Iron(ii) spin crossover complexes with diaminonaphthalene-based Schiff base-like ligands: mononuclear complexes

Abstract

The synthesis of new Schiff base-like ligands with extended π-system and their iron complexes is described. Some of the iron(ii) complexes with N-heterocycles as axial ligands show spin crossover behaviour. The influence of the extended aromatic system on cooperative interactions is investigated by single crystal X-ray structure analysis, X-ray powder diffraction, and magnetic measurements. A combination of C-Hπ and C-HO interactions is made responsible for up to 10 K wide thermal hysteresis loops.

Influence of CF3 Substituents on the Spin Crossover Behavior of Iron(II) Coordination Polymers with Schiff Base‐like Ligands

“…Another approach to receive cooperativity is the introduction of long‐range interactions through 1D coordination polymers . In recent years the well‐known Jäger Schiff base‐like system, was studied extensively, as the iron(II) complexes often showed SCO behavior both, as mononuclear and dinuclear complexes, and as 1D coordination polymers, and ladder‐type polymers . Processing of these polymers is often hampered by their low solubility due to strong intermolecular interactions.…”

Synthesis and Optical Properties of Phenanthroline‐Derived Schiff Base‐Like Dinuclear RuII–NiII Complexes

“…Ligand 1 was obtained from a condensation reaction between the 5,6‐diamino‐1,10‐phenanthroline and a keto enol ether by using a method already developed for similar Schiff base‐like ligands . The purity of 1 was confirmed with 1 H and 13 C NMR spectroscopic, mass‐spectrometric, IR spectroscopic and elemental analysis.…”

“…Analysis of the C−C bond lengths given in Table clearly shows that the ligand crystallises as keto‐enamine tautomer, in good agreement with the NMR spectroscopic analysis. This result is in line with already reported Schiff base‐like ligands of this general type . The chelate cycles of the molecule are twisted in opposite directions out of the phenanthroline plane.…”

“…Please note that the amount of carbon present, as determined by elemental analysis, is too low due to incomplete combustion for all samples. The same difficulties were encountered for similar complexes of this ligand type with extended aromatic units . In addition, SEM images were recorded to analyse the homogeneity of the samples and showed that the samples were homogeneously amorphous (see Figure S1 in the Supporting Information).…”

Bifunctional Fe(ii) spin crossover-complexes based on ω-(1H-tetrazol-1-yl) carboxylic acids

“…27 Therefore, in this work, a carboxylic acid moiety has been introduced to the ligand system, allowing for the investigation of the SCO in [Fe(ω-(1Htetrazol-1-yl) carboxylic acid)6] 2+ -cations. Alkylcarboxylic acid substituted tetrazoles provide three useful features: On a molecular level the COOH-group should establish a network of hydrogen bonds, increasing cooperativity and governing the abruptness of the spin state transition, [28][29][30] the COOH-group may act as an additional ligand allowing for the formation of multi-metallic networks with a second transition metal, or rareearth element and, finally, the COOH termination of the ligand may allow for deposition on oxide surfaces. In this contribution, we report the ω-(1H-tetrazol-1-yl) carboxylic acids with C2-C4 alkyl chains and the magnetic, structural and spectroscopic characterization of their Fe(II)-SCO…”