Dinuclear Complexes with a Triple N1, N2‐Triazole Bridge That Exhibit Partial Spin Crossover and Weak Antiferromagnetic Interactions. Issue 5 (26th November 2012)

• Record Type: Journal Article
• Authors: Roubeau, Olivier; Gamez, Patrick; Teat, Simon J.
• Other Names: Murray Keith S. sponsoringEditor.; Oshio Hiroki sponsoringEditor.; Real Jose Antonio sponsoringEditor.
• Is Part Of: European journal of inorganic chemistry. Issue 5/6(2013)
• Page Start: 934
• Page End: 942
• Publication Date: 2012-11-26
• Subjects: Triazole -- Coordination compounds -- Iron -- Spin crossover -- Magnetic properties; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201201126
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: The reaction of 4‐phenylimino‐1, 2, 4‐triazole (1 ) with Fe II, Co II, Ni II and Cu II thiocyanate produces a series of analogous dinuclear compounds of formula [M2 (1 )5 (NCS)4 ] (2 –5 ) as demonstrated by single‐crystal X‐ray diffraction studies of the Fe II (2 ) and Co II (3 ) analogues. The magnetic properties of [Fe2 (1 )5 (NCS)4 ]· x MeOH ( x = 3.5–5) reveal a partial and gradual spin crossover (SCO) centred at T SCO = 115 K. This is confirmed by its crystal structure solved at 100, 150 and 250 K, which exhibits a gradual decrease of the Fe–N bond lengths with temperature. However, the bulk hydrated form of2 that is generated upon exposure to air of crystals is a high‐spin compound that exhibits weak antiferromagnetic interaction. The exchange coupling among the Fe II S = 2 ions within the dinuclear neutral complex was evaluated as J / k B = –1.33(3) K by using the Heisenberg Hamiltonian H = –2 JS 1 · S 2 . Similarly, the magnetic properties of the Ni II (4 ) and Cu II (5 ) analogues are dominated by moderate and weak antiferromagnetic interactions evaluated as J / k B = –13.9(3) and –0.30(5) K, respectively. The presence of strong spin–orbit coupling of the individual Co II ions impeded the evaluation of the likely antiferromagnetic interaction that leads to a singlet ground state in3 . The reported structures of2 and3 are new additions to a very scarce family of dinuclear complexes bearing a unique triple N 1, N 2‐triazole bridge. Owing to its relevance in the peculiar properties of 1D triazole‐based SCO materials, which are widely studied for their various potential applications, a structural analysis of this triple N 1, N 2‐triazole bridge in reported structures of Fe II and Co II trinuclear and 1D compounds is provided. Abstract : Two new structurally characterized coordination compounds with a sole triple N 1, N 2‐1, 2, 4‐triazole bridge are reported with 4‐phenylimino‐1, 2, 4‐triazole as ligand. The structural parameters of this unique coordination link are reviewed and analyzed. The Fe II analogue exhibits gradual incomplete spin crossover centred at 115 K.