jo301911w_si_004.cif (45.41 kB)
High Affinity Crown Ether Complexes in Water: Thermodynamic Analysis, Evidence of Crystallography and Binding of NAD+
dataset
posted on 2012-11-02, 00:00 authored by Ling Chen, Heng-Yi Zhang, Yu LiuImproving traditional crown ether to the water-soluble
and high
binding ability host molecule is critical to our efforts to model
or mimic biological supramolecular systems. In this paper, we converted
two traditional crown ethers, 1,5-dinaphtho-32-crown-8 and 1,5-dinaphtho-38-crown-10,
into the water-soluble tetrasulfonated 1,5-dinaphtho-32-crown-8 and
tetrasulfonated 1,5-dinaphtho-38-crown-10, evaluated their complexation
with three dicationic bipyridiniums in aqueous solution by microcalorimetric
titration, UV–vis, and NMR experiments, and then determined
the crystal structures of three tetrasulfonatocrown ether-bipyridinium
complexes. The equilibrium association constants of tetrasulfonated
1,5-dinaphtho-32-crown-8 with these bipyridiniums reach up to 107 M–1, while those of tetrasulfonated 1,5-dinaphtho-38-crown-10
are just in the range of 105 M–1 order
of magnitude. The thermodynamic data obtained show that the complexation
of two tetrasulfonatocrown ethers with dicationic bipyridiniums is
absolutely enthalpy-driven in water with an accompanying little entropic
gain, and each monocationic pyridinium moiety in guest molecules can
provide about −10 to −15 kJ·mol–1 enthalpy contribution irrespective of the size of ether crowns.
Moreover, we also investigated the recognition capability of the two
water-soluble crown ethers with NAD+ and NADH by microcalorimetric
titration and NMR experiments, indicating that tetrasulfonated 1,5-dinaphtho-32-crown-8
shows exclusive selectivity to NAD+. The water-solubility
and high affinity of this system as well as the flexible and non-preorganized
characteristic of these crown ethers make it suitable to serve as
a model for mimicking biological systems.