The photochemistry of phenanthrene-substituted molecules

Abstract

7'11i.y 1)[1per is cledicoted to PI-ofessor Harry E. G L~I I~I~I~S 0 1 1 file occcr.sio11 of his 65th birtt~rlrlyHOWARD E. ZIMMERMAN and GUO-SHENG WU. Can. J. Chcm. 61, 866 (1983).The photochemistry of 3-methyl-3-(9-phcnanthry1)-1-butene was examined as part of 'an investigation into the effects of having two n chromophores of widely different energies participating in a di-n-methane rearrangement. Wc observed both direct and sensitized reactivity with quantum yiclds = 0.043 and 0.053. Thc primary reaction product from both direct and sensitized photolyses was I, 1-dimethyl-2-(9-phenanthryl)cyclopropan. However, in practice this product was obtained only from sensitized irradiations where it was almost completely unreactive. The triplet reactivity is unusual in that the typical free rotor decay exhibited by triplets does not lead to inhibition of di-n-methane reactivity in this case. This point is discussed. The intersystcm crossing efficiency of the phcnanthryl vinyl mcthanc reactant was obtained from the scnsitization of biacetyl phosphorescence by the phenanthrene derivative at varying biacetyl concentrations. This was +, , , = 0.86. This result and the bracketing relationships signify that essentially all of the direct irradiation rearrangement utilizes T I . In addition, from these experiments, 'k,,,,,,, was determined as 5.8 X 10' s-I. Similarly, 'k, = 250 s-I which is the slowest di-n-methane rearrangement encountered thus far. The rearrangement of the cyclopropane product to form 2-methyl-4-(9-phenanthry1)-I-butene was also investigated. 'I$ was determined to be 0.091 and '41 was determined as 0.00072. Thus the interesting contrast was encountered in which thc di-n-methane rearrangement proceeds from the triplet while the rearrangement of the cyclopropane product proceeds most efficiently from the singlet. HOWARD E. ZIMMERMAN et GUO-SHENG WU. Can. J. Chcm. 61, 866 (1983).On a CtudiC la photochimie du mCthyl-3-(phenanthryl-9-)-3 butene-I comme un aspcct dc la rechcrchc portant sur les effets de la presence de dcux chromophores n d'inergies tres differentes participant h la transposition di-n-mkthane. Nous avons observC les deux rCactivitCs directe et scnsibilisCc avec des rendemcnts quantiqucs +"IK = 0,043 et +SEN" 0,535. Le dimethyl-1, l (phinanthryl-9)-2 cyclopropane et le produit primaire de rCaction h partir de la photolyse directe et de la photolyse sensibiliske. Cependant, en fait, on obtient ce produit uniquement h partir des irradiations faites en presence de photosensibilisateurs oh il est presque complktement inactif. La reactivitk du triplet est inhabituelle en ce sens quc la dksintegration par centrifiguration libre typique exhibee par les triplets ne conduit pas h une inhibition de la r6activitC du di-n-methane dans ce cas. On discute de ce point. On retrouve I'efficacitC du croisement intersystkme du rCactif phCnanthrylvinyl methane h partir de la sensibilisation de la phosphorescence du biacCtyle par le derive du phknanthrene h des concentrations variables de biacCtyle. Cette efficacitk est...

Photochemical Fulleroid to Methanofullerene Conversion via the Di-.pi.-methane (Zimmerman) Rearrangement

“…The rearrangement is efficient for 1 but does not take place for [5,6]C61H2, consistent with the general requirement for the di-n-methane rearrangement that the methane carbon carries substituenk2 Evidently, the intermediate 1,3-diradical of 1 will be stabilized by the phenyl ring. This photochemical interconversion is of potential synthetic interest, especially when a thermal rearrangement of fullerenes is not feasible due to product instability.…”

“…There are t On leave from the Department of Chemical Engineering, Eindhoven University of Technology, The Netherlands. 60 n electrons in the [5,6]methanoannulene 1, and the visible region of its electronic spectrum is almost identical to that of C60 (cf. Figure l), suggesting the same n-bonding.…”

Open-Cage Fullerenes: Synthesis, Structure, and Molecular Encapsulation

“…18 However, during the rearrangement of 6b, the intermediate 9b having an unsymmetrical [6,5] open/ [6,6] closed structure was isolated together with 7b and 8b. 24 The formation of 9b could be explained by the di-pmethane rearrangement; 26,27 a theoretical study supported this mechanism. 28 Isolated 9b converged to a 1:1 mixture of 7b and 8b under bright-light conditions, whereas it reverted to 6b in the dark.…”

Synthetic Aspects of the Di-π-methane Rearrangement

“…“biradical 1”) and electron-withdrawing groups lead to stabilization when so situated. Examples of DPM rearrangements of acyclic, cyclic, and bicyclic 1,4-dienes are collected in Tables −9. ,,,,,9a,−

17

18

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