Heteroleptic europium complexes with β-diketones and trifluoroacetic acid

Europium complexes with β-diketones and trifluoroacetic acid were obtained and characterized using elemental analysis, IR spectroscopy, emission spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry. The europium complexes are more stable when fluorinated substituents in β-diketones are replaced by alkyl substituents. Both the ligands (β-diketone and trifluoroacetic acid) are coordinated in a bidentate fashion. The Stark splitting of the ⁷ F ₁ levels in the complexes obtained increases with an increase in the negative inductive effect of the substituents in β-diketones, which indicates the partially ionic character of the Eu-ligand bond.     

Iridium-catalyzed asymmetric hydrogenation of β-keto esters with f-amphox ligands

The iridium-catalyzed asymmetric hydrogenation of β-keto esters with chiral tridentate P,N,N-ligands (f-amphox) has been developed. Under the optimized conditions, a wide range of β-keto esters can be hydrogenated smoothly, affording the corresponding β-hydroxy esters in good to excellent enantioselectivities (up to 95% ee).     

Hydrothermal syntheses,structures, and properties of four metal–organic coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands

A series of four metal–organic frameworks, namely, [Cu(sdpa)_0.5(2,2′-bpy)]·H₂O (1), [Zn₂(sdpa)(2,2′-bpy)₂(H₂O)₂]·3H₂O (2), [Zn₂(sdpa)(4,4′-bpy)]·3H₂O (3), [Cd₂(sdpa)(4,4′-bpy)_1.5(H₂O)₂](4), have been hydro(solvo)thermally synthesized through the reaction of 2,3,2′,3′-sulfonyldiphthalic acid (H₄sdpa) with divalent copper, zinc and cadmium salts in the presence of ancillary nitrogen ligands (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complex 1 and 2 show metal–organic chain structure, and the adjacent chains are further linked by π?π and C–H?π interactions for 1 and hydrogen bonds and π?π interactions for 2 to form 3D supramolecular structure. In complex 3, two Zn1 and two Zn2 atoms appear alternately and are bridged by sdpa⁴⁻ anion ligands to form an infinite Zn-sdpa chain. Such chains are further linked together through 4,4′-bpy ligands in four orientations to form a robust 3D metal–organic network. In compound 4, a 3D Cd-sdpa metal–organic network is accomplished through sdpa⁴⁻ anion ligands, and further stabilized by 4,4′-bpy in six orientations. Their luminescence and thermal analysis have also been investigated.     

New mononuclear copper(II) complexes from β-diketone and β-keto ester N-donor heterocyclic ligands: structure,bioactivity, and molecular simulation studies

Four new mononuclear copper(II) complexes with methyl acetoacetate and benzoylacetone in the presence of 1,10-phenanthroline and 2,2′-bipyridine were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The molecular structures of complexes [Cu(MAA)(bpy)(ClO₄)] (1a), [Cu(bzac)(bpy)]ClO₄ (2a), [Cu(MAA)(phen)(ClO₄)] (1b) and [Cu(bzac)(phen)(ClO₄)] (2b) were determined by single crystal X-ray diffraction technique. 1a, 1b, and 2b are five coordinate with a distorted square pyramidal geometry and the structure of 2a consists of isolated [Cu(bzac)(bpy)]⁺ cations and perchlorate counter anions. The electrochemical studies of copper complexes in acetonitrile solution showed that Cu^II/Cu^I reduction processes are electrochemically irreversible. Cytotoxic activity of complexes was screened, including an MTT assay against gastric cancer cell line (MKN-45). The four Cu(II) complexes exhibited lethal effects against MKN-45 cell lines and the half maximal inhibitory concentration (IC₅₀) values obtained were much lower in comparison with 5-fluorouracil. In addition, MTT and migration studies revealed that benzoylacetone complexes are more active than complexes of methyl acetoacetate against the MKN-45 cancer cell lines. Docking simulations of Cu(II) complexes on DNA revealed that the most stable adducts with DNA bind in the minor groove. All complexes display a binding specificity to the A/T rich regions.     

The reaction of trifluoromethanesulfenyl chloride with enamines of β-keto carboxylic acid anilides

1-Morpholino-cyclopenten-2-carboxylic acid anilides react with CF₃SCl in molar ratio 1:2 to give products of the displacement of two hydrogen atoms at C-2 and C-5. The analogous reaction with enamines of cyclohexanono- and cycloheptanono- 2-carboxylic acid anilides and benzoylacetanilides proceeds in 1:1 molar ratios affording enamines and keto compounds.     

