X -band electron spin resonance (ESR) spectra of S3− radicals in ultramarine analog (pigment) prepared from zeolite A and maintaining the original structure of parent zeolite were recorded in the temperature range of 4.2–380 K. Electron spin echo experiments (echo detected ESR, electron spin-lattice relaxation, and spin echo dephasing) were performed in the temperature range of 4.2–50 K. The rigid lattice g factors are gx=2.0016, gy=2.0505, and gz=2.0355, and they are gradually averaged with temperature to the final collapse into a single line with g=2.028 above 300 K. This is due to reorientations of S3− molecule between 12 possible orientations in the sodalite cage through the energy barrier of 2.4 kJ/mol. The low-lying orbital states of the open form of S3− molecule having C2v symmetry are considered and molecular orbital (MO) theory of the g factors is presented. The orbital mixing coefficients were calculated from experimental g factors and available theoretical orbital splitting. They indicate that the unpaired electron spin density in the ground state is localized mainly (about 50%) on the central sulfur atom of S3− anion radical, whereas in the excited electronic state the density is localized mainly on the lateral sulfur atoms (90%). A strong broadening of the ESR lines in directions around the twofold symmetry axis of the radical S3− molecule (z-axis) is discovered below 10 K. It is due to a distribution of the S–S–S bond angle value influencing mainly the energy of the B22-symmetry MO. This effect is smeared out by molecular dynamics at higher temperatures. A distribution of the g factors is confirmed by the recovery of the spin system magnetization during spin-lattice relaxation measurements, which is described by a stretched exponential function. Both the spin-lattice relaxation and electron spin echo dephasing are governed by localized phonon mode of energy of about 40 cm−1. Thus, the anion-radical S3− molecules are weakly bonded to the zeolite framework, and they do not participate in the phonon motion of the host lattice because of their own local dynamics.

Imidazole embedded in molecular sieves shows remarkable and steady proton conductivity (>1 × 10⁻⁵ S cm⁻¹ above 360 K). It can be considered to be a promising solid high proton conducting electrolyte for fuel cells. The conductivity depends on imidazole loading and mobility, which result from the pore geometry, the chemical nature of matrices and the preparation method.