Determination of the structure of EuTETA and the luminescence properties of EuTETA and EuDOTA (TETA=1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate and DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate)

The crystal structure and the luminescence of the complex Na[Eu(TETA)]·2H2O·4NaCl (TETA=1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate) have been determined. The space group is P, and the lattice parameters are a=9.283(2) Å, b=17.794(3) Å, c=19.8087(17) Å, α=70.733(11)°, β=83.474(12)°, γ=88.478(18)°, V=3068.6(9) Å3, ρ=1.890 g cm−3, and Z=2. The luminescence of Na[EuDOTA·H2O]·3H2O (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) has also been reported. In the TETA macrocycle, the Eu(III) is completely encapsulated via coordination to the four nitrogen atoms and the four carboxylate oxygen atoms of the ligand. The geometry of the eight-coordinate polyhedron is a strongly distorted dodecahedron. The characteristic feature in the geometry is the conformation of the pendant carboxylate arms. The asymmetric unit consists of two independent molecules, differentiated from the helicities of the pendant arms. When the EuTETA and EuDOTA crystals are excited by UV light, they produce very characteristic luminescences responsible for the 5D0→7FJ (J=0, 1, 2, 3, 4) transitions. Unlike the EuDOTA complex, the luminescence structure of the EuTETA complex is significantly affected by the crystalline state. This might be due to the rigidity of the complex. The energy-level schemes of the 7FJ states and detailed assignments for the observed luminescence lines of the EuTETA and EuDOTA complexes have been proposed by phenomenological simulation in the framework of the crystal-field Hamiltonian.