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5,11,17,23‐Tetra‐tert‐butyl‐25,27‐dihydroxy‐26,28‐bis(tetrazole‐5‐ylmethoxy)calix[4]arene has been reported to form remarkable Ln19 and Ln12 elongated clusters, upon addition of aqueous ammonium carboxylates. The impact of the para substituent on lanthanoid cluster formation has been studied by synthesising two new bis‐tetrazole calixarenes, with p‐H, and p‐allyl substituents. Solution phase dynamic light scattering measurements of the reaction mixtures indicated that clusters are not formed with the p‐H and p‐allyl derivatives, in contrast with the behaviour of the tert‐butyl analogue. Lanthanoid complexes of the p‐H and p‐allyl calixarenes were characterised by single‐crystal X‐ray diffraction, and were found to form mononuclear complexes, linked to form a one‐dimensional coordination polymer for the p‐allyl system. All of the complexes were isolated as ammonium salts, with ammonium cation included in the calixarene cavity in most cases. It is concluded that the nature of the para substituent has a profound impact on the lanthanoid cluster formation process, and derivatives with more subtle structural changes will be required to determine if additional lanthanoid "bottlebrush" clusters can be isolated. [ABSTRACT FROM AUTHOR]

Unconventionally modified dibenzoylmethane (dbm) ligands have been synthesized and successfully utilized as ancillary ligands for neutral iridium(III) complexes of the formula [Ir(dFppy)2(LX)], where dFppyH is 2‐(2,4‐difluorophenyl)pyridine and LX is tribenzoylmethane (tbm) or 1‐phenyl‐3‐(4‐(pyridin‐2‐yl)phenyl)propane‐1,3‐dione (pydbm). The modification of the ligands aims to prevent or enhance possible intermolecular interactions between the dFppy and/or the LX moiety in comparison with the previously reported [Ir(dFppy)2(dbm)] complex. The aggregation induced emission (AIE) properties of these complexes are significantly modulated, as a consequence of the different π–π interactions revealed by X‐ray crystallography. The structural and photophysical properties of neutral iridium(III) complexes using modified β‐diketonates as ancillary ligands have been investigated, resulting in significantly modulated aggregation induced emission properties. [ABSTRACT FROM AUTHOR]

The Front Cover shows the two Ir complexes bearing β‐diketone/triketonate ligands. Upon UV light irradiation in the solid state, both molecules show visible emission ranging from yellow to red. This emission is negligible in solution, confirming that these compounds are aggregation‐induced emitters (AIE). The molecular packing in the crystal and the alteration of the π–π stacking involving the ancillary ligands determines the nature of the emission. The importance of structural parameters in comprehending the solid‐state phosphorescence of Ir complexes is highlighted by merging the experimental solid‐state emissions and crystal structures of the complexes. More information can be found in the Full Paper by D. Jacquemin, M. I. Ogden, M. Massi, E. Zysman‐Colman et al. For more on the story behind the cover research, see the Cover Profile. [ABSTRACT FROM AUTHOR]