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Novel nickel(ii) complexes bearing (tbutyl)bis(diphenylphosphanyl)amine and different halogenido ligands, [Ni(P,P)X2] = [Ni{tBuN(PPh2)2-κ2P}X2], (X = Cl, Br, I) are prepared, characterized by IR and NMR spectroscopy, mass spectrometry and X-ray crystallography, and tested as catalysts in the Kumada cross-coupling reaction of model substituted iodobenzenes and p-tolylmagnesium bromide. The data obtained together with DFT calculations indicate that these new catalysts operate in the Ni(i)–Ni(iii) mode. The highest catalytic activity and selectivity are exhibited by [Ni(P,P)Cl2], which is most easily reduced by the used Grignard reagent to the Ni(i) state. This process is much more energy demanding in the case of the bromido and iodido complexes, causing the appearance of the induction period. [Ni(P,P)Cl2] is also very active in the cross-couplings of substrates with iodine atoms sterically shielded by ortho substituents. The data obtained are in good accordance with the described positive effect of the increased electron-releasing power of N-substituents R′ on the overall catalytic performance of [Ni{R′N(PPh2)2-κ2P}X2] complexes. This journal is © The Royal Society of Chemistry

The synthesis, as well as the structural and electronic properties of the [Mn(O,O)(N,N)(NO3)] complexes, (O,O) = {PhC(O)NP(O)PPh2}−, (N,N) = phenanthroline (1), neocuproine (2) and 2,2′-bipyridine (3) is reported. The three complexes were structurally characterized by X-ray crystallography, and complexes 1 and 2 were shown to be closer to octahedral, whereas 3 to trigonal prismatic. The zero-field splitting parameters of these S = 5/2 systems were determined by X- and Q-band EPR spectroscopy, revealing a small but significant difference in the magnitude of |D| for complex 3 (0.18 cm−1) compared to those of 1 and 2 (0.14 and 0.12 cm−1, respectively). These differences are attributed to the structural and electronic properties of complexes 1–3. The latter were probed by DFT calculations, which showed different DSOC contributions among the three complexes. © 2021 Elsevier Ltd

The synthesis and catalytic properties in Kumada C–C coupling of the [Ni(BIPHEP)X2] complexes, X = Cl (1), Br (2), are described. The crystal structures of the BIPHEP ligand and 2 are also presented and compared with previously reported crystal structures of atropisomeric bidentate phosphine ligands (P,P) and related [M(P,P)X2] complexes (M = Ni, Pd, Pt). BIPHEP crystallizes in the C2/c space group, with both enantiomers present in the unit cell. This is consistent with BIPHEP being a “tropos” ligand. Complex 2 crystallizes in the P21/a space group. There are two symmetry-independent molecules in the asymmetric unit, namely 2a and 2b, in which the BIPHEP ligand adopts the S or the R configuration, respectively. Complexes 2a and 2b exhibit a severely tetrahedrally-distorted square planar NiP2Br2 coordination sphere, with a PNiP bite angle of 93.3° and 94.7°, respectively. The observed catalytic behavior of complexes 1 and 2 in the Kumada coupling between p-tert-butyl-halogenobenzene and p-tolylmagnesium chloride is benchmarked against that of [Ni(dppp)Cl2], dppp = 1,3-bis(diphenylphoshpino)propane. However, all three complexes are catalytically inactive in the Suzuki-Miyaura coupling reaction. © 2021 Elsevier B.V.

Diabetes mellitus is a debilitating disease, plaguing a significant number of people around the globe. Attempts to develop new drugs on well‐defined atoxic metalloforms, which are capable of influencing fundamental cellular processes overcoming insulin resistance, has triggered an upsurge in molecular research linked to zinc metallodrugs. To that end, meticulous efforts were launched toward the design and synthesis of materials with insulin mimetic potential. Henceforth, trigonelline and N‐(2‐hydroxyethyl)‐iminodiacetic acid (HEIDAH2) were selected as organic substrates seeking binding to zinc (Zn(II)), with new crystalline compounds characterized by elemental analysis, FT‐IR, X‐rays, thermogravimetry (TGA), luminescence, NMR, and ESI‐MS spectrometry. Physicochemical characterization was followed by in vitro biochemical experiments, in which three out of the five zinc compounds emerged as atoxic, exhibiting bio‐activity profiles reflecting enhanced adipogenic potential. Concurrently, well‐defined qualitative–quantitative experiments provided links to genetic loci responsible for the observed effects, thereby unraveling their key involvement in signaling pathways in adipocyte tissue and insulin mimetic behavior. The collective results (a) signify the quintessential role of molecular studies in unearthing unknown facets of pathophysiological events in diabetes mellitus II, (b) reflect the close associations of properly configured molecular zincoforms to well‐defined biological profiles, and (c) set the stage for further physicochemical‐based development of efficient zinc antidiabetic metallodrugs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The poor handling and hygiene practices of contact lenses are the key reasons for their frequent contamination, and are responsible for developing ocular complications, such as microbial keratitis (MK). Thus there is a strong demand for the development of biomaterials of which contact lenses are made, combined with antimicrobial agents. For this purpose, the known water soluble silver(i) covalent polymers of glycine (GlyH), urea (U) and the salicylic acid (SalH2) of formulae [Ag3(Gly)2NO3]n(AGGLY), [Ag(U)NO3]n(AGU), and dimeric [Ag(salH)]2(AGSAL) were used. Water solutions ofAGGLY,AGUandAGSALwere dispersed in polymeric hydrogels using hydroxyethyl-methacrylate (HEMA) to form the biomaterialspHEMA@AGGLY-2,pHEMA@AGU-2, andpHEMA@AGSAL-2. The biomaterials were characterized by X-ray fluorescence (XRF) spectroscopy, thermogravimetric differential thermal analysis (TG-DTA), differential scanning calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR) and single crystal diffraction analysis. The antibacterial activity ofAGGLY,AGU,AGSAL,pHEMA@AGGLY-2,pHEMA@AGU-2andpHEMA@AGSAL-2was evaluated against the Gram negative speciesPseudomonas aeruginosa(P. aeruginosa) and Gram positive onesStaphylococcus epidermidis(S. epidermidis) andStaphylococcus aureus(S. aureus), which mainly colonize in contact lenses. Thein vitrotoxicity of the biomaterials and their ingredients was evaluated against normal human corneal epithelial cells (HCECs) whereas thein vitrogenotoxicity was evaluated by the micronucleus (MN) assay in HCECs. TheArtemia salinaandAllium cepamodels were applied for the evaluation ofin vivotoxicity and genotoxicity of the materials. Following our studies, the new biomaterialspHEMA@AGGLY-2,pHEMA@AGU-2, andpHEMA@AGSAL-2are suggested as efficient candidates for the development of antimicrobial contact lenses. © The Royal Society of Chemistry 2021.

