Synthesis of Fluorescent Nanoscale Salts/Metal–Organic Frameworks for Live-Cell Imaging

The reaction between disulfonic acid, i.e., 1,5-naphthalenedisulfonic acid (NDS), Cu(NO3)2·3H2O, and variety of ditopic pyridine analogues viz., 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene (B4PVA), 9,10-bis((E)-2-(pyridin-3-yl)vinyl)anthracene (B3PVA), and 3,3′-(peroxybis(methylene))dipyridine (3PBP), resulted in the formation of salts/metal–organic frameworks (MOFs), i.e., [NDS2–·B4PVA2+·S] (FNP 1a), [NDS2–·3PBP2+·MeOH·H2O] (FNP 1b), [Cu·NDS·B4PVA] (FNP 1c), [Cu·NDS·B3PVA] (FNP 1d), and [Cu·NDS·3PBP] (FNP 1e), by the diffusion method where S in FNP 1a is a squeezed solvent molecule. Sulfonates with six oxygen atoms are involved in coordination with metal center and formed hydrogen bond interactions. X-ray structural analysis showed supramolecular architecture of the salts/MOFs where ligands act as a linear linker. The approximate particle size was calculated by powder X-ray diffraction patterns of the compounds using the Debye–Scherrer equation. The morphological characterization of the FNPs were performed by using scanning electron microscopy. The emission properties of these salts/MOFs may due the intraligand charge transfer (ILCT) and ligand to metal charge transfer phenomena. These nanocrystals were evaluated in live-cell imaging assays using HeLa and MCF-7 as a model cell-line.