J. Otsuki et al., A BIS-CROWN ETHER DERIVATIVE OF TRIAMINOTRIAZINE - SYNTHESIS AND BEHAVIOR OF THE ION-SELECTIVE AND HYDROGEN-BONDING RESPONSIVE ROTAMERS, Bulletin of the Chemical Society of Japan, 70(3), 1997, pp. 671-679
A bis-crown ether derivative of triaminotriazine was synthesized via a
phthalic acid derivative of a polyether macrocycle obtained from benz
o-18-crown-6. It exists in different conformers distinguishable by H-1
NMR at room temperature, in which the macrocyclic side-arms take a cl
osed, half-open, or fully open form, due to the rotational barrier of
the C(triazine)-N bond. Large alkali metal ions, such as Rb+ and Cs+,
the latter being particularly effective, promote the formation of the
closed conformer. A barbiturate derivative also causes a similar equil
ibrium shift to the closed form by establishing complementary hydrogen
bonds. The half-open and fully open conformers are induced by smaller
alkali metal ions than Rb+, among which K+ is the most effective.