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Four new oxidovanadium [V V OL 1-4 (ema)] complexes ( 1 - 4 ) have been synthesized using tridentate binegative ONO donor ligands H 2 L 1-4 [H 2 L 1 : ( E )- N' -(2-hydroxybenzylidene)furan-2-carbohydrazide; H 2 L 2 : ( E )- N' -(4-(diethylamino)-2-hydroxybenzylidene)thiophene-2-carbohydrazide; H 2 L 3 : ( E )-2-(4-(diethylamino)-2-hydroxybenzylideneamino)-4-methylphenol; H 2 L 4 : ( E )-2-(3-ethoxy-2-hydroxybenzylideneamino)-4-methylphenol] and ethyl maltol (Hema) as a bidentate uninegative coligand and characterized by CHNS analysis, IR, UV-vis, NMR, and HR-ESI-MS methods. The structures of 1 , 3 , and 4 are confirmed by single-crystal X-ray analysis. The hydrophobicity and hydrolytic stability of the complexes are tested using NMR and HR-ESI-MS and correlated with their observed biological activities. It is observed that 1 hydrolyzed into a penta-coordinated vanadium-hydroxyl species (V V OL 1 -OH) with the release of ethyl maltol, whereas 2 - 4 are found quite stable under the investigated time period. The biomolecular interaction of 1 - 4 with DNA and BSA was performed using absorbance, fluorescence, and circular dichroism techniques. The in vitro cytotoxicity activities of H 2 L 1-4 and 1 - 4 were tested against A549, HT-29, and NIH-3T3 cell lines. Among complexes, 2 with an IC 50 value of 4.4 ± 0.1 μM displayed maximum anticancer activity against the HT-29 cell line. Complexes induce cell cycle arrest at the G2/M phase and subsequently trigger dose-dependent cell apoptosis, which is obtained by the cell apoptosis analysis via flow cytometry and confocal microscopy assays. Being fluorescence active, 1 - 4 were observed to target the mitochondria and exhibit disruption of the mitochondrial membrane potential, which consequently causes overproduction of intracellular reactive oxygen species and induced cell apoptosis.

A series of nine new complexes of ruthenium(II), rhodium(III), and iridium(III) incorporated with pyrazoline-based ligands were synthesized and characterized by various spectroscopic techniques such as FTIR, 1 H NMR, 13 C NMR, UV-Vis spectroscopy, ESI-MS spectrometry and X-ray crystallographic studies. All the synthesized compounds were assessed for their antibacterial abilities against Gram-positive and Gram-negative bacterial strains. The compounds showed better antibacterial activity against two Gram-positive bacteria (Staphylococcus aureus and Bacillus Thuringiensis), with activities superior to standard kanamycin. Antioxidant studies revealed the mild radical scavenging proficiency of the compounds. DNA binding studies using fluorescence spectroscopy showed that the compounds could bind to Salmon Milt DNA electrostatically via external contact and groove surface binding with moderate affinity. The synthesized complexes were tested for anticancer activity using cell cytotoxicity and apoptosis assays in Dalton's lymphoma (DL) cell lines. The findings were compared to cisplatin (the standard drug) under identical experimental conditions. The cell viability results showed that complex 7 induced higher cytotoxicity in the DL cell line than the other tested compounds. The results of the molecular docking analysis further suggest that selective complexes have complete contact with the active amino acids sites of anti-apoptotic Bcl-2 family protein., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this work, one oxidomethoxidovanadium(V) [V V O(L)(OMe)] (1) and two mixed-ligand oxidovanadium(IV) [V IV O(L)(phen)] (2), and [V IV O(L)(bipy)] (3) complexes have been synthesized using a tridentate bi-negative ONS donor dithiocarbazate as main ligand, H 2 L [where, H 2 L = S-benzyl-3-(2-hydroxy-3-ethoxyphenyl)methylenedithiocarbazate] along with 1,10-phenanthroline (phen) (for 2) and 2,2'-bipyridine (bipy) (for 3) as co-ligands. The ligand and complexes have been characterised by FT-IR, UV-vis, NMR, and HR-ESI-MS techniques. Distorted square pyramidal for 1, and distorted octahedral geometry for 2 and 3 was confirmed by single crystal X-ray crystallography. The behavior of 1-3 in solution medium has been investigated through various physicochemical techniques. It is observed that 1 completely and 2-3 partially decomposes and converts into a penta-coordinated species, [V IV O(L)(DMSO/H 2 O)] after the release of the methoxido group (1) or breaking of the diimine based co-ligands (2 and 3) in DMSO/aqueous solution. Interestingly, in DMSO/aqueous solution, 1 gets completely reduced and converted into the corresponding oxidovanadium(IV) species. Interaction of 1-3 with calf thymus DNA (CT-DNA) was investigated and the results show, complex 2 exhibited the maximum binding constants, K b  = 7.12 × 10 4  M -1 . The anticancer potential of 1-3 was evaluated by cell viability assay against human breast carcinoma cell, MCF-7, and noncancerous mouse embryonic cell, NIH-3T3 and 2 was found to be the most cytotoxic complex (IC 50  = 6.73 ± 0.36 μM) in the series. In addition, 2 selectively inhibit colony formation compared to the rest complexes. Also, the cell cycle studies of the complexes were performed using flow cytometry analysis., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Redox-active multimetallic platforms with synthetically addressable and hemilabile active sites are attractive synthetic targets for mimicking the reactivity of enzymatic co-factors toward multielectron transformations. To this end, a family of ternary clusters featuring three edge metal sites anchored on a [Co6Se8] multimetallic support via amidophosphine ligands are a promising platform. In this report, we explore how small changes in the stereoelectronic properties of these ligands alter [Co6Se8] metalloligand formation, but also substrate binding affinity and strength of the edge/support interaction in two new ternary clusters, M3Co6Se8L6 (M = Zn, Fe; L(-) = Ph2PN(-)iPr). These clusters are characterized extensively using a range of methods, including single crystal X-ray diffraction, electronic absorption spectroscopy and cyclic voltammetry. Substrate binding studies reveal that Fe3Co6Se8L6 resists coordination of larger ligands like pyridine or tetrahydrofuran, but binds the smaller ligand CNtBu. Additionally, investigations into the synthesis of new [Co6Se8] metalloligands using two aminophosphines, Ph2PN(H)iPr (LH) and iPr2PN(H)iPr, led to the synthesis and characterization of Co6Se8LH6, as well as the smaller clusters Co4Se2(CO)6LH4, Co3Se(μ2-PPh2)(CO)4LH3, and [Co(CO)3(iPr2PN(H)iPr)]2. Cumulatively, this study expands our understanding on the effect of the stereoelectronic properties of aminophosphine ligands in the synthesis of cobalt chalcogenide clusters, and, importantly on modulating the push-pull dynamic between the [Co6Se8] support, the edge metals and incoming coordinating ligands in ternary M3Co6Se8L6 clusters.

