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C60-pyridyl supramolecular system formation
Tetrahedron xxx (2015) 1e6
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Kinetics of Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system formation Ekaterina N. Ovchenkova *, Nataliya G. Bichan, Tatyana N. Lomova G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 April 2015 Received in revised form 6 July 2015 Accepted 20 July 2015 Available online xxx
The reaction of (octakis(4-tert-butyl-phenyl)tetraazaporphyrinato) manganese(III) acetate ((AcO) MnTAP(p-t-BuC6H4)8) with 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)-pyrrolidino[30 ,40 :1,2][60] fullerene (Py3F) in toluene was studied by methods of chemical kinetics and UV, visible, IR and 1H NMR spectroscopy. The interaction is found to result in the formation of 1:1 donor-acceptor complex whose structure was determined. A negative value of a complex formation order with respect to Py3F was established and explained. The kinetic equation can be used in the development of technology of metal tetraazaporphyrin-fullerene dyad production. Ó 2015 Published by Elsevier Ltd.
Keywords: Tetraazaporphyrin Manganese(III) complexes Pyridine substituted pyrrolidino[60] fullerene Donor-acceptor dyad
1. Introduction The ability of metal porphyrins/phthalocyanines (P/Pc) to form coordination assemblies due to axial metal-ligand interactions can successfully be used in the design of complexes with some fullerene derivatives. Supramolecular dyads of metal porphyrins/phthalocyanines with fullerenes show promising photophysical, ferromagnetic, superconducting and unusual optical properties.1e4 Porphyrins and phthalocyanines are aromatic macrocyclic compounds which present rich redox chemistry coupled to an absorption in the red/near infrared (IR) region of the solar spectrum with high extinction coefficients and fluorescence quantum yields. The unique physicochemical features of these compounds make them ideal molecular components for the preparation of photoactive, donoreacceptor (DeA) ensembles. In such systems, the Pcs’ role is twofold: first, they function as antennas due to their excellent optical absorption in the visible region of the emission solar spectrum; and second, once photo-excited, they act as electron donors. Among the acceptor moieties that have been chosen as molecular partners for porphyrins/phthalocyanines, fullerene and their derivatives have a privileged position. This spherical carbon nanostructure in fact possesses an extraordinary electron acceptor property,1,5,6 which coupled with its small reorganization energy and its ability for promoting fast charge separation with slow charge recombination, has prompted its incorporation in P/Pc-based materials.
No covalently bonded systems built of metal porphyrins/ phthalocyanines and fullerene derivatives are similar to the natural photosynthetic reaction center. The study of these models is very important for understanding the processes occurring in the initial stages of photosynthesis. Supramolecular coordination systems composed of pyridine or imidazole groups appending fullerene derivatives as the electron acceptor and metal porphyrins as the donor are most like the natural complexes.1,7 Pyridyl-substituted pyrrolidinofullerenes have been used as materials in organic solar cells in combination with zinc phthalocyanine.8 Photoactive phthalocyanine-fullerene supramolecular systems have also been successfully applied in the design of bulk heterojunction and mixed heterojunction solar cells.9,10 Many selfassembled dyads composed of pyrrolidinofullerenes and metal porphyrins/phthalocyanines have been investigated in solution. These are based on pyrrolidinofullerenes bearing one chelating pyridyl or imidazolyl group,11e13 two chelating substituents at the 20 and 50 or 10 and 20 positions of the pyrrolidine ring14e16 or even three chelating pyridyl units at positions 10, 20 , 50 .17,18 The number of fullerene molecules coordinated to the metal porphyrin depends on the central metal. The triad composed of cis-20 ,50 -di(3-pyridyl) pyrrolidino[30 ,40 :1,2][60]fullerene and two MnIITPP (TPPdtetraphenylporphin dianion) molecules has been recently obtained for the first time.19 The interaction of fullerene derivatives containing chelating groups with tetraazaporphyrins as analogues of porphyrins and phthalocyanines has received little attention.20 The formation of
* Corresponding author. E-mail address: [email protected] (E.N. Ovchenkova). http://dx.doi.org/10.1016/j.tet.2015.07.054 0040-4020/Ó 2015 Published by Elsevier Ltd.
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charge separation states such as C (Ncdnaph60eIm/ZnNc thapocyanine dianion) was confirmed. In this work, we report our study of the donoreacceptor type bonding using (acetato)(octakis(4-tert-butyl-phenyl)tetraazaporphyrinato)manganese(III) (AcP)MnTAP(4-t-BuC6H4)8 (1) as the electron donor and 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene (Py3F) (2) as the electron acceptor and determine the optimum conditions for the metal tetraazaporphyrin/fullerene supramolecular system formation.
2. Results and discussion The purity of synthesized complex 1 was confirmed by its elemental composition and electronic absorption, IR, and mass spectra which are identical with the data reported by authors,21 who have first obtained and identified this complex. The UVevis spectra were characteristic of five-coordinate manganese complexes (AcO) MnIIITAP(4-t-BuC6H4)8.22 The spectrum of 1 in toluene contains two maxima at l 413 (B-band) and 673 (Q-band) nm. The comparison of the electronic absorption spectra of complex 1 and manganese(III) porphyrin complexes shows that the introduction of aza-bridges instead of methyne ones causes a large bathochromic shift of the Q-band (lmax 618 and 673 nm for (AcO)MnTPP23 and for (AcO) MnTAP(4-t-BuC6H4)8, respectively, in CHCl3). The azasubstitution removes the quasi-forbidding nature from the electronic transitions corresponding to the absorption bands of porphyrin complexes in the visible region. As a result bands the intensity of (AcO) MnTAP(4-t-BuC6H4)8 in this spectral region is significantly higher than that of (AcO)MnTPP.24 This enables us to study the reaction kinetics of complex 1 with the compound 2 as N-donor ligand by spectrophotometric methods (Experimental section). The addition of 2 to a solution of the compound 1 in toluene causes a gradual decrease in intensity and a small hypsochromic shift (3 nm) of the band at 673 nm (Fig. 2) that is indicative of slow reaction passage. As follows from Fig. 2, the UVevis spectra of the
Fig. 2. Change in the UVevis spectrum of (AcP)MnTAP(4-t-BuC6H4)8 during the reaction with fullerene (CPy3 F ¼1.05105 M) in toluene at the initial instant of the reaction (1) and after 24 h (2) at 298 K. Other lines correspond to intermediate times.
product do not change drastically, and they are typical the macrocyclic chromophore coordinated to manganese (III). A straight-line dependence (Fig. 3) in the coordinates of the Eq. 1 of formal first order with respect to the compound 1 was observed in the kinetics measurements.25
kef ¼
1
s
ln
A0 AN As AN
(1)
Here, A0, As, AN are the optical densities of complex 1, of the reaction mixture at s time and in the reaction product at the working wavelength. The values of the effective rate constant of the first order with respect to (porphyrinato)manganese (III) (kef, Table 1) were optimized by the least squares procedure using Microsoft Excel. The relative error in determination of kef did not exceed 10%. The reaction order with respect to Py3F was determined from the slope of the lgkefelgCPy3 F dependence (Fig. 4). Unexpectedly, the order is a negative value (1.21). The above mentioned results allow us to generate the kinetic equation for the reaction between the compounds 1 and 2:
. 1 1 dCðAcOÞMnTAPð4tBuC6 H4 Þ8 ds ¼ k$CðAcOÞMnTAPð4tBuC6 H4 Þ8 $CPy ¼ ¼ ð2:50 0:26Þ$108 $CðAcOÞMnTAPð4tBuC6 H4 Þ8 $CPy 3F 3F
(2)
Fig. 3. Plot of lg(C0/Cs) versus s for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene. CPy3 F ¼2.09105 (1), 3.14105 (2), 3.56105 (3), 4.18105 (4), 5.02105 (5) M (R2¼0.991O0.999).
