Synthesis, Structural Characterization, and Optical Properties of Benzene-Fused Tetracyclic and Pentacyclic Stiboles.

Mio Matsumura,Yuki Murata,Kentaro Yamaguchi,Masatoshi Kawahata,Masato Kawakubo,Tadashi Hyodo,Yuki Matsuhashi,Shuji Yasuike

doi:10.3390/molecules26010222

Mio Matsumura, Yuki Murata + Show 6 more

Open Access

https://doi.org/10.3390/molecules26010222

Copy DOI

Abstract

The expectation that antimony (Sb) compounds should display phosphorescence emissions based on the “heavy element effect” prompted our interest in the introduction of antimony to a biaryl as the bridging atom in a fused heterole system. Herein, the synthesis, molecular structures, and optical properties of novel benzene-fused heteroacenes containing antimony or arsenic atoms are described. The stiboles and arsole were prepared by the condensation of dibromo(phenyl)stibane or dichloro(phenyl)arsine with dilithium intermediates derived from the corresponding dibromo compounds. Nuclear magnetic resonance (NMR) spectroscopy and X-ray crystal analysis revealed that the linear pentacyclic stibole was highly symmetric in both the solution and crystal states. In contrast, the curved pentacyclic stibole adopted a helical structure in solution, and surprisingly, only M helical molecules were crystallized from the racemate. All synthesized compounds produced very weak or no emissions at room temperature or in the solid state. In contrast, the linear penta- and tetracyclic stiboles exhibited clear phosphorescence emissions in the CHCl3 frozen matrix at 77 K under aerobic conditions.

Highlights

The development of novel π-conjugated systems and the elucidation of their optical properties to realize desired behaviors and functionalities are of current importance in the field of organic optoelectronic materials
Arsoles, containing the homologous element, arsenic, have been reported as luminescent substances that are less likely to be oxidized than phospholes, toxicity is a concern [7,8,9,10,11]. Another homologue located in the fifth period of group 15 elements in the periodic table, is expected to impart phosphorescence to bismuth and tellurium based on the “heavy element effect”, in contrast to lighter elements such as phosphorus [12,13,14,15,16]
In 2012, Ohshita et al reported the synthesis of benzothiophene-fused pentacyclic stibole IV {1-(4-methylphenyl)-2,2 -di(benzo[b]thieno)stibolein} in low yield; almost no luminescence was observed at room temperature [29]

Summary

Introduction

The development of novel π-conjugated systems and the elucidation of their optical properties to realize desired behaviors and functionalities are of current importance in the field of organic optoelectronic materials. In 2012, Ohshita et al reported the synthesis of benzothiophene-fused pentacyclic stibole IV {1-(4-methylphenyl)-2,2 -di(benzo[b]thieno)stibolein} in low yield; almost no luminescence was observed at room temperature [29]. They reported both the synthesis of pyridine-fused tricyclic stibole V (9-phenyl-stibolo [2,3c:5,4-c ]dipyridine) and its phosphorescence at low temperature. We reported the synthesis and structural study of optically active 7-(p-tolyl)dinaphtho[2,1-b:1 ,2 -d]stibole (7-Tol-DNSb) and revealed the dynamic behavior of the binaphthyl skeleton based on the C2 symmetry axis [31] These results show that the synthesis, structural analysis, and optical properties of the parent compound, stibole, are important for the subsequent creation of functional devices. We present the synthesis of 5-phenylbenzo[b]naphtho[2,3-d]stibole (2), 6-phenyldinaphtho[2,3-b:2 ,3 -d]stibole (3), and 7-phenyldinaphtho[2,1-b:1 ,2 -d]stibole (5) (Scheme 1) and explore the influence of the fused benzene rings on the optical properties including the phosphorescence of polycyclic benzostiboles

Methods

Results

Conclusion