Photosensitizer in a molecular bowl: steric protection enhancing the photonuclease activity of copper(II) scorpionates

Steric encumbrance caused by the tripodal ligand in the ternary tris(3-phenylpyrazolyl)borate copper(II) heterocyclic base complexes [Cu(B)(Tp(Ph))](ClO(4)) (B = dipyridoquinoxaline, dipyridophenazine) leads to efficient cleavage of supercoiled DNA to its relaxed form upon exposure to red light at 632.8 and 694 nm as a result of protection of the photosensitizer in the molecular bowl of the {Cu(Tp(Ph))} moiety, which generates singlet oxygen as the reactive species in a type-II process.     

The effect of 3d-metal intercalation on the electronic structure of metallic and semiconducting nanotubes

The electronic structure of 3d-metal-intercalated metallic (5,5) and semiconducting (10,0) nanotubes has been studied by quantum-chemical methods. The total and partial densities of states of nanotubes as a function of metal concentration and nature and the carbon-shell structure have been calculated by the linear augmented-cylindrical-wave method. Metalized nanowires based on armchair (5,5) and zigzag (10,0) nanotubes with one, two, three, and four metal atoms in the cross-section have been calculated. The introduction of the metal is accompanied by a sharp increase in the density of states at the Fermi level of the nanowire, which determines the concentration of free electrons involved in charge transfer in the nanotube. The 3d electrons of the metal and the carbon shell are nearly equally involved in electron transport in intercalated wires. Both the 3d electrons of a metal and the carbon shell should be nearly equally involved in electron transport in intercalated wires. The introduction of metals not only affects the conductive state of the carbon nanotube but also changes the entire pattern of its valence band, in particular, increases the valence band width of the nanotube by 5–10 eV owing to the low-energy shift of the 2s(C) states.     

In vitro and in vivo antitumour studies of a new thiosemicarbazide derivative and its complexes with 3d-metal ions

A new ligand, 1-(2-furanthiocarbo)-3-thiosemicarbazide (H₂ftsc), prepared from thiosemicarbazide and carboxymethyl-2-furandithioate, forms complexes [Mn(ftsc)(H₂O)₂], [Pd(ftsc)] · 2H₂O, [M(Hftsc)(acac)₂] (M=Co^III or Cr^III), [M(Hftsc)₂(acac)] (M=Mn^III or Fe^III) and [Zn(Hftsc)₂] · 2H₂O, which were characterized by elemental analyses, magnetic susceptibility, i.r., electronic and n.m.r. spectral data. The Mössbauer spectra of [Fe(Hftsc)₂(acac)] at 298K and 80K suggest the presence of high-spin iron(III) with an S=5/2 state. In vivo and in vitro antitumour activity of the ligand and the complexes have been screened towards several tumour cell-lines.     

Reactivity of 3d-metal salt solvates in reactions with porphyrins: Influence of the trans effect

The reactivity of 3d-metal salt solvates [MX₂(S)₄] and [MX₂(S₁) _m (S₂)_4?m ] has been studied in reactions with different porphyrins: meso-tetraphenylporphine (H₂TPP), N-methyloctaethylporphine (H(N-Me)(β-Et)₈P), and meso-tetraphenyltetrabenzoporphine (H₂TBP(ms-Ph)₄). Solvents S, S₁, and S₂ are dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and pyridine (Py), respectively. The strong catalytic effect of the solvents and ligands with π orbitals on the reaction rates due to the trans influence in the coordination sphere of the salt solvates has been observed and explained. A possible activation mechanism of the trans influence was considered. A strong dependence of the trans effect on the nature of the metal and porphyrin was shown.     

New insights into the visible-light-induced DNA cleavage activity of dipyridoquinoxaline complexes of bivalent 3d-metal ions

