Tridentate Nitrogen Ligand as a Tool for the Construction of Well-Defined Rare Earth Trichloride Complexes

LnCl₃(THF)₃ (Ln = Y, La ÷ Nd, Sm ÷ Lu) readily react with the tridentate 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me₃tach) ligand to form mono- or binuclear lanthanide trichloride complexes, depending on the stoichiometry of the reaction and the ionic radius of the metal: mononuclear pseudosandwich [LnCl₃(Me₃tach)₂], (Ln = Y, La ÷ Ho) or binuclear complexes [Ln₂Cl₆(Me₃tach)₃], or [LnCl₃(Me₃tach)(THF)]₂ (Ln = Sm, Tb). Detailed analysis of the NMR data of [LnCl₃(Me₃tach)₂] complexes with paramagnetic lanthanide ions showed that their structures remained unchanged in the toluene solution. A series of isomorphous complexes [LnCl₃(Me₃tach)(Py)₂] (Ln = La, Sm, Tb, Er, Lu; Py = pyridine) have been obtained by the recrystallization of either mononuclear or binuclear complexes from pyridine. Complexes of terbium and europium ions with the Me₃tach ligand exhibit relatively high quantum yields of metal-centered luminescence (0.39 and 0.32, respectively).