Transition-metal,organic solvent and base free α-hydroxylation of β-keto esters and β-keto amides with peroxides in water

Without employing any transition metal, organic solvent and base, a facile, economical and environmentally friendly strategy has been developed for the α-hydroxylation of β-keto esters and β-keto amides with peroxides via radical cross-coupling reaction in water under open-air conditions. This protocol allows a convenient access to various α-hydroxy-β-keto esters and α-hydroxy-β-keto amides with up to 92% yield (34 examples). Moreover, the reaction was successfully scaled up to gram quantity and mechanistic studies showed the radical pathway was involved in this hydroxylation.     

Reaction of CH acids with 2-arylidenecycloalkanones: Synthesis of β-keto acid anilide derivatives of naphthalene,indene, fluorene,and phenanthrene

Summary 2-Arylidene-cyclohexanone1, -cyclopentanone2, -1-indanone3 and-1-tetralone4 react with acetoacetanilide5 yielding 2-oxo-4-aryl-3-carboxylic acid anilides derivatives of naphthalene7, indene8, fluorene9 and phenanthrene10. Reaction of1 and3 with benzoylacetanilide6 yields the corresponding Michael adducts11 and12.

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Reaktion von CH-Säuren mit 2-Arylidencycloalkanonen. Synthese von -Ketosäureanilid-Derivaten von Naphthalin, Inden, Fluoren und Phenanthren

Zusammenfassung 2-Arylidencyclohexanone1, -cyclopentanone2, -1-indanone3 und -1-tetralone4 reagieren mit Acetoacetanilid5 unter Bildung von 2-Oxo-4-aryl-3-carbonsäureanilid-Derivaten von Naphthalin7, Inden8, Fluoren9 und Phenanthren10. Die Reaktion von1 und3 mit Benzoylacetanilid6 ergibt die entsprechenden Michael-Addukte11 und12.

     

Synthesis,characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Transition Metal Chemistry - Two copper(II) complexes with ligands derived from β-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were...     

New tetrahedral boron heterobicycles: Cyclocondensation of phenylboronic acid with β-keto butanoic acid N-acyl hydrazones

A series of 4-phenyl-2-aryl-8-methyl-6-oxo-7-phenylhydrazo-2H,4H,6H,7H,8H[1,3,4,2]-oxadiazaborolo[2,3-b][1,3,2]oxazaborines were prepared in high yields via the reaction of phenylboronic acid with various N-acylhydrazones of 3-keto-2-(2′-phenylhydrazono) butanoic acid in the presence of 4 Å molecular sieves. These derivatives represent a novel class of zwitterionic, tetrahedral boron heterocycles. Single crystal X-ray analysis of a representative boron containing product is reported.     

Novel heteroligated titanium complexes with fluorinated salicylaldiminato and β-enaminoketonato ligands: synthesis, characterization and catalytic behavior in vinyl addition polymerization of norbornene

A series of heteroligated (salicylaldiminato)(β-enaminoketonato)titanium complexes of the general formula [3-Bu(t)-2-OC(6)H(3)CH==N(C(6)F(5))][PhN==C(CF(3))CHC(R)O]TiCl(2) (3a: R==Ph, 3b: R==C(6)H(4)Ph(p), 3c: R==C(6)H(4)Ph(o), 3d: R = 1-naphthyl, 3e: R = C(6)H(4)F2(2,6), 3f: R = C(6)H(4)Cl2(2,5), 3g: R==C(6)F4(2,3,5,6)OMe(4)) were synthesized. The structure of complexes 3d, 3f-g were determined by single crystal X-ray diffraction analysis. The X-ray crystallographic analysis indicated these complexes adopted a distorted octahedral geometry around the titanium center. Upon activation with modified methylaluminoxane, complexes 3a-g exhibited moderate to good catalytic activity for norbornene (NB) vinyl addition polymerization, producing moderate molecular weight polynorbornenes under mild conditions. The introduction of electron-withdrawing groups can greatly enhance the catalytic activity. Significantly, the heteroligated titanium complexes displayed greatly improved activity for vinyl addition polymerization of NB compared to homoligated counterparts, which may stem from the suitable combinations of electronic and steric effects.     

Synthesis and luminescence-spectral properties of benzoheterocyclic β-diketones and their complexes with europium

In order to solve some environmental and biomedical problems, we synthesized fluorinated heterocyclic β-diketones and estimated the luminescence-spectral properties of these compounds complexes with the ions of rare-earth elements as the possible reagents for immunofluorescence analysis.     

