Authors: Wei Ying | Qiujing Bao | Zheng Zhang | Hao Li | Shuwei Ma | Tao Wang | Linghai Xie
Source: Chinese Science Bulletin (Chinese Version) (article, 2023-11-30)
Field: Materials Science — Materials Chemistry

Research progress on spirofluorene-based closed-loop compounds <p indent="0mm">In 1930, Clarkson first synthesized 9,9′-spirobifluorene. With the in-depth research on spirobifluorene structures, various types of spiro-ring molecules have been expanded, including spiro[fluorene-9,9′-xanthene], spiro[indene-thiophene]fluorenes, and spiro[cyclopentadithiophene]fluorenes. These molecules are renowned for their unique rigid π-conjugated orthogonal configuration and multi-reactive site molecular skeleton, making them valuable building blocks in the field of organic optoelectronic materials. They are commonly employed in the synthesis of organic functional small molecules, linear polymers, and closed-loop compounds. Spirofluorene-based closed-loop compounds are a class of molecules constructed using spirofluorene as the core unit. They mainly include macrocycles, nanogrids, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and other related structures. These compounds possess well-defined cyclic structures, tunable sizes and shapes, diverse conformational and optical properties, and find widespread applicationss in fields such as sensing, drug delivery, adsorption, separation, optical devices, molecular recognition, and other fields. Overall, the advancements in spirofluorene chemistry have opened up new possibilities for the design and development of functional materials with enhanced properties and wide-ranging applications. Depending on the spatial dimensions of these compounds, they can be classified into zero-, one-, two-, and three-dimensional spirofluorene-based closed-loop structures, each dimension exhibiting distinct properties and applications. Zero-dimensional structures refer to compounds with nanoscale dimensions in one direction, featuring closed-loop compound with spirofluorenes as the core units, including macrocycles and nanogirds. They demonstrate excellent molecular recognition properties and are often designed for selective recognition and detection of specific molecules, holding potential applications in environmental monitoring and medical diagnostics. One-dimensional structures have nanoscale cross-sectional areas and macroscopic lengths. They primarily include linear polymer networks and polyacenes. These structures display high structural regularity and are commonly used in the preparation of sensing and separation materials, with broad applications in optoelectronics, environmental science, and other fields. Two-dimensional structures involve two directions reaching nanoscale in space, encompassing conjugated microporous polymers, COFs, and MOFs. These structures offer abundant adsorption sites that enhance interactions between gases and materials, enabling efficient gas adsorption. They are commonly used in the preparation of gas adsorption materials. Three-dimensional structures refer to those reaching nanoscale in all three directions in space, mainly including COFs and MOFs. These compounds combine the high activity of metals, flexibility of organic ligands, and selectivity of functional groups, making them excellent candidates for applications in gas adsorption and catalysis. By understanding the spatial dimensions and properties of spirofluorene-based closed-loop compounds, researchers can tailor their designs to meet specific application requirements in fields such as molecular recognition, sensing, gas adsorption, separation, catalysis, and more. In recent years, significant progress has been made in the synthesis methods for spirofluorene-based closed-loop compounds. A series of efficient, economical, and environmentally friendly methods have emerged, including Sonogashira coupling, Yamamoto coupling, Suzuki-Miyaura coupling, C−H activation, and Buchwald-Hartwig coupling reactions. Generally, spirofluorene-based closed-loop compounds show promising applications in various fields. We believe that with further research and technological development, these compounds are expected to achieve significant breakthroughs in structural design, performance optimization, and innovative applications, providing more opportunities across various fields such as materials science, flexible electronics, and medicine. Therefore, this article reviews the recent advances in the study of spirofluorene-based closed-loop compounds, with a focus on their structural characteristics, synthetic methods, property characterization, and applications. This research provides robust support for the design and preparation of new materials with more functionalities in the fields such as chemistry, materials science, life sciences, organic optoelectronics, and other related fields. Closed loop ; Loop (graph theory) ; Biochemical engineering ; Chemistry ; Computational biology ; Computer science ; Mathematics ; Biology ; Engineering ; Control engineering ; Combinatorics Luminescence and Fluorescent Materials ; Supramolecular Chemistry and Complexes ; Covalent Organic Framework Applications