Glass-Forming Binaphthyl Chromophores

Abstract

The use of the binaphthyl framework to synthesize glass-forming organic chromophores is described. Suzuki coupling reactions of racemic 6,6'-dibromo-2,2'-dialkoxy-1,1'-binaphthyl with 1,1-diphenyl-2-(4-dihydroxyboronphenyl)-ethene using [Pd(dppf)Cl2] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) as the catalyst provide a set of chromophores with the 4-(2,2'-diphenylvinyl)-1-phenyl group at the 6- and 6'-positions and a range of groups on the oxygen atom. Starting with enantiomerically enriched (R)-6,6'-dibromo-2,2'-dihexyloxy-1,1'-binaphthyl ((R)-2Hex), one can obtain (R)-3Hex. Heck coupling reactions of 6,6'-dibromo-2,2'-dialkoxy-1,1'-binaphthyl compounds with styrene provide chromophores of the type 2,2'-dialkoxy-1,1'-binaphthyl-6,6'-bis(2-phenyl-vinyl). Starting with enantiomerically enriched (R)-2Hex, one obtains (R)-4Hex. Molecules of the type 4 contain two 1-naphthyl-2-phenyl ethylene chromophores with a pseudoorthogonal relationship. Similar procedures can be used to obtain fragments with more extended conjugation length. Thus, the Heck coupling reaction of 2Hex with 4-(4'-tert-butylstyryl)styrene, 1-(4'-tert-butylstyryl)-4-(4'-vinylstyryl)benzene, and 1-(3',5'-dihexyloxystyryl)4-(4'-vinylstyryl)benzene provides 5Hex, 6Hex, and 7Hex, respectively. DSC measurements and powder diffraction experiments indicate that the binaphthol chromophores show a resistance to crystallization. In some cases, considerably different thermal behavior is observed between enantiomerically enriched samples and their racemic counterparts. Increasing the size of the conjugated fragment on the binaphthol core leads to materials with higher glass-transition temperatures and a less pronounced tendency to crystallize. Fluorescence spectroscopy gives evidence of "excimer"-type interactions in the solid state, except for the chromophores with 4-(2,2'-diphenylvinyl)-1-phenyl groups. It is possible to obtain amorphous films of these chromophores directly from solution, and to fabricate light-emitting diodes, in which the electroluminescent layer corresponds to the binaphthyl chromophore.

Binaphthyl‐Containing Green‐ and Red‐Emitting Molecules for Solution‐Processable Organic Light‐Emitting Diodes

“…[9,10] The non-planar binaphthyl unit, with its large dihedral angle and its twisted conformation, has proved to be a suitable moiety that yields a stable amorphous phase and results in good solubility. To date, binaphthyl-containing polymers, [11][12][13][14] dendrimers, [15,16] and small organic molecules [17][18][19] have already been widely used in chiral sensors, [20][21][22][23] unsymmetrical catalysis, [24][25][26][27] photochromic application, [28][29][30] and nonlinear optical materials; [31,32] but in recent years binaphthyl-containing materials have also been successfully employed as blue-emitter in electroluminescent (EL) devices. [11][12][13][14]17,18,[33][34][35][36][37][38][39][40] Yet, greenand red-emitting materials based on binaphthyl-containing molecules (BNCMs) are rarely reported so far.…”

Anthracene‐Containing Binaphthol Chromophores for Light‐Emitting Diode (LED) Fabrication

“…Previous work in our laboratories [10] demonstrated that the binaphthol core is a suitable platform for the design of chromophores that yield stable amorphous phases. The glass forming ability arises from the pseudo-orthogonal relationship between the two-naphthyl fragments.…”

Red Electrophosphorescence from a Soluble Binaphthol Derivative as Host and Iridium Complex as Guest

“…11,12 A hexyl chain was introduced at the 2 and 2′ positions to ensure good solubility. The carbazole unit was introduced at the 6 and 6′ positions using the Buchwald-Hartwig cross coupling.…”