Linker-dependent control of the chiroptical properties of polymethylene-vaulted trans -bis[(β-iminomethyl)naphthoxy]platinum(II) complexes.

The effects of polymethylene bridges on the chiroptical properties of trans -bis[(β-iminomethyl)naphthoxy]platinum(II) platforms were examined both experimentally and theoretically using newly designed planar chiral Pt analogues (1) having three-dimensional superstructures. A series of optically pure polymethylene-vaulted Pt complexes ( R )- and ( S )-1 were synthesized and characterized with regard to the chiroptical behaviour of the trans -bis[(β-iminomethyl)naphthoxy]platinum(II) platforms. These complexes were found to exhibit structure-dependent chiroptical characteristics in solution, such that the absolute values of specific rotation, the circular dichroism dissymmetry factor ( g abs ) and the circularly polarized luminescence dissymmetry factor ( g lum ) all increased upon shortening the polymethylene bridges. Density functional theory and time dependent density functional theory calculations were used to analyse vaulted and non-vaulted complexes, which demonstrated that the present linker-dependent chiroptical properties resulted from constraint-induced changes in the square planar Pt coordination centres rather than from chiral distortion along the coordination platforms.