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Comparison of Linear and Cross‐Conjugation from Rates of Vinylheptafulvene Ring‐Closure
Author(s) -
Fjelbye Kasper,
Christensen Trine Nørgaard,
Jevric Martyn,
Broman Søren Lindbæk,
Petersen Anne Ugleholdt,
Kadziola Anders,
Nielsen Mogens Brøndsted
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201403117
Subject(s) - conjugated system , chemistry , photochemistry , absorption (acoustics) , molecule , absorption spectroscopy , kinetics , organic chemistry , polymer , optics , physics , quantum mechanics
The concept of cross‐conjugation has in recent years attracted increasing interest in materials science as well as in the field of molecular electronics as a means to tune the optical properties and molecular conductance of nanoscale devices. In this paper we show how the rate of an electrocyclic reaction, the conversion of vinylheptafulvene (VHF) into dihydroazulene (DHA), is influenced by an electron‐withdrawing p ‐nitrophenyl group separated from the VHF by either cross‐conjugated or linearly π‐conjugated bridging units. A selection of DHA/VHF molecules with ethyne, 1,1‐ and 1,2‐diethynylethene, and 1,3‐butadiyne bridges was prepared by metal‐catalyzed coupling reactions. The effect of the different conjugated spacers on the kinetics of the conversion of VHF into DHA was examined by UV/Vis absorption spectroscopy by monitoring the decay of the VHF absorption. The cross‐conjugated diethynylethene spacer was found to increase the half‐life of the VHF relative to the linearly conjugated spacers.