Reaction of the cage amine adamanzane, 1,5,9,13-tetraazatricyclo-[184.108.40.206,13]docosane, with sodium iodide in 93% sulfuric acid affords the bicyclictetraamine adamanzane, 1,5,9,13-tetraazabicyclo[7.7.3]nonadecane which was isolated as its tetraprotonated bromide salt, [H4adz]Br4 (yield 70%). The structure of the [H4adz]Br4 has been determined by X-ray diffraction techniques at T=120 K; Mr=529.09, monoclinic, P21/n, a=11.300(3), b=12.563(3), c=15.561(6) Å, beta=90.29(3)degrees, Z=4, Dx=1.78 g cm-3, MoKa=0.71073 Å, mu=72.9 cm-1, F(000)=1176, R(F)=0.0734 for 4028 reflections with I>2 sigma(I) and wR(F2)=0.2116 for all 6439 unique reflections. The conformation of the 16-membered ring is best described as a distorted 'rectangular'  conformation. The distance between the bridging nitrogen atoms is 4.983(9) Å, and the distance between the non-bridging atoms is 7.568(10) Å. The four acidic hydrogen atoms are all oriented away from the cavity. The concentration acid dissociation constants of H4adz4+ were determined by potentiometric glass-electrode measurements and 1H and 13C NMR spectroscopy: pKa1=1-2, pKa3=9.65(2) and pKa4=12.09(4) (1 M NaBr, 25 degrees C).
|Journal||Acta Chemica Scandinavica|
|Publication status||Published - 1998|