Synthesis and characterization of C60 and C70 acetylacetone monoadducts and study of their photochemical properties for potential application in solar cells

We report on the synthesis of C60 and C70 monoadducts at room temperature through the Bingel reaction; employing acetylacetone as ligand; in presence of DBU (1,8-Diazabicyclo [5.4.0] undec-7-ene), carbon tetrabromide (CBr4), and o-dichlorobenzene. Diacetylmethane-[C60-Ih]-fullerene-[5,6] and diacetylmethane-[C70-D5h]-fullerene-[5,6] monoadducts were obtained with yields of 69% and 44%, respectively. The products were purified by column chromatography (CC, on silica gel, using hexane, carbon disulfide, and chloroform as eluents at room temperature) and characterized by Nuclear Magnetic Resonance (1H and 13C), Fourier-Transform Infrared (FT-IR) and UV-Visible spectroscopies, Matrix-assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) Mass spectrometry, Cyclic Voltammetry (CV), and Osteryoung Square Wave Voltammetry (OSWV). Both compounds showed irreversible reduction peaks controlled by diffusion, with LUMO energy levels of -3.09 eV, -3.13 eV for C60, and C70 monoadducts, respectively. These values are comparable with the -3.99 eV of PC61BM. The synthetized adducts were incorporated into inverted-type perovskite solar cells and were used as electron transporting materials (ETM) obtaining power conversion efficiencies (PCE) of 8.5% and 14.0% for the C60 and C70 monoadducts, respectively. When C60 is replaced by a lower symmetrical fullerene such as C70 an improved light absorption in the visible region is observed.

Correlation between Yield and Reduced Mass of Raw Materials in Reaction of Fullerene

It turned out that the same regression equation between<br>yield and reduced mass of raw materials holds in<br>cycloaddition, Bingel reaction, and other reactions of<br>fullerene. For the reactions, where the molecular weight of the<br>product exceeds around 1500, reduced mass was obtained<br>from molecular weight adjusted by number of rotatable bonds<br>to show a similar correlation by the regression equation.

Correlation between Yield and Reduced Mass of Raw Materials in Reaction of Fullerene

It turned out that the same regression equation between<br>yield and reduced mass of raw materials holds in<br>cycloaddition, Bingel reaction, and other reactions of<br>fullerene. For the reactions, where the molecular weight of the<br>product exceeds around 1500, reduced mass was obtained<br>from molecular weight adjusted by number of rotatable bonds<br>to show a similar correlation by the regression equation.

Kinetic investigation of the cyclopropanation process of fullerene C60 by halogenmethyl ketones under the conditions of the Bingel reaction

The kinetics of the Bingel reaction with halogenmethyl ketones and C60 fullerene has been studied in streaming mode by sampling the reaction mixture at different time intervals and separating the components using HPLC.

A New Method to prepare an e,e,e Trisadduct of C60 Using a ProtectionDeprotection Sequence

A racemic mixture of the e,e,e Bingel-trisadduct, tris[di(ethoxycarbonyl)methano][60]fullerene 3 was synthesized by malonate additions (Bingel reaction) following by retro Diels-Alder reactions using a C60 tris-e,e,e adduct of anthracene 1 as precursor. Using this approach, the anthracenes act as protective groups and help orient the new additions so that poly-adducts with particular geometries are obtained. From the e,e,e anthracene-trisadduct 1 we also obtained the mono[di(ethoxycarbonyl)methano][60]fullerene 6 and bis [di(ethoxycarbonyl)methano][60]fullerene 7. This approach exhibits a total yield of 4,2 % for the e,e,e tris malonate adduct, gives rise to less complex reaction mixtures and makes it easier to separate and characterize the compounds than other methods. The compounds obtained where characterized by UV/VIS, FT-IR, 1H NMR, and MALDI-TOF.