A cooperative chiral salen Ti^IV catalyst was prepared by covalently appending multiple chiral salen Ti^IV complexes on a graphene oxide (GO) surface through a flexible ionic liquid (IL) linker. Characterization results confirmed the decoration of intact Ti(salen) units on the edges and planes of exfoliated GO with the imidazolium-IL spacer. The IL-functionalized GO nanosheets endowed the chiral salen Ti^IV catalyst with high water-dispersion, diminished diffusion limitation, and particularly a reinforced intramolecular cooperative effect. The cooperative catalyst was thus highly efficient and universally applicable in the catalysis of asymmetric sulfoxidation in water, affording high yields of various chiral sulfoxides with excellent enantioselectivities, while traditional chiral salen Ti^IV complex was far less active. More importantly, the heterogeneous catalyst was perfectly stable and could be reused several times without significant loss of activity and selectivity.

中文翻译：

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离子液体官能化氧化石墨烯上负载的手性合作Salen Ti ^IV催化剂促进水中的不对称硫氧化

通过将多个手性Salen Ti ^IV配合物通过柔性离子液体（IL）连接剂共价附着在氧化石墨烯（GO）的表面上，制备了手性Salen Ti ^IV协同催化剂。表征结果证实了用咪唑-IL间隔基修饰剥落的GO的边缘和平面上完整的Ti（salen）单元的装饰。IL功能化的GO纳米片赋予了手性Salen Ti ^IV具有高水分散性的催化剂，减少了扩散限制，特别是增强了分子内的协同作用。因此，该合作催化剂是高效的，并且普遍适用于催化水中的不对称硫氧化，可提供高收率的各种具有优良对映选择性的手性亚砜，而传统的手性Salen Ti ^IV络合物的活性则低得多。更重要的是，非均相催化剂是完全稳定的，可以重复使用几次，而不会显着降低活性和选择性。