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A series of substituted para-,meta- and ortho-nitrophenyl derivatives of fulleropyrrolidine were synthesized to investigate the effects of the position of substitution on electronic properties by using steady-state absorption and fluorescence spectra,combined with DFT calculations.The results confirmed that the position of substitution has little effect on absorption and fluorescence spectra,whereas a significant effect was observed on their LUMO energy levels.The theoretical calculations revealed that the LUMO energy of the ortho-nitrophenyl substituted derivative was increased 0.1 eV above those of para- and meta-substitution.The prominent effect of ortho-substitution was attributed to the through-space orbital interaction between spatially closed electron-withdrawing nitro group and fullerene cage.These findings could provide fundamental insights in raising LUMO levels of C_(60)-based electron acceptor materials and an alternative strategy to increase open circuit voltage V_(oc) in polymer solar cells.
A series of substituted para-, meta- and ortho-nitrophenyl derivatives of fulleropyrrolidine were synthesized to investigate the effects of the position of substitution on electronic properties by using steady-state absorption and fluorescence spectra, combined with DFT calculations. Results that the that the position of substitution has little effect on absorption and fluorescence spectra, a significant effect was observed on their LUMO energy levels. the theoretical calculations revealed that the LUMO energy of the ortho-nitrophenyl substituted derivative was increased 0.1 eV above those of para- and meta -substitution.The prominent effect of ortho-substitution was attributed to the through-space orbital interaction between spatially closed electron-withdrawing nitro group and fullerene cage.These findings could provide fundamental insights in raising LUMO levels of C_ (60) -based electron acceptor materials and an alternative strategy to increase open circuit voltage V oc (oc) in polymer solar cells.