5T2g-1A1g Spin crossover in tris[2-(2'-pyridyl)benzimidazole]iron(II) complexes

Solution-state spin-equilibrium properties of the tris[2-(2-pyridyl)imidazole]iron(II) and tris[2-(2-pyridyl)benzimidazole]iron(II) cations

“…Even though lattice solvation effects are not crucial for the solution-phase studies reported below, it is still interesting that our preparations yield solvates different from ethanol (2.62 µ at 293 K) differs from the CC14-H20 solvate we obtained by precipitation of the compound from CH2C12 with CC14 (2.23 µ at 298 K). Likewise, the monohydrate of [Fe((py)bimH)3](BPh4)2 that Sams et al 18 isolated by precipitation with NaBPh4 in 95% ethanol (4.9 µ at 300 K) differs from the trihydrate we obtained via precipitation of the same compound from methanol (5.1 µ at 298 K). Such differences appear commonplace for these complexes, regardless of the anion present.…”

“…Such studies are of fundamental importance in understanding intersystem crossing phenomena as they relate to photochemically induced excited states15 and for a general understanding of the role of spin-multiplicity changes on electron-transfer rates. 16 In this work we report the solution-state spin-equilibrium properties for the [Fe((py)imH)3]2+ and [Fe((py)bimH)3]2+ cations, both of which have been found to exhibit the phenomenon in solution contrary to earlier findings.17, 18 In addition, the neutral iron(III) complex of the 2-(2-pyridyl)imidazolate anion, Fe((py)im)3, has also been prepared by deprotonation of [Fe((py)imH)3]2+, via an Fe((py)imH)2Cl2 intermediate, and characterized as low spin in both the solution and solid states.…”

Tuning of the charge in octahedral ferric complexes based on pyridoxal-N-substituted thiosemicarbazone ligands

“…11 In general, Fe(III) spin crossover behaviour is related to many factors such as; counter anion, solvate molecules, intermolecular interactions or hydrogen bonding network, which mediate the intercentre communication in the solid. [14][15][16][17] Recent work carried out on ferrous complexes bearing imidazole-type ligand evidenced that the spin state of the metal center can also be tuned through the protonation state of the ligand, 18 as this may influence the ligand field strength about the metal ion. Considering these features, our report aims on varying the charge of the metal complex by essentially maintaining the same geometry around the central atom, and thereby, tuning the spin state of the metal ion.…”

Nonlinear optical frequency conversion in a resonator with random inhomogeneities

“…Sams and Tsin (1976) derived the parameter values BY = -152 cm-', A = -80 cm-' for Fe(PyN0)6(C104)2, and these values were used for the calculations reported here. The Fe2+ ground state is a doublet, derived from the trigonal 5E, orbital doublet, and it lies more than 100 cm-' below the first excited state.…”

“…The Mossbauer results indicated that under these conditions well resolved paramagnetic hyperfine structure should be observed at sufficiently low temperatures, even in the absence of an applied magnetic field. The ferrous ion sites in the rhombohedral (space group R3) compound Fe(PyN0)6(C104)2 (where PyNO = C5H5NO) are of similar symmetry to those in the carbonates referred to above (C3,), and the Fe2+ ground state is also expected to be an $ (Sams andTsin 1975a, b, 1976) indicate that this is the case, but even at very low temperatures well resolved paramagnetic hyperfine structure was not observed in the absence of an applied field. Application of small magnetic fields (-0.1 T ) , however, resulted in the appearance of resolved hyperfine structure.…”