Microwave and conventional synthesis, characterization, photophysical properties, toxicity and bacterial staining of new mesoporous zinc(II)-based luminescent coordination polymer

In this paper we reported the microwave assisted and conventional syntheses of new mesoporous zinc-based luminescent coordination polymer (2: catena-poly[(aquazinc-μ-5-ylmethyleneamino-8-quinolinolate-O:N)-μ-(benzoate-O:O)]) derivative from new rigid Schiff base linker (1a: (E)-4-((quinolin-5-ylmethylene)amino)benzoic acid). The microwave-assisted synthesis allows getting aggregates of nanoparticles with high crystallinity in good yields, which demonstrated to be a better synthetic route than conventional synthesis in terms of processing facility, short reaction time, and reproducibility. Mesoporous zinc-based luminescent coordination polymer 2 and its free Schiff base linker 1a were fully characterized by Raman, IR-ATR, EDX-FESEM, XRD and XPS techniques. In addition, free Schiff base linker 1a was also characterized by NMR (1H and 13C). The photophysical properties were analyzed in MeOH by UV–Vis and fluorescence spectroscopy revealing that both materials can be classified as semiconductor with fluorescence quantum yield in the 0.13–0.50 range. X-ray diffraction pattern of mesoporous zinc-based luminescent coordination polymer 2 synthetized under microwave irradiation exhibited high crystallinity and thermal analysis indicated that the nanostructures show one molecule of occluded into the polymer layers. The bacterial toxicity and staining studies by epifluorescence microscopy were carried out with the newly synthetized molecules. To the best of our knowledge, this is the first report of new mesoporous zinc(II)−based luminescent coordination polymer with a rigid Schiff base linker as spacer group and applied as bacterial-staining fluorescent probe.