Construction of helical coordination polymers via flexible conformers of bis(3-pyridyl)cyclotetramethylenesilane: metal(ii) and halogen effects on luminescence, thermolysis and catalysisElectronic supplementary information (ESI) available: TGA and DSC curves of the present complexes; SEM images, powder XRD patterns, and SEM-EDX data for zinc(ii) oxide; 1H NMR spectra on the procedure of transesterification of phenyl acetate in methanol using the present complexes as catalysts. CCDC 1047992-10479

Infinite rectangular-tubular helices, [MX 2 L] (M = Zn( ii ), Hg( ii ); X − = Cl − , Br − ; L = bis(3-pyridyl)cyclotetramethylenesilane), have been efficiently constructed via the combined effects of the potential flexible conformers of L and the tetrahedral geometry of M( ii ) ions. This helical molecular system affords a racemic mixture of P - and M -helices in a crystal. The helical pitches (7.8934(4)-8.1560(2) Å) that are sensitive to the nature of M( ii ) ions and halide anions are attributable to subtle change in the flexible dihedral angles between the two pyridyl groups around Si and the M( ii ) hinges. Their photoluminescence intensities, correspondingly, are in the order [ZnCl 2 L] > [ZnBr 2 L] > [HgCl 2 L] > [HgBr 2 L]. Zinc( ii ) complexes show recyclable catalytic effects on the transesterification reaction in the order [ZnCl 2 L] > [ZnBr 2 L]. Calcination of [ZnCl 2 L] and [ZnBr 2 L] at 500 °C produces uniform hexagonal tubular spire crystals of 1.2 × 1.2 × 4.0 μm 3 dimensions and spheres, respectively. Construction and physicochemical properties of rectangular-tubular-helical coordination polymers of [M( ii )X 2 L] (M = Zn( ii ), Hg( ii ); X − = Cl − , Br − ) were investigated.