Bispyridinylidenes (BPYs) have emerged as an important class of neutralo rganic electron donors, with redox potentials that vary widely with choice of substituent. Methods to predict the effect of substitution on the redox potential are therefore highly desirable. Here we show that the redox potential of BPYs featuring iminophosphoranos ubstituents (R 3 P = N-), which representt he most reducing class of BPYs, can be predicted basedo n the well-knownT olman electronic parameter(TEP) for the respective phosphine fragment (R 3 P). Moreover,b uilding on earlier work relatingr edox potentials to Hammett-type substituent constants, it is now possible to quantitatively predict s p + values for iminophosphoranos ubstituents from TEP values. Theser esultsp rovide ap ath for precisely tailoringr edoxp otentials of iminophosphorano-substituted BPYs, but also give quantitative descriptors for how these highly versatile iminophosphorano substituents can impactt he properties of any molecular scaffold. Scheme1.Reductions of iodoester 4 to products 5 or 6 in varying isolated yields depending on the strengthoft he OEDused (1, 2,o r3).
Herein, the chemical compatibility of the hydrogel electrolyte in highly alkaline pH was evaluated. Through simple experiments, we demonstrated that the frequently used polymer compound, acrylamide, is not stable at a high pH. The addition of glycerol as a cryoprotectant in highly alkaline hydrogels was also problematic due to the possible base‐initiated decomposition of glycerol to polyglycerols. Hence, a quick and simple one‐pot synthesis of highly alkaline potassium poly(acrylate) hydrogel with 1 vol % glycerol was proposed. The ionic conductivities of the hydrogel are 46.48 mS/cm and 8.67 mS/cm at 22 and −23 °C, respectively. One important benefit from the addition of the cryoprotectant is that the hydrogel sustained its mechanical features at temperatures as low as −80 °C. We also reported here for the first time the diffusion coefficients (D at ∼10−8 cm2/s), ionic mobilities (μ at ∼10−7 cm2/Vs), and ion density (n at ∼10−7 cm−3) of the hydrogel electrolyte used in flexible alkaline batteries.
Invited for this issue's Front Cover is the group of Prof. Anna Ignaszak from the University of New Brunswick (Canada). The cover picture shows the structure of a leakage‐free polymer electrolyte that sustains its ionic conductivity and mechanical resilience at extremely cold temperature. Read the full text of the Research Article at 10.1002/celc.202300113.
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