Ligand Symmetry Research Articles

Cu-Ni Bimetallic Nanowires with Various Structures Originating from Ni Reduction Kinetics.

Bimetallic nanowires play important roles in the fields of electronics and mechanics. However, their structure types and morphological control methods are limited, especially for systems with low lattice mismatch. Herein, for a Cu-Ni bimetallic system with lattice mismatch ratio less than 2.5%, a novel preparation approach of various Cu-Ni nanowires dominated by Ni(II) reduction kinetics is presented. With the increase of Ni(II) reduction rate, the core-shell Cu@Ni straight nanowires, the asymmetric Cu-Ni nanocurves, and asymmetric Cu-Ni nanocoils can be prepared, respectively. The formation of Cu-Ni nanowires with different structures can be divided into the growth of Cu nanowires and the deposition of Ni. The regulatory effects were revealed by establishing a kinetic model for Ni(II) reduction. For the novel Cu-Ni asymmetrically distributed nanocurves and nanocoils, the formation mechanism was proposed by considering the Cu nanowire bending due to the rearrangement of surface ligand and bending-induced symmetry breaking of Ni(II) reduction.

Systematic investigations of ortho-aryl substitution effect on chain microstructure in nickel-catalyzed long chain α-olefin polymerization and copolymerization with methyl undecenoate

The tuning of branching density and branch-type distribution of the polyolefin through the ligand modification in “chain-walking”-type late transition metal catalysts is highly desired but remains a significant challenge in olefin polymerization. Herein, we performed a systematic investigation on the (co)polymerization of long chain α-olefin (1-octene and 1-decene) by a series of α-diimine Ni(II) catalysts with the varied ligand sterics arising from the number of the ortho-aryl (4-methylphenyl) substituents. The effects of structural variations, mainly including the steric tuning on the ortho-position of N-aryl ring and ligand backbone, steric distribution (ligand symmetry) tuning and electronic tuning, and polymerization conditions on catalytic activities, polymer molecular weight, polymer branching density, and branch-type distribution were described. The steric effect of ortho-methylphenyl substituents played a major role rather than the electronic effect in determining the preference of insertion fashion (1,2-insertion or 2,1-insertion) and chain walking in long chain α-olefin polymerization. As the bulk and number of ortho-methylphenyl substituents increased, the preferred 2,1-insertion and 1, ω-enchainment (chain straightening) were observed even at high monomer concentrations, thus leading to the decrease of branching density as well as the percentage of methyl branches, and eventually affording the semicrystalline “polyethylene-like” polymer with high Tm up to 121 °C and good mechanical properties. Moreover, the tuning of chain microstructure can be achieved over a very wide range through the modification of ligand sterics. Most importantly, these Ni(II) catalysts could copolymerize long chain α-olefin and polar monomer methyl undecenoate (MU) to generate the various functionalized semicrystalline copolymers with high incorporation ratios of MU up to 11% and Tm in a wide range of 5.6–93 °C.

Exploring the Influence of ZnF2 on Zinc-Tellurite Glass: Unveiling Changes in OH Content, Structure, and Optical Properties.

Tellurite glasses have garnered considerable interest as optical host materials due to their advantageous properties, including low processing temperature, high resistance to corrosion and crystallization, and excellent solubility for rare earth ions. However, their applicability in the infrared (IR) region is limited by the absorption of species with distinct vibrations. The incorporation of fluorides has emerged as a promising approach to reduce hydroxyl (OH) absorption during the precursor melting process. In this study, we investigated the influence of ZnF2 on a glass matrix composed of TeO2-ZnO-Na2O, resulting in notable changes in the glass structure and optical properties, with Eu3+ serving as an environmental optical probe. The samples underwent comprehensive structural, thermal, and optical characterization. Structural analyses encompassed 19F and 125Te nuclear magnetic resonance (NMR), with the latter being complemented by mathematical simulations, and these findings were consistent with observations from Raman scattering. The main findings indicate an enhancement in thermal stability, modifications in the Te-O connectivity, and a reduction in emission intensity attributed to the effects of ligand polarizability and symmetry changes around Eu3+. Additionally, the fluorotellurite matrices exhibited a shift in the absorption edge toward higher energies, accompanied by a decrease in mid-IR absorptions, thereby expanding the transparency window. As a result, these glass matrices hold substantial potential for applications across various regions of the electromagnetic spectrum, including optical fiber drawing and the development of solid-state emitting materials.

