Novel halogenated cyclopentasilylene-2,4-dienes via DFT

In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1–4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC₄H₃X ( 1 _X ), SiC₄H₂X₂ ( 2 _X ), SiC₄HX₃ ( 3 _X ), and SiC₄X₄ ( 4 _X ). In going down from F to I, the singlet (s)-triplet (t) energy gap (ΔE_s-t, a possible indication of stability), and band gap (ΔE_H-L) decrease while nucleophilicity (N), chemical potential (μ), and proton affinity (PA) increase. The overall order of N, μ, and PA for each X is 2 _X > 1 _X > 3 _X > 4 _X . Precedence of 2 _X over 1 _X is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2 _I and 4 _F . The trend of divalent angle () for each X is 4 _X > 1 _X > 3 _X > 2 _X . The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the ΔE_s-t and ΔE_H-L decrease while N, μ, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry.     

New monodentate and bidentate silylene ligands by DFT

Considering the importance of silylene ligands in transition metal-mediated catalytic reactions, we have scrutinized eight novel monodentate ( 1 – 4 ) and bidentate ( 1 ^′ - 4 ^′ ) derivatives of 2,5-diX-cyclopentasilylene-2,4-dienes (X = NH₂, OH, PH₂, and SH), at M06/6-311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom ( 1 _Rh - 4 _Rh and 1 ^′ _Rh - 4 ^′ _Rh , respectively), thermodynamic and structural parameters such as complexation energy (ΔE_Com), singlet-triplet energy gap (ΔE_s-t), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH₂ > OH > PH₂ > SH), the σ -donor strength and ligand flexibility increase. Structures 1 and 1 ^′ turn out as the most nucleophilic species for showing the highest nucleophilicity (N = 5.47 and 5.40 eV, respectively). Furthermore, they exhibit the highest proton affinity values (PA = 271.46 and 271.23 kcal/mol, respectively). The results indicate that bidentate coordination mode of silylene leads to a stronger Si-Rh complex. The overall orders of σ -donation ability for monodentate and bidentate silylene ligands are 1 > 2 > 3 > 4 and 1 ^′ > 2 ^′ > 3 ^′ > 4 ^′ , respectively.     

Novel silicon super bases at DFT level of theory: effects of fused benzene rings on the basicity of 2,4,6-cycloheptatrienesilylene

Research on Chemical Intermediates - Super bases are extremely important compounds with high proton affinities (PAs) and many applications in organic, inorganic, polymer, and photochemistry. Here,...     

Detection of bendamustine anti-cancer drug via AlN and Si-doped C nanocone and nanosheet sensors by DFT

Bendamustine or Treanda? is used as an anti-cancer drug, especially in treatment of hematologic malignancies. In view of the immense importance of drug/sensor issues, here we report adsorption behavior of this drug in presence of six nanosensors including aluminum nitride (AlN), carbon, and Si-doped carbon nanocones and nanosheets, at B3LYP/6-31G* level of theory. Electrical conductivity of these nanoadsorbents is probed against that of bendamustine for assessing their abilities of drug sensing with possible implications in drug delivery. The adsorption energy (E_ad), doping energy (E_dop), HOMO energy (E_H), LUMO energy (E_L), HOMO-LUMO band gap (E_g), change of band gaps in percent (%?E_g), change of natural bond orbital (NBO) charges (?Q), conduction electron population (N), and density of state (DOS) plots are calculated. More E_ad, ?Q, and N values imply more interaction between bendamustine and nanosensor which lead to a strong recognition of the drug. The interaction of AlN nanosheet and bendamustine shows the highest E_ad, %?E_g, and ?Q (??28.8 kcal/mol, ??33.6%, and 0.4 e, respectively) which make AlN nanosheet as the most promising among our scrutinized nanosensors. A negative E_dop indicates an exothermic doping process, where Si atom improves the electronic sensitivity of C nanocone and nanosheet. All calculated E_ad and %?E_g turn out as negative values which reveal that electrical conductivity of our scrutinized nanostructures are increased upon adsorbing process which makes them efficient sensors for bendamustine.

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Novel silylphenol antioxidants by density functional theory

We have scrutinized five novel silylphenol antioxidants, including 2-silylphenol ( 1 ), 4-silylphenol ( 2 ), 2,6-disilylphenol ( 3 ), 2,4-disilylphenol ( 4 ), and 2,4,6-trisilylphenol ( 5 ), at M06/6–311++G** level of theory. To evaluate the antioxidant efficiency, the electronic effects on O─H bond dissociation energy (BDE) and vertical ionization potential (IP_v) of 1 – 5 are investigated, which are mainly governed by electronic effects. The conductor-like polarized continuum model (CPCM) is applied to measure the antioxidant capacity in the solution phase. The results show that antioxidants with the lowest BDE and IP_v values can efficiently act via hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms, respectively. The stability of resulting radicals is measured by nucleus independent chemical shift (NICS) index, natural bond orbital (NBO) analysis, and nucleophilicity (N) index. The BDE shows lower values in the gas phase with respect to water, while water exhibits lower IP_v values than gas. Structure 5 turns out as the most efficient antioxidant. The overall order of antioxidant efficiency in both gas and water phases is 5 > 2 > 3 > 4 > 1 .