title: Tuning the spin-transition properties of pyrene-decorated 2,6-bispyrazolylpyridine based Fe(II) complexes.
abstract: Two 2,6-bispyrazolylpyridine ligands (bpp) were functionalized with pyrene moieties through linkers of different lengths. In the ligand 2,6-di(1H-pyrazol-1-yl)-4-(pyren-1-yl)pyridine (L1) the pyrene group is directly connected to the bpp moiety via a C-C single bond, while in the ligand 4-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)benzyl-4-(pyren-1-yl)butanoate (L2) it is separated by a benzyl ester group involving a flexible butanoic chain. Subsequent complexation of Fe(II) salts revealed dramatic the influence of the nature of the pyrene substitution on the spin-transition behaviour of the resulting complexes. Thus, compound [Fe(L1)(2)](ClO(4))(2) (1) is blocked in its high spin state due to constraints caused by a strong intermolecular π-π stacking in its structure. On the other hand, the flexible chain of ligand L2 in compounds [Fe(L2)(2)](ClO(4))(2) (2) and [Fe(L2)(2)](BF(4))(2)·CH(3)CN·H(2)O (3) prevents structural constraints allowing for reversible spin transitions. Temperature-dependent studies of the photophysical properties of compound 3 do not reveal any obvious correlation between the fluorescence of the pyrene group and the spin state of the spin transition core.
authors.affiliation: Karlsruhe Institute of Technology, Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: González-Prieto
authors.forename: Benoit
authors.initials: B
authors.lastname: Fleury
authors.forename: Frank
authors.initials: F
authors.lastname: Schramm
authors.forename: Giorgio
authors.initials: G
authors.lastname: Zoppellaro
authors.forename: Rajadurai
authors.initials: R
authors.lastname: Chandrasekar
authors.forename: Olaf
authors.initials: O
authors.lastname: Fuhr
authors.forename: Sergei
authors.initials: S
authors.lastname: Lebedkin
authors.forename: Manfred
authors.initials: M
authors.lastname: Kappes
authors.forename: Mario
authors.initials: M
authors.lastname: Ruben
mesh_terms: D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D008163:Luminescent Measurements; D008280:Magnetics; D008958:Models, Molecular; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*; D011721:Pyrenes / Q000138:chemical synthesis / Q000737:chemistry*; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature
chemical_list: D005296:Ferrous Compounds; D008024:Ligands; D011720:Pyrazoles; D011721:Pyrenes; D011725:Pyridines; C030984:pyrene