Heteroatom-Based Diradical(oid)s.

Heteroatom-centered diradical(oid)s have been in the focus of molecular main group chemistry for nearly 30 years. During this time, the diradical concept has evolved and the focus has shifted to the rational design of diradical(oid)s for specific applications. This review article begins with some important theoretical considerations of the diradical and tetraradical concept. Based on these theoretical considerations, the design of diradical(oid)s in terms of ligand choice, steric, symmetry, electronic situation, element choice, and reactivity is highlighted with examples. In particular, heteroatom-centered diradical reactions are discussed and compared with closed-shell reactions such as pericyclic additions. The comparison between closed-shell reactivity, which proceeds in a concerted manner, and open-shell reactivity, which proceeds in a stepwise fashion, along with considerations of diradical(oid) design, provides a rational understanding of this interesting and unusual class of compounds. The application of diradical(oid)s, for example in small molecule activation or as molecular switches, is also highlighted. The final part of this review begins with application-related details of the spectroscopy of diradical(oid)s, followed by an update of the heteroatom-centered diradical(oid)s and tetraradical(oid)s published in the last 10 years since 2013.

On the Single-Molecule Magnetic Behavior of Linear Iron(I) Arylsilylamides.

The rational design of 3d-metal-based single-molecule magnets (SMM) requires a fundamental understanding of their intrinsic electronic and structural properties and how they translate into experimentally observable features. Here, we determined the magnetic properties of the linear iron(I) silylamides K{crypt}[FeL2] and [KFeL2] (L = -N(Dipp)SiMe3; crypt = 4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosan). For the former, slow-relaxation of the magnetization with a spin reversal barrier of Ueff = 152 cm-1 as well as a closed-waist magnetic hysteresis and magnetic blocking below 2.5 K are observed. For the more linear [KFeL2], in which the potassium cation is encapsulated by the aryl substituents of the amide ligands, the relaxation barrier and the blocking temperature increase to Ueff = 184 cm-1 and TB = 4.5 K, respectively. The increase is rationalized by a more pronounced axial anisotropy in [KFeL2] determined by dc-SQUID magnetometry. The effective relaxation barrier of [KFeL2] is in agreement with the energy spacing between the ground and first-excited magnetic states, as obtained by field-dependent IR-spectroscopy (178 cm-1), magnetic measurements (208 cm-1), as well as theoretical analysis (212 cm-1). In comparison with the literature, the results show that magnetic coercivity in linear iron(I) silylamides is driven by the degree of linearity in conjunction with steric encumbrance, whereas the ligand symmetry is a marginal factor.

Improving binding entropy by higher ligand symmetry? - A case study with human matriptase.

Understanding different contributions to the binding entropy of ligands is of utmost interest to better predict affinity and the thermodynamic binding profiles of protein-ligand interactions and to develop new strategies for ligand optimization. To these means, the largely neglected effects of introducing higher ligand symmetry, thereby reducing the number of energetically distinguishable binding modes on binding entropy using the human matriptase as a model system, were investigated. A set of new trivalent phloroglucinol-based inhibitors that address the roughly symmetric binding site of the enzyme was designed, synthesized, and subjected to isothermal titration calorimetry. These highly symmetric ligands that can adopt multiple indistinguishable binding modes exhibited high entropy-driven affinity in line with affinity-change predictions.

Developing Water-Stable Pore-Partitioned Metal-Organic Frameworks with Multi-Level Symmetry for High-Performance Sorption Applications.

A new perspective is proposed in the design of pore-space-partitioned MOFs that is focused on ligand symmetry properties sub-divided here into three hierarchical levels: 1) overall ligand, 2) ligand substructure such as backbone or core, and 3) the substituent groups. Different combinations of the above symmetry properties exist. Given the close correlation between nature of chemical moiety and its symmetry, such a unique perspective into ligand symmetry and sub-symmetry in MOF design translates into the influences on MOF properties. Five new MOFs have been prepared that exhibit excellent hydrothermal stability and high-performance adsorption properties with potential applications such as C3 H6 /C2 H4 and C2 H2 /CO2 selective adsorption. The combination of high stability with high benzene/cyclohexane selectivity of ≈13.7 is also of particular interest.

