Acta Crystallographica Section B

Structural Science

Volume 60, Part 3 (June 2004)

Acta Cryst. (2004). B60, 343-349 [doi:10.1107/S0108768104005506]

Packing-dependent photochromism: the case of photoinduced intramolecular proton transfer in 6-(2',4'-dinitrobenzyl)-2,2'-bipyridine

P. Naumov and Y. Ohashi

Abstract: A new photoactive monoclinic polymorph ( [bold gamma] -form) of 6-(2',4'-dinitrobenzyl)-2,2'-bipyridine was obtained from an acetone-methanol solution. The crystal structure was compared with those of two polymorphs reported previously (photoactive orthorhombic [alpha] -form and photoinactive monoclinic [beta] -form) and with structures of related nitrobenzylpyridines to explain the relation between the structure and photochromism. The comparison of the reaction cavities around the reactive pyridyl-benzyl-nitro fragment among the polymorphs and related nitrobenzylpyridines revealed that a crucial factor for photochromic activity is the rotational freedom of the ortho-nitro group in their crystals and its accessibility from the proton-donor and proton-acceptor sites. This is because the ortho-nitro group should rotate around the N-C bond to transfer a proton from the methylene group to the N atom of the pyridine ring.

Online 17 May 2004


	Structure factor file (CIF format) (326.9 kbytes) Contains datablock alpha

	Structure factor file (CIF format) (169.0 kbytes) Contains datablock gamma

Notes:

To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.