Beilstein J. Org. Chem.2018,14, 1704–1722, doi:10.3762/bjoc.14.145
solution, for example, asymmetric vs propeller (C3-symmetric) [30][36][45][46], “dendritic choreography” [47], “open-gates closed-gates” frontier rotamerism [31] and “in out” axial chirality [33].
In addition, in the targeted G-2 dendrimers (Figure 1), different connections of branches around the core
solution, the reaction conditions were found mandatory to the high solvation of the G-0 and G-1 dendrons exhibiting a major (anti–anti) (parallel) rotamerism of the peripheral 4-(n-octyloxy)phenyl units about the C(s-triazine)–N(exocyclic) partial double bonds. The final iterative synthetic step was
. The structural variety of the covalent dendritic elaboration around the m-trivalent cores (1,4-phenylene over piperazin-1,4-diyl adjacent linkers, propeller over asymmetric rotamerism of the angular over linear connectivity) modulated the degree of nano-aggregation.
Experimental
General
All reagents
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Graphical Abstract
Figure 1:
The key elements for design and construction of the targeted G-2 dendrimers.
Beilstein J. Org. Chem.2015,11, 2105–2116, doi:10.3762/bjoc.11.227
; hydrogen bonding; NMR; rotamerism; supramolecular chemistry; Introduction
The hydrogen bond (HB) is one of the most common non-covalent interactions. Since it stabilizes, for example, the double helix of DNA and influences peptide folding it is quite reasonable to assume that HBing is crucial for
interactions [41] that act diagonally between neighbouring hydrogen bonding sites.
The breakage of single intramolecular hydrogen bonding upon association leading to rotamerism was our motivation to search for more complex systems than previously reported [2][9][10]. Since the amide group is common in
) separate curves overlap. One of these exhibits a decrease of the chemical shift in the beginning of titration with relatively small CIS value and reaches its plateau relatively fast. The said decrease of the chemical shift may only be caused by the rotamerism and change of intra- to intermolecular hydrogen
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Graphical Abstract
Figure 1:
The compounds used in this study and their atom numbering.