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Condensation reactions of mono- and didodecyl-substituted-2,5-diformylthiophene with hydrazine, p-diaminobenzene, 2,7-diaminofluorene, and 1,5-diaminonaphatalene give the corresponding polyazines (PAZs) and polyazomethines (PAMs), which have been characterized by thermal, structural, and optical analyses. The former polymers begin to decompose at 300 °C, while the latter polymers are stable up to 360 °C. All disubstituted polymers and the regioregular monosubstituted polyazines show nematic character. Disubstituted polymers display a larger conjugation with respect to monosubstituted ones. This effect has been attributed to a different conformation of thiophenic rings versus imino-linkages assumed by the polymeric backbone in the two classes of polyazines. Particular attention has been devoted to study the reactivity of mono- and disubstituted dialdehydes toward condensation with nucleophiles displaying different steric hindrance or power. Specifically the study of the reaction onset allowed us to determine the conditions to obtain regioregular monosubstituted polymers even with hydrazine, which is the less hindered and the more powerful nucleophile used.

The aromatic methylene blue cation (MB) shows unprecedented ligand behavior in the X-ray structures of the trigonal-planar (TP) complexes MBMCl (M = Cu, Ag). The two isostructural compounds were exclusively synthesized by grinding together methylene blue chloride and MCl solids. Only in the case of AuCl did the technique lead to a different, yet isoformular, Au derivative with separated MB and AuCl counterions and no direct N-Au linkage. While the density functional theory (DFT) molecular modeling failed in reproducing the isolated Cu and Ag complexes, the solid-state program CRYSTAL satisfactorily provided for Cu the correct TP building block associated with a highly compact π stacking of the MB ligands. In this respect, the dispersion interactions, evaluated with the DFT functional, provide to the system an extra energy, which likely supports the unprecedented metal coordination of the MB cation. The feature seems governed by subtle chemical factors, such as, for instance, the selected metal ion of the coinage triad. Thus, the electronically consistent Au ion does not form the analogous TP building block because of a looser supramolecular arrangement. In conclusion, while a given crystalline design is generally fixed by the nature of the building block, a peculiarly efficient supramolecular packing may stabilize an otherwise unattainable metal complex.

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An anionic Pd₁₅-oxo-cluster [Pd₁₅(μ₃-SeO₃)₁₀(μ₃-O)₁₀Na]⁹⁻ has been synthesized. It is the result of an unprecedented self-assembly of Pd(2+) and Na(+) cations, SeO₃²⁻ and oxo anions. It has been found for the first time, that selenito groups can give rise to supramolecular interactions in the solid state with palladium atoms, through the selenium electron lone pairs.

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