The paramagnetic and chiral anion [Fe(C
5O
5)
3]
3- (C
5O
52- = croconate) has been combined with the organic donorBEDT-TTF (=ET = bis(ethylenedithio)tetrathiafulvalene) to synthesize a novel paramagnetic semiconductor withthe first chirality-induced
![](/images/gifchars/alpha.gif)
phase,
![](/images/gifchars/alpha.gif)
-(BEDT-TTF)
5[Fe(C
5O
5)
3]·5H
2O (
1), and one of the few known paramagneticmolecular metals,
![](/images/gifchars/beta2.gif)
-(BEDT-TTF)
5[Fe(C
5O
5)
3]·C
6H
5CN (
2). Both compounds present layers of BEDT-TTF molecules,with the
![](/images/gifchars/alpha.gif)
or
![](/images/gifchars/beta2.gif)
packing modes, alternating with layers containing the high-spin
S = 5/2 Fe(III) anions and solventmolecules. In the
![](/images/gifchars/alpha.gif)
phase, the alternation of the chiral [Fe(C
5O
5)
3]
3- anions along the direction perpendicular tothe BEDT-TTF chains induces an alternation of the tilt angle of the BEDT-TTF molecules, giving rise to the observed
![](/images/gifchars/alpha.gif)
phase. The
![](/images/gifchars/alpha.gif)
phase presents a semiconductor behavior with a high room-temperature conductivity (6 S·cm
-1)and an activation energy of 116 meV. The
![](/images/gifchars/beta2.gif)
phase presents a metallic behavior down to ca. 120 K, where acharge 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 magnetic properties are dominated by the paramagnetic
S = 5/2[Fe(C
5O
5)
3]
3- anion with an extra Pauli-type paramagnetism in the metallic
![](/images/gifchars/beta2.gif)
phase. The ESR spectra confirm thepresence of the high-spin Fe(III)-containing anion and show a progressive localization in the organic sublatticealong with an antiferromagnetic coupling below ca. 120 K that, in the metallic
![](/images/gifchars/beta2.gif)
phase, could be at the origin ofthe transition from the metallic to the activated conductivity regime. The correlation between crystal structure andconductivity behavior has been studied by means of tight-binding band structure calculations which provide arationalization of the charge distribution and conductivity results.