Spectroscopic and Theoretical Investigations on Effective and Selective Interaction of Fullerenes C₆₀ and C₇₀ with a Derivatized Zn−phthalocyanine: Stabilization of Charge-Recombined State by Side-On Approach of C₇₀

Abstract

The photophysical aspects of noncovalently linked fullerenes C(60) and C(70) with a designed metallophthalocyanine, namely, zinc-2,3,9,10,16,17,23,24-octakis-(octyloxy)-29H,31H-phthalocyanine (1) have been investigated employing various spectroscopic tools such as UV-vis absorption spectrophotometry, steady state and time-resolved fluorescence, along with solution state IR measurements in toluene medium. The ground state interaction between fullerenes and 1 is first evidenced from UV-vis measurements. Binding constants (K) for the complexes of C(60) and C(70) with 1 are determined to be 13,235 and 27,670 dm(3) x mol(-1), respectively. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 1 in presence of both C(60) and C(70). Emission studies reveal K values of 8945 and 19,175 dm(3) x mol(-1) for C(60)/1 and C(70)/1 complexes, respectively. The magnitude of K suggests that 1 preferentially binds C(70) in comparison to C(60) as average selectivity in K of C(70) over C(60) is enumerated to be 2.0. Time resolved emission measurements establish that C(70)/1 complex is stabilized much more in comparison to C(60)/1 complex in terms of charge recombination. Liquid IR studies provide very good support in favor of ground state complexation between fullerenes and 1. Molecular mechanics calculations at force field model and semiempirical calculations employing third parametric method substantiate the strong binding between C(70) and 1, and at the same time, determine the orientation of bound guest (here C(70)) within the cavity of 1.

„Zwerge“ aus dem Minilabor

“…The resulting difference spectra corresponded to pure fullerenes without any notable additional bands (Figure 3b) 29,30. Therefore, we can conclude that receptors 1 and 2 lack significant ground state interaction with fullerenes, similar to previously investigated noncovalent ensembles 21,31…”

Photophysical and theoretical insights on non-covalently linked fullerene–zinc phthalocyanine complexes

“…The study on non-covalently linked fullerene-phthalocyanine composite, however, is rare. In recent past, our research group substantiates the role of electrostatic interaction in fullerene-Pc non-covalent assembly by choosing very simple unsubstituted free-base, i.e., H 2 -and ZnPc molecules [55,56]. The fullerene-Pc non-covalent interaction is also validated in terms of a C 60 derivative, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate with H 2 -and Zn-Pc molecules [57].…”

Modern Synthetic Approaches to Phthalonitriles with Special Emphasis on Transition-Metal Catalyzed Cyanation Reactions

“…Phthalocyanines, prepared from 2b are expected to have mesogenic properties, [11] as well as act as receptors for polyaromatic substrates and fullerenes. [49] Cyanation of dibromide 3c, bearing 2-(2'-ethoxy)ethoxyl groups, was also performed under anaerobic conditions. Dibromide 3c was directly mixed with Pd 2 (dba) 3 , dppf and required amount of Zn(CN) 2 , reaction mixture was flushed with Ar, DMAA was added, and mixture heated to 120 °C, which afforded dinitrile 3d in 80 % yield ( Figure 15).…”