The reaction of 2-{2-(benzo[1,3]dioxol-5-yl)- diazo}-4-methylphenol (HL) with [Ru(PPh 3 ) 3 Cl 2 ] in ethanol resulted in the carbonylated ruthenium complex [RuL(PPh 3 ) 2 (CO)] ( 1 ), wherein metal-assisted decarbonylation via in situ ethanol dehydrogenation is observed. When the reaction was performed in acetonitrile, however, the complex [RuL(PPh 3 ) 2 (CH 3 CN)] ( 2 ) was obtained as the main product, probably by trapping of a common intermediate through coordination of CH 3 CN to the Ru(II) center. The analogous reaction of HL with [Ir(PPh 3 ) 3 Cl] in ethanol did not result in ethanol decarbonylation and instead gave the organoiridium hydride complex [IrL(PPh 3 ) 2 (H)] ( 3 ). Unambiguous evidence for the generation of CO via ruthenium-assisted ethanol oxidation is provided by the synthesis of the 13 C-labeled complex, [Ru(PPh 3 ) 2 L( 13 CO)] ( 1A ) using isotopically labeled ethanol, CH 3 13 CH 2 OH. To summarize all the evidence, a ruthenium-assisted mechanistic pathway for the decarbonylation and generation of alkane via alcohol dehydrogenation is proposed. In addition, the in vitro antiproliferative activity of complexes 1 - 3 was tested against human cervical (HeLa) and human colorectal adenocarcinoma (HT-29) cell lines. Complexes 1 - 3 showed impressive cytotoxicity against both HeLa (half-maximal inhibitory concentration (IC 50 ) value of 3.84-4.22 μM) and HT-29 cancer cells (IC 50 values between 3.3 and 4.5 μM). Moreover, the complexes were comparatively less toxic to noncancerous NIH-3T3 cells.

