New Photophysical Insights in Noncovalent Interaction between Fulleropyrrolidine and a Series of Zincphthalocyanines

Abstract

The present article reports, for the first time, the photophysical aspects of noncovalent interaction of a fullerene derivative, namely, C(60) pyrrolidine tris-acid ethyl ester (PyC(60)) with a series of zincphthalocyanines, for example, underivatized zincphthalocyanine (1), zinc-1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (2), and zinc-2,3,9,10,16,17,23,24-octakis-(octyloxy)-29H,31H-phthalocyanine (3) in toluene. Ground state electronic interaction of PyC(60) with 1, 2 and 3 has been evidenced from the observation of well-defined charge transfer (CT) absorption bands in the visible region. Utilizing the CT transition energy, vertical electron affinity (E(A)(v)) of PyC(60) is determined. Steady state fluorescence experiment enables us to determine the value of binding constant (K) in the magnitude of 2.60 × 10(4) dm(3)·mol(-1), 2.20 × 10(4) dm(3)·mol(-1), and 1.27 × 10(4) dm(3)·mol(-1) for the noncovalent complexes of PyC(60) with 1, 2, and 3, respectively. K values of PyC(60)-ZnPc complexes suggest that PyC(60) is incapable of discriminating between 1, 2, and 3 in solution. Lifetime experiment signifies the importance of static quenching phenomenon for our presently investigated supramolecules and it yields larger magnitude of charge separated rate constant for the PyC(60)-1 species in toluene. Photoinduced energy transfer between PyC(60) and ZnPc derivatives, namely, 1, 2, and 3, in toluene, has been evidenced with nanosecond laser photolysis method by observing the transient absorption bands in the visible region; transient absorption studies establish that energy transfer from (T)PyC(60)* to the ZnPc occurs predominantly, as confirmed by the consecutive appearance of the triplet states of PyC(60). Theoretical calculations at semiempirical level (PM3) evoke the single projection geometric structures for the PyC(60)-ZnPc systems in vacuo, which also proves that interaction between PyC(60) and ZnPc is governed by the electrostatic mechanism rather than dispersive forces associated with π-π interaction.

Complexation of C60 Fullerene with Aromatic Drugs

“…[8] Such molecules feature an overlap area of the aromatic chromophores in the 1:1 hetero-complexes similar to that expected for the ligand-C 60 systems studied in the present work. [10][11][12] These facts provide additional support to the magnitudes of the obtained parameters and justify performing the full analysis of the energetics. [10][11][12] These facts provide additional support to the magnitudes of the obtained parameters and justify performing the full analysis of the energetics.…”

“…One of the main reasons for that might be the utilization of the K F parameter as an adjustable quantity, which may not be correct for the case when the fullerene molecules do not give an explicit contribution to the optical density, and therefore, to the titration curve (as in the present work) [see Eq. [10][11][12] The estimation of K F was accomplished in the present work as follows: To the best of our knowledge, an experimental estimation of the magnitude of K F in aqueous solution accounting for the polydisperse nature of FWS has not been reported in the literature, except the quite extensively published cases of simple 1:1 or 1:2 complexations studied predominantly in organic solvents.…”

Model of Complexation between C60 Fullerenes and Biologically Active Compounds

“…Насколько нам известно, экспериментальная оценка величины KF с учетом полидисперсной природы водного раствора фуллерена не проводилась до сих пор, за исключением довольно подробно рассмотренных случаев простых комплексообразований 1:1 и 1:2, преимущественно в органических растворителях [10,11,21], и результатов исследований, описанных в работе [12]. Оценка KF была выполнена в настоящей работе следующим образом.…”

Quenching of fluorescence in C60 fulleropyrrolidines by chloroform

“…Fluorescence of the fullerene derivatives is effectively quenched by halogenated alkanes such as carbon tetrachloride and chloroform [13,14]. The mechanism of fluorescence quenching involves the formation of charge-transfer (CT) complexes between the electron rich fluorophore and electron deficient quencher [15,16]. Electron transfer and energy transfer processes could be responsible for the fluorescence quenching of the molecules in the presence of chloroform.…”