Reversible Coordination Polymers Research Articles

Putting Ink into Polyion Micelles: Full-Color Anticounterfeiting with Water/Organic Solvent Dual Resistance.

Anticounterfeiting paintings are usually with limited colors and easy blurring and need to be dispersed in an environmentally unfriendly organic solvent. We report a set of water-based polyion micellar inks to solve all these problems. Upon complexation of reversible coordination polymers formed with rare earth metal ions Eu3+ and Tb3+ and the aggregation-induced emission ligand tetraphenylethylene-L2EO4 with oppositely charged block polyelectrolyte P2MVP29-b-PEO205, we are able to generate polyion micelles displaying three elementary emission colors of red (R) (ΦEu3+ = 24%), green (G) (ΦTb3+ = 7%), and blue (B) (ΦTPE = 9%). Full-spectrum emission and white light emission (0.34, 0.34) become possible by simply mixing the R, G, and B micelles at the desired fraction. Strikingly, the micellar inks remain stable even after soaking in water or organic solvents (ethyl acetate, ethanol, etc.) for 24 h. We envision that polyion micelles would open a new paradigm in the field of anticounterfeiting.

White emission thin films based on rationally designed supramolecular coordination polymers

Rationally designed reversible coordination polymers allow facile mixing of different color components to generate white emission films for specific detection of Cl2.

Supramolecular Virus-Like Nanorods by Coassembly of a Triblock Polypeptide and Reversible Coordination Polymers.

We investigate a new case of a self-assembly-stimulated self-assembly in which a triblock polypeptide is combined with a anionic coordination polymer of a dipicolinic acid bis-ligand, and d- or f- block metal ions like ZnII or EuIII . The polypeptide not only has a silk-like domain that can fold and stack, but also a C-terminal cationic sequence by which it can interact with the supramolecular (coordination) polyanion. In the presence of all three ingredients (polypeptide, bis-ligand, and metal ions), we observe the initiation and slow growth of well-defined metal-containing nanorods of up to 150 nm in length, proving that self-assembly of the polypeptide is triggered by the self-assembly of the coordination polyelectrolyte and vice versa. The particles, which have a striking resemblance to rod-like viruses, are stable up to 1.2 m NaCl, and can be made fluorescent when lanthanides like EuIII are used, showing the potential to exploit functional properties and applications of virus-like supramolecular structures.

Understanding the Structure of Reversible Coordination Polymers Based on Europium in Electrostatic Assemblies Using Time-Resolved Luminescence.

In situ characterization of the structure of reversible coordination polymers remains a challenge because of their dynamic and concentration-responsive nature. It is especially difficult to determine these structures in their self-assemblies where their degree of polymerization responds to the local concentration. In this paper, we report on the structure of reversible lanthanide coordination polymers in electrostatic assemblies using time-resolved luminescence (TRL) measurement. The reversible coordinating system is composed of the bifunctional ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) and europium ion Eu(3+). Upon mixing with the positively charged diblock copolymer poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP41-b-PEO205), electrostatic polyion micelles are formed and the negatively charged L2EO4-Eu coordination complex simultaneously transforms into coordination "polymers" in the micellar core. By virtue of the water-sensitive luminescence of Eu(3+), we are able to obtain the structural information of the L2EO4-Eu coordination polymers before and after the formation of polyion micelles. Upon analyzing the fluorescence decay curves of Eu(3+) before and after micellization, the fraction of Eu(3+) fully coordinated with L2EO4 is found to increase from 32 to 83%, which verifies the occurrence of chain extension of the L2EO4-Eu coordination polymers in the micellar core. Our work provides a qualitative picture for the structure change of reversible coordination polymers, which allows us to look into these "invisible" structures.

The advantage of reversible coordination polymers in producing visible light sensitized Eu(iii) emissions over EDTA via excluding water from the coordination sphere

In this paper, we report on the impact of the structure of ligands on the luminescence enhancement of Eu(III) by directly exciting Eu(III) with visible light in aqueous media. Upon replacing the water molecules that coordinated around a Eu(3+) ion with a ditopic ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) or ethylenediaminetetraacetic acid disodium salt (EDTA), significant luminescence can be obtained. L2EO4 may occupy all 9 coordinating sites of a Eu(3+) ion at proper L2EO4/Eu ratios, whereas EDTA only occupies 6 of them with 3 sites left for water at various EDTA/Eu ratios. These coordinated water molecules quench the fluorescence of EDTA-Eu complexes drastically so that the luminescence is about 30 times lower than that of the L2EO4-Eu system. Furthermore, the negatively charged L2EO4/Eu = 3/2 coordinated complex can be further transformed into coordination 'polymers' by mixing with a positively charged block polyelectrolyte, which forms electrostatic micelles with further enhanced luminescence. The emission of the EDTA-Eu complex is not influenced by the addition of polymers due to the formation of stable small 1 : 1 EDTA-Eu complex which doesn't change with increasing concentration. Our work points out that the L2EO4-Eu system is superior to the EDTA-Eu system in creating visible light sensitized Eu(III) luminescence, and the emission of Eu(III) can be indeed significantly enhanced to an applicable level by excluding all the water molecules in the coordination sphere of Eu(III).

