A material possessing a very small energy gap between its singlet and triplet excited states, ΔE1−3, which allows efficient up-conversion of triplet excitons into a singlet state and leads to efficient thermally activated delayed fluorescence (TADF), is reported. The compound, 2-biphenyl-4,6-bis(12-phenylindolo[2,3-a] carbazole-11-yl)-1,3,5-triazine, breaks the restriction of a large energy gap, with a ΔE1−3 of just 0.11 eV, while maintaining a high fluorescent radiative decay rate (kr∼107). The intense TADF provides a pathway for highly efficient electroluminescence.

We demonstrate an organic molecule with an energy gap between its singlet and triplet excited states of almost zero (ΔE(ST) ∼ 0 eV). Such separation was realized through proper combination of an electron-donating indolocarbazole group and a diphenyltriazine electron-accepting moiety. Calculated and measured ΔE(ST) were 0.003 and 0.02 eV, respectively. A total photoluminescence efficiency of 59% ± 2% with 45% ± 2% from a delayed component and 14% ± 2% from a prompt component was obtained for a doped film. Organic light emitting diodes containing this molecule as an emitting dopant exhibited an unexpectedly high external electroluminescence efficiency of η(EQE) = 14% ± 1%.

Truly heterogeneous with retention of its high performance: The 1,3‐dipolar cycloaddition of azomethine imines to terminal alkynes was efficiently promoted by the easily prepared, inexpensive, supported copper hydroxide, Cu(OH)x/Al2O3. Various kinds of azomethine imines and terminal alkynes could be utilized as dipoles and dipolarophiles, respectively, to form the corresponding N,N‐bicyclic pyrazolidinone derivatives in high yields.

A simple dinuclear copper complex [Cu(®-OH)(tmen)] 2 Cl 2 (tmen = N,N,N¤,N¤-tetramethylethylenediamine) could act as an effective precatalyst for the 1,3-dipolar cycloaddition of pyrazolidinone-based dipoles to terminal alkynes to produce the corresponding N,N-bicyclic pyrazolidinone derivatives.

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