Topochemical solid state photodimerization of non-ideally oriented monomers: 7-chlorocoumarin and 7-methoxycoumarin

Gnanaguru, K. ; Ramasubbu, N. ; Venkatesan, K. ; Ramamurthy, V. (1984) Topochemical solid state photodimerization of non-ideally oriented monomers: 7-chlorocoumarin and 7-methoxycoumarin Journal of Photochemistry, 27 (3). pp. 355-362. ISSN 0047-2670

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Official URL: http://www.sciencedirect.com/science/article/pii/0...

Related URL: http://dx.doi.org/10.1016/0047-2670(84)80051-9

Abstract

Photodimerizations of 7-chlorocoumarin and 7-methoxycoumarin in the solid state were studied; syn head-to-head and syn head-to-tail dimers are the respective products of irradiation in the solid state. X-ray crystal structure analyses of 7-chlorocoumarin and 7-methoxycoumarin reveal unusual features. 7-Chlorocoumarin is arranged in a β-type packing, the centre-to-centre distance between the reactive double bonds being 4.454 Å, which lies outside the limit accepted at present of 3.5 - 4.2 Å. In contrast, the reactive double bonds of 7-methoxycoumarin are rotated by about 65° with respect to each other with the centre-to-centre distance between the double bonds being 3.83 Å. In spite of these unfavourable arrangements photodimerization of these two coumarins in the solid state occurs through a topochemical process with large dimer yields.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
ID Code:90001
Deposited On:04 May 2012 05:15
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