Chiral one-dimensional O–P–O bridged MnIII-Schiff base complexes

Abstract

Two couples of enantiomerically pure metal phosphonates are successfully synthesized by using chiral Mn^III-Schiff base mononuclear precursors. Compounds [Mn((R,R)-5-Brsalcy)(2-FC₆H₄PO₃H)]·3H₂O (1) and [Mn((R,R)-5-Brsalcy)(4-CH₃C₆H₄PO₃H)]·CH₃OH·H₂O (3) [5-Brsalcy = N,N′-(1,2-cyclohexanediylethylene)bis(5-bromosalicylideneiminato) dianion] are isostructural and show similar one-dimensional chain structures where the Mn((R,R)-5-Brsalcy)⁺ species are bridged by O–P–O units. Compounds 2 and 4 are (S,S)-enantiomers of 1 and 3, respectively. These compounds are all optically active, exhibiting second harmonic generation responses 0.3 times that of urea. The magnetic measurements of 1 and 3 reveal that dominant antiferromagnetic interactions are mediated between the Mn^III centers.