Intramolecular Charge Transfer with Crystal Violet Lactone in Acetonitrile As a Function of Temperature: Reaction Is Not Solvent-Controlled was written by Druzhinin, Sergey I.;Demeter, Attila;Zachariasse, Klaas A.. And the article was included in Journal of Physical Chemistry A in 2013.HPLC of Formula: 1552-42-7 This article mentions the following:
Intramol. charge transfer (ICT) with crystal violet lactone (CVL) in the excited singlet state takes place in solvents more polar than n-hexane, such as Et acetate, THF, and acetonitrile (MeCN). In these solvents, the fluorescence spectrum of CVL consists of two emission bands, from a locally excited (LE) and an ICT state. The dominant deactivation channel of the lowest excited singlet state is internal conversion, as the quantum yields of fluorescence (0.007) and intersystem crossing (0.015) in MeCN at 25 °C are very small. CVL is a weakly coupled electron donor/acceptor (D/A) mol., similar to an exciplex 1(A–D+). A solvatochromic treatment of the LE and ICT emission maxima results in the dipole moments μe(LE) = 17 D and μe(ICT) = 33 D, much larger than those previously reported. This discrepancy is attributed to different Onsager radii and spectral fluorometer calibration. The LE and ICT fluorescence decays of CVL in MeCN are double exponential. As determined by global anal., the LE and ICT decays at 25 °C have the times τ2 = 9.2 ps and τ1 = 1180 ps, with an amplitude ratio of 35.3 for LE. From these parameters, the rate constants ka = 106 × 109 s-1 and kd = 3.0 × 109 s-1 of the forward and backward reaction in the LE ⇄ ICT equilibrium are calculated, resulting in a free enthalpy difference ΔG of -8.9 kJ/mol. The amplitude ratio of the ICT fluorescence decay is -1.0, which signifies that the ICT state is not prepared by light absorption in the S0 ground state, but originates exclusively from the directly excited LE precursor. From the temperature dependence of the fluorescence decays of CVL in MeCN (-45 to 75 °C), activation energies Ea = 3.9 kJ/mol (LE → ICT) and Ed = 23.6 kJ/mol (ICT → LE) are obtained, giving an enthalpy difference ΔH (= Ea – Ed) of -19.7 kJ/mol, and an entropy difference ΔS = -35.5 J mol-1 K-1. The ICT reaction of CVL in MeCN is not barrierless. The ICT reaction time of 9.2 ps is much longer than the mean solvent relaxation time of MeCN (0.26 ps), indicating, in contrast with earlier reports in the literature, that the reaction is not solvent controlled. This conclusion is supported by the observation of double exponential LE and ICT fluorescence with the same decay times. In the experiment, the researchers used many compounds, for example, Crystal violet lactone (cas: 1552-42-7HPLC of Formula: 1552-42-7).
Crystal violet lactone (cas: 1552-42-7) belongs to benzofurans derivatives. Benzofurans are compounds with a planar structure having 10 pi electrons that include the lone pair on oxygen atom, which makes it more susceptible to electrophilic attack. In nature, benzofurans have occupied an important role among the plant phenols & several pharmacologically active compounds.HPLC of Formula: 1552-42-7
Referemce:
Benzofuran – Wikipedia,
Benzofuran | C8H6O – PubChem