Picolinamide Complexes Research Articles

Rhodium(III)-Picolinamide Complexes Act as Anticancer and Antimetastasis Agents via Inducing Apoptosis and Autophagy.

As a continuation of our endeavors in discovering metal-based drugs with cytotoxic and antimetastatic activities, herein, we reported the syntheses of 11 new rhodium(III)-picolinamide complexes and the exploration of their potential anticancer activities. These Rh(III) complexes showed high antiproliferative activity against the tested cancer cell lines in vitro. The mechanism study indicated that Rh1 ([Rh(3a)(CH3CN)Cl2]) and Rh2 ([Rh(3b)(CH3CN)Cl2]) inhibited cell proliferation by multiple modes of action via cell cycle arrest, apoptosis, and autophagy and inhibited cell metastasis via FAK-regulated integrin β1-mediated suppression of EGFR expression. Furthermore, Rh1 and Rh2 significantly inhibited bladder cancer growth and breast cancer metastasis in a xenograft model. These rhodium(III) complexes could be developed as potential anticancer agents with antitumor growth and antimetastasis activity.

Highly efficient hydrogenation of furfural to valuable products catalysed by Rh (III), Pd (II), Ni (II), Fe (II) and Ru (II) half‐sandwich picolinamide and the SBA‐15 supported molecular complexes as pre‐catalysts

Novel palladium, rhodium, iron, ruthenium and nickel half‐sandwich picolinamide complexes have been prepared and characterised in detail using high‐resolution electrospray ionisation mass spectrometry (HR‐ESI‐MS), multi‐dimensional nuclear magnetic resonance spectroscopy, elemental analysis (EA), Fourier transform‐infrared spectroscopy (FT‐IR), and single crystal X‐ray diffraction (SCXRD). All the systems proved to be active with good catalytic performance for the hydrogenation of furfural. Among the pre‐catalyst,C2(Rh metal centre) displayed complete conversion (100%). Pre‐catalystC5(Ru metal centre) also resulted in excellent selectivity to EL (51%) and FA (49%). All the pre‐catalysts with early transition metal centres (Ni, Fe) gave selectivity towards FA (100%) under optimal conditions. Possible pathways for the formation of catalytically active have been proposed based on in situ NMR studies obtained usingC2. Successful modification of molecular complexes (C2andC3) on SBA‐15 resulted in supported molecular complexes (C2@SBA‐15andC3@SBA‐15). Furthermore, the supported molecular catalysts were characterised using inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), Fourier‐transform infrared spectroscopy (FT‐IR), powder X‐ray diffraction (PXRD), BET surface area, selected area electron diffraction (SAED), X‐ray photoelectron spectroscopy (XPS) and high‐resolution transmission electron microscopy (HR‐TEM). The supported molecular complexC2@SBA‐15was recycled five times (with consistent activity and selectivity).

The role of anion in supramolecular aggregation and energetic properties in a series of Cd picolinamide complexes

A novel group of energetic compounds, known as energetic coordination polymers (ECPs), can be rationally designed by introducing of highly energetic ions like ClO4-, N3–, NO3– and NO2– into a polymeric framework. Herein we report the preparation of four novel cadmium(II) complexes with picolinamide (pia) as ligand and different ions: [Cd(pia)3](ClO4)2·2H2O (1), [Cd(NO3)(ac)(pia)2] (2), [Cd(NO2)2(pia)2] (3), [Cd2(μ1,1-N3)4(pia)2]n [Cd(μ1,1-N3)2(pia)]n (4). The presence of different anions from starting Cd(II) salts caused the formation of discrete coordination compounds(1, 2 and 3), and coordination polymer (4). In 2, 3 and 4 anions are coordinated to Cd(II), while in 1 perchlorate anions act as a counterion. The molecular and crystal structure analysis has shown that in all compounds pia acts as N,O-chelator in various coordination arrangements depending on the present anion (1, 2 and 4 - distorted octahedral, 3- distorted square antiprismatic). In the crystal structures, the dominant mode of intermolecular interaction is a strong head−to−head amide hydrogen bond, with exception of 1. Structural analysis of herein-reported compounds and previously described Cd(pia)A (A – anion) compounds has shown that bulky tetrahedral anions (ClO4- and SO42-) inhibit the formation of the strong head−to−head amide hydrogen bonds. The investigations of energetic properties and sensitivity indicate a possible application of compound 4 as a secondary explosive material with energetic properties like those of LA (lead azide), mercury fulminate, or ammonium nitrate.