Improving the Performance of Photocatalytic Hydrogen Production through Adjusting the Size of Defective Quantum Dots Co‐Catalyst Affected by Intramolecular Steric Hindrance on Thermal Stability of Functional Groups

Quantum dots (QDs) co‐catalysts have been extensively studied in the field of photocatalytic hydrogen production (PHP) due to their limited domain effect. However, how to adjust the size of QDs co‐catalysts remains a big challenge. Herein, Ni2P QDs co‐catalysts are synthesized via phosphating metal–organic frameworks (MOFs). Due to the intramolecular steric hindrance on the thermal stability of functional groups: electron‐giving functional groups ‐NH2, ‐OH, and electron‐absorbing functional group ‐COOH, the electronic symmetry of organic ligands and the coordination with metal ions is affected, resulting in three sizes of Ni2P QDs co‐catalysts in the phosphating process, and the smallest one has the highest interfacial charge injection efficiency and transfer rate. Meanwhile, the carbon defects of the carbon skeleton produced in the phosphating process, in which the band position is lower than the conduction band of the Zn0.5Cd0.5S (ZCS) catalyst, can effectively collect electrons and inhibit the recombination of photocarriers to a greater extent, and Ni defects adjust the internal electronic structure of Ni2P QDs. The results of experiments and density functional theory calculations demonstrate that Ni2P@ZCS has excellent electronic structure and electron transfer efficiency. Thus, the best PHP performance of Schottky junctions Ni2P@ZCS is achieved with the combined efforts of QDs co‐catalysts and defects.

Modifier’s influence on spectral properties of dysprosium ions doped lead boro-telluro-phosphate glasses for white light applications

Trivalent dysprosium doped Lead boro-telluro-phosphate glasses were synthesized with varying modifiers such as Li+, Zn2+, Ca2+, Sr2+, and Ba2+ using traditional route of glass preparation (melt quenching). The basic network formation and spectroscopical aspects of the as piped outed glasses was analyzed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), UV–vis-NIR, photoluminescence (PL) and emission decay measurements. The existence of elementary functional groups pertaining to the present glass network was explored through FTIR spectral analysis. Bonding parameters (δ) were found to analyze the bonding nature of the rare earth ions and the surrounding metal ligand site. The optical bandgap, band tailing parameter and Urbach energy was found using Tauc’s method in order to identify the transparent region of the prepared glass samples. Furthermore, the symmetry of ligands around the Dy3+ ions has been explored with absorption spectral data by inspecting the Judd-Ofelt (JO) parameters and oscillator strengths of the as-synthesized samples. The radiative properties for instance branching ratios (βR), stimulated emission cross-section (σP) and lifetime (τR) of the meta stable states are estimated to realize the novel applications. The CIE colour coordinates and Y/B ratio values were estimated employing the photoluminescence spectra, whereas the colour purity and it’s colour correlated temperature (CCT) were determined following the (x,y) values thus confirms the generation of neutral white light emitting ability of the prepped samples. The decay or lifetime analysis shows the well fitted non-exponential behavior of the present Dy3+ doped Lead boro-telluro-phosphate glasses.

Impact of Molecular Symmetry/Asymmetry on Insulin-Sensitizing Treatments for Type 2 Diabetes

Although the advantages and disadvantages of asymmetrical thiazolidinediones as insulin-sensitizers have been well-studied, the relevance of symmetry and asymmetry for thiazolidinediones and biguanides has scarcely been explored. Regarding symmetrical molecules, only one thiazolidinedione and no biguanides have been evaluated and proposed as an antihyperglycemic agent for treating type 2 diabetes. Since molecular structure defines physicochemical, pharmacological, and toxicological properties, it is important to gain greater insights into poorly investigated patterns. For example, compounds with intrinsic antioxidant properties commonly have low toxicity. Additionally, the molecular symmetry and asymmetry of ligands are each associated with affinity for certain types of receptors. An advantageous response obtained in one therapeutic application may imply a poor or even adverse effect in another. Within the context of general patterns, each compound must be assessed individually. The current review aimed to summarize the available evidence for the advantages and disadvantages of utilizing symmetrical and asymmetrical thiazolidinediones and biguanides as insulin sensitizers in patients with type 2 diabetes. Other applications of these same compounds are also examined as well as the various uses of additional symmetrical molecules. More research is needed to exploit the potential of symmetrical molecules as insulin sensitizers.

