N HETEROATOMIC EFFECT ON THE PHOTOPHYSICS OF A POLYPHENYL SYSTEM - 2,2'-DIPYRIDYLAMINE

A detailed investigation of the absorption and emission characteristic s of 2,2'-dipyridylamine (DPyA) and diphenylamine (DPA) has been carri ed out in different polar and non-polar solvents at room temperature ( 300 K) and at 77 K. A dramatic change in both the characteristics has been observed in DPyA in comparison with DPA. Measured fluorescence an d phosphorescence lifetimes and critical study of the absorption and e mission spectral data suggest that DPyA is more planar than DPA and it s lowest-energy singlet state is of (1)L(a), type containing a little charge transfer character. Evidence of the presence of a (1)n pi stat e has been found in DPyA on protonation in the binary mixture of water and sulphuric acid at room temperature.