A novel photochromic compound (PMCP-TSC) containing NNS hexa-atomic heterocycle was obtained by the reaction of 1-phenyl-3-methyl-4- chloroacetyl-pyrazolone-5 with thiosemicarbazine. The compound has been characterized by elemental analysis, MS, ~1H NMR spectra, IR spectrum and X-ray single crystal diffraction. The photochromic properties and photochemical kinetics of PMCP-TSC have been studied by UV spectra under irradiation of 365 nm light. The crystal belongs to monoclinic system with space group P2_1/c. The unit cell parameters are a = 0.105 10 (2) nm, b = 0.150 61(3) nm, c = 0.993 70(10) nm, β = 107.890(10)°, V = 1.496 9(4) nm~3, Z = 4, D_c = 1.417 Mg/m~3, μ = 0.232 mm~(-1), F (000) = 672, R = 0.033 4, wR = 0.089 6. The crystal structure analysis of photocolored product showed that the photochromic phenomenon was due to photoisomerization from enol form to keto form. Three types of hydrogen bonds [N(1)…O(1), N(1)…O(2), O(1)…O(2)] lead to the formation of supramolecular compound with three-dimensional network structure.

Key words: PHOTOCHROMISM, SUPERMOLECULAR STRUCTURE, PYRAZOLONE P, THIOSEMICARBAZIDE, CRYSTAL STRUCTURE, CONDENSATION REACTION