TY  - JOUR
AB  - Dihydroxymagnesium carboxylates [(OH)MgOCR] were probed for decarboxylation on a theoretical level, by utilizing both Møller-Plesset perturbation theory (MP2) and density functional theory (B3LYP-DFT) computations. This study is connected to the question of whether this recently introduced, astrobiologically relevant chemical class may form Grignard-type reagent molecules. To extract trends for a broad molecular mass range, different linear alkyl chain lengths between Cand Cwere computed. The forward energy barrier for decarboxylation reactions increases linearly as a function of the ligand's chain length. Decarboxylation-type fragmentations of these organomagnesium compounds seem to be improbable in non-catalytic, low energetic environments. A high forward energy barrier (E > 55 kcal mol) towards a described transition state restricts the release of CO. Nevertheless, we propose the release of COon a theoretical level, as been revealed via an intramolecular nucleophilic attack mechanism. Once the challenging transition state for decarboxylation is overcome, a stable Mg-C bond is formed. These mechanistic insights were gained by help of natural bond orbital analysis. The Cα atom (first carbon atom in the ligand chain attached to the carboxyl group) is thought to prefer binding towards the electrophilic magnesium coordination center, rather than towards the electrophilic CO-carbon atom. Additionally, the putatively formed Grignard-type OH-bearing product molecules possess a more polarized Mg-C bond in comparison to RMgCl species. Therefore, carbanion formation from OH-bearing Grignard-type molecules is made feasible for triggering C-C bond formation reactions. Graphical abstract This study asks whether recently introduced, astrobiologically dihydroxymagnesium carboxylates form Grignard-type reagent molecules via decarboxylative fragmentation.
AU  - Ruf, A.
AU  - Kanawati, B.
AU  - Schmitt-Kopplin, P.
C1  - 53331
C2  - 44659
TI  - Do dihydroxymagnesium carboxylates form Grignard-type reagents? A theoretical investigation on decarboxylative fragmentation.
JO  - J. Mol. Model.
VL  - 24
IS  - 4
PY  - 2018
SN  - 1610-2940
ER  - 

TY  - JOUR
AB  - The geometries, energies, and electronic properties of the two possible configurations of bis-[dibenzo[a.i]fluorenylidene] were investigated theoretically by density functional theory DFT B3LYP at the UB3LYP/6-311 + G(2d,p) // UB3LYP/6-31 + G(d,p) level of theory. According to the performed calculations, it was found that the singlet is 3.4 kcal mol(-1) lower in energy compared to triplet state at room temperature. This gap is compared with those of other alkenes like ethylene, (61.9 kcal mol(-1)) tetra-tert-butyethylene, (6.4 kcal mol(-1)) and bis-fluorenylidene (19.5 kcal mol(-1)). These results confirm the experimental findings of the paramagnetic properties determined by Franzen and Joschek. The low singlet-triplet gap in the case of bis-[dibenzo[a.i]fluorenylidene] is the result of a steric destabilization of the singlet due to strain and stabilization of the triplet electronic state by delocalization of each free electron within each aromatic moiety. This correlates with the special electronic structure of the triplet state of this compound, where facial interaction of two hydrogen atoms lying close to the lobes of each p-orbital occupied with a single electron at the distorted double bond in the triplet electronic state.
AU  - Kanawati, B.
AU  - Genest, A.*
AU  - Schmitt-Kopplin, P.
AU  - Lenoir, D.
C1  - 11349
C2  - 30629
SP  - 5089-5095
TI  - Bis-dibenzo[a.i]fluorenylidene, does it exist as stable 1,2-diradical?
JO  - J. Mol. Model.
VL  - 18
IS  - 12
PB  - Springer
PY  - 2012
SN  - 1610-2940
ER  - 

TY  - JOUR
AU  - Chiappe, C.*
AU  - Pomelli, C.S.*
AU  - Lenoir, D.
AU  - Wattenbach, C.
C1  - 2583
C2  - 23779
SP  - 631-639
TI  - The first intermediates in the bromination of bicyclo[3.3.1]nonylidenebicyclo[3.3.1]nonane, combination of experiments and theoretical results.
JO  - J. Mol. Model.
VL  - 12
PY  - 2006
SN  - 1610-2940
ER  -