The photophysical properties of molecules with triple bonds

1. The relative contribution of the triple bond to conjugation in the tert-butyl derivtives of tolan, diphenylacetylene, 4-tert-butyl-4′-(phenylethynyl)biphenyl, and 1,4-bis(p-tert-butylphenylethynyl) benzene is comparable with the contribution from a double bond or a phenyl ring. 2. The introduction of a phenyl ring into compounds with triple bonds leads to an increase in the fluorescence. 3. The reduction in the phosphorescence lifetime resulting from the increase in the number of triple bonds in the molecule is the result of an increase in the constant for the radiationless triplet-singlet transition.