The intramolecular cyclization of a number of methoxy-substituted bibenzyls and bis(3-methoxyphenyl)methane was shown to take place upon anodic oxidation in acetonitrile or in media containing trifluoroacetic acid (TFA). Yields are low in the former solvent due to the fact that the cyclized products are more easily oxidized than their precursors and the oxidation products are not stable. In the presence of TFA, the cation radicals derived from the oxidation of the cyclized products are stable and, thus, after reduction the dihydrophenanthrenes or fluorene may be isolated in high yield. Potential step cyclic voltammetry was used to provide evidence that the reactions occur by oxidation to the dication diradicals which couple and eliminate protons. In acetonitrile, voltammetry was used to show that the coupling reaction is markedly sensitive to the conditions and appears to be catalyzed by H30+, in the absence of which no coupling was observed.

The photophysical properties of bimanes (l,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-diones) exhibit two types of behavior in solution. The maximal absorption energies, the maximal emission energies, the quantum yields of fluorescence, and the radiative rate constants all decrease (a) moderately fast with solvent polarities up to the intermediate range and (b) slowly from the intermediate polarity range up to water. The bimanes examined include syn-(hydro,hydro)bimane (1), -sy«-(methyl, fluoro)bimane ( 2), sy«-(methyl,hydro) bimane (3), ^(0)-jy«-(methylene,methyl)bimane ( 4), 5y«-(methyl,chloro)bimane ( 5), and jy«-(methyl,methyl)bimane ( 6). The effects are interpreted in terms of two conformational isomers, "bent" and "quasi-planar", for both the ground and excited states. The magnitude of the solvent sensitivities of the photophysical properties, the nature of the conjugation, and the shapes observed in crystal structures suggest that solvent polarity affects the conformation of the bent conformers. The equilibrium between bent and quasi-planar forms may not vary much with solvent polarity, but the appearance of the emission spectrum changes drastically due to substantial differences in the radiative rates for the two conformers.

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chloroplatinic acid. The mixture was stirred for 16 hr at room temperature. The pentane was removed by distillation through a 24-in. spinning-band column yielding the product, 3.1 g (60g/), bp 102", n S o~ 1.4288 (lit.8 bp 103-105", 122% 1.4340). lt1,2-Trimethyl-l-silacyclohexane (1). 1-(Trichlorosily1)-5-ch1orohexane.-To 20 g (0.16 mol) of 5-chloro-I-hexene in 250 ml of cyclohexane were added 60 g (0.50 mol) of trichlorosilane and 3.6 g of dibenzoyl peroxide catalyst. The temperature of the mixture was maintained at 65' for 90 hr. The solvent and excess trichlorosilane were removed by atmospheric distillation, and the product, bp 110-112° (0.12 mm), was isolated by vacuum distillation. The reaction yield was 21 g (87%). The product was converted to trimethyl-n-hexylsilane for characterization (see below).Trimethyl-n-hexylsilane.-To 50 g of l-(trichlorosilyl)-5chlorohexane was added 50 ml of 3 A4 methylmagnesium bromide in ether. The mixture was stirred at ambient temperature for 1 hr, then poured over cracked ice, and extracted with two 50ml portions of ether. The ether was removed by distillation, and the product, bp 195-197", n Z 5~ 1.4123, was distilled. The 1-(trimethylsily1)-.i-chlorohexane wa5 treated with magnesium in ether, and the resulting Grignard reagent was hydrolyzed with HzO. The product was distilled and shown to be trimethyl-nhexylsilane by comparison of its spectra (nmr, ir) with those of an authentic sample prepared from the reaction of n-hexylmagnesium bromide and trimethyl~hlorosilane.1~Attempted Ring Closure of 1-(Trichlorosilyl)-5-chlorohexane .-To a large excess of -Mg in 500 ml of ether was added 20 g (0.063 mol) of l-(trichlorosilyl)-5-chlorohexane. The mixture was heated at reflux overnight, and then 35 g (0.25 mol) of methyl iodide was added. The mixture wa5 again heated at reflux for