Electron-Donating Radialenes. Potential Donors for Molecular Organic (Super) Conductors and Ferromagnets
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ELECTRON-DONATING RADIALENES.
POTENTIAL DONORS FOR
MOLECULAR ORGANIC (SUPER)CONDUCTORS AND FERROMAGNETS
YOSHIDA Z. SUGIMOTO T. AND MISAKI Y. Department of Synthetic Chemistry, Kyoto University, Yoshida,
Kyoto 606,
Japan
ABSTRACT
The electron-donating [njradialenes (n=3,4,5) were prepared with the aim of developing both new type of organic (super)conductors and unprecedented organic/molecular ferromagnets.
The charge-transfer
(CT)
complexes of 1,3-dithiole[4]radialene with TCNQ and of 1,3-benzodithiole[4]radialene with TCNQF 4 and DDQ showed comparatively high electrical conductivities in compressed pellets.
The single crystals of PF6 and CIO4
salts of 1,3-benzodithiole[4]radialene
radical cation revealed temperature
change of electrical conductivity characteristic of a semiconductor.
The
magnetic properties of the bis(trifluoroacetate)salt of thioxanthene[3]radialene dication and of the CT complexes of 1,3-benzodithiole[5]radialene with DDQ, TCNQF4, and hexacyanohexamethylenecyclopropane, also investigated from the ESR and/or magnetic susceptibility
were
measurements.
INTRODUCTION
It
seems likely that the creation of novel electron donors having
skeletal structures different from those of the hitherto known systems will be required for ultimate accomplishment of high Tc organic super conductors and organic ferromagnetic materials. cyclic
¶
[n]Radialene is
an unique
system composed of an n-membered ring and n of exocyclic double
bonds [1].
Electron donating [nlradialene,
that is
substituted with n of electron donating groups is
[n]radialene
considered to be a
multi-step redox system exhibiting characteristic electrochemical properties. Of those,
electron-donating [4]radialene will be a donor component
for preparing organic
(super) conductors.
On the other hand,
on HMO
consideration assuming that the molecular symmetry of [niradialene is Cn or higher, odd-numbered radialene can possess a pair of degenerate Mat. Res. Soc. Symp. Proc. Vol. 173. ©1990 Materials Research Society
of
4
HOMO.
Thus electron-donating [3]- and [5] radialenes have a potential as
donor components for preparing organic ferromagnetic materials.
SYNTHESES AND ELECTROCHEMICAL PROPERTIES OF ELECTRON-DONATING [n]RADIALENES
No electron-donating [nlradialene has been reported so far except for tetrakis(N-carboethoxy-4H-pyridin-4-ylidene)cyclobutane ethoxy-4H-pyridenyl[4]radialene)
[2].
(N-carbo-
We tried to synthesize
electron-donating [njradialenes (n=3,4,5) which have stronger electrondonating 1,3-dithiol or thiopyranyl groups than N-carboethoxy-4Hpyridenyl groups.
As a result of our efforts for several years the
following radialenes
were synthesized:
cyclopropane
tetrakis(1,3-dithiol-2-ylidene)cyclobutane
(1) [3],
tris(thioxanthen-9-ylidene)-
tetrakis(1,3-benzodithiol-2-ylidene)cyclobutane (1,3-benzodithiol-2-ylidene)cyclopentane
(3) [5].
synthetic study of 1,3-dithiole[3]radialene radialenes are air-stable, most organic solvents.
(4).
(2b)[4],
(2a)[4],
and pentakis-
We continue our Th
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