Blue Emitting 3 π–2 Spiro Terfluorene–Indenofluorene Isomers: A Structure–Properties Relationship Study

Abstract

Two novel terfluorenyl derivatives, 2,2'',7,7''-tetrakis(9,9-dioctyl-9H-fluoren-2-yl)dispiro[fluorene-9,11'-indeno-(2,1-a)-fluorene-12',9''-fluorene] ((2,1-a)-DST-IF) and 2,2'',7,7''-tetrakis(9,9-dioctyl-9H-fluoren-2-yl)dispiro- [fluorene-9,6'-indeno-(1,2-b)-fluorene-12',9''-fluorene] ((1,2-b)-DST-IF) have been synthesized by two different synthetic approaches. These terfluorenyl derivatives possess a different central indenofluorene core, namely (2,1-a)-indenofluorene or (1,2-b)-indenofluorene, which imposes two distinct geometry profiles, and different structural environments for the terfluorenyl fluorophores that translates into drastically different optical and electrochemical properties for (2,1-a)-DST-IF and (1,2-b)-DST-IF. These properties have been carefully studied through a combined experimental and theoretical approach. The (2,1-a)-DST-IF isomer has been successfully used as emitting layer in a blue single-layer small-molecule organic light-emitting diode (SMOLED) and appears as the first example of a blue emission arising from intramolecular terfluorenyl excimers. Regarding the importance of terfluorenyl derivatives in organic electronics, the present structure-properties relationship study, may open new avenues in the design of efficient blue fluorophores.

Spirobifluorene Regioisomerism: A Structure–Property Relationship Study

“…The regioselectivity has not been studied in detail herein but preliminary works seem to show that the temperature and the nature of the solvent have an important effect as previously reported in literature for similar aromatic electrophilic substitutions. [23,24] The substitution of the amine by an iodine atom is then performed through a Sandmeyer reaction on fluorenone b1 providing the 1-iodofluorenone c1 with 75% yield. We note that compound c1 reported herein widens the scope of substituted fluorenone isomers as key building blocks for the synthesis of spiro derivatives for organics electronics.…”

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

“…Indeed, this feature appears hence to be a unique characteristic of 4-substituted-SBF derivatives as 2-substituted-SBF analogues always present well resolved emission bands assigned to the double bond character of the C-C bond linking the pendant substituent and the fluorenyl core in the excited state. 8,9,83,92,93 Thus, 2,2'-(SBF) 3 and 2,2'-(SBF) 2 exclusively built on para linkages present a well resolved emission spectrum, drastically different to those of their 4-substituted analogues, namely 4,4'-(SBF) 2 and 4,4'-(SBF) 3 . The same conclusion can be drawn for 2-Ph-SBF and 4-Ph-SBF.…”

“…6,7 From a more fundamental point of view, the orthogonal configuration induced by the spiro carbon also allows to design shape persistent molecules with specific arrangements, which in turn has peculiar electronic consequences. 3,4,[8][9][10][11][12][13][14][15] In addition, the application field of the SBF scaffold is not only restricted to electronics and SBF has also found many other appealing applications as chiral ligand, [16][17][18][19] electropolymerizable building block, [20][21][22][23][24][25][26] homogeneous 27 and heterogeneous 23-25, 28, 29 catalysts or as building unit in coordination polymers, [30][31][32] clearly showing the versatility of this fragment. Sixteen positions of substitutions are available on the SBF backbone, eight on each fluorene unit (figure 1).…”

Electrochemistry and electrogenerated chemiluminescence of thiophene and fluorene oligomers. Benzoyl peroxide as a coreactant for oligomerization of thiophene dimers

“…[32][33][34][35][36][37] Studies of electrochemical behavior of oligomers of phenylvinylenes, boron dipyrromethene (BODIPY) dyes, thiophenes, fluorenes, and spirofluorenes show the presence of more than one wave for both oxidation and reduction. 10,11,15,16,19,38,39 However, the separations between waves for successive electron transfers have not been delineated very clearly; neither have the differences between oxidation and reduction processes. In this work we attempt to establish guidelines for the separation between electrochemical waves for a range of thiophene and fluorene oligomer lengths.…”