Primary‐Colored Electrochromism of 1,4‐Phenylenediamines

Abstract

Ten 1,4‐phenylenediamines were studied using electrochemical techniques (voltammetry and controlled potential electrolysis) and UV/Vis spectroscopy under ambient conditions. All compounds demonstrated vibrant color changes upon one‐electron electrochemical oxidation in acetonitrile, with most displaying a primary color (red, green, blue, or yellow) in their oxidized state. The four electrochromes that exhibited the most intense color changes were examined by using a gold micromesh electrode laminated inside a polymer film to determine their electrochromic properties in solution (contrast ratios, chromatic efficiency, and cycle life). Their colored radical cations were also characterized by electron paramagnetic resonance spectroscopy as well as monitored for color retention over a period of 24 hours. Notably, only relatively small potentials were required to initiate the chromatic changes and the oxidized forms of the compounds were long‐lived and unaffected by atmospheric oxygen or moisture.

Green‐Light Activation of Push–Pull Ruthenium(II) Complexes

“…For the aromatic amines, the higher K SV of TMPA correlates to its lower TMPA/TMPA . + redox potential (−0.27 V vs. ferrocene) than that of p ‐toluidine (+0.34 V vs. ferrocene). With the excited‐state lifetime of 477 ns of 2 2+ , the quenching rate constants of the amines amount to k q =0.005×10 9 , 0.19×10 9 and 5.91×10 9 m −1 s −1 for DIPEA, p ‐toluidine and TMPA, respectively.…”

Using Voltammetry to Measure the Relative Hydrogen‐Bonding Strengths of Pyridine and Its Derivatives in Acetonitrile

“…Phenylenediamines have been widely used as dyes, [3] antioxidants in rubber and fuels, [4] organicm aterials in spin electron-ic [5] and electrochromic [6] devices and in the detection of ammonia, [7] chlorine, [8] paracetamol [9] and metal cations, [10] all of which are based on their electroactivity.I na cetonitrile (CH 3 CN), [11] phenylenediamines generally undergot wo chemically reversible 1e À -oxidation reactions with the neutral compound( P) first oxidized to the radicalc ation (P · + )a tp otential E P ox (1) and thereafter into the quinonediimine dication (P 2 + )a t am ore positive potential E P ox(2) (Scheme 1a nd Figure 1). [6,12] The neutral compound Pl argely behaves as aw eak base and so preferentially functions as ah ydrogen acceptort hrough the lone pairs of electrons on its nitrogen atoms, but can also serve as ah ydrogen donor via the hydrogen atoms of the amino groups. The oxidized forms P · + and P 2 + ,o nt he other hand, tend to behave as hydrogen donors with the latter being more acidic and as tronger donor because of its greater positive charge.…”

Impurities in Nitrile Solvents Commonly Used for Electrochemistry, and their Effects on Voltammetric Data

“…The overall voltammetry of N , N ′‐di‐2‐napthyl‐1,4‐phenylenediamine and N , N , N ′, N ′‐tetraphenyl‐1,4‐phenylenediamine in a 1:1 MeCN/toluene solvent mixture was reported to be unchanged from the EE oxidation behavior of other phenylenediamines recorded in MeCN, and it was not expected that any nitrile impurities would behave differently from MeCN. Therefore, it appears that 2‐methyl‐2‐pentenal might be responsible for some of the observed differences, to which its amount in the solvents were accurately quantified with the use of a high‐purity standard and shown in parenthesis in Table .…”