Strain effects on g and metal hyperfine coupling tensors, A, are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{Ph2P(O)NP(O)Ph2-κ2O,O′}2], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO4 coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit 31P correlation ridges that have unusual inverse or so-called "boomerang" shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation. © 2020 American Chemical Society.

The synthesis and the structural characterization of the octahedral trans-[Co(OPPh2)(EPPh2)N2(dmf)2], E = S (1), Se (2), complexes is described. These complexes are formed by crystallization of the corresponding tetrahedral [Co(OPPh2)(EPPh2)N2] complexes in the presence of dimethylformamide (dmf) and are the first examples of intact octahedral Co(ii) complexes bearing dichalcogenidoimidodiphosphinato ligands. X-ray crystallography studies revealed a trans-CoO4E2 first coordination sphere consisting of two chelating (OPPh2)(EPPh2)N- ligands, as well as two dmf molecules coordinated via their O atoms. The isomorphous complexes 1 and 2 were studied by Direct Current magnetometry and shown to exhibit axial magnetic anisotropy. This finding was unequivocally confirmed by magnetic susceptibility measurements on an oriented crystal of complex 1, which clearly defined its easy axis of magnetization. Alternating Current magnetometry studies revealed field-induced slow relaxation of magnetization for both complexes, the characteristics of which are compared with those of other octahedral Co(ii) complexes. The effects of the Se- vs. S-coordination on the magnetic anisotropy and relaxation properties of these and other 3d metal complexes are discussed. © 2019 the Partner Organisations.

The reactions of hydrated lanthanide(III) [Ln(III)] nitrates and salicylideneaniline (salanH) have provided access to two families of mononuclear complexes depending on the reaction solvent used. In MeCN, the products are [Ln(NO3)3(salanH)2(H2O)]·MeCN, and, in MeOH, the products are [Ln(NO3)3(salanH)2(MeOH)]·(salanH). The complexes within each family are proven to be isomorphous. The structures of complexes [Ln(NO3)3(salanH)2(H2O)]·MeCN (Ln = Eu, 4·MeCN_Eu, Ln = Dy, 7·MeCN_Dy; Ln = Yb, 10·MeCN_Yb) and [Ln(NO3)3(salanH)2(MeOH)]·(salanH) (Ln = Tb, 17_Tb; Ln = Dy, 18_Dy) have been solved by single-crystal X-ray crystallography. In the five complexes, the LnIII center is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms from the two monodentate zwitterionic salanH ligands, and one oxygen atom from the coordinated H2O or MeOH group. The salanH ligands are mutually “cis” in 4·MeCN_Eu, 7·MeCN_Dy and 10·MeCN_Yb while they are “trans” in 17_Tb and 18_Dy. The lattice salanH molecule in 17_Tb and 18_Dy is also in its zwitterionic form with the acidic H atom being clearly located on the imine nitrogen atom. The coordination polyhedra defined by the nine oxygen donor atoms can be described as spherical tricapped trigonal prisms in 4·MeCN_Eu, 7·MeCN_Dy, and 10·MeCN_Yb and as spherical capped square antiprisms in 17_Tb and 18_Dy. Various intermolecular interactions build the crystal structures, which are completely different in the members of the two families. Solid-state IR data of the complexes are discussed in terms of their structural features. 1H NMR data for the diamagnetic Y(III) complexes provide strong evidence that the compounds decompose in DMSO by releasing the coordinated salanH ligands. The solid complexes emit greenlight upon excitation at 360 nm (room temperature) or 405 nm (room temperature). The emission is ligand-based. The solid Pr(III), Nd(III), Sm(III), Er(III), and Yb(III) complexes of both families exhibit LnIII-centered emission in the near-IR region of the electromagnetic spectrum, but there is probably no efficient salanH→LnIII energy transfer responsible for this emission. Detailed magnetic studies reveal that complexes 7·MeCN_Dy, 17_Tb and 18_Dy show field-induced slow magnetic relaxation while complex [Tb(NO3)3(salanH)2(H2O)]·MeCN (6