Periodicity in the properties of lanthanoids: Review of theory, systematics and the role of nephelauxetic effects

Abstract

Development in the phenomenon of tetrad or double-double effect in periodically in the properties of lanthanoids (Lns) and its recent quantum chemical enplanation have been reviewed.A  five-parameter semi-empirical equation based on interelectronic repulsion Racah parameters has also been used and discussed to calculate the extrastabiliztion' (Est) at specific fq configurations and the 'nephelauxetic ratio' (E3/E1) for Lns in different ligand environments. The possibility of dependence of 3Est, on ligand basicity has heen examined with prospects of developing a nephelauxetic series for Lns. The nomadic behaviour of Y(III) with respect to Ln(III)s has also been discussed.