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    Air and moisture stable para- and ortho-quinodimethane derivatives derived from bis-N-Heterocyclic olefins
    (American Chemical Society, 2023) Jana, Subhadip; Elvers, Benedict J.; Patsch, Sebastian; Sarkar, Pallavi; Krummenacher, Ivo; Nayak, Mithilesh Kumar; Maiti, Avijit; Chrysochos, Nicolas; Pati, Swapan K.; Schulzke, Carola; Braunschweig, Holger; Yıldız, Cem Bural
    Herein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of bis-Nheterocyclic olefins linked by different pi-conjugated aromatic spacers. In case of paraand ortho-phenylene bridge, we obtained air and moisture stable diimidazolium paraand ortho-quinodimethane derivatives. Analogues of the para-phenylene spacer such as tetrafluoro-p-phenylene and p-anthracene also led to the corresponding air and moisture stable quinodimethane derivatives. This emphasizes the influence of imidazolium substituents which facilitate the air and moisture stability of the quinodimethane derivatives. Differences were observed for the electron transfer processes: two one-electron vs one two-electron redox transitions between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes depending on the employed pi-conjugated aromatic spacer. The formation of the pi-conjugated radical-cations, transient redox intermediates between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes, was addressed by an EPR investigation.
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    Assembly of NHC-stabilized 2-hydrophosphasilenes from Si(iv) precursors: a Lewis acid-base complex
    (Royal Society of Chemistry, 2016) Dhara, Debebrata; Mandal, Debdeep; Maiti, Avijit; Yıldız, Cem Burak; Kalita, Pankaj; Chrysochos, Nicolas; Schulzke, Carola; Chandrasekhar, Vadapalli; Jana, Anukul
    NHC-stabilized 2-hydrophosphasilenes are obtained from 1,2-dihydro-2-chlorophosphasilanes as Si(iv) precursors by a NHC-assisted 1,2-elimination of HCl. The NHC-exchange of these compounds is demonstrated as a proof of donor acceptor bonding between NHC and the silicon centre of the “P” moiety. We have also explored the possibility of similar exchanges in NHC-stabilized Si2 and P2 compounds. Theoretical DFT calculations were performed to address the nature of Si-P bonding in the NHC-stabilized 2-hydrophosphasilenes. © The Royal Society of Chemistry.
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    Comment on "Disclosing Cyclic(Alkyl)(Amino)Carbenes as a One-Electron Reductant: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids"
    (Wiley-VCH - Home, 2023) Maiti, Avijit; Elvers, Benedict J.; Bera, Sachinath; Lindl, Felix; Krummenacher, Ivo; Ghosh, Prasanta; Braunschweig, Holger; Yıldız, Cem B.; Schulzke, Carola
    The authors would like to correct a misassignment of an EPR spectrum in the title paper (https://doi.org/10.1002/chem. 202104567). The authors of the original paper reported the one-electron oxidation of the cyclic(alkyl)(amino)carbene (CAAC) 1 to produce the intermediate iminium radical cation 2, as deduced from the high isolated yield of the hydrogen abstraction product 3 (Figure 1). By low-temperature (200 K) EPR spectroscopy, we observed a weak transient, three-line EPR spectrum with a g-factor of 2.0043 and a 14N hyperfine splitting (hfs) of a( 14N)=5.9 G, which we attributed to the radical cation 2 (the spectrum was depicted as Figure 1b, in the TOC cover image, in the Cover Feature (https://doi.org/10.1002/chem. 202201219), and as Figure S46 of the original paper). However, as one of the present authors (H.G.K.) later pointed out, the foregoing EPR parameters, in particular the g-factor, would not be in agreement with the proposed vinyl-type ?-radical cation.
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    ?,??-Diamino-p-quinodimethanes with three stable oxidation states
    (American Chemical Society, 2020) Mahata, Alok; Chandra, Shubhadeep; Maiti, Avijit; Rao, D. Krishna; Yıldız, Cem Burak; Sarkar, Biprajit; Jana, Anukul
    Herein, we report the rational design, synthesis, and characterization of ?,??-diamino-substituted-p-quinodimethanes, which are a group of partially substituted p-quinodimethanes. These exhibit two reversible one-electron redox steps and electrochromism in the ultraviolet, visible, and near-infrared regions. We were able to isolate the crystalline compounds of all three oxidation states: neutral, radical cation, and dication. The obtained results not only create the bridge between p-quinodimethane and ?,?,??,??-tetrasubstituted-p-quinodimethane, but also demonstrate the straightforward modular approach for the synthesis of ?-conjugated open-shell compounds.
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    Disclosing Cyclic(Alkyl)(Amino)Carbenes as a One-Electron Reductant: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids
    (Wiley, 2023) Maiti, Avijit; Elver, Benedict J.; Bera, Sachinath; Lindl, Felix; I-Krummenacher, Ivo; Krummenacher, Ivo; Ghosh, Prasanta; Yıldız, Cem Burak; Braunschweig, Holger; Schulzke, Carola; Jana, Anukul
    Herein we disclose cyclic(alkyl)(amino)carbenes (CAACs) as a one-electron reductant under the formation of a transient radical cation as indicated by EPR spectroscopy. Subsequently, the disclosed CAAC reducing reactivity was utilized for the synthesis of acyclic(amino)(aryl)carbene-based Thiele and Chichibabin hydrocarbons, a new class of Kekulé diradicaloids. The results demonstrate the CAAC to be a potent organic reductant. Notably, the acyclic(amino)(aryl)carbene-based Chichibabin's hydrocarbon shows an appreciable population of the triplet state at room temperature, as evidenced by both variable temperature NMR and EPR spectroscopy.