Domino reaction for the controlled functionalization of sp2 carbon allotropes

Graphene and graphene related materials are a hot research topic in the material science and are becoming a reality of increasing importance in many application fields. Indeed, graphene has high charge-carrier mobilities, in-plane thermal conductivity and very high elastic modulus. It is increasingly acknowledged that application of carbon nanomaterials such as graphene has to be assisted by functionalization, which allows to tune electronic and solubility properties, phaseforming and self-assembly behaviour. In this work, functionalization of graphene layers was performed with 2-(2,5- dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) [3]. SP is a serinol derivative obtained from the neat reaction of 2-amino-1,3- propandiol with 2,5-hexanedione, with atom economy of about 85%, almost quantitative yield and thus high atom efficiency, the only byproduct being water, in the absence of solvent and catalyst [1, 2, 3]. Functionalization was obtained by simply mixing nanosized high surface area graphite with SP, giving either mechanical or thermal energy. Very high functionalization yield was found, larger than 90% and even almost quantitative. Few layers graphene were isolated from stable water suspensions. Reaction of SP was applied to other sp2 carbon allotropes, such as carbon nanotubes and carbon black. Many different applications were developed: from conductive inks to carbon papers and aerogels. The reaction occurring between SP and graphene layers was investigated. Adducts of a high surface area nanosized graphite were prepared with a model molecule, 1,2,5-trimethyl-1H-pyrrole (TMP). Pristine TMP, HSAG, products formed by the reaction and HSAG-TMP adducts were studied by means of Fourier transformed infrared spectroscopy (FT-IR), 1H-NMR and thermogravimetric analysis. DFT modelling was carried out to predict IR spectra of HSAG-TMP reaction products and adducts. Reaction pathway is presented. Domino reaction appears to occur: carbocatalyzed oxidation of the pyrrole compound lead to the formation of activated double bond, able to give rise cycloaddition with the graphitic substrate. Such a facile and sustainable functionalization method allows the controlled introduction of functional groups on graphitic substrate without appreciably altering their structure.