ABSTRACT
Through a cycloaddition reaction, fullerene (C60) was derivatized with a novel organic compound 5-(benzo[b]thiophen-3-yl)pyridine-3-carbaldehyde to form the processable and stable 3-(benzo[b]thiophene-3yl)-5-fullero-1-methylpyrrolidinepyridine (BTFP) compound. BTFP exhibits close similarities to phenyl-C61-butyric-acid-methyl-ester (PCBM) in terms of first reduction potential values (-0.62 and -0.61â V vs. Ag/AgCl, for BTFP and PCBM, respectively) and lowest occupied molecular orbital (LUMO) energy level values (3.93â eV in both cases). In chloroform, BTFP exhibits a bathochromic shift in the λmax of BTFP (λmax,BTFP=290â nm and λmax,PCBM=260â nm), owing to the grafted benzo[b]thiophene-3-yl)pyridine moiety. Despite the similarity in LUMO (3.93â eV) energy values, BTFP and PCBM differ in their luminescence-quenching ability. The bathochromic shift in the λmax of BTFP (relative to PCMB) is likely to contribute to improved light absorption of a suitable donor for photovoltaic applications.
ABSTRACT
The synthesis of a new class of robust squaraine dyes, colloquially named 1,2-hemisquarimines (1,2-HSQiMs), through the microwave-assisted condensation of aniline derivatives with the 1,2-squaraine core is reported. In CH3CN, 1,2-HSQiMs show a broad absorption band with a high extinction coefficient and a maximum at around λ=530â nm, as well as an emission band centered at about λ=574â nm, that are pH dependent. Protonation of the imine nitrogen causes a redshift of both absorption and emission maxima, with a concomitant increase in the lifetime of the emitting excited state. Encapsulation of the chromophore into a cucurbit[7]uril host revealed fluorescence enhancement and increased photostability in water. The redox characteristics of 1,2-HSQiMs indicate that charge injection into TiO2 is possible; this opens up promising perspectives for their use as photosensitizers for solar energy conversion.
