19198-87-9Relevant academic research and scientific papers
Evaluation of the metal-dependent cytotoxic behaviour of coordination compounds
Grau, Jordi,Renau, Cristina,Caballero, Ana B.,Caubet, Amparo,Pockaj, Marta,Lorenzo, Julia,Gamez, Patrick
, p. 4902 - 4908 (2018)
The [Cu(L)Cl2]2 and [Pt(L)Cl2] complexes were prepared from the simple Schiff-base ligand (E)-phenyl-N-((pyridin-2-yl)methylene)methanamine (L) and respectively, CuCl2 and cis-[PtCl2(DMSO)2]. DNA-interaction studies revealed that the copper complex most likely acts as a DNA cleaver whereas the platinum complex binds to the double helix. Remarkably, cell-viability experiments with HeLa, MCF7 and PC3 cells showed that [Cu(L)Cl2]2 is an efficient cytotoxic agent whereas [Pt(L)Cl2] is not toxic, illustrating the crucial role played by the nature of the metal ion in the corresponding biological activity.
Gas-phase synthesis and reactivity of Cu+-benzyne complexes
Chai, Yunfeng,Shen, Shanshan,Weng, Guofeng,Pan, Yuanjiang
, p. 11668 - 11671 (2014)
Cu+-benzyne complexes bearing bidentate nitrogen ligands were synthesized in the gas phase for the first time using electrospray ionization mass spectrometry. The addition reactivity of copper-stabilized benzyne with amines was studied in the ion trap analyzer. The structures of products were identified by comparing their MSn data with authentic compounds obtained from another generation route.
Molybdenum (VI) Complexes Containing Pyridylimine Ligands: Effect of the Imine Nitrogen Substituent in the Epoxidation Reaction
Martínez-Martínez, Daniel,Santiago, M. León,Toscano, Rubén A.,Amézquita-Valencia, Manuel
, p. 243 - 251 (2021)
A series of pyridylimine ligands with variations of the substituent at the imine nitrogen were synthesized and coordinated to the [MoCl2O2] core. The novel molecular structures of the complexes were fully characterized by 1H and 13C NMR, FT-IR, ESI, EA, and X-ray crystallography, and their catalytic activity was studied for the epoxidation of alkenes using tert-butyl hydroperoxide (TBHP) as the oxidant. The new complexes showed excellent catalytic activity and fine selectivity in the epoxidation reaction compared with similar homogeneous molybdenum complexes. The results demonstrated that there is a significant change in the catalytic performance, depending on the alkyl arm on the structure of the pyridilimine ligand. The catalytic results indicated that complex [MoCl2O2(L)] (L: N-(2-Pyridinylmethylene)-1-tert-butylimine) C5 is the best catalytic precursor in the epoxidation of cyclohexene (TON: 92920 and TOF: 30974 h?1).
Pyridine- A nd Quinoline-Derived Imines as N, N-Bidentate Directing Groups in Palladium versus Platinum C-H Bond Activation Reactions
Torralvo, Héctor,Albert, Joan,Ariza, Xavier,Font-Bardia, Mercè,Garcia, Jordi,Granell, Jaume,Martinez, Manuel
, p. 203 - 217 (2021/02/01)
The C-H activation by Pd(II) and Pt(II) compounds of a wide range of imines related to 2-pyridinecarboxaldehyde, ArCHaNCH2(CH2)nPh (Ar = 2-pyridinyl, 2-picolinyl, 2-quinolinyl, n = 0, 1), which can be useful for bond functionalization assisted by bidentate directing groups, has been studied. The results indicate that the presence of two methyl groups at the α-carbon, relative to the imine nitrogen atom, facilitates the metalation. The heterocyclic fragment of the chelating ligand also shows a relevant influence on the full process, the cyclometalated compounds being more easily formed for the 2-picolinyl than for the 2-quinolinyl derivatives, while for the 2-pyridinyl derivatives the reaction is less favored. These effects have been found to be determinant for both palladium and platinum compounds. The preparative results can be explained by a steric enhancement of the metalation process, the reaction being strongly favored when bulky substituents are located in the proximity (α-carbon) of the coordinating nitrogen atoms (with both palladium and platinum). Furthermore, surprisingly the formation of six-membered platinacycles is especially favored. The kinetico-mechanistic studies of the C-H activation reaction, on some equivalent Pd(II) and Pt(II) coordination complexes of the family, have shown that the nature of the d8 metal center plays a determinant role in the reactivity observed. In this respect, the Pt(II) square-planar center has been found to be much more involved in the energetics of the reaction than the Pd(II) equivalent. The full process can be seen as a mechanistic continuum that goes from an electrophilic substitution (Pd(II) centers) to an oxidative addition/reductive elimination sequence (Pt(II) centers). The observation is directly associated with the fact that the Pt(II) center is prone to the existence of oxidatively added Pt(IV) hydrido complexes.
