Three copper(II) 4-amino-1,2,4-triazole complexes containing differently deprotonated forms of 1,3,5-benzenetricarboxylic acid: Synthesis, structures and magnetism

Three new CuII cluster-based magnetic complexes with the same components but different structures and magnetic behavior, [Cu4(atr)2(μ3-OH)2(btc)2]n (1), {[Cu3(atr)6(H2O)2(H2btc)2]·4H2btc·11H2O·DMF}n (2), and [Cu3(atr)6(Hbtc)2(H2btc)2]·2H2O (3) (atr = 4-amino-1,2,4-triazole and H3btc = 1,3,5-benzenetricarboxylic acid), were synthesized by varying the preparation methods and fully characterized. Significantly due to the deprotonation extent-dependent binding modes of the aromatic tricarboxylic acid coligand, the former two complexes exhibit polymeric structures with a butterfly-shaped CuII4 cluster-based rtl-type framework for 1 and a linear CuII3 subunit-derived coplanar layer for 2, and the last one is a discrete linear CuII3 entity blocked by the terminal tricarboxylate groups. The cooperative antiferromagnetic and ferromagnetic nearest-neighbor interactions mediated by the differently four-fold heterobridges in the local CuII4 cluster result in an S = 0 ground state of 1. Instead, the central CuII ion in the linear CuII3 subunit is antiferromagnetically coupled with its two external ones through triple μ-κ2N1:N2-atr homobridges to lead to an S = 1/2 ground state of 2 and 3.

Graphical abstractThree CuII cluster-based complexes with the same components but different structures and magnetic behavior, a butterfly-shaped CuII4 cluster-based rtl-type framework for 1 with an S = 0 spin ground state, a linear CuII3 subunit-derived coplanar layer and a discrete linear CuII3 system for 2 and 3 with an S = 1/2 spin ground state, were structurally and magnetically characterized.Figure optionsDownload full-size imageDownload as PowerPoint slide