Synthesis of N,N''''-1,4-tetramethylene Bisspiropyran and Bisspirooxazine Compounds and Their Photochromism

Three photochromic N,N'-1,4-tetramethylene bisspiropyran and bisspirooxazine compounds were synthesized.They have been identified by IR spectra,1H -NMR spectra and elemental analysis;Their melting points have been found higher than those of the corresponding monospirocyclic compounds.The photochromic properties of bisspirocyclic compounds and their ring opening form(merocyanine)were studied.It was found that the heat stability of their ring opening form is higher than that of the corresponding monospirocyclic compounds.