Design, synthesis and structure of novel dendritic G-2 melamines comprising piperidine motifs as key linkers and 4-(n-octyloxy)aniline as a peripheral unit
Abstract
Starting from 4-amino-1-(tert-butoxycarbonyl)piperidine (Boc-PD-NH2), we report the synthesis of three novel meta-tri- and dimeric tetravalent N-substituted melamines with piperidin-4-yl groups. These compounds were used as central building-blocks and successfully incorporated into three new G-2 melamine dendrimers containing 4-(n-octyloxy)aniline as a peripheral unit. From a structural point of view, the challenging reactivity of Boc-PD-NH2 in comparison with 1-Boc-piperazine and cyclohexylamine, as SN2-Ar amination reagents against cyanuric chloride, was interpreted in terms of DFT (Density Functional Theory) thermodynamic and electronic computed data. Two out of the three dendrimers self-assembled in the solid state as large homogeneously packed spherical nano-aggregates (average D values ranging between 2500 and 3200 nm, TEM (Transmission Electron Microscopy) data) as a result of their “shell-to-shell” pre-associations in solution (DMF and 1,4-dioxane), promoted by chiral self-organisation, “round”- or “oval”-vaulted shapes (DFT data).