Aromatic N-donor Ligands Research Articles

Ortho-palladated complexes with aromatic N-donor ligands, synthesis, characterization, molecular structures, antibacterial and anticancer activity

Ortho-palladated complexes with aromatic N-donor ligands, synthesis, characterization, molecular structures, antibacterial and anticancer activity

Syntheses, structure, DNA docking and antimicrobial studies of copper(II) complexes with diethylenetriamine and N-bidentate ligands

A series of mononuclear heteroleptic copper(II) complexes with diethylenetriamine (DETA) and bidentate N-donor ligands, [Cu(DETA)(5,6-DMPhen)](ClO4)21, [Cu(DETA)(4,7-DMPhen)](ClO4)2, 2, [Cu(DETA)(3,4,7,8-TMPhen)](BPh4)2, 3, [Cu(DETA)(8-AQ)](ClO4)2, 4, [Cu(DETA)(2-AMP)](ClO4)2, 5, [Cu(DETA)(2-AEP)](ClO4)2, 6, [Cu(DETA)(1,2-DACH)](ClO4)2, 7 and [Cu(DETA)(1,3-DAP)](ClO4)2, 8, with biologically relevant N-donor ligands 5,6-dimethyl-1,10-phenanthroline (5,6-DMPhen), 4,7-dimethyl-1,10-phenanthroline (4,7-DMPhen), 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-TMPhen), 8-aminoquinoline (8-AQ), 2-aminomethylpyridine (2-AMP), 2-aminoethylpyridine (2-AEP), 1,2-diaminocyclohexane (1,2-DACH) and 1,3-diaminopropane (DAP) respectively. All the complexes (1–8) were structurally determined by a single-crystal X-ray diffraction technique and characterized by CHN, UV–Vis, FT-IR, and ESI-MS. X-ray analysis revealed that the geometry around the copper center in all complexes (1–8) is distorted trigonal bipyramidal. All complexes strongly bind with ct-DNA via groove/electrostatic interactions. Their binding with DNA was supported by UV–Vis and CD spectral studies. Docking studies revealed that copper(II) complexes containing aromatic N-donor ligands (5,6-DMPhen, 4,7-DMPhen, 3,4,7,8-TMPhen & 8-AQ) have a stronger binding affinity than complexes with aliphatic N-donor ligands (2-AMP, 2-AEP, 1,2-DACH & DAP) towards DNA. All complexes exhibited good antibacterial activity against American standard ATCC Escherichia coli (ATCC 25922) and clinically isolated Escherichia coli (E1) bacterial strains.

Mononuclear and polymeric zinc(II) β-diketonate complexes with aromatic N-donor ligands: Structural, spectral, thermal, theoretical and docking studies

Four new compounds, {[Zn(μ-DPP)(DBM)2].2MeOH}n (1), {[Zn(μ-Pyrazine)(DBM)2]}n (2), [Zn(PHEN)(DBM)2] (3) and [Zn(2,2′-BPY)(DBM)(CH3COO)] (4) (DPP: 1,3-di(4-pyridyl)propane, HDBM: dibenzoylmethanato, PHEN: 1,10-phenanthrolin, 2,2′-BPY: 2,2′-bipyridine), were prepared and identified by elemental analysis, FT-IR and 1H NMR spectroscopy and single-crystal X-ray diffraction. In addition, the thermal stability of the compounds was evaluated by thermogravimetric analysis (TGA and DTA). The complexes 1 and 2 form 1D coordination polymers whereas 3 and 4 adopt a mononuclear structure. In these structures, the zinc atoms have octahedral (1–3) and square-pyramidal (4) geometries. The charge distribution pattern of the complexes 3 and 4 and their ligands was studied by NBO analysis and their ability to interact with ten biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) is investigated by docking calculations.

