The Isoindazole Nucleus as a Donor in Fullerene-Based Dyads. Evidence for Electron Transfer

A series of isoindazole-C60 dyads 4a−c based on pyrazolino[60]fullerene have been prepared by 1,3-dipolar cycloadditions of the nitrile imines, generated in situ from hydrazones 3a−c, to C60. Molecular orbital calculations for 4b revealed that the electron distribution of the HOMO is located on the...

Full description

Saved in:
Bibliographic Details
Published in:Journal of organic chemistry 2004-04, Vol.69 (8), p.2661-2668
Main Authors: Delgado, Juan L, de la Cruz, Pilar, López-Arza, Vicente, Langa, Fernando, Kimball, David B, Haley, Michael M, Araki, Yasuyuki, Ito, Osamu
Format: Article
Language:English
Subjects:
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Fullerenes and related materials
diamonds, graphite
Materials science
Physics
Specific materials
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A series of isoindazole-C60 dyads 4a−c based on pyrazolino[60]fullerene have been prepared by 1,3-dipolar cycloadditions of the nitrile imines, generated in situ from hydrazones 3a−c, to C60. Molecular orbital calculations for 4b revealed that the electron distribution of the HOMO is located on the isoindazole moiety, while the electron distribution of the LUMO is located on the C60 moiety. Electrochemical properties of the new dyads 4a−c show a similar electron affinity with respect to C60. Charge-transfer interactions in the ground state between the isoindazole ring and the fullerene cage are predicted by the molecular orbital calculations and confirmed by electrochemical studies in 4a,b. Steady-state fluorescence emission spectra of dyads 4a−c show that fluorescence intensities in polar benzonitrile solvent decrease with increasing electron-donating ability of the substituent attached on the isoindazole group. This was confirmed by the shortening of fluorescence lifetimes, from which intramolecular charge-separation rates and efficiencies via the excited singlet states of the fullerene moiety were evaluated. The yields of the triplet states in polar solvent decrease with the electron-donating ability, supporting the competitive formation of the charge-separated state with the intersystem crossing from the excited states. Thus, isoindazole[60]fullerene 4b can be considered a molecular switch with an AND logic gate.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo0499017