Phase Diagram of Coacervate Complexes Containing Reversible Coordination Structures

Phase separation of coacervate complexes from cationic PDMAEMA [poly(N,N-dimethylaminoethyl methacrylate)] and anionic reversible coordination polymers are studied in the present work. The coordination polymers are formed from zinc and a bis-ligand L2EO4 [1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane] and have variable chain length. The charge mixing ratio and metal-to-ligand ratio, M/L, are varied systematically, and the composition of the two coexisting phases is measured using 1H NMR and ICP-AES. The resulting phase diagram is asymmetric: the coacervate complex phase tolerates an excess of coordination polymer much more than an excess of the homopolymer. Moreover, the coacervate complex tends to choose the right amount of the three components under nonstoichiometric mixing conditions. Both the metal-to-ligand ratio (M/L ≈ 1) and charge ratio (f– ≈ 0.5) in the coacervate phase are around stoichiometry, leaving the excess components in the dilute phase.

Main-chain dynamics in metallo-supramolecular polymers: from solution to elastomeric fibres

Main-chain reversible coordination polymers were formed from bis-platinum pincer complexes 2 and bis-pyridine-terminated poly-THF-bis-Py 1. The properties of the polymers, both in solution and in fibres drawn from solution, are characterised. Structural perturbations that influence the ligand exchange (dissociation) rate of the defining metal–ligand bond have no measurable impact on either the viscosity of the polymer solutions or the ultimate yield behaviour of the fibres.

Stimuli‐Responsive Gels from Reversible Coordination Polymers

Sol–gel switching is triggered by counteranion guest exchange. The secondary structures of reversible coordination polymers can interconvert from a folded helical conformation (gel) into an unfolded zigzag conformation (sol) and back again in aqueous media (see picture).

Stimuli‐Responsive Gels from Reversible Coordination Polymers

Ein Wechsel von Sol zu Gel wird durch den Austausch des als Gast eingeschlossenen Anions ausgelöst. Die Sekundärstrukturen von reversibel gebildeten Koordinationspolymeren wandeln sich in wässrigen Medien ineinander um: von einer gefalteten helicalen Konformation (im Gel) in eine nichtgefaltete Zickzack-Konformation (im Sol) und umgekehrt (siehe Bild).

Water-Soluble Reversible Coordination Polymers: Chains and Rings

The formation of soluble reversible coordination polymers with Zn2+ ions in aqueous solution was studied for two bifunctional ligands, differing in spacer length. Viscosity measurements were used to follow the formation of polymers as a function of the ratio between metal ions and ligands, the total ligand concentration, and the temperature. All the experimental findings could be reproduced and interpreted with a theoretical model that accounts for the formation of chains and rings. At low concentrations and at a 1:1 metal-to-ligand ratio, a large fraction of the ligand monomers are incorporated in small rings, with a small contribution to the viscosity. Rings are less important at higher concentrations or if one of the two components is in excess. The fraction of monomers in chains and rings could be estimated from 1H NMR measurements, which were in good agreement with the model predictions. With increasing temperature, the fraction of monomers in rings decreases. As a result, the reduced viscosity increases with increasing temperature.

Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge-Transfer Complexes and Reversible Coordination Polymers

Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge-Transfer Complexes and Reversible Coordination Polymers

Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge-Transfer Complexes and Reversible Coordination Polymers

Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge-Transfer Complexes and Reversible Coordination Polymers

Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge-Transfer Complexes and Reversible Coordination Polymers

Compared to parent ferrocene, the redox potential of the FeII/FeIII transition is shifted to much more cathodic values in B–N adducts 1·Do and 2·(Do)2 of borylated ferrocenes FcBMe2 (1) and 1,1′-fc(BMe2)2 (2) with pyridine bases Do [Fc: (C5H5)Fe(C5H4); fc: (C5H4)Fe(C5H4); Do: γ-picoline, 4-(dimethylamino)pyridine, N-(n-propyl)-4-(4′-pyridyl)pyridinium hexafluorophosphate]. Electron donation by one single BMe2·Do substituent at the cyclopentadienyl ligand is approximately equal to the positive inductive effect of the five methyl groups in a C5Me5 (cp*) moiety. Using the bidentate nitrogen ligand 4,4′-bipyridine (bipy), the dark-purple dimetallic complex 1·bipy·1 is obtained upon reaction with 2 equiv. of 1. 1·bipy·1 has been structurally characterized by X-ray crystallography. The compound tolerates loss of two electrons at the ferrocene groups, as well as two one-electron reductions at the bipy linker. Dark purple coloured coordination polymers [2·bipy]n are accessible from bipy and 1 equiv. of the diborylated derivative 2. The intense colours of 1·bipy·1 and [2·bipy]n are indicative of charge-transfer interactions between the electron-rich ferrocene fragments and the viologen-like R3B–bipy–BR3 acceptor. Neat, solid [2·bipy]n is thermally stable up to 240 °C, but in the presence of toluene, polymerization is fully reversible at about 85 °C.