Influence of the Fluorinated Aromatic Fragments on the Structures of the Cadmium and Zinc Carboxylate Complexes Using Pentafluorobenzoates and 2,3,4,5-Tetrafluorobenzoates as Examples

A series of the cadmium and zinc carboxylate complexes with anions of pentafluorobenzoic (HРfbz) and 2,3,4,5-tetrafluorobenzoic (HТfbz) acids and N-donor ligands (1,10-phenanthroline (Phen) and quinoline (Quin)), [Cd(Pfbz)2(Phen)]n (I), [Cd(Рfbz)2(Рhen)2]·2MeCN (II), [Zn(H2O)-(Рfbz)2(Рhen)] (III), [Zn2Cd(Рfbz)6(Рhen)2]⋅2C6H6 (IV), [Cd2(H2O)2(Tfbz)4(Рhen)2] (V), [Cd2-(H2O)2(Tfbz)4(Quin)2] (VI), and [Cd(Tfbz)2(Phen)2]⋅HTfbz (VII), is synthesized. The structures of new complexes I–VII are determined by X-ray diffraction analysis (CIF files CCDC nos. 1871300, 2005461, 2005462, 2005464, 2005466, 2005465, and 2005459, respectively). The majority of the synthesized compounds is typical of intramolecular stacking interactions between the coordinated molecules of the aromatic N-donor ligands and fluorinated substituents of the carboxylate anions. These interactions lead to the formation of unusual compounds, which are different in the cases of pentafluorobenzoates and tetrafluorobenzoates, in particular, coordination polymer I and binuclear complexes V and VI with coordinated water molecules. The synthesized zinc and cadmium compounds differ in structure and composition.

Targeted Synthesis of NIR Luminescent Rhenium Diimine cis,trans-[Re( )(CO)2 (L)2 ]n+ Complexes Containing N-Donor Axial Ligands: Photophysical, Electrochemical, and Theoretical Studies.

The combined action of ultraviolet irradiation and microwave heating onto acetonitrile solution of [Re( )(CO)3 (NCMe)]OTf ( =phenantroline and neocuproine) afforded cis,trans-Re( )(CO)2 (NCMe)2 ]+ acetonitrile derivatives. Substitution of relatively labile NCMe with a series of aromatic N-donor ligands (pyridine, pyrazine, 4,4'-bipyridine, N-methyl-4,4'-bipyridine) gave a novel family of the diimine cis,trans-[Re( )(CO)2 (L)2 ]+ complexes. Photophysical studies of the obtained compounds in solution revealed unusually high absorption across the visible region and NIR phosphorescence with emission band maxima ranging from 711 to 805 nm. The nature of emissive excited states was studied using DFT calculations to show dominant contribution of 3 MLCT (dπ(Re)→π*( )) character. Electrochemical (CV and DPV) studies of the monocationic diimine complexes revealed one reduction and one oxidation wave assigned to reduction of the diimine moiety and oxidation of the rhenium center, respectively.

Utilization of mixtures of aromatic N-donor ligands of different coordination ability for the solvothermal synthesis of thiostannate containing molecules.

Utilization of mixtures of differently coordinating aromatic N-donor ligands leads to the formation of the two new compounds {[Ni(phen)2]2Sn2S6}·4,4'-bipy·½H2O I and {[Ni(phen)2]2Sn2S6}·2,2'-bipy II that could be prepared under solvothermal conditions (4,4'-bipy = 4,4'-bipyridine, C10H8N2; phen = 1,10-phenanthroline, C12H8N2; 2,2'-bipy = 2,2'-bipyridine, C10H8N2). In the structures of both compounds Ni-S bond formation is observed which is highly unusual when only bidentate N-donor ligands are applied in the reaction mixture. The detailed analysis of the crystal structure indicates that the presence of 4,4'-bipy and 2,2'-bipy molecules are essential for the stabilization of the arrangement of the constituents. The main structural motif {[Ni(phen)2]2Sn2S6} is arranged generating off center parallel stacking of the phen ligands. The empty spaces between the {[Ni(phen)2]2Sn2S6} moieties are occupied by either 2,2'-bipy (I) or 4,4'-bipy (II) molecules which are oriented towards the phen ligands to form intermolecular π-π interactions.

