Molecular Binding Behaviors of Pyromellitic and Naphthalene Diimide Derivatives by Tetrasulfonated 1,5-Dinaphtho-(3n+8)-crown-n (n=8, 10) in Aqueous Solution

The highly affinitive and selective binding processes of tetrasulfonated 1,5-dinaphtho-38-crown-10 (1(4-)) and tetrasulfonated 1,5-dinaphtho-32-crown-8 (2(4-)) with pyromellitic diimide and naphthalene diimide derivatives bearing cationic terminal groups (PMDI2+ and NDI2+) are comprehensively investigated in aqueous solution by H-1 NMR and UV/vis experiments, mass spectrometry, microcalorimetric titration, and crystallographic analysis. The binding process of host-guest complexation is thermodynamically driven by the large enthalpic gain and favorable entropic change with the high association constants in the range of 10(4)-10(6) M-1 order of magnitude. Combined with our previously reported thermodynamic data of ethyl viologen (EV2+), it is found that the exclusively selective binding behaviors originate from the size/shape matching effect, as well as the electrostatic interaction between negatively charged hosts and positively charged guests and aromatic pi-stacking interrelation between electron-rich donors and electron-deficient acceptors.