Sixteen new 3d–4f binuclear complexes have been obtained using two Schiff-base ligands, Hvalampy and Hvalaepy, derived from the reaction of o-vanillin and 2-aminomethyl-pyridine or 2-(2-aminoethyl)-pyridine, respectively. Hvalaepy ligand: [Zn(valaepy)2Sm(O2NO)3]·CH3CN 1; [Ni(valaepy)2Eu(O2NO)3(H2O)]·CH3CN 2; [Ni(valaepy)2Gd(O2NO)3(H2O)]·CH3CN 3; [Ni(valaepy)2Dy(O2NO)3(H2O)]·CH3CN 4; [Ni(valaepy)2Ho(O2NO)3(H2O)]·CH3CN 5; [Cu(valaepy)2Eu(O2NO)3]·CH3CN 6; [Cu(valaepy)2Gd(O2NO)3]·CH3CN 7; Hvalampy ligand: [Zn(valampy)2Pr(O2NO)3]·CH3CN 8, [Zn(valampy)2Sm(O2NO)3]·CH3CN 9; [Zn(valampy)2Gd(O2NO)3]·CH3CN 10; [Zn(valampy)2Tb(O2NO)3]·CH3CN 11; [Zn(valampy)2Dy(O2NO)3]·CH3CN 12; [Zn(valampy)2Eu(O2NO)3]·CH3CN 13; [Ni(valampy)2La(O2NO)3(H2O)2]·2H2O 14, [Ni(valampy)2Sm(O2NO)3(H2O)2]·2H2O 15; [Ni(valampy)2Eu(O2NO)3(H2O)]·2CH3CN 16. The crystal structures of the sixteen compounds can be described as resulting from the coordination of two valaepy− (or valampy−) ligands to the 3d metal ions through two phenoxo oxygen atoms and nitrogen atoms, arising from the pyridyl and azomethynic groups. In all these compounds the 3d and 4f metal ions are bridged by the phenoxo oxygen atoms. The comparative analysis of the crystal structures shows several differences, which arise mainly from the stereochemical preference of the 3d metal ions. These ions arrange the two organic ligands in positions that favour or not the coordination of the methoxy groups to the lanthanide ions. The magnetic properties of compounds 2, 3, 4, 5, 7, 14, 15, and 16 have been investigated. The exchange interactions between NiII and GdIII in 3, and between CuII and GdIII in 7 were found to be ferromagnetic (JNiGd = 1.56 cm−1; JCuGd = 4.94 cm−1; H = −JSGdSM). For the 3d–4f binuclear complexes derived from the Hvalampy ligand (namely 8–13) the photoluminescence (PL) properties were investigated in the Vis spectral region. The results provide evidence for the relatively stronger antenna effect in 9 and 11 compared to 8, 12 and 13.

The mononuclear complexes belonging to the [M(valXn)]0/+ family [H2valXn are bicompartmental ligands derived from o-vanillin and 1,2- or 1,3-diamines; M = Ni(II), Cu(II), Au(III)] can efficiently act as receptors towards various hydrogen bond donors. The co-crystallization processes between [Ni(valXn)] complexes and ammonium salts (NH4Z, Z− = ClO4−; PF6−; C6H5NH3ClO4) led to different supramolecular arrangements in the crystals depending on the host:guest molar ratio used in reactions. For a 2:1 stoichiometry, supramolecular dimers were obtained in the crystals: 2[Ni(valen)]·NH4Z (Z− = ClO4−, 1a; Z− = PF6−, 1b), 2[Ni(valphen)]·NH4ClO4·CH3OH 1c, 2[Ni(valmen)]·C6H5NH3ClO43, while for a 1:1 stoichiometry a supercomplex with a quadruple deck architecture resulted: 4[Ni(valen)]·3NH4ClO42. The co-crystallization of the Reinecke salt with mononuclear complexes from the [M(valXn)] family affords the following crystals: [Ni(valen)]2·NH4[Cr(NCS)4(NH3)2]·CH3OH 4, [Ni(valdmpn)]2·NH4[Cr(NCS)4(NH3)2]·2H2O 5, and [Cu(valpn)]·NH4[Cr(NCS)4(NH3)2]·CH3CN 6, in which the [M(valXn)] complexes interact with the ammonium ions and ammonia ligands, resulting in supramolecular chains. The composition and the topology of the supramolecular chain can be changed by replacing the ammonium ion from the Reinecke salt with a cationic receptor, [Au(valpn)]+:[Au(valpn)][Cr(NCS)4(NH3)2] 7.