Structure effect on photochromic mechanism of spirooxazines

Structure effect on photochromic mechanism of 1,3,3 -trimethylspiro[indolin e-2,3'-[3H]naphtho[2,1,-b][1,4]oxazine] (SP1), 1,3-Dimethyl-3,2'-(1,2' -pro pylene)spiro[indoline-2,3'-[3H] naphtho[2,1-b][1,4]oxazine] (SP2) and 1,2'- (1,3-propylene),3,3-dimethylspiro[indo- line-2,3' [3H]naphtho[2,1-b][1,4]ox azine](SP3) have been studied by nanosecond laser photolysis. Because of di fferent connective positions of 1,3-propylene group in SP2 and SP3, the pho tochromic behaviours of them are quite different. One photoproduct of SP2 w as only detected, and its lifetime is about 0.15 mu s. However, two colored forms of SP3 were detected after UV irradiation. The lifetimes of them are much longer than that of C-SP2. The semiempirical computational results by AMI method were coincided with the experimental results.