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Three novel heterocyclic host based on diaryl ketone‐tethered 1,5‐diazocines were designed and synthesized for applications in phosphorescent organic light‐emitting diodes (PhOLEDs). The hosts were derived by anchoring the naphthyl ketone (TBN), anthryl ketone (TBA), and phenanthryl ketone (TBP) to the 1,5‐diazocine core. The materials were successfully characterized using spectroscopic techniques. TBN and TBP exhibited low external quantum efficiency of 1.5% and 1.9% when explored as hosts in PhOLED devices. Among the series, TBP exhibited the highest luminance of 4160 cd/m2, maximum luminance efficiency of 6.3 cd/A, and power efficiency of 3.21 lm/w, when doped with Ir(ppy)3 in PhOLED. Nevertheless to our surprise, TBA manifested the lowest device performance than other TBs as a host due to low carrier mobility caused by a highly twisted structure as deciphered from the comparative analysis of single‐crystal structure that could impede carrier transport crucial for efficient electroluminescence. The outcomes of electroluminescence were validated and explained with analysis of single‐crystal structure, and also with the aid of density functional theory. [ABSTRACT FROM AUTHOR]

Phenyl/arylethynylation of 2,2-diphenylbenzopyrans (i.e., chromenes) permits modulation of the spectral properties of photogenerated colored o-quinonoid intermediates, and brings about remarkable stabilization of the latter, rendering the phenomenon of photochromism observable readily at room temperature. Modification of the spectrokinetic properties of the o-quinonoid intermediates are a consequence of resonance effects, with the substituent effects being relayed nicely from one end of the molecule to the other. Functionalization at the 6-position of the chromene nucleus leads to more redshifted absorptions as well as to increased lifetimes of the colored species when compared with functionalization at the 7- position. Given that photochromism is observable in the parent chromene at only low temperatures, phenyl/arylethynylation, which precludes steric inhibition of resonance, is demonstrated to render bleaching kinetics of the colored intermediates that approach those reported for industrially relevant diarylnaphthopyrans. [ABSTRACT FROM AUTHOR]

Phenyl/arylethynylation of 2,2-diphenylbenzopyrans (i.e., chromenes) permits modulation of the spectral properties of photogenerated colored o-quinonoid intermediates, and brings about remarkable stabilization of the latter, rendering the phenomenon of photochromism observable readily at room temperature. Modification of the spectrokinetic properties of the o-quinonoid intermediates are a consequence of resonance effects, with the substituent effects being relayed nicely from one end of the molecule to the other. Functionalization at the 6-position of the chromene nucleus leads to more redshifted absorptions as well as to increased lifetimes of the colored species when compared with functionalization at the 7-position. Given that photochromism is observable in the parent chromene at only low temperatures, phenyl/arylethynylation, which precludes steric inhibition of resonance, is demonstrated to render bleaching kinetics of the colored intermediates that approach those reported for industrially relevant diarylnaphthopyrans. [ABSTRACT FROM AUTHOR]

A water-stable In-MOF, constructed based on a conformationally-flexible tetraacid linker, i.e., 2,7-bis(3,5-dicarboxyphenyl)-9,9'-diphenyl-9H-fluorene, i.e., H4DPF, is shown to exhibit a significantly enhanced solid-state fluorescence quantum yield (φf) of 23% in comparison with that of the linker (φfca. 4%) as a consequence of rigidification of the latter by metalation. Application of external stimulus in the form of grinding of the In-MOF leads to a drastic enhancement by 29%, φf from 23 to 52%. Solid-state absorption and emission spectra show that the absorption in the region of 368-550 nm gets diminished with a concomitant change in the emission maximum with a blue shift upon grinding. Fluorescence enhancement with grinding is correlated with a gradual reduction in the size of the particles, as established by SEM analysis. MOF particle aggregation has been invoked to account for the observed fluorescence enhancement in addition to a subtle conformational change in the structure of the linker upon grinding. Intriguingly, the ground MOF particles exhibit aggregation behaviour in the DMF-water solvent system with the emission further increasing up to 75% for the increase in the water fraction (fw) from 0 to 60%; hydrophobic aggregation of particles evidently leads to a change in the conformation of the linker and particle aggregation-enhanced emission (AEE). De-aggregation of particles ensues for fw = 70-90%, as reflected by a gradual decrease in the emission intensity. It is shown that the suspension of ground In-MOF particles in water permits sensing of metal ions, in particular Al3+ ions, by fluorescence quenching with detection at a sub-ppb level. The observed results comprise first demonstration of both mechanoluminescence and AEE of MOF particles.