Tris-beta-diketonate lanthanide(III) complexes (Ln = Eu, Er, Yb, Tb), of general formula [Ln(acac)3 L(m)], with chelating ligands such as 4,7-disubstituted-1,10-phenanthrolines and 4,4'-disubstituted-2,2'-bipyridines, have been synthesized and fully characterized. The inductive effects of the para-substituents on the aromatic N-donor ligands have been investigated both in the solid and in the solution states. Single-crystal X-ray structures have been determined for the diethyl 1,10-phenanthroline-4,7-dicarboxylate europium and 4,4'-dimethoxy-2,2'-bipyridine erbium derivatives, revealing a distorted square antiprismatic geometry around the lanthanide atom in both cases. The influence exerted by the p,p'-substituents with respect to the nitrogen coordinating atoms on the Ln-N bond distances is discussed comparing the geometrical parameters with those found for the crystal structures containing the fragments [Ln(III)(phen)] and [Ln(III)(bipy)] obtained from the Cambridge Structural Database. The influence exerted by the electron-attracting groups on the coordination ability of the ligands, that in some cases becomes lack of coordination of the lanthanide ions, has been also detected in solution where the loss of the ligand has been followed by UV-vis spectroscopy. Moreover, the use of relatively long alkoxy chains as substituents on the 1,10-phenanthroline ligand led to the formation of a promesogenic lanthanide complex, whose thermal behavior is encouraging for the synthesis of new lanthanide liquid-crystalline species.

The 4,4‘-disubstituted azobenzene ligands HL a - d react with [(η3-C4H7)Pt(μ-Cl)]2 to give the dinuclear cycloplatinated complexes [(L a - d )Pt(μ-Cl)]2, which are easily converted to their mononuclear Pt(II) acetylacetonate derivatives [(L a - d )Pt(acac)]. Oxidative addition to the square-planar Pt(II) complexes [(L a - d )Pt(acac)] of electrophilic substrates such as I2 or CH3I (RI) eventually led to the corresponding octahedral Pt(IV) [(L a - d )Pt(acac)I2] and [(L a - d )Pt(acac)(CH3)I] products. Characterization by X-ray crystallography on model complexes [(L a )Pt(acac)], [(L a )Pt(acac)I2], and [(L a )Pt(acac)(CH3)I] has been carried out, showing that the I2 or CH3I ligands are bound to the Pt(IV) center at the apical positions. The presence of two ligands in apical position led to the loss of the short intermolecular Pt- - -Pt distance of 3.311(1) Å observed in the square-planar complex [(L a )Pt(acac)]. Thermotropic mesomorphism is observed for both the Pt(II) and Pt(IV) species with clearing temperatures, mainly lower than those of the corresponding organic ligands. These products are the first examples of Pt(IV) octahedral liquid crystalline species and suggest that oxidative addition to appropriate Pt(II) precursors should be a convenient synthetic procedure for new hexacoordinated Pt(IV) mesogenic materials.

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A series of bischelate ionic silver complexes [Ag(L*)(2)][X] was prepared by complexation of a newly synthesized 2,2'-bipyridine containing chiral alkoxy chains in the 4,4' positions. The appropriate choice of the construction motifs allows the preparation of new materials in which several functionalities can be introduced. Indeed, when the anion X(-) is a triflate or a dodecylsulfate group, the right combination of intermolecular interactions promotes the production of liquid crystalline mesophases. Therefore, the presence of coordinating anions, which drives the supramolecular assembly, is essential to generate, at the same time, room-temperature columnar hexagonal mesomorphism, the columnar helical supramolecular structure, and excimeric emission.