Twisted and Bent Out of Shape: Symmetry and Chirality Analysis of Substituted Ferrocenes

Kaspi-Kaneti, Ariela; Tuvi-Arad, Inbal

doi:10.1021/acs.organomet.8b00514

Cited by 11 publications

(12 citation statements)

References 45 publications

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“…This behavior is known for other simple alkyl and aryl carbodiimides ( N , N ′-dicyclohexylcarbodiimide, N , N ′-diisopropyl carbodiimide). − Here the reaction is no doubt favored since the two carbodiimide moieties are linked and in close proximity forming exclusively the E , E isomer to minimize steric interactions of the bulky substituents. A recent computational study shows the ability of ferrocene to bend while in the eclipsed conformation thus allowing for intramolecular cyclizations like this to occur . Prolonged storage of 1a and 1d neat and in C 6 D 6 solutions shows no detectable conversion of the carbodiimide, whereas 1b converts to 2b in 42% yield in C 6 D 6 solution after 38 days at room temperature but remains unaltered in the solid state.…”

Section: Resultssupporting

confidence: 61%

“…A recent computational study shows the ability of ferrocene to bend while in the eclipsed conformation thus allowing for intramolecular cyclizations like this to occur. 37 Prolonged storage of 1a and 1d neat and in C 6 D 6 solutions shows no detectable conversion of the carbodiimide, whereas 1b converts to 2b in 42% yield in C 6 D 6 solution after 38 days at room temperature but remains unaltered in the solid state. We were able to isolate the corresponding 2,4-diimino-1,3 diazetidines 2a, 2b, 2c, and 2d by conducting the reaction at ∼100 °C in toluene.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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1,1′-Dicarbodiimidoferrocenes: Synthesis, Characterization, and Group IV 1,1′-Bisguanidinateferrocene Complexes

Palomero

Jones

2019

Organometallics

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We report the two-step one-pot preparation of a series of bulky substituted 1,1′-dicarbodiimidoferrocene proligands. In solution the compounds achieve equilibrium with the corresponding 2,4-diimino-1,3azetidine products which exhibit distinct spectroscopic and electrochemical features. Metalation of the carbodiimides with M(NMe 2 ) 4 (M = Zr, Hf) leads to fluxional six-coordinate compounds that exhibit intermediate Bailar twist features in solution and in the solid state. Coordination of the 2,4-diimino-1,3-diazetidines to Zr(NMe 2 ) 4 results in a metal-mediated carbodiimide metathesis into two zirconium guanidinate complexes, which can be rationalized by a two-step reaction mechanism.

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Section: Resultssupporting

confidence: 61%

Section: ■ Results and Discussionmentioning

confidence: 99%

1,1′-Dicarbodiimidoferrocenes: Synthesis, Characterization, and Group IV 1,1′-Bisguanidinateferrocene Complexes

Palomero

Jones

2019

Organometallics

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“…The CSM measure is a global parameter, and thus allows the comparison of various structures and various symmetries on the same scale. Numerous applications of the CSM methodology all across chemistry have been reported and few examples are collected in the cited references [27][28][29][30] , including biochemistry 14,31,32 and physics 33-37 . types of symmetry analysis. In previous studies 13, 14 we have introduced specific CSM computational tools for the evaluation of the symmetry content, S(G), of proteins.…”

Section: Methodsmentioning

confidence: 99%

The near-symmetry of protein oligomers: NMR-derived structures

Bonjack

Avnir

2020

Sci Rep

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the majority of oligomeric proteins form clusters which have rotational or dihedral symmetry. Despite the many advantages of symmetric packing, protein oligomers are only nearly symmetric, and the origin of this phenomenon is still in need to be fully explored. Here we apply near-symmetry analyses by the continuous Symmetry Measures methodology of protein homomers to their natural state, namely their structures in solution. NMR-derived structural data serves us for that purpose. We find that symmetry deviations of proteins are by far higher in solution, compared to the crystalline state; that much of the symmetry distortion is due to amino acids along the interface between the subunits; that the distortions are mainly due to hydrophilic amino acids; and that distortive oligomerization processes such as the swap-domain mechanism can be identified by the symmetry analysis. Most of the analyses were carried out on distorted C 2-symmetry dimers, but C 3 and D 2 cases were analyzed as well. our nMR analysis supports the idea that the crystallographic B-factor represents non-classical crystals, in which different conformers pack in the crystal, perhaps from the conformers which the NMR analysis provides. The majority of proteins which form oligomers are organized in quaternary structures which are symmetric at least to some degree 1-3. The most prevalent symmetry point-groups of these oligomers are the cyclic C n and the dihedral D n symmetries. The symmetric assembly of the oligomeric subunits leads to various advantages over asymmetric structure or monomeric form. These include coding efficiency and reduction of synthetic errors, cooperative regulation, increase in stability and formation of lower-energy structures, and minimization of excessive aggregation 2-7. Interestingly, despite these many functional advantages of the symmetric packing, the vast majority of protein oligomers are only nearly symmetric 2,4-6,8-11 , that is, although many oligomeric proteins are classified as 'symmetric' , there are conformational differences between the sequence-identical subunits 2,11. Understanding the origin and role of the asymmetry, is critical for understanding protein functions. In a recent review, Goodsell highlighted the issues around the near symmetry of biological functions in general, and proteins in particular, and pointed to evolutionary processes as lead to symmetry at some degree 1. The distortion from perfect symmetry of proteins is related to several issues, among them are functionality of the protein, thermodynamic considerations, such as enthalpy, entropy and the constant motion of the protein, the asymmetric environment that surrounds the protein, the mechanism of oligomerization, and even experimental conditions 1,9,11-14. Symmetric proteins and their imperfection, have been an ongoing research and some recent studies include global motion patterns of symmetric proteins 15 , how symmetry can compound the effect of point mutations and trigger uncontrolled self-assembly into high-order structures 16 , and how ...

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“…These measures quantify the degree of symmetry and the degree of chirality by determining the distance of a given molecular structure to its nearest symmetric (or achiral) form, on a continuous, normalized scale. Since their original developments these measures have been proven useful for various studies of reaction paths, , catalytic processes, , physical and chemical changes, − and more. − …”

Section: Introductionmentioning

confidence: 99%

Head to Tail Distortion Wave Characterizes the Enantiomerization of Helicenes

Kaspi-Kaneti

Barroso²,

Merino³

et al. 2020

J. Org. Chem.

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A fresh look on helicenes’ enantiomerization process with a focus on ring conformation reveals that it can be described as a step-by-step mechanism in which maximal distortion is consecutively transferred along the helicene skeleton, head to tail. Density functional theory methods were used to compute the enantiomerization pathway, and continuous symmetry measures were applied to quantify the distortion of even-number helicenes with 8–14 rings. Our findings show that the distortion wave is additivethe process always starts from one edge of the helicene and progresses along the rings until the other edge is reached. As more rings are added to the helicene, extra steps are appended to the distortion wave. Implications of this fundamental process are discussed in light of similar natural phenomena from polymer dynamics to snake locomotion.

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Twisted and Bent Out of Shape: Symmetry and Chirality Analysis of Substituted Ferrocenes

Cited by 11 publications

References 45 publications

1,1′-Dicarbodiimidoferrocenes: Synthesis, Characterization, and Group IV 1,1′-Bisguanidinateferrocene Complexes

1,1′-Dicarbodiimidoferrocenes: Synthesis, Characterization, and Group IV 1,1′-Bisguanidinateferrocene Complexes

The near-symmetry of protein oligomers: NMR-derived structures

Head to Tail Distortion Wave Characterizes the Enantiomerization of Helicenes

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