Unprecedented regioselective post-functionalization of racemic and enantiopure cationic diaza [4]helicenes is afforded.

Physicochemical properties of cationic dioxa 1, azaoxa 2 and diaza 3 [6]helicenes demonstrate a much higher chemical stability of diaza adduct 3 (pKR+ 20.4, E1false/2red −0.72 V) compared to azaoxa 2 (pKR+ 15.2, E1false/2red −0.45 V) and dioxa 1 (pKR+ 8.8, E1false/2red −0.12 V) analogues. The fluorescence of these cationic chromophores was established and ranges from the orange to the far-red regions. From 1 to 3, a bathochromic shift of the lowest energy transitions (up to 614 nm in acetonitrile) and an enhancement of the fluorescence quantum yields and lifetimes (up to 31% and 9.8 ns at 658 nm) are observed. The triplet quantum yields and the circularly polarized luminescence are also reported. Finally, fine tuning of the optical properties of the diaza [6]helicene core was achieved through selective and orthogonal post-functionalization reactions (12 examples, compounds 4-15). The electronic absorption is modulated from the orange to far-red spectral range (560-731 nm) while fluorescence is observed from 591 to 755 nm with enhanced quantum efficiency up to 70% (619 nm). The influence of the peripheral auxochrome substituents is rationalized by first-principles calculations.

The inherent porous nature and facile tunability of metal-organic frameworks (MOFs) make them ideal candidates for use in multiple fields. MOF hybrid materials are derived from existing MOFs hybridized with other materials or small molecules using a variety of techniques. This led to superior performance of the new materials by combining the advantages of MOF components and others. In this review, we discuss several hybridization methods for the preparation of various MOF hybrids with representative examples from the literature. These methods include covalent modifications, noncovalent modifications, and using MOFs as templates or precursors. We also review the applications of the MOF hybrids in the fields of catalysis, drug delivery, gas storage and separation, energy storage, sensing, and others. Crystals 2018, 8, 325 2 of 23to coordinate to other materials. In addition to covalent modifications, MOF hybrids can also be made via noncovalent interactions, such as encapsulation [19,20], layer-by-layer deposition [21], and in situ growth [22]. These methods take advantage of noncovalent interactions between MOFs and the hybridizing species by trapping the species within the MOF pores, layering them on top of the parent MOF, or growing MOFs crystals in situ with the species. Noncovalent modification allows the individual characteristics of the MOF and hybridizing materials to work synergistically in the resultant MOF hybrids while requiring less synthetic efforts than covalent modifications. These methods can be used to achieve materials with MOF coating/protection, multi-layered membranes, and the controlled growth of MOF structures with superior performance than individual parent materials. Finally, hybridizing MOFs through use as either sacrificial templates [23] or precursors [24] utilizes the ordered structure of MOFs to afford porous materials with high surface areas and uniform pore sizes. This method eliminates the metal node and/or the organic linker, leaving behind only the newly synthesized materials with the inherited uniform nanoframe of the template/precursor MOF.In this review, we discuss each hybridization method with representative MOF hybrids from literature, as well as the hybrid materials' superior performances and applications. At the end of this review, we also summarize all reported MOF hybrid materials. Crystals 2018, 8, x FOR PEER REVIEW 2 of 22

Racemic sample of 2,2’,7,7’-tetrahydroxy-1,1’-binaphthyl was resolved with (S)-proline and the separated enantiomers were independently converted to atropisomeric bis-oxazines by aromatic Mannich reaction. These chirally pure oxazines were then converted to the helicene like cyclic ethers. The Circularly Polarized Luminescence (CPL) profile was consistent with the isolation of the targeted helical-like molecules in optically pure form, prepared from the achiral primary amines. The compounds of interest displayed active and opposite CPL activities for each sets of the helicene like isomers (P)-/(M)-3 and (P)-/(M)-5.

The R,R and S,S enantiomers of N,N'‐bis(1‐phenylpropyl)‐2,6‐pyridinedicarboxamide, L(Et), react with Ln3+ ions (Ln = La, Eu, Gd, and Tb) to give stable [Ln((R,R)‐ and (S,S)‐L(Et))3]3+ in anhydrous acetonitrile solution, as evidenced by various spectroscopic measurements, including NMR and luminescence titrations. In addition to the characteristic Eu3+ and Tb3+ luminescence bands, the steady‐state and time‐resolved luminescence spectra of the aforementioned complexes show the residual ligand‐centered emission of the 1ππ* to 3ππ* states, indicating an incomplete intersystem crossing (ISC) transfer from the 1ππ* to 3ππ* and ligand‐to‐Ln3+ energy transfer, respectively. The high circularly polarized luminescence (CPL) activity of [Eu(L(Et))3]3+ confirms that using a single enantiomer of L(Et) induces the preferential formation of one chiral [Eu(L(Et))3]3+ complex, consistent with the [EuL3]3+ complexes formed with other ligands derived from a 2,6‐pyridine dicarboxamide moiety. Furthermore, the CPL sign patterns of complexes with (R,R) or (S,S) enantiomer of L(Et) are consistent with the CPL sign pattern of related [LnL3]3+ complexes with the (R,R) or (S,S) enantiomer of the respective ligands in this family.