A Combined Experimental and Theoretical Study on the Isomers of 2,3,4,5‐Tetracarba‐nido‐Hexaborane(6) Derivatives and Their Photophysical Properties

Abstract

Building upon our ongoing studies on the high-yield synthetic route to 2,3,4,5-tetracarba-1,6-nido hexaborane derivative 5, we continue to explore the chemistry of this system to isolate a range of perphenylated C4 B2 -type carborane isomers. As a result, the photolysis of 5 for an elongated period yielded 6, which exhibits an intense luminescence upon excitation with a UV lamp (λex =366 nm). In contrast, the conversion of 5 under thermal conditions (microwave heating) generated the isomer 7, which does not show any luminescence. The structural disparity among the three isomers 5-7 is the position of the butadiene moiety with respect to the C4 B2 -carborane cage as deduced from single-crystal X-ray diffraction analyses. In an attempt to generate the classical structural motif of 5, an equimolar amount of KOtBu was added to a THF solution of 5, which immediately provided the boratacyclopentadiene derivative 8 in good yield. The observed rearrangement reactions were further investigated by quantum chemical calculations to suggest a plausible reaction pathway. According to the DFT calculations, the energetically favored reaction mechanism most likely involves tricyclic transition states and classical intermediate structures. In addition, the fluorescence emission properties of 6 were investigated in solution as well as in the solid state.

Luminescent Mono‐, Di‐, and Triradicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes

“…Furthermore,f or compoundsw ith carbazole as the donor efficient OLEDs could be fabricated. [3] The topology of the triphenylmethyl radical and the triphenlyamine donora lso allowed the synthesis of linear oligomers, [4] polymers [5] and branched chromophores [6] that show charge transfer upon opticale xcitation. However,w hile radicals are usefulb uilding blocksf or functionalm aterials, [7] almostn othing is known about the luminescent properties of such di-and polyradicals.…”

Ein neutraler “Aluminocen”‐Sandwich‐Komplex: η1‐ vs. η5‐Koordination eines Pentaarylborols mit ECp* (E=Al, Ga; Cp*=C5Me5)

“…Die Daten erlauben dennoch die eindeutige Identifizierung des Schlüsselstrukturmotivs, welches der antizipierte η 5 ‐Cp*,η 5 ‐[(Ph*C) 4 BXyl F ]‐Al III ‐Sandwichkomplex 1 darstellt. Dies ist die erste Darstellung eines neutralen “Aluminocens” und der zweite Borolkomplex eines p‐Block‐Elements . Heteroleptische Cp/Borol‐Sandwichkomplexe sind für Übergangsmetallkomplexe bekannt …”

“…Dies ist die erste Darstellung eines neutralen "Aluminocens" und der zweite Borolkomplex eines p-Block-Elements. [10,18] Heteroleptische Cp/Borol-Sandwichkomplexe sind für Übergangsmetallkomplexe bekannt. [8e,19] Die Qualitätd er Rçntgendaten begrenzt ausgedehnte Erçrterungen der Struktur, jedoch kçnnen einige Schlüsseleigenschaften klar erkannt werden.…”

A crystalline bisindolylmaleimide with strong solid-state fluorescence of red color and its analogous cross-linked polymer without fluorescence

“…Organic fluorescent materials with strong emission in solid state are crucial in both fundamental research [1][2][3][4] and industry applications. [5][6][7][8][9] Although a number of organic molecules with strong emission in diluted solution have been reported, most of them become weekly luminescent or non-luminescent in the solid state.…”