Chemical Bonding in Silicon Carbonyl Complexes

Although silylene-carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re-evaluated to explain the origins of their remarkable stability within the Kohn-Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor-acceptor interaction: a σ-donation from the σCO into the empty p-orbital of silicon, and a π-back donation from the sp2 lone pair of silicon into the π*CO antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si−CO compounds, however, is another π-back donation from a perpendicular bonding R−Si σ-orbital into the π*CO antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the π-back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene-carbonyl chemistry

Evidence of AlII Radical Addition to Benzene

Electrophilic AlIII species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent AlI aluminyl anions have showcased oxidative additions towards arenes C−C and/or C−H bonds. Herein, we communicate compelling evidence of an AlII radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC8 in benzene furnishes a double addition to the benzene ring instead of a C−H bond activation, producing the corresponding cyclohexa-1,3(orl,4)-dienes as Birch-type reduction product. X-ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable AlII radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection

Evidence of AlII Radical Addition to Benzene

Electrophilic AlIII species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent AlI aluminyl anions have showcased oxidative additions towards arenes C-C and/or C-H bonds. Herein, we communicate compelling evidence of an AlII radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC8 in benzene furnishes a double addition to the benzene ring instead of a C-H bond activation, producing the corresponding cyclohexa-1,3(orl,4)-dienes as Birch-type reduction product. X-ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable AlII radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection

Evidence of AlII Radical Addition to Benzene

Electrophilic AlIII species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent AlI aluminyl anions have showcased oxidative additions towards arenes C C and/or C H bonds. Herein, we communicate compelling evidence of an AlII radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC8 in benzene furnishes a double addition to the benzene ring instead of a C H bond activation, producing the corresponding cyclohexa-1,3 (orl,4)-dienes as Birch-type reduction product. X-ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable AlII radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection

Twisted Push-Pull Alkenes Bearing Geminal Cyclicdiamino and Difluoroaryl Substituents

The systematic combination of N-heterocyclic olefins (NHOs) with fluoroarenes resulted in twisted push-pull alkenes. These alkenes carry electron-donating cyclicdiamino substituents and two electron-withdrawing fluoroaryl substituents in the geminal positions. The synthetic method can be extended to a variety of substituted push-pull alkenes by varying the NHO as well as the fluoroarenes. Solid-state molecular structures of these molecules reveal a notable elongation of the central C-C bond and a twisted geometry in the alkene motif. Absorption properties were investigated with UV-vis spectroscopy. The redox properties of the twisted push-pull alkenes were probed with electrochemistry as well as UV-vis/NIR and EPR spectroelectrochemistry, while the electronic structures were computationally evaluated and validated.Fil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Universitat Stuttgart; AlemaniaFil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Pal, Sudip. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Universität Stuttgart; AlemaniaFil: Chandrasekhar, Vadapalli. Indian Institute Of Technology Kanpur; IndiaFil: Jana, Anukul. Tata Institute Of Fundamental Research, Hyderabad; Indi

Trisubstituted Geminal Diazaalkenes Derived Transient 1,2-Carbodications

Coulombic repulsion between two adjacent cation centres of 1,2-carbodications are known to decrease with π- and/or n-donor substituents by the positive charge delocalization. Here we report the delocalization of positive charge of transient 1,2-carbodications having one H-substituent by an intramolecular base-coordination. N-heterocyclic olefin (NHO) derived 2-pyrrolidinyl appended trisubstituted geminal diazaalkenes were employed for the generation of transient 1,2-carbodications through a 2-e chemical oxidation process. We have also studied the 1-e oxidation reaction of trisubstituted geminal diazaalkenes (electrochemically and chemically) and also studied them by in situ EPR spectroscopy.Fil: Mandal, Debdeep. Indian Institute of Technology; IndiaFil: Stein, Felix. Freie Universität Berlin; AlemaniaFil: Chandra, Shubhadeep. Universitat Stuttgart;Fil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Sarkar, Pallavi. Indian Institute of Technology; IndiaFil: Das, Shubhajit. Indian Institute of Technology; IndiaFil: Kundu, Abhinanda. Indian Institute of Technology; IndiaFil: Sarkar, Arighna. Indian Institute of Technology; IndiaFil: Rawat, Hemant. Indian Institute of Technology; IndiaFil: Pati, Swapan. Indian Institute of Technology; IndiaFil: Chandrasekhar, Vadapalli. Indian Institute of Technology; IndiaFil: Sarkar, Biprajit. Universität Stuttgart;Fil: Jana, Anukul. Indian Institute of Technology; Indi

