Experimental and theoretical approaches on structural, electronic, thermal and conductivity properties of ethynylated versus alkoxylated chalcones and elucidation of their cytotoxicity mechanisms in Acanthamoeba cells.

The new members of ethynylated and alkoxy chalcone derivatives (4TDEP and 4HPEP) featuring donor-π-Acceptor (D-π-A) and donor-π-Donor (D-π-D) systems were successfully designed and synthesized via Claisen-Schmidt condensation reaction. The physico-chemical properties of these molecules were determined via FTIR, 1H and 13C NMR, UV-Vis, UV-Fluorescence and TGA analysis. Density Functional Theory (DFT) calculations with basis set of B3LYP/6-311G (d,p) were conducted to analyze their optimized molecular geometries, HOMO-LUMO energy level and molecular electrostatic potential (MEP) of these compounds. The energy band gap for 4TDEP is lower compared to 4HPEP; however, both compounds fall within the semiconductor energy band gap range. OLEDs thin films fabrication on ITO glass substrates demonstrated electroluminescence behaviour, confirming the potential of these compounds as emissive materials. In turn, bioanalysis using Acanthamoeba cells was performed as part of an environmental safety management strategy in the development of new emerging compounds. Cytotoxicity assessment showed that 4TDEP did not exhibit cytotoxicity, whereas 4HPEP showed significant biological activity. The IC₅₀ value was determined only for 4HPEP. Morphological alterations and disruption of membrane integrity were also observed in cells treated with 4HPEP, as demonstrated by AOPI staining. In contrast, no such effects, including changes in cell morphology or membrane damage, were detected in cells exposed to 4TDEP. Surprisingly, 4HPEP exhibits stronger bioactivity linked to its optoelectronic properties, whereas 4TDEP remains biologically inert, suggesting a structure-electronic-property dependence in governing the cytotoxic response. Although 4TDEP demonstrated promising bioactivity, further structural modification is recommended to retain its desirable optoelectronic performance while minimizing cytotoxic effects.