Fig. 1. Molecular structures of the compounds studied.
The value of the constant k (mol.L1.s1) was found by optimization of the dependence shown in Fig. 4. Previously we have tested the influence of the solvent and the effects of an association and an aggregation of Py3F on the reaction kinetics of metal tetraazaporphyrin-fullerene dyad formation. For the same reaction in chloroform, the changes in the UVevis spectra
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Table 1 The effective rate constant kef for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene at 298 K CPy3 F 105/M
(kefdkef).103/s1
2.09 2.58 3.14 3.56 4.18 5.02
1.410.09 1.010.07 0.770.07 0.710.01 0.620.03 0.460.04
Fig. 6. IR spectra of (a) (AcP)MnTAP(4-t-BuC6H4)8, (b) 20 -(4-pyridyl)-50 -(2-pyridyl)-10 (3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene and (c) its molecular complex in KBr. Bands corresponding to vibrations of C60-pyridyl are denoted with asterisks. Fig. 4. Plot of lgkef versus lgCPy3 F for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene at 298 K (R2¼0.988).
and the dependence of the effective rate constant versus concentration of Py3F are analogous to the reaction in toluene. The investigation of UVevis spectrum of Py3F solutions in toluene in the concentration range 0.59105O2.84105 M showed the absence of a shift in absorption bands position (Fig. 5). The change in the absorption bands intensity in the dilute solutions of fullerene 2 is submitted to the BouguereLamberteBeer law. Also the spectrum of fullerene in toluene remains constant in time (5 h).
Fig. 5. UVevis spectra of Py3F in toluene at 298 L. CPy3 F ¼2.84105 (1), 2.37105 (2), 1.76105 (3), 1.21105 (4), 0.59105 (5) M.
The new absorption bands at 1587, 1512, 1427, 1374, 1168, 1064, 1024, 801, 710, 527 cm1 due to vibrations of coordinated Py3F have appeared in the IR spectrum of the reaction product (Fig. 6); no such bands were observed in the spectrum of initial compound 1. The bands at 1427 and 527 cm1 correspond to the vibrations of fullerene S60 and their position is unchanged in the spectrum of the reaction product.26 The other vibration frequencies of fragments Py3F due to vibrations of pyridine and pyrrolidinyl rings are shifted by 2e6 cm1 when compared with those of free fullerene Py3F (see Experimental section).27 In the IR spectrum of the reaction product in CsBr we detected a new signal with frequency at 232 cm1 due to vibrations of the MneN bond in the pyridyl fragment of C60pyridyl.28,29 The presence and the state of acetate ion in initial complex 1 and in the reaction product 3 can also be analyzed by IR spectroscopy.
The absorption bands at 1609 cm1 (nas(OeCeO), 1384 cm1 (ns(OeCeO)) and the weak signal at 1717 cm1 (n(C]O))27 belong to the acetate ligand in the IR spectrum of 1. The low intensity of n(C]O) and position of two first signals indicate a bidentate coordination of the acetate ion30 in complex 1 (Fig. 1). Indeed, the difference in the frequencies of two vibrations (nas(OeCeO) and ns(OeCeO)) is 225 cm1, which is greater than that for the acetate complexes30 (<225 cm1) and lower for the monodentate coordination (300 cm1) of the carboxyl group. In the IR spectrum of the product 3 (Fig. 6b) a less intense peak at 1374 cm1 due to vibrations of the fullerene base appears in place of the signal ns(OeCeO) at 1384 cm1. The vibration signal ns(OeCeO) is observed at 1427 cm1 in the form of a complicated band, which is overlapped with a signal of C60-pyridyl. The difference in the frequencies (Dn) of two vibrations of group OeCeO is 182 cm1 for the reaction product 3 that points out the ion type of AcO binding in complex 3. Thus, the reaction product 3 contains the molecular ligand Py3F in the first coordination sphere according to IR spectroscopy data. Acetate ion is a counter-anion and is placed in the second coordination sphere as [(Py3F)MnTAP(4-t-BuC6H4)8]þAcO. UV-visible spectroscopy data do not contradict the idea of axial coordination of fullerene-containing N-base by (tetraazaporphyrinato) manganese(III). In our work,31 we have studied the coordination of imidazole (Im) with the compound 1. Manganese(III) complex 1 was found to react with imidazole with the formation of 1:1 complexe in a one-step reversible process. The addition of imidazole to the solution of (AcP)MnTAP(4-t-BuC6H4)8 in toluene induces a bathochromic shift of the Q-band by 2 nm whereas the interaction of complex 1 with Py3F is accompanied by a hypsochromic shift. According to the data,32 analogous reaction of (AcO)MnOPTAP (OPTAPe2,3,7,8,12,13,17,18-octaphenyltetraazaporphyrin dianion) and tetrahydrofuran in toluene is attended by a hypsochromic shift (by 6 nm) of the long-wave absorption band in comparison with the corresponding band of the initial manganese complex as in the case with Py3F. Taking into account the data,31,32 it can be argued that the various band shift directions in the cases of axial complex formation with tetrahydrofuran/Py3F (p-acceptors) and with Im (p-donor) are explained by the presence of dative p-electron MneN interactions and their absence, respectively. This is caused by a combination of
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electronic effects of coordination and functional substitution. Eight electron-withdrawing phenyl groups in (AcO)MnOPTAP promote the formation of the dative p-bonds O/Mn in the axial complex with tetrahydrofuran. Whereas the 4-t-BuC6H4 substituents in complex 1 and Im as the axial ligand exhibit mutually compensative electron-donor properties in the reaction of (AcO)MnTAP(4-tBuC6H4)8 with Im. Using experimental (electronic spectroscopy)33 and theoreti34 cal methods, a frontier orbital diagram was constructed for tetraazazporphyrin iron(III) complexes, and the absorption bands in their electronic spectra were assigned: the Q-band was attributed to charge transfer from the a1 orbital to dp (dp stands for dxz and dyz orbitals) and the B-band, to electronic transition a1/d2z . Variations in the UVevis spectrum of complex 1 upon addition of Py3F may be interpreted on the basis of the above assignment of absorption bands and known analogy between manganese(III) and iron(III) complexes. The dxz, dyz orbitals participate in transmission of an opposite p-effect from the manganese atom and macroring to the fullerene molecule, which stabilizes the dp and a1 orbitals. A hypsochromic shift of Q-band is explained by the smaller change in the energy of the molecular orbital (a1) from which electron transition a1/dp is realized (Fig. 7). The reduction in intensity of the Q-band is related to the opposite direction of the p-effect Py3F)Mn. The energy of orbitals involved in other electronic transitions in the optical range change to a considerably lesser extent.
