Engineering of a kinetically driven phase of phenoxazine by surface crystallisation

Kaltenegger, Martin; Hofer, Sebastian; Resel, Roland; Werzer, Oliver; Riegler, Hans; Simbrunner, J.; Winkler, Christian; Geerts, Yves; Liu, Jie

doi:10.1039/d2ce00479h

Cited by 3 publications

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“…In addition, the layered morphology of the CCOFs observed by SEM and TEM suggests that 2D topologies are more rational (Figures a and S3). Notably, the observation of exclusively (5–10) peaks for both CCOFs suggests a preferred orientation of crystalline particles . This is evidenced by the fact that the preferred orientation effect can be partly reduced by rotation of the sample in a capillary in collecting PXRD data (Figure S6).…”

Section: Resultsmentioning

confidence: 90%

“…Notably, the observation of exclusively (5−10) peaks for both CCOFs suggests a preferred orientation of crystalline particles. 35 This is evidenced by the fact that the preferred orientation effect can be partly reduced by rotation of the sample in a capillary in collecting PXRD data (Figure S6). In addition, the PXRD patterns of two CCOFs on other possible structures were calculated, but all the calculated patterns did not match the experimental patterns (Figures S7 and S8).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation

et al. 2023

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Privileged diphosphine ligands that chelate many transition metals to form stable chelation complexes are essential in a variety of catalytic processes. However, the exact identity of the catalytically active moieties remains ambiguous because the chelated metal catalysts may undergo rearrangement during catalysis to produce monophosphine–metal complexes, which are hard to isolate and evaluate the activities. By taking advantage of the isolation of two phosphorus atoms, we demonstrate here the successful construction of chiral monophosphine–Ir/Ru complexes of diphosphine ligands in covalent organic frameworks (COFs) for enantioselective hydrogenation. By condensation of the tetraaldehyde of enantiopure MeO-BIPHEP and linear aromatic diamines, we prepare two homochiral two-dimensional COFs with ABC stacking, in which the two P atoms of each diphosphine are separated and fixed far apart. Post-synthetic metalations of the COFs thus afford the single-site Ir/Ru–monophosphine catalysts, in contrast to the homogeneous chelated analogues, that demonstrated excellent catalytic and recyclable performance in the asymmetric hydrogenation of quinolines and β-ketoesters, affording up to 99.9% enantiomeric excess. Owing to the fact that the porous catalyst is capable of adsorbing and concentrating hydrogen, the catalytic reactions are promoted under ambient/medium pressure, which are typically performed under high pressure for homogeneous catalysis. This work not only shows that monophosphine–metal complexes of diphosphines can be catalytically active centers for asymmetric hydrogenation reactions but also provides a new strategy to prepare new types of privileged phosphine-based heterogeneous catalysts.

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Section: Resultsmentioning

confidence: 90%

Section: ■ Results and Discussionmentioning

confidence: 99%

Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation

et al. 2023

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“…22 Crystallization can also be carried out under spatial confinement, such as in nano-pores 23,24 or at substrate surfaces. [25][26][27] Utilizing solid surfaces as nucleation templates is undoubtedly a promising strategy for discovering new forms. [28][29][30] In some systems, the adaptation of the molecular packing to a substrate surface leads to an entropy reduction and thereby results in the formation of new phases.…”

Section: Materials Horizonsmentioning

confidence: 99%

“…[31][32][33] Thus molecular crystals nucleating in the proximity of a surface may organise differently, and these new phases are not accessible otherwise. 27 Therefore, it is vital to integrate this feature into the polymorph screening process.…”

Section: Materials Horizonsmentioning

confidence: 99%

Polymorph screening at surfaces of a benzothienobenzothiophene derivative: discovering new solvate forms

et al. 2023

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Indexing of grazing-incidence X-ray diffraction patterns

Simbrunner

Salzmann

Resel

2023

Crystallography Reviews

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Engineering of a kinetically driven phase of phenoxazine by surface crystallisation

Abstract: The appearance of different polymorphs at surfaces is a well-known phenomenon for organic molecules. Here the molecule phenoxazine, a small molecule with a rather rigid conformation whose bulk crystal structure...

Cited by 3 publications

References 77 publications

Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation

Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation

Polymorph screening at surfaces of a benzothienobenzothiophene derivative: discovering new solvate forms

Indexing of grazing-incidence X-ray diffraction patterns

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