Dispirofluorene–Indenofluorene Derivatives as New Building Blocks for Blue Organic Electroluminescent Devices and Electroactive Polymers

Abstract

A series of new dispiro[fluorene-9',6,9'',12-indeno[1,2b]fluorenes] (DSF-IFs) has been synthesised. These new building blocks for blue-light-emitting devices and electroactive polymers combine indenofluorene (IF) and spirobifluorene (SBF) properties. We report here our synthetic investigations towards these new structures and their thermal, structural, photophysical and electrochemical properties. These properties have been compared to those of IF and SBF. We also report the anodic oxidation of DSF-IFs that leads to the formation of non-soluble transparent three-dimensional polymers. The structural and electrochemical behaviour of these polymers has been studied. The first application of these building blocks as new blue-light-emitting materials in organic light-emitting diodes (OLED) is also reported.

Structure–property relationship of 4-substituted-spirobifluorenes as hosts for phosphorescent organic light emitting diodes: an overview

“…DSF[2,1-c]IF 3 with its fused structure will be also used herein for comparison purpose. The UV-Vis absorption spectrum of 4-Ph-SBF (in cyclohexane) exhibits at low energy two thin absorption bands at 296 and 308 nm, similar to those observed for SBF (figure 12, left) 81,91 and for the other 4-substituted oligo-SBFs such as 4,4'-(SBF) 2 , 4,4'-(SBF) 3 , 4,4'-(SBF) 4 or 4,4'-(SBF) 5 . 69,70 However, for 4-Ph-SBF, the band at 308 nm clearly presents a longer wavelength tail leading to an optical energy gap (∆E opt ) of 3.82 eV, more contracted by 0.15 eV than that of SBF (3.97 eV).…”

“…116 The band at 308 nm, previously observed for other SBF based compounds, corresponds to π-π* transitions involving the fluorene. 91 The authors do not provide any explanation regarding the nature of the second absorption band red shifted by 6 nm from 2-POPh 2 -SBF (316 nm) to 4-POPh 2 -SBF (322 nm). The substitution in position 4 in 4-POPh 2 -SBF and in position 2 in 2-POPh 2 -SBF provides (i) very similar HOMO energy levels (-6.57 vs -6.55 eV resp.)…”

“…Despite very similar properties in the fundamental state, 4-Ph-SBF and SBF display remarkable but surprising differences in their excited states (figure 12, middle). 81 Indeed, 4-Ph-SBF exhibits a structureless emission spectrum (λ max =358 nm), noticeably different in shape and wavelength compared to that of SBF, 81,91 which presents a well-resolved spectrum (λ max =310/323 nm) mirror image of its absorption spectrum. This large and unresolved band is found for all the dyes exclusively built on the 4-substituted SBF scaffold such as 4,4'-(SBF) 2 (λ max =373 nm), 4,4'-(SBF) 3 , 4,4'-(SBF) 4 , 4,4'-(SBF) 5 (λ max =374 nm), 69 and 4,3'-(SBF) 2 (λ max =370 nm).…”

“…First, the E T of SBF has been reported at 2.87 eV being slightly lower than that of its building block fluorene (E T =2.92 eV). 81 The slight conjugation between the two fluorene units in SBF (called spiroconjugation) 91,[98][99][100][101][102] decreases the E T of SBF by ca 0.05 eV compare to fluorene. 81,91 All the PHC derivatives exclusively built on ortho linkages possess a similar E T , measured at 2.77 eV for 4-Ph-SBF and close to 2.80 eV for the oligo-SBFs, 4,4'-(SBF) 2 , 4,4'-(SBF) 3 , 4,4'-(SBF) 4 or 4,4'-(SBF) 5 .…”

Synthesis and Optical Study of a New Oligophenylene

“…In this frame, one significant design approach towards low band gap polymers is to introduce rigid and planar units, such as molecules with fused ring structures, into the polymer backbones [16,17]. Generally, these fused components are structurally planar and lead to a substantive extension of conjugation in the polymers [18,19].…”