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1. Structural deformation and host–guest properties of doubly-reduced cycloparaphenylenes, [ n ]CPPs ²⁻ ( n = 6, 8, 10, and 12)

   https://doi.org/10.1039/D0SC03072D  

   Zhou, Zheng; Wei, Zheng; Schaub, Tobias A.; Jasti, Ramesh; Petrukhina, Marina A. (September 2020, Chemical Science)

   null (Ed.)

   Chemical reduction of several cycloparaphenylenes (CPPs) ranging in size from [8]CPP to [12]CPP has been investigated with potassium metal in THF. The X-ray diffraction characterization of the resulting doubly-reduced [ n ]CPPs provided a unique series of carbon nanohoops with increasing dimensions and core flexibility for the first comprehensive structural analysis. The consequences of electron acquisition by a [ n ]CPP core have been analyzed in comparison with the neutral parents. The addition of two electrons to the cyclic carbon framework of [ n ]CPPs leads to the characteristic elliptic core distortion and facilitates the internal encapsulation of sizable cationic guests. Molecular and solid-state structure changes, alkali metal binding and unique size-dependent host abilities of the [ n ]CPP 2− series with n = 6–12 are discussed. This in-depth analysis opens new perspectives in supramolecular chemistry of [ n ]CPPs and promotes their applications in size-selective guest encapsulation and chemical separation. 

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2. Dynamics of rotation in two‐coordinate thiazolyl copper(I) carbazolyl complexes

   https://doi.org/10.1002/aoc.6728  

   Ma, Jie; Kapper, Savannah_C; Ponnekanti, Aamani; Schaab, Jonas; Djurovich, Peter_I; Thompson, Mark_E (May 2022, Applied Organometallic Chemistry)

   Two‐coordinate carbene Cu(Ι) amide complexes with sterically bulky groups such as the diisopropyl phenyl (dipp) on the carbenes have been shown to have comparable performance to the phosphorescent emitters bearing heavy atoms such as iridium and platinum. These bulky groups enforce a coplanar molecular structure and suppress the nonradiative decay rates. Here, three different two‐coordinate Cu(Ι) complexes were investigated that bear a common thiazole carbene, 3‐(2,6‐diisopropylphenyl)‐4,5‐dimethylthiazol‐2‐ylidene, with only a single dipp group, and carbazolyl ligands with substituents of varying steric bulkorthoto N. These substituents have a negligible impact on luminescence energies of the complexes but serve to modulate the rotation barriers along the metal–ligand coordinate bond. The geometric arrangement of ligands (syn‐ oranti‐conformer) in complexes with alkyl substituents were found to differ, beingsynin the solid state versusantiin solution as revealed by crystallographic analysis and nuclear magnetic resonance spectroscopy. In addition, calculations were performed to determine potential energy surfaces for different conformations of the three complexes to provide a theoretical evaluation of rotation barriers around the metal–ligand bond axis. The relationship between rotation barriers and photophysical properties demonstrate that rates for nonradiative decay decrease with increasing bulk of the substituents on the carbazolyl ligand. 

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3. Photochemistry of N ‐Phenyl Dibenzothiophene Sulfoximine ^†

   https://doi.org/10.1111/php.13456  

   Isor, Ankita; Hommelsheim, Renè; Cone, Grant W.; Frings, Marcus; Petroff, II, John T.; Bolm, Carsten; McCulla, Ryan D. (June 2021, Photochemistry and Photobiology)

