Multiple Lanthanide Helicate Clusters and the Effects of Anions on Their Configuration

Abstract

Helices are the central structural motif in biological molecules. [1] Except for some familiar helices (single, double, and triple), the plasmid DNA has a cyclic structure, [2] and the biologically significant multi-stranded nucleic acid configuration is quadruplex. [3] Helices and circular helices have been fundamental topological targets for chemical synthesis for the past two decades, and much effort has been made in the design and synthesis of artificial helical molecules. [4] Helicalmetal coordination compounds (helicates), have been extensively investigated; [5] however, the formation of the cyclic helicate, a higher nuclearity variant of the helicate, is conversely less well understood. [6] Controlling the structure of assemblies of helicates is one of the leading challenges for supramolecular chemists. The ingenuity of Lehn and coworkers occupies a prominent position, and they have reported a series of helicates/circular helicates, leading to further improvements in this field. [7] Although this challenging task has been quite successfully accomplished with transition metals, [8] the polynuclear helicates with lanthanides have not been developed to such an extent because of the fact that trivalent lanthanide ions display high kinetic lability and a lack of stereochemical preference. [9] Despite some evolution, the ability to predict and control supramolecular assembly is seriously restricted by the bewildering structuredirecting factors; [10] in particular, the anion-controlled selfassembly of lanthanide helicates is rare.Furthermore, it is necessary to investigate nitrates because of the importance of nitrate ions in environmental and biological systems. Primary nitrate response is the best known nitrate-induced response, in which genes encoding the nitrate assimilatory enzymes and nitrate transporters are rapidly induced by nitrate; moreover, transcriptomic studies have indicated that many other genes for diverse biological processes, including amino acid and nucleic acid metabolism, protein folding, RNA processing, and hormone biosynthesis, could also be rapidly induced or repressed by nitrate. [11] Herein, we discuss the design and synthesis of a flexible dentate-bridging ligand, H 2 L, which has two amide-containing NO 3 tetradentate chelators positioned at the two termini ( Figure 1). This linear amide-containing ligand is highly effective in the construction of supramolecular lanthanide complexes. The self-assembly process depends strongly on anion templates, tetrahedral ClO 4 À and trigonal-planar NO 3 À anions, to induce the formation of novel hexanuclear lanthanum circular helicate and tetranuclear quadruple-stranded helicate complexes, respectively. Moreover, the lanthanum complexes dynamically converted from a circular helicate structure into a quadruple-stranded helicate structure upon NO 3 À anion stimulus, which suggests that NO 3 À is the more potent structure regulator.Adding a solution of La(ClO 4 ) 3 ·6 H 2 O in methanol to a light yellow and transparent solution of H 2 L and LiOH (...

Insight into two unusual stable homomultinuclear copper (II)‐based bis (salamo)‐type complexes

“…[ 35 ] It is noteworthy that new strong vibration peaks of complex 1 were observed at approximately 1102 and 626 cm −1 , which are attributed to the stretching vibration frequencies of free ClO 4 − group, at the same time, strong vibration peaks of free ClO 4 − group were also observed at about 1104 and 624 cm −1 in complex 2 . [ 18 ]…”

“…[ 14,15 ] In addition, they have outstanding performance in supermolecular building and chiral complexes. [ 16–18 ] Under normal circumstances, salen‐type N 2 O 2 ‐donor ligands are synthesized by the condensation of the appropriate diamine with the salicylaldehyde derivative, by gently heating the solution of the two compounds, the imine bond (C=N) is formed very smoothly, [ 19–23 ] but for oligo (N 2 O 2 ) ligands with two or more N 2 O 2 moieties, the relatively high reactivity of the imine bond makes it reversible in solution, and a stable single compound cannot be obtained. [ 24,25 ] In order to overcome the instability of imine bond, last several years, a new kind of salen‐type analogue, salamo‐type (R–CH=N–O–(CH 2 ) n –O–N=CH–R) ligands have been developed, the strong electronegativity of oxygen atoms can significantly affect the electronic properties of the N 2 O 2 cavity and inhibit the reversible reaction of the imine bond.…”

Construction of a Nano‐rectangular Zn(II)‐Yb(III) Complex with Near‐Infrared Luminescent Response towards Metal Ions

“…Construction of heterometallic nanoclusters containing both d‐block metals and lanthanide (III) ions has received much interest during recent years due to their unique optical, electrical and magnetic properties. [ 1,2 ] One useful way to organize individual molecular components into nanosize species is through the coordination self‐assembly between the metal ions and ligands. Fluorescent response for selective detection of metal ions is currently of interest because of its potential application in environment, biology and medicine.…”

Self-assembling of three rare structurally various homomultinuclear CuII complexes derived from a bis(salamo)-based multioxime ligand

“…Coordination chemistry is an important branch of chemistry and is involved many active research fields (Mirza et al, 2018;Liu et al, 2018aLiu et al, , 2019cYamamura et al, 2010;Wang et al, 2012;Duan et al, 2019;Zhang et al, 2020b;Cao et al, 2017). In salen-based ligands [R-CH N-(CH 2 ) n -N CH-R] and their corresponding homometallic and heterometallic complexes, due to their potential application values, intense research in modern coordination chemistry is still ongoing (Bhanja et al, 2020;Maity et al, 2020;Bag et al, 2020;Song et al, 2018;Majumdar et al, 2018;Zhang et al, 2015;Wang et al, 2009;Lo Presti et al, 2010).…”