A New Star-shaped Carbazole Derivative with Polyhedral Oligomeric Silsesquioxane Core: Crystal Structure and Unique Photoluminescence Property

Synthesis, Crystal Structure, Fluorescence and Theoretical Calculations of Three Zn(II)/Cd(II) Complexes with Bis-dentate N,N-Quinoline Schiff Base

Three d10 metal complexes, ZnL(OAc)2 (1), CdL(OAc)2 (2) and [CdL2(NO3)2]·CH3CN (3) were synthesized using the ligand (E)-N-(3-methoxy-4-methylphenyl)-1-(quinolin-2-yl)methanimine (L) and characterized by FT-IR spectra, NMR spectra, and CHN elemental analysis. Single-crystal X-ray diffraction analysis revealed that complexes 1 and 2 are isostructural, with the central metal adopting a hexacoordinate octahedral geometry, while complex 3 adopts a triangular dodecahedron geometry. Thermal gravimetric analysis showed that these complexes exhibit good thermal stability. Solid-state fluorescence spectroscopy measurements demonstrated that complexes 1-3 exhibit bright yellow-green fluorescence (λem = 564 nm for 1; 524 nm for 2; 542 nm for 3), suggesting their potential as photoluminescent materials. Furthermore, DFT calculations, including frontier molecular orbitals, energy levels, and surface electrostatic potential, provided insights into the structural and electronic spectral properties of complexes 1-3.

Functionalization of octaspherosilicate (HSiMe2O)8Si8O12 with buta-1,3-diynes by hydrosilylation

Hydrosilylation with octaspherosilicate (HSiMe2O)8Si8O12 (1) has provided hundreds of molecular and macromolecular systems so far, making this method the most popular in the synthesis of siloxane-based, nanometric, cubic, and reactive building blocks. However, there are no reports on its selective reaction with 1,3-diynes, which allows for the formation of new products with unique properties. Therefore, herein we present an efficient protocol for monohydrosilylation of symmetrically and non-symmetrically 1,4-disubstituted buta-1,3-diynes with 1. The compounds obtained bear double and triple bonds and other functionalities (e.g., Br, F, OH, SiR3), making them highly desirable, giant building blocks in organic synthesis and material chemistry. These compounds were fully characterized by 1H, 13C, 29Si, 1D NOE, 1H-13C HSQC NMR, FT-IR, and MALDI TOF MS, EA, UV-Vis, and TGA analysis. The TGA proved their high thermal stability up to 427 ℃ (Td10%) for compound 3j.

Blue Emission of Tetrafluorobenzocarbazole Under the Interactions of Nitrogen–oxygen Saturated hydrogen Bonds with Aggregated Proton Acid

Two novel tetrafluorobenzocarbazole and containing the amino branch introduced at the end of the molecule are synthesized by a simple method. The tetrafluorobenzocarbazole as the electron donor with electron-rich fluoride ions connected by π-benzyl ring conjugation structure, which affects the overall electron cloud density. Moreover, the amino branch introduced at the end of the molecule, which makes it easy to form intermolecular hydrogen bonds and affected photophysical properties. Meanwhile, the photophysical property of both compounds are discussed under different acidic conditions. The UV-absorption show that around ~286 nm is mainly attributed to the strong structural absorption band peak of the π-π ∗ transition of the carbazole moiety, and the irregular absorption band around ~314 nm and ~326 nm are mainly attributed to the n-π ∗ transition of the carbazole group conjugate with the adjacent molecule. The emission spectrum of both compounds showed that the intensity of fluorescence decreased in different degrees after the addition of the acidic solution. Furthermore, the electrochemical properties were evidenced by cyclic voltammetry (CV) and density functional theory (DFT) calculations, and the orbital conformation (HOMOs-LUMOs) was simulated by Gaussian 09 software and its crystal structure was observed by X-ray diffraction (XRD). The results exhibited that both compounds are electrochemically stable blue small-molecule fluorescent substances, and expected that both compounds can be novel and stable acid-sensitive organic blue-light materials.

Design of Fluorescent Hybrid Materials Based on POSS for Sensing Applications

Polyhedral oligomeric silsesquioxane (POSS) has a nanoscale silicon core and eight organic functional groups on the surface, with sizes from 0.7 to 1.5 nm. The three-dimensional nanostructures of POSS can be used to build all types of hybrid materials with specific performance and controllable nanostructures. The applications of POSS-based fluorescent materials have spread across various fields. In particular, the employment of POSS-based fluorescent materials in sensing application can achieve high sensitivity, selectivity, and stability. As a result, POSS-based fluorescent materials are attracting increasing attention due to their fascinating vistas, including unique structural features, easy fabrication, and tunable optical properties by molecular design. Here, we summarize the current available POSS-based fluorescent materials from design to sensing applications. In the design section, we introduce synthetic strategies and structures of the functionalized POSS-based fluorescent materials, as well as photophysical properties. In the application section, the typical POSS-based fluorescent materials used for the detection of various target objects are summarized with selected examples to elaborate on their wide applications.

Spectroscopic Study of Aggregation of Carbazole Units

Several fluorescence spectral features in aggregation of carbazole unites have been reported in previous study. Unfortunately, the influence of inner filter effect has not been paid enough attention. In this work, aggregation of carbazole unites resulting from increasing concentration or decreasing solvent affinity, was investigated by fluorescence spectroscopy. Through comparison between the spectra of two aggregation processes, it is found that only intensity ratio of 0-0 transition to 0-1 transition in excitation/emission spectra is sensitive to aggregation states. There is an obvious decrease in that intensity ratio upon aggregation. On the other hand, other spectral features observed in previous research such as intensity decrease in S₀ → S₂ transition and emission quenching in concentration induced aggregation process, should be induced by inner filter effect. Graphical Abstract.

An overview on synthetic strategies for the construction of star-shaped molecules

Strategies for the synthesis of star-shaped molecules have been in high demand in the last decades due to the importance of those compounds in various fields. The distinctly different properties of these compounds compared to their linear analogues make them versatile building blocks for the formation of mesophases of interesting mesomorphic and photophysical properties. Moreover, the applications of star-shaped molecules as building units for dendrimers as well as in supramolecular host-guest chemistry have also been recently studied. The star-shaped molecules mentioned in this review are classified according to the central core as well as the type of side arms. The properties and applications of these compounds are described in the appropriate contexts. This report summarizes the recent advances in this area.

Antimicrobial activities of self-assembled copper(ii), nickel(ii), and cobalt(iii) complexes combined with crystallographic, spectroscopic, DFT calculations and Hirshfeld surfaces analyses

Three 2-D and 3-D Cu(ii), Ni(ii), and Co(iii) complexes were obtained by reaction of HL1 with different metal salts. The complexes were characterized by single-crystal X-ray crystallography and spectroscopic methods, as well as Hirshfeld surface analysis and DFT studies.

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe2 O)8 Si8 O12

Comprehensive studies on platinum-catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe2 O)8 Si8 O12 (1 a) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2-(E)-disubstituted and 1,1,2-(E)-trisubstituted alkenyl-octaspherosilicates (3 a-m, 6 n-t) were selectively obtained with high yields, and fully characterized (1 H, 13 C, 29 Si NMR, FTIR, MALDI TOF or TOF MS ES+ analysis). Moreover, the molecular structure of the compound (Me3 Si(H)C=C(H)SiMe2 O)8 Si8 O12 (3 a) was determined by X-ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a, as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si-O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star-shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied.