NQR Spectroscopy and Structure of Photochromic 2,3,4,4‐Tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline and 2,4,4‐Trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide

Abstract

The 35Cl NQR spectra of the photochromic compounds 2,3,4,4‐tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline. β‐TKN, and 2,4,4‐trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide, TCNS, were studied from 77 K to the decomposition temperature. The crystal structure of TCNS was determined, space group C‐P21/m, Z = 2, a = 818.3(2) pm, b = 828.0(2) pm, c = 905.4(2) pm, β = 107.552(2)°, σcalc = 1.752 Mg · m−3. No phase transition is observed for the two title compounds in the temperature range of the 35Cl NQR spectroscopy. The 35Cl NQR spectra are discussed in connection with the crystal structures. — For a few other compounds related to the photochromic ones, 2,2,3,4‐tetrachloro‐1‐oxo‐1,2‐dihydronaphthaline (α‐TKN), 2,3,4,4,5,6‐hexachloro‐cyclohexadiene‐(2,5)‐one‐(1) (HCP), 2,2,3,4,4‐pentachloro‐1‐oxo‐1,2,3,4‐tetrahydronaphthaline, and 2,3,4‐trichloro‐1‐naphthol, results of NQR spectroscopy are given, too.