Metal–organic frameworks (MOFs) or coordination polymers (CPs), a class of compounds constructed often by self-assembly of inorganic metal ions and organic ligands, have attracted growing interest on account of their diverse structures, permanent porosity and tunable properties, with a prospect for various applications. In some cases, the self-assembly of the building blocks produces different MOFs with the same molecular composition, i.e., supramolecular isomers. The design of supramolecular isomers in the area of MOFs is challenging and this highlight gathers recently published articles concerning the different types of supramolecular isomers, i.e., structural, conformational, catenane and optical, in this area. The syntheses and structures of the isomers and their comparison are presented, as well as the role of various parameters, such as temperature, solvent, concentration, crystallization method, additive and template, in the formation of the different supramolecular isomers, by analyzing selected examples.

A new quinazoline functionalized benzimidazole-based compound as a selective and sensitive fluorogenic chemosensor for Cu²⁺and sequential recognition of S²⁻, also being used as live cell imaging.

A series of new benzimidazole containing compounds 2-((1-R-1-H-benzimidazol-2-yl)phenyl-imino)naphthol HL^1–3 (R = methyl, ethyl or propyl, respectively) have been synthesized by Schiff base condensation of 2-(1-R-1-H-benzo[d]imidazol-2-yl)aniline and 2-hydroxy-1-naphthaldehyde. The reactions of HL^1–3 with Cu(NO₃)₂·2.5H₂O led to the corresponding copper(II) complexes [Cu(L)(NO₃)] 1–3. All the compounds were characterized by conventional analytical techniques and, for 1 and 3, also by single-crystal X-ray analysis. The interactions of complexes 1–3 with calf thymus DNA were studied by absorption and fluorescence spectroscopic techniques and the calculated binding constants (K_b) are in the range of 3.5 × 10⁵ M⁻¹–3.2 × 10⁵ M⁻¹. Complexes 1–3 effectively bind DNA through an intercalative mode, as proved by molecular docking studies. The binding affinity of the complexes decreases with the size increase of the N-alkyl substituent, in the order of 1 > 2 > 3, which is also in accord with the calculated LUMO_complex energies. They show substantial in vitro cytotoxic effect against human lung (A-549), breast (MDA-MB-231) and cervical (HeLa) cancer cell lines. Complex 1 exhibits a significant inhibitory effect on the proliferation of the A-549 cancer cells. The antiproliferative efficacy of 1 has also been analysed by a DNA fragmentation assay, fluorescence activated cell sorting (FACS) and nuclear morphology using a fluorescence microscope. The possible mode for the apoptosis pathway of 1 has also been evaluated by a reactive oxygen species (ROS) generation study.

Four novel Zn(II) and Cd(II) compounds based on a dicarboxyl-functionalized arylhydrazone of barbituric acid ligand, 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalic acid (H₅L), namely [Zn(1κO:2κO′:3κO′′-H₃L)(H₂O)₂]_n (1), [Cd(1κO,O’:2κO′:3κO′′,O′′′-H₃L)(H₂O)₂]_n (2), [Zn(κN-H₃L)(H₂O)₃]·3H₂O (3) and [Cd(1κO,O′:2κN-H₃L)(H₂O)₃]_n·4nH₂O (4), have been synthesized at different pHs under hydrothermal conditions and characterized by elemental and thermogravimetric, FT-IR, and X-ray single-crystal diffraction analyses. Compounds 1 and 2 prepared in acidic medium are coordination polymers exhibiting double chain type one-dimensional (1D) structures, whereas 3 and 4 are obtained in basic medium. Compound 3 is a mononuclear Zn(II) complex containing three lattice water molecules, but in 4, Cd(II) cations are bridged by H₃L²⁻ ligands to form an interesting zig-zag type 1D coordination polymer. The crystal structures of these compounds are stabilized by strong hydrogen bonding interactions, forming two and three-dimensional networks. The pH value of the reaction system plays a crucial role in the ligand deprotonation and in the assembly of the metal–organic polymers. These compounds act as effective heterogeneous catalysts, under mild conditions, for the Knoevenagel condensation reaction of different aldehydes with malononitrile and can be recycled at least five times without losing activity. Further, compounds 1–4 exhibit luminescence properties in the solid state at room temperature.