The Role of Anion in Supramolecular Aggregation and Energetic Properties in a Series of Cd Picolinamide Complexes

The Role of Anion in Supramolecular Aggregation and Energetic Properties in a Series of Cd Picolinamide Complexes

Structural and electrochemical properties of two novel CdX2 (X = Br, I) picolinamide complexes

Two novel discrete cadmium(II) complexes, namely [CdBr2(pia)2] (1) and [CdI2(pia)2] (2) were prepared by reactions of aqueous solutions of CdX2 (X = Br, I) salts with picolinamide (pia) in the 2:1 ligand to metal stoichiometric ratio. Both compounds were characterized by elemental analysis, IR-spectroscopy, TG/DSC analyses and electrochemical methods. The electrochemical characteristics of both ligand (pia) and prepared complexes were studied by cyclic and (cyclic) square-wave voltammetry, on a static mercury drop electrode (SMDE), in aqueous media over a wide pH range. The molecular and crystal structure of the compounds was determined by the single crystal X-ray diffraction method. X-ray structure analysis of 1 and 2 have shown that the compounds are isostructural with minor differences in the bond angles of the coordination sphere. In both compounds the Cd(II) ion is coordinated by two halide atoms and two mutually orthogonal picolinamide ligands that act as N,O-chelators in a distorted octahedral arrangement. In the crystal structure, the molecules of 1 and 2 are primarily linked via strong head–to–head amide hydrogen bond interactions forming dimers. In 1 the adjacent dimers are connected via NH⋯Br hydrogen bonds and offset face to face π⋯π interactions that involve pyridine rings, while in the structure of 2, the dimers are connected via CH⋯O, CH⋯N and NH⋯I hydrogen bonds into the final 3D structure. The intermolecular interactions in both crystal structures were further studied by Hirshfeld surface analysis. Electrochemical analysis of 2-picolinamide indicates the irreversible nature of its electro-reduction reaction on SMDE at pH 2. To provide better insight into the redox mechanism and electrokinetic properties of 2-picolinamide, the study of the effect of signal frequency on CSWV response was carried out, too. The electrochemical reduction of complex 2 involves two electron transfer reactions at −0.55 V and −0.83 V, indicating two redox active centers in the molecule, while complex 1 appears to be apparently electro-inactive in the studied potential range.

Catalytic Oxidation of Cyclopentene by O2 over Pd(II)-SBA-15 Complexes

Novel catalysts with Pd(II)-picolinamide complexes anchored into the channels of mesoporous material SBA-15 were prepared for chemical transformation of cyclopentene, and characterized in details. Spectra of 29Si NMR, 13C NMR and XPS revealed the organic ligands were grafted into the SBA-15 and Pd(II) complexes formed. Spacial diversity of the complexes, especially distances from –C=O to N on pyridyl cycles, may influence electronic distribution of conjugated system and further the catalytic activity. With the help of the newly synthesized catalytic materials, a new heterogeneous oxidation system was developed for selective catalytic transformation of cyclopentene to cyclopentanone with molecular oxygen as the sole oxidant. Analytic results of the reaction mixtures indicated that all catalysts exhibited high activity, while the cat.1 and cat.2 with 2-pyridinecarbonyl or 3-pyridinecarbonyl on the ligands gave better yields of cyclopentanone. 96.2% conversion of cyclopentene and 76.3% yied of cyclopentanone were achieved over the catalyst cat.2 under the conditions of 0.7 MPa O2, 323 K and 6 h reaction. In addition, the catalysts were also appealing for easy separation and recyclable property. A new heterogeneous reaction system was developed for the catalytic oxidation of cyclopentene to cyclopentanone by molecular oxygen over novel catalysts. The synthesized catalysts are comprised of Pd(II)-picolinamide complexes anchored into the channels of SBA-15. The new system was efficient for the mentioned reaction, and the catalysts were reusable.