Dipyridoquinoxaline (dpq) complexes of bivalent 3d-metal ions, viz., [FeII(dpq)3](PF6)2 (1), [CoII(dpq)3](ClO4)2 (2), [NiII(dpq)3](ClO4)2 (3), [CuII(dpq)2(H2O)](ClO4)2 (4), [ZnII(dpq)3](ClO4)2 (5), and [ZnII(dpq)2(DMF)2](ClO4)2 (5a) (DMF = N,N-dimethylformamide), are prepared and their photoinduced DNA cleavage activity studied. Structural characterization for the complexes 1 and 5a is done by single-crystal X-ray crystallography. All the complexes show efficient binding propensity to calf thymus DNA with a binding constant (K) value of approximately 10(5) M(-1). Complexes 1, 2, and 4 show metal-based cyclic voltammetric responses at 1.2, 0.4, and 0.09 V (vs SCE) in DMF 0.1 M [Bun4N](ClO4) assignable to the respective FeIII/FeII, CoIII/CoII, and CuII/CuI couples. The NiII and ZnII complexes do not show any metal-based redox process. The dpq-based reductions are observed in the potential range of -1.0 to -1.7 V vs SCE. DNA melting and viscosity data indicate the groove-binding nature of the complexes. Control experiments using distamycin-A suggest a minor groove-binding propensity of the complexes. The complexes exhibit photoinduced cleavage of supercoiled pUC19 DNA in UV light of 365 nm. The diamagnetic d6-FeII and d10-ZnII complexes are cleavage-inactive on irradiation with visible light. The paramagnetic d7-CoII and d9-CuII complexes exhibit efficient DNA cleavage activity on photoirradiation at their respective d-d band. The paramagnetic d8-NiII complex displays only minor DNA cleavage activity on irradiation at its d-d band. The DNA cleavage reactions at visible light under aerobic conditions involve the formation of hydroxyl radical. The CoII complex shows photocleavage of DNA under an argon atmosphere. Theoretical calculations on the complexes suggest a photoredox pathway in preference to a type-2 process forming singlet oxygen for the visible-light-induced DNA cleavage activity of the 3d-metal complexes. The theoretical data also predict that the photoredox pathway is favorable for the 3d7-CoII and 3d9-CuII complexes to exhibit DNA cleavage activity, while the analogous 3d6-FeII and 3d8-NiII complexes are energetically unfavorable for the exhibition of such activity under visible light. The CoII and CuII complexes are better suited for designing and developing new metal-based PDT agents than their cleavage-inactive FeII, NiII, and ZnII analogues.     

Hydrogenation of 3d-metal oxide clusters: Effects on the structure and magnetic properties

The geometrical structures and properties of the M₈O₁₂, M₈O₁₂H₈, and M₈O₁₂H₁₂ clusters are explored using density functional theory with the generalized gradient approximation for all 3d-metals M from Sc to Zn. It is found that the geometries and total spin magnetic moments of the clusters depended strongly on the 3d-atom type and the hydrogenation extent. More than the half of all of the 30 clusters had singlet lowest total energy states, which could be described as either nonmagnetic or antiferromagnetic. Hydrogenation increases the total spin magnetic moments of the M₈O₁₂H₁₂ clusters when MMn Ni, which become larger by four Bohr magneton than those of the corresponding unary clusters M₈. Hydrogenation substantially affects such properties as polarizability, forbidden band gaps, and dipole moments. Collective superexchange where the local total spin magnetic moments of two atom squads are coupled antiparallel was observed in antiferromagnetic singlet states of Fe₈O₁₂H₈ and Co₈O₁₂H₈, whereas the lowest total energy states of their neighbors Mn₈O₁₂H₈ and Ni₈O₁₂H₈ are ferrimagnetic and ferromagnetic, respectively. Hydrogenation leads to a decrease in the average binding energy per atom when moving across the 3d-metal atom series. © 2018 Wiley Periodicals, Inc.     

Electronic spectra of jet-cooled calix[4]arene and its van der Waals clusters: encapsulation of a neutral atom in a molecular bowl

The encapsulation of neutral guest has been studied for calix[4]arene (C4A) by forming van der Waals clusters with Ar and Ne in supersonic jets. The electronic transitions of these clusters suggest that the first Ar (Ne) is encapsulated inside the C4A cavity, while the next atoms are bound outside.     

A chiral molecular bowl containing three ferrocenes: synthesis and its efficiency in an optical resolution of 1,1'-bi-2-naphthol

Condensation reaction of 1,1'-ferrocenedicarboxaldehyde with (1R,2R)-1,2-diaminocyclohexane affords a novel bowl-shaped macrocycle with a chiral concave cavity which exhibits a remarkable ability as a host material for the enantioselective enclathration of 1,1'-bi-2-naphthol.     

Synthesis,DNA-binding,molecular docking and cytotoxic activity in vitro evaluation of ruthenium(II) complexes

Transition Metal Chemistry - Five new ruthenium(II) polypyridyl complexes [Ru(N–N)2(BTCP)](ClO4)2 (BTCP?=?2-(bicyclo[2.2.1]hept-5-en-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline;...     