Ligand-to-metal ratio controls stereoselectivity: Highly functional-group-tolerant, iridium-based, (E)-selective alkyne transfer semihydrogenation

Herein, we present ( E )-selective transfer semihydrogenation of alkynes based on an iridium complex in situ generated from [Ir(COD)Cl] 2 and an unsymmetrical (bearing two different phosphorous centers), ferrocene-based phosphine ligand utilizing formic acid as a hydrogen donor. Interestingly, a ligand-to-metal ratio may be used to control the stereoselectivity of the semihydrogenation process: a ratio of 1:1 iridium to ligand led to the formation of ( Z )-alkene as a major product, whereas a ratio of 1:2 gave exclusively ( E )-alkene. The latter 1:2 catalytic system is distinguished by its unprecedented chemoselectivity and exceptional stereoselectivity, which is substantiated by the broad scope of tested substrates, including natural product derivatives. The intriguing difference in catalytic activity between unsymmetrical and symmetrical ferrocene-based ligands was attributed to divergent coordination and steric hindrance. The presented methodology constitutes a solution to the common limitations of the known catalytic systems for semihydrogenation. • Excellent stereoselectivity and functional-group tolerance • Stereoselectivity controlled by metal-to-ligand ratio • Catalytic activity affected by ligand symmetry Olefins are ubiquitous organic compounds which contain unsaturated double C–C bonds, and they may be found in many natural products and pharmaceuticals. Alkenes isomerism plays a vital role in the biological activity of drugs, to give one example. Thus, selective methods of their synthesis are highly coveted. Herein, we provide an unprecedented alternative to the other known catalytic systems for alkynes semihydrogenation, of which stereoselectivity may be controlled by the metal-to-ligand ratio. The ( E )-selective variant is distinguished by excellent stereo- and chemoselectivity. Reducible and problematic functionalities are tolerated under reductive conditions, and this makes our methodology a perfect tool for the late-stage functionalization of organic compounds. The environmentally friendly character of this catalytic system is proven by its efficiency and chemoselectivity, which allow one to avoid the use of protecting groups and allow the application of formic acid as a green and safe hydrogen donor. An iridium-based catalytic system for ( E )-selective transfer semihydrogenation of alkynes was developed. A unique feature of this method is the possibility of stereoselectivity control by the metal-to-ligand ratio. The catalytic system is distinguished by high functional-group tolerance, making it a valuable tool for organic synthesis. The observed intriguing dependence of ligand symmetry on catalytic activity may pave the way for efficient development of catalysts.

Cyclodextrin-Templated Co(II) Grids: Symmetry Control over Supramolecular Topology and Magnetic Properties.

While inherent complexation properties and propensity for self-organization of cyclodextrins (CDs) render them potentially promising scaffolds of magnetic materials, this research area is still at an embryonic stage. We report on the synthesis and structure characterization of a new sandwich-type complex, [(α-CD)2Co3Li6(H2O)9] (α-1), which represents a smaller analogue of the previously characterized [(γ-CD)2Co4Li8(H2O)12] (γ-1) cluster. A comprehensive structural analysis of α-1 and a careful reinvestigation of γ-1 reveal how the symmetry of CD ligands determines the molecular composition and supramolecular arrangements of Co/Li sandwich-type complexes. Furthermore, the first comparative studies of the magnetic properties in this type of system point to subtle differences in the magnetic behavior of both compounds. The sandwich-type complexes α-1 and γ-1 exhibit field-induced slow magnetic relaxation, defining a new family of magnetic materials with a pillared grid-like supramolecular structure composed of weakly interacting CoII centers forming an SMM.

Magnetic interaction of photoexcited terbium-porphyrin complexes with non-aromatic ligands having different symmetries.

Interaction between the total angular momentum (J) of 4f electrons in lanthanides and the orbital angular momentum (L) of porphyrins in the photoexcited states was investigated by temperature-dependent and magnetic circular dichroism (MCD) for 5,10,15,20-tetraphenylporphyrinato (TPP) terbium(III) complexes with two different non-aromatic ligands i.e. 12-crown-4(1,4,7,10-tetraoxacyclododecane) and 1-aza-12-crown-4(1,4,7-trioxa-10-azacyclododecane). The two cases with different ligands were examined in order to understand how magnetic interaction depends on the symmetry of the non-aromatic ligands. The three absorption bands in the visible region, B(0,0), Q(1,0), and Q(0,0) bands, showed temperature-dependent MCD A term. For each band, the J-L interaction was determined from the simulation-based fitting to experimental ratios. An increase in the magnitude of the J-L interaction was observed when the second ligand was the aza-crown with a lower symmetry. Ab initio RASSCF/RASSI calculations were performed to explore the effect of the difference in the second ligand to the ligand centred excited states and the ligand-field-splitting structure on the metal-centred ground multiplet of J = 6.