Fig. 7. Shifts of absorption bands in the UVevis spectra of (AcP)MnTAP(4-t-BuC6H4)8 upon addition of 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino [30 ,40 :1,2][60]-fullerene molecule.
Dyad 3 formation was confirmed by 1H NMR spectroscopy as one of the main methods for molecular structure analysis of porphyrins and their complexes.28,35,36 The 1H NMR spectrum of 1 obtained in CDC13 at 298 K is shown in Fig. 8a. Due to manganese paramagnetism, the phenyl proton resonances are shifted and broadened as compared to 1H NMR spectra of diamagnetic analogues.29 The signals of the o-protons are shifted upfield to 3.82 and 2.85 ppm. The m-proton resonances are shifted downfield to 8.0 and 7.31 ppm. The signal of tert-butyl group protons is located at about 2.0 ppm as expected. Meta-, ortho- and para-proton resonances of the pyridyl substituents in Py3F spectrum appear in the range of 9.08e7.17 ppm (Fig. 8b). The signals of the methine group protons are observed as two doublets at 4.36 and 4.17 ppm while that for the methylene group protons appears as a singlet with a chemical shift at 5.94 ppm. The 1H NMR spectrum of the compound 3 is shown in Fig. 8c. The intense signal for the tert-butyl groups with a chemical shift at 2.08 ppm in the spectrum of initial manganese complex 1 shifts in the field of 0e1.8 ppm in the spectrum of the dyad. This evidences about the change in the deshielding degree of t-Bu protons in the porphyrin/fullerene dyad under the influence of the coordinated molecule of Py3F, i.e. about a redistribution of electron density in the supramolecule. Taking into account the kinetic and physicochemical data, the reaction of (acetato)(octakis(4-tert-butyl-phenyl)tetraazaporphyrinato)manganese(III) with 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3pyridylmethyl)pyrrolidino-[30 ,40 :1,2][60]-fullerene can be
Fig. 8. 1H NMR spectra of compounds (a) 1, (b) 2 and (c) 3 in CDCl3.
interpreted as a two-stage process of donor-acceptor interaction limited by irreversible displacement of the bidentate coordinated acetate ion in (AcO)(Py3F)MnTAP(4-t-BuC6H4)8 (Fig. 9) into the second coordination sphere:
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E.N. Ovchenkova et al. / Tetrahedron xxx (2015) 1e6
Fig. 9. Chemical structure of (AcO)(Py3F)MnTAP(4-t-BuC6H4)8. The similar donoreacceptor complexes structures optimized by quantum-chemical method have been presented earlier.11,37
fast
ðAcOÞMnTAPð4 tBuC6 H4 Þ8 þ Py3 F! ðAcOÞðPy3 FÞMnTAPð4 tBuC6 H4 Þ8
(3)
k
ðAcOÞðPy3 FÞMnTAPð4 tBuC6 H4 Þ8 / þ ðPy3 FÞMnTAPð4 tBuC6 H4 Þ8 AcO
(4)
Obviously, the monomolecular reaction (4) is to be of zero order with respect to Py3F. However, the mixture of Py3F with toluene is a medium with a basicity that is as stronger as concentration of Py3F is higher. That’s why, its action induces a difficulty in displacement of AcO from the first coordination sphere and results in the apparent first negative order of the reaction (1) with respect to the base. 3. Conclusion We have described the formation of donoreacceptor Mn(III) tetraazaporphyrin/C60-pyridyl supramolecular system 3 from tetraazaporphyrin complex manganese(III) 1 and 20 -(4-pyridyl)-50 -(2pyridyl)-10 -(3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene 2. The kinetics of dyad formation in toluene were studied spectrophotometrically at 298 K and the rate constant k¼(2.500.26).108 mol L1 s1 was determined. The inverse dependence of the reaction rate on the fullerene concentration connected with the features of the stoichiometric reaction mechanism and with medium effects was observed. Identification of the dyad 3 [(Py3F)MnTAP(4-t-BuC6H4)8]þAcO as an outer-sphere acetate complex of a donoreacceptor dyad was confirmed by UV-visible, IR and 1H NMR spectroscopy. On the basis of self-assembly properties of the obtained porphyrin/fullerene dyad and taking into account prospects of porphyrin/fullerene supramolecular systems as components for photoactive materials28,38 and synergistic antimicrobial compositions,29,39e41 we envisage future applications of data obtained in our work in photovoltaics and biomedicine. The equation of the Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system formation rate (Eq. 2) can be used for compilation of the technological tetraazaporphyrin/fullerene dyad synthesis regulations.
