Structural transformation from a coplanar layer to a linear chain by switchable coordination of exocyclic amino group

Two new magnetic entities, [Cu(atr)(μ-OH)(NO3)]n (1) and {[Cu(atr)2(NO3)]·NO3}n (2) (atr = 4-amino-1,2,4-triazole), were respectively obtained by tuning the molar ratio of initial reactants and structure-directing agent. Complex 1 exhibits a grid-like coplanar layer with hydroxyl group bridged linear ―CuOCu― chains interlinked by pairs of exotridentate μ3-atr ligands. Instead, 2 displays a linear chain periodically extended by two μ-atr and one nitrate connectors. The structural transformation is significantly governed by the switchable coordination of exocyclic amino group of atr ligand. Antiferromagnetic interactions with variable strength between the nearest intra-chain spin carriers lead to overall S = 0 spin ground states of the two complexes.