Aspirin ligands as a novel approach to synthesis Fe3+-metal complexes to modify the structural and optical characterization of PVA matrix

Abstract In this work, a novel methodology has been used to synthesis Fe 3+ - metal complexes using aspirin as a precursor for salicylic acid ligands formed in situ. The synthesis and thorough characterization of ferric chloride-aspirin (FeCl 3 -acetylsalicylic acid) complex inserted into the polyvinyl alcohol (PVA) matrix have been reported. PVA based composites have been prepared with various amounts of Fe 3+ -metal complex utilizing casting approach. The creation of a new metal-drug complex was established by a change in the visible colour and confirmed by FTIR, which revealed the coordination of Fe3 + ions to the oxygen containing groups of the drug, and an increase in the intermolecular hydrogen bonding of the polymer matrix. UV-Vis spectroscopy indicated an enhanced absorption and a large red shift with the inclusion of the complex. The wide optical band gap of pure PVA (5.6 eV) was successfully reduced to 1.5 eV in the PVA-2 composite. This confirms that metal complexes play a crucial role in optical band gap tuning. The gradual increase in refractive index and dielectric constant (PVA-0 to PVA-2) is a confirmation for enhanced electronic polarizability and charge transfer. Dielectric loss also revealed interband electronic transitions and structural changes upon the formation of complex. These findings suggest a collaborative interaction of the metal, drug and polymer, which suggests that the composite has a huge potential in optoelectronic, smart sensors and UV protective applications.