Unifying Principles of the Reductive Covalent Graphene Functionalization

Abstract

Covalently functionalized graphene derivatives were synthesized via benchmark reductive routes using graphite intercalation compounds (GICs), in particular KC. We have compared the graphene arylation and alkylation of the GIC using 4-tert-butylphenyldiazonium and bis(4-(tert-butyl)phenyl)iodonium salts, as well as phenyl iodide, n-hexyl iodide, and n-dodecyl iodide, as electrophiles in model reactions. We have put a particular focus on the evaluation of the degree of addition and the bulk functionalization homogeneity (H). For this purpose, we have employed statistical Raman spectroscopy (SRS), and a forefront characterization tool using thermogravimetric analysis coupled with FT-IR, gas chromatography, and mass spectrometry (TGA/FT-IR/GC/MS). The present study unambiguously shows that the graphene functionalization using alkyl iodides leads to the best results, in terms of both the degree of addition and the H. Moreover, we have identified the reversible character of the covalent addition chemistry, even at temperatures below 200 °C. The thermally induced addend cleavage proceeds homolytically, which allows for the detection of dimeric cleavage products by TGA/FT-IR/GC/MS. This dimerization points to a certain degree of regioselectivity, leading to a low sheet homogeneity (H). Finally, we developed this concept by performing the reductive alkylation reaction in monolayer CVD graphene films. This work provides important insights into the understanding of basic principles of reductive graphene functionalization and will serve as a guide in the design of new graphene functionalization concepts.

Controlling the Degree of Functionalization: In‐Depth Quantification and Side‐Product Analysis of Diazonium Chemistry on SWCNTs

“…As seen in Figure 2, the TGA spectra of three chosen SWCNT-PhI samples are identical until 150 8C. [13a, 15] Alternatively, the high mass loss temperature and the toluene peak are an indicator for lattice decomposition, which has been previously reportedf or graphene [14] and SWCNTs. At even highert emperatures (> 400 8C), no indication for ad ifference in the samples can be found, as the TGA curvesare parallel in that region.…”

Gitteröffnung durch reduktive kovalente Volumen‐Funktionalisierung von schwarzem Phosphor

“…[30] Zusammenfassend resultiert die reduktive kovalente Funktionalisierung von BP mit Alkylhalogeniden unter Ver-Abbildung 3. Dies steht im Gegensatz zur neutralen Reaktionsroute (Abbildung SI 22).…”

Highly Regioselective Alkylation of Hexabenzocoronenes: Fundamental Insights into the Covalent Chemistry of Graphene

“…Thef irst step in the reaction between the HBC-dianion and alkyl iodide is aSET from the HBC dianion to the alkyl iodide.T his fast process has been reported in the chemistry of fullerenes, [32] carbon nanotubes, [33][34][35][36][37][38] and particularly for the reductive alkylation and arylation of graphene. [15,21] TheSET is avery fast process which leads to the anion radical of the corresponding alkyl iodide and subsequently releases an iodide,w hile the simultaneously formed alkyl radical RC attacks ac arbon atom of the HBC anion radical just generated. DFT calculations of the corresponding reaction coordinate show that this process is highly exergonic and has virtually no activation barrier.…”

“…[12][13][14][15][16][17][18][19][20][21] This reductive approach allows the generation of alarge variety of covalent adducts,including alkylated, arylated, and hydrogenated graphene derivatives, which exhibit comparatively high degrees of addition. Together with the reductive bulk functionalization, the addition chemistry of graphenides deposited on surfaces [18][19][20][21] has been investigated. Thek ey point is the use of negatively charged graphites,t he so called graphite intercalation compounds (GICs), as starting materials.InGICs,alkaline metals, such as potassium, are placed between the individual carbon sheets and the graphene layers are reductively activated by electron transfer from the metal intercalates.Ageneral feature of reductive graphene functionalization protocols seems to be an inhomogeneous distribution of addends on the surface and leads to the formation of islands of highly functionalized areas next to intact nanographenes.T his distribution has been demonstrated, for example,b yh ighresolution transmission-electron microscopy (HRTEM) of polyarylated graphene, [11] and fluorescence spectroscopy of hydrogenated graphene.…”

“…[12][13][14][15][16][17][18][19][20][21] This reductive approach allows the generation of alarge variety of covalent adducts,including alkylated, arylated, and hydrogenated graphene derivatives, which exhibit comparatively high degrees of addition. Together with the reductive bulk functionalization, the addition chemistry of graphenides deposited on surfaces [18][19][20][21] has been investigated.…”