Experimental and theoretical insights into the stability and reactivity of Isatin-derived Schiff bases

This study explores the stability and reactivity of two isatin-derived Schiff bases, ISSB1 and ISSB2 , via experimental and computational approaches. Experimental synthesis and characterisation of these Schiff bases were carried out to confirm their synthetic accessibility and compare theoretical predictions with experimental findings. To gain deeper insights into their electronic properties, density functional theory (DFT), conceptual density functional theory (CDFT), and topological analyses were employed, highlighting ISSB2 ’s promising potential. The DFT approach encompassed geometry optimisation, FMO analysis, MEP mapping, Mulliken charge analysis, and vibrational analysis, collectively assessing the reactivity parameters of ISSB1 and ISSB2 . The influence of solvents on reactivity was explored using the IEFPCM model, while band gap energies were evaluated across different phases. Furthermore, topological studies, including ELF, LOL, and QTAIM analyses, provided additional validation for the electronic parameters predicted through DFT calculations. Additionally, Fukui function analysis within the CDFT framework strongly reinforced ISSB2 ’s reactive potential. From an application perspective, the higher reactivity of ISSB2 , as demonstrated computationally, is further explored through two types of derivatives of the isatin-based Schiff bases: stable metal complexes and hetero-spirocyclic compounds derived from them. The initial phase of computational evaluation focused on Fe-complexes ( ISSB1-Fe and ISSB2-Fe ) and hetero-spirocyclic derivatives ( ISSB1-SP and ISSB2-SP ), offering deeper insights into their reactivity and potential applications. • Experimental and theoretical studies evaluated the stability and reactivity of ISSB1 and ISSB2 . • Both Schiff bases were synthesised and characterised to validate theoretical predictions experimentally. • DFT, topology, and CDFT studies confirm the enhanced reactivity of ISSB2 . • FMO, MEP, Mulliken charge distribution, and vibrational analyses further supported the computational results. • ISSB2 ’s reactivity was further explored via Fe-complexes and hetero-spirocyclic derivatives.