Structural, Luminescent and Thermal Properties of Heteronuclear Pd(II)–Ln(III)–Pd(II) Complexes of Hexadentate N(2)O(4) Schiff Base Ligand

New Pd(II)–Ln(III)–Pd(II) complexes of hexadentate N(2)O(4) Schiff base ligand (H(4)L: N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane) with Eu (1), Tb (2), Er (3) and Yb (4) ([Pd(2)Eu(H(2)L)(2)NO(3)](NO(3))(2)∙2H(2)O∙2CH(3)OH 1, [Pd(2)Ln(H(2)L)(2)H(2)O](NO(3))(3)∙3H(2)O, where Ln = Tb 2, Er 3, [Pd(2)Yb(H(2)L)(2)H(2)O](NO(3))(3)∙5.5H(2)O 4) were synthesized and characterized structurally and physicochemically by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC) and luminescence measurements. The compounds 1–4 are built of cationic heterometallic Pd(II)–Ln(III)–Pd(II) trinuclear units. The palladium(II) centers adopt a planar square geometry occupying the smaller N(2)O(2) cavity of the Schiff base ligand. The lanthanide(III) is surrounded by two Schiff base ligands (eight oxygen atoms) and its coordination sphere is supplemented by a chelating bidentate nitrate ion in 1 or by a water molecule in 2–4. The complexes have a bent conformation along the Pd(II)–Ln(III)–Pd(II) line with valence angles in the ranges of 162–171°. The decomposition process of the complexes results in mixtures of: PdO, Pd and respective lanthanide oxides Eu(2)O(3), Tb(2)O(3), Tb(4)O(7), Er(2)O(3), Yb(2)O(3). The luminescent measurements show low efficiency intramolecular energy transfer only in the complex of terbium(III) (2).