EuIII-1-Naphthoate Complex with N-Donor Ligand as a New White Luminescent Single Molecular Material

Two novel antenna complexes of <TEX>$Eu^{III}$</TEX> with 1-naphthoic acid (NA) as primary ligand and two aromatic N-donor ligands namely N-hexyl-N-(pyridin-2-yl) pyridin-2-amine (1) and 4-((dipyridin-2-ylamino)methyl)benzoic acid (2) have been synthesized and characterized by various spectroscopic techniques. The room-temperature (298 K) photoluminescence spectrum of <TEX>$Eu^{III}$</TEX> complexes composed of typical line like emissions, assigned to transitions between the first excited state <TEX>$^5D_0$</TEX> to the <TEX>$^7F_J$</TEX> (J = 0-4), resulting in red emission along with the residual emission from the 1-naphthoic acid moiety in the blue region. The determined CIE color coordinate value for the complex 2 is (x = 0.36, y = 0.34), which is in white region.

Synthesis, characterization and antitumor activity study of some cyclometalated organoplatinum(II) complexes containing aromatic N-donor ligands

A general approach has been designed to synthesize some mononuclear and binuclear cyclometalated platinum(II) complexes, containing aromatic N-donor ligands with the presence of one Cl − trans to carbon. In this way, cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, C^N = N(1),C(2′)-chelated, deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was used as a precursor to react with imidazole derivatives (1-methylimidazole, 2a, imidazole, 2b,), monodentate pyridine derivatives (4-methylpyridine, 2c, pyridine, 2d,) and bidentate pyridine derivative (4,4′-bipyridine, 3 and 4,). Synthesized complexes were fully characterized by using multinuclear NMR spectroscopy ( 1H, 13C{ 1H} and 195Pt), correlation NMR spectroscopy ( 1H- 1H COSY, 13C{ 1H}- 1H Heteronuclear Multiple Quantum Correlation, HMQC, Heteronuclear Multiple Bond Correlation, HMBC, 15N- 1H HETCOR), elemental analysis, X-ray crystallography and ESI-Mass spectrometry. Antitumor effects of mononuclear cyclometalated platinum(II) complexes 2a, 2c, 2d and 3 were determined on Jurkat, K562, and Raji cell lines and results showed reasonable cytotoxicities.

MTO Schiff‐Base Complexes: Synthesis, Structures and Catalytic Applications in Olefin Epoxidation

Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallography, with the O(-) moiety binding to the Lewis acidic Re atom and the Re-bound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from (17)O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition.

Synthesis and Luminescent Properties of Novel Lanthanide(III) β-Diketone Complexes with Nitrogen p,p‘-Disubstituted Aromatic Ligands

Tris-beta-diketonate lanthanide(III) complexes (Ln = Eu, Er, Yb, Tb), of general formula [Ln(acac)3 L(m)], with chelating ligands such as 4,7-disubstituted-1,10-phenanthrolines and 4,4'-disubstituted-2,2'-bipyridines, have been synthesized and fully characterized. The inductive effects of the para-substituents on the aromatic N-donor ligands have been investigated both in the solid and in the solution states. Single-crystal X-ray structures have been determined for the diethyl 1,10-phenanthroline-4,7-dicarboxylate europium and 4,4'-dimethoxy-2,2'-bipyridine erbium derivatives, revealing a distorted square antiprismatic geometry around the lanthanide atom in both cases. The influence exerted by the p,p'-substituents with respect to the nitrogen coordinating atoms on the Ln-N bond distances is discussed comparing the geometrical parameters with those found for the crystal structures containing the fragments [Ln(III)(phen)] and [Ln(III)(bipy)] obtained from the Cambridge Structural Database. The influence exerted by the electron-attracting groups on the coordination ability of the ligands, that in some cases becomes lack of coordination of the lanthanide ions, has been also detected in solution where the loss of the ligand has been followed by UV-vis spectroscopy. Moreover, the use of relatively long alkoxy chains as substituents on the 1,10-phenanthroline ligand led to the formation of a promesogenic lanthanide complex, whose thermal behavior is encouraging for the synthesis of new lanthanide liquid-crystalline species.

