The present study of structure-property relationships and disclosure of fascinating amplified spontaneous emission (ASE) behavior of an organic molecule not only exhibits the individual effect of molecular conformation and arrangement on the emission properties of the crystal separately, but also indicates that some concealed elegant properties of organic solids can be achieved through manipulating the polymorphic form.

No abstract

Developing pure organic materials with ultralong lifetimes is attractive but challenging. Here we report a concise chemical approach to regulate the electronic configuration for phosphorescence enhancement. After the introduction of d–pπ bonds into a phenothiazine model system, a phosphorescence lifetime enhancement of up to 19 times was observed for DOPPMO, compared to the reference PPMO. A record phosphorescence lifetime of up to 876 ms was obtained in phosphorescent phenothiazine. Theoretical calculations and single‐crystal analysis reveal that the d–pπ bond not only reduces the (n, π*) proportion of the T1 state, but also endows the rigid molecular environment with multiple intermolecular interactions, thus enabling long‐lived phosphorescence. This finding makes a valuable contribution to the prolongation of phosphorescence lifetimes and the extension of the scope of phosphorescent materials.

The design and construction of coordination polymers from preformed metal clusters, [1] such as metal carboxylate clusters [2] and chalcogenide supertetrahedral clusters, [3] to produce new materials with unique properties have been the focus of recent research interest. However, given the importance of cuprous iodide clusters in photochemistry and photophysics, [4] as well as their considerable variety of structural forms not encountered for other iodometalates, [5] it is surprising that relatively little progress has been made in using them as building blocks for the fabrication of multidimensional coordination frameworks.[6] On the other hand, polyoxometalates (POMs), [7,8] as a unique class of metaloxide clusters, have many properties that make them attractive for applications in catalysis, biology, magnetism, optics, and medicine.[9] Impressive studies on linking of these welldefined metal-oxygen building blocks to generate giant discrete clusters and related extended structures have been performed. [10,11] However, up to now no reports have been made on the combination of these two interesting fields to prepare high-dimensional cluster-based compounds, although POM chemistry has touched an almost unprecedented number of other fields of chemistry.[9b] Such composite materials present the opportunity to generate high-dimensional nanoscopic assemblies from even larger multinanounits and also have vast potential for use in materials science by incorporation of their own physical and chemical properties.Among the many different types of POMs, we chose the Keggin heteropolyanions, as they are the most widely recognized and thoroughly studied. Furthermore, we used the N-heterocyclic ligand 4-[3-(1H-1,2,4-triazol-1-yl)propyl]-4H-1,2,4-triazole (L, see the Supporting Information) for our synthetic strategy because 1) its clawlike donor atoms and bent coordination geometry offer the possibility of incorporating more metal atoms into high-nuclearity clusters, and 2) ligands containing a large number of N atoms could partially reduce Mo VI to Mo V , [12] whereby the surface charge density of the polyanion is increased and the surface oxygen atoms are activated to facilitate formation of high-dimensional covalent networks. Herein we report the synthesis, structure, and luminescent and electrochemical properties of an unprecedented (4,12)-connected 3D network, namely, (NH 4