NMR data for isolated organic compounds

Benzenediazonium tetrafluoroborate: Prepared according to the general procedure.

1_{H NMR (300.1 MHz, DMSO-d}

6, δ ppm): 8.67 (d, J = 8.0 Hz, 2H), 8.26 (t, J = 7.7 Hz, 1H), 7.99

(t, J = 7.4 Hz, 2H).

1-phenylnaphthalene: Prepared according to the general procedure.

1_{H NMR (300.1 MHz, DMSO-d}

6, δ ppm): 8.95 (d, J = 8.4 Hz, 1H), 8.50 (d, J = 8.1 Hz, 1H), 8.20 (t,

J = 8.3 Hz, 1H), 8.09 (t, J = 8.1 Hz, 1H), 7.78 (m, 3H), 7.49 (m, 3H), 7.40 (m, 2H).

1-phenylanthracene: Prepared according to the general procedure.

1_{H NMR (300.1 MHz, DMSO-d}

6, δ ppm): 8.61 (m, 1H), 8.31 (d, J = 8.1 Hz, 1H), 8.12 (t, J = 8.3 Hz, 1H), 8.09 (t, J = 8.1 Hz, 1H), 7.95 (m, 1H), 7.79 (t, J = 8.1 Hz, 2H), 7.55 (m, 3H), 7.43 (m, 4H).

1-phenylpyrene: Prepared according to the general procedure.

1_{H NMR (300.1 MHz, DMSO-d}

6, δ ppm): 8.51 (d, J = 8.4 Hz, 1H), 8.29 (d, J = 8.1 Hz, 1H), 8.14 (m, 1H), 8.06 (m, 4H), 7.94 (d, J = 8.2 Hz, 1H), 7.74 (m, 3H), 7.43 (m, 3H).

5.4 Conclusions

The covalent functionalization of graphene acid with Fc has been accomplished employing the carbodiimide chemistry. Graphene oxide was also tested in the same experimental conditions as standard oxidized graphenic benchmark for comparison. While the functionalization was confirmed by several independent techniques, the quite precise surface chemistry of the GA, which selectively exposes a high density of carboxylic groups on the basal plane, yielded a higher functionalization degree (3.9 at.% of Fe) of mainly pure Fe(II) ferrocene. On the contrary, the functionalization efficiency on standard graphene oxide was poorer, (0.8 at.% of Fe), probably because of the presence of a wide gamut of surface oxygen species with a variable chemical reactivity, thus limiting the control over functionalization.

Both Fc-modified materials were found to be active and easily recyclable catalysts in the C-H insertion reaction of benzenediazonium tetrafluoroborate on naphthalene. Notably, GA-PDA-Fc sample catalyzed the production of the same amount of 1-phenylnaphthalene as compared to molecular ferrocene, which means that all the iron centers covalently attached on the GA surface behave as active sites. Furthermore, both heterogenized catalysts presented an extended scope, being able to catalyze the C-H insertion using anthracene and pyrene as substrates. In every reaction, the GA-based catalyst achieved a higher production of the insertion product compared to the GO-based sample. The well-defined structure of GA with precise functionalities and higher aromatic content, allowing efficient adsorption of the reagents close to the active centers combined with superior electron conductivity, are likely responsible for the higher catalytic activity than that of the GO analogue.

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