STRUCTURE AND SPECTROSCOPIC AND MAGNETIC-PROPERTIES OF RARE-EARTH METAL(III) DERIVATIVES WITH THE 2-FORMYL-4-METHYL-6-(N-(2-PYRIDYLETHYL)FORMIMIDOYL)PHENOL LIGAND

The compounds [ML2(H2O)4](ClO4)3-4H2O ((1)M), Where M is a trivalent rare earth metal and L the bidentate liquid 2-formyl-4-methyl-6-(N-(2-pyridylethyl)formimidoyl)phenol, have been synthesized. Single crystals of [GdL2(H2O)4](ClO4)2CI.2.75H2O have been obtained, and its crystal structure has been solved. This compound crystallizes in the monoclinic system, space group P2(1)/c. The lattice parameters are a = 18.079(4) angstrom, b = 14.560(3) angstrom, c = 16.409(3) angstrom, beta = 92.93(2)-degrees, and Z = 4. The structure consists of [GdL2(H2O)4]3+ cations, perchlorate and chloride anions and noncoordinated water molecules. The Gd atom is surrounded by eight oxygen atoms, four belonging to water molecules and the other four to the carbonyl and phenolic functions of two L ligands. The coordination sphere of Gd is very close to a perfect square antiprism. (1) Eu exhibits a strong luminescence in the solid state. The transition energies of the luminescence spectrum have been determined. The temperature dependences of the molar magnetic susceptibility chi(M) for (1)M (M = Gd, Nd, Eu, Sm) have been measured. A perfect Curie law is observed for (1)Gd. The EPR spectrum reveals a zero-field splitting within the S-8(7/2) ground state characterized by an axial parameter Absolute value of D = 4.0 X 10(-2) CM-1. Chi(M)T for (1)Nd decreases from 1.64 cm3 K mol-1 at 300 K down to 0.8 CM3 K mol-1 at 4.2 K as the temperature T is lowered, due to the crystal-field splitting of the I-4(9/2) free-ion state. For both (1)Eu and (I)Sm compound, the first free-ion excited states are thermally populated at 300 K; hence, their magnetic behaviors significantly deviate from the Curie law. The magnetic data have been satisfactorily interpreted in the free-ion approximation. For(1)Eu, an excellent agreement between optical and magnetic properties has been obtained.