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Intramolecular Exciplex and Charge Transfer Complex Formations in (9,lO-Dicyanoanthracene)-( CH,),(Naphthalene) Systems' Michiya Itoh,* Tsutomu Mimura, Hideo Usui, and Toshihiko Okamoto Contribution from the Faculty of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan. Received December 19, 1972 Abstract: The intramolecular exciplex fluorescence was observed in two (9,10-dicyanoanthracene)-(CH2)3-
(naphthalene) systems in polar and nonpolar solvents, in which activation energies for the exciplex formations were obtained. Only in the nonpolar solvent was another fluorescence observed in the longer wavelength region below 150°K than the exciplex fluorescence, and it was ascribed to the intramolecular charge-transfer fluorescence between the dicyanoanthracene and naphthalene moieties. Analysis of the temperature dependence of the absorption spectra a t low temperature demonstrates considerably great intramolecular interaction in these systems which exhibit exciplex fluorescence a t room temperature. Determination of the fluorescence lifetime at various temperatures suggests that these two fluorescences are from the individual excited states.
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T matic
here have been numerous investigations a b o u t exciplex formations between singlet excited arohydrocarbons and various amines or other weak electron donors,2 where no electronic interaction between the electron d o n o r and acceptor is detected in the g r o u n d state. Perylene exhibits excimer and also dimer fluorescences i n rigid solution at low temperature. However, few spectroscopic studies of the charge-transfer (CT) interaction between the donor and acceptor i n the g r o u n d state, which f o r m s the exciplex in the excited state, have been reported. Efficiency of the trimethylene g r o u p f o r the intramolecular electronic interaction has been demonstrated i n the excimer f ~ r m a t i o n ,i n~ the , ~ energy transfer and the fluorescence q ~ e n c h i n g , ~and - ~ in t h e CT interaction between stable radicals. Recently, Chandross and Thomas have examined the geometrical requirement for the exciplex formation i n naphthylalkyl amine^.'^ Okada, et al., suggested an ionic character i n the exciplex of (9-anthracene)-(CHz),(N,N-dimethylaniline) systems b y their determination of the solvent effect of t h e exciplex fluorescence, and ( S , - Sl)absorption spectra.I4 We have studied the intramolecular electronic interaction between the d o n o r and acceptor moieties i n the following c o m p o u n d s i 5 both i n t h e g r o u n d and excited (1) A preliminary report was presented at the Japanese Symposium of Molecular Structure and Spectra, Sendai, Oct 1972. (2) N. Mataga and T. Kubota, "Molecular Interactions and Electronic Spectra," Marcel Dekker, New York, N. Y., 1970. (3) J. Ferguson, J. Chem. Phys., 44, 2677 (1966). (4) F. Hirayama, ibid., 42, 3163 (1965). (5) E. A. Chandross and C. J. Dempster, J . Amer. Chem. SOC.,92, 3586 (1970). (6) 0. Schnepp and M. Levy, ibid., 84, 172 (1962). (7) A. A. Lamola, P. A. Leermakers, S. W. Byers, and G. S. Hammond, ibid., 87, 2322 (1965). (8) D. T. Browne, J. Eisinger, and N. J. Leonard, ibid., 90, 7302 (1968). (9) T. G. Scott, R. D. Spencer, N. I. Leonard, and G. Weber, ibid., 92, 687 (1970). (10) M. Itoh and E. M. Kosower, ibid., 89, 3955 (1967); 90, 843 (1968). (11) M. Itoh, ibid., 93, 4750 (1971). (12) M. Itoh, ibid., 94, 1034 (1972); Bull. Chem. SOC.Jap., 46, 821 (1973). (13) E. A. Chandross and H. T.Thomas, Chem. Phys. Lett., 6, 393 (1971). (14) T.Okada, T.Fujita, M. Kubota, S . Masaki, N. Mataga, R. Ide, Y. Sakata, and S. Misumi, ibid., 14, 563 (1972).
Journal of the American Chemical Society
95:13
states, and discussed the excited fluorescent states of both the exciplex and the CT complex. CN I
6N @,a'-and @,pl-DCAN
Experimental Section Syntheses of 1-(9,10-Dicyano-2-anthryl)-3-(naphthyl)propan~. Two l-(9,10-dicyano-2-anthryl)-3-(naphthyl)propanes were synthesized by bromination and cyanation of 1-(2-anthryl)-3-(naphthyl)propanes, which were prepared by the same route as that of the 1,3-dinaphthylpropane~.~ 1-(9,10-Dicyan0-2-anthryl)-3-(2-naphthyl)propane @,P'-DCAN). An alkaline ethanol solution (1 g of NaOH in 200 ml) of 2-formylanthracene (3 g) and 2-acetylnaphthalene (3 g) was stirred under an argon atmosphere. The unsaturated ketone, 1-(2-anthryl)-2-(2naphthoy1)ethylene (l),precipitated from the reaction mixture and was filtered. The yellow unsaturated ketone 1 was recrystallized from benzene-hexane: mp 268"; ir (KBr) 1655, 1595, 743 cm-l; yield 62%. Anal. Calcd for CnHlsO: C, 90.47; H, 5.06. Found: C, 90.74; H, 5.09. A solution of the unsaturated ketone 1 (2.2 g) in tetrahydrofuran (100 ml) was hydrogenated over 5% Pd/C for about 3 hr. The ketone, 1-(2-anthryl)-2-(2-naphthoyl)ethane (2), was obtained as colorless crystals: mp 138 (crystallization from hexane); ir (KBr) 1670, 805, 740 cm-l; yield 70.3%. Anal. Calcd for Cz7HzoO: C, 89.97; H, 5.59. Found: C,
89.74; H, 5.60.
The ketone 2 (1.2 g) was reduced in refluxing (4 hr) diethylene glycol (10 ml) containing hydrazine (2 ml, -95%) and sodium hydroxide (1 8). The mixture was diluted with water and extracted with benzene. The yellow product obtained here was purified through silica gel with benzene-hexane and gave colorless crystals. 1-(2-Anthryl)-3-(2-naphthyl)propane (3) was recrystallized from benzene-hexane: mt, 171"; ir (KBr) 955, 895, 815, 740 cm-I; yield 61.1 %. Anal. Calcd for C2,Hn: C, 93.64; H, 6.36. Found: C, 93.42; H, 6.34. The hvdrocarbon 3 (0.5 g) and bromine (0.36 g ) in carbon tetra~ h l o r i d e ~ ( lml) 8 were'stirred on a water bath
