@article {49393, title = {Activation of carbon disulfide by a hypersilyl germylene}, journal = {Dalton Transactions}, volume = {53}, year = {2024}, month = {JUL}, type = {Article}, abstract = {

In this work, the insertion of CS2 into the Ge-Si bond of PhC(NtBu)2Ge-Si(SiMe3)3 (1) has been investigated, resulting in the formation of PhC(NtBu)2Ge-C( 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 S)-S-Si(SiMe3)3 (2). Interestingly, the addition of NHC to 2 allows the release of NHCCS2 with concomitant regeneration of 1. Addition of another equivalent of 1 or an analogous hypersilyl silylene, [PhC(NtBu)2Si-Si(SiMe3)3], to 2 led to the formation of compounds with a GeS (3) or a SiS (4) bond. In this work, the insertion of CS2 into the Ge-Si bond of PhC(NtBu)2Ge-Si(SiMe3)3 (1) has been investigated, resulting in the formation of PhC(NtBu)2Ge-C(S)-S-Si(SiMe3)3 (2).

}, issn = {1477-9226}, doi = {10.1039/d4dt01573h}, author = {Ajithkumar, V. S. and Khilari, Nripen and Ghanwat, Pratiksha B. and Venugopal, Geethu and Koley, Debasis and Sen, Sakya S.} } @article {49100, title = {Boron- and oxygen-doped π-extended helical nanographene with circularly polarised thermally activated delayed fluorescence}, journal = {Chemistry-A European Journal}, volume = {30}, year = {2024}, month = {APR }, type = {Article}, abstract = {

Helical nanographenes have garnered substantial attention owing to their finely adjustable optical and semiconducting properties. The strategic integration of both helicity and heteroatoms into the nanographene structure, facilitated by a boron-oxygen-based multiple resonance (MR) thermally activated delayed fluorescence (TADF), elevates its photophysical and chiroptical features. This signifies the introduction of an elegant category of helical nanographene that combines optical (TADF) and chiroptical (CPL) features. In this direction, we report the synthesis, optical, and chiroptical properties of boron, oxygen-doped pi-extended helical nanographene. The pi-extension induces distortion in the DOBNA-incorporated nanographene, endowing a pair of helicenes, (P)-B2NG, and (M)-B2NG exhibiting circularly polarized luminescence with glum of -2.3x10-3 and +2.5x10-3, respectively. B2NG exhibited MR-TADF with a lifetime below 5 mu s, and a reasonably high fluorescence quantum yield (50 \%). Our molecular design enriches the optical and chiroptical properties of nanographenes and opens up new opportunities in multidisciplinary fields. B, O-doped pi-extended helical nanographene has been explored for its optical and chiroptical properties. The presence of helical and nanographene segments stabilize the helicity and imparts tunable optical properties. Helical nanographene display circularly polarized thermally activated delayed fluorescence. image

}, keywords = {circularly polarized luminescence, DOBNA, dual emission, nanographene, TADF}, issn = {0947-6539}, doi = {10.1002/chem.202304169}, author = {Venugopal, Geethu and Kumar, Viksit and Jadhav, Ashok Badrinarayan and Dongre, Sangram D. and Khan, Abujunaid and Gonnade, Rajesh and Kumar, Jatish and Santhosh Babu, Sukumaran} } @article {49318, title = {Tailoring helical ends of π-extended [6]heterohelicenes to control optical, and electrochemical features}, journal = {Chemical Communications}, volume = {60}, year = {2024}, month = {OCT }, pages = {11944-11947}, type = {Article}, abstract = {

The inherent helical chirality and improved pi-stacking capabilities endow helicenes with fascinating photophysical characteristics when decorated with lateral pi-extensions. Here, we report the synthesis and physicochemical characterization of expanded hetero[6]helicenes fused with thiadiazole and selenadiazole rings at the helical ends. Comparing these heterohelicenes revealed the impact of the heteroatom-embedded aromatic rings on the excited state and redox features. A small structural variation of the terminal rings from thiadiazole to selenadiazole caused a striking change in the heterohelical nanographenes. The inherent helical chirality and improved pi-stacking capabilities endow helicenes with fascinating photophysical characteristics when decorated with heteroatoms.