Cytotoxicity activity,in silico molecular docking,protein- and DNA-binding study of a new Ni(II) Schiff base complex

Abstract

One new nickel(II) complex, [Ni(L)] (1), was synthesized from the Schiff base ligand derived from pyrrole-2-carboxaldehyde and 1,3-diaminopropane. Complex 1 was characterized by elemental analysis, IR, UV-Vis and ESI mass spectroscopy, cyclic voltammetry, and single-crystal X-ray structure analysis. Crystallographic results show that two Ni(II) monomeric moieties are present with similar structural features but with slightly different bond lengths and bond angles. The geometry around the Ni(II) center is distorted square planar. DNA-binding properties of complex 1 were well explored by employing UV-Vis and fluorescence spectral methods, cyclic voltammetry, and by viscosity measurements. Similarly the protein-binding study was studied by multispectroscopic techniques using both BSA and HSA. The cytotoxicity study of the compound has also been evaluated. Notably, the in vitro cytotoxicity of complex 1 on two cancer cell lines (AGS and A549) demonstrates that complex 1 has very good anticancer activity. MTT assay, cell-cycle analysis, and annexin-V assay have been performed to know the extent of effect of complex 1 as anticancer agent. Further, in silico molecular docking study revealed that the nickel(II) complex fits into the minor groove of duplex DNA by hydrophobic interaction with functional groups of B-DNA.     

A theoretical study of the photochemical α-cleavage processes in symmetric and non-symmetric ketones

The energy profiles for radical dissociation of the lowest triplet state of various symmetric and non-symmetric ketones have been computed using the MINDO/3 method and employing configuration interaction. The results of radical dissociation of thioformaldehyde were also examined. In each case, the activation barrier arises from an avoided crossing between two states of different symmetry. Our analysis reveals that the perpendicular motion of the carbonyl carbon is an important component in the reaction coordinate.     

Incorporation of 3d-metal ions in the hexagonal channels of the Sr5(PO4)3OH apatite

Strontium phosphate apatites with compositions Sr₅(PO₄)₃Zn_0.15O_0.3(OH)_0.7, Sr₅(PO₄)₃Ni_0.2O_0.4(OH)_0.6, and Sr₅(PO₄)₃Co_0.2O_0.5(OH)_0.4 were synthesized by solid state reaction at 1400 °C in air. The samples were characterized by powder X-ray diffraction, EDX analysis, magnetic measurements and IR spectroscopy. The crystal structures were refined by the Rietveld method in the space group P6₃/m with lattice constants a = 9.7499(1), 9.7722(1), 9.7507(1) Å and c = 7.3066(1), 7.2962(1), 7.2988(1) Å, respectively. The 3d-metal atoms were found randomly distributed in the hexagonal channels formally substituting hydrogen in the initial hydroxyapatite. Zn and Ni atoms were twofold coordinated by oxygen atoms such that the linear O–M–O groups formed in the channel separated by the OH groups. Co atom was shifted from the channel center giving the O–Co–O fragment distorted from a linear geometry probably due to the additional coordination by the oxygen atoms of the phosphate groups.     

The effect of the molecular weight of chitosan nanoparticles and its application on drug delivery

Nanoparticulate drug delivery systems offer several advantages over conventional forms of dosing, with polymer nanoparticles prepared from biomaterials being good candidates for use in drug delivery. We selected fluorouracil (5FU) as a model drug because it has been suggested that chitosan might prevent the side effects induced by 5FU. We have exploited the complexation between oppositely charged macromolecules to develop a safe and efficient method of preparation of chitosan bead formulations for use as drug delivery systems. In this study, we examined the effect that the molecular weight of chitosan had on the resulting nanoparticles' properties; the initial concentration of chitosan was held constant, but its molecular weight was decreased through the action of NaNO₂. FTIR spectroscopy suggested that no structural change occurred during the depolymerization process. The diameters of the nanoparticles—determined using dynamic light scattering and TEM techniques—decreased as the value of the viscosity of molecular weight (Mv) of chitosan decreased. In addition, we prepared fluorouracil-loaded chitosan nanoparticles and characterized them using NMR spectroscopy. The encapsulation efficiency increased as the value of Mv of chitosan decreased. The particles produced using 55-kDa chitosan had a mean diameter of 70.6 nm and a 66% drug loading.     