In order to shed light on metal-dependent mechanisms for O-O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O 2 -derived binuclear Co(III)- and Mn(III)-peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic H 2 O oxidation, and a Co-containing artificial leaf inspired by nature's photosynthetic H 2 O oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III). Density functional theory (DFT) calculations show that the frontier orbitals of the Co(III)-peroxo compound differ noticeably from the analogous Mn(III)-peroxo compound. The highest occupied molecular orbital (HOMO) associated with the Co(III)-peroxo is more localized on the peroxo in an antibonding π*(O-O) orbital, whereas the HOMO of the structurally analogous Mn(III)-peroxo is delocalized over both the metal d-orbitals and peroxo π*(O-O) orbital. With low-spin d 6 Co(III), filled t 2g orbitals prevent π-back-donation from the doubly occupied antibonding π*(O-O) orbital onto the metal ion. This is not the case with high-spin d 4 Mn(III), since these orbitals are half-filled. This weakens the peroxo O-O bond of the former relative to the latter.

The synthesis of ethoxido-bridged dinuclear oxidovanadium(IV) complexes of the general formula (HNEt 3 )[(VOL 1-3 ) 2 (μ-OEt)] (1-3) with the azo dyes 2-(2'-carboxy-5'-X-phenylazo)-4-methylphenol (H 2 L 1 , X = H; H 2 L 2 , X = NO 2 ) and 2-(2'-carboxy-5'-Br-phenylazo)-2-naphthol (H 2 L 3 ) as ligands is reported. The ligands differ in the substituents at the phenyl ring to probe their influence on the redox behavior, biological activity, and magnetochemistry of the complexes, for which the results are presented and discussed. All synthesized ligands and vanadium(IV) complexes have been characterized by various physicochemical techniques, namely, elemental analysis, electrospray ionization mass spectrometry, spectroscopic methods (UV/vis and IR), and cyclic voltammetry. X-ray crystallography of 1 and 3 revealed the presence of a twisted arrangement of the edged-shared bridging core unit. In agreement with the distorted nature of the twisted core, antiferromagnetic exchange interactions were observed between the vanadium(IV) centers of the dinuclear complexes with a superexchange mechanism operative. These results have been verified by DFT calculations. The complexes were also screened for their in vitro cytotoxicity against HeLa and HT-29 cancer cell lines. The results indicated that all the synthesized vanadium(IV) complexes (1-3) were cytotoxic in nature and were specific to a particular cell type. Complex 1 was found to be the most potent against HeLa cells (IC 50 value 1.92 μM).

Four novel dimeric bis-μ-imido bridged metal-metal bonded oxidomolybdenum(V) complexes [Mo V 2 O 2 L' 2 1-4 ] (1-4) (where L' 1-4 are rearranged ligands formed in situ from H 2 L 1-4 ) and a new mononuclear dioxidomolybdenum(VI) complex [Mo VI O 2 L 5 ] (5) synthesized from salen type N 2 O 2 ligands are reported. This rare series of imido-bridged complexes (1-4) have been furnished from rearranged H 3 L' 1-4 ligands, containing an aromatic diimine (o-phenylenediamine) "linker", where Mo assisted hydrolysis followed by -C═N bond cleavage of one of the arms of the ligand H 2 L 1-4 took place. A monomeric molybdenum(V) intermediate species [Mo V O(HL' 1-4 )(OEt)] (I d 1-4 ) was generated in situ. The concomitant deprotonation and dimerization of two molybdenum(V) intermediate species (I d 1-4 ) ultimately resulted in the formation of a bis-μ-imido bridge between the two molybdenum centers of [Mo V 2 O 2 L' 2 1-4 ] (1-4). The mechanism of formation of 1-4 has been discussed, and one of the rare intermediate monomeric molybdenum(V) species I d 4 has been isolated in the solid state and characterized. The monomeric dioxidomolybdenum(VI) complex [Mo VI O 2 L 5 ] (5) was prepared from the ligand H 2 L 5 where the aromatic "linker" was replaced by an aliphatic diimine (1,2-diaminopropane). All the ligands and complexes have been characterized by elemental analysis, IR, UV-vis spectroscopy, NMR, ESI-MS, and cyclic voltammetry, and the structural features of 1, 2, 4, and 5 have been solved by X-ray crystallography. The DNA binding and cleavage activity of 1-5 have been explored. The complexes interact with CT-DNA by the groove binding mode, and the binding constants range between 10 3 and 10 4 M -1 . Fairly good photoinduced cleavage of pUC19 supercoiled plasmid DNA was exhibited by all the complexes, with 4 showing the most promising photoinduced DNA cleavage activity of ∼93%. Moreover, in vitro cytotoxic activity of all the complexes was evaluated by MTT assay, which reveals that the complexes induce cell death in MCF-7 (human breast adenocarcinoma) and HCT-15 (colon cancer) cell lines.

