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Structural information from hydrazine radical cation optical absorption spectra

Nelsen, Stephen F. and Tran, Hieu Q. and Ismagilov, Rustem F. and Ramm, Michael T. and Chen, Ling-Jen and Powell, Douglas R. (1998) Structural information from hydrazine radical cation optical absorption spectra. Journal of Organic Chemistry, 63 (8). pp. 2536-2543. ISSN 0022-3263. doi:10.1021/jo9718307.

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Transition energies (Eop) of the nitrogen-centered π,π* absorption of tetraalkylhydrazine radical cations are quite sensitive to twist at the NN bond, nitrogen pyramidality, and mixing of the σ orbitals with the π system. Thirty-one examples for which Eop varies from 63 to 107.5 kcal/mol are discussed with the aid of calculated values (Ecalc) for the 0,0 transition energy using simple (no configuration interaction) neutral-in-cation-geometry calculations on AM1−UHF geometry-optimized radical-cation structures. Significant changes in the difference between Eop and Ecalc are observed for bis-N,N‘-bicyclic systems, which are syn pyramidalized at nitrogen (twist angles near 0°; Eop about 23 kcal/mol larger than Ecalc) and for bis-N,N-bicyclic ones, which are anti pyramidalized (twist angles of 180°; difference about 7 kcal/mol when calculations of 180° structures are employed). Within these classes, changes in Eop caused by changes in pyramidality and σ,π interaction are predicted well by the calculations. The tetraisopropylhydrazine radical cation has λmax = 282 nm, but its tetracyclohexyl analogue shows two transitions, at 276 and 386 nm. This surprising difference is attributed to tetracyclohexylhydrazine radical cation having both untwisted and significantly twisted (estimated twist angle ≈ 44°) forms occupied in solution, although the isopropyl compound only has the untwisted form significantly occupied.

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Ismagilov, Rustem F.0000-0002-3680-4399
Additional Information:Copyright © 1998 American Chemical Society. Published In Issue: April 17, 1998. Received October 3, 1997. We thank the National Science Foundation for partial financial support of this work through Grant No. CHE-9417546 and the National Science Foundation, National Institutes of Health, and the University of Wisconsin for funds used in purchasing the spectrometers and computers used in this work. We are obviously indebted to Timothy Clark, who developed the NCG method and provided us with the software used. We thank Jack Pladziewicz for asking what 31+ showing two absorption maxima means. Supporting Information Available: Crystal data for 2+NO3- (21/22+), 15(AdN)2), 15+TsO-, and 31+Ar4B- (cHx2N)2+), thermal ellipsoid drawings, and crystal coordinates (11 pages).
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University of WisconsinUNSPECIFIED
Subject Keywords:sesquibicyclic hydrazines; lone pairs; x-ray; tetraalkylhydrazine; splittings; dication; nitrogen; syn
Issue or Number:8
Record Number:CaltechAUTHORS:20130821-160728363
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40850
Deposited By: Whitney Barlow
Deposited On:29 Aug 2013 20:23
Last Modified:10 Nov 2021 00:09

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