}, issn = {1359-7345}, doi = {10.1039/d4cc03707c}, author = {Kumar, Viksit and Dongre, Sangram D. and Venugopal, Geethu and Narayanan, Aswini and Babu, Sukumaran Santhosh} } @article {49607, title = {Chiroptical amplification of [7]-helicene nanographene by additional helical chirality}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {FEB }, pages = {e202420767}, type = {Article}, abstract = {

Nanographenes have captivated scientific interest since the pioneering discovery of graphene. Recently, attention has shifted towards exploring chiral and nonplanar nanographenes, for their distinct optical, chiroptical, and electronic properties. Despite the growing acceptance of helicenes, the research on inducing helical chirality on pi-extended derivatives to boost chiroptical properties remains unattended. In our study, we introduce a new pi-extended [7]-helicene resulting from the condensation of diamines with 3,6-dibromophenanthrene-9,10-dione, complemented by two hexabenzocoronene arms in the periphery. Notably, the nanographene containing binaphtho-[1,4]diazocine, compared to the corresponding phenazine, exhibits a remarkable average 2.5, 5, and 10-fold enhancements in quantum yield, dissymmetry factor, and brightness, respectively, when measured in five different solvents. These improvements underscore the significance of the induced helical chirality by the antiaromatic binaphtho-[1,4]diazocine in influencing the chiroptical properties of the helical nanographene. Our research represents a significant stride toward unlocking the potential of pi-extended helicenes and lays the groundwork for further exploration in designing and synthesizing new chiral nanomaterials.

}, keywords = {circularly polarised luminescence, dissymmetry factor, helicene, nanographene, quantum yield}, doi = {10.1002/anie.202420767}, author = {Dongre, Sangram D. and Venugopal, Geethu and Kumar, Viksit and Badrinarayan Jadhav, Ashok and Kumar, Jatish and Babu, Sukumaran Santhosh} } @article {49616, title = {Germylene mediated reductive C-C and C-N coupling of an isocyanide and its device application}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {FEB }, type = {Article}, abstract = {

We have demonstrated a unique reductive coupling of 4-iodophenyl isocyanide, facilitated by a perimidine-based N-heterocyclic germylene (NHGe), which yields a bis-spirogerma compound featuring simultaneous C-C and C-N bond formation. This reaction, which leads to the oxidation of germanium from +2 to +4, represents a significant departure from previously documented isocyanide-germylene interactions. The product exhibits extensive conjugation across its bicyclic C4Ge2N2 framework, conferring distinct photophysical properties, including prominent orange luminescence in both solution and solid states. The photophysical properties are supported by the TD-DFT calculations confirming an n -\>pi* transition. The potential application of this compound in optoelectronic devices, particularly as a hole transport layer in PbS quantum dot solar cells, is also explored, with promising preliminary results.

}, keywords = {Germylene, hole transport layer, Isocyanide, reductive coupling}, doi = {10.1002/anie.202417052}, author = {Gour, Kritika and Pramanik, Debjit and Dash, Soumya Ranjan and Shinde, Dipak Dattatray and Venugopal, Geethu and Vanka, Kumar and Rath, Arup K. and Sen, Sakya S.} } @article {49568, title = {Regioisomeric π-extended nanographene with long-lived phosphorescence afterglow}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {FEB}, pages = {e202422125}, type = {Article}, abstract = {

The cutouts of graphene sheets, particularly those with a nonplanar topology, present vast opportunities for advancement. Even a slight deviation from the planar structure can lead to intriguing (chiro)optical features for helically twisted nanographenes. In this context, we introduce two regioisomeric pi-extended nanographenes that exhibit distinct excited-state characteristics. The helicene structure and the photophysical features can be easily tuned by changing the connecting position of the nanographene to the carbazole core (2,7- and 3,6-). Single-crystal X-ray diffraction analysis confirmed the formation of nanographenes with bent and helical conformations. Both derivatives exhibited thermally activated delayed fluorescence at room temperature and phosphorescence at low temperatures. Notably, the nanographene with the bent structure displayed an impressive red afterglow lasting over 30seconds, in contrast to the very weak afterglow observed in the helical structure. DFT calculations revealed the existence of an isoenergetic higher triplet state (T-8) and comparatively weak spin-orbit coupling (T-1-S-0), thereby enabling the bent nanographene to exhibit a long-lived component and strong afterglow. Our findings highlight the significance of regioisomeric nanographenes with exceptional optical properties and offer a deeper understanding of the structure-property relationship in nonplanar nanographenes.

}, keywords = {Afterglow, CPL, Helicenes, nanographene, Phosphorescence, TADF}, doi = {10.1002/anie.202422125}, author = {Kumar, Viksit and Venugopal, Geethu and Jadhav, Ashok Badrinarayan and Dongre, Sangram D. and Gonnade, Rajesh and Kumar, Jatish and Ruer, Paul C. and Hupp, Benjamin and Steffen, Andreas and Babu, Sukumaran Santhosh} }