Coordination recognition of differential template units of lanthanide chiral chain.

Coordination-driven self-assembly processes often produce remarkable structures. In particular, self-assembly processes mediated by chiral template units have provided research ideas for analyzing the formation of chiral macromolecules in living organisms. In this study, by regulating the proportion of reaction raw materials in the "one-pot" synthesis of lanthanide complexes, we constructed chiral template units with different coordination orientations. As a result, lanthanide chiral chains connected to different structures were obtained through the self-assembly process of coordination recognition. In particular, driven by coordination, chiral template units with codirectional coordination points (called cis configuration) coordinate solely with cis template units during the self-assembly process to obtain a one-dimensional (1D) chain R-1/S-1 with an "S"-shaped distribution. Moreover, chiral template units with reversed coordination sites (called trans configuration) and twisted chiral template units are connected solely to templates with the same configuration to form a 1D chain R-2/S-2 with an axial helix. A circular dichroism spectrum shows that R-1/S-1 and R-2/S-2 are two pairs of enantiomers. The controllable construction of these two differential 1D chains is of great significance for studying coordination recognition at the molecular level. To the best of our knowledge, this is the first study to construct a 1D lanthanide chain through the self-assembly process of coordination recognition. The assembly process of nucleotides to form a hierarchical structure is simulated. This work provides a vivid example of the controllable synthesis of lanthanide complexes with precise structures and offers a new perspective on the formation process of chiral macromolecules that simulates natural processes.

Assembly of pinwheel/twist-shaped chiral lanthanide clusters with rotor structures by an annular/linear growth mechanism and their magnetic properties.

Although progress has been made in the design and synthesis of chiral lanthanide clusters with pleasing structural connections and special shapes, assembly rules that guide their directional construction are still lacking. We reacted R/S-mandelic acid hydrazide, 2,3-dihydroxybenzaldehyde and DyCl3·6H2O under solvothermal conditions to obtain two octanuclear chirality clusters R-1 and S-1, which are the enantiomers of each other. R/S-mandelic acid hydrazide and 2,3-dihydroxybenzaldehyde underwent an in situ reaction under "one-pot" conditions to generate a monohydrazone-type organic ligand R/S-mandelic acid hydrazide-2,3-dihydroxybenzaldehyde hydrazone (R/S-H2L). Four R/S-H2L ligands captured eight metal-centered Dy(III) ions and presented an annular arrangement, which assembled to form a pinwheel-shaped chiral cluster R/S-1. The benzene rings at the four vertices of R/S-1 can rotate freely as rotors. This is the first discovery of an annular growth mechanism during the self-assembly of lanthanide clusters. By changing the metal salt to Dy(NO3)3·6H2O, two twist-shaped hexanuclear clusters R-2 and S-2, which are the enantiomers of each other were obtained. Four R/S-H2L and two R/S-H3L ligands captured six metal-centered Dy(III) ions, respectively, and were assembled through a linear growth mechanism to form the twist-shaped chiral clusters R/S-2. This is the first time that a linear growth mechanism has been proposed for the directional construction of lanthanide clusters with specific shapes. Circular dichroism results showed that R/S-1 and R/S-2 were both chiral clusters and enantiomers of each other. Magnetic studies showed that both R/S-1 and R/S-2 exhibit obvious single-molecule magnet (SMM) behaviors under zero-field conditions. This work is the first to propose an annular/linear growth mechanism for the design and synthesis of lanthanide clusters and allows the directional construction of chiral lanthanide clusters with special shapes and structural connections.

Tunable photosalient behaviours within coordination polymers via functional molecular prearrangements.

Four Cd(II)/diene coordination polymers (CPs) with similar 1D chain motifs exhibit different photosalient (PS) behaviours in response to UV light. The [2+2] photoreaction between the CC groups within these CPs results in diverse PS behaviours of their crystals with different CC pair arrangements. The interesting PS behaviours of these CPs can be applied in design and fabrication of advanced photoactuating materials.

New structurally diverse photoactive cadmium coordination polymers.

Four structurally diverse coordination polymers 1-4 (CP1-CP4) were designed and constructed from Cd(II) ions and various carboxyl ligands (H2oba, 4,4'-oxydibenzoic acid; H2bpa, (E)-4,4'-(ethene-1,2-diyl)dibenzoic acid; H2pbda, 4,4'-((1,3-phenylenebis(methylene))bis(oxy))dibenzoic acid) and the alkene containing ligand (CH3-bpeb, 4,4'-((1E,1'E)-(2,5-dimethyl-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine). CP1-CP4 possess Cd2 binuclear secondary building units (SBUs). The geometry of the dicarboxylate ligands and the reaction conditions determined the final structure with a variety of motifs. CP1 possesses an interdigitated 2D structure, while CP2 consists of a 1D channel-like motif with isolated CH3-bpeb molecules embedded in the channels. The solid-state structure of CP3 consists of two unique layers interpenetrated to form a 2D + 2D → 2D polycatenated backbone, while a 1D channel-like motif filled by isolated CH3-bpeb molecules was observed for CP4. In all four coordination polymers pairs of CH3-bpeb molecules were bound or encapsulated by the Cd2 secondary building units at an appropriate distance and orientation for solid-state [2 + 2] photodimerization of one pair of CC bonds. Desolvation of CP3 with heat resulted in a decrease in solid-state fluorescence and a slowing of the rate of solid-state photodimerization.

A pyrazolopyrimidine based fluorescent probe for the detection of Cu2+ and Ni2+ and its application in living cells.

A fluorescent sensor L based on a pyrazolopyrimidine core simultaneously detects Cu2+ and Ni2+ ions by photoluminescence quenching, even in the presence of other metal cations. Sensor L possesses high association constants of 5.24 × 103 M-1 and 2.85 × 104 M-1 and low detection limits of 0.043 µM and 0.038 µM for Cu2+ and Ni2+, respectively. The binding stoichiometry ratios of L to Cu2+ or Ni2+ is 1:1 as determined by Benesi-Hildebrand and Job's plots, and by crystal structures. DFT calculations on L-Cu2+ indicated reduced electron donation from the coordinated pyrazolopyridine to the fused pyrimidine and pendant phenyl group which, together with a smaller HOMO-LUMO orbital gap could favour non-radiative decay and explain the observed fluorescence quenching. Sensor L possessed low cytotoxicity and good imaging characteristics for Cu2+ and Ni2+ in living cells, suggesting potential applications for detecting Cu2+ and Ni2+in vivo.