Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4′-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4′,4′′-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

A series of novel mono- and binuclear arene–ruthenium­(II) complexes [(p-cym)­Ru­(L)­Cl] containing 11H-indeno­[1,2-b]­quinoxalin-11-one derivatives or tryptanthrin-6-oxime were synthesized and characterized by X-ray crystallography, IR, NMR spectroscopy, cyclic voltammetry, and elemental analysis. Theoretical calculations invoking singlet state geometry optimization, solvation effects, and noncovalent interactions were done using density functional theory (DFT). DFT calculations were also applied to evaluate the electronic properties, and time-dependent DFT was applied to clarify experimental UV–vis results. Cytotoxicity for cancerous and noncancerous human cell lines was evaluated with cell viability MTT assay. Complexes demonstrated a moderate cytotoxic effect toward cancerous human cell line PANC-1. The catalytic activity of the complexes was evaluated in transfer hydrogenation of aryl ketones. All complexes exhibited good catalytic activity and functional group tolerance.

Solvothermal reaction of 5,5′‐(pyridine‐2,6‐diylbis(oxy))diisophthalic acid (H4L) with europium(III) or terbium(III) nitrates in acetonitrile‐water (1 : 1) at 120 °C gave rise to isostructural 2D coordination polymers, [Ln(HL)(H2O)3]∞ (NIIC‐1‐Eu and NIIC‐1‐Tb), the layers of which are composed by eight‐coordinated lanthanide(III) ions interconnected by triply deprotonated ligands HL3−. The layers are packed in the crystal without any specific intermolecular interactions between them, allowing the facile preparation of stable water suspensions, in which NIIC‐1‐Tb exhibited top‐performing sensing properties through luminescence quenching effect with exceptionally low detection limits towards Fe3+ (LOD 8.62 nM), ofloxacin (OFX) antibiotic (LOD 3.91 nM) and cotton phytotoxicant gossypol (LOD 2.27 nM). In addition to low detection limit and high selectivity, NIIC‐1‐Tb features fast sensing response (within 60–90 seconds), making it superior to other MOF‐based sensors for metal cations and organic toxicants. The photoluminescence quantum yield of NIIC‐1‐Tb was 93 %, one of the highest among lanthanide MOFs. Mixed‐metal coordination polymers NIIC‐1‐EuxTb1−x demonstrated efficient photoluminescence, the color of which could be modulated by the excitation wavelength and time delay for emission monitoring (within 1 millisecond). Furthermore, an original 2D QR‐coding scheme was designed for anti‐counterfeiting labeling of goods based on unique and tunable emission spectra of NIIC‐1‐Ln coordination polymers.