Six new binary charge-transfer (CT) cocrystals have been synthesized by solvent drop-assisted mechanochemical grinding method, and all of them exhibited remarkable color changes during the grinding process. Crystal structure analysis reveals the donor (D) and acceptor (A) molecules have assembled primarily via cofacial π•••π stacking interactions displaying mixed D−A−D−A stacked columns. Interestingly these cocrystals exhibited very diverse dielectric response in the presence of an alternating current (ac) external electric field, and their dielectric behavior can be explained from the nature and strength of CT interactions in the cocrystal assembly. Strong CT cocrystals were found to display a rigid supramolecular framework while weakly bound CT complexes allowed its constituent polar molecules to relax and hence the observed rotational dynamics contributed to their dielectric properties. Chemical shift anisotropy parameters, spin−lattice relaxation, and molecular correlation times obtained from 13 C solid-state NMR spectroscopy measurements establish the occurrence of molecular dynamics at the atomistic scale in cocrystals, thereby displaying high permittivity. Furthermore, we also propose a strategy directed toward the design of CT cocrystals that allows us to introduce rotational dynamics in noncentrosymmetric molecules, which significantly enhances their dielectric properties due to orientation polarization. The results indicate that D−A-based organic CT systems, particularly with a mixed stack, have a wide range of potential applications in materials science.

Five new binary co-crystals have been prepared through molecular self-assembly of π-electron-rich molecules, such as phenanthrene, benzo[c]cinnoline, and phenazine, in the presence of π-electron-deficient molecules, such as tetrafluoro-1,4-benzoquinone, tetrachloro-1,4-benzoquinone, and 1,2,4,5-tetracyanobenzene, taken in an equimolar ratio. Crystal structure analysis revealed that in three binary co-crystals the constituent molecules were alternately sandwiched in a cofacial arrangement through π•••π interactions, whereas in the remaining two binary co-crystals the constituent molecules were aligned in a unique edge-to-face manner through lp•••π interactions. Co-crystals with π-stacking arrangement were fluorescent, whereas almost complete quenching of luminescence was observed in those having edge-to-face alignment of molecules. The photophysical observations of these co-crystals have been demonstrated via energetic quantification of the intermolecular interaction topology, which provides a molecular level understanding of factors controlling their solid-state absorption and luminescence behavior.

An unusually large exciton coupling and spontaneous self-localization safeguards the long-lived excitons of H-aggregated perylene bisimide against a notoriously universal excimeric trapping process, and rekindles its potential as a light-harvesting material.

σ- and π-hole directed intermolecular interaction driven tuning of luminescence.

Long-term visualization of the lysosomal properties is extremely crucial to evaluate their dysfunction-related diseases. However, many of the reported lysotrackers are less conducive to image lysosomes precisely because they suffer...

Atom precise metal nanoclusters with customized surface structures are important for understanding the mechanism of surface engineering for appropriate applications. We are reporting a single copper doping on a very widely studied Au 11 (PPh 3 ) 7 Cl 3 nanocluster, in which one chloride ligand is replaced by one Cu atom. Accordingly, a new bimetal nanocluster Cu 1 Au 11 (PPh 3 ) 7 Cl 2 is produced, which consisted of a unique Au− Cu surface motif where the Cu is only bonded with an Au atom. In such a motif, the unsaturated Cu atom acts as an active catalyst for the Sonogashira reaction in contrast to the catalytically inactive Au 11 nanocluster. Moreover, it demonstrated a reversed selectivity in the Sonogashira cross-coupling reaction, where the major product obtained was homocoupled Glaser products in contrast to the selectivity of previously reported cluster/bimetallic clusters toward Ullmann or Sonogashira products. Theoretical calculations support the unsaturated Cu to be the active site on the nanocluster (NC) and act like a single-atom catalyst. This highlights the effect of mono copper atom doping on the unique selectivity in the Sonogashira cross-coupling reaction.

Tetrahydrate berberine chloride crystals undergo cracking, bending and jumping on cooling as well as on heating at room temperature with a rapid conversion to a dihydrate phase.

The structure–property correlation of a series of silver nanoclusters (NCs) is essential to understand the origin of photophysical properties. Here, we report a series of face-centered cubic (fcc)-based silver NCs by varying the halogen atom in the thiolate ligand to investigate the influence of the halide atoms on the electronic structure. These are {Ag14(FBT)12(PPh3)8·(solvent) x } (NC-1), Ag14(CBT)12(PPh3)8 (NC-2), and Ag14(BBT)12(PPh3)8 (NC-3), where 4-fluorothiophenol (FBT), 4-chlorothiophenol (CBT), and 4-bromothiophenol (BBT) have been utilized as thiolate ligands, respectively. Interestingly, the optical and electrochemical bandgap values of these NCs nicely correlated with the electronic effect of the halides, which is governed by the intracluster and interclusters π–π interactions. These clusters are emissive at room temperature and the luminescence intensity increases with the lowering of temperature. The short lifetime data suggest that the emission is predominantly originating due to the interband relaxation (d → sp) of the Ag cores. Femtosecond transient absorption (TA) spectra revealed similar types of decay profiles for NC-2 and NC-3 and longer decay time for NC-2. The relaxation dominates the decay profile to the surface states and most of the excited-state energy dissipates via this process. This supports the molecular-like dynamics of these series of NCs with an fcc core. This overview shed light on an in-depth understanding of ligand’s role in luminescence and transient absorption spectra.