Substituent effects on the stabilities of polymeric and small molecule bis-terpyridine complexes

Henderson, Ian; Hayward, Ryan C.

doi:10.1039/c2py20042b

Cited by 20 publications

(21 citation statements)

References 78 publications

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“…18 The Co(III/II) redox potentials are given in Table 3, and a comparison with other previously reported cobalt bis-terpyridyl systems is given in Figure S66 and Table S4. [18][19] It shows that this class of system can span a broad range of potentials, more than 1 V. As expected, in the C6 -C8 series the Co(III/II) redox potential is shifting to more cathodic values when adding more amino substituents on the tpy ligand. Interestingly, the potential of C6 (+0.53 V) was much more positive than that of R1 (-0.39 V), a previously reported cobalt bis-terpyridyl complex with a N-pyrrolidine at the 4-central position ( Figure S66 and Table S4).…”

Section: Synthesis Of [Co(terpyridyl)2](pf6)2 Complexes the Corresposupporting

confidence: 65%

Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes

et al. 2017

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Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions. The corresponding cobalt(II) complexes were synthesized and fully characterized by elemental analysis, single-crystal X-ray crystallography, mass spectrometry, and UV-vis, H NMR, and Fourier transform infrared (FT-IR) spectroscopy as well as by cyclic voltammetry (CV). Density functional theory (DFT) calculations were performed to investigate the electronic structure of all the Co(II) bis-terpyridyl molecular complexes. In this work, we show that terpyridine ligand functionalization allows tuning the redox potentials of the Co(III)/Co(II), Co(II)/Co(I), and Co(I)/Co(I) (tpy) couples over a 1 V range.

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Section: Synthesis Of [Co(terpyridyl)2](pf6)2 Complexes the Corresposupporting

confidence: 65%

Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes

et al. 2017

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“…The t yields a dissociation rate constant k À2,Co of 1.4 Â 10 À3 s À1 , similar to the value presented in literature for the dissociation rate constant of a Co 2+ complex of a linear terpyridyl endgroup modied PEG (1.5 Â 10 À3 s À1 ). 33 The exchange of Fe 2+ by Ni 2+ ions from the Fe 2+ -bis(terpyridyl) complex proceeds rather slowly and the data could be t according to eqn (1) over at least 6 hours, yielding a dissociation rate constant of 8.1 Â 10 À7 s À1 . This dissociation rate constant is lower than that determined for an Fe 2+ complex of terpyridyl end-group modied linear PEG (5.0 Â 10 À6 s À1 ) but higher than that of an unsubstituted terpyridine (1.6 Â 10 À7 ).…”

Section: Resultsmentioning

confidence: 98%

Hydrogels by supramolecular crosslinking of terpyridine end group functionalized 8-arm poly(ethylene glycol)

et al. 2014

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Metallo supramolecular assemblies of an 8-arm poly(ethylene glycol) partially substituted with terpyridyl end-groups and the transition metal ions Ni(2+), Fe(2+), Co(2+) and Zn(2+) were studied for their nano-particle formation at dilute conditions and gelation at higher concentrations. The large differences in dissociation rate constants of the metal ligand complexes largely determine the assembly behavior. Thermodynamically stable complexes are generated with Ni(2+) and Fe(2+) chlorides, which lead to distinct particle sizes of ∼200 nm in dilute conditions. The Co(2+) and Zn(2+) chlorides provide multiple size distributions revealing that mono and bis-complexes are present at equilibrium. Upon complexation, terpyridyl groups move to the outer sphere giving aggregates with a charged surface. At polymer concentrations above 5 wt%, crosslinking upon addition of transition metal ions provides hydrogels. Elastic hydrogels were obtained with Ni(2+), Fe(2+) and Co(2+) having storage moduli in excess of 20 kPa, whereas Zn(2+) gels are relatively viscous. Only Zn(2+) gels show a thermoreversible sol to gel transition at a temperature of 25 °C independent of polymer concentration.

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“…To provide physical crosslinks with tunable strength and dynamics, we use nitrate salts of manganese(II), zinc(II), cobalt(II), and nickel(II). By introduction of these salts into the precursor solutions, each metal ion complexes to two terpyridine ligands with equilibrium constants that vary in the order of Mn < Zn < Co < Ni . Hoyler et al have shown that the equilibrium constant of complexation with unsubstituted terpyridine increases about two orders of magnitude by going from one ion to the next stronger one in that series .…”

Section: Resultsmentioning

confidence: 99%

Dynamic Model Metallo‐Supramolecular Dual‐Network Hydrogels with Independently Tunable Network Crosslinks

Ahmadi

Seiffert

2020

Journal of Polymer Science

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Hybrid polymer networks emerge between chemical and physical crosslinking, where two different modes of chain connectivity control the material behavior. However, rational relations between their microstructural characteristics, supramolecular kinetics, and the resulting network mechanics and dynamics are not well developed. To address this shortcoming, this study introduces a material platform based on a model dual-network hydrogel, comprising independently tunable chemical and physical crosslinks. The idea is realized by a click reaction between a tetra-PEG and a linear-PEG precursor, whereby the linear block also carries a terpyridine ligand at each end that can form additional physical crosslinks by metal ion-bis(terpyridine) complexation. We change the number of chemical crosslinks by varying the molar mass of the tetra-PEG, and we independently tune the metallo-supramolecular bonds by using different metal ions, Mn 2+ , Zn 2+ , Co 2+ , and Ni 2+ . Based on that modular approach, we study the rheological behavior and the diffusivity of fluorescent polymeric tracers. The dissociation of the metallosupramolecular bonds provides a relaxation step, whose timescale and intensity are quantified by a sticky Rouse model. These two characteristics differ not only depending on the metal ion but also according to the chemical network mesh size, which highlights an interplay between the chemical and physical crosslinks.

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Substituent effects on the stabilities of polymeric and small molecule bis-terpyridine complexes

Cited by 20 publications

References 78 publications

Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes

Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes

Hydrogels by supramolecular crosslinking of terpyridine end group functionalized 8-arm poly(ethylene glycol)

Dynamic Model Metallo‐Supramolecular Dual‐Network Hydrogels with Independently Tunable Network Crosslinks

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