Charge transfer salts containing a paramagnetic cyano-complex and iodine substituted organic donor involving -: I(donor) •••N(anion)-interactions

The preparation, crystal structures, EHT band calculation and optical properties of two new charge transfer salts, namely (DIET)(2)[Fe(bpca)(CN)(3)] (1) and (DIEDO)(2)[Fe(bpca)(CN)(3)] (2), where bpca = bis(2-pyridylcarbonyl)amide anion, DIET = diiodoethylenedithotetrathiavalene and DIEDO = diiodoethylenedioxotetrathiavalene are reported. The magnetic properties of 2 and those of the low-spin iron(III) precursor of formula (PPh4)[Fe(bpca)(CN)(3)]center dot H2O (3) were also investigated in the temperature range 1.9-205 K. Crystal data; (1): monoclinic P2(1), a = 8.8238(2) angstrom, b = 13.2891(3) angstrom, c = 18.5042(5) angstrom, beta = 91.115(1)degrees, Z = 2, R = 0.0710 for 7021 independent reflections with I > 2 sigma(I) and (2): Monoclinic P2(1)/c, a = 8.6870(1) angstrom, b = 12.6122(2) beta, c = 36.0277(11) angstrom, beta = 90.380(5)degrees, Z = 4, R = 0.0602 for 4633 independent reflections with I > 2 sigma(I). The crystal structures for both compounds consist of alternating organic and inorganic layers. Compounds 1 and 2 exhibit semiconductive behavior. Simple tight-binding band calculations indicate quasi one- (1) and two-dimensional (2) electronic band structures. The magnetic properties of 2 compared to that of the low-spin iron(III) precursor 3 (which was used as a blank) reveal the occurrence of a relative large antiferromagnetic interaction between the DIEDO radical units, however, below 30 K, the magnetic behavior of 2 is indistinguishable from 3. (c) 2005 Academie des sciences. Published by Elsevier SAS. All rights reserved.