35Cl NQR, Crystal Structure, and Pyroelectricity of 2,3-Dichloro-1,4-naphthoquinone

Abstract

Abstract The 35Cl NQR spectra of the two phases (phases I and II) of 2,3-dichloro-1,4-naphthoquinone were studied from 77 to 394 K. The crystal structure determination of the triclinic phase (phase I) was refined by single crystal X-ray diffraction. Phase I crystallizes in the space group C1 i-P1̄. The unit cell (Z = 4) has the dimensions a = 1614.3(4) pm, 6 = 828.1 (3) pm, c = 733.2(3) pm, α = 67.02(1)°, β = 82.55(1)°, γ = 89.77(1)°. In the temperature range 439≦ TI→II/K≦447 a unidirectional phase transition I → II is observed. Phase II is orthorhombic, space group C5 2v-Pb21a. The bond distances d(C-CI) and the 35Cl NQR frequencies correlate quite well according to the theory: v(35Cl) ~ (d(C-CI)) 3- The multiplicity of the 35Cl NQR spectra is discussed. Pyroelectricity studies on phase II are reported. The pyroelectric coefficient depends little on the temperature, 8.3≦px/μCm-2 K-1≦10.7 in 103 ≦T/K≦343.