Elucidation of the pre-nucleation phase directing metal-organic framework formation

Metal-organic framework (MOF) crystallization is governed by molecular assembly processes in the pre-nucleation stage. Yet, unravelling these pre-nucleation pathways and rationalizing their impact on crystal formation poses a great challenge since probing molecular-scale assemblies and macroscopic particles simultaneously is very complex. Herein, we present a multimodal, integrated approach to monitor MOF nucleation across multiple length scales by combining in situ optical spectroscopy, mass spectrometry, and molecular simulations. This approach allows tracing initial metal-organic complexes in solution and their assembly into oligomeric nuclei and simultaneously probing particle formation. During Co-ZIF-67 nucleation, a metal-organic pool forms with a variety of complexes caused by ligand exchange and symmetry reduction reactions. We discriminate complexes capable of initiating nucleation from growth species required for oligomerization into frameworks. Co 4 -nuclei are observed, which grow into particles following autocatalytic kinetics. The geometric and compositional variability of metal-organic pool species clarifies long-debated amorphous zeolitic imidazolate framework (ZIF)-particle nucleation and non-classic pathways of MOF crystallization. Simultaneous probing of metal-organic complexes, oligomeric nuclei, and MOF particles Metal-organic pool forms as pre-equilibrium with geometry diverse complexes “Nucleation” and “growth” complexes are discriminated, which assemble into nuclei Stable nuclei are observed, growing into MOF particles with autocatalytic kinetics The molecular pathway that governs metal-organic framework formation is challenging to grasp. Filez et al. establish a multi-scale characterization approach combined with theory to link the somewhat different worlds of “molecular” metal-organic ligand assembly and MOF “particle” crystallization.

Ligand symmetry significantly affects spin crossover behaviour in isomeric [Fe(pybox)2]2+ complexes.

The understanding of the correlation between the spin-state behaviour and the structural features in transition-metal complexes is of pronounced importance to the design of spin crossover compounds with high performance. However, the study of the influence of ligand symmetry on the spin crossover properties is still limited due to the shortage of suitable structural systems. Herein we report the magneto-structural correlations of three mononuclear Fe(ii) isomers with respect to their ligand symmetry. In this work, two phenyl-substituted meso and optically pure pybox ligands were employed to construct meso (1), optically pure (2), and racemic (3) ligand types of [Fe(pybox)2]2+ complexes. Their magnetic susceptibilities were measured via temperature-dependent paramagnetic 1H NMR spectroscopy. We fitted the midpoint temperatures of the transition (T1/2) of 260 K for 1(ClO4), 247 K for 2(ClO4), and 281 K for 3(ClO4). The influence of structural symmetry on spin crossover was rationalized through density functional theory calculations. The optimized structures of [Fe(pybox)2]2+ complex cations show that the geometric distortion of the central FeN6 coordination sphere is mainly caused by the steric congestions between adjacent phenyl substituents. In these compounds, there is a distinct correlation that more steric congestions produce larger coordination distortion and favor the electron configuration in the high-spin state, which reflects in the increase of T1/2. Additionally, the influence of the counter anion and lattice solvent on the meso series compounds was inspected. It is revealed that multiple factors dominate the spin-state behaviour in the solid state. This work provides deep insight into the effect of ligand symmetry on the spin transition behaviour in spin crossover compounds. It demonstrates that molecular symmetry should be considered in the design of spin crossover compounds.

Non-Symmetrical Sterically Challenged Phenanthroline Ligands and Their Homoleptic Copper(I) Complexes with Improved Excited-State Properties.

