Inducing Spin Crossover in Amphiphilic Iron(III) Complexes

Abstract

Thermal spin crossover (SCO) was induced in a high-spin Fe III complex by alkylation of the polyamino ligand backbone. The SCO profile was responsive to chain length with partial crossover observed with C 6 alkylation and full transi-

Organization of spin- and redox-labile metal centers into Langmuir and Langmuir–Blodgett films

“…Multilayer fabrication was limited to a maximum of four layers, as subsequent layer deposition occurred only partially (transfer ratio ~ 0.7) and, most significantly, these layers were released again upon immersion. Attempts to increase the number of layers by 10 changing the solid support from glass to silicon wafers or to gold showed no improvement. Modification of the surface pressure during film transfer from 4 to 8 mN/m enhanced the initial transfer ratio (0.97 for first emersion, 0.89 for second emersion), however, only oligolayers were obtained again.…”

“…Modification of the alkyl tail length (7a-d) or the number of alkyl chains (7e-g) had virtually no impact on the low-energy absorption wave-length in the visible region (λ max ), attributed to a ligand-to-metal charge transfer. This band is expected to 10 be highly sensitive to modifications in the ligand donor properties and to changes in the ligand coordination geometry. Spectroelectrochemical measurements using an optically transparent thin layer electrode (OTTLE) cell 21 allowed the electrochemically generated iron(II) complexes to be 15 characterized in situ.…”

“…9c This position hence offers a suitable anchor for covalently installing entities for supramolecular engineering 45 without affecting the bonding situation around the metal center. Similar to amine functionalization, 10 aryl substitution addresses two mutually cis-oriented donor sites of the sal 2 (trien) ligand. Introduction of lipophilic substituents therefore provides a methodology for evoking amphiphilic 50 behavior of the molecule, especially when bound to a M III metal center that induces an ionic coordination environment.…”

“…However, models based on crystal structure analyses suggest a surface area of the polar iron sal 2 (trien) unit of ca. 65 Å 2 , 9 thus requiring three alkyl chains of 20 Å 2 each for reaching similar projection 10 planes of the polar and apolar fragments. 24 Possibly, back folding 25 of the alkyl chains in the complexes 7c and 7d may occur, thus accounting for the observed surface per molecule (~ 4 × 20 Å 2 ) and providing an explanation for the similar surface area of the dialkylated complexes with the 15 tetralkylated (and presumably not back folding) species 7e-g.…”

Synthesis and characterisation of Fe(III) and Co(III) complexes of thiazole-containing thiosemicarbazone ligands

“…Thiosemicarbazone-based ligands are ideal for such a purpose as they are readily and reliably constructed from simple precursors allowing introduction of a large range of substituents. [23][24][25][26][27][28][29][30][31][32] Here we report the synthesis and characterization of three thiazole containing thiosemicarbazone ligands (L1-L3, Fig. 1) and their complexation with Fe(III) and Co(III).…”