Geometrical preferences of complexes of terpyridine N-oxide ligands: synthesis and crystal structures of nickel(II) with terpyridine 1,1′,1″-trioxide, terpyridine 1,1″-dioxide and terpyridine 1-oxide

[NiL2][ClO4]2 complexes (L = terpyridine 1,1′,1″-trioxide, terpyridine 1,1″-dioxide and terpyridine 1-oxide) have been prepared and crystallographically characterised; data shows a predictable variation in ligand conformation, such as facial or meridonal binding, which is in agreement with DFT calculations.