ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The title compound 1, {[Fe(H2pztc)(H2O)2] · 2 H2O}∞, has been prepared from pyrazinetetracarboxylic acid (H4pztc) and Fe(II) salt in H2O. It crystallizes in the monoclinic space group P21/a with cell parameters a = 13.56(1) Å, b = 7.17(1) Å, c = 6.48(1) Å, β = 101.0(2)°, V = 618.4 Å3. The molecules form infinite parallel chains with bis(bidentate) coordination (through N and O) of the bridging pyrazine ligands. Two trans-COOH groups of the ligand remain uncoordinated, and two trans-H2O ligands complete a pseudo-octahedral Fe(II) coordination which is distorted by the steric effect of the free COOH groups. The parallel polynuclear chains are linked through an extended network of H-bonds involving the COO functions of the bridging ligand and the coordinated and lattice H2O molecules. Mössbauer and magnetic-susceptibility data suggest normal paramagnetic behaviour of high-spin Fe2+. An observed drop below 15 K in effective magnetic moment for 1 was attributed to temperature-dependent population changes of the levels of the ground state 5Γ, and not to antiferromagnetic coupling (J 〈 1 cm-1). This result establishes that the obvious potential magnetic exchange pathway through the pyrazine bridges is inefficient, and this may be attributed, in part, to the high planarity of Fe(H2pztc) moieties.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19860690507
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