Search results for "Theoretical"
showing 10 items of 11439 documents
Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {CuIIMnIICrIII} Complexes
2017
The self-assembly process between the heteroleptic [CrIII(phen)(CN)4]− and [CrIII(ampy)(CN)4]− metalloligands and the heterobimetallic {CuII(valpn)MnII}2+ tecton afforded two heterotrimetallic complexes of formula [{CuII(valpn)MnII(μ-NC)2CrIII(phen)(CN)2}2{(μ-NC)CrIII(phen)(CN)3}2]·2CH3CN (1) and {[CuII(valpn)MnII(μ-NC)2CrIII(ampy)(CN)2]2·2CH3CN}n (2) [phen = 1,10-phenanthroline, ampy = 2-aminomethylpyridine, and H2valpn = 1,3-propanedyilbis(2-iminomethylene-6-methoxyphenol)]. The crystal structure of 1 consists of neutral CuII2MnII2CrIII4 octanuclear units, where two [Cr(phen)(CN)4]− anions act as bis-monodentate ligands through cyanide groups toward two manganese(II) ions from two [CuII(v…
A two-dimensional coordination polymer constructed from binuclear copper(II) metalloligands and manganese(II) ions: Synthesis, crystal structure and …
2016
Abstract The self-assembly process between the binuclear [Cu2(HL)(L)]− complex and the manganese(II) ion affords a two-dimensional coordination polymer of formula [Mn{Cu2(HL)(L)}2(H2O)2]n (1) (H3L = 3-hydroxyiminomethylsalicylic acid) where parallel ladder-like motifs of defective double cubanes of bis(phenoxo)dicopper(II) units as rods and anti-syn carboxylato bridges as rungs act as ligands towards tetraaqua-manganese(II) entities through the deprotonated oxime groups. The topology of 1 is compared with the one of another compound, [Mn{Cu2(HL)(L)}2(H2O)4]·4H2O·2DMF (1′) which was obtained in different conditions by Okawa et al. (J. Chem. Soc., Dalton Trans. (2001) 3119). Magnetic suscepti…
Determining Factors for the Unfolding Pathway of Peptides, Peptoids, and Peptidic Foldamers.
2016
We present a study of the mechanical unfolding pathway of five different oligomers (α-peptide, β-peptide, δ-aromatic-peptides, α/γ-peptides, and β-peptoids), adopting stable helix conformations. Using force-probe molecular dynamics, we identify the determining structural factors for the unfolding pathways and reveal the interplay between the hydrogen bond strength and the backbone rigidity in the stabilization of their helix conformations. On the basis of their behavior, we classify the oligomers in four groups and deduce a set of rules for the prediction of the unfolding pathways of small foldamers.
Catalytic Asymmetric Reactions Involving the Seven-Membered Cyclic Imine Moieties Present in Dibenzo[b,f][1,4]oxazepines
2017
The dibenzo[b,f][1,4]oxazepine scaffold is a privileged structure in medicinal chemistry that displays a wide variety of biological and pharmacological activities. However, catalytic asymmetric methodologies for the synthesis of chiral dibenzo[b,f][1,4]oxazepine derivatives are scarce in the literature. This microreview presents an overview of enantioselective reactions in which these cyclic seven-membered imines are used as electrophiles, including their substrate scope, limitations and application to the synthesis of related compounds.
Conformational Control of Metallocene Backbone by Cyclopentadienyl Ring Substitution: a New Concept in Polyphosphane Ligands Evidenced by “Through-Sp…
2009
The present study deals with the conformational control of the metallocene backbone within ferrocenyl polyphosphane ligands and their performance in the highly topical palladium-catalyzed heteroaromatics arylation by direct C−H activation. New substituted cyclopentadienyl rings were synthesized, which allowed the assembling of original tri- and diphosphanes. The bulky cyclopentadienyl lithium salts diphenylphosphino-3-(triphenyl)methylcyclopentadienyllithium (4) and 1,2-bis(diphenylphosphino)-4-(triphenyl)methylcyclopentadienyllithium (5) were prepared in excellent yield. The assembling of these new hindered cyclopentadienyl salts (Cp) with other Cp fragments was performed in order to prepa…
Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling
2015
The oxidative treatment of (m)ethyl 2-aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C–C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems.
Substituent effect on the σ- and π-electron structure of the nitro group and the ring in meta- and para-substituted nitrobenzenes
2017
An application of quantum chemical modeling allowed us to investigate a substituent effect on a σ and π electron structure of a ring and the nitro group in a series of meta- and para-X-substituted nitrobenzene derivatives (X = NMe2, NHMe, NH2, OH, OMe, Me, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, and NO). The obtained pEDA and sEDA parameters (the π- and σ-electron structure characteristics of a given planar fragment of the system obtained by the summation of π- and σ-orbital occupancies, respectively) of the NO2 group and the benzene ring allowed us to reveal the impact of the substituents on their mutual relations as well as to analyze them from the viewpoint of substituent charact…
Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylat…
2016
The synthesis and magnetostructural characterization of [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](ClO4)13·(CH3)2CO)6·(solvate) (2) are reported. This compound is obtained as a secondary product during synthesis of the mononuclear complex [Fe(II)(bppCOOH)2](ClO4)2 (1). The single-crystal X-ray diffraction structure of 2 shows that it contains the nonanuclear cluster of the formula [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](13+), which is formed by a central Fe(III)3O core coordinated to six partially deprotonated [Fe(II)(bppCOOH)(bppCOO)](+) complexes. Raman spectroscopy studies on single crystals of 1 and 2 have been performed to elucidate the spin and oxidation states of iron …
Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans…
1999
Abstract New binuclear complexes of the type [(Ni(Medpt)NO3)2ox] (1) (Medpt=3,3′-diamino-N-methyl-dipropylamine, H2ox=oxalic acid), [(Ni(dach)2)2ox]NO3·2H2O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))2ox]X2·yH2O (X=NO3, y=2 2/3 (3); X=ClO4, y=0 (4)) and [(Zn(dach)2)2ox](ClO4)2·2H2O (5) have been prepared and characterized by IR and UV–Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N3O3 or N4O2) Ni(II) (compounds 1 or 2), five-coordinated (N3O2) Cu(II) (compounds 3 and 4) or six-coordinated (N4O2) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))2ox](NO3)2·2 2/3 H2O (3) has been determined by single-crystal X-…
Remote Control by π-Conjugation of the Emissive Properties of Fischer Carbene-BODIPY Dyads.
2016
The synthesis, structure, and complete characterization of mono- and bimetallic dyads joining Fischer carbene complexes and BODIPY chromophores are reported. In these organometallic species, the Fischer carbene complex is attached to the BODIPY moiety through a p-aminophenyl group linked at the C8 carbon atom of the BODIPY core. The photophysical properties, namely the corresponding UV/vis absorption and emission spectra of these new metal-carbene complexes, are analyzed and discussed. It is found that whereas the absorption of the considered dyads strongly resembles that of the parent 4-anilinyl-substituted BODIPY, the fluorescence emission is significantly reduced in these species, very l…