NMR and luminescence spectroscopy study of the formation of mixed europium β-diketonate complexes with trifluoroacetic acid in nonaqueous solutions

The ligand substitution in Eu(AA)₃ · Phen-CDCl₃-TFA systems, where AA is acetylacetone, Phen is 1,10-phenanthroline, and TFA is trifluoroacetic acid was studied at various molar ratios (m) of competing ligands (m = TFA/AA) using NMR (¹H, ¹⁹F) and luminescence spectroscopy. The formation of mixed Eu(AA)₂(TFA) · Phen and Eu(AA)(TFA)₂ · Phen complexes in the resultant solutions was attested. The luminescence spectra were studied. The competitive capacity of TFA was ascertained to be higher than that of AA. Depending on the m value, the substitution of acido ligands was shown to occur successively according equations Eu(AA)₃ · Phen + (TFA) _n = Eu(AA)_{3 − n} (TFA) _n · Phen + (AA) _n (n = 1, 2, 3).     

Zirconium and hafnium amide, alkoxide, and pyrrolyl complexes manifesting with pyrrolyl-linked N-donor ligands: Syntheses, characterization, and ring opening polymerization of ε-caprolactone

A series of zirconium and hafnium alkoxide and amide complexes containing symmetrical tridentate pyrrolyl ligand, [C₄H₂NH(2,5-CH₂NMe₂)₂] have been synthesized conveniently by treatment of 2,6-di-tert-butylphenol, tert-butanol or pyrrole in pentane and their reactivity over ring opening polymerization of ε-caprolactone have been carried out. Reactions of [C₄H₂NH(2,5-CH₂NMe₂)₂] with M(NEt₂)₄ (M = Zr or Hf) originate [C₄H₂N(2,5-CH₂NMe₂)₂]M(NEt₂)₃ (1, M = Zr; 2, M = Hf). Furthermore, reactions of [C₄H₂N(2,5-CH₂NMe₂)₂]M(NEt₂)₃ with 2,6-di-tert-butylphenol, tert-butanol or pyrrole afford [C₄H₂N(2,5-CH₂NMe₂)₂]M(OC₆H₃-2,6-^tBu₂)(NEt₂)₂ (3, M = Zr; 4, M = Hf), [C₄H₂N(2,5-CH₂NMe₂)₂]M(O^tBu)₃ (5, M = Zr; 6, M = Hf) and [C₄H₂N(2,5-CH₂NMe₂)₂]M(C₄H₄N)₃ (7, M = Zr; 8, M = Hf), respectively, in satisfactory yield. All the complexes have been characterized by NMR spectra as well 3, 4 and 6 subjected to the X-ray diffraction analysis. Complexes 3-8 have been used as initiators for the ring-opening polymerization of ε-caprolactone and observed broad PDI values (1.84-2.75) representing multiple reactivity centers of these complexes.     

Molybdenum(VI) dioxo and oxo-imido complexes of fluorinated β-ketiminato ligands and their use in OAT reactions

Substitution of a methyl by a trifluoromethyl moiety in well-known β-ketimines afforded the ligands (Ar)NC(Me)CH(2)CO(CF(3)) (HL(H), Ar = C(6)H(5); HL(Me), A r= 2,6-Me(2)C(6)H(3); HL(iPr), Ar = 2,6-(i)Pr(2)C(6)H(3)). Subsequent complexation to the [MoO(2)](2+) core leads to the formation of novel complexes of general formula [MoO(2)(L(R))(2)] (R = H, 1; R = Me, 2; R = iPr, 3). For reasons of comparison the oxo-imido complex [MoO(N(t)Bu)(L(Me))(2)] (4) has also been synthesized. Complexes 1-4 were investigated in oxygen atom transfer (OAT) reactions using the substrate trimethylphosphine. The respective products after OAT, the reduced Mo(IV) complexes [MoO(PMe(3))(L(R))(2)] (R = H, 5; R = Me, 6; R = iPr, 7) and [Mo(N(t)Bu)(PMe(3))(L(Me))(2)] (8), were isolated. All complexes have been characterized by NMR spectroscopy, and 1-4 also by cyclic voltammetry. A positive shift of the Mo(VI)-Mo(V) reduction wave upon fluorination was observed. Furthermore, molecular structures of complexes 2, 4, 5, and 8 have been determined via single crystal X-ray diffraction analysis. Complex 8 represents a rare example of a Mo(IV) phosphino-imido complex. Kinetic measurements by UV-vis spectroscopy of the OAT reactions from complexes 1-4 to PMe(3) showed them to be more efficient than previously reported nonfluorinated ones, with ligand L' = (Ar)NC(Me)CH(2)CO(CH(3)) [MoO(2)(L')(2)] (9) and [MoO(N(t)Bu)(L')(2)] (10), respectively. Thermodynamic activation parameters ΔH(?) and ΔS(?) of the OAT reactions for complexes 2 and 4 have been determined. The activation enthalpy for the reaction employing 2 is significantly smaller (12.3 kJ/mol) compared to the reaction with the nonfluorinated complex 9 (60.8 kJ/mol). The change of the entropic term ΔS(?) is small. The reaction of the oxo-imido complex 4 to 8 revealed a significant electron-donating contribution of the imido substituent.     

