Proton-transfer reactions in the excited state of phenanthrylamines by nanosecond spectroscopy and fluorimetry

Abstract

Proton-transfer reactions in the excited singlet state of phenanthrylamines at 300 K have been studied by means of nanosecond time-resolved spectroscopy and fluorimetry. On the basis of dynamic analyses involving proton-induced fluorescence quenching, the proton dissociation (k,) and association (k,) rate constants and the acidity constants pK,* in the excited singlet state of phenanthrylamines were determined. The pK,* values are discussed theoretically by taking account of their electronic structures. An empirical equation to estimate approximately the correct pK,* values of aromatic amines using data from Stokes shifts and (pK,*),, values (determined by the Forster cycle) is proposed. Isotope effects on the rate constants and pK,* values have also been examined.

A green to blue fluorescence switch of protonated 2-aminoanthracene upon inclusion in cucurbit[7]uril

“…The discrepancy between the two values is in the range commonly observed for aromatic amines, and has been attributed to a number of factors, including assumptions made in the use of the Fo ¨rster's cycle. 20 Applying a method reported for correcting the Fo ¨rster pK a * value for aromatic amines gives a pK a * value of about 4.7, 21,22 in good agreement with the fluorescence titration value.…”

Cucurbit[n]uril Host‐Guest Complexes of Acids, Photoacids, and Super Photoacids

“…Tsutsumi et al . have reported a method for correcting the Förster (p K a *) FC value for aromatic amines which display a large Stoke's shift (Δ E St ): …”

The 2pπ*–3dπ interaction in aromatic silanes. Fluorescence from the 1(2pπ, 3dπ) intramolecular charge-transfer state

“…The fluorescence quantum yields were measured by comparison with a quinine bisulphate 0.05 mol dm-, H,SO, solution (aF = 0.54).31-32 The fluorescence and phosphorescence quantum yields at 77 K were determined from the fluorescence quantum yield of toluene (aF.= 0.29)33 in MP glass at 77 K. The fluorescence response functions were recorded using a Hitachi nanosecond time-resolved fluorimeter (pulse width 1 1 ns) and the convolution method was applied. 34 The phosphorescence lifetimes were measured using a Hitachi MPF 2A fluorimeter or a transient memory (Kawasaki MR-SOE) with a photomultiplier (1 P28).…”

“…The slow decay function Ifm(t) at the delay time t > 40 ns shows a single-exponential decay (20. , ns for 1; 20. ns for 2), and the shape of the Zfm(t) function at t < 40 ns can be determined by the convolution method. 34 The fast decay function Igm(t) is derived by subtraction of Irm(t) from Ifm(t) under ideal conditions. The I ; , (t) function is very close to the lamp function I, (t) of the D, pulser with a 6 function [fig.…”