Hydrogen-Bond Catalysis of Imine Exchange in Dynamic Covalent Systems
Schaufelberger, Fredrik,Seigel, Karolina,Ramstr?m, Olof
supporting information, p. 15581 - 15588 (2020/10/02)
The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
Synthesis, characterization, and antimicrobial studies of half-sandwich η6-toluene ruthenium complexes with N,N′-bidentate ligands
Gichumbi, Joel M.,Friedrich, Holger B.,Omondi, Bernard,Chenia, Hafizah Y.
, p. 1833 - 1847 (2020/08/05)
Nine new complexes [(η6-C6H5-CH3)RuLCl]+(PF6)ˉ (where L = N,N′-bidentate ligand; (C5H4NCH = N-Ar) where Ar = 4-methylphenyl (C20H20ClF6N2PRu, 1); 3,4-dimethylphenyl (C21H22ClF6N2PRu, 2); 2,4,6-trimethylphenyl (C21H24ClF6N2PRu, 3); 4-bromophenyl (C19H17ClBrF6N2PRu, 4); 2,5-dimethylphenyl (C21H22ClF6N2PRu, 5); 2-flourophenyl (C19H17ClF7N2PRu, 6), (4-methoxyphenyl)methylene (C21H22ClF6N2OPRu, 7); phenylmethylene (C20H20ClF6N2PRu, 8); and 3,5-dimethylphenyl (C21H22ClF6N2PRu, 9) were synthesized by reacting the corresponding N,N′-bidentate ligands with the ruthenium arene dimer in a 2:1 ratio. The compounds were fully characterized via 1H NMR and 13C NMR, IR, and UV-vis spectroscopy and elemental analyses. The molecular structures of representative complexes (1, 7, and 8) were established by single-crystal X-ray diffraction studies. In the molecular structures of the complexes, the ligands coordinate to the Ru(II) centers via the pyridine nitrogen atom and the imine N atom in a bidentate manner. The other coordination sites of the Ru(II) center are occupied by the tolyl system in an η6 manner resulting in geometry often referred to as “pseudo-octahedral piano-stool.” All compounds were evaluated for their in?vitro antibacterial activity by the disk diffusion method against a panel of Gram-negative and Gram-positive bacteria. The complexes showed promising bactericidal activity against methicillin-resistant Staphylococcus aureus ATCC 43300.
Improving C=N bond reductions with (Cyclopentadienone)iron complexes: Scope and limitations
Cettolin, Mattia,Bai, Xishan,Lübken, Dennis,Gatti, Marco,Facchini, Sofia Vailati,Piarulli, Umberto,Pignataro, Luca,Gennari, Cesare
supporting information, p. 647 - 654 (2018/10/24)
Herein, we broaden the application scope of (cyclo-pentadienone)iron complexes 1 in C=N bond reduction. The catalytic scope of pre-catalyst 1b, which is more active than the “Kn?lker complex” (1a) and other members of its family, has been expanded to the catalytic transfer hydrogenation (CTH) of a wider range of aldimines and ketimines, either pre-isolated or generated in situ. The kinetics of 1b-promoted CTH of ketimine S1 were assessed, showing a pseudo-first order profile, with TOF = 6.07 h–1 at 50 % conversion. Moreover, the chiral complex 1c and its analog 1d were employed in the enantioselective reduction of ketimines and reductive amination of ketones, giving fair to good yields and moderate enantioselectivity.
Time-Dependent Switching of Constitutional Dynamic Libraries and Networks from Kinetic to Thermodynamic Distributions
He, Meixia,Lehn, Jean-Marie
supporting information, p. 18560 - 18569 (2019/11/21)
The distribution of the constituents of a constitutional dynamic library (CDL) may undergo time-dependent changes as a function of the kinetics of the processes generating the CDL from its components. Thus, the constitutional dynamic network (CDN) representing the connections between the constituents changes from a kinetic distribution to the thermodynamic one as a function of time. We investigated the behavior of dynamic covalent libraries (DCLs) of four constituents generated by reversible formation of C═N bonds between four components, 2 aldehydes and 2 amino compounds, both in absence and in the presence of metal cations. The associated [2 × 2] networks underwent time-dependent changes from the initial kinetic distribution to the final thermodynamic one, involving an orthogonal switch from one diagonal to the other diagonal of the square [2 × 2] network leading to a very large change in distribution. The DCL constituents could be switched from kinetic products (imines) to thermodynamic products (oximes or acylhydrazones) based on the reactivities of the components and the thermodynamic stabilities of the constituents without addition of any external effector, solely on the basis of the intrinsic properties of the self-contained system. Such processes were achieved for purely organic DCLs/CDNs as well as for inorganic ones containing two metal cations, the latter changing from the silver(I) complex of an imine (kinetic product) to the zinc(II) complex of a hydrazone (thermodynamic product). The results bear relationship to out-of-equilibrium systems concerning kinetic behavior in adaptive chemistry.
