Unusual twisted intramolecular charge transfer processes of 4,4′-diaminodiphenylsulfone in β-cyclodextrin: A study by electronic spectra

Abstract

Analysis of the absorption and fluorescence characteristics of 4,4′-diaminodiphenylsulfone (4DADPS) in aqueous β-cyclodextrin (β-CDx) solution under different acidic conditions reveals that: (i) the twisted intramolecular charge transfer state (TICT) is more populated than the locally excited (LE) state of 4DADPS in β-CDx; and (ii) the protonation of the monocation of 4DADPS in the S0 and S1 states in β-CDx requires more acidic conditions than in the absence of β-CDx. The higher stabilisation of the TICT state compared to the LE state of 4DADPS in β-CDx inclusion complex is contrary to normal observation. This anomalous behaviour is explained by the geometry of the 1: 1 inclusion complex.