23388-23-0Relevant academic research and scientific papers
Spin states in iron(III) phthalocyanines studied by M?ssbauer, magnetic susceptibility, and ESR measurements
Kennedy, Brendan J.,Murray, Keith S.,Zwack, Peter R.,Homborg, Heinrich,Kalz, Winfried
, p. 2539 - 2545 (2008/10/08)
Magnetic susceptibility, M?ssbauer, and ESR measurements, over a wide temperature range, have been used to determine the ground states and electronic structures of a range of iron(III) phthalocyanine complexes. Anionic six-coordinate species B+-[FeL2(Pc(2-))]- (B+ = bulky cation; L = OH-, OPh-, NCO-, NCS-, N3-, CN-) display low-spin d5 characteristics. Magnetic moments at 295 K are in the range 2.05-2.49 μB and show a Curie-Weiss dependence on temperature between 295 and 4.2 K. Well-resolved ESR spectra were obtained on neat powders of the dihydroxo, diphenoxo, and diazido derivatives. Analysis of the three g value line shapes in terms of a simple crystal field model yielded values of the tetragonal and rhombic splitting parameters that were similar in magnitude to those recently reported for anionic iron porphyrins of type [Fe(OR)2TPP]-. M?ssbauer parameters are in the ranges normally observed for low-spin FeIII-N4 macrocycles, viz. δ = 0.18-0.29 mm s-1 (relative to Fe) and ΔEQ = 2.22-2.65 mm s-1, except for L = CN- with δ = 0.11 mm s-1 and ΔEQ = 0.99 mm s-1 (at 4.2 K). The dicyano species generally displays differences in electronic detail from those of the other axially ligated derivatives. In the resonance Raman spectra the cyano, isocyanato, and isothiocyanato complexes display electronic Raman transitions at 525, 490, and 520 cm-1, respectively, arising from transitions within the spin-orbit split sublevels of the 2T2g (Oh) ground state. A wide range of five-coordinate complexes with halide and O-donor axial ligands have been studied of type FeX(Pc(2-)), where X = Cl, Br, I, RCO2, or RSO3. These compounds display intermediate-spin (S = 3/2) or spin-admixed (S = 3/2-S = 5/2) behavior as judged by magnetic moments (3.9-4.53 μB) and M?ssbauer parameters (δ ～ 0.28 mm s-1; ΔEQ = 2.94-3.23 mm s-1). Comparisons are made with related FeX(porph) complexes. In contrast to the many examples of high-spin, S = 5/2, iron(III) porphyrins, there are very few well-characterized high-spin phthalocyanine analogues. One such example is the binuclear μ-oxo complex [Fe(Pc(2-))]2O. Its electronic features are briefly described together with those for the sulfato complex [Fe(SO4)(Pc(2-))]-.
