Dynamic behavior of ammonium ion in the crown ether cavity within Ni(dmit)2 salt as studied by solid-state NMR

In the integrated molecular systems of the crown ether-based ionic channel and the electronic conducting column of Ni(dmit)2, an interaction is expected between the dynamic motion of ions in the crown ether channel and the electronic state of the conducting column. To investigate an ability of the crown ether molecule for providing the environment suitable for the ionic motion, the dynamic behavior of the ammonium ion of semiconducting [(NH4+)(18-crown-6)][Ni(dmit)2]3 was studied by the solid state D NMR and 15N CP NMR. The D NMR spectrum of deuterated analogue of [(ND4+)(18-crown-6)][Ni(dmit)2]3 indicated that the ND4+ ion rotated rapidly with jumping rate more than the order of 106 Hz above room temperature. The quadrupole coupling of e2Qq/h=6.5 kHz remained even at 360 K for deuterium atom of ND4+ ion. The anisotropic tensor of 15N chemical shift, the principal values of which were σ11=−356.0 ppm, σ22=−353.2 ppm and σ33=−342.6 ppm, was found. These results suggest that the rotating ammonium ion is slightly deformed in the cavity of 18-crown-6.