Caterina Zuffa

This study examines the relationship between molecular structure and crystal packing in organic crystals of homologous compounds, with an emphasis on isomorphism─the ability of a series of molecules to maintain the same space group and homothetic unit cell when they crystallize despite variations in chemical composition. This phenomenon challenges the conventional view that distinct molecular structures lead to diverse crystalline forms, particularly for chiral molecules, where the interplay between chirality and molecular symmetry within crystal lattices remains poorly understood. Herein, we present the first structurally consistent series of five m-Y-phenyl-N,N-diisopropylglyoxylamide derivatives (Y = H, F, Cl, Br, or I), exemplifying a rare case of isomorphism within a homologous set of achiral molecules in solution that crystallize as conglomerates by adopting a twisted chiral conformation. These enantiomorphic crystals were manually resolved using Pasteur’s method, enabling direct investigation of symmetry breaking at the morphological level. Continuous chirality measures quantitatively confirm consistent chiral behavior at both the molecular and crystalline levels, while the unit cell similarity index further validates the isomorphic nature of the series. Thermal analyses reveal systematic trends in stability across the series, while crystallographic studies demonstrate the persistence of packing motifs and supramolecular chirality. Overall, this work introduces a rare class of chiral molecular materials derived from chemically distinct achiral molecules that exhibit isomorphic molecular packing. These systems are broadly relevant to fields ranging from pharmaceuticals to functional materials, where small variations in the solid-state structure can lead to substantial differences in performance.

Photodynamic therapy is a non-invasive treatment strategy for various types of cancer, based on the use of light to activate a photosensitizer which triggers processes leading to cell death. Given the increasing interest in the development of mitochondria-targeted photosensitizers, in this study we synthesized two novel thiadiazol-substituted porphyrins, 5,10,15,20-tetra(2,1,3-benzothiadiazol-5-yl) porphyrin (C1) and 5,10,15,20-tetra(1,2,3-thiadiazol-4-yl) porphyrin (C2), designed to target mitochondria in cancer cells thanks to the azole residues present in their structure. The two porphyrinic compounds were characterized in terms of structural and photophysical properties, revealing high yields of singlet oxygen production. Their interaction with biological structures was analyzed in a triple-negative human breast carcinoma cell line (MDA-MB-231), either as free compounds or delivered via mitochondriotropic liposome formulations. Both newly synthesized porphyrins entered MDA-MB-231 cells, with compound C2 demonstrating more efficient localization in the cytoplasm and in mitochondria. Dark and phototoxicity tests were also performed: both compounds proved to be effective phototoxic agents, with C2 showing the highest activity, making it a promising photosensitizer for mitochondria-targeted photodynamic therapy.

The crystal structures of organic semiconductors are critical when they are integrated into optoelectronic devices, such as organic field-effect transistors (OFETs). In this study, we introduce a crystal engineering approach that leverages weak, nondirectional dispersion forces and steric effects, working together to govern the molecular packing. We investigated how the substitution at the peri-position affects the crystal structure in a series of oligorylene molecules. Upon elucidation of the crystal structures, we found a distinct difference between symmetrical and unsymmetrical derivatives. The unsymmetrical derivatives are prone to forming a sandwich herringbone (SHB) motif, while symmetrical derivatives exhibit a typical herringbone (HB) motif. In most of the rylene derivatives, substitutions at the peri-position triggered an "end-to-face" orientation within the HB structure, rather than an "edge-to-face" orientation, which occurs more often. Results from the Hirschfeld surface analysis provide evidence that the "end-to-face" orientation promotes C-H-π interactions between terminal methyl groups and the π-core of the molecules. While these C-H_methyl---π interactions contribute to the overall stability of the packing structure, they remain ineffective in enhancing the charge transport properties. In contrast, a particular derivative, tetramethyl perylene (TMP), exhibits a HB structure with an edge-to-face orientation, promoting both C-H---π and π---π interactions. These interactions are crucial for improving the charge carrier mobility, as evidenced by mobility values. For TMP, we could obtain the mobility value of 0.05 cm² V^-1 s^-1 in OFETs, whereas a slightly higher mobility of 0.2 cm² V^-1 s^-1 was observed with Field-Induced Time-Resolved Microwave conductivity (FI-TRMC) technique.

Hybrid coordination polymers based on AgCl or AgBr and different n-picolylamine ligands show interesting and tunable electronic and photophysical properties.

This study investigates the mechanochemical reactions between AgBr 3-picolylamine and 4-picolylamine. The use of different stoichiometry ratios of the reagents allows [(AgBr)(n-pica)]_n and [(AgBr)₂(n-pica)]_n to be obtained, and we report the new structures of [(AgBr)₂(3-pica)]_n and [(AgBr)₂(4-pica)]_n which are characterized by the presence of the following: (a) infinite inorganic chains, (b) silver atom coordinated only by bromide atoms and (c) argentophilic interactions. Furthermore, we studied the interconversion of [(AgBr)(n-pica)]_n/[(AgBr)₂(n-pica)]_n by mechanochemical and thermal properties. The in situ experiments suggest that [(AgBr)(3-pica)]_n is kinetically favoured while [(AgBr)₂(3-pica)]_n is converted into [(AgBr)(3-pica)]_n only with a high excess of the ligand. Finally, the liquid nature of the ligands is not sufficient to assist the grinding process, and the complete reaction is observed with the addition of a small quantity of acetonitrile.

Hybrid coordination polymers (HCP) are interesting for the ability to converge the properties of inorganic and organic systems in one single compound and our attention has been focused on silver-based HCP due to their luminescence properties.