Synthesis, characterization and photophysical study of ethynyl pyrene derivatives as promising materials for organic optoelectronics

• Published in: Journal of luminescence Vol. 161; pp. 37 - 46
• Main Authors: Gama, Paola E., Corrêa, Rodrigo J., Garden, Simon J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2015
• Subjects: Ethynylpyrene derivatives; Red-shift; Solid state fluorescence; Solution fluorescence; TDDFT; Ethynylpyrene derivatives; Solution fluorescence; TDDFT; Red-shift; Solid state fluorescence
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2014.12.036

Two series of pyrene derivatives, phenylethynyl (4–6) and the previously unknown ethynylcyclohexanol (7–9), were prepared by Sonogashira cross-coupling reactions. The introduction of an increasing number of ethynyl substituents resulted in a progressive bathochromic shift in the absorption and emission spectra which culminated in an inversion of the nature of the first two excited states (1La and 1Lb) of the tetra-substituted derivatives (6 and 9) relative to pyrene. In solution, only for the mono-cyclohexanolethynyl pyrene (7) a sufficiently concentrated solution could be obtained so as to observe the excimer. Additionally, the emission band ratio I1/I3 for 7 was found to be moderately sensitive to the nature of the solvent and the ratio directly correlated with the Py scale. TDDFT calculations were used to explore the variation of the properties of the low lying excited states. Fluorescence emission in the solid state, with the appropriate choice of materials, covers the entire visible region of the electromagnetic spectrum due to static excimer emission. A massive red-shift for solid state photoluminescence from 9 resulted in emission at longer wavelength than the more highly conjugated 6. •Phenyl and cyclohexanol ethynylpyrene derivatives: photophysically compared.•Excimer formation and solvent dependent emission from cyclohexanolethynylpyrene.•Systematic red shifting of solid state photoluminescence from static excimers.•Massive red-shift in the solid state photoluminescence of 9.•TDDFT calculations: properties of the lowest singlet states, systematic comparison.