Dipole moments of singlet and triplet excited states of 4-N,N-dimethylaminobenzonitrile and related compounds and of their solute—solvent exciplexes

✍ Scribed by Robert J. Visser; Petra C.M. Weisenborn; Cyril A.G.O. Varma; Mathijs P. De Haas; John M. Warman

• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 803 KB
• Volume: 104
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(84)85301-4

✦ Synopsis

Changes in dielectric loss at microwave frequencies resulting from UV laser excitation of solutions of 4-N,N-dimethyfaminobsnzonitrile and some of its derivatives in cyclohexane and in lfl-dioxane have been studied. The changes are due to differences between the dipole moments of the sohste in the ground and excited states. ExcipIex formation with 1,4dioxane leads to a reduction of the excited-state dipole moment both where the amino group is restricted to be copIanar and where it is non-coplanar with the aromatic ring of the solute. We did not fmd indications of Iarge moIecuIar polarizabilities of DiMABN which could govern its ffuoresccnce behaviour and we have to reject the suggestion (TICf theory) that twisting of the amino group causes a Iarge increase of the dipole moment of DMABN in the Sr state.