STRUCTURES AND MAGNETIC-PROPERTIES OF SOME FE(III) COMPLEXES WITH HEXADENTATE LIGANDS - IN CONNECTION WITH SPIN-CROSSOVER BEHAVIOR

Several iron(III) complexes with the different hexadentate Schiff-base ligands of N4O2 donor sets were synthesized; these are 1 : 2 condensa tion products of linear tetramines (3,3,3-, 3,2,3-, 2,3,2- or 2,2,2-te tramine) and salicylaldehyde, acetophenone or benzophenone derivatives . Their crystal structures, Mossbauer spectra, magnetic susceptibiliti es, electronic spectra and cyclic voltammetry of the complexes were ex amined. The X-ray structures of the single crystals of [Fe(3,2, 3-sal( 2)tet)]NO3 (1), [Fe(3,2,3-sal(2)tet)]BPh4 (2), [Fe(3,2,3-mpk(2)tet)]PF 6 (3), [Fe(2,3,2-sal(2)tet)]ClO4 (4), [Fe(2,3,2-3MeO-sal(2)tet)]ClO4 ( 5), [Fe(2,3,2-mpk(2)tet)]ClO4 (6), [Fe(2,3,2-bpk(2)tet)]CLO4 (7), and [Fe(2,2,2-bpk(2)tet)]ClO4 . EtOH (8) were determined. Crystal data for (1): C22H28N5O5Fe, space group P2(1)/c, Z = 4, a = 7.607(1), b = 16.0 63(1), c = 19.063(1) Angstrom, beta = 91.00(2)degrees, V = 2329(3) Ang strom(3), R = 5.8%, R-w = 4.2%, 4605 reflections. Crystal data for (2) : C46H48N4O2BFe, space group P2(1)/n, Z = 4, a = 14.390(6), b = 20.617 (8), c = 14.754(5) Angstrom, beta = 115.85(2)degrees, V = 3939(2) Angs trom(3), R = 6.3%, R-w = 6.7%, 7458 reflections. Crystal data for (3): C24H32N4O2PF6Fe, space group P2(1)/c, Z = 4, a = 9.37(6), b = 24.15(7 ), c = 12.85(3) Angstrom, beta = 97.7(3)degrees, V = 2880(17) Angstrom (3), R = 10.9%, R-w = 13.6%, 5569 reflections. Crystal data for (4): C 21H26N4O6ClFe, space group Pbcn, Z = 4, a = 11.041(2), b = 17.251(2), c = 11.722(2) Angstrom, V = 2232(1) Angstrom(3), R = 3.9%, R-w = 2.8%, 2258 reflections. Crystal data for (5): C23H30N4O8ClFe, space group P een, Z = 8, a = 14.567(1), b = 22.288(1), c = 15.477(1) Angstrom, V = 5025(4) Angstrom(3), R = 6.2%, R-w = 6.2%, 4956 reflections. Crystal d ata for (6): C23H30N4O6ClFe, space group Pbca, Z = 8, a = 28.249(4), b = 13.989(4), c = 13.174(4) Angstrom, V = 5205(1) Angstrom(3), R = 8.2 %, R-w = 8.4%, 5148 reflections. Crystal data for (7): C33H34N4O6ClFe, space group <P(1)over bar>, Z = 2, a = 10.241(3), b = 17.373(1), c = 9.692(7) Angstrom, alpha = 105.95(6)degrees beta = 91.61(4)degrees, ga mma = 93.83(4)degrees, V = 1652(1) Angstrom(3), R = 7.1%, R-w = 7.6%, 6179 reflections. Crystal data for (8): C34H38N4O7ClFe, space roup P2( 1)/c, Z = 4, a = 14.553(4), b = 14.079(4), c = 16.959(6) Angstrom, bet a = 94.92(3)degrees, V = 3461(1) Angstrom(3), R = 8.4%, R-w = 7.7%, 66 51 reflections: The moieties of the iron atoms of (1), (2), and (3) wi th 3,2,3-tetramine, and (7) with 2,3,2-tetramine were pseudo octahedra l with trans-FeN4O2 geometry. Those of (4), (5), and (6) with 2,3,2-te tramine, and (8) with 2,2, 2-tetramine were cis-FeN4O2 geometry. The i ron(III) complexes (1), (2), (3), and (7) were in the low-spin state, and the iron(III) complexes (4), (5), (6), and (8) were in the high-sp in state. In the electronic spectra, the wave lengths of the LMCT band s for the low spin complexes were longer than those for the high-spin complexes. The values of redox potentials for the low-spin states were suggested to be 0.12 V more negative than those for the high-spin sta tes.