Controlled isoprene polymerization mediated by iminopyridine-iron (II) acetylacetonate pre-catalysts
Zhao, Mengmeng,Wang, Liang,Mahmood, Qaiser,Jing, Chuyang,Zhu, Guangqian,Zhang, Xianhui,Wang, Xiaowu,Wang, Qinggang
, (2019/02/06)
A ligand controlled stereoselective polymerization of isoprene has been developed. A series of (aryl/alkyl)-iminopyridine iron (II) acetylacetonate complexes: (aryl?=?Ph Fe1; alkyl?=?CH2Ph Fe2, CH (Ph)2 Fe3, CH (Me)2 Fe4, C (Me)3 Fe5, C (Me)2CH2C(Me)3 Fe6), has been prepared in which steric and electronic substituents systematically modified to investigate their influences for isoprene polymerization. The molecular structure of representative complex Fe2 was confirmed by single crystal X-ray diffraction and, revealed a distorted octahedral geometry at iron center. On treatment with methylaluminoxane (MAO), Fe1–Fe6 displayed low (Fe5 & Fe6) to high activities (Fe1–Fe4) with quantitative monomer conversion (>99%) for isoprene polymerization producing polyisoprene of high molecular weight (up to 2.0?×?105?g/mol) and unimodal molecular weight distribution (1.4–3.3). Specifically, complex Fe2 (alkyl?=?CH2Ph) displayed the highest activity of 7.0?×?106?g (mol of Fe)?1?h?1 with 85% conversion of monomer over run time of 10?min at 25?°C. While, Fe6 catalyzed polyisoprene possessed high content of trans-1,4 unit (up to 87%). Furthermore, the influence of the reaction parameters and the nature of the ligands on the catalytic activities and microstructural properties of the polymer were investigated in detail.
Synthesis and characterization of aminopyridine iron(ii) chloride catalysts for isoprene polymerization: Sterically controlled monomer enchainment
Jing, Chuyang,Wang, Liang,Mahmood, Qaiser,Zhao, Mengmeng,Zhu, Guangqian,Zhang, Xianhui,Wang, Xiaowu,Wang, Qinggang
, p. 7862 - 7874 (2019/06/13)
In this study, a series of 2-R-6-(1-(alkylamino)methyl)pyridine-iron complexes [alkyl: (CPh3) Fe1H; (CHPh2) Fe2H; (CHPh2) Fe3Me; (CHMePh) Fe4H; (CH2Ph) Fe5H; (CHMe2) Fe6H; (C6H11) Fe7H; (CH2(4-OMe)Ph) Fe8H; (CH2(4-CF3)Ph) Fe9H; (CH2(2,4,6-Me3)Ph) Fe10H; (CH2Ph) Fe11Me] were synthesized and well characterized by ATR-IR spectroscopy, HRMS spectroscopy and elemental analysis. In addition, Fe3Me, Fe4H, Fe7H and Fe11Me were characterized by X-ray diffraction analysis: Fe3Me and Fe11Me adopted distorted tetrahedral geometries in the solid state while Fe4H and Fe7H were found in dimeric or polymeric forms respectively in which chlorides acted as bridging ligands. The catalytic capacities of these iron complexes were investigated for isoprene polymerization. Upon activation with a MAO cocatalyst, the catalytic activities of complexes varied as a function of the steric and electronic influences of substituents. In general, the catalysts bearing the least steric groups and electron-withdrawing groups exhibited relatively high activities. An outstanding activity of 190.6 × 104 g·mol-1·h-1 was obtained by Fe5H [CH2Ph]. Moreover, changes in the steric hindrance around the metal center showed a notable effect on the selectivity of monomer enchainment. In particular, most of the polymers obtained by these complexes bearing flexible frameworks were in favor of 3,4-enchainment.