Macrocylic Picolinamide Complexes and their Catalytic Reactivity in Allylic Oxidation

This paper describes the synthesis, characterization and catalytic activities of three closed-loop picolinamide complexes. They were prepared by Mn(II), Cu(II), Co(II) acetate and macrocylic ligand (L), which was formed by the condensation between 2,6-pyridinedicarboxylic acid chloride and 2,6-diaminopyridine. These complexes have been characterized by XRD, 1H NMR, IR, UV-vis DRS, Element analysis and TGA. Their catalytic activities in allylic oxidation of cyclohexene and isophorone with molecular oxygen as primary terminal oxidant were investigated for the first time. The influences of reaction temperature, the amount of catalyst and reaction time on the oxidation of cyclohexene by Co-L were also investigated. The results show that the Co-L can be obtained optimum catalytic efficiency, giving 58.2% conversion of cyclohexene and maximum selectivity of 83.4% for 2-cyclohexene-1-one; 15.4% conversion of isophorone and 46.2% selectivity of ketoisophorone. The heterogeneous catalysts can be easily separated for reuse at least three times without any significant change in selectivity. Keywords: Allylic oxidation, cyclohexene, macrocylic picolinamide, metal organic complexes, molecular oxygen, α-isophorone.

Synthesis, crystal structures and luminescence properties of europium and terbium picolinamide complexes

Abstract The novel coordination structures of europium and terbium chloride-picolinamide complexes (EuCl3·(C6H6N2O)2·5H2O, Eu-pa and TbCl3·(C6H6N2O)2·5H2O, Tb-pa) are reported. The crystal structures in the solid state are characterized by X-ray single crystal diffraction, FTIR, Raman, FIR, THz and luminescence spectroscopy. In the crystal structures, the pyridyl nitrogen and carbonyl oxygen atoms in picolinamide are coordinated to the metal ions to form a five-membered ring structure. The experimental results indicate the similar coordination structures of Eu and Tb-pa complexes and the changes of hydrogen bonds and conformation of the ligands induced by complexation. The results provide models for the coordination structures of lanthanide ions with ligands having amide groups.

Rhodium, Iridium, and Ruthenium Half-Sandwich Picolinamide Complexes as Anticancer Agents

Novel rhodium, iridium, and ruthenium half-sandwich complexes containing (N,N)-bound picolinamide ligands have been prepared for use as anticancer agents. The complexes show promising cytotoxicities, with the presence, position, and number of halides having a significant effect on the corresponding IC50 values. One ruthenium complex was found to be more cytotoxic than cisplatin on HT-29 and MCF-7 cells after 5 days and 1 h, respectively, and it remains active with MCF-7 cells even under hypoxic conditions, making it a promising candidate for in vivo studies.

The coordination of lanthanide ions with picolinamide. The influence of different anions

Four kinds of structures varied with different rare earth ions and anions have been observed for lanthanide–picolinamide complexes.

Structural study of picolinamide complexes of Ni(II), Zn(II), Cd(II), and Hg(II) nitrates in solid state and solution

Three picolinamide complexes of nickel(II) (1), zinc(II) (2), and cadmium(II) (3) have been prepared and their solid state structures were determined by single-crystal X-ray diffraction analysis. Their structures in DMSO solutions as well as the structure of similar mercury(II) complex, [Hg(NO3)(pia)2](NO3) (4), have been elucidated by 1H and 13C NMR spectra. The picolinamide is bound through the N,O-donors in all four complexes in solid state, but only in 4 it is in solution state. In nickel (1), zinc (2), and cadmium (3) complexes the pia-N coordination in solution is suggested. The X-ray analysis revealed that isomorphous nickel (1) and zinc (2) crystal structures comprise the centrosymmetrical trans-[M(H2O)2(pia)2]2+ (M = Ni, Zn; pia = picolinamide) and nitrate. The crystal lattices also contain two non-coordinated H2O molecules. In 3, each cadmium(II) is N,O-chelated by two cis-oriented pia ligands, while remaining coordination sites of the capped pentagonal bipyramid are occupied by three oxygen atoms from two nitrates. Crystal structures are dominated by O/N/C–H···O hydrogen bonds. The carboxamide moieties in 1 and 2 do not form any head-to-head or catemeric supramolecular synthons, but participate in the formation of (12) motifs with solely the amide nitrogen atoms as double hydrogen bond donors. In 3, neighboring molecules are linked into head-to-head amide dimers. The biological effect of picolinamide and [Zn(pia)2(H2O)2](NO3)2 on ingestion and intracellular microbicidal capacities of human peripheral blood phagocytes was also assessed.

