Single‐Ion Magnet Investigation of ABAB‐Type Tetrachloro‐ and Tetraalkoxy‐Substituted Bis(phthalocyaninato) Terbium Double‐Decker with D2 Symmetrical Ligand Field

Abstract

A D2h symmetrical ABAB‐phthalocyanine, 1,4,15,18‐tetrapentyloxy‐9,10,23,24‐tetrachlorophthalocyanine (TPTCPc), has been employed in the construction of sandwich‐type bis(phthalocyaninato) terbium double‐decker, resulting in the isolation and identification of a reduced form TbH(TPTCPc)2 (1). Single crystal structure analysis of 1 demonstrates the approximate square‐antiprismatic (SAP) coordination geometry around the TbIII ion along with a twist angle of 42.19°. However, the introduction of strong electron‐withdrawing chloride groups and electron‐donating pentyloxy groups on the peripheral and non‐peripheral positions, respectively, of ABAB‐phthalocyanine significantly perturbs the crystal field D4d symmetry of sandwich‐type bis(phthalcyaninato) lanthanide compound and affords a new crystal field with approximate D2 symmetry. Such perturbation has been clearly evidenced by theoretical calculations, which, instead of the protonation nature, exerts a negative effect in single‐molecule magnet (SMM) performance, further supporting the predominant advantage of crystal field D4d symmetry in SMM behaviors of sandwich‐type lanthanide compounds.