Anthracene 9-cyanoanthracene

Cyanoanthracene (anthracene-9-carbonitrile) [1210-12-4] M 203.2, m 134-137°. Purified by crystn from EtOH or toluene, and vacuum sublimed in the dark and in an inert atmosphere [Ebied et al. 7 Chem Soc, Faraday Trans 7 76 2170 1980 Kikuchi et al. J Phys Chem 91 574 1987. ... 

For instance, head-head photodimers are predicted from the crystal structures of 9-cyanoanthracene and 9-anthraldehyde, but the head-tail isomer is produced. Craig and Sarti-Fantoni and later others found that photoreactions of 9-cyanoanthracene and 9-anthraldehyde take place at defect sites [96,215], Systematic photochemical and crystallographic studies by Schmidt and co-workers uncovered many cases of substituted anthracenes which behave in an unexpected fashion (Scheme 40) [216,217]. Examples shown in Scheme 40 clearly illustrate that, unlike cinnamic acid derivatives, the stereochemistry of the product dimer from anthracenes cannot be predicted on the basis of crystal packing. An example from the laboratories of Venkatesan is noteworthy in this context [218], Irradiation of crystals of 7-... 

Albini et al. reported that the cross-dimerization of 9-cyanoanthracene with substituted naphthalenes and anthracenes takes place through a significantly polar intermediates and is affected by solvents and substituents [156], The combination of 9-cyanoanthracene and unsubstituted anthracene in CH3CN gave the best result (Scheme 31). Photoirradiation of 9-cyanoanthracene with 1-methylnaphthalene,... 

In contrast to the course of reaction with the parent anthracene, 2,S-dimethyl-2,4-hexadiene has been reported to yield chiefly the photochemically forbidden [4 + 2] cycloadduct (105) when exposed to 9-cyanoanthracene. The rem able variability in periselectivity displayed by these systems has been rationalized in terms of the [arene 1,3-diene] exciplex which is presumably involved in these transformations. Polar exciplexes are descried as leading to [4 + 2] products while less polar exci-plexes are believed to be the precursors of [4 + 4] adducts. Of interest is the observation that cyclohexa-diene provides principally the corresponding [4 + 4] adduct when reacted with both anthracene and 9-cyanoanthracene thus it has been proposed Aat a less polar exciplex is involved in both of these reactions. ... 

Interest in the monomerization of anthracene photodimers continues the head-to-tail dimer (290) (see p. 361) produced by irradiation of 9-cyanoanthracene has been investigated by two groups. " From results of differential scanning calorimetry and emission spectroscopy of cleaved surfaces of partially monomerized single crystals, it is suggested that the first exothermic peak (and the subsequent ones) arises from monomer crystallization in the photodimer host matrix. " Theocharis and Jones have also examined this retroprocess and using single crystal X-ray techniques they have shown that the first step in the solid-state thermal monomerization of this dimer is a... 

When after formation of photoproduct at one of the two sites the crystal was heated and cooled the photoreaction was reversed. We were able to conclude with the help of the packing calculations of sec. 3.2 and other experimental results that those impurity molecules that reacted could not be those that replaced anthracenes in the regular lattice, but must be at dislocations or regions of abnormal packing, where the host and guest were in face-to-face positions. The reaction is thus belongs to the class of the photodimerizations of anthracene, and 9-cyanoanthracene, not of dimers formed topochemically in the normal lattice. 

Photolysis of 9-bromoanthracene in acetonitrile containing triphenylamine is reported to give a complex mixture of products which includes anthracene and 9-cyanoanthracene. 

Cyanoanthracene has a 3-type crystal structure but produces a head-to-tail photodimer. Unlike cinnamic acids and their derivatives, the stereochemistry of the photoproduct dimer from anthracenes cannot often be predicted on the basis of their crystal packing [78]. 9-Methoxyanthracene has a photostable y-type crystal structure. 9-CNA host crystals doped with 9-MeOA form a solid solution, which upon irradiation yield a heterodimer (3> = 0.12). A reaction mechanism via an exciplex is proposed. The exciplex fluorescence was observed [32] ... 

There are several reports this year of photocycloaddition reactions between polycyclic aromatic hydrocarbons and 1,3-dienes. Anthracene (58 R = H) or 9-cyanoanthracene (58 R = CN) give [4 -I- 4] and [4 -I- 2]adducts on irradiation with buta-1,3-diene, but the different product ratios and temperature effects are used to support the previously proposed biradical mechanism for the reaction. Another report from the same group deals with anthracene-hexa-2,4-diene and 9-phenylanthracene-penta-1,3-diene or cyclohexa-1,3-diene systems in the case of 9-phenylanthracene (59) and cyclohexa-1,3-diene, two [2 -I- 2]cycloadducts involving a terminal aromatic ring are isolated, as well as the more usual [4 + 2] and [4 -f- 4]adducts involving the central ring. Irradiation of substituted anthracenes... 

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