Synthesis, Characterization, DNA Binding, and Photocleavage Activity of Oxorhenium (V) Complexes with α-Diimine and Quinoxaline Ligands

The complex [ReOCl3pq] (1) (where pq = 2-(2′pyridyl)quinoxaline) has been synthesized and fully characterized by UV-Vis, FTIR, 1 and 2D NMR, and cyclic voltammetry (CV). The DNA-binding properties of the complex 1 as well as of the compounds [ReOCl3bpy] (2), [ReOCl3phen] (3), and pq (4) were investigated by UV-spectrophotometric (melting curves), CV (cyclic voltammetry), and viscosity measurements. Experimental data suggest that complex 1 intercalates into the DNA base pairs. Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II. The mechanism of the DNA cleavage by complex 1 was also investigated

Synthesis, Characterization, DNA Binding, and Photocleavage Activity of Oxorhenium (V) Complexes with α-Diimine and Quinoxaline Ligands

The complex [ReOCl 3 pq] (1) (where pq = 2-(2 pyridyl)quinoxaline) has been synthesized and fully characterized by UV-Vis, FTIR, 1 and 2D NMR, and cyclic voltammetry (CV). The DNA-binding properties of the complex 1 as well as of the compounds [ReOCl 3 bpy] (2), [ReOCl 3 phen] (3), and pq (4) were investigated by UV-spectrophotometric (melting curves), CV (cyclic voltammetry), and viscosity measurements. Experimental data suggest that complex 1 intercalates into the DNA base pairs. Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II. The mechanism of the DNA cleavage by complex 1 was also investigated

Re(I) tricarbonyl complex of 1,10-phenanthroline-5,6-dione: DNA binding, cytotoxicity, antiinflammatory and anti-coagulant effects towards platelet activating factor

The complex fac-[Re(CO)3(phendione)Cl] (1) (where phendione = 1,10-phenanthroline-5,6-dione) has been synthesized and fully characterized by UV–visible, FTIR, and NMR techniques. The DNA binding properties of 1 are investigated by UV-spectrophotometric (melting curves), covalent binding assay, CV (cyclic voltammetry), circular dichroism (CD) and viscosity measurements. Experimental data indicate that 1 fits into the major groove without disrupting the helical structure of the B-DNA in contrast to the free phendione which intercalates within the base pairs of DNA. Upon irradiation, complex 1promotes the cleavage of plasmid pBR322 DNA from supercoiled form I to nicked form II via a proton coupled electron transfer mechanism. This comes as a result of experimental data in anaerobic/aerobic conditions and in the presence of DMSO. The biological activities of 1 and its precursors [Re(CO)5Cl] and phendione are tested towards a series of cancerous cell lines as glioblastoma (T98G), prostate cancer (PC3) and breast cancer (MCF-7) as well as platelet activating factor (PAF)-aggregation. Moreover, all the aforementioned compounds are tested for their ability to modulate PAF-basic metabolic enzyme activities in preparations of rabbit leukolytes. The in vitro experiments indicate that phendione has a better antitumor effect than cisplatin whereas [Re(CO)5Cl] is a better PAF inhibitor than both the phendione ligand and 1. Moreover, for the first time it is indicated that [Re(CO)5Cl], with a IC50 of 17 nM is comparable to the widely used PAF receptor antagonists, BN52021 and WEB2170 with IC50 of 30 and 20 nM, respectively, whereas 1 affects PAF-catabolism

Photocatalytic Hydrogen Evolution by tris-dithiolene tungsten complexes

Herein, we report on the homogeneous photocatalytic evolution of hydrogen by using as reductive catalysts the prismatic symmetric tris – dithiolene complexes of the tungsten, namely [W{S2C2(Ph)2}3] (1) and its monoanion [W{S2C2(Ph)2}3](TBA) (2). Complex 2 is fully characterized by elemental analysis, ESI-MS, IR, UV-Vis and fluorescence spectrophotometry as well as cyclic voltammetry. The photocatalytic system consists of [ReBr(CO)3(bpy)] as a photosensitizer, triethanolamine as a sacrificial electron donor and acetic acid as the proton source. Although the activity of the photocatalytic system is rather small (TON=18), it indicates that the homoleptic tris dithiolene complexes can act as proton reductive catalysts with their monoanion form to be more active in accordance with the findings for the bis - dithiolene complexes

Synthesis, spectroscopic properties and crystal structure of mononuclear tricarbonylrhenium(I) chloride complexes carrying 6-functionalised quinoxalines