A strategy is presented to improve the excited state reactivity of homoleptic copper-bis(diimine) complexes CuL2 + by increasing the steric bulk around CuI whereas preserving their stability. Substituting the phenanthroline at the 2-position by a phenyl group allows the implementation of stabilizing intramolecular π stacking within the copper complex, whereas tethering a branched alkyl chain at the 9-position provides enough steric bulk to rise the excited state energy E00 . Two novel complexes are studied and compared to symmetrical models. The impact of breaking the symmetry of phenanthroline ligands on the photophysical properties of the complexes is analyzed and rationalized thanks to a combined theoretical and experimental study. The importance of fine-tuning the steric bulk of the N-N chelate in order to stabilize the coordination sphere is demonstrated. Importantly, the excited state reactivity of the newly developed complexes is improved as demonstrated in the frame of a reductive quenching step, evidencing the relevance of our strategy.

Ab Initio Prediction of Metal-Organic Framework Structures

Metal-organic frameworks (MOFs) have emerged as highly versatile materials with applications in gas storage and separation, solar light energy harvesting and photocatalysis. The design of new MOFs, however, has been hampered by the lack of computational methods for ab initio MOF structure prediction, which could be used to inspire and direct experimental synthesis. Here, we report the first ab initio method for the prediction of MOF structures and test it against a diverse set of known MOFs that were chosen for their differences in topology, metal coordination geometry, and ligand binding sites. In all cases, our calculations produced structures that match experiment using only the target composition and ligand molecular structure, proving the versatility of our procedure. The herein presented methodology utilizes the point group symmetry of ligands to enable, for the first time, prediction of MOF structures from first principles, without having to resort to empirical guidelines based on rigid connectivity of nodes and linkers, or to previously determined crystal structures and topologies of known MOFs. This advance provides the first tool to change MOF design from an empirically based process that is based on chemistʼs intuition rooted in literature- or database-established knowledge of node-and-linker connectivity to a more general and theory-driven materials development. This ab initio MOF structure prediction approach, which is here validated on a range of known MOF classes, provides a unique opportunity to explore the phase landscape of MOFs computationally and enables MOF research and development even in case of limited access to laboratory resources, as for example in case of a global pandemic.

Stepwise autophosphorylation regulates biased agonism of the insulin receptor

Insulin is a key regulator of energy metabolism in peripheral tissues but also functions as a growth factor. Insulin binding to the insulin receptor (IR) leads to autophosphorylation of intracellular tyrosine residues, which simultaneously initiates a multitude of signals and functions. In contrast, some artificial (non‐insulin) ligands for the IR result in biased agonism, selectively activating the PI3K/AKT pathway and metabolic effects without activating mitogen‐activated protein kinase (MAPK) pathway and mitogenic effects. However, the precise mechanism of biased agonism at the receptor level remains unclear. The biased agonist IR‐A48 aptamer selectively induces mono‐phosphorylation of Tyr1150 residue (m‐pY1150) in the kinase domain of IR. Hence, we hypothesized that IR autophosphorylation is a stepwise process in which formation of m‐pY1150 represents an intermediate step. To explore this idea, we used hybrid receptors in which insulin can bind only one of the two binding sites of the dimeric receptor. Asymmetric insulin binding selectively induced symmetric m‐pY1150 in both kinase domains. Moreover, the juxtamembrane domain, which interacts with the kinase domain, restricted the full activation of IR, and symmetric m‐pY1150 played a crucial role in the rearrangement of intracellular domains to release this restriction. Our findings demonstrate that the symmetry of insulin binding to a dimeric receptor determines the stepwise autophosphorylation of IR. Furthermore, considering that the degree of ligand symmetry on a receptor depends mainly on ligand concentration, our results suggest that IR may play metabolic‐biased roles in peripheral tissues dependent on local insulin concentrations.Support or Funding InformationThis research was supported by the Global Research Laboratory (GRL) Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (No. NRF‐2016K1A1A2912722).

Redox-switchable ring-opening polymerization by tridentate ONN-type titanium and zirconium catalysts

A study designed to ascertain the impact that ligand symmetry, number of redox-active moieties, and identity of the active metal center have on the catalytic ring-opening polymerization performance of redox-switchable catalysts.

Luminescent lanthanide (Eu(iii)) cross-linked supramolecular metallo co-polymeric hydrogels: the effect of ligand symmetry.

Two lanthanide luminescent naphthyl-dipicolinic amide (dpa) methacrylate monomers for the synthesis of grafted supramolecular co-polymer gels (hydrogels), and their use as additional crosslinks in robust covalently cross-linked HEMA hydrogels is presented; the results demonstrate the importance of the ligand symmetry for the Eu(iii) emission from the hydrogels.