Crystal structures of uranyl ion complexes of tetrahydroxy[3.1.3.1]metacyclophane (homocalix[4]arene)

The first crystal structures of complexes of tetrahydroxy-[3.1.3.1]metacyclophanes, also termed homocalix[4]-arenes, are reported. In the two uranyl ion complexes obtained, with different para-substituents, the complex core is analogous to that in tetrahomodioxacalix[4]arene complexes, with the cation in a tetra-phenoxide, distorted square-planar environment. The packing in one of these complexes comprises two different arrangements, one of them being a columnar stacking of complex molecules with sandwiched triethylammonium counter-ions hydrogen bonded to one complex and held by cation-pi and CH-pi interactions within the cavity of the other neighbouring one.