Coordination Of Alkali Metal Ions Research Articles

Fast room‐temperature self‐healing vitrimers enabled by accelerated associative exchange kinetics

Enhanced dynamicity remains a matter of concern in vitrimer design for fast self-healing materials. In this study, we fabricated pseudo-cyclic vinylogous urethane (VU) vitrimers with accelerated associative exchange kinetics and enhanced mechanical properties based on a bottom-up strategy. Unique cation-templated pseudo-crown ether building blocks were prepared via coordination of alkali metal ions. The resultant pseudo-cyclic VU vitrimers possess higher crosslinking densities and more orderly arranged network topologies than their counterpart vitrimer based on linear building blocks, which were confirmed by swelling experiments and free volume parameters determination. Tensile strength and toughness were significantly improved, which are positively correlated with complexation strength. Furthermore, both stress relaxation and creep recovery experiments demonstrate that pseudo-cyclic vitrimers can undergo more rapidly topological rearrangement due to the synergetic effect of unique pseudo-cyclic structure and alkaline metal salts-promoted catalytic dynamic exchange. Given that the resultant vitrimers exhibit a high-efficient self-healable capability at room temperature. This work contributes to tailor-make fast room‐temperature self‐healing vitrimers via a building block design and expands the potential of vitrimers.

Alkali Metal Ions Dictate the Structure and Reactivity of an Iron(II) Imido Complex.

The presence of redox innocent metal ions has been proposed to modulate the reactivity of metal ligand multiple bonds; however, insight from structure/function relationships is limited. Here, alkali metal reduction of the Fe(III) imido complex [Ph2B(tBuIm)2Fe═NDipp] (1) provides the series of structurally characterized Fe(II) imido complexes [Ph2B(tBuIm)2Fe═NDippLi(THF)2] (2), [Ph2B(tBuIm)2Fe═NDippNa(THF)3] (3), and [Ph2B(tBuIm)2Fe═NDippK]2 (4), in which the alkali metal cations coordinate the imido ligand. Structural investigations demonstrate that the alkali metal ions modestly lengthen the Fe═N bond distance from that in the charge separated complex [Ph2B(tBuIm)2Fe═NDipp][K(18-C-6)THF2] (5), with the longest bond observed for the smallest alkali metal ion. In contrast to 5, the imido ligands in 2-4 can be protonated and alkylated to afford Fe(II) amido complexes. Combined experimental and computational studies reveal that the alkali metal polarizes the Fe═N bond, and the basicity of imido ligand increases according to 5 < 4 ≈ 3 < 2. The basicity of the imido ligands influences the relative rates of reaction with 1,4-cyclohexadiene, specifically by gating access to complex 5, which is the species that is active for HAT. All complexes 2-4 react with benzophenone form metastable Fe(II) intermediates that subsequently eliminate the metathesis product Ph2C═NDipp, with relative rates dependent on the alkali metal ion. By contrast, the same reaction with 5 does not lead to the formation of Ph2C═NDipp. These results demonstrate that the coordination of alkali metal ions dictate both the structure and reactivity of the imido ligand and moreover can direct the reactivity of reaction intermediates.

Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li⁺, Na⁺ and K⁺--peroxide-hydroxide systems.

The alkali metal ions Li(+), Na(+) and K(+) have a profound influence on the stoichiometry of the complexes formed in uranyl(VI)-peroxide-hydroxide systems, presumably as a result of a templating effect, resulting in the formation of two complexes, M[(UO2)(O2)(OH)]2(-) where the uranyl units are linked by one peroxide bridge, μ-η(2)-η(2), with the second peroxide coordinated "end-on", η(2), to one of the uranyl groups, and M[(UO2)(O2)(OH)]4(3-), with a four-membered ring of uranyl ions linked by μ-η(2)-η(2) peroxide bridges. The stoichiometry and equilibrium constants for the reactions: M(+) + 2UO2(2+) + 2HO2(-) + 2H2O → M[(UO2)(O2)(OH)]2(-) + 4H(+) (1) and M(+) + 4UO2(2+) + 4HO2(-) + 4H2O → M[(UO2)(O2)(OH)]4(3-) + 8H(+) (2) have been measured at 25 °C in 0.10 M (tetramethyl ammonium/M(+))NO3 ionic media using reaction calorimetry. Both reactions are strongly enthalpy driven with large negative entropies of reaction; the observation that ΔH(2) ≈ 2ΔH(1) suggests that the enthalpy of reaction is approximately the same when peroxide is added in bridging and "end-on" positions. The thermodynamic driving force in the reactions is the formation of strong peroxide bridges and the role of M(+) cations is to provide a pathway with a low activation barrier between the reactants and in this way "guide" them to form peroxide bridged complexes; they play a similar role as in the synthesis of crown-ethers. Quantum chemical (QC) methods were used to determine the structure of the complexes, and to demonstrate how the size of the M(+)-ions affects their coordination geometry. There are several isomers of Na[(UO2)(O2)(OH)]2(-) and QC energy calculations show that the ones with a peroxide bridge are substantially more stable than the ones with hydroxide bridges. There are isomers with different coordination sites for Na(+) and the one with coordination to the peroxide bridge and two uranyl oxygen atoms is the most stable one.

Lithium-selective phosphine oxide-based ditopic receptors show enhanced halide binding upon alkali metal ion coordination.

Previous work on a ditopic receptor based on a tripodal phosphine oxide core demonstrated preferential enhancement of bromide binding over chloride or iodide in the presence of lithium cation. Current studies on an elongated receptor provide evidence that preferential bromide binding enhancement in the presence of lithium cation is common to this receptor class in general, and that lengthening of the receptor results in an overall increase in halide association. Furthermore, the extended receptor shows a strong preference for Li+ binding in solution.

Single crystal X-ray structure of Lawsone anion: Evidence for coordination of alkali metal ions and formation of naphthosemiquinone radical in basic media

Abstract 2-hydroxy-1,4-naphthoquinone; Lawsone ( Lw ) is a natural compound found in henna leaves. The reaction of lawsone with ‘Na’ metal ( Lw - 1 ), CH 3 COONa ( Lw - 2 ), NaOH ( Lw - 3 ), KOH ( Lw - 4 ), K 2 CO 3 ( Lw - 5 ) and Tris(hydroxymethyl)aminomethane ( Lw - 6 ) were studied. Red orange solids obtained for Lw - 1 to Lw - 6 are characterized by Elemental Analysis, FTIR, 1 HNMR and EPR studies. The results reveal the coordination of alkali metals ‘Na’ and ‘K’ to lawsone anion. The single crystal X-ray structure of Lw - 6 was solved and it crystallizes in triclinic space group P-1 with extensive hydrogen bonding network of C H⋯O, N H⋯O and O H⋯O between cations and anions. Polycrystalline powder X-band EPR spectra of Lw - 1 to Lw - 5 shows signals ∼2.004 at 133 K, while Lw - 6 is EPR silent. The naphthosemiquinone ( NSQ − ) radical formed in Lw - 2 to Lw - 5 , is due to disproportion reaction of catechol and naphthoquinone.

Synthesis and Structures of Alkali Metal Complexes of Isophthalic Acid: The Interplay of Organic Supramolecular Interactions and Flexible Metal Coordination As Structure-Directing Factors

The supramolecular interactions of classical O−H···O hydrogen bonding and aromatic π−π stacking found in the crystal structure of isophthalic acid are retained, with minor modifications, in the structures of its complexes with lithium, sodium, rubidium, and cesium, where stacked hydrogen-bonded ribbons of partially deprotonated isophthalate anions are combined with alkali metal ion coordination. The coordination number increases as expected with cation size, from irregular tetrahedral for Li+, through a mixture of octahedral, trigonal prismatic, and irregular pentacoordinated for Na+, to cubic for Rb+ and Cs+. The arrangement of metal ions around the anions also varies considerably in these structures, despite the relative constancy of the arrangement of anions among themselves. The supramolecular properties of the acid thus have potential for design purposes in complexes of this type.

Effect of Alkali Metal Coordination on Gas‐Phase Chemistry of the Diphosphate Ion: The MH2P2O7− Ions

Systematic experimental and theoretical studies on anionic phosphate species in the gas phase are almost nonexistent, even though they could provide a benchmark for enhanced comprehension of their liquid-phase chemical behavior. Gaseous MH(2)P(2)O(7) (-) ions (M=Li, Na, K, Rb, Cs), obtained from electrospray ionization of solutions containing H(4)P(2)O(7) and MOH or M salts as a source of M(+) ions were structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and theoretical calculations at the B3LYP/6-31+G* level of theory. The joint application of mass spectrometric techniques and theoretical methods allowed the MH(2)P(2)O(7) (-) ions to be identified as having a structure in which the linear diphosphate anion is coordinated to the M(+) ion (I) and provides information on gas-phase isomerization processes in the [PO(3)...MH(2)PO(4)](-) clusters II and the [P(2)O(6)...M...H(2)O](-) clusters IV. Studies of gas-phase reactivity by Fourier transform ion cyclotron resonance (FTICR) and triple quadrupole (TQ) mass spectrometry revealed that the MH(2)P(2)O(7) (-) ions react with selected nucleophiles by clustering, proton transfer and addition-elimination mechanisms. The influence of the coordination of alkali metal ions on the chemical behavior of pyrophosphate is discussed.

Is potential coordination of alkali metal ions to stereodefined polyoxygenated cyclohexanes an adequate driving force for fostering the adoption of axial conformers?

Inositol orthoesters have been developed as precursors to stereodefined hexakis polyoxygenated cyclohexanes. The objective of the study was to determine if all- trans systems could be coaxed by alkali metal ions into adopting the all- axial coordinative features. This high level coordination cannot be matched by epimers whose only option is to experience monocomplexation. Only very low levels of coordination were exhibited in solution by the ligands in question. Electrospray ionization mass spectrometry was also used to evaluate the metal complexation properties of the inositol ligands based on competition experiments involving each ligand and one or more metals.

Coordination of alkali metal ions in ZSM-5: A combined quantum mechanics/interatomic potential function study

The siting and coordination of alkali metal ions (Li+, Na+, and K+) in zeolite ZSM-5 were studied by a combined quantum mechanics/interatomic potential function method, which employed the B3LYP density functional and core–shell model potentials. New interaction parameters for Li+ and K+ ions with the zeolite were parameterized based on ab initio data. Several different sites of extra-framework M+ ions in the ZSM-5 were found and classified. Relative stabilities of particular sites depend (i) on the location of the framework Al atom and (ii) on the size of the alkali metal ion. The Li+ ion preferably occupies the sites on top of the six-membered ring on the channel wall while K+ ion preferably binds on the channel intersection.