1,2,3-Triazole aromatic oligomers are driven by intramolecular three-center C-H center dot center dot center dot O hydrogen bonding to form folded or helical secondary structures. This paper reports the assessment of their ability to form intermolecular C-H center dot center dot center dot Cl- in CDCl3 or C-H center dot center dot center dot N hydrogen bonding in CD2Cl2 by using H-1 NMR. It is revealed that the two kinds of intramolecular six-membered C-H center dot center dot center dot O hydrogen bondings of the backbones are both weakened by Cl- through the formation of intermolecular C-H center dot center dot center dot Cl- hydrogen bonding. In the presence of excess of Cl-, the C-H center dot center dot center dot O hydrogen bonding on the N-1 side of the triazole units is, to a large extent, broken by intermolecular C-H center dot center dot center dot Cl- hydrogen bonding, which induces the backbones to form another kind of more extended crescent secondary structures. Under similar conditions, excess of Br- and I- can also form similar intermolecular hydrogen bonding. It is also found that the inside-located N-2 and N-3 atoms of the triazole units of a 8-mer oligomer can also form weak intermolecular C-H center dot center dot center dot N hydrogen bonding with C-H atoms of the alkynyl units of several tri- and bi-alkynes, which is enhanced by the folded conformation of the oligomer through forcing the N-2 and N-3 atoms to arrange into a ring.
[1]Chinese Acad Sci, Shanghai Inst Organ Chem, Key Lab Synthet & Self Assembly Chem Organ Funct, Shanghai 200032, Peoples R China;
[2]Fudan Univ, Dept Chem, Shanghai 200433, Peoples R China
(8.0+极速模式)