A combined theoretical and experimental approach to determine the right choice of co-ligand to impart spin crossover in Fe(II) complexes based on 1,3,4-oxadiazole ligands.

We present the synthesis of two new novel tetradentate ligands based on 1,3,4-oxadiazole, 2-(2-pyridyl)-5-[,-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole (LTetraPy-ODA) and 2-(2-phenyl)-5-[,-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole (LTetraPh-ODA). The ligands were used to prepare six mononuclear complexes [Fe(LTetraPy-ODA)(NCE)] (C1-C3) and [Fe(LTetraPh-ODA)(NCE)] (C4-C6) where E = S, Se or BH. In addition, the ligand LTetraPy-ODA was employed in the synthesis of a new di-nuclear complex [FeII2(LTetraPh)](ClO)·1 CHNO·1.

Synergetic spin singlet-quintet switching and luminescence in mononuclear Fe(II) 1,3,4-oxadiazole tetradentate chelates with NCBH co-ligand.

We report the multi-step synthesis of the tetradentate 2-(naphthalen-2-yl)-5-[,-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole ligand (LTetra-ODA) along with its corresponding [Fe(LTetra-ODA)(NCBH)]·1.5CHOH (C1) complex, which is the first mononuclear 1,3,4-oxadiazole based Fe(II) spin crossover (SCO) complex, and its zinc analogue [Zn(LTetra-ODA)(NCBH)]·0.5HO (C2).