5
2.9 mmol) and Mn(OAc)2$4H2O (0.9 g, 3.5 mmol) in 2dimethylaminoethanol (7 ml) was heated gradually with stirring to 150 C and the temperature was maintained for 10 h. Completion of the reaction was monitored by TLC, until no traces of starting material were detected. The reaction mixture was cooled, poured into methanol (50 ml) and the precipitate was centrifuged. For purification, the product was dissolved in chloroform (10 ml) and an equal amount of methanol (10 ml) was added to the solution. Chloroform was partially removed from the obtained solution using a rotary evaporator, and the precipitate formed was filtered off, purified by flash chromatography (silica gel/CHCl3e1% CH3OH) and dried under vacuum (60 C, 24 h). Yield: 0.52 g (0.35 mmol, 48%). UVevis (toluene) lmax nm (log ε): 421 (4.51), 494 (4.50), 619 sh, 673 (4.74). IR (KBr) nmax cm1: 2962, 2905, 2868, 1717, 1609, 1384, 1364, 1299, 1269, 1197, 1147, 1109, 997, 891, 850, 839, 811, 751, 635, 599, 585, 563. IR (CsBr) nmax cm1: 508, 479, 406, 362, 299. Found: C 78.82, H 7.47, N 7.31%. C98H107N8O2Mn requires C 79.32, H 7.27, N 7.55%. MS (MALDI-TOF) m/z: 1423.78 [MnTAP(4-t-BuC6H4)8]þ (calcd. For C96H104N8Mn 1423.0). 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino [30 ,40 :1,2][60]fullerene Py3F was provided by Dr Troshin P. A. and was synthesized by reaction of fullerene C60 with azomethinylid in 1,2-dichlorobenzene.42 UVevis (toluene) lmax nm (log ε): 294, 313, 433 (3.82) nm. IR (KBr) nmax cm1: 1721, 1689, 1636, 1587, 1572, 1455, 1426, 1377, 1356, 1307, 1279, 1231, 1215, 1187, 1157, 1123, 1096, 1064, 1048, 1026, 996, 962, 876, 845, 824, 799, 748, 711, 672, 627, 599, 574, 548, 527, 481, 399. 1H NMR (400 MHz; d, ppm; CDCl3): 9.08 (d, J¼4.7 Hz, 1H), 8.87e8.82 (m, 3H), 8.53e8.50 (m, 2H), 8.04e8.00 (m, 1H), 7.83e7.80 (m, 2H), 7.47e7.45 (m, 2H), 7.20e7.19 (m, 1H), 5.94 (s, 2H), 4.36 (d, J¼15.1 Hz, 1H), 4.17 (d, J¼15.3 Hz, 1H). 4.2. Spectroscopy The UVevis spectra were measured on Agilent 8453 UV-visible spectrophotometers; IR and 1H NMR spectra were recorded on VERTEX 80v and Bruker Avance III-500 NMR spectrometers, respectively; elemental analysis was performed on Euro EA 3000; mass spectra was performed on Bruker Autoflex; all 1H NMR measurements were carried out at room temperature in deuterochloroform (CDCl3). 4.3. Kinetics
4. Experimental section
The kinetics of the reaction between (AcP)MnTAP(4-t-BuC6H4)8 and Py3F in toluene was studied spectrophotometrically over a wide range of concentrations of Py3F (0e5.44 105 M) at 298 K by excess concentrations method. The upper concentration limit of fullerene 2 is determined by solubility of the latter in toluene. The solutions of 1 and 2 in freshly distilled toluene were prepared directly before use in order to avoid the formation of peroxides in the solvent. The optical density measurements on the wavelength of 673 nm for compound 1 solution series at constant concentration of 1 (5.31106 M) with different additions of the base 2 were carried out immediately after mixing of the reagents. Since Py3F absorbs in this range, the spectra of the Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system were monitored in subtraction mode using the spectrum of the base 2 of the same concentration as in the stock solution as a zero line. The solutions were thermostatted at 298 K in a closed quartz cuvette in the special spectrophotometer cell. The temperature control accuracy was 0.1 K.
4.1. Synthesis
Acknowledgements
(Octakis(4-tert-butyl-phenyl)tetraazaporphyrinato) manganese(III) acetate (AcP)MnTAP(4-t-BuC6H4)8 was synthesized as follows. A mixture of bis(4-tert-butylphenyl)fumaronitrile (1 g,
We appreciate Prof. Klyuev M. V assistance in choice of fullerene derivative. This work was carried out with the help of the centre of the scientific equipment collective use ‘The upper Volga region
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centre of physic-chemical research’ and with the financial support from grants of the Presidium of the Russian Academy of Sciences (Program No. 8, 2014) and RFBR, No 15-03-00646-a. References and notes 1. Guldi, D. M. Chem. Soc. Rev. 2002, 31, 22. 2. Ito, O.; D’Souza, F. Molecules 2012, 17, 5816. 3. Allemand, P. M.; Khemani, K. C.; Koch, A.; Wudl, F.; Holczer, K.; Donovan, S.; € ner, G.; Thompson, J. D. Science 1991, 253, 301. Gru 4. Konarev, D. V.; Khasanov, S. S.; Otsuka, A.; Maesato, M.; Saito, G.; Lyubovskaya, R. N. Angew. Chem., Int. Ed. 2010, 49, 4829. 5. Guldi, D. M. Chem. Commun. 2000, 321. 6. RSC Nanoscience and Nanotechnology Series; Langa, F., Nierengarten, J. F., Eds.; 2007. 7. Meijer, M.; Van Klink, G. P.; Van Koten, G. Coord. Chem. Rev. 2002, 230, 141. 8. Troshin, P. A.; Lyubovskay, R. N.; Peregudov, A. S.; Troyanov, S. I. Rus. Chem. Bull. 2008, 57, 887. 9. Troshin, P. A.; Koeppe, R.; Peregudov, A. S.; Peregudova, S. M.; Egginger, M.; Lyubovskaya, R. N.; Sariciftci, N. S. Chem. Mater. 2007, 19, 5363. 10. Loi, M. A.; Denk, P.; Hoppe, H.; Neugebauer, H.; Winder, C.; Meissner, D.; Brabec, C.; Sariciftci, N. S.; Gouloumis, A.; Vazquez, P.; Torres, T. J. Mater. Chem. 2003, 13, 700. 11. Lomova, T. N.; Malov, M. E.; Klyuev, M. V.; Troshin, P. A. Macroheterocycles 2009, 2, 164. 12. D’Souza, F.; Deviprasad, G. R.; Zandler, M. E.; Hoang, V. T.; Klykov, A.; Van Stipdonk, M.; Perera, A.; El-Khouly, M. E.; Fujitsuka, M.; Ito, O. J. Phys. Chem. A 2002, 106, 3243. 13. Motorina, E. V.; Lomova, T. N.; Troshin, P. A.; Klyuev, M. V. Zh. Obsch. Khim. 2014, 84, 855 Russ. J. Gen. Chem. 2014, 84, 946. 14. El-Khouly, M. E.; Gadde, S.; Deviprasad, G. R.; Fujitsuka, M.; Ito, O.; D’Souza, F. J. Porphyrins Phthalocyanines 2003, 7, 1. 15. Mochalov, I. A.; Lapshin, A. N.; Nadtochenko, V. A.; Smirnov, V. A.; Goldshleger, N. F. Izv. Akad. Nauk, Ser. Khim. 2006, 55, 1541 Russ. Chem. Bull., Int. Ed. 2006, 55, 1598. 16. Lomova, T. N.; Motorina, E. V.; Klyuev, M. V. Macroheterocycles 2013, 6, 327. 17. Lapshin, A. N.; Smirnov, V. A.; Lyubovskaya, R. N.; Goldshleger, N. F. Izv. Akad. Nauk, Ser. Khim. 2005, 54, 2265 Russ. Chem. Bull., Int. Ed. 2005, 54, 2338. 18. Koeppe, R.; Troshin, P. A.; Fuchsbauer, A.; Lyubovskaya, R. N.; Sariciftci, N. S. Fullerenes, Nanotubes, Carbon Nanostruct. 2006, 14, 441.
