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Crystal Structure, Ultraviolet Spectrum, and Electronic Structure of a Strongly Twisted Push-Pull Ethylene, approaching an Amidinium-Vinylogous Dithioate Zwitterion

Sandstrom, Jan and Stenvall, Kristina and Sen, Nirupa and Venkatesan, Kailasam (1985) Crystal Structure, Ultraviolet Spectrum, and Electronic Structure of a Strongly Twisted Push-Pull Ethylene, approaching an Amidinium-Vinylogous Dithioate Zwitterion. In: Perkin Transactions 2 (12). pp. 1939-1942.

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Abstract

The crystal structure of 1,3-di benzyl -2 - (4,4-dimet hyl- 2,5- bist hioxocyclo hexylidene) imidazolidine (2) shows a twist of 80.8(5)' about the inter-ring bond, which has a length of 1.482(6) A. The near orthogonality of the donor and acceptor parts of this formal push-pull ethylene makes the structure approach that of a zwitterion, as evidenced by bond lengths indicating strong electron delocalization. The acceptor part approaches a vinylogous dithioate structure, the donor part an amidinium system. The U.V. spectrum shows an n + R and a R + R transition, at 51 1 and 41 7.5 nm, respectively; according to CNDO/S calculations these are located entirely in the [S-C-C-C-SI- part. Two bands at shorter wavelength are ascribed to transitions from combinations of the lone-pair orbitals on the sulphur atoms to a n* orbital in the [N-C-N] + part; this is facilitated by the near perpendicularity of the two parts of the molecule.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 22 Jan 2010 06:30
Last Modified: 19 Sep 2010 05:43
URI: http://eprints.iisc.ernet.in/id/eprint/22837

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