In the copper-catalyzed oxidation of alcohols to aldehydes, a Cu(II)-alkoxide (Cu(II)-OR) intermediate is believed to modulate the αC-H bond strength of the deprotonated substrate to facilitate the oxidation. As a structural model for these intermediates, we characterized the electronic structure of the stable compound Tp(tBu)Cu(II)(OCH2CF3) (Tp(tBu) = hydro-tris(3-tert-butyl-pyrazolyl)borate) and investigated the influence of the trifluoroethoxide ligand on the electronic structure of the complex. The compound exhibits an electron paramagnetic resonance (EPR) spectrum with an unusually large gzz value of 2.44 and a small copper hyperfine coupling Azz of 40 × 10(-4) cm(-1) (120 MHz). Single-crystal electron nuclear double resonance (ENDOR) spectra show that the unpaired spin population is highly localized on the copper ion (≈68%), with no more than 15% on the ethoxide oxygen. Electronic absorption and magnetic circular dichroism (MCD) spectra show weak ligand-field transitions between 5000 and 12,000 cm(-1) and an intense ethoxide-to-copper charge transfer (LMCT) transition at 24,000 cm(-1), resulting in the red color of this complex. Resonance Raman (rR) spectroscopy reveals a Cu-O stretch mode at 592 cm(-1). Quantum chemical calculations support the interpretation and assignment of the experimental data. Compared to known Cu(II)-thiolate and Cu(II)-alkylperoxo complexes from the literature, we found an increased σ interaction in the Cu(II)-OR bond that results in the spectroscopic features. These insights lay the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations.

Three dioxidovanadium(V) complexes [VO2L(1-3)] (1-3) [HL(1)=1-napthoyl hydrazone of 2-acetyl pyridine, HL(2)=2-furoyl hydrazone of 2-acetyl pyridine and H2L(3)=isonicotinoyl hydrazone of 2-hydroxy benzaldehyde] have been reported. All the complexes were characterized by various spectroscopy (IR, UV-visible and NMR) and the molecular structures of 1 and 2 were characterized by single crystal X-ray diffraction technique. Structural report established five-coordinate geometries, distorted toward square pyramidal for each of 1 and 2, based on a tridentate -O,N,N coordinating anion and two oxido-O atoms. The experimental results show that the complexes interact with calf-thymus DNA (CT-DNA) possibly by a groove binding mode, with binding constants of ~10(5)M(-1). All complexes show good photo-induced cleavage of pUC19 supercoiled plasmid DNA with complex 1 showing the highest photo-induced DNA cleavage activity of ~68%. 1-3 also exhibit moderate binding affinity in the range of 10(3)-10(4)M(-1) towards bovine serum albumin (BSA), while all the complexes show good photo-induced BSA cleavage activity. Moreover the antiproliferative activity of all these complexes was studied, which reveal all compounds are significantly cytotoxic towards the HeLa cell line., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Eight alkali metal ion-mediated dioxidovanadium(v), [{V(V)O2L(1-6)}A(H2O)n]∝, complexes for A = Li(+), Na(+), K(+) and Cs(+), containing tridentate aroylhydrazonate ligands coordinating via ONO donor atoms, are described. All the synthesised ligands and the metal complexes were successfully characterised by elemental analysis, IR, UV-Vis and NMR spectroscopy. X-ray crystallographic investigation of 3, 5-7 shows the presence of distorted NO4 coordination geometries for LVO2(-) in each case, and varying μ-oxido and/or μ-aqua bridging with interesting variations correlated with the size of the alkali metal ions: with small Li(+), no bridging-O is found but four ion aggregates are found with Na(+), chains for K(+) and finally, layers for Cs(+). Two (5) or three-dimensional (3, 6 and 7) architectures are consolidated by hydrogen bonding. The dioxidovanadium(v) complexes were found to exhibit DNA binding activity due to their interaction with CT-DNA by the groove binding mode, with binding constants ranging from 10(3) to 10(4) M(-1). Complexes 1-8 were also tested for DNA nuclease activity against pUC19 plasmid DNA which showed that 6 and 7 had the best DNA binding and photonuclease activity; these results support their good protein binding and cleavage activity with binding constants ranging from 10(4) to 10(5) M(-1). Finally, the in vitro antiproliferative activity of all complexes was assayed against the HeLa cell line. Some of the complexes (2, 5, 6 and 7) show considerable activity compared to commonly used chemotherapeutic drugs. The variation in cytotoxicity of the complexes is influenced by the various functional groups attached to the aroylhydrazone derivative.