Synthesis and Reactivity of Cyclopentadienyl Based Organometallic Compounds and Their Electrochemical and Biological Properties

Abstract

The current focus of organometallic chemistry is based upon their synthesis, eloectrochemical properties, diverse biological behavior and their facet towards a new field of bioorganometallics concerning both organometallic and coordination chemistry. Organometallic complexes involving metal - cyclopentadienyl linkages have been an important fragment due to their unique structural variety, stability and their potential applications in organic synthesis, catalysis, bioorganometallic, advance materials, molecular recognition etc. Ferrocene and its derivatives are the most versatile aspect in organometallic chemistry because of their unique structural integrity, reversible redox behavior and have been responsible for the development of material science, molecular wires, catalysis, molecular recognition, sensing, electronic communication, bio-conjugates and medicinal chemistry. The use of ferrocenyl compounds as bioactive molecule has been established recently and several reports show that a large number of ferrocene containing compounds display interesting cytotoxic and DNA cleaving activities. Ferrocene substituted tamoxifen and chloroquine derivatives are among the many examples where systematic functionalization of ferrocene has improved the cytotoxic activity of the standard drug itself. In parallel, the half sandwich based organometallic compounds are also drawing interest because their various biological properties ranging from antimalarial, antimicrobial, anticancer, enzyme inhibitors and phototoxicity. Half sandwich compounds containing metal carbonyls are the most significant ligands in medicinal chemistry and can play a vital role as tracers in immunological analysis based on several analytical methods like FTIR, electrochemical, atomic absorption techniques etc. Moreover, ferrocenyl Schiff base compounds have been reported for their interesting coordination features and exciting biological properties. In view of the enormous potential applications of ferrocenyl and half sandwich based organometallic compounds, we focused our study to synthesize some sandwich and half sandwich based Schiff base compounds and to study their biological properties. We have been able to synthesize a range of novel ferrocene and cymantrene based Schiff base compounds and characterize by spectroscopic and crystallographic technique. We have also described the synthesis of hetero-bimetallic chalcones containing both ferrocenyl and cymantrenyl fragments and studied their reactivity towards mono- and diphosphine substitution. In addition, compounds containing multiple redox centers have also been highly focused due to their various application related to electronic communication, sensors and molecular wires. In this regard, we focused on the synthesis of diferrocenyl bifunctional molecular systems containing both hydrazone and enone units using simple and systematic synthetic route. Efforts have been made to study the unique structural feature and to understand the biological and sensing properties of some of the compounds. We have carried out cyclic-voltammetric studies with different analogs of the diferrocenyl compounds to understand the electronic communication behavior inside the molecule. DFT calculation was also performed to establish some of the interesting features related to structural stability, metal ion interaction and molecular orbital energies.