Investigation of iron(III) ionic structural complexes for seebeck coefficient enhancement using variation of ligand lengths with extended Π-conjugated bipyridyl ligands

Abstract

Abstract Five new octahedral spin-crossover magnetic complexes with general formulae, [Fe(LCn)3](BF4)3, where L\u202f=\u202fligand, and n\u202f=\u202f8, 10, 12, 14, 16, were synthesized and characterized. The influence of different ligand lengths on the diffusion and Seebeck coefficient, and the effect of counterions were investigated. It was found that diffusion and Seebeck values were highly dependent on magnetic properties of the complexes and the agglomeration formed from the long ligand lengths. Hence, it was found that ionic complexes with higher percentage of low-spin have recorded the highest diffusion and Seebeck values due to the presence of N-donor ligand as an effective electron donor to the metal centre. Thus, it is easier to break the Coulombic interaction, consequently increase the ionic mobility in solution that accounted for the entropy formed. Therefore, these findings provide a systematic pathway in the designing and synthesising SCO complex to obtain optimum performance of thermo-electrochemical materials.