The title compound, 2,2-bis（4-tertial butyl phenyl） naphthopyran, has been prepared and characterized by means of IR, ^1H NMR and elemental analysis, and its crystal structure was determined with X-ray diffraction in the ring-opened form after hydrolyzation. It belongs to monoclinic, space group P21/c, with a = 14.358（3）, b = 7.6725（15）, c = 24.470（5） А, β= 97.147（4）°, C_33H_36O2, Mr=464.62, V= 2674.8（9）А^3, Z = 4, Dc = 1.154 g/cm^3,μ= 0.070 mm^-1, F（000） = 1000, the final R = 0.0514 and wR = 0.1272 for 5444 observed reflections （I 〉 2σ（I））. X-ray analysis revealed that the C（13）-O（1） bond of the title compound cracks after UV irradiation, the six-membered heterocycles are destroyed, and zwitterionic intermediates come into being. The molecular structure in the ring-opened form is obtained after hydrolyzation. It is infrequent that the single-crystal structure is determined in a ring-opened form. A two-dimensional framework is formed by O-H…O and CAr-H…O hydrogen bonds. The UV-vis spectra show that the title compound exhibits excellent photochromic properties in solutions and polymers.
The title compound 2,2-dithiophene-naphthopyran （C21H14OS2, Mr = 346.44） was synthesized and characterized by IR,^1lH NMR, elemental analysis and single-crystal X-ray diffraction. It belongs to the monoclinic system, space group P21/n, with a = 8.2349（14）, b = 6.1964（11）, c = 32.458（5）A, β= 95.051（3）°, V= 1649.8（5）A^3, Z = 4, Dc = 1.395 g/cm^3,μ = 0.327 cm^-1, F（000） = 720, the final R = 0.0559 and wR = 0.1442 for 3370 observed reflections （I 〉 2σ（I））. X-ray analysis revealed that the interatomic distance of C（13）-O（1） is 1.456（3）A, longer than that of normal C-O bond （1.41 - 1.43 A） in a six-membered heterocycle. The UV-vis spectra of the title compound showed that it exhibits excellent photochromic property in polyester coating and solutions.
