Evolution of Luminescent Supramolecular Lanthanide M_2nL_3n Complexes from Helicates and Tetrahedra to Cubes

Abstract

Lanthanide-containing molecules have many potential applications in material science and biology, that is, luminescent sensing/labling, MRI, magnetic refrigeration, and catalysis among others. Coordination-directed self-assembly has shown great power in the designed construction of well-defined supramolecular systems. However, application of this strategy to the lanthanide edifices is challenging due to the complicated and greatly labile coordination numbers and geometries for lanthanides. Here we demonstrate a sensitive structural switching phenomenon during the stereocontrolled self-assembly of a group of LnL (Ln for lanthanides, L for organic ligands, and n = 1, 2, 4) compounds. Systematic variation of the offset distances between the two chelating arms on the bis(tridentate) ligands dictated the final outcomes of the lanthanide assembly, ranging from LnL helicates and LnL tetrahedra to LnL cubes. Remarkably, the borderline case leading to the formation of a mixture of the helicate and the tetrahedron was clearly revealed. Moreover, the concentration-dependent self-assembly of an unprecedented cubic LnL complex was also confirmed. The luminescent lanthanide cubes can serve as excellent turn-off sensors in explosives detection, featuring high selectivity and sensitivity toward picric acid. All complexes were confirmed by NMR, ESI-TOF-MS, and single crystal X-ray diffraction studies. Our results provide valuable design principles for the coordination self-assembly of multinuclear functional lanthanide architectures.

Host–Guest and Photophysical Behavior of Ti8L12 Cube with Encapsulated [Ti(H2O)6] Species

“…Its molecular structure is featured by ac ubic arrangement with the Ti atoms situateda tt he 8v ertices and Ll igands defining the 12 edges ( Figure 1a). Although many coordination cubes based on transition metal and lanthanide ions have been reported, [35][36][37][38] to the best of our knowledge,t he Ti 8 L 12 in PTC-97 is the first cubic Ti-organic cage. All the Ti atoms are located at an octahedral coordination environmentc omprisingo f three phenol oxygen atoms and three carboxylate oxygen atoms from three different Ll igands;e ach Ll igand bridges two Ti atoms in as ymmetric form.…”

Chiral Self‐Discrimination and Guest Recognition in Helicene‐Based Coordination Cages

“…Beyond their use in enantioselective recognition, chiral cages based on luminescent metal centers have been shown to exhibit unique chiroptical properties. [9,12] With respect to mechanically interlocked coordination cages, [13] reports covering the implementation of homochirality are still scarce, with Hardies dimer of cyclotriveratrylene-based coordination cages serving as a notable example. [14] Since their discovery in 1912, [15] helicenes have been widely studied for properties related to their helical chirality.…”

Photoinduced Energy and Electron Transfer Between a Photoactive Cage Based on a Thermally Activate Delayed Fluorescence Ligand and Encapsulated Fluorescent Dyes

“…[5][6][7][8] Small guest molecules have been shown to be sequestered inside the cavities of these cages and their host-guest interactions have been exploited in diverse applications such as in sensing, 9 for gas storage and purification, 10 and for catalysis. [11][12] In recent years, there has been an increasing exploration of the properties of photoactive supramolecular cages in which at least one component, either the metal ion [13][14][15] or the bridging ligand, [16][17][18] is luminescent. Such cages provide both a high concentration of luminophoric units in known relative orientations and dispositions, and restricted shape and size to govern the host-guest interactions.…”