13C NMR and Electronic Absorption Spectroscopic Studies on the Equilibrium between the Colorless Lactone and the Colored Zwitterion Forms of a Fluoran-Based Black Color Former

Abstract

The equilibrium between the colorless lactone (L) and the colored zwitterion (Z) forms of the fluoran compound 1, which has been widely used as a typical black color former in data-recording systems, has been studied by 13C NMR and electronic absorption spectroscopies. Fluoran 1 showed no visible absorption in aprotic solvents, while a black color appeared in phenolic solvents. The 13C NMR and signal of the spiro carbon of 1 in CDCl3 appeared at 84.2 ppm, indicating that 1 exists substantially as L in aprotic solvents. In phenol d6 at 50 °C, the signal of the spiro carbon in 1 shifted to a lower magnetic field and appeared in the sp2-hybridization region (δ = 162.7), suggesting that in phenol-d6 a cleavage of the C(spiro)–O bond in the lactone ring occurs and that the ring-opened Z form is produced. The equilibrium between L and Z depended strongly on the temperature and solvents. The high temperature and inhibition of the solute (1)–solvent interaction by steric hindrance, self-association and intramolecular chelation of the solvent shifted the L–Z equilibrium toward L. The thermodynamic parameters for the equilibrium reaction in phenolic solvents were also estimated.

A Highly Selective Fluorescent Chemosensor for Pb2+

“…The carbonyl carbon peak in the 13 C NMR spectra moved from 167.5 to 171.5 ppm in CD 3 CN:CDCl 3 (9:1, v/v) when 1.2 equiv of Zn(ClO 4 ) 2 was added (see Supporting Information). The cleavage of the lactone ring in the fluoran-based dye was reported and explained on the basis of the changes in the 13 C NMR spectrum. 10a, In the case of the fluoran-based dye, the spiro carbon in the lactone ring moiety appeared at approximately δ 75−85 ppm and moved to δ ∼160 ppm in the lactone ring-opened structure. 10a, The spiro carbon in 1 appeared at δ 64.7 ppm in CD 3 CN:CDCl 3 (9:1, v/v). When 1.2 equiv of Zn(ClO 4 ) 2 was added, the spiro carbon at δ 64.7 ppm disappeared and moved to δ 150 ppm.…”

Application of Photo Acid Generators for .GAMMA. Rays Detective Materials.

“…1). [3] We expected acid generated by y irradiation would cause this color reaction of fluoran dye la to give lb. In this paper, we report the effectiveness of photo acid generators (2-8) ( Fig.2) for y rays as dosimeter.…”

Preparation of 4,6-Trichloromethyl-2-(p-Acetobiphenyl)-1,3,5-Triazine

“…In PAG system, triazine can produce acid to lead to decomposition or cross-linking of the acid-sensitive materials, so the contrast between the part of the lightened and non-lightened increases as to the visualization and image formation can be realized. In recent years, as the PAG system having a very good chemical amplification effect [7,8], high image sensitivity and record accuracy, increasing attention has been paid on the new class of PAG compounds-substitution of triazine derivatives [9][10][11]. The application of triazine is also a focus in the field of pesticide and the triazine insecticides occpupied a large proportion of the sales market [12].…”