Spin crossover iron phenanthroline complexes

The ligand field strength approaches the spin crossover point in the iron(II) complexes of l,10-phenanthroline-2-carbaldehyde hydrazones, (phen-2-CH=N-NR1R2) (V)123). 

Similar effects of intra-ligand substitution on the ligand field strength have been observed on iron (II) complexes with l,10-phenanthroline-2-carbaldehyde imines (phen-2-CH=NR) (VI)12S). The only complex which has been found to exhibit spin crossover (gradual in this case) is the tetrafluoroborate with R = tertiary butyl (Bul)... 

Iron(ii) complexes of 2-methyl-l,10-phenanthroline (L) have been prepared. FeL2X2 (X = Cl, Br, NCS, N3, or malonate) are all high-spin, the CNS complex containing N-bonded anions in a cis arrangement. FeL2(CN)2 is low-spin, and it is concluded that the crossover point for FeL2X2 is exactly at the position of L in the spectrochemical series, in contrast to the analogous... 

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... 

A spin-crossover study on one of the most studied iron(II) complexes, the [Fe(phen)2(NCS)2] (phen = 1,10-phenanthroline) was recently published... 

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