Hydrogen-bonded networks through second-sphere coordination.

The reaction of 4, 7-phenanthroline (1) with aqueous transitionmetal complexes [Mn(H2O)6][NO3]2, [Co(H2O)6][NO3]2, [Ni(H2O)6[NO3]2, [Mn(H2O)6][ClO4]2, and [Co(H2O)6][ClO4]2 does not produce coordination complexes between these metal cations and the N-donor ligand as expected. Instead, supramolecular hydrogenbonded networks are formed between the nitrogen donor atoms of 4, 7-phenanthroline and the OH groups of coordinated water molecules: M-O-H...N interactions. This motif of second-sphere coordination for 1 can be exploited as a tool for crystal engineering. As a demonstration of the generality of this new interaction as a supramolecular building block, five X-ray crystal structures are reported that utilise this hydrogen bonding scheme; [Co(H2O)4(NO3)2].(1)2 (2a), [Co(MeCN)2(H2O)4][ClO4]2.(1)2 (2b), [Ni(H2O)4(NO3)2].(1)2 (3a), [Mn(H2O)4(NO3)2].(1)2 (4a), and [Mn(H2O)6][ClO4]2.(1)(4).4H2O (4b). Each network involves complete saturation of the hydrogen-bond donor sets between the aqua complex and 1 using primarily M-O-H...N(1) and M-O-H...O(anion), interactions. Thermogravimteric analysis shows these materials to have stabililities similar to coordination polymers involving metal-ligand bonds; this demonstrates that second-sphere hydrogen bonding has potential for the construction of polymeric metal-containing materials.

Using Simple Aquo Complexes and Sterically Hindered Aromatic N-Donor Ligands to Generate Hydrogen-Bonded Frameworks

4,7-Phenanthroline (L) acts as a hydrogen-bond acceptor in the compounds {[M(NO 3) 2(H 2O) 4].L 2} (M=Mn, Co, Ni, Zn) forming square-grid hydrogen-bonded structures which are linked into an α-Po three-dimensional structure via supplementary hydrogen bonding and π–π interactions.

Pt(II) complexes with different N-donor aromatic ligands for specific inhibition of telomerase

A number of cis-dichloroplatinum(II) derivatives containing aromatic N-donor ligands such as pyridine and/or 5-substituted isoquinolines have been synthesized and fully characterized, with particular use of Raman spectroscopy and mass spectrometry. These complexes have been tested for specific inhibition of telomerase, which could represent a selective target for cancer chemotherapy. The screening of such potential drugs has been performed by a biochemical assay on the isolated enzyme. It is noteworthy that the cis-[PtCl 2(pyridine)(5-SO 3H-isoquinoline)] compound exhibited remarkable telomerase inhibition at a concentration as low as 10 −7 M.

Crystals Containing Conformers: A Rare Case in Which a Solid Closely Reflects a Solution Equilibrium Mixture

The factors influencing the structural, energetic and dynamic chemistry of complexes with coordinated aromatic N-donor ligands (L) are not well understood. Complexes of the type cis,cis,cis-RuCl2(Me2SO)2(L1)(L2) with L1 = L2 and L1 ≠ L2 (L1 trans to Cl, L2 trans to Me2SO) have afforded highly informative results. Here we report studies on two such complexes. One complex provides a rare example of a compound in which the solid state closely reflects the solution state, both in the structure of species involved in a conformational equilibrium and in the position of that equilibrium. In effect, the components of a fluxional equilibrium in solution are trapped, almost unchanged, in the solid state. Specifically, the complex cis,cis,cis-RuCl2(Me2SO)2(3,5-lut)(1,2-Me2Im) (2) (L1 = 3,5-lut = 3,5-lutidine; L2 = 1,2-Me2Im = 1,2-dimethylimidazole) exists as two conformers (R1 and R2) in solution and in the solid state (ratio = 0.63(2):0.37(2)); these rotamers differ by a 180° rotation of 1,2-Me2Im about the Ru−N bo...