19. Konarev, D. V.; Khasanov, S. S.; Kornev, A. B.; Faraonov, M. A.; Troshin, P. A.; Lyubovskaya, R. N. Dalton Trans. 2012, 41, 791. 20. Sandanayaka, A. S. D.; Ito, O. J. Porphyrins Phthalocyanines 2009, 13, 1033. 21. Ovchenkova, E. N.; Lomova, T. N.; Hanack, M. Macroheterocycles 2010, 3, 63. 22. Klueva, M. E.; Repina, N. V.; Chizhova, N. V.; Berezin, B. D. Zh. Koord. Khim. 2010, 31, 22 Rus. J. Coord. Chem. 2005, 31, 19. 23. Lomova, T. N.; Kluev, M. V.; Ovchenkova, E. N.; Klueva, M. E. Zh. Obsch. Khim. 2010, 80, 841 Russ. J. Gen. Chem. 2010, 80, 1011. 24. Enikolopyan, N. S. Porfiriny: Struktura, Svoistva, Sintez (Porphyrins: Structure, Properties, and Synthesis); Nauka: Moscow, Russia, 1985. 25. Budanov, V. V.; Lomova, T. N.; Rybkin, V. V. Khimicheskaya Kinetika(Chemical Kinetics); Lan: St. Petersburg, Russia, 2014. 26. Eletskiǐ, A. V.; Smirnov, B. M. Phys. Uspekhi 1993, 36, 202. 27. Nakanishi, K. Infrared Absorption Spectroscopy; Holden-Day, San Francisco and Nankodo Company Limited: Tokyo, Japan, 1962. 28. Kathleen, M. M.; Gunter, M. J. J. Org. Chem. 2008, 73, 3336. 29. La Mar, G. N.; Walker, F. A. J. Am. Chem. Soc. 1973, 95, 6950. 30. Lomova, T. N.; Tyulyaeva, E. Yu.; Bachurova, S. E. Zh. Neorg. Khim. 2010, 55, 690 Russ. J. Inorg. Chem. 2010, 55, 640. 31. Ovchenkova, E. N.; Lomova, T. N. Russ. Zh. Org. Khim. 2011, 47, 1551 J. Org. Chem. 2011, 47, 1581. 32. Klyueva, M. E.; Berezin, B. D.; Repina, N. V. Zh. Neorg. Khim. 2005, 50, 510 Russ. J. Inorg. Chem. 2005, 50, 454. 33. Edwards, W. D.; Weiner, B.; Zerner, M. C. J. Phys. Chem. 1988, 92, 188. 34. Stuzhin, P. A.; Hamdush, M.; Ziener, U. Inorg. Chim. Acta 1995, 236, 31. 35. Khodov, I. A.; Nikiforov, M. Y.; Alper, G. A.; Mamardashvili, G. M.; Mamardashvili, N. Z.; Koifman, O. I. J. Mol. Struct. 2015, 1081, 426. 36. Bichan, N. G.; Tyulyaeva, E. Yu.; Khodov, I. A.; Lomova, T. N. J. Mol. Struct. 2014, 1061, 82. 37. Lomova, T. N.; Malov, M. E.; Klyuev, M. V.; Troshin, P. A. In Advances in Materials Science Research; Wythers, M. C., Ed.; Nova Science: New York, NY, 2011; Vol. 2, pp 143e154. 38. Grin, M. A.; Lonin, I. S.; Likhosherstov, L. M.; Novikova, O. S.; Plyutinskaya, A. D.; Plotnikova, E. A.; Kachala, V. V.; Yakubovskaya, R. I.; Mironov, A. F. J. Porphyrins Phthalocyanines 2012, 16, 1094. 39. Cheremisina, I. M. Zh. Structur. Khim. 1978, 19, 336. 40. Saito, Y.; Takemoto, J.; Hutschinson, B.; Nakamoto, K. Inorg. Chem. 1972, 11, 2003. 41. Zhao, H.; Zhu, Y.; Chen, C.; Zheng, J. Polymer 2014, 55, 1913. 42. Troshin, P. A.; Troyanov, S. I.; Boiko, G. N.; Lyubovskaya, R. N.; Lapshin, A. N.; Goldshleger, N. F. Fullerenes, Nanotubes, Carbon Nanostruct. 2004, 12, 435.
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Kinetics of Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system formation Ekaterina N. Ovchenkova *, Nataliya G. Bichan, Tatyana N. Lomova G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 April 2015 Received in revised form 6 July 2015 Accepted 20 July 2015 Available online xxx
The reaction of (octakis(4-tert-butyl-phenyl)tetraazaporphyrinato) manganese(III) acetate ((AcO) MnTAP(p-t-BuC6H4)8) with 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)-pyrrolidino[30 ,40 :1,2][60] fullerene (Py3F) in toluene was studied by methods of chemical kinetics and UV, visible, IR and 1H NMR spectroscopy. The interaction is found to result in the formation of 1:1 donor-acceptor complex whose structure was determined. A negative value of a complex formation order with respect to Py3F was established and explained. The kinetic equation can be used in the development of technology of metal tetraazaporphyrin-fullerene dyad production. Ó 2015 Published by Elsevier Ltd.
Keywords: Tetraazaporphyrin Manganese(III) complexes Pyridine substituted pyrrolidino[60] fullerene Donor-acceptor dyad
1. Introduction The ability of metal porphyrins/phthalocyanines (P/Pc) to form coordination assemblies due to axial metal-ligand interactions can successfully be used in the design of complexes with some fullerene derivatives. Supramolecular dyads of metal porphyrins/phthalocyanines with fullerenes show promising photophysical, ferromagnetic, superconducting and unusual optical properties.1e4 Porphyrins and phthalocyanines are aromatic macrocyclic compounds which present rich redox chemistry coupled to an absorption in the red/near infrared (IR) region of the solar spectrum with high extinction coefficients and fluorescence quantum yields. The unique physicochemical features of these compounds make them ideal molecular components for the preparation of photoactive, donoreacceptor (DeA) ensembles. In such systems, the Pcs’ role is twofold: first, they function as antennas due to their excellent optical absorption in the visible region of the emission solar spectrum; and second, once photo-excited, they act as electron donors. Among the acceptor moieties that have been chosen as molecular partners for porphyrins/phthalocyanines, fullerene and their derivatives have a privileged position. This spherical carbon nanostructure in fact possesses an extraordinary electron acceptor property,1,5,6 which coupled with its small reorganization energy and its ability for promoting fast charge separation with slow charge recombination, has prompted its incorporation in P/Pc-based materials.