The possibility of manganese disorder in LiMnPO4 and its effect on the electrochemical activity

Orthorhombic structured LiMnPO₄ was synthesized by a hydrothermal method. The possibility of manganese disorder in LiMnPO₄ was studied using powder X-ray diffraction and X-ray absorption fine structure analysis. A manganese-rich model was proposed for the hydrothermally synthesized LiMnPO₄. It is found that the extent of Mn²⁺ disorder on the Li⁺ sites was suppressed by increasing the reaction temperature, which led to an enhanced electrochemical activity. These observations are explained on the basis of the manganese-rich model, in which the disordered Mn²⁺ on the Li⁺ sites may act as a blockage in one-dimensional lithium ion transport pathway, thus reducing the electrochemical activity of the LiMnPO₄ prepared at low temperatures.     

An ab initio study on the torsional surface of alkanes and its effect on molecular simulations of alkanes and a DPPC bilayer

Energies of 119 conformations of normal alkanes from butane to heptane were calculated at approximately the CCSD(T)/cc-pVQZ level. Energies of gauche (g) conformers relative to trans (t) decrease as chain length increases. In what is termed the "positive pentane effect", adjacent gauche conformers of the same sign are stabilized compared to nonadjacent conformers; e.g., for hexane the energies of tgt, tgg, and gtg are 0.600, 0.930, and 1.18 kcal/mol, respectively. Torsional terms in the CHARMM27 (C27) force field were fit to the calculated QM energies to yield a revised potential, C27r. Molecular dynamics simulations of normal alkanes (heptane, decane, tridecane, and pentadecane) with C27r yield higher populations of gauche states, increased transition rates, and improved agreement with experiment as compared to C27. In addition, C27r simulations of a hydrated DPPC lipid bilayer yield improved agreement with the experimental NMR deuterium order parameters for the aliphatic chain ends.     

A bowl-shaped phosphine as a ligand in palladium-catalyzed Suzuki-Miyaura coupling of aryl chlorides: effect of the depth of the bowl

[reaction: see text] Bowl-shaped phosphine ligands were found to be highly effective in Suzuki-Miyaura coupling of unactivated aryl chlorides, in which the depth of the bowl affected the catalytic activity considerably.     

Change of the molecular surface and volume during internal rotation and its effect on conformational equilibrium in solution

Conformational dependence of the molecular surface S and molecular volume V for hexane and 1,1,2-trichloroethane during rotation around a central bond in the molecules have been calculated. A model of overlapping spheres is used, the size of the spheres being determined by Van der Waals radii of individual atoms. Plots of S and V against torsional angle φ are compared with the potential of internal rotation of both molecules E(φ). The calculated molecular surfaces and volumes of the two molecules for the most stable conformers mutually differ by several percent as experimental results also indicate. We also show that the differences in S and V between individual conformers always affect conformational equilibrium in solution even if solvent-solute interaction energies are not explicitly considered. As a consequence of the mentioned volume changes during internal rotation in a molecule, the conformational energies for hydrocarbons in the condensed and gaseous phases can differ by as much as several kJ mol^?1.     

Comparative study of mono- and dinuclear complexes of late 3d-metal chlorides with N,N-dimethylformamide in the gas phase

Mono- and binuclear complexes of N,N-dimethylformamide (DMF) with chlorides of the divalent, late 3d metals M = Co, Ni, Cu, and Zn are investigated by means of electrospray ionization (ESI). Specifically, ESI leads to monocations of the type [(DMF)(n)MCl](+) and [(DMF)(n)M(2)Cl(3)](+), of which the species with n = 2 and 3 were selected for in-depth studies. The latter include collision-induced dissociation experiments, gas-phase infrared spectroscopy, and calculations using density functional theory. The mononuclear complexes [(DMF)(n)MCl](+) almost exclusively lose neutral DMF upon collisional activation with the notable exception of the copper complex, for which also a reduction from Cu(II) to Cu(I) concomitant with the release of atomic chlorine is observed. For the dinuclear clusters, there exists a competition between loss of a DMF ligand and cluster degradation via loss of neutral MCl(2) with decreasing cluster stability from cobalt to zinc. For the specific case of [(DMF)(n)ZnCl](+) and [(DMF)(n)Zn(2)Cl(3)](+), ion-mobility mass spectrometry indicates the existence of two isomeric cluster ions in the case of [(DMF)(2)Zn(2)Cl(3)](+) which corroborates parallel theoretical predictions.