Anion-dependent spin crossover and coordination assembly based on [Fe(tpa)]2+ [tpa = tris(2-pyridylmethyl)-amine] and [N(CN) 2]-: Square, zigzag, dimeric, and [4+1]-cocrystallized complexes

Rong Jia Wei, Jun Tao*, Rong Bin Huang, Lan Sun Zheng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

A series of FeII complexes based on [Fe(tpa)]2+ building units and [N(CN)2 ]- bridging ligands with different anions for charge balance has been prepared and characterized. They have a general formula [Fe(tpa){N(CN)2 }]x·Y·Z, where x = 4 (14+), Y = 4ClO4 -, and Z = 2H2O for 1·(ClO4) 4(H2O)2 ; x = n (2n+), Z = 0, and Y = nClO 4 -, nPF6 -, nAsF6 -, and nBPh4 - for 2·(ClO4)n, 2·(PF6) n, 2·(AsF6)n, and 2·(BPh 4)n, respectively; x = 2 (32+), Z = 0, and Y = 2BPh 4 - for 3·(BPh4)2 ; x = 4 (44+), Y = 3SbF6 - + [N(CN)2 ]-, and Z = [Fe(tpa){N(CN)2 }2] (5) + 4H2O for (4+5). Single-crystal X-ray diffraction studies reveal that these complexes show various structures that are affected by different counteranions, i.e., square 1·(ClO4) 4(H2O)2 , zigzag polymers [2·(ClO 4)n, 2·(PF6)n, 2·(AsF6)n, and 2·(BPh4) n], dimeric 3·(BPh4)2 , and [4+1]-cocrystallized (4+5). Magnetic studies show that the square complex 1·(ClO4)4(H2O)2 undergoes a two-step complete spin crossover, whereas the dimer 3·(BPh 4)2 is high-spin in the whole temperature range, and all zigzag polymer 2·anions show spin-crossover (SCO) behavior, the transition temperature (T1/2) of which increases with increasing anion size. Interestingly, complex (4+5) displays a gradual two-step spin crossover, which is different from that of 1·(ClO4)4(H 2O)2 and originates from the cocrystallized spin-crossover tetranuclear and monomeric species. Detailed studies on the crystal structures and magnetic properties have unveiled a remarkable anion-dependent formation of different structures and SCO behavior of these complexes.

Original languageEnglish
Pages (from-to)916-926
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Issue number5-6
DOIs
Publication statusPublished - Feb 2013
Externally publishedYes

Keywords

  • Anion dependence
  • Coordination assembly
  • Magnetic properties
  • Spin crossover
  • Structure elucidation

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