No covalently bonded systems built of metal porphyrins/ phthalocyanines and fullerene derivatives are similar to the natural photosynthetic reaction center. The study of these models is very important for understanding the processes occurring in the initial stages of photosynthesis. Supramolecular coordination systems composed of pyridine or imidazole groups appending fullerene derivatives as the electron acceptor and metal porphyrins as the donor are most like the natural complexes.1,7 Pyridyl-substituted pyrrolidinofullerenes have been used as materials in organic solar cells in combination with zinc phthalocyanine.8 Photoactive phthalocyanine-fullerene supramolecular systems have also been successfully applied in the design of bulk heterojunction and mixed heterojunction solar cells.9,10 Many selfassembled dyads composed of pyrrolidinofullerenes and metal porphyrins/phthalocyanines have been investigated in solution. These are based on pyrrolidinofullerenes bearing one chelating pyridyl or imidazolyl group,11e13 two chelating substituents at the 20 and 50 or 10 and 20 positions of the pyrrolidine ring14e16 or even three chelating pyridyl units at positions 10, 20 , 50 .17,18 The number of fullerene molecules coordinated to the metal porphyrin depends on the central metal. The triad composed of cis-20 ,50 -di(3-pyridyl) pyrrolidino[30 ,40 :1,2][60]fullerene and two MnIITPP (TPPdtetraphenylporphin dianion) molecules has been recently obtained for the first time.19 The interaction of fullerene derivatives containing chelating groups with tetraazaporphyrins as analogues of porphyrins and phthalocyanines has received little attention.20 The formation of
* Corresponding author. E-mail address: [email protected] (E.N. Ovchenkova). http://dx.doi.org/10.1016/j.tet.2015.07.054 0040-4020/Ó 2015 Published by Elsevier Ltd.
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charge separation states such as C (Ncdnaph60eIm/ZnNc thapocyanine dianion) was confirmed. In this work, we report our study of the donoreacceptor type bonding using (acetato)(octakis(4-tert-butyl-phenyl)tetraazaporphyrinato)manganese(III) (AcP)MnTAP(4-t-BuC6H4)8 (1) as the electron donor and 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene (Py3F) (2) as the electron acceptor and determine the optimum conditions for the metal tetraazaporphyrin/fullerene supramolecular system formation.
2. Results and discussion The purity of synthesized complex 1 was confirmed by its elemental composition and electronic absorption, IR, and mass spectra which are identical with the data reported by authors,21 who have first obtained and identified this complex. The UVevis spectra were characteristic of five-coordinate manganese complexes (AcO) MnIIITAP(4-t-BuC6H4)8.22 The spectrum of 1 in toluene contains two maxima at l 413 (B-band) and 673 (Q-band) nm. The comparison of the electronic absorption spectra of complex 1 and manganese(III) porphyrin complexes shows that the introduction of aza-bridges instead of methyne ones causes a large bathochromic shift of the Q-band (lmax 618 and 673 nm for (AcO)MnTPP23 and for (AcO) MnTAP(4-t-BuC6H4)8, respectively, in CHCl3). The azasubstitution removes the quasi-forbidding nature from the electronic transitions corresponding to the absorption bands of porphyrin complexes in the visible region. As a result bands the intensity of (AcO) MnTAP(4-t-BuC6H4)8 in this spectral region is significantly higher than that of (AcO)MnTPP.24 This enables us to study the reaction kinetics of complex 1 with the compound 2 as N-donor ligand by spectrophotometric methods (Experimental section). The addition of 2 to a solution of the compound 1 in toluene causes a gradual decrease in intensity and a small hypsochromic shift (3 nm) of the band at 673 nm (Fig. 2) that is indicative of slow reaction passage. As follows from Fig. 2, the UVevis spectra of the
Fig. 2. Change in the UVevis spectrum of (AcP)MnTAP(4-t-BuC6H4)8 during the reaction with fullerene (CPy3 F ¼1.05105 M) in toluene at the initial instant of the reaction (1) and after 24 h (2) at 298 K. Other lines correspond to intermediate times.
product do not change drastically, and they are typical the macrocyclic chromophore coordinated to manganese (III). A straight-line dependence (Fig. 3) in the coordinates of the Eq. 1 of formal first order with respect to the compound 1 was observed in the kinetics measurements.25
kef ¼
1
s
ln
A0 AN As AN
(1)
Here, A0, As, AN are the optical densities of complex 1, of the reaction mixture at s time and in the reaction product at the working wavelength. The values of the effective rate constant of the first order with respect to (porphyrinato)manganese (III) (kef, Table 1) were optimized by the least squares procedure using Microsoft Excel. The relative error in determination of kef did not exceed 10%. The reaction order with respect to Py3F was determined from the slope of the lgkefelgCPy3 F dependence (Fig. 4). Unexpectedly, the order is a negative value (1.21). The above mentioned results allow us to generate the kinetic equation for the reaction between the compounds 1 and 2:
. 1 1 dCðAcOÞMnTAPð4tBuC6 H4 Þ8 ds ¼ k$CðAcOÞMnTAPð4tBuC6 H4 Þ8 $CPy ¼ ¼ ð2:50 0:26Þ$108 $CðAcOÞMnTAPð4tBuC6 H4 Þ8 $CPy 3F 3F
(2)
Fig. 3. Plot of lg(C0/Cs) versus s for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene. CPy3 F ¼2.09105 (1), 3.14105 (2), 3.56105 (3), 4.18105 (4), 5.02105 (5) M (R2¼0.991O0.999).
Fig. 1. Molecular structures of the compounds studied.
The value of the constant k (mol.L1.s1) was found by optimization of the dependence shown in Fig. 4. Previously we have tested the influence of the solvent and the effects of an association and an aggregation of Py3F on the reaction kinetics of metal tetraazaporphyrin-fullerene dyad formation. For the same reaction in chloroform, the changes in the UVevis spectra
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3
Table 1 The effective rate constant kef for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene at 298 K CPy3 F 105/M
(kefdkef).103/s1
2.09 2.58 3.14 3.56 4.18 5.02
1.410.09 1.010.07 0.770.07 0.710.01 0.620.03 0.460.04
Fig. 6. IR spectra of (a) (AcP)MnTAP(4-t-BuC6H4)8, (b) 20 -(4-pyridyl)-50 -(2-pyridyl)-10 (3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene and (c) its molecular complex in KBr. Bands corresponding to vibrations of C60-pyridyl are denoted with asterisks. Fig. 4. Plot of lgkef versus lgCPy3 F for the reaction of (AcP)MnTAP(4-t-BuC6H4)8 with Py3F in toluene at 298 K (R2¼0.988).
and the dependence of the effective rate constant versus concentration of Py3F are analogous to the reaction in toluene. The investigation of UVevis spectrum of Py3F solutions in toluene in the concentration range 0.59105O2.84105 M showed the absence of a shift in absorption bands position (Fig. 5). The change in the absorption bands intensity in the dilute solutions of fullerene 2 is submitted to the BouguereLamberteBeer law. Also the spectrum of fullerene in toluene remains constant in time (5 h).
Fig. 5. UVevis spectra of Py3F in toluene at 298 L. CPy3 F ¼2.84105 (1), 2.37105 (2), 1.76105 (3), 1.21105 (4), 0.59105 (5) M.
