Structures Of Square-planar Complexes Research Articles

Synthesis, electronic structure and interaction of rhodium(I) and iridium(I) bisimine-acenaphthalene complexes with CO2

The bis(arylimino)acenaphthalene (BIAN) group of α-diimine compounds has shown promising electron sink behaviour and redox non-innocent activity as ligands to main group and transition metals. Here we present a series of rhodium(I) and iridium(I) complexes of BIAN derivatives with 2,6-diisopropylphenyl (DippBIAN, DB) and 2,4,6-trimethylphenyl (MesBIAN, MB), featuring various electron withdrawing and donating ancillary ligands. The crystal structures of square planar complexes 1b [RhMB(cod)]PF6, 1d [IrMB(cod)]PF6, 2a [RhDB(CO)2]PF6, 2b [RhMB(CO)2]PF6, 2c [IrDB(CO)2]PF6 and 3a [RhDB(CO)(PEt3)]PF6 are reported, as well as the square pyramidal structure of 4c [IrDB(cod)Cl]. The C-N and C-C bond lengths within the bisimine moiety for the structures of 2a and 4c suggest that the DippBIAN ligands are present in a reduced state, however, all other data from our multi-technique analyses correspond to results for neutral BIAN ligands. These contrasting results are indicative of the DippBIAN’s non-innocent behaviour, accepting additional electron density from the metal centre due to push–pull mechanism between the ancillary and BIAN ligands. The electrochemical study in non-coordinating solvent CH2Cl2 revealed that all complexes featured at least one reversible, ligand-centred reduction event at less negative potentials (above –1.0 V vs Ag/Ag+). In addition, preliminary results from our electrocatalytic CO2 reduction study has shown a promising interaction between CO2 and complex 3a, paving the way for exploring heterogeneous catalysis on these class of compounds

Synthesis of Palladium(II) Complexes via Michael Addition: Antiproliferative Effects through ROS-Mediated Mitochondrial Apoptosis and Docking with SARS-CoV-2.

Metal complexes have numerous applications in the current era, particularly in the field of pharmaceutical chemistry and catalysis. A novel synthetic approach for the same is always a beneficial addition to the literature. Henceforth, for the first time, we report the formation of three new Pd(II) complexes through the Michael addition pathway. Three chromone-based thiosemicarbazone ligands (SVSL1–SVSL3) and Pd(II) complexes (1–3) were synthesized and characterized by analytical and spectroscopic tools. The Michael addition pathway for the formation of complexes was confirmed by spectroscopic studies. Distorted square planar structure of complex 2 was confirmed by single-crystal X-ray diffraction. Complexes 1–3 were subjected to DNA- and BSA-binding studies. The complex with cyclohexyl substituent on the terminal N of thiosemicarbazone (3) showed the highest binding efficacy toward these biomolecules, which was further understood through molecular docking studies. The anticancer potential of these complexes was studied preliminarily by using MTT assay in cancer and normal cell lines along with the benchmark drugs (cisplatin, carboplatin, and gemcitabine). It was found that complex 3 was highly toxic toward MDA-MB-231 and AsPC-1 cancer cells with IC50 values of 0.5 and 0.9 μM, respectively, and was more efficient than the standard drugs. The programmed cell death mechanism of the complexes in MDA-MB-231 cancer cells was confirmed. Furthermore, the complexes induced apoptosis via ROS-mediated mitochondrial signaling pathway. Conveniently, all the complexes showed less toxicity (≥50 μM) against MCF-10a normal cell line. Molecular docking studies were performed with VEGFR2, EGFR, and SARS-CoV-2 main protease to illustrate the binding efficiency of the complexes with these receptors. To our surprise, binding potential of the complexes with SARS-CoV-2 main protease was higher than that with chloroquine and hydroxychloroquine.

Effect of 2‐Bromopyridine Ancillary Ligand in the Catalysis of Pd(II)‐NNN Pincer Complexes towards Suzuki‐Miyaura Cross‐Coupling Reaction

AbstractPd(II)‐NNN pincer complexes containing sterically hindered 2‐bromopyridine (sp2 hybridized N donor) as ancillary ligand have been synthesized in order to compare their catalytic efficiency with the reported analogous complexes containing acetonitrile (sp hybridized N donor) ancillary ligand. The complexes have been characterized by analytical and spectroscopic techniques. Single crystal XRD reveals distorted square planar structure of complex 1. These complexes have been investigated as catalysts for the Suzuki‐Miyaura cross‐coupling (SMC) reaction. The scope is extended using various substituted aromatic/aliphatic halides. The activity of the Pd(II)‐NNN pincer complexes bearing bulky 2‐bromopyridine ancillary ligand is not higher compared to that of the complexes with acetonitrile ancillary ligand, which shows superiority of acetonitrile ancillary ligand.

Molecular and electronic structure of square planar complexes [PdII(tbpy)(LIPN,O)]0, [PdII(tbpy)(LISQN,O)](PF6), and [PdII(tbpy)(LIBQN,O)](PF6)(BF4)·2CH2Cl2: an o-iminophenolato based ligand centered, three-membered redox series

Three Pd(II) complexes which are members of the same electron-transfer series have been synthesized. Refluxing of the reaction mixture containing equimolar amounts of PdCl(2), 2-(2-trifluoromethyl)anilino-4,6-di-tert-butylphenol (H(2)L(N,O)), 4,4'-di-tert-butyl-2,2'-dipyridyl ((t)bpy), and 3 equiv of triethylamine in MeOH under an argon atmosphere followed by exposure to air and addition of KPF(6) after cooling to room temperature yields reddish brown crystals of paramagnetic (S = 1/2) [Pd(L(N,O)(ISQ))((t)bpy)](PF6) (2). Reaction of 2 with one equiv of [CoCp2] in dry and degassed CH(2)Cl(2) using anaerobic conditions gives diamagnetic [Pd(L(N,O)(IP))((t)bpy)] (1), which is the one-electron reduced form of 2. One-electron oxidation of 2 in CH(2)Cl(2) under argon with one equiv of NOBF4 affords diamagnetic [Pd(L(N,O)(IBQ))((t)bpy)](PF6)(BF4).2CH(2)Cl(2) (3). Complexes 1, 2, and 3 constitute three members of the same electron-transfer series. They are ideally suited to distinctly distinguish the geometrical and spectroscopic features of the N,O-coordinated, closed-shell, diamagnetic o-iminophenolate (L(N,O)(IP))2-, the corresponding open-shell pi-radical o-iminobenzosemiquinonate (L(N,O)(ISQ))1-.(S(rad) = 1/2), and the closed-shell o-iminobenzoquinone (L(N,O)(IBQ))0 forms. All complexes were characterized by X-ray crystallography (100 K), cyclic voltammetry, EPR, and UV-vis spectroscopy. Complex 2 exhibits three reversible electron transfer waves in the cyclic voltammogram. Structural characterization of complex 3 reveals an interesting strong ion pairing between the BF4 anion and the complex dication with a short C-F distance of 2.7 A.