Two quinoxaline derivatives pqCH3 and pqCl (where pq stands for 2-(2′-pyridyl)quinoxaline) were prepared by condensation of 2-acetyl pyridyl with 2-amino-4-methylphenylamine or 2-amino-4-chlorophenylamine, correspondingly and were studied spectroscopically and electrochemically, in correlation with the originally reported pq. Their novel corresponded complexes namely, fac-[Re(CO)3Cl(L)] (where L = pqCH3 2 and pqCl 3) were synthesized, characterized, studied and compared to Re(CO)3Clpq, 1. Complex 2 crystallizes in space group C2/c with a = 20.4476(17) Å, b = 15.4521(13) Å, c = 15.2887(13) Å, β = 126.1210(11)°, Z = 8 and V = 3902.0(6) Å3. The substitution of –H by –CH3 or –Cl at 6-position of pq has a minor electronic effect on the pyridyl ring of the ligands, but seems to influence the quinoxaline moiety enough to alter the spectroscopical and electrochemical features.We would like to thank the Special Research Account of University of Athens for partial financial support.Peer reviewe

Isolation, X-ray structure and properties of an unusual pentacarbonyl(2,2′-pyridyl-quinoxaline) tungsten complex

The first example of a monodentate complexation of 2-(2′-pyridyl)quinoxaline (pq) to a metal centre through N4 is reported. Photochemical exchange of the THF ligand in W(CO)5THF by pq yields W(CO)5(N4-pq) (1), where the potentially bidentate pq ligand coordinates in an unusual monodentate fashion. Complex 1 is isolated as orange crystals and fully characterized on the basis of NMR, IR, UV–Vis and emission spectroscopy. The structure of 1 was determined by X-ray analysis. W(CO)5(N4-pq) (1) crystallizes in space group P21/n, monoclinic crystal system with α = 7.0237(5) Å, b = 10.4618(8) Å, c = 23.7768(18) Å, Z = 4 and V = 1731.9(2) Å3. Complex 1 exhibits intramolecular CH⋯N and intermolecular CH⋯O hydrogen bonds between the CH groups and nitrogen atoms of quinoxaline and CH groups and oxygen atoms of carbonyls, respectively, resulting in a supramolecular architecture in solid state. The preference to N4 as coordination site is discussed in terms of electronic interactions. Solutions of 1 emits dually at 77 K while they are moderately instable at room temperature, as 1 undergoes chelation via a first-order kinetic process to form W(CO)4pq (2). The determined reaction rate of 1 in toluene is 2.3 × 10−5 s−1 (at 298 K) and is compared with literature values for other W(CO)5L (L:diimine) complexes.This project is co-funded by the European Social Fund and National Resources-EPEAEK II-‘Pythagoras I’.Peer reviewe

Synthesis, characterization and crystal structure of rhenium(I) tricarbonyl diimine complexes coupled with their efficiency in producing hydrogen in a photocatalytic system

Herein, we present the synthesis and characterization of two complexes, namely [ReBr(CO)3amphen] (1) (amphen = 1,10-phenanthroline-5-amine) and [ReBr(CO)3pq] (2) (pq = 2-(2′pyridyl)quinoxaline); complex 2 is reported for the first time. The X-ray crystal structure of 2 has been determined. Electrochemical and photophysical studies have been performed to study the effect of the variation of the diimine ligand on the redox and optical properties of this class of compounds. Both complexes were used as photosensitizers for hydrogen production in a homogeneous photocatalytic system also carrying [Co(dmgH)2] as a hydrogen reaction catalyst, triethanolamine as an irreversible reductive quencher and AcOH as proton source. Complex 1 produces H2 after only 2 h irradiation while complex 2 requires 24 h indicating that the differences in the electronic properties influence their photosensitizing ability

Combining photosensitizers: The case of [Cl2Pt(bpym)Re(CO)3Cl] and its dithiolate analogs

The bimetallic complex [Cl2Pt(bpym)Re(CO)(3)Cl] (4) (where bpym denotes 2,2’-bipyrimidine) has been prepared along with the corresponding monometallic precursors and the dithiolate derivatives with bdt(2-) (1,2-benzene-dithiolate) and mnt(2-) (1,2-maleonitrile-dithiolate). The compounds have been characterized using elemental analysis, NMR, FTIR, UV-Vis and cyclic voltammetry methods. DFT and TD-DFT calculations on all the complexes under study allow us to correlate geometries and electronic structures. The theoretical studies of the dithiolate bimetallic complexes assigned the main band in the UV-Vis spectrum as a mixed metal ligand to ligand charge transfer transition (MML’CT), analogous to [M(diimine)(dithiolate)] complexes, with the former red shifted due to the presence of the Re(CO)(3)Cl moiety. Moreover coordination of the dithiolate ligand to the bimetallic complex 4 influences not only the energy, but also the nature of HOMO orbital altering it from Re(CO)(3)Cl to Pt/bdt character. (C) 2012 Elsevier Ltd. All rights reserved