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

K. Gnanaguru, N. Ramasubbu, K. Venkatesan, V. Ramamurthy

Research output: Contribution to journalArticle

25 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)355-362
Number of pages8
JournalJournal of Photochemistry
Volume27
Issue number3
DOIs
StatePublished - Dec 1984
Externally publishedYes

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