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Effect of Metal Dilution on the Thermal Spin Transition of [Fe x Zn 1– x (bapbpy)(NCS) 2 ]
Author(s) -
Zheng Sipeng,
Siegler Maxime A.,
Sánchez Costa José,
Fu WenTian,
Bonnet Sylvestre
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201201183
Subject(s) - chemistry , zinc , powder diffraction , crystallography , spin crossover , hexacoordinate , infrared spectroscopy , x ray crystallography , analytical chemistry (journal) , inorganic chemistry , diffraction , organic chemistry , physics , optics , silicon
This study reports on the effects of zinc dilution on the structure and magnetic properties of the mononuclear two‐step spin‐crossover compound [Fe(bapbpy)(NCS) 2 ] ( 1 ; bapbpy = N 6, N 6′‐di(pyridin‐2‐yl)‐2,2′‐bipyridine‐6,6′‐diamine). The zinc analogue of 1 , [Zn(bapbpy)(NCS) 2 ] ( 3 ), was synthesized and characterized by X‐ray powder diffraction, which suggests different structural features from 1 . The crystal structure of the related compound [Fe(bapbpy)(NCS)] 2 [Zn(NCS) 4 ] · 3DMF ( 4 ) was determined by single‐crystal X‐ray diffraction. Unlike the hexacoordinate Fe II in 1 , the Zn II ions in 4 are pentacoordinate. Nine diluted powder samples [Fe x Zn 1– x (bapbpy)(NCS) 2 ] were prepared with iron fractions of x = 0.89, 0.81, 0.76, 0.65, 0.60, 0.53, 0.44, 0.38, and 0.24. According to powder X‐ray diffraction and infrared spectroscopy, the phase of compound 1 is retained in the zinc‐diluted samples when x > 0.53. At higher dilutions (i.e., when x < 0.53), the phase of compound 3 gradually takes over, but the SCO of the iron complexes in the zinc phase remains observable at an iron fraction as low as x = 0.24. Powder X‐ray diffraction and infrared spectroscopy data indicate the presence of the zinc phase only (i.e., compound 3 ) when x ≤ 0.24. Magnetic susceptibility measurements on the diluted samples show that upon decreasing the iron fraction x , both hysteresis cycles become initially narrower, and then vanish to lead to a single‐step SCO material at x = 0.76. Upon additional increase of the zinc contents, the cooperativity of the SCO gradually vanishes to lead to a noncooperative SCO material at the lowest iron fraction studied ( x = 0.24). Despite the different coordination properties of the bapbpy ligand towards Fe II and Zn II , the spin crossover of the hexacoordinate Fe II complex is robust enough to withstand dilution into a magnetically silent Zn II phase that is structurally different from that of the iron compound.