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A family of organometallic compounds has been designed based on half-sandwich ruthenium complexes [(arene)Ru(L)X2] (X = Cl, I); this showed dynamic host–guest properties towards volatile molecules, caused by small local reversible structural rearrangements. These features are derived from the supramolecular organization of the compounds in the solid state, based on a so-called wheel-and-axle pattern, which is known to favour guest inclusion. The molecular features of the Ru complexes (arene size and shape, ligand size and chemical properties, and halogen nature) were screened in order to optimize the final performance of the materials. The design strategy has proven to be successful, affording materials capable of allowing dynamic exchange of volatile molecules by gas–solid processes and solid–solid transformations without loss of crystallinity. [ABSTRACT FROM AUTHOR]

A family of organometallic compounds has been designed based on half-sandwich ruthenium complexes [(arene)Ru(L)X2] (X = Cl, I); this showed dynamic host–guest properties towards volatile molecules, caused by small local reversible structural rearrangements. These features are derived from the supramolecular organization of the compounds in the solid state, based on a so-called wheel-and-axle pattern, which is known to favour guest inclusion. The molecular features of the Ru complexes (arene size and shape, ligand size and chemical properties, and halogen nature) were screened in order to optimize the final performance of the materials. The design strategy has proven to be successful, affording materials capable of allowing dynamic exchange of volatile molecules by gas–solid processes and solid–solid transformations without loss of crystallinity. [ABSTRACT FROM AUTHOR]

Dynamically porous crystalline materials have been obtained by engineering organometallic molecules. This feature article deals with organometallic wheel-and-axle compounds, molecules with two relatively bulky groups (wheels) connected by a linear spacer. The wheels are represented by half-sandwich Ru(ii) moieties, while the spacer can be covalent or supramolecular in character. Covalent spacers are obtained using divergent bidentate ligands connecting two [(arene)RuX2] groups. Supramolecular spacers are instead obtained by exploiting the dimerization of COOH or C(O)NH2 groups appended to N-based ligands. A careful choice of ligand functional groups and X ligands leads to the isolation of crystalline materials with remarkable host–guest properties, evidenced by the possibility of reversibly capturing/releasing volatile guests through heterogenous solid–gas reactions. Structural correlations between the crystalline arrangement of the apohost and the host–guest compounds allow us to envisage the structural path followed by the system during the exchange processes. [ABSTRACT FROM AUTHOR]

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Half-sandwich ruthenium(II) complexes containing the two amino-amide ligands 4-aminobenzamide (4AB) and 4-aminobenzanilide (4ABN) have been synthesized and structurally characterized. The complexes have the general formula {[(p-cymene)RuCl2(κN-ligand)](x.solvent)}. The crystal packings are governed by extended hydrogen-bond networks involving the N-H bonds of the amine and amide groups as well as the Cl ligands. In the case of 4AB, two different non-solvate polymorphs (x = 0) have been isolated from methanol (1α) and water (1β, disappearing polymorph). In both cases, the amide groups of two molecules associate, giving rise to a supramolecular ring, where the N-H bond not involved in the ring intermolecularly contacts a neighbouring Cl ligand. The resultant frameworks are very robust, thus impeding the insertion of solvent molecules. A methanol-solvate (1.MeOH) has in fact been isolated in very low yield where two methanols bridge two different amide groups. These crystals are highly unstable at room temperature. However, 1α shows a distinct reactivity toward NH3 in heterogeneous gas-uptake experiments, although the final nature of the product has not yet been defined. A comparison between the structural results reported here and those previously collected with 4-aminobenzoic acid reveals that the COOH function leads to linear supramolecular wheel-and-axle motifs, while the C(O)NH2 function of 4AB leads to bent supramolecular wheel-and-axle motifs. The complexes containing 4ABN (2 and 2.2H2O) have always been crystallized as solvate (2.EtOH and 2.H2O), where the included guest molecules are hydrogen-bonded to the C(O)NHR functionality, thus preventing the dimerization of the amide groups. [ABSTRACT FROM AUTHOR]

In this study, a new series of extended linkers containing different polyaromatic chromophores (biphenyl, naphthalene, anthracene, fluorene, 9,9-dimethylfluorene and fluorenone) functionalized with isonicotinoyl moieties have been synthesized by Pd-catalyzed cross-coupling reactions involving isonicotinamide and the appropriate aromatic dibromide. The optimized protocol led to the isolation of the target molecules in good yield and with high purity. These were characterized by 1 H NMR, FTIR, MS, and elemental analysis and their solid state structures were solved by single-crystal X-ray diffraction analysis. Electronic absorption and emission spectra were collected both in solution (DMF) and in the solid state. TDDFT calculations were carried out to investigate the effect of the isonicotinoyl moieties on the spectral features of the central chromophores. Although in solution only the linker containing a fluorenone scaffold shows a weak fluorescence, all the isolated linkers turned out to be fluorescent in the solid state, thus paving the way for their use for the fabrication of fluorescent MOFs.