The new absorption bands at 1587, 1512, 1427, 1374, 1168, 1064, 1024, 801, 710, 527 cm1 due to vibrations of coordinated Py3F have appeared in the IR spectrum of the reaction product (Fig. 6); no such bands were observed in the spectrum of initial compound 1. The bands at 1427 and 527 cm1 correspond to the vibrations of fullerene S60 and their position is unchanged in the spectrum of the reaction product.26 The other vibration frequencies of fragments Py3F due to vibrations of pyridine and pyrrolidinyl rings are shifted by 2e6 cm1 when compared with those of free fullerene Py3F (see Experimental section).27 In the IR spectrum of the reaction product in CsBr we detected a new signal with frequency at 232 cm1 due to vibrations of the MneN bond in the pyridyl fragment of C60pyridyl.28,29 The presence and the state of acetate ion in initial complex 1 and in the reaction product 3 can also be analyzed by IR spectroscopy.
The absorption bands at 1609 cm1 (nas(OeCeO), 1384 cm1 (ns(OeCeO)) and the weak signal at 1717 cm1 (n(C]O))27 belong to the acetate ligand in the IR spectrum of 1. The low intensity of n(C]O) and position of two first signals indicate a bidentate coordination of the acetate ion30 in complex 1 (Fig. 1). Indeed, the difference in the frequencies of two vibrations (nas(OeCeO) and ns(OeCeO)) is 225 cm1, which is greater than that for the acetate complexes30 (<225 cm1) and lower for the monodentate coordination (300 cm1) of the carboxyl group. In the IR spectrum of the product 3 (Fig. 6b) a less intense peak at 1374 cm1 due to vibrations of the fullerene base appears in place of the signal ns(OeCeO) at 1384 cm1. The vibration signal ns(OeCeO) is observed at 1427 cm1 in the form of a complicated band, which is overlapped with a signal of C60-pyridyl. The difference in the frequencies (Dn) of two vibrations of group OeCeO is 182 cm1 for the reaction product 3 that points out the ion type of AcO binding in complex 3. Thus, the reaction product 3 contains the molecular ligand Py3F in the first coordination sphere according to IR spectroscopy data. Acetate ion is a counter-anion and is placed in the second coordination sphere as [(Py3F)MnTAP(4-t-BuC6H4)8]þAcO. UV-visible spectroscopy data do not contradict the idea of axial coordination of fullerene-containing N-base by (tetraazaporphyrinato) manganese(III). In our work,31 we have studied the coordination of imidazole (Im) with the compound 1. Manganese(III) complex 1 was found to react with imidazole with the formation of 1:1 complexe in a one-step reversible process. The addition of imidazole to the solution of (AcP)MnTAP(4-t-BuC6H4)8 in toluene induces a bathochromic shift of the Q-band by 2 nm whereas the interaction of complex 1 with Py3F is accompanied by a hypsochromic shift. According to the data,32 analogous reaction of (AcO)MnOPTAP (OPTAPe2,3,7,8,12,13,17,18-octaphenyltetraazaporphyrin dianion) and tetrahydrofuran in toluene is attended by a hypsochromic shift (by 6 nm) of the long-wave absorption band in comparison with the corresponding band of the initial manganese complex as in the case with Py3F. Taking into account the data,31,32 it can be argued that the various band shift directions in the cases of axial complex formation with tetrahydrofuran/Py3F (p-acceptors) and with Im (p-donor) are explained by the presence of dative p-electron MneN interactions and their absence, respectively. This is caused by a combination of
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electronic effects of coordination and functional substitution. Eight electron-withdrawing phenyl groups in (AcO)MnOPTAP promote the formation of the dative p-bonds O/Mn in the axial complex with tetrahydrofuran. Whereas the 4-t-BuC6H4 substituents in complex 1 and Im as the axial ligand exhibit mutually compensative electron-donor properties in the reaction of (AcO)MnTAP(4-tBuC6H4)8 with Im. Using experimental (electronic spectroscopy)33 and theoreti34 cal methods, a frontier orbital diagram was constructed for tetraazazporphyrin iron(III) complexes, and the absorption bands in their electronic spectra were assigned: the Q-band was attributed to charge transfer from the a1 orbital to dp (dp stands for dxz and dyz orbitals) and the B-band, to electronic transition a1/d2z . Variations in the UVevis spectrum of complex 1 upon addition of Py3F may be interpreted on the basis of the above assignment of absorption bands and known analogy between manganese(III) and iron(III) complexes. The dxz, dyz orbitals participate in transmission of an opposite p-effect from the manganese atom and macroring to the fullerene molecule, which stabilizes the dp and a1 orbitals. A hypsochromic shift of Q-band is explained by the smaller change in the energy of the molecular orbital (a1) from which electron transition a1/dp is realized (Fig. 7). The reduction in intensity of the Q-band is related to the opposite direction of the p-effect Py3F)Mn. The energy of orbitals involved in other electronic transitions in the optical range change to a considerably lesser extent.
Fig. 7. Shifts of absorption bands in the UVevis spectra of (AcP)MnTAP(4-t-BuC6H4)8 upon addition of 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino [30 ,40 :1,2][60]-fullerene molecule.
Dyad 3 formation was confirmed by 1H NMR spectroscopy as one of the main methods for molecular structure analysis of porphyrins and their complexes.28,35,36 The 1H NMR spectrum of 1 obtained in CDC13 at 298 K is shown in Fig. 8a. Due to manganese paramagnetism, the phenyl proton resonances are shifted and broadened as compared to 1H NMR spectra of diamagnetic analogues.29 The signals of the o-protons are shifted upfield to 3.82 and 2.85 ppm. The m-proton resonances are shifted downfield to 8.0 and 7.31 ppm. The signal of tert-butyl group protons is located at about 2.0 ppm as expected. Meta-, ortho- and para-proton resonances of the pyridyl substituents in Py3F spectrum appear in the range of 9.08e7.17 ppm (Fig. 8b). The signals of the methine group protons are observed as two doublets at 4.36 and 4.17 ppm while that for the methylene group protons appears as a singlet with a chemical shift at 5.94 ppm. The 1H NMR spectrum of the compound 3 is shown in Fig. 8c. The intense signal for the tert-butyl groups with a chemical shift at 2.08 ppm in the spectrum of initial manganese complex 1 shifts in the field of 0e1.8 ppm in the spectrum of the dyad. This evidences about the change in the deshielding degree of t-Bu protons in the porphyrin/fullerene dyad under the influence of the coordinated molecule of Py3F, i.e. about a redistribution of electron density in the supramolecule. Taking into account the kinetic and physicochemical data, the reaction of (acetato)(octakis(4-tert-butyl-phenyl)tetraazaporphyrinato)manganese(III) with 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3pyridylmethyl)pyrrolidino-[30 ,40 :1,2][60]-fullerene can be
Fig. 8. 1H NMR spectra of compounds (a) 1, (b) 2 and (c) 3 in CDCl3.
