Aluminum complexes of non-chiral-salalen ligands were investigated in the catalysis of ring-opening polymerization (ROP) of lactide and ε-caprolactone and in their copolymerization. The aluminum-salalen complexes were found to polymerize all varieties of lactide, namely: L-, D-, rac- and meso-lactide, and showed moderate productivities. rac-LA gave rise to isotactic polylactides (with P_m up to 72%), while meso-LA gave rise to heterotactic polylactides (with a P_m of 79%). An experiment was designed for distinguishing between chain-end control and enantiomorphic-site control combined with polymeryl exchange for the isotactic stereoblock microstructure observed for the PLA produced from rac-LA; it gave strong evidence for polymeryl exchange between propagating species. Finally, this class of catalysts promoted the copolymerization of ε-caprolactone and lactides. In particular, compound 2b allowed controlled random copolymerization of ε-caprolactone and L-lactide.

Salan, salen and salalen iron complexes as catalysts in CO₂/epoxide reactions and in the ROP of ε-caprolactone and l-lactide.

In this work, we investigate the mode of interaction of a family of fluorescent zinc complexes with HS^– and H₂S. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS^– binds the zinc center of all the complexes under investigation. Treatment with neutral H₂S exhibits a markedly different reactivity which indicates selectivity for HS^– over H₂S of the systems under investigation. Striking color changes, visible to the naked eye, occur when treating the systems with HS^– or by an H₂S flow. Accordingly, also the fluorescence is modulated by the presence of HS^–, with the possible formation of multiple adducts. The results highlight the potential of the devised systems to be implemented as HS^–/H₂S colorimetric and fluorescent sensors. Bioimaging experiments indicate the potential of using this class of compounds as probes for the detection of H₂S in living cells.

The aim of the present review is to highlight the most recent achievements in different fields of application of salen-based zinc and aluminum complexes. More specifically this article focuses on the use of aluminum and zinc salen-type complexes as optical probes for biologically relevant molecules, as catalysts for the ring opening polymerization (ROP) of cyclic esters and co-polymerization of epoxides and anhydrides (ROCOP) and in the chemical fixation of carbon dioxide (CO₂). The intention is to provide an overview of the most recent results from our group within the framework of the state-of-art-results in the literature.