   Abstract Sulfoximines are popular scaffolds in drug discovery due to their hydrogen bonding properties and chemical stability. In recent years, the role of reactive intermediates such as nitrenes has been studied in the synthesis and degradation of sulfoximines. In this work, the photochemistry ofN‐phenyl dibenzothiophene sulfoximine [5‐(phenylimino)‐5H‐5λ⁴‐dibenzo[b,d]thiopheneS‐oxide] was analyzed. The structure resembles a combination ofN‐phenyl iminodibenzothiophene and dibenzothiopheneS‐oxide, which generate nitrene and O(³P) upon UV‐A irradiation, respectively. The photochemistry ofN‐phenyl dibenzothiophene sulfoximine was explored by monitoring the formation of azobenzene, a photoproduct of triplet nitrene, using direct irradiation and sensitized experiments. The reactivity profile was further studied through direct irradiation experiments in the presence of diethylamine (DEA) as a nucleophile. The studies demonstrated thatN‐phenyl dibenzothiophene sulfoximine underwent S–N photocleavage to release singlet phenyl nitrene which formed a mixture of azepines in the presence of DEA and generated moderate amounts of azobenzene in the absence of DEA to indicate formation of triplet phenyl nitrene. 

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4. Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes

   https://doi.org/10.1021/acs.inorgchem.3c04391  

   Valerio, Leyla R; Hakey, Brett M; Leary, Dylan C; Stockdale, Erin; Brennessel, William W; Milsmann, Carsten; Matson, Ellen M (February 2024, Inorganic Chemistry)

   A series of pyridine dipyrrolide actinide(IV) complexes, (MesPDPPh)AnCl2(THF) and An(MesPDPPh)2 (An = U, Th, where (MesPDPPh) is the doubly deprotonated form of 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine), have been prepared. Characterization of all four complexes has been performed through a combination of solid- and solution-state methods, including elemental analysis, single crystal X-ray diffraction, and electronic absorption and nuclear magnetic resonance spectroscopies. Collectively, these data confirm the formation of the mono- and bis-ligated species. Time-dependent density functional theory has been performed on all four An(IV) complexes, providing insight into the nature of electronic transitions that are observed in the electronic absorption spectra of these compounds. Room temperature, solution-state luminescence of the actinide complexes is presented. Both Th(IV) derivatives exhibit strong photoluminescence; in contrast, theU(IV) species are nonemissive. 

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5. Stereo-electronic effect of the perfluoropropyl group on the solid-state molecular packing of isomeric dibenzo[ a , c ]phenazine derivatives

   https://doi.org/10.1039/d2ce00019a  

   Putta, Anjaneyulu; Gairhe, Shankar; Feng, Yao; Sun, Haoran (March 2022, CrystEngComm)

   We report here the synthesis, characterization, and crystal structures of three perfluoropropylated dibenzo[ a , c ]phenazine constitutional isomers, in which the only difference among them was the positions of the perfluoropropyl substituents. The crystal structures of these perfluropropylated dibenzo[ a , c ]phenazine isomers indicated that the stereo-electronic effect of the perfluoropropyl group on the dibenzo[ a , c ]phenazine molecule plays a crucial role in determining the crystal-packing motif in the solid state. Our results from both X-ray crystallography and computational approaches revealed that the positions of the perfluoropropyl groups on the dibenzo[ a , c ]phenazine ring significantly affected the electrostatic potential distribution along the aromatic ring surface, resulting in drastic changes in the molecular packing in the solid state, from herringbone to lamellar crystal packing, among these three constitutional isomers. Simple topological consideration of the molecular packing in the solid state was coincidently cooperative with the changes in the electrostatic potential distributions, where localized partial positive and partial negative charges perhaps dominated the intermolecular interactions between the aromatic rings. Together, the perfluoropropylation on the dibenzo[ a , c ]phenazine ring provided us with a fortunate scenario, wherein the molecular topological structure and electrostatic potential worked together to facilitate the formation of the desired lamellar π–π stacked crystal packing. Meanwhile, electrochemistry, UV-visible absorption and emission spectra, and the computational chemistry results pointed out that there were only minor to moderate changes in the electronic properties of the molecules upon changing the position of the perfluoroalkylation on the dibenzo[ a , c ]phenazine core. While controlling the solid-state structure of aromatics by design still has a long way to go, we hope that our work will ignite a spark that can potentially spread into the field of the design of organic solid-state materials. 

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