Photophysical Properties of Saturated Amines in Slightly Polar Media. Saturated Ethers

Article abstract of DOI:10.1021/j150612a018

The fluorescence properties of a prototype saturated amine, N,N-diethylmethylamine (DEMA), were examined in diethyl ether and in tetrahydrofuran (THF).In going from a nonpolar medium (n-hexane) to more polar media (diethyl ether and THF), the fluorescence of DEMA undergoes a substantial red shift (292-308-340 nm), along with a diminution in quantum efficiency and an increase in lifetime.The shift in the fluorescence spectrum occurs continuously as the amount of THF in THF/n-hexane mixed solvents in increased.These observations are discussed within the framework of universal and specific interactions.Consideration is also taken of the change in geometry of DEMA in the ground and excited states, and some properties of a "rigid" amine, 1-azabicyclo<2.2.2>octane, are compared and discussed.The question of specific complexation of the amine excited state with the solvent molecules is raised (amine / ether exciplex), and it is concluded on the basis of the properties of aminoether model compounds that a 1:1 exciplex cannot account for the observed photophysical properties.It seems possible that the original view of Muto, Nakato, and Tsubomura that the ether solvent media stabilize the Rydberg or Rydberg-like excited state of the amines may account satisfactorily for the observations.