Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 1, pp. 60−67.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © K.K. Kalnin’sh, S.G. Semenov, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 1, pp. 61−67.
OF SYSTEMS AND PROCESSES
Hydrogen Bond in the Excited State
of [18.104.22.168](1,2,4,5)Cyclophane Quinhydrones
K. K. Kalnin’sh
and S. G. Semenov
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
St. Petersburg State University, St. Petersburg, Russia
Received May 27, 2010
Abstract—Intra- and intermolecular hydrogen bond was studied in electron-donor-acceptor complexes in the
excited state. It was shown that low-frequency shifts of electron-transfer bands are correlated with the strength
of the hydrogen bond in the ground electron state. A satisfactory agreement was obtained between the results of
quantum-chemical calculations of [22.214.171.124](1,2,4,5)cyclophane bisquinones and their reduced forms, [126.96.36.199]
(1,2,4,5)cyclophane quinhydrones, with experimental data, and unusual physicochemical properties of quinhydrones
Quinhydrones, crystalline electron-donor-acceptor
(EDA) complexes between quinones and hydroquinones,
exist in the form of stacks of alternating donor
(hydroquinone) and acceptor (quinone) molecules.
The stack interact via a hydrogen bond directed
along the C=O...H–O line in the plane of donor and
acceptor molecules. There is published evidence about
several tens of complexes of the quinhydrone type,
for the most part derivatives of para-benzoquinone,
1,4-naphthoquinone, and the corresponding reduced
forms, for some of which an X-ray diffraction analysis
(XRDA) has been performed [1–3]. A structure of this
kind is characteristics of the so-called phenoquinones
, complexes between phenol and para-benzoquinone
, with an interplanar spacing of 3.16 Å and O...O
H-bond length of 2.74 Å. Large (up to 1.5 eV) low-
frequency shifts of the electron-transfer (ET) bands
and a strictly monomolecular kinetics of the redox
transformation occurring with high activation barriers
are characteristic of quinhydrones [5–7].
Quinones and hydroquinones widely occur in
organic and bioorganic chemistry as both reagents and
products. For example, there is a known coenzyme
ubiquinone, which is present in all, without exception,
human body cells and is involved in electron and proton
transfer processes. In contrast to solid quinhydrones
with a strictly deﬁ ned crystal structure, complexes
supposedly having a plane-parallel arrangement of
quinone and hydroquinone molecules exist in solution.
With a solvent involved, these complexes can form
complex associates. The problem of the spatial structure
of complexes of this kind has not been conclusively
solved and requires further experimental examination.
Of particular interest in this context is examination of
cyclophane quinhydrones, in which the quinoid and
hydroquinoid six-membered rings are spatially ﬁ xed
by four CH
bridges . A more detailed study
of the effect of the C=O...H–O hydrogen bond on the
structure, spectral characteristics, and chemical behavior
of the complexes can be performed for the example of
compounds of this kind.
In this study, we calculated the spatial and electronic
structure of [188.8.131.52](1,2,4,5)-cyclophane quinhydrones,
cyclophane-bisquinones, and the corresponding
complexes with a hydrogen bond. The effect of the
hydrogen bond between a quinhydrone and a third species
on the energy of electron transfer between the donor and
acceptor components of quinhydrone was theoretically