Chiral Crystal Structure of a P212121 Kryptoracemate Iron(II) Complex with an Unsymmetric Azine Ligand and the Observation of Chiral Single Crystal Circular Dichroism

A chiral complex, [Fe­(HL)2]­(PF6)2 (1), where HL denotes 2-pyridylmethylidenehydrazono-4-(2-methylimidazolyl)­methane, was prepared. X-ray structure analysis revealed that it crystallizes as a kryptoracemate of sesquihydrate chiral crystals in the orthorhombic noncentrosymmetric space group P212121 (Z = 8, Z′ = 2). Two diastereomeric cationic complexes with opposite configuration reside within the asymmetric unit. KBr pellets prepared using selected single crystals showed enantiomorphous circular dichroism patterns.