Trinuclear copper(II) complexes with bridging (N–N) diazine ligands: structural and magnetic studies

The polytopic ligands 2poap and po2p have a linear disposition of coordination pockets suitably disposed to bind metal ions in close proximity and produce linear trinuclear copper(II) complexes. The complexes [Cu₃(2poap − 2H)(CH₃CO₂)₄]·3H₂O (1), [Cu₃(2poap − 2H)(H₂O)(DMF )₃(CH₃OH)₂](BF₄)₄ (2), and [Cu₃(po2p − H)₂(H₂O)₂](ClO₄)₄·2H₂O (3) have a linear arrangement of Cu(II) centres linked by a trans arrangement of N–N single bonds. Each metal is assigned a d_{x² − y²} magnetic ground state, and the trans diazine bridging arrangement leads to strong antiferromagnetic coupling in complete agreement with previous magnetostructural correlations relating the twist of the copper magnetic planes around the N–N bond to the exchange integral.