A nine-ring fused terrylene diimide exhibits switching between red TADF and near-IR room temperature phosphorescence.

Herein, we report the first example of a terrylene diimide derivative that switches emission between thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) in the red region. By design, the molecule TDI-cDBT boasts a symmetrical, consecutively fused nine-ring motif with a kite-like structure. The rigid core formed by the annulated dibenzothiophene moiety favoured efficient intersystem crossing and yielded a narrow-band emission with a full-width half maxima (FWHM) of 0.09 eV, along with high colour purity. A small ΔE S1-T1 of 0.04 eV facilitated thermally activated delayed fluorescence, enhancing the quantum yield to 88% in the red region. Additionally, it also prefers a direct triplet emission from the aggregated state. The room temperature phosphorescence observed from the aggregates has a longer emission lifetime of 1.8 ms, which is further prolonged to 8 ms at 77 K in the NIR region. Thus, the current strategy is successful in not only reducing ΔE S1-T1 to favour TADF but also serves as a novel platform that can switch emission from TADF to RTP depending upon the concentration.

A Bis-Porphyrin Cavitand Breathing-In to Constrict Bucky Balls.

Bis-porphyrin cages have long been exploited to bind fullerenes selectively for various applications. The major consideration for an effective binding here had been the cavity size. Herein, we structurally demonstrate that a bis-Ni-porphyrin cavitand having even a smaller cavity can host a larger fullerene by a breathing and ruffling mechanism. It has also been shown that both the electronic and steric influence at the meso- positions of the porphyrin in fact dictate the binding character. The smaller cavity of 2NiD exhibits preferential binding for C70 over C60; however, surprisingly, the larger cavities in 2HD and 2NiTD display stronger affinities for C60 over the larger fullerene. We show here that the structural elasticity infused both by the metalloporphyrins and the connecting bridges play a major role in directing the binding. These conclusions have adequately been supported by structural and spectroscopic investigations. Additionally, the suitability of one of the conjugates for photoinduced charge-separation has been investigated using ultrafast transient absorption measurements. 2NiD⊃C60 has a charge separation timescale of ~0.8 ps, while charge recombination occurs at a longer timescale of ~920 ps.

Aminophenyl-substituted cobalt(iii) corrole: a bifunctional electrocatalyst for the oxygen and hydrogen evolution reactions.

Catalytic water splitting is a highly promising area of research for the development of a hydrogen-based society. Herein, the synthesis of the bifunctional A2B-type cobalt(iii) corrole Co(BAPC)Py2 having the electron-withdrawing meso-pentafluorophenyl and the basic meso-p-aminophenyl substituents is reported. Cyclic voltammetric studies reveal that Co(BAPC)Py2 has two oxidation waves at 0.97 V and 1.42 V associated with the Co(iii) → Co(iv) and Co(iv) → Co(v) redox couples, respectively, and two reduction waves at 0.45 and -0.21 V corresponding to the Co(iii) → Co(ii) and Co(ii) → Co(i) redox couples. The as-synthesized Co(BAPC)Py2 corrole has been demonstrated to be an efficient catalyst for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in homogeneous (acetonitrile) as well as heterogeneous media. In a homogeneous solution, Co(BAPC)Py2 showed excellent activity towards both the HER, with the first-order rate constant (kcat) of 952.0 s-1, and the OER with the first-order rate constant of 0.2 s-1. The strong electron -withdrawing pentafluorophenyl group present on the corrole ring shifts the redox process towards the anodic direction and facilitates the HER performance, whereas the aminophenyl group increases the basicity of the catalyst that improves the OER activity.