N-(Aryl)picolinamide complexes of rhodium · Synthesis, structure and, spectral and electrochemical properties

N-(Aryl)picolinamide complexes of rhodium · Synthesis, structure and, spectral and electrochemical properties

Impact of metal coordination on amide synthons in picolinamide complexes

Impact of metal coordination on amide synthons in picolinamide complexes

New chromium(III)–picolinamide complexes. Kinetics and mechanism of picolinamide liberation in HClO4 solutions

Two new chromium(III) complexes with picolinamide (pica) and oxalates, [Cr(C2O4)2(N,N′-pica)]2− and [Cr(C2O4)2(N,O-pica)]−, were obtained and the kinetics of their aquation in HClO4 solutions were studied. The aquation leads to pica liberation and proceeds in two stages: (i) the chelate-ring opening at the Cr–amide bond and (ii) the Cr–N-pyridine bond breaking, which gives free pica and cis-[Cr(C2O4)2(H2O2)2]−. In the case of N,N′-bonded pica the kinetics of both stages was determined and in the case of the N,O-bonded pica only the second stage was investigated. The following rate laws were established: (kobs)1 = k0 + k1Q1[H+] and (kobs)2 = k2Q2[H+], where k0 and k1 are the rate constants of the chelate-ring opening in the unprotonated and protonated starting complex, and k2 is the rate constant of the pica liberation from the protonated intermediate. Kinetic parameters are calculated and the aquation mechanism is discussed.

Syntheses, Spectral and Thermal Studies, and Crystal Structure of 1,10-Phenanthroline and Picolinamide Complexes of Cobalt(II) Squarate

Abstract Preparations, crystal structures, thermal properties, IR and UV/vis spectroscopic studies and magnetic moments of tris(1,10-phenanthroline)cobalt(II) squarate octahydrate, [Co(phen)3]sq ・ 8H2O (1) and diaquabis(picolinamide)cobalt(II) squarate, [Co(H2O)2(pia)2]sq (2) are described. 1 crystallizes in the monoclinic system, space group P21/c, with a = 10.9832(5), b = 21.4569(12), c = 17.0649(7) Å , β = 98.159(3)° and Z = 8, while 2 crystallizes in the triclinic system, space group P1̅, with a =6.9624(9), b =7.9224(11), c =8.0501(11)Å ,α =107.404°, β =93.340(11)°, γ =93.266° and Z = 1. Both 1 and 2 have slightly distorted octahedral coordination geometry, involving six N atoms from bidentately chelating phen ligands and trans-[CoN2O4] coordination geometry, in which the Co atom is located at a center of symmetry. There are significant hydrogen-bonding interactions in the structure of 1. The squarate dianions are linked to the eight solvent water molecules by means of hydrogen-bonding interactions. Moreover, there are links between the complex cation and the squarate dianion via C-H···O hydrogen bonds. These interactions hold the crystal structure of 1 in a three-dimensional network, while O-H···O, N-H···O, weak π ···π and π ··· ring interactions lead to a three-dimensional crystal structure for 2. The thermal decomposition pathways of 1 and 2 have been investigated by the help of thermal analyses data (TG and DTA).

Lanthanide complexes with picolinamide

The preparation of picolinamide complexes with lanthanide nitrates, thiocyanates and perchlorates is reported. I.R. spectral data show picolinamide acting as bidentate ligand through ring nitrogen and carbonyl oxygen. The molar conductivity values in acetonitrile indicate that the nitrate and thiocyanate complexes are non-electrolytes and the perchlorate 1:3 electrolytes. A variation in intensity of the hypersensitive transition 4I 9 2 → 4G 5 2 in Nd 3+ complexes has been observed on changing the anionic group. The nephelauxetic effect has been evaluated from the parameter β.