Effects of substituents in silyl groups on the absorption, fluorescence and structural properties of 1,3,6,8-tetrasilylpyrenes

• Published in: Photochemical & photobiological sciences Vol. 17; no. 6; pp. 781 - 792
• Main Authors: Maeda, Hajime, Suzuki, Tsubasa, Segi, Masahito
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2018; Springer Nature; Royal Society of Chemistry
• Subjects: Absorption; Biochemistry; Biochemistry & Molecular Biology; Biomaterials; Biophysics; Chemistry; Chemistry, Physical; Cyclohexane; Derivatives; Dichloromethane; Emissions; Excimers; Fluorescence; Life Sciences & Biomedicine; Mathematical analysis; NMR; Nuclear magnetic resonance; Organic chemistry; Physical Chemistry; Physical Sciences; Plant Sciences; Pyrene; Rotation; Science & Technology; Silicon; Wavelengths; ELECTRONIC-PROPERTIES; TIME-RESOLVED FLUORESCENCE; THROUGH-SPACE; PYRENE; QUANTUM YIELDS; PI-PI; STATE; INTRAMOLECULAR EXCIMER; CHARGE-TRANSFER; AROMATIC-COMPOUNDS
• ISSN: 1474-905X; 1474-9092
• DOI: 10.1039/c8pp00135a

1,3,6,8-Tetrasilylpyrenes and related germyl and stannyl derivatives were synthesized, and their absorption and fluorescence spectroscopic and structural properties were elucidated. The results show that the UV-vis absorption maxima of these substances in CH 2 Cl 2 solutions shift to longer wavelengths as the size of the alkyl groups and numbers of phenyl groups on silicon increase. Fluorescence quantum yields of tetrasilylpyrenes in cyclohexane are larger than that of pyrene, and a pentamethyldisilyl derivative has an emission efficiency of 0.79. Except in the case of the SiMe 2 H derivative, excimer emission was not observed in concentrated solutions of these substances. The SiMe 2 H and SiMe 3 derivatives were shown to form CT complexes with tetracyanoethylene in CH 2 Cl 2 solutions. The calculated energy barriers for rotation of the silyl groups about the Si-C bond increase as the steric bulk of the silyl group increases. 29 Si NMR chemical shifts were found to depend on the sizes of the alkyl groups and numbers of phenyl groups. Data arising from theoretical calculations suggest that the silyl groups act as electron-donating groups, and the donating ability of the groups decreases in the order SiR 3 > GeR 3 > SnR 3 . In this effort, we prepared and characterized photophysical properties of 1,3,6,8-tetrasilylpyrenes, focussing on the effects of substituents on silicon atoms.