The parama
gnetic and chiral anion [Fe(C
5O
5)
3]
3- (C
5O
52- = croconate) has been combined with the or
ganic donorBEDT-TTF (=ET = bis(ethylenedithio)tetrathiafulvalene) to synthesize a novel parama
gnetic semiconductor withthe first chirality-induced
ges/
gifchars/alpha.
gif" BORDER=0> phase,
ges/
gifchars/alpha.
gif" BORDER=0>-(BEDT-TTF)
5[Fe(C
5O
5)
3]·5H
2O (
1), and one of the few known parama
gneticmolecular metals,
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">-(BEDT-TTF)
5[Fe(C
5O
5)
3]·C
6H
5CN (
2). Both compounds present layers of BEDT-TTF molecules,with the
ges/
gifchars/alpha.
gif" BORDER=0> or
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle"> packin
g modes, alternatin
g with layers containin
g the hi
gh-spin
S = 5/2 Fe(III) anions and solventmolecules. In the
ges/
gifchars/alpha.
gif" BORDER=0> phase, the alternation of the chiral [Fe(C
5O
5)
3]
3- anions alon
g the direction perpendicular tothe BEDT-TTF chains induces an alternation of the tilt an
gle of the BEDT-TTF molecules,
givin
g rise to the observed
ges/
gifchars/alpha.
gif" BORDER=0> phase. The
ges/
gifchars/alpha.
gif" BORDER=0> phase presents a semiconductor behavior with a hi
gh room-temperature conductivity (6 S·cm
-1)and an activation ener
gy of 116 meV. The
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle"> phase presents a metallic behavior down to ca. 120 K, where achar
ge localization takes place with a reentrance to the metallic state below ca. 20 K followed by a metal-semiconductor transition at ca. 10 K. The ma
gnetic properties are dominated by the parama
gnetic
S = 5/2[Fe(C
5O
5)
3]
3- anion with an extra Pauli-type parama
gnetism in the metallic
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle"> phase. The ESR spectra confirm thepresence of the hi
gh-spin Fe(III)-containin
g anion and show a pro
gressive localization in the or
ganic sublatticealon
g with an antiferroma
gnetic couplin
g below ca. 120 K that, in the metallic
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle"> phase, could be at the ori
gin ofthe transition from the metallic to the activated conductivity re
gime. The correlation between crystal structure andconductivity behavior has been studied by means of ti
ght-bindin
g band structure calculations which provide arationalization of the char
ge distribution and conductivity results.