Luminescent and Axially Chiral π-Conjugated Polymers Linked by Carboranes in the Main Chain

Abstract

Sonogashira-Hagihara polycondensations of two bis(4-iodophenyl)carborane compounds with axially chiral diyne monomers having binaphthyl unit were carried out to obtain the corresponding chiral π-conjugated polymers having o-or m-carborane segment in the main chain. The polymer structures and their optical properties were characterized by 1 H, 13 C, and 11 B NMR, FT-IR, UV-vis absorption, photoluminescence, and circular dichroism spectroscopies. Photoluminescence study revealed that the polymer having m-carborane exhibited intense blue emission in solution state, whereas polymers having o-carborane exhibited aggregation-induced emission (AIE). All polymers showed strong CD signals, indicating the construction of highly ordered conformation.

C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry

“…3 These carboranes have only recently been considered as potential components for OLEDs in photophysical studies on C,C-diarylated dicarbadodecaboranes. [4][5][6][7][8][9][10][11][12][13] Selected photophysical data for some C,C-diarylcarboranes are summarized in Chart 1.…”

Substituent Effects on the Fluorescence Properties of ortho‐Carbor­anes: Unusual Emission Behaviour in C‐(2′‐Pyridyl)‐ortho‐carboranes

“…[4][5][6][7][8][9][10][11][12][13] The meta-or para-carborane cluster merely plays roles as a spectator, a spacer or an inductively electron-withdrawing group in these molecules or polymers. There are, however, rare exceptions where the clusters are actively involved in the excited states of bis(benzodiazaborolyl)-meta-and -para-carboranes.…”

“…Photoexcitation of such dyads induced a charge transfer from an organic scaffold to the carborane cluster, which either led to luminescence quenching or to charge-transfer (CT) emissions or both -depending on the solvents used and whether the materials were investigated as solids. [7][8][9][10][11][12][13][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Dual fluorescence with CT and local transitions has been observed in some orthocarboranes. [12,13,[15][16][17][18][19][20]28] The ortho-carborane unit plays a role similar to meta-and para-carborane clusters in the photophysical process of a compound if there is a stronger electron acceptor than the cluster in these systems, [5,6,29,30] and if the ortho-carborane group is connected to a donor at one or more boron cluster atoms.…”

“…[33] Also other highly luminescent metal complexes have been reported with the pyridylcarborane unit present. [46] Given that there have been many articles on the observed luminescence of 1-monoalkyl-, 1-monoaryl-and 1,2-diaryl-ortho-carborane derivatives, [7][8][9][10][11][12][13][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] by contrast 1-monomethyl-ortho-carborane 4, 1-monophenyl-ortho-carborane 7 and 1,2-diphenyl-ortho-carborane 16 were quoted to be non-emissive. [20,30] …”

Polymer reaction of poly(p-phenylene–ethynylene) by addition of decaborane: modulation of luminescence and heat resistance

“…[18][19][20][21][22][23][24] Recently, we reported the synthesis of novel p-conjugated polymers with an icosahedral carborane cluster in their main chain, their great thermal durability and surprising optical properties, that is, aggregation-induced emission based on the molecular orbital of o-carborane. [25][26][27][28][29][30][31][32] Although the hybridization of p-conjugated polymers with inorganic clusters has given prominent results, the multistep synthesis of monomers containing inorganic clusters would have obstructed a thorough investigation in this field. One methodology to lessen the burden on synthesis is the polymer reaction of p-conjugated polymers.…”