Synthesis of Novel Organometallic Compounds of Groups VIII and IX and evaluation of their catalytic and biological potential

Transition metal complexes are a fascinating and essential class of compounds in chemistry. They consist of transition metals, which are elements found in the middle of the periodic table, surrounded by ligands, which are molecules or ions that bind the metal center. Transition metals exhibit different oxidation states and can interact with a large number or type of molecules. Due to the diversity of chemical bonding possible between the metal centre and the different ligands, the advances in these areas have presented unique opportunities and challenges in transition-metal chemistry. In fact, the behaviour of the metal−ligand bond represents a very tuneable aspect for achieving target properties like the interplay between spin, oxidation state, coordination environment and metal-electron configuration. In this way this class of compounds exhibits a wide range of properties which plays crucial roles in various chemical, industrial, and biological processes.1 For this reason, the transition metal complexes are attractive targets for the design of a wide range of functional materials with applications in catalysis, supramolecular assemblies, molecular devices and medicinal chemistry. In fact, they have shown important catalytic activities or bioactivities among which anti-inflammatory, antibiotics, anticonvulsant, analgesic, antimicrobial, antiparasitic, antitubercular, anti-HIV, antioxidant and anticancer.2–7 According to this, the scope of this doctoral thesis is based on the synthesis of novel coordination compounds containing particular metal and ligands able to provide an intrinsic anti-tumor or catalytic activity. The two research lines are herein described in two different parts:  Biologically active compounds: related to Ru(II) and Os(II) metal centers coordinated with curcumin and bisdemethoxycurcumin derivatives as ligands. The curcuminoids (curcumin and bisdemethoxycurcumin) are well-known for their biological potentials which also include the anticancer activity but, unfortunately, their low water solubility and low bioavailability decrease the overall activity. The aim of this part was focused on the strategical modification of the curcuminoids structure (which includes the aryl side chain bioconjugation; reduction of the conjugation’s degree and heterocyclization of di-keto functionality) suitable for the improvement of this aspects. Additionally, Ru(II) and Os(II) possess their own anticancer activity. Based on this statements, the scope of this part was to synthesize new complexes and to see the correlation between their chemical structure and the related cytotoxicity. Catalytically active compounds: referred to Ru(II), Rh(III) and Ir(III) metal centres coordinated with pyrazolone-containing hydrazone ligands. The pyrazolone-containing hydrazone compounds are a class of Schiff base molecules acting as polydentate ligands for different metal centres. More precisely, the hydrazine moiety present into the structure, confers a κ-N,O coordinating sphere or, with a pyridine-hydrazine moiety, also a κ-N,N binding mode can be afforded through the nitrogen atom present into the pyridine ring. In both of the coordination typology, the presence of nitrogen atoms makes them suitable as a Lewis base catalytic site. Moreover, the Platinum group metals (Lewis acid site) is famous for its huge catalytic applications but no examples of catalysis with Ru(II), Rh(III) and Ir(III) bearing pyrazolone-containing hydrazone are reported in literature. Thus, the novel complexes have been evaluated for their ability to act as bifunctional catalyst toward tandem reactions.