interpreted as a two-stage process of donor-acceptor interaction limited by irreversible displacement of the bidentate coordinated acetate ion in (AcO)(Py3F)MnTAP(4-t-BuC6H4)8 (Fig. 9) into the second coordination sphere:
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E.N. Ovchenkova et al. / Tetrahedron xxx (2015) 1e6
Fig. 9. Chemical structure of (AcO)(Py3F)MnTAP(4-t-BuC6H4)8. The similar donoreacceptor complexes structures optimized by quantum-chemical method have been presented earlier.11,37
fast
ðAcOÞMnTAPð4 tBuC6 H4 Þ8 þ Py3 F! ðAcOÞðPy3 FÞMnTAPð4 tBuC6 H4 Þ8
(3)
k
ðAcOÞðPy3 FÞMnTAPð4 tBuC6 H4 Þ8 / þ ðPy3 FÞMnTAPð4 tBuC6 H4 Þ8 AcO
(4)
Obviously, the monomolecular reaction (4) is to be of zero order with respect to Py3F. However, the mixture of Py3F with toluene is a medium with a basicity that is as stronger as concentration of Py3F is higher. That’s why, its action induces a difficulty in displacement of AcO from the first coordination sphere and results in the apparent first negative order of the reaction (1) with respect to the base. 3. Conclusion We have described the formation of donoreacceptor Mn(III) tetraazaporphyrin/C60-pyridyl supramolecular system 3 from tetraazaporphyrin complex manganese(III) 1 and 20 -(4-pyridyl)-50 -(2pyridyl)-10 -(3-pyridylmethyl)pyrrolidino[30 ,40 :1,2][60]fullerene 2. The kinetics of dyad formation in toluene were studied spectrophotometrically at 298 K and the rate constant k¼(2.500.26).108 mol L1 s1 was determined. The inverse dependence of the reaction rate on the fullerene concentration connected with the features of the stoichiometric reaction mechanism and with medium effects was observed. Identification of the dyad 3 [(Py3F)MnTAP(4-t-BuC6H4)8]þAcO as an outer-sphere acetate complex of a donoreacceptor dyad was confirmed by UV-visible, IR and 1H NMR spectroscopy. On the basis of self-assembly properties of the obtained porphyrin/fullerene dyad and taking into account prospects of porphyrin/fullerene supramolecular systems as components for photoactive materials28,38 and synergistic antimicrobial compositions,29,39e41 we envisage future applications of data obtained in our work in photovoltaics and biomedicine. The equation of the Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system formation rate (Eq. 2) can be used for compilation of the technological tetraazaporphyrin/fullerene dyad synthesis regulations.
5
2.9 mmol) and Mn(OAc)2$4H2O (0.9 g, 3.5 mmol) in 2dimethylaminoethanol (7 ml) was heated gradually with stirring to 150 C and the temperature was maintained for 10 h. Completion of the reaction was monitored by TLC, until no traces of starting material were detected. The reaction mixture was cooled, poured into methanol (50 ml) and the precipitate was centrifuged. For purification, the product was dissolved in chloroform (10 ml) and an equal amount of methanol (10 ml) was added to the solution. Chloroform was partially removed from the obtained solution using a rotary evaporator, and the precipitate formed was filtered off, purified by flash chromatography (silica gel/CHCl3e1% CH3OH) and dried under vacuum (60 C, 24 h). Yield: 0.52 g (0.35 mmol, 48%). UVevis (toluene) lmax nm (log ε): 421 (4.51), 494 (4.50), 619 sh, 673 (4.74). IR (KBr) nmax cm1: 2962, 2905, 2868, 1717, 1609, 1384, 1364, 1299, 1269, 1197, 1147, 1109, 997, 891, 850, 839, 811, 751, 635, 599, 585, 563. IR (CsBr) nmax cm1: 508, 479, 406, 362, 299. Found: C 78.82, H 7.47, N 7.31%. C98H107N8O2Mn requires C 79.32, H 7.27, N 7.55%. MS (MALDI-TOF) m/z: 1423.78 [MnTAP(4-t-BuC6H4)8]þ (calcd. For C96H104N8Mn 1423.0). 20 -(4-pyridyl)-50 -(2-pyridyl)-10 -(3-pyridylmethyl)pyrrolidino [30 ,40 :1,2][60]fullerene Py3F was provided by Dr Troshin P. A. and was synthesized by reaction of fullerene C60 with azomethinylid in 1,2-dichlorobenzene.42 UVevis (toluene) lmax nm (log ε): 294, 313, 433 (3.82) nm. IR (KBr) nmax cm1: 1721, 1689, 1636, 1587, 1572, 1455, 1426, 1377, 1356, 1307, 1279, 1231, 1215, 1187, 1157, 1123, 1096, 1064, 1048, 1026, 996, 962, 876, 845, 824, 799, 748, 711, 672, 627, 599, 574, 548, 527, 481, 399. 1H NMR (400 MHz; d, ppm; CDCl3): 9.08 (d, J¼4.7 Hz, 1H), 8.87e8.82 (m, 3H), 8.53e8.50 (m, 2H), 8.04e8.00 (m, 1H), 7.83e7.80 (m, 2H), 7.47e7.45 (m, 2H), 7.20e7.19 (m, 1H), 5.94 (s, 2H), 4.36 (d, J¼15.1 Hz, 1H), 4.17 (d, J¼15.3 Hz, 1H). 4.2. Spectroscopy The UVevis spectra were measured on Agilent 8453 UV-visible spectrophotometers; IR and 1H NMR spectra were recorded on VERTEX 80v and Bruker Avance III-500 NMR spectrometers, respectively; elemental analysis was performed on Euro EA 3000; mass spectra was performed on Bruker Autoflex; all 1H NMR measurements were carried out at room temperature in deuterochloroform (CDCl3). 4.3. Kinetics
4. Experimental section
The kinetics of the reaction between (AcP)MnTAP(4-t-BuC6H4)8 and Py3F in toluene was studied spectrophotometrically over a wide range of concentrations of Py3F (0e5.44 105 M) at 298 K by excess concentrations method. The upper concentration limit of fullerene 2 is determined by solubility of the latter in toluene. The solutions of 1 and 2 in freshly distilled toluene were prepared directly before use in order to avoid the formation of peroxides in the solvent. The optical density measurements on the wavelength of 673 nm for compound 1 solution series at constant concentration of 1 (5.31106 M) with different additions of the base 2 were carried out immediately after mixing of the reagents. Since Py3F absorbs in this range, the spectra of the Mn(III)tetraazaporphyrin/C60-pyridyl supramolecular system were monitored in subtraction mode using the spectrum of the base 2 of the same concentration as in the stock solution as a zero line. The solutions were thermostatted at 298 K in a closed quartz cuvette in the special spectrophotometer cell. The temperature control accuracy was 0.1 K.
4.1. Synthesis
Acknowledgements
(Octakis(4-tert-butyl-phenyl)tetraazaporphyrinato) manganese(III) acetate (AcP)MnTAP(4-t-BuC6H4)8 was synthesized as follows. A mixture of bis(4-tert-butylphenyl)fumaronitrile (1 g,
We appreciate Prof. Klyuev M. V assistance in choice of fullerene derivative. This work was carried out with the help of the centre of the scientific equipment collective use ‘The upper Volga region
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