Preferred hydrogen bonding site of 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane (TATU) to hydroquinone

The structure of 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane (TATU) (2), recently deduced from NMR measurements, is confirmed by single crystal X-ray diffraction of its adduct with hydroquinone. The crystals are orthorhombic, space group Pnma, with a = 7.585(1) Å, b = 16.065(3) Å, c = 10.837(2) Å, V = 1320.5(4) Å3, Z = 4, F(0 0 0) = 568, R1 = 3.93%, wR2 = 8.09%. One hydroquinone molecule is linked to one TATU molecule through O–H⋯N hydrogen bonding, and the crystal structure, similar to other hydroquinone:adamanzanes adducts, is based on a packing determined mainly by hydrogen bonds. Additionally, significant differences in binding affinities between the two types of nitrogen atoms of TATU were estimated.