Hence, we tested the sensitized photodimerization of the larger 8 and 9 under the same conditions as 7, leading to yields of, respectively, 45% and 7% (Table ). Clearly, as the degree of twisting in the T1 state increases, the yield of dimers decreases, confirming that the twisting of the larger cyclic 1,3-dienes in their T1 states reduces the efficiency of the photosensitized dimerization. In fact, for 9 the yield is comparable to that of 5. Interestingly, 8 shows a lower yield of dimers than 2 despite having a significantly longer triplet lifetime (~500 vs. 27 ns).