ThemetaandparaOH Substitution Effect onC‐Phenyl‐Nitrilimine Bond‐Shift Isomers

Ferreira, Gil A.; Nunes, Cláudio M.; Jesus, A. J. Lopes; Fausto, Rui

doi:10.1002/ejoc.202300310

Cited by 3 publications

(1 citation statement)

References 60 publications

(125 reference statements)

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“…[1][2][3][4][5][6][7][8][9] Nitrile ylides, as other 1,3-dipolar species, commonly exist as a single minimum on their potential energy surfaces (PES), characterized by a structure that is better described by propargylic and/or allenic resonance form(s) (Scheme 1). [10][11][12][13][14][15] For the parent nitrile ylide molecule, MP2/6-311 + + G(d,p) and B3LYP/6-311 + + G(d,p) computations predict an almost linear CNC framework, together with a strongly bent carbon-C3 and a nearly perpendicular orientation between the two terminal (CH and CH 2 ) groups. [16] These structural features suggest that this species adopts an allenic-type structure.…”

Section: Introductionmentioning

confidence: 99%

On the Carbenic Nature of Nitrile Ylides: Experimental and Computational Characterization of Hydroxy and Amino Nitrile Ylides

Nunes,

Lopes Jesus,

Rosado

et al. 2023

Eur J Org Chem

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Nitrile ylides are 1,3‐dipolar species with structures that are commonly described by propargylic and/or allenic resonance forms. Nevertheless, certain nitrile ylides exhibit a tendency to form dimers, suggesting the existence of structures characterized by an important carbenic contribution. To address the nitrile ylide carbenic nature, here we investigate two derivatives with OH and NH2 electron‐donating substituents. These nitrile ylides were generated in cryogenic matrices by UV‐irradiation of 3‐hydroxy‐ and 3‐amino‐isoxazole precursors and were found to photoisomerize to the corresponding oxazoles. The IR spectral characterization of the photogenerated nitrile ylides reveals the absence of the characteristic strong νas(CNC) absorption, which is associated with allenic and propargylic type structures. Computed geometries for the two experimentally investigated nitrile ylides and for analogues with different substituents at C3 and C1, together with NBO and NRT electronic structure analyses, performed at the CCSD(T) level of theory, reveal substantial carbenic character exclusively for nitrile ylides bearing OH and NH2 substituents at C3. As a whole, the results shed light on the factors determining the structural features of nitrile ylides, which play a major role in defining the reactivity of these important elusive compounds.

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Section: Introductionmentioning

confidence: 99%

On the Carbenic Nature of Nitrile Ylides: Experimental and Computational Characterization of Hydroxy and Amino Nitrile Ylides

Nunes,

Lopes Jesus,

Rosado

et al. 2023

Eur J Org Chem

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A New Azide-Bridged Polymeric Manganese (III) Schiff Base Complex with an Allylamine-Derived Ligand: Structural Characterization and Activity Spectra

Talebi,

Salehi,

Jesus

et al. 2024

Inorganics

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This paper reports the synthesis and structural characterization of a novel azide-bridged polymeric manganese (III) Schiff base complex, using 2-((allylimino)methyl)-6-ethoxyphenol as a ligand. The crystal structure of the synthesized compound, elucidated by single-crystal X-ray diffraction analysis, indicates that it crystallizes in the monoclinic space group P21/c. The complex is found to display an octahedral geometry in which the central manganese Mn(III) coordinates with two bidentate donor Schiff base ligands via oxygen and nitrogen atoms. In addition, the metallic centers are linked together to form a one-dimensional chain bridged by end-to-end azide ligands. To offer a more thorough characterization of the synthesized compound, the study incorporates experimental data from FT-IR, UV-Vis, and cyclic voltammetry, alongside computational results from Hirshfeld surface analysis and DFT calculations conducted for both the ligand and complex. The computational analyses provided valuable insights into the intrachain and interchain interactions within the crystal structure, clarified the conformational characteristics of the isolated ligand molecule, and aided in the interpretation of the experimental IR spectra. Furthermore, an assessment of the compound’s drug-like properties was conducted using activity spectra for substances (PASS) predictions, revealing potential pharmacological activities.

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Photochemical Generation and Characterization of C-Aminophenyl-Nitrilimines: Insights on Their Bond-Shift Isomers by Matrix-Isolation IR Spectroscopy and Density Functional Theory Calculations

Lopes Jesus,

Nunes,

Ferreira

et al. 2024

Molecules

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The intriguing ability of C-phenyl-nitrilimine to co-exist as allenic and propargylic bond-shift isomers motivated us to investigate how substituents in the phenyl ring influence this behavior. Building on our previous work on the meta- and para-OH substitution, here we extended this investigation to explore the effect of the NH2 substitution. For this purpose, C-(4-aminophenyl)- and C-(3-aminophenyl)-nitrilimines were photogenerated in an argon matrix at 15 K by narrowband UV-light irradiation (λ = 230 nm) of 5-(4-aminophenyl)- and 5-(3-aminophenyl)-tetrazole, respectively. The produced nitrilimines were further photoisomerized to carbodiimides via 1H-diazirines by irradiations at longer wavelengths (λ = 380 or 330 nm). Combining IR spectroscopic measurements and DFT calculations, it was found that the para-NH2-substituted nitrilimine exists as a single isomeric structure with a predominant allenic character. In contrast, the meta-NH2-substituted nitrilimine co-exists as two bond-shift isomers characterized by propargylic and allenic structures. To gain further understanding of the effects of phenyl substitution on the bond-shift isomerism of the nitrilimine fragment, we compared geometric and charge distribution data derived from theoretical calculations performed for C-phenyl-nitrilimine with those performed for the derivatives resulting from NH2 (electron-donating group) and NO2 (electron-withdrawing group) phenyl substitutions.

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ThemetaandparaOH Substitution Effect onC‐Phenyl‐Nitrilimine Bond‐Shift Isomers

Cited by 3 publications

References 60 publications

On the Carbenic Nature of Nitrile Ylides: Experimental and Computational Characterization of Hydroxy and Amino Nitrile Ylides

On the Carbenic Nature of Nitrile Ylides: Experimental and Computational Characterization of Hydroxy and Amino Nitrile Ylides

A New Azide-Bridged Polymeric Manganese (III) Schiff Base Complex with an Allylamine-Derived Ligand: Structural Characterization and Activity Spectra

Photochemical Generation and Characterization of C-Aminophenyl-Nitrilimines: Insights on Their Bond-Shift Isomers by Matrix-Isolation IR Spectroscopy and Density Functional Theory Calculations

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