Gradual Two-step Spin Crossover Behavior of Binuclear Iron(III) Complex Bridged by trans-1,2-Bis(4-pyridyl)ethylene

Abstract

A binuclear iron(III) complex bridged by trans-1,2-bis(4-pyridyl)ethylene, [LFeIII(vibpy)FeIIIL](BPh4)2, showed a gradual two-step spin crossover behavior, where H2L is bis(3-methoxysalicylideneaminopropyl)methylamine and BPh4− is tetraphenylborate. The single-crystal X-ray analysis at the intermediate state revealed that one of the two FeIII ions of the binuclear complex is in the high-spin (HS) state and the other is in the low-spin (LS) state. The HS and LS sites independently form layers and these HS and LS layers alternately stack.

A rare octacoordinated mononuclear iron(III) spin-crossover compound: synthesis, crystal structure and magnetic properties

“…With decreasing temperature from 300 K, the m T value remained constant until the sample was cooled to about 150 K. After that, m T began to decrease at a comparatively fast rate to about 2.78 cm 3 K mol À1 at a temperature of 80 K, demonstrating the occurrence of a gradually incomplete SCO between the HS state and the LS state. On further lowering the temperature, the m T value decreased smoothly and reached its lowest value of 1.1 cm 3 K mol À1 at 2 K. A similar incomplete SCO behaviour was found in previously reported discrete hexacoordinated Fe III complexes based on pentadentate Schiff bases and bidentate pyridyl ligands (Fujinami et al, 2011;Kitashima et al, 2005;Boča et al, 2000).…”

Spin crossover iron(III) complexes

“…Gradual two step SCO was, on the other hand, observed in a binuclear complex of [(3-OMe-salten)Fe(vibpy)Fe(3-OMe-salten)](BPh 4 ) 2 (vibpy = 1,2-bis(4-pyridyl)ethylene)) ( Fig. 6a) [51]. The χ m T -T plot for the dinuclear complex showed a stepped curve with plateaus at 350 K (7.70 emu mol −1 K) and 140 K (4.75 emu mol −1 K), suggesting SCO from HS-HS to HS-LS states on two iron(III) sites.…”

“…Structures of (a) the cations in [(3-OMe-salten)Fe(vibpy)Fe(3-OMe-salten)](BPh 4 ) 2 , and (b) [{Fe(salten)} 3 Cr(CN) 6 ][51,52].…”

Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

“…Octahedral metal complexes with pentadentate ligand are of interest since their ligand field strength can be systematically controlled by modifying the additional monodentate ligand in line with the spectrochemical series [30][31][32], and such a characteristic is useful not only for exhibiting SCO but also for the possible tuning of T 1/2 . These complexes are also beneficial for the construction of polynuclear materials such as di [33][34][35][36][37][38][39][40][41][42], tri [43], tetra [44], penta [45], hepta [46][47][48], nona [48] and dodecanuclear [49] complexes by using bridging ligands instead of monodentate ligands for exhibiting multi-step spin transition. In the pentadentate ligand system, although iron(III) SCO compounds are well known [50][51][52][53][54][55][56][57], iron(II) spin transition systems are quite rare [58,59].…”