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

Optically active two-dimensional (2D) MIPS[(MnMIII)-M-II(C2O4)(3)] bimetallic networks with MIPS = 4-[4-methox-alpha-styryl]-N-isopentylpyridinium and M-III = Cr, Co were obtained using as chiral inducing reagents the resolved (Delta)- or (Lambda)-[M-III(C2O4)(3)](3-) building blocks. The correlation of the natural circular dichroism (NCD) of these 2D networks with their UV-vis properties demonstrates that the [(MnMIII)-M-II(C2O4)(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. (C) 2004 Elsevier Ltd. All rights reserved.