H-Aggregates Granting Crystallization-Induced Emissive Behavior and Ultralong Phosphorescence from a Pure Organic Molecule

Abstract

Solid-state luminescent materials with long lifetimes are the subject of ever-growing interest from both a scientific and a technological point of view. However, when dealing with organic compounds, the achievement of highly efficient materials is limited by aggregation-caused quenching (ACQ) phenomena on one side and by ultrafast deactivation of the excited states on the other. Here, we report on a simple organic molecule, namely, cyclic triimidazole (CHN), 1, showing crystallization-induced emissive (CIE) behavior and, in particular, ultralong phosphorescence due to strong coupling in H-aggregated molecules. Our experimental data reveal that luminescence lifetimes up to 1 s, which are several orders of magnitude longer than those of conventional organic fluorophores, can be realized under ambient conditions, thus expanding the class of organic materials for phosphorescence applications.

Extrinsic Heavy Metal Atom Effect on the Solid‐State Room Temperature Phosphorescence of Cyclic Triimidazole

“…In this regard, we have recently reported on the photophysical properties of triimidazo[1,2‐ a :1′,2′‐ c :1′′,2′′‐ e ][1,3,5]triazine ( TT ), which displays crystallization‐induced (CIE) and mechanochromic emission, together with RTUP under ambient conditions due to H aggregation . In addition we investigated the possibility of modulating its phosphorescence by introducing into the molecule (intrinsic effect) a halogen atom (Br or I) or by exploiting specific intermolecular interactions (extrinsic effect) based on halogen bonding with other molecules of the same type (one component) or a different type (two‐component for example, in co‐crystals)…”

Efficient Room‐Temperature Phosphorescence of a Solid‐State Supramolecule Enhanced by Cucurbit[6]uril

“…Single crystal X-rayd iffraction results indicate that the chromophore with iodide counterion (PYI) exhibits the highest efficiency maybe due to the halogen-bond interactions.S ignificantly,t he nanosupramolecular assembly of PY chloride complexation with the cucurbit[6]uril gives agreatly enhanced phosphorescent quantum yield up to 81.2 % in ambient. [11] On the other hand, supramolecular approach have been used extensively to construct functional materials by complexing or assembly.N oncovalent interactions,s uch as host-guest interaction, [12] hydrogen bonding, [13] p-p stacking [14] can alter the properties of guests greatly.Recently,Huang and co-workers reported asupramolecular strategy to enhance the efficiency (phosphorescence quantum yield 24.3 %) and extend the lifetime of phosphorescence by constructing crystalline framework. This supramolecular assembly concept with counterions effect provides anovel approach for the improvement of RTP.…”

Persistent Solid‐State Phosphorescence and Delayed Fluorescence at Room Temperature by a Twisted Hydrocarbon

“…These data illustrate the obvious:while there is, of course,n ol inear correlation between yield and lifetime, ah igh F is much harder to achieve if phosphorescence is persistent (3)than if lifetimes are in or below the millisecond range (1, 2), where it can more easily compete with non-radiative deactivation. [16] In general, electronic transitions between non-coplanar (orthogonal or tilted) orbitals are necessary to allow for spinorbit coupling (SOC), [17,18] but the vast majority of polycyclic aromatic compounds do not present this kind of geometry. [12] Innovative approaches for the improvement of RTPv ia intermolecular interactions are crystallization-induced phosphorescence, [9] halogen bonding in co-crystals, [13] aggregation-induced ISC, [14] complexationinduced RTPi ns olution, [15] and emission from H-aggregates.…”

“…Short-lived RTPwith F near unity has been obtained with Ir and Pt complexes [11] and with abenzene bearing six arylthio substituents. [16] In general, electronic transitions between non-coplanar (orthogonal or tilted) orbitals are necessary to allow for spinorbit coupling (SOC), [17,18] but the vast majority of polycyclic aromatic compounds do not present this kind of geometry. [16] In general, electronic transitions between non-coplanar (orthogonal or tilted) orbitals are necessary to allow for spinorbit coupling (SOC), [17,18] but the vast majority of polycyclic aromatic compounds do not present this kind of geometry.…”

“…[12] Innovative approaches for the improvement of RTPv ia intermolecular interactions are crystallization-induced phosphorescence, [9] halogen bonding in co-crystals, [13] aggregation-induced ISC, [14] complexationinduced RTPi ns olution, [15] and emission from H-aggregates. [16] In general, electronic transitions between non-coplanar (orthogonal or tilted) orbitals are necessary to allow for spinorbit coupling (SOC), [17,18] but the vast majority of polycyclic aromatic compounds do not present this kind of geometry. However,ahydrocarbon whose persistent solid-state RTP was noted early is tetraphenylmethane 4.…”