Activation of Aromatic C‐F Bonds by a N‐Heterocyclic Olefin (NHO)

A N-heterocyclic olefin (NHO), a terminal alkeneselectively activates aromatic C-F bonds without the need of anyadditional catalyst. As a result, a straightforward methodology wasdeveloped for the formation of different fluoroaryl substituted alkenesin which the central carbon-carbon double bond is in a twistedgeometry.Fil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Freie Universität Berlin.; AlemaniaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Sarkar, Arighna. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Freie Universität Berlin.; AlemaniaFil: Mote, Kaustubh R.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandrasekhar, Vadapalli. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Jana, Anukul. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

Molecular enneanuclear CuII phosphates containing planar hexanuclear and trinuclear sub-units: syntheses, structures, and magnetism

Highly symmetric enneanuclear copper(II) phosphates [Cu9(Pz)6(μ-OH)3(μ3-OH)(ArOPO3)4(DMF)3] (PzH =pyrazole, Ar = 2,6-(CHPh2)2-4-R-C6H2; R = Me, 2MeAr; Et, 2EtAr; iPr, 2iPrAr; and Ar = 2,6-iPr2C6H3, 2Dip) comprising nine copper(II) centers and pyrazole, hydroxide and DMF as ancillary ligands were synthesized by a reaction involving the arylphosphate monoester, 1, copper(I)chloride, pyrazole, and triethylamine in a 4 : 9 : 6 : 14 ratio. All four complexes were characterized by single crystal structural analysis. The complexes contain two distinct structural motifs within the multinuclear copper scaffold: a hexanuclear unit and a trinuclear unit. In the latter, the three Cu(II) centres are bridged by a µ3-OH. Each pair of Cu(II) centers in the trinuclear unit are bridged by a pyrazole ligand. The hexanuclear unit is made up of three dinuclear Cu(II) motifs where the two Cu(II) centres are bridged by an -OH and a pyrazole ligand. The three dinuclear units are connected to each other by phosphate ligands. The latter also aid the fusion of the trinuclear and the hexanuclear motifs. Magnetic studies reveal a strong antiferromagnetic exchange between the Cu(II) centres of the dinuclear units in the hexanuclear part and a strong spin frustration in the trinuclear part leading to a degenerate ground state

CalyPSO: An Enhanced Search Optimization based Framework to Model Delay-based PUFs

Delay-based Physically Unclonable Functions (PUFs) are a popular choice for “keyless” cryptography in low-power devices. However, they have been subjected to modeling attacks using Machine Learning (ML) approaches, leading to improved PUF designs that resist ML-based attacks. On the contrary, evolutionary search (ES) based modeling approaches have garnered little attention compared to their ML counterparts due to their limited success. In this work, we revisit the problem of modeling delaybased PUFs using ES algorithms and identify drawbacks in present state-of-the-art genetic algorithms (GA) when applied to PUFs. This leads to the design of a new ES-based algorithm called CalyPSO, inspired by Particle Swarm Optimization (PSO) techniques, which is fundamentally different from classic genetic algorithm design rationale. This allows CalyPSO to avoid the pitfalls of textbook GA and mount successful modeling attacks on a variety of delay-based PUFs, including k-XOR APUF variants. Empirically, we show attacks for the parameter choices of k as high as 20, for which there are no reported ML or ES-based attacks without exploiting additional information like reliability or power/timing side-channels. We further show that CalyPSO can invade PUF designs like interpose-PUFs (i-PUFs) and (previously unattacked) LP-PUFs, which attempt to enhance ML robustness by obfuscating the input challenge. Furthermore, we evolve CalyPSO to CalyPSO++ by observing that the PUF compositions do not alter the input challenge dimensions, allowing the attacker to investigate cross-architecture modeling. This allows us to model a k-XOR APUF using a (k − 1)-XOR APUF as well as perform cross-architectural modeling of BRPUF and i-PUF using k-XOR APUF variants. CalyPSO++ provides the first modeling attack on 4 LP-PUF by reducing it to a 4-XOR APUF. Finally, we demonstrate the potency of CalyPSO and CalyPSO++ by successfully modeling various PUF architectures on noisy simulations as well as real-world hardware implementations

Assembly of NHC-stabilized 2-hydrophosphasilenes from Si(iv) precursors: a Lewis acid-base complex

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