Iron complexes spin crossover

Keywords Iron(II) spin crossover complexes Multidentate ligands Ligand design Synthesis Magnetic properties... 

It is expected that ligands providing a weaker ligand field than tpa will be obtained if one or more of the 2-pyridylmethyl arms are replaced by 2-pyr-idylethyl arms. However, the first ligand of such a series of expanded tripo-dal ligands (7) still forms an iron(II) spin crossover system. However, if more than one of the chelate rings are six-membered, only high-spin complexes are formed [14]. 

Figure 17-E-3 Schematic representation of the potential wells for the LS ( A,) and the HS (ST2) states of an iron(II) spin crossover complex. The nuclear coordinate is the bond length. Thermal spin crossover is observed when AEHL — kT.

Bipyrimidine-Bridged Iron(II) Spin-Crossover Complexes... 

The initial reports of synthetic iron(II) spin crossover involved [Fe(diimine)2(NCS)2] complexes where the diimine was either 1,10-phenanthroline or 2,2 -bipyridine. The spin crossover situation persists in such complexes for a wide range of diimine species and for certain unidentate pyridine derivatives/ bridging diimine systems and bis(unidentate) systems. In addition, mixed aromatic-aliphatic N4 quadridentate donors have been incorporated into this general class. The anionic groups can be varied and spin crossover is also observed in [Fe(diimine)2X2] systems when X =NCSe, [NCBH3] TCNQ [N(CN)2] and 2X =[WS4f... 

Figure 1 The electronic structure of iron(II) spin-crossover complexes. The mechanisms of LIESST, reverse-LIESST, and NIESST are indicated by curly arrows.

Figure 5 hl on a log scale plotted against 1/r for a series of iron(II) spin-crossover and low-spin complexes diluted in inert host lattices [Zn Fe(ptz)6](BF4)2 ( ), [Mn Fe(pic)3]Cl2EtOH ( ) from laser pulse excitation, (V) [Fe(pic)3]Cl2EtOH from Mossbauer lineshape analysis, [Zn Fe(mepy)3tren](PF6)2 ( ), [Zn Fe(bpy)3tren](PF6)2 (A), [Mn Fe(bpy)3tren](PF6)2 ( ) from laser pulse excitation, (o) from... 

Naik AD, Tinant B, Muffler K, Ja W, Sehtinemann V, Garcia Y (2009) Relevance of supramolecular interactions, texture and lattiee occupancy in the designer iron(II) spin crossover complexes. J Solid State Chem 182 1365-1376... 

There will exist an equilibrium between the two states. If the ener between the two states, E, is of the order of kT, then the relative populations of the two states will vary with the temperature of the sample. In the Fe(III) dithiocarbamate series of complexes, [FeCRiRgdtcla], AE can be varied by suitable choice of substituents Ri and Rj. Although these are well removed from the FeSg molecular core, they can appreciably affect the electronic parameters of the central iron atom and of the surrounding crystal field of the sulfur atom by way of the conjugated system of the ligand (237). The results of the spin crossover are reflected in magnetic susceptibility data. 

Giitlich and Hauser (1989) Thermal and light-induced spin crossover in iron(II) complexes—new perspectives in optical storage [227]. 

Giitlich (1997) Spin crossover, LIESST and NIESST—fascinating electronic games in iron complexes [239]. 

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