Full paper / Mémoire 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]·H2 O( 3) were also investigated in the temperature range 1.9–205 K. Crystal data; (1): monoclinic P21, a = 8.8238(2)A, b = 13.2891(3) A, c = 18.5042(5) A, b = 91.115(1)°, Z =2 ,R = 0.0710 for 7021 independent reflections with I >2 r(I) and (2): Monoclinic P21/c, a = 8.6870(1) A, b = 12.6122(2) A, c = 36.0277(11) A, b = 90.380(5)°, Z =4 ,R = 0.0602 for 4633 independent reflections with I >2 r(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 mag