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Abstract: Solid-state luminescent materials that possess reversible fluorescence changes toward external multistimuli are of immense interest because of their potential applications in data storage and sensors. While the recent developments in this field are mainly focused on the π-conjugated organic molecules. Herein two polymorphic luminescent ionic liquid (IL)-based stimuli-responsive materials were designed by the supramolecular assemblies of an organic-decorated chlorobismuthate anion and a rotationally flexible imidazolium cation, namely, α (1)/β (2)-[Bmmim][BiCl4(2,2′-bpy)] (Bmmim = 1-butyl-2,3-dimethylimidazolium; 2,2′-bpy = 2,2′-bipyridine). Because of the different conformations of the n-butyl chains on the imidazolium cations, tuning of the supramolecular packing structures as well as luminescent colors for 1 and 2 was realized. Single-crystal X-ray diffraction and Hirshfeld surface analyses disclose that the polymorphism-dependent emission may be attributed to the different weak interactions, especially to the π–π interactions between adjacent [BiCl4(2,2′-bpy)]− anions in two compounds. Additionally, compound 2 could be transformed into 1 spontaneously at ambient conditions, which could be triggered by the moisture in the air. Both of the title compounds could detect NH3 vapor selectively through the luminescence “turn-off” method rapidly and reversibly because of the destruction of intermolecular interactions, indicating their stimuli-responsive property toward NH3.

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Abstract: This present PhD Thesis has been dedicated to the exploration and study the solid-gas phase ozonolysis as a quick, simple and versatile method for post-synthetic modification of metal-organic frameworks (MOFs). In the first Chapter, a brief introduction to the origin of MOFs is given, followed by typical concepts for design and synthesis of the porous materials. We then pay special attention to the current methodologies that used for post-synthesic modifications of MOFs with state-of-the-art advancements and selected examples, aiming to place the reader in the context of the thesis. Additionally, the main applications of post-synthetically functionalized MOFs are provided. In Chapter 2, the general and specific objectives of the Thesis are introduced. In Chapter 3, we develop a new post-synthetic methodology for functionalization of MOFs based on the solid-gas ozonolysis. The generated ozonide rings are identified by nuclear magnetic resonance (NMR) technique. Moreover, the generality of this method has been proven by a single-crystal-to-single-crystal transformation, as confirmed by single-crystal X-Ray diffraction together with density functional theory (DFT) calculation. Finally, the amenability of ozonide functionality is demonstrated by selectively workup treatment. Chapter 4 extends the use of the solid-gas ozonolysis to post-synthetic modification of MOF porosity. We show that, by carefully selecting mixed-ligand Zr-fcu-MOFs based on organic ligand pairs in which one ligand has ozone-cleavable olefin bonds and the other ligand is ozone-resistant, we were able to selectively break the cleavable ligand via ozonolysis to trigger fusion of micropores into mesopores within MOF framework. Thus, the mesoporous MOFs are subsequently created through removal of ligand fragments by washing or sublimation, as evidenced by their distinct gas sorption properties.

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Abstract: A new method for the stereoselective synthesis of highly functionalized oxygen heterocycles using allyl or benzyl alcohols as alkylating agents is presented. The process is efficient and atom economic, generating water as the only stoichiometric byproduct. Substoichiometric amounts of Ti(OiPr)4 in HFIP solvent are key to this reactivity, and the method tolerates a broad substitution pattern on both the alcohol initiator and homoallylic alcohol substrate. Preliminary mechanistic studies reveal in situ formation of a titanium complex with HFIP which may initiate the cyclization reaction. Further stereoselective functionalization of the products allows access to a diverse range of interesting heterocyclic structures.

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Abstract: The exceptional performance of oxobenzene-bridged bis-1,2,3-dithiazolyls 6 as single-component neutral radical conductors arises from the presence of a low-lying π-lowest unoccupied molecular orbital, which reduces the potential barrier to charge transport and increases the kinetic stabilization energy of the metallic state. As part of ongoing efforts to modify the solid-state structures and transport properties of these so-called multiorbital materials, we report the preparation and characterization of the acetoxy, methoxy, and thiomethyl derivatives 6 (R = OAc, OMe, SMe). The crystal structures are based on ribbonlike arrays of radicals laced together by S···N′ and S···O′ secondary bonding interactions. The steric and electronic effects of the exocyclic ligands varies, affording one-dimensional (1D) π-stacked radicals for R = OAc, 1D cofacial dimer π-stacks for R = SMe, and a pseudo two-dimensional (2D) brick-wall arrangement for R = OMe. Variable-temperature magnetic and conductivity measurements reveal strong antiferromagnetic interactions and Mott insulating behavior for the two radical-based structures (R = OAc, OMe), with lower room-temperature conductivities (σRT ≈ 1 × 10–4 and ∼1 × 10–3 S cm–1, respectively) and higher thermal activation energies (Eact = 0.24 and 0.21 eV, respectively) than found for the ideal 2D brick-wall structure of 6 (R = F), where σRT ≈ 1 × 10–2 S cm–1 and Eact = 0.10 eV. The performance of R = OMe, OAc relative to that of R = F, is consistent with the results of density functional theory band electronic structure calculations, which indicate a lower kinetic stabilization energy of the putative metallic state arising from their reduced electronic dimensionality.

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Abstract: Hierarchically nested hosts offer new opportunities to control the guest binding of the inner host, functionalize the cavity of the outer host, and investigate communication between different layers. Here we report a self-assembled triazatruxene-based FeII4L4 capsule, which was able to encapsulate a covalent cage, cryptophane-111 (CRY). The resulting cage-in-cage complex was capable of accommodating a cesium cation or xenon atom with altered guest binding behavior compared to the CRY alone. A crystal structure of the Russian doll complex [Cs+⊂CRY]⊂FeII4L4 unambiguously demonstrated the unusual encapsulation of a cation within a capsule bearing a 8+ charge. Moreover, the binding of enantiopure CRY occurred with high enantioselectivity (530-fold) between the two enantiomers of the tetrahedron. This discrimination resulted in stereochemical information transfer from the inner covalent cage to the outer self-assembled capsule, leading to the formation of enantiopure [guest⊂cage]⊂cage complexes. The stereochemistry of the tetrahedron persisted even after displacement of CRY with an achiral guest.