The new organic–inorganic compound (C₆H₉N₂)₂BiCl₅ (I) has been grown by the solvent evaporation method. The one-dimensional (1D) structure of the allylimidazolium chlorobismuthate (I) has been determined by single crystal X-ray diffraction. It crystallizes in the centrosymmetric space group C2/c and consists of 1-allylimidazolium cations and (1D) chains of the anion BiCl₅²⁻, built up of corner-sharing [BiCl₆³⁻] octahedra which are interconnected by means of hydrogen bonding contacts N/C–H⋯Cl. The intermolecular interactions were quantified using Hirshfeld surface analysis and the enrichment ratio established that the most important role in the stability of the crystal structure was provided by hydrogen bonding and H···H interactions. The highest value of E was calculated for the contact N⋯C (6.87) followed by C⋯C (2.85) and Bi⋯Cl (2.43). These contacts were favored and made the main contribution to the crystal packing. The vibrational modes were identified and assigned by infrared and Raman spectroscopy. The optical band gap (Eg = 3.26 eV) was calculated from the diffuse reflectance spectrum and showed that we can consider the material as a semiconductor. The density functional theory (DFT) has been used to determine the calculated gap, which was about 3.73 eV, and to explain the electronic structure of the title compound, its optical properties, and the stability of the organic part by the calculation of HOMO and LUMO energy and the Fukui indices.

Selenium nanoparticles (Se NPs) were synthesized from Na₂SeO₃ using Foeniculum vulgare (fennel) seed extract as mild sustainable reductant, coated with chitosan (Ch), and loaded with Paclitaxel (PTX). The PTX release from the Se@Ch–PTX NPs and their cytotoxicity against MDA-MB-231 breast cancer cells was studied in view of an application as drug delivery platform. Thermogravimetric analysis (TGA) showed the thermal stability of the NPs up to 300 °C. UV–vis absorption and Fourier transform IR (FT-IR) spectroscopy allowed to trace surface species originating from the F. vulgare extract on the Se NPs, while the surface of the Se@Ch–PTX NPs is characterized from Ch and PTX functionalities. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed approximate spherical shaped NPs with sizes ranging from 10 to 40 nm. Zeta potential measurements showed a clear distinction between the −39 mV found the Se NPs and +57 mV for the Ch–PTX coated NPs. The NPs showed good biocompatibility with red blood cells (RBCs) in hemolytic activity assays, exhibiting no hemolytic effects at concentrations ranging from 50 to 400 µg/mL. In vitro release studies showed a sustained and pH-responsive release pattern with a maximum release of about 80% within 22 h for Se@Ch–PTX at pH = 3.5. The Se@Ch–PTX NPs showed high antiproliferative activity against MDA-MB-231 cells with an IC₅₀ value of 12.3 µg/mL compared to about 36 for PTX and 52 µg/mL for the Se NPs. The reactive oxygen species (ROS) activity as studied through DPPH scavenging showed higher values for the Se@Ch–PTX NPs compared to the Se NP.