Estimating structure, stability, and electronic properties on halogenated derivatives of 2-germabicyclo[1.1.1.]pentane-2-ylidenes at density functional theory.

In this computational survey, substituent effects of group 17 on the stability (singlet-triplet energy gaps, ΔEs-t) and reactivity of singlet (s) and triplet (t) forms of 2-germabicyclo[1.1.1.]pentane-2-ylidenes are considered by using B3LYP/6-311 + + G**, B3LYP/aug-cc-pvtz, and B3LYP/def2-TZVP level of theories. In all germylene structures, singlets appear more stable than their corresponding triplet congeners, revealing a singlet ground state and the order of stability appears to be 1,3,4,4,5,5-hexachloro-2-germabicyclo[1.1.1.]pentane-2-ylidenes (3) > 1,3,4,4,5,5-hexabromo-2-germabicyclo[1.1.1.]pentane-2-ylidenes (4) > 1,3,4,4,5,5-hexafluoro-2-germabicyclo[1.1.1.]pentane-2-ylidenes (2) > 1,3,4,4,5,5-hexaiodo-2-germabicyclo[1.1.1.]pentane-2-ylidenes (5) > 2-germabicyclo[1.1.1.]pentane-2-ylidenes (1), at the three levels of theory. The positive and negative effects on germylene stability are LP(F, Cl, Br, and I) → LP*G̈e and σ(C-Ge) → σ*(C-F, Cl, Br, and I) interactions, respectively. The results of our calculations show that every singlet germylene with high LP(F, Cl, Br, and I) → LP*G̈e interactions has higher electrophilicity. Also, in going from the most electronegative F to the least electronegative I, the nucleophilicity index (N) for germylene increases. Finally, this survey introduces that germylene 4 s with rather high band gap (ΔEHOMO-LUMO = 97.19 kcal/mol), nucleophilicity (2.20 eV), and stability (ΔEs-t = 76.95 kcal/mol) has high proton affinity (171.55 kcal/mol) that can be applied as multidentate ligands and it is hoped that this will prompt experimental attention toward its.

Substitution effects on novel bicyclo[2.2.1]hepta-7-silylenes by DFT.

Substitution effects on stability (ΔΕs-t) of novel singlet and triplet forms of bicyclo[2.2.1]hepta-7-silylenes are compared and contrasted, at B3LYP/6-311++G** level of theory. All species appear as ground state minima on their energy surface, for showing no negative force constant. Singlets (1s-24s) are ground state and more stable than their corresponding triplets (1t-24t). The most stable scrutinized silylenes appear to be 2,3-disilabicyclo[2.2.1]hepta-7-silylene (9) for showing the highest value of ΔEs-t. This stability can be related to our imposed topology and ß-silicon effect. The band gaps (ΔΕHOMO-LUMO) show the same trend as ΔEs-t and the lowest unoccupied molecular orbital energies. Also, the electrophilicity appears inverse correlation with our results of ΔΕs-t. The purpose of the present work was to assess the influence of 1 to 6 silicon substitutions on the stability, band gaps, nucleophilicity, electrophilicity, and proton affinity. Finally, our investigation introduces novel silylenes with possible applications in chemistry such as semiconductors, cumulated multidentate ligands, etc. Synopsis Substitution effects on stability (ΔΕs-t) of novel singlet (s) and triplet (t) forms of bicyclo[2.2.1]hepta-7-silylenes are compared and contrasted, at B3LYP/6-311++G** level of theory. All species appear as ground state minima on their energy surface, for showing no negative force constant. Singlets (1s-24s) are ground state and more stable than their corresponding triplets (1t-24t). The most stable scrutinized silylenes appear to be 2,3-disilabicyclo[2.2.1]hepta-7-silylene (9) for showing the highest value of ΔEs-t. This stability can be related to our imposed topology and ß-silicon effect. The purpose of the present work was to assess the influence of 1 to 6 silicon substitutions on stability (ΔΕs-t), band gaps (ΔΕHOMO-LUMO), nucleophilicity (N), electrophilicity (ω), and proton affinity (ΔΕPA). Finally, this new generation has the intrinsic potential to form accumulated multidentate ligands.

New pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole, by DFT.

We have investigated the pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole (1a, 2a, 3a, and 4a, respectively), at the M06/6-311++G** level of theory. Optimization and vibrational frequency calculations of ground states (GS) and transition states (TS) are performed to identify Gibbs free energies and nature of stationary points, respectively. Two possible pathways of stability for 1a-4a are compared and contrasted which entail dimerization through hydrogen bonding (HB) and covalent bonding (CB). The CB pathway comprises head to head (HH) and head to tail (HT) dimerizations. Plausible reaction profiles are illustrated for 1a-4a along with the mechanism of each dimerization. Structures 1a-3a show one possibility for HB while 4a represents two possibilities. Structures 1a and 4a display two HH dimers while 2a and 3a show one. Structures 1a-4a undergo HT dimerizations to yield three possible dimers which include trans, cis, and [2+3] isomers. Interestingly, for all 1a-4a, HB dimerization turns out as the most favorable stability pathway for showing no barrier of reaction. Structures 4b and 4c indicate the highest stability with respect to their initial 4a compared to remaining HB dimers 1b-3b. In addition, the 1,2-H shift appears as a possible rearrangement for 1a-4a to yield their corresponding tautomers (1i, 2h, 3h, and 4k, respectively). The reaction profile of this rearrangement indicates that 1a-4a favor HB dimerization pathway more than 1,2-H shift, in terms of kinetic and thermodynamic. Graphical Abstract.