pH-dependent syntheses and crystal structures, characterizations, and DFT calculations of complexes with 2,2′-biimidazole and terephthalic acid ligands

The divalent transition metal complexes [Zn(L)₂(H₂O)₂](Tere) (I), [Cd(L)₂(H₂O)₂](Tere]) (II) and [Cd(L)₂(HTere)₂] (III) (L = 2,2’-biimidazole, Tere = terephthalate) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectrum, thermal analysis and single-crystal X-ray diffraction analysis. Complexes II and III have the same starting materials but possess different frame-works and are prepared from H₂Biim and H₂Tere under hydrothermal conditions with different pH values. The crystal structures show I and II have the same coordination circumstances and are coordinated by two H₂O molecules and two neutral bidentate 2,2′-biimidazole ligands. The terephthalate acts as the counter anion. In contrast, complex III contains protonated carboxylate groups coordinated to the metal centre to give neutral species. Furthermore, based on the optimized structures, molecular frontier orbitals, Mulliken charges and IR spetra of complex I and III are investigated by density functional theory. Calculated results show that the energy gap (ΔE _L-H) between HOMO and LUMO of complex III is bigger than that of I. It is revealed that complex III is more stable, and this calculated estimation corresponds with experimental analysis of TGA curves.     

Synthesis and structure of new europium(ɪɪɪ) and terbium(ɪɪɪ) coordination polymers with trans-1,4-cyclohexanedicarboxylic acid

Russian Chemical Bulletin - Two new metal-organic frameworks of composition [Eu2(phen)2Cl2(chdc)2] ? 1.1DMF? ?0.7diox (1?1.1DMF?0.7diox, phen is 1,10-phenanthroline,...     

Structure-based design,synthesis and biological evaluation of β-glucuronidase inhibitors

Using structure-based virtual screening approach, a coumarin derivative (1) was identified as β-glucuronidase inhibitor. A focused library of coumarin derivatives was synthesized by eco-benign version of chemical reaction, and all synthetic compounds were characterized by using spectroscopy. These compounds were found to be inhibitor of β-glucuronidase with IC₅₀ values in a micromolar range. All synthetic compounds exhibited interesting inhibitory activity against β-glucuronidase, however, their potency varied substantially from IC₅₀ = 9.9–352.6 µM. Of twenty-one compounds, four exhibited a better inhibitory profile than the initial hit 1. Interestingly, compounds 1e, 1k, 1n and 1p exhibited more potency than the standard inhibitor with IC₅₀ values 34.2, 21.4, 11.7, and 9.9 µM, respectively. We further studied their dose responses and also checked our results by using detergent Triton ×-100. We found that our results are true and not affected by detergent.     

Efficient two-photon-sensitized luminescence of a novel europium(III) β-diketonate complex and application in biological imaging

A novel europium(III) β-diketonate complex exhibiting bright two-photon-sensitized luminescence is synthesized and applied as a two-photon-sensitized luminescent probe to stain DNA in live cells.     

Syntheses,crystal structures,and characterization of three metal–organic complexes with 2,2′-biphenyldicarboxylic acid and phenanthroline ligands

Three complexes constructed with 2,2′-biphenyldicarboxylic acid, multidentate nitrogen donors, and metal salts, {[Cd(2,2′-dpdc)(tppp)(H₂O)]₂?·?2H₂O} _n (1), {[Pb(2,2′-dpdc)(pyphen)]₂} _n (2), and {[Pb(2,2′-dpdc)(dppz)]} _n (3) (H₂dpdc = 2,2′-diphenyldicarboxylic acid; tppp = 4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol; pyphen?=?pyrazino[2,3-f]-[1,10]phenanthroline; and dppz = dipyrido[3,2-a:2′,3′-c]phenazine), are synthesized under hydrothermal conditions. These complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and photoluminescence. In 1, two 2,2′-dpdc ions bridge two Cd(II) ions to form an isolated cluster with Cd?···?Cd distance of 5.023(4)?Å. These clusters are further linked by intermolecular hydrogen bonds, yielding a 2-D supramolecular structure. Complex 2 contains two crystallographically independent Pb(II) ions in the asymmetric unit. Pb1 ions are bridged by 2,2′-dpdc anions to form a chain along the x-axis. Two Pb2 ions are coordinated by two 2,2′-dpdc anions and two pyphen ligands to form a cluster. These clusters are linked by π–π interactions to yield a 1-D supramolecular chain along the y-axis. In 3, neighboring Pb(II) atoms are bridged by 2,2′-dpdc anions to form a 1-D chain structure. Further, the chains are linked into a 3-D supramolecular network through aromatic π–π interactions.