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

• Published in: Molecules (Basel, Switzerland) Vol. 26; no. 1; p. 222
• Main Authors: Matsumura, Mio, Matsuhashi, Yuki, Kawakubo, Masato, Hyodo, Tadashi, Murata, Yuki, Kawahata, Masatoshi, Yamaguchi, Kentaro, Yasuike, Shuji
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 04.01.2021; MDPI
• Subjects: Aerobic conditions; Antimony; Antimony compounds; Arsenic; Arsenic - chemistry; Asymmetry; Benzene; Benzene - chemistry; Chloroform; Communication; Crystal structure; Crystallization; Crystallography, X-Ray; Emissions; Heavy elements; Heterocyclic Compounds - chemistry; Hydrocarbons; Hydrocarbons, Brominated - chemistry; Intermediates; low-temperature luminescence; Luminescence; Models, Molecular; Molecular Structure; NMR; NMR spectroscopy; Nuclear magnetic resonance; Optical properties; Phosphorescence; Room temperature; Single crystals; Spectroscopy; stibole; Structural analysis; molecular structure; phosphorescence; stibole; antimony; low-temperature luminescence
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules26010222

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 CHCl frozen matrix at 77 K under aerobic conditions.