins with long chain alkyl groups of 6, 14, and 18 carbon atoms (Figure 1).
Figure 1. Structure of fullerene-porphyrin conjugates.
Results and Discussion
Among the main approaches for preparation of porphyrin conjugates with C60 (namely, the [3+2] Bingel-Hirsch cyclopropanation of C60 fullerene and the [4+2] Diels-Alder cycloaddition), the [3+2] cyclopropanation is considered as the most effective synthetic route to covalently linked conjugates.[18-24]
Thus to derive the fullerene-porphyrin conjugates with long chain alkyl substituents we employed the Prato reaction that is 1,3-dipolar cycloaddition to the double bond in a 6,6 ring position in a fullerene of azomethine ylide generated by the condensation of an a-amino acid and an aldehyde.[25-26]
The reaction offers the following advantages:
• The condensation yields single 6,6-closed isomers;
• Various a-amino acids and aldehydes can be easily obtained from commercially available precursors;
• The intermediate ylides may be synthesized starting with diverse aldehydes to afford a variety of functionalized fulleropyrrolidinoporphyrins.
In this work, we used mono-p-formyltetraphenylporphyrins with the long chain alkyl groups at the /»-position of meso-phenyl moieties.
C60 was bound to formylporphyrins 1a,b,c by condensation with ^-methylglycine in dry toluene under argon, reaction time was 20 h, TLC control (hexane:toluene) (Scheme 1). The reaction mixture was cooled and the solvent was removed in vacuo. The produced conjugates 3a,b,c were isolated by column chromatography on silica gel (hexane:toluene = 3:1, hexane:chloroform = 3:1) in 2527 % yield. Long alkyl chains attached onto the periphery of the porphyrin core provide good solubility of fullerene-porphyrin conjugates in methylene chloride, which makes further handling of the synthesized products much easier.
The synthesized dyads were characterized by IR, UV-vis, 13C NMR, 1H NMR spectroscopy, and mass-spectrometry The absorption spectra of 3a,b,c show the hypsochromic shift of the Soret band towards 429 nm. Proton resonances shifted 5.46 ppm (1H, s, NCH), 4.68 (1H, d, NCH2), 3.83 ppm (1H, d, NCH2) and 2.54 ppm (3H, s, NCH3) in the 1H NMR spectrum of 3a indicate the formation of pyrrolidine ring. The signals at 158.45-110.88 ppm observed in 13C NMR spectrum of 1a are from the fullerene fragment of the dyad, and those at 66.92, 67.09, 67.36, 68.89, 38.38 ppm belong to pyrrolidine ring. The MALDI peak at m/z 1792.33 in the mass spectrum of 3a corresponds to the molecular ion of the dyad.
The nickel complexes of fullerene-porphyrin conjugates were prepared starting from formylporphyrins 2a,b,c analogously to conjugates 3a,b,c. In this case the yield was somewhat lower but it was found to increase with alkyl chain length.
The Soret band in the absorption spectra is shifted towards 426-427 nm. The 1H NMR spectrum of 4a contains signals from pyrrolidine ring shifted 5.46 ppm (1H, s, NCH), 4.71 (1H, d, NCH2), 3.86 ppm (1H, d, NCH2), and 2.57 ppm (3H, s, NCH3). 13C NMR spectrum of 4a shows signals from fullerene sp2 C atoms at 159.80-113.12 ppm and from pyrrolidine sp3 C atoms at 66.89, 67.01, 67.37, 38.5 ppm.
The synthesized fullerene-porphyrin conjugates were used to derive the corresponding zinc complexes 5a,b,c (Scheme 2). Treatment of 3a,b,c with zinc acetate in chloroform/methanol mixture afforded zinc complexes of the dyads, the formation of which was confirmed
ROf ,M
-N N
OR
1a,b,c M=2H 2a,b,c M=Ni
RO/ M\ .M. /i/OR
R=-(CH2)nCH3 n=5(a), 13(b), 17(c)
OR
3a,b,c M=2H 4a,b,c M=Ni
Scheme 1. Synthesis of fullerene-porphyrin conjugates.
Scheme 2. Synthesis of zinc complexes of porphyrin-fullerene conjugates.
spectrophotometrically. The electronic absorption spectra of metalated 5a,b,c feature the prominent Soret band at 430 nm and one Q band at 555 nm indicative of insertion of the metal into the porphyrin ring. The obtained metalloporphyrins were dissolved in chloroform and precipitated by addition of heptane. Zinc complexes were isolated in 92-95 % yield.
Considering the produced dyads 3a,b,c and their nickel complexes 4a,b,c and zinc complexes 5a,b,c, we examined the possibility of forming Langmuir monolayers on the aqueous subphase. It was found that the dyads 3a,b,c and their nickel complexes 4a,b,c and zinc complexes 5a,b,c are able to form stable monolayers at air/water interface.
Formation of Langmuir monolayers as well as compression experiments were performed with the KSV (KSV Mini, Finland) system equipped with a moving barrier and a Wilhelmi plate (accuracy 0.05 mN/m). Water surface area between the barriers was 273.0 cm2 (length - 36.4 cm, width - 7.5 cm). The in situ absorption and fluorescence spectra for the monolayers on the water surface under compression were recorded with the AvaSpec-2048 fiber optic spectrometer (Netherlands).127-281 The subphase was deionized water. Chloroform of analytical grade (Merck) was used for solution preparation and as a spreading solvent. Exposition time for solvent evaporation was 15 min. Monolayers were compressed at the rates of 2 cm2/min.
A, A2/molecule
Surface pressure (surface pressure versus water area available per molecule) isotherms were measured to study the possibility of forming stable monolayers at the air/water interface. For fullerene-porphyrin dyad 3b (Figure 2a), the curve shows a classical shape with three distinct regions corresponding to the phase transition of the monolayer. Sequential compression of the monolayer changes the structure of monolayer films, which passes through a series of two-dimensional states, conventionally designated as the state of gas, liquid, and solid. When the available area is large, the monolayer can be regarded as a two-dimensional gas (region 1). If the surface area of the monolayer is reduced by a barrier system, as early as at the surface pressures of 2-3 mN/m the isotherm bends upward as the monolayer undergoes a transition to the liquid-expanded state (region 2). A less pronounced bend in the isotherm at 10-15 mN/m marks the transformation to a more ordered liquid-condensed state. Upon further compression to 5055 mN/m molecules form densely packed monolayer, that corresponds to the solid state film (region 3). A high degree of order in the monolayer is suggested by the high surface pressure and rather high area at which monolayer collapses. Good experimental reproducibility and the identical surface pressure isotherms obtained for the monolayers spread from the chloroform solutions of different volumes mean that
A, A2/molecule
Figure 2. Isotherms of monolayer compression at the air/water interface at T=27 °C: a) 3b (500 mkl, 5-10-6 M), b) 3a (625 mkl, 1-10-5 M), 3b (625 mkl, 110-5 M), and 3c (500 mkl, 110-5 M); n is the surface pressure, A is area per molecule.
Novel Fullerene-Porphyrin Conjugates for Langmuir Monolayers a)
I, a.u.
380 -330 -280 -230 -180 -130 -80 30 -20 +-
600
----5b
TPPOC14 3b
700
800
X, nm
I, a.u.
1200
600
-TPPOC14
3b
-4b
--5b
600 650 700 750 800
X, nm
Figure 3. a) Fluorescence spectra of solution of dyad 3b (1T0"6 M), 5b (1T0"6 M) and porphyrin TPPOC14 (CHCl3), b) fluorescence spectra of the monolayers of dyad 3b (5-10"6 M, 500 mkl), 4b (110-5 M, 500 mkl), 5b (l10-5 M, 500 mkl) and porphyrin TPPOC14 (110-5, 450 mkl M), (surface pressure 25 mN/m). Wavelength 430 nm.
0
lipophilic molecules spread uniformly on water without self-aggregation thus proving the system stability and, therefore, we managed to get a true Langmuir monolayers.
Comparing the surface pressure isotherms for the monolayers of 3а, 3b, and 3c bearing hydrocarbon chains of different lengths (Figure 2b), it expectedly turns out that the most stable monolayer is formed by dyad 3b with pendant tetradecyl groups due to the high pressure of the collapse, according to п-A -isotherm.
For dyad 3b and 5b solutions in CHCl3 fluorescence quenching was much stronger compared to parent 5,10,15,20-tetra(4-tetradecyloxyphenyl)porphyrin ТРРОС14 (Figure 3a). Concerning the Langmuir monolayers of dyads 3b, 4b and 5b the intensive reduction of fluorescence intensity compared to the monolayer of ТРРОС14 was also observed (Figure 3b).
The absorption spectrum of molecular monolayer is highly sensitive to the aggregation type of fullerene-porphyrin adducts. Hence the behavior of the monolayers under 2D compression on the water surface in situ was studied spectrometrically. The absorption spectra of fullerene-porphyrin conjugates 3b and Ni, Zn-complexes 4b, 5b solutions in CHCl3 are shown in Figure 4а. The
a)
D -,
0,2 -
0,15 -
0,1
0,05
400
450
500
A, A2/molecule
550
X, nm
absorption spectrum of the 3b, 4b and 5b monolayers is characterized by distinct Soret band at 440 nm (Figure 5a,b,c). The absorption spectra of 4b and 5b monolayers have a broad band with the maximum at 550-560 nm corresponding to one Q band. The Langmuir monolayer of dyad 3b, 4b and 5b exhibited a significant increase in the absorption intensity with the surface pressure within 2 to 25 mN/m range, which indicates the formation of a highly ordered monolayer on deionized water (Figure 5a,b,c). Bathochromic shift of the Soret band of the fullerene-porphyrin conjugates of 2-3 nm implies that no aggregation occurs in this case. The mean molecular area-surface pressure isotherms of the dyad 3b, 4b, and 5b monolayers on the water surface are presented in Figure 4b.
The similar results were obtained for dyads 3a,c and their nickel complexes 4a,c and zinc complexes 5a,c.
Thus, addition of terminal long chain hydrophobic alkyl groups to the porphyrin-fullerene molecules promotes the formation of highly ordered Langmuir monolayers at the air/water interface. These monolayers can be transferred onto solid substrates, which is essential for their further use in optoelectronics.
b)
X, nm
n, mN/m
50403020100
3b 4b 5b
200
400
600
800
A, A /molecule
Figure 4. a) The absorption spectra of dyad 3b (M0-6 M), 4b (110-6 M) and 5b (1-10-6 M): solutions in CHCl3. b) Isotherms of monolayer compression at the air/water interface at 27 °C: 3b (5-10"6 M, 500 mkl), 4b (110-5 M, 500 mkl), 5b (110-5 M, 500 mkl).
0
400 OmN/m
Figure 5. The absorption spectra of monolayer: a) 3b (110-5 M, 625 mkl); b) 4b (110-5 M, 500 mkl); c) 5b (2.5-10-5 M, 250 mkl). Arrows indicate the direction of the surface pressure gradient.
Conclusion
New fullerene-porphyrin conjugates bearing terminal hydrocarbon long chains were synthesized and metalated to yield zinc and nickel complexes. The prepared fullerene-porphyrin adducts form highly ordered Langmuir monolayers on the water subphase. The most stable Langmuir monolayers are produced by the conjugates with tetradecyl side chains attached to the porphyrin ring. It is necessary to note that such monolayers retain the optical and fluorescence characteristics of new compounds in chloroform solutions.
References
1. Langa F., Nierengarten J.-F. Fullerenes: Principles and Applications. Cambridge: The Royal Society of Chemistry, 2007. 398 p.
2. Rosen B.M., Wilson C.J., Wilson D.A., Peterca M., Imam M.R., Percec V. Chem. Rev. 2009, 109, 6275-6540.
3. Sidorov L.N., Yurovskaya N.A., Borschevskii A.Yu., Trushkov I.V., Ioffe I.N. Fullereny [Fullerenes]. Moscow: Publishers: "Ekzamen", 2005. 688 p. (in Russ.).
4. Rezayat S.M., Boushehri S.V.S., Salmanian B., Omidvari A.H., Tarighat S., Esmaeili S., Sarkar S., Amirshahi N., Alyautdin R.N., Orlova M.A., Trushkov I.V., Buchachenko A.L., Liu K.C., Kuznetsov D.A. Eur. J. Med. Chem. 2009, 44, 1554-1569.
5. Razumov V.F., Efimov O.N., Kaplunov M.T., Klyuev M.V., Klyueva M.E., Lomova T.N., Tarasov B.P., Troshin P.A., Yarmolenko O.B., Nanostrukturirovannye materialy dlya sistem zapasaniya i preobrazovaniya energii [Nanostructured Materials for Energy Storage and Processing Systems]. Ivanovo State University, 2007. 296 p. (in Russ.).
6. Kahnt A., Karnbratt J., Esdaile L. J., Hutin M., Sawada K., Anderson H. L., Albinsson B. J. Am. Chem. Soc. 2011, 133, 9863-9871.
7. Li W.-S., Aida T. Chem. Rev. 2009, 109, 6047-6076.
8. Guldi D.M. Fullerenes: From Synthesis to Optoelectronic Properties. Kluwer Academic Publishers: Dordrecht, The Netherlands, 2002. p. 163-212.
9. Guldi D.M., Rahman G.M.A., Sgobba V., Ehli C. Chem. Soc. Rev. 2006, 35, 471-487.
10. Molina-Ontoria A., Wielopolski M., Gebhardt J., Gouloumis A., Clark T., Guldi D. M., Mart N. J. Am. Chem. Soc. 2011 133, 2370-2373.
11. Choi M.-S., Aida T., Luo H., Araki Y., Ito O. Angew. Chem.Int. Ed. 2003, 42, 4060-4063.
12. Kuciauskas D., Liddell P.A., Lin S., Johnson T.E., Weghorn S.J., Lindsey J.S., Moore A.L., Moore T.A., Gust D. J. Am. Chem. Soc. 1999, 121, 8604-8614.
13. Vuorinen T., Kaunisto K., Tkachenko N.V. Langmuir 2005, 21, 5383-5390.
14. Vivo P.A., Alekseev A.S., Kaunisto K., Pekkola O., Tolkki A., Chukharev V., Efimov A., Ihalainen P. Phys. Chem. Chem. Phys. 2010, 12, 12525-12532.
15. Lewandowska K., Bogucki A., Wrobel D., Graja A. J. Photochem. Photobiol. A: Chem. 2007, 188, 12-18.
16. Vuorinen T., Kaunisto K., Tkachenko N.V., Efimov A., Lemmetyinen H. J. Photochem. Photobiol. A: Chem. 2006, 178, 185-191.
17. Alekseev A.S., Tkachenko N.V., Efimov A.V., Lemmetyinen H. Zh. Fiz. Khimii 2010, 84, 1356-1367 (in Russ.).
18. Nagata N., Kuramochi Y., Kobuke Y. J. Am. Chem. Soc. 2009, 131, 10-11.
19. Souza F.D., Gadde S., Zandler M. E., Klykov A., El-Khouly M.E. Fujitsuka M., Ito O. J. Phys. Chem. A. 2002, 106, 12393-12404.
20. Schuster D.I., Li K., Guldi D.M., Palkar A., Echegoyen L., Stanisky C., Cross R. J., Niemi M., Tkachenko N.V., Lemmetyinen H. J. Am. Chem. Soc. 2007, 129, 15973-15982.
21. Lembo A., Tagliatesta P., Guldi D.M., Wielopolski M., Nuccetelli M. J. Phys. Chem. A. 2009, 113, 1779-1793.
22. Fazio M.A., Lee O.P., Schuster D.I. Org Lett. 2008, 10, 4979-4982.
23. Higashida S., Imahori H., Kaneda T., Sakata Y. Chem. Lett. 1998, 7, 605-606.
24. Carbonera D.V., Valentin M.D., Corvaja C., Agostini G., Giacometti G., Liddell P.A, Kuciauskas D., Moore A.L., Moore T.A., Gust D. J. Am. Chem. Soc. 1998, 120, 4398-4405.
25. Maggini M., Scorrano G. J. Am. Chem. Soc. 1993, 115, 9798-9799.
26. Drovetskaya T., Reed C.A., Boyd P. Tetrahedron Lett. 1995, 36, 7971-7974.
27. Stuchebrukov S.D., Selektor S.L., Silantieva D.A., Shokurov A.V. Prot. Met. Phys. Chem. Surf. 2013, 49 (in press).
28. Selector S., Fedorova O., Lukovskaya E., Anisimov A., Fedorov
Y., Tarasova N., Raitman O., Fages F., Arslanov V. J. Phys. Chem. B. 2012, 116, 1482-1490.
Received 21.11.2012 Accepted 18.12.2012
Макрогетероциmbl /Macroheterocycles 2012 5(4-5) 333-337
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