The impact of metal coordination on the assembly of bis(indolyl)methane-naphthalene-diimide amphiphiles

Abstract

The self-assembly and coordination of amphiphiles comprised of naphthalenediimide (NDI) and bis(indolyl)methane (BIM) chromophores were investigated as a function of pH and metal. As observed by TEM, SEM and AFM imaging, the self-assembly of NDI-BIM 1 produced irregular nanostructures at neutral pH in CH₃CN–H₂O (1 : 1); whereas, well-defined nanotubes were observed at pH 2. Conversely, Fmoc-protected, NDI-BIM 2 formed nanotubes at neutral pH and nonspecific aggregates at pH 2. Upon coordination of Cu²⁺ ions to the bis(indoyl)methane moiety, a reorganization from nanotubes to vesicular structures was observed.