Luminescent Blooming of Dendronic Carbon Nanotubes through Ion-Pairing Interactions with an EuIII Complex

A multiwalled carbon nanotube (MWCNT) scaffold was covalently functionalized with a second‐generation polyamidoamine (PAMAM) dendron, presenting four terminal amino groups per grafted aryl moiety. These reactive functions were alkylated to obtain a positively charged polycationic dendron/carbon nanotube system (d‐MWCNTs⋅Cl), which eventually underwent anion exchange reaction with a negatively charged and highly luminescent EuIII complex ([EuL4]⋅NEt4, in which L=(2‐naphtoyltrifluoroacetonate)). This process afforded the target material d‐MWCNTs⋅[EuL4], in which MWCNTs are combined with red‐emitting EuIII centers through electrostatic interactions with the dendronic branches. Characterization of the novel MWCNT materials was accomplished by means of TGA and TEM, whereas d‐MWCNTs⋅Cl and d‐MWCNTs⋅ [EuL4] further underwent XPS, SEM and Raman analyses. These studies demonstrate the integrity of the luminescent [EuL4]− center in the luminescent hybrid, the massive load of the cationic binding sites, and the virtually complete anion‐exchange into the final hybrid material. The occurrence of the ion‐pairing interaction with MWCNTs was unambiguously demonstrated through DOSY NMR diffusion studies. Photophysical investigations show that MWCNTs⋅[EuL4] is a highly soluble and brightly luminescent red hybrid material in which MWCNTs act as photochemically inert scaffolds with negligible UV/Vis absorption, compared with the grafted Eu complex, and with no quenching activity. The high dispersibility of MWCNTs⋅[EuL4] in a polymer matrix makes it a promising luminophore for applications in material science. Red light from the dark: Combining a positively charged dendronic carbon nanotube (CNT) and a negatively charged EuIII complex, a unique hybrid material characterized by an intense luminescence has been prepared, proving for the first time that ion‐pairing interactions are a potent supramolecular tool to assemble CNT materials with potentially relevant applicative perspectives (see figure).