Chiral matrix effect of optically active oxalate-based networks: controlled helical conformation of an organic chromophore

Abstract

Optically active two-dimensional (2D) MIPS[Mn IIM III(C 2O 4) 3] bimetallic networks with MIPS = 4-[4-methoxy-α-styryl]- N-isopentylpyridinium and M III = Cr, Co were obtained using as chiral inducing reagents the resolved (Δ)- or (Λ)-[M III(C 2O 4) 3] 3− building blocks. The correlation of the natural circular dichroism (NCD) of these 2D networks with their UV–vis properties demonstrates that the [Mn IIM III(C 2O 4) 3] − anionic network has a chiral matrix effect on the MIPS + cation: the choice of the configuration of the starting tris(oxalato)metallate(III) determines the helical conformation of the MIPS + cation. Such a conformation of the cation sharply contrasts with the perfectly planar geometry observed by X-ray diffraction in MIPSBr.