Sudden Polarization in the Zwitterionic Z₁ Excited States of Organic Intermediates. Photochemical Implications

Abstract

co= 7.23 a] are comparable with those of the compounds cited.

Solvent Induced Charge Separation in the Excited States of Symmetrical Ethylene: A Direct Reaction Field Study

“…This is known as the zwitterionic (Z) state. In contrast, the associated higher (V) state, 1 (c 3 a 2 -c 4 b 2 ) with c 3 * c 4 , is destabilized by the same effect. Hence, there is a tendency to reduce the dipole moment when the molecule is on this potential surface.…”

The Sudden‐Polarization Effect and its Role in the Ultrafast Photochemistry of Ethene

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The term "sudden polarization", which describes the charge separation in excited singlet states of twisted polyenes, especially of ethene, was introduced in the mid-1970s by Salem.[1] The ionic character and the easy polarizability of these valence excited states of alkenes upon a small perturbation was pointed out as early as 1971 by Wulfman and Kumei.[2] Bonačić-Koutecký et al, [3] in the mid-1970s, were the first to perform an ab initio study of the charge separation in 908-twisted ethene as a function of an internal perturbation: the one-sided pyramidalization of a CH 2 group (D 2d geometry). To our knowledge, all the following studies of the sudden-polarization effect of ethene considered only onesided pyramidalization.

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Photochemistry of alkenes. 9. Medium-sized cycloalkenes

“…There remains a third alternative, which is consistent with the available data, that ether 25 arises via protonation of the '(n,n*) state, which is thought to have dipolar character once it has relaxed to an orthogonal geometry (17). Protonation of this state does not normally occur because internal conversion to the ground state and relaxation to the E or Z isomer is generally more rapid than intermolecular trapping.…”