Tetrahedral Zinc Complexes with Liquid Crystalline and Luminescent Properties:  Interplay Between Nonconventional Molecular Shapes and Supramolecular Mesomorphic Order

Abstract

Novel metallomesogens with luminescent properties and liquid crystalline behavior at room temperature have been achieved by the preparation of zinc complexes with polycatenar pyrazole and bis(pyrazolyl)methane ligands. Their molecular structures do not have a conventional shape in that they are far from the typical rod-like and flat disc-like geometries of common liquid crystals. They consist of a nonplanar nucleus due to the methylene spacer and/or the coordination to the tetrahedral center, as confirmed by single crystal analysis of the cores. The different numbers and positions of side chains in the pyrazole ligand enabled us to access lamellar and columnar mesophases and, of particular interest, to obtain columnar arrangements at room temperature. Supramolecular models for the organization of the molecules in the mesophases are proposed on the basis of the small-angle XRD diffractograms. The zinc complexes display luminescence in the near UV-blue region with large Stokes shifts. An interplay between non-conventional molecular shapes (due to the tetrahedral core) and the supramolecular mesomorphic order (due to the ligand design) led to materials that interestingly embody two rather opposite properties, a columnar self-organizational ability and luminescence with weak intermolecular interactions.

Regioselective One‐Step Synthesis of Pyrazoles from Alkynes and N‐Tosylhydrazones: [3+2] Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement Cascade

“…[2] Examples of leading commercial drugs based on the pyrazole scaffold include celecoxib, [3] lonazolac, [4] and rimonabant. [5] Currently, pyrazoles are constantly employed as building blocks in drug discovery programs, [6] and are also found as key constituents of ligands for transition metals, [7] receptors in supramolecular chemistry, [8] liquid crystals, [9] and polymers. [10] For these reasons, the development of new methodologies for the regioselective synthesis of polysubstituted pyrazoles continues to be an active area of research of high impact in fine chemistry.…”

“…Angewandte Zuschriften (Scheme 4), thus giving rise to the benzocycloheptapyrazoles 9, which correspond to the rearrangement of the sp 2 -carbon atom to C4. Benzocycloheptapyrazoles (9) are interesting intermediates which could be further elaborated through functionalization or oxidation of the double bond. For instance, the ozonolysis of 9 a led to the densely functionalized tetrahydropyridinopyrazole 10 in quantitative yield.…”

Synthesis, Crystal Structure and Luminescent Property of A Novel Cd(II) Coordination Polymer with Bis-imidazole Ligand

“…[18][19][20] It has been demonstrated that incorporation of fluorescent organic molecules into metal-organic frameworks has, in some cases, led to significant enhancements of fluorescent intensities compared to its free ligands. 21,22 Furthermore, metal-organic frameworks can offer the advantages of higher thermal stability and solvent resistance compared to the all-organic materials.…”

Ag/Tio2 Nano Thin Films Catalyzed Efficient Synthesis of 6-Amino-4-Aryl-3-Methyl-1,4-Dihydropyrano[2,3-C] Pyrazole-5-Carbonitriles At Green Conditions

“…In addition pyrazoles have been used for treatment of type 2 diabetes, obesity, thrombopiotinmimetics and antiangiogenesis because of their kinase inhibitory effects 20 . Furthermore, some pyrazoles are employed in polymer and supramolecular chemistry, in the food industry, and as UV stabilizers and cosmetic colorings and in some cases it was observed that these compounds also have liquid crystal properties [21][22][23][24][25] . Dihydropyrano [2,3-c]pyrazoles, are one of the most important pyrazole compounds and they have received considerable attention owing to their biological activity and they have been utilize as a template for medicinal chemistry.…”