Abstract: Two rare earth nitrate complexes with phosphinoxide (-CH₂P(O)Ph₂)-substituted calix arene were prepared and characterized by elemental analysis and IR spectroscopy. Their crystal structures were determined by X-ray diffraction method. Lanthanum nitrate complex [L·La(OH₂)(NO₃)₂]NO₃( L=tetrakis(methylenediphenylphosphinoxide)calixarene) belongs to tetragonal crystal system, space group P4₃2₁2 with a=1.897 7(4) nm, b=1.897 7(4) nm, c=3.108 7(11) nm; Z=4; V=11.196(5) nm³; D_c=1.097 g/cm³, F(000)=3 712, μ=0.491 mm^-1, R₁=0.118 1, wR₂=0.193 0. Europium nitrate complex [L·Eu(OH₂)(NO₃)₂]NO₃·CH₃OH belongs to monoclinic crystal system, space group C₂/c with a=2.881 72(11) nm, b=5.401 5(2) nm, c=2.011 89(7) nm; β=133.406 7(9)°, Z=8; V=22.751 1(14) nm³, F(000)=7 464, R₁=0.067 1, wR₂=0.179 4. The structures of the two complexes are very similar, the rare earth atoms are both nine-coordinated with four oxygen atoms from phosphorus-oxygen bonds and four oxygen atoms from two bidentate nitrate anions and one oxygen atom from a water molecule. The coordination polyhedron is a single-capped square antiprism. In the europium complex, a methanol molecule was included in the calixarene.

Key words: Lanthanum and europium ionic complexes, Phosphinoxide[-CH₂P(O)Ph2]-substituted calix[4]arene, Crystal structures