Stereochemistry for engineering spin crossover: structures and magnetic properties of a homochiral vs. racemic [Fe(N3O2)(CN)2] complex

Abstract

The Schiff-base condensation of the R,R-(+)-diamine (2a) with 2,6-diacetyl pyridine in the presence of Fe^II affords the macrocyclic complex [Fe(dpN₃O₂)(CN)₂] (3a) (dp = diphenyl) with ligand centred chirality comprising of a 1 : 1 mixture of LS 6- and HS 7-coordinate Fe^II centres. Variable temperature magnetic susceptibility and Mössbauer studies reveal that (3a) undergoes an incomplete thermal SCO transition with a T_1/2 = 250 K as well as a LIESST effect. In contrast its racemic counterpart (3c) comprises of mostly LS Fe^II and exhibits no LIESST properties.