A cyanide-bridged FeII/FeIII mixed-valence chain exhibiting spin transition in the Fe(II) sites.

An isolated cyanide-bridged {FeIII 2 FeII} n one-dimensional double-zigzag chain {[Fe(Tp)(CN) 3 ] 2 Fe(btb)} n (Tp = hydrotris(pyrazolyl)borate, btb = 1,4-(1H-1,2,4-triazole)butane) has been synthesized via hydrothermal reaction. Single-crystal X-ray data, magnetic measurement, and infrared (IR) absorption spectra indicate that this complex exhibits thermal and light induced spin transition behavior in the Fe(II) sites. [Display omitted] • A cyanide-bridged {FeIII 2 FeII} n 1D double-zigzag chain has been synthesised. • This complex exhibits thermal induced spin transition in the Fe(II) sites. • Light-induced excited spin-state trapping of this complex was also observed at low temperature. A cyanide-bridged {FeIII 2 FeII} n one-dimensional chain {[Fe(Tp)(CN) 3 ] 2 Fe(btb)} n (1) (Tp = hydrotris(pyrazolyl)borate, btb = 1,4-(1H-1,2,4-triazole)butane) has been synthesized via the hydrothermal reaction of Li[Fe(Tp)(CN) 3 ], btb, and FeII(ClO 4) 2 ·6H 2 O at 120 °C. Single-crystal X-ray analysis reveals that compound 1 is an isolated neutral mixed-valence {FeIII 2 FeII} n double-zigzag chain with each [FeIII(Tp)(CN) 3 ]− unit connecting with two Fe(II) centres via two of its three CN− groups in the cis -positions, and two triazole groups from btb coordinated with Fe(II) ion in its axial positions. Single-crystal data obtained at different temperature together with magnetic data indicate that complex 1 exhibits thermal induced spin transition in the Fe(II) sites with T 1/2 ≈ 165 K. Additionally, light-induced excited spin-state trapping (LIESST) of 1 was also observed at low temperature. [ABSTRACT FROM AUTHOR]