Details

Autor(en) / Beteiligte

• Adams, Christopher J
• Muñoz, M. Carmen
• Waddington, Rachel E
• Real, José Antonio

Titel

Cooperative Spin Transition in the Two-Dimensional Coordination Polymer [Fe(4,4′-bipyridine)2(NCX)2]·4CHCl3 (X = S, Se)

Ist Teil von

• Inorganic chemistry, 2011-11, Vol.50 (21), p.10633-10642

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2011

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Two new isostructural two-dimensional (2D) coordination polymers exhibiting spin crossover (SCO) behavior of formulation [Fe(4,4′-bipy)2(NCX)2]·4CHCl3 (4,4′-bipy = 4,4′-bipyridine; X = S [1·4CHCl 3 ], Se [2·4CHCl 3 ]) have been synthesized and characterized, and both undergo cooperative spin transitions (ST). For 1·4CHCl 3 the ST takes place in two steps with critical temperatures of T c1 down = 143.1 K, T c2 down = 91.2 K, T c1 up = 150.7 K, and T c2 up = 112.2 K. 2·4CHCl 3 displays half ST characterized by T c down = 161.7 K and T c up = 168.3 K. The average enthalpy and entropy variations and cooperativity parameters associated with the ST have been estimated to be ΔH 1 av = 5.18 kJ mol–1, ΔS 1 av = 35 J K–1 mol–1, and Γ1 = 2.8 kJ mol–1 and ΔH 2 av = 3.55 kJ mol–1, ΔS 2 av = 35 J K–1 mol–1, and Γ2 = 2.6 kJ mol–1 for 1·4CHCl 3 , and ΔH av = 6.25 kJ mol–1, ΔS av = 38.1 J K–1 mol–1, and Γ = 3.2 kJ mol–1 for 2·4CHCl 3 . At T > [T c1 (1·4CHCl 3 ); T c (2·4CHCl 3 )], both compounds are in the space group P2/c while at T < [T c1 (1·4CHCl 3 ); T c (2·4CHCl 3 )] they change to the C2/c space group and display an ordered checkerboard-like arrangement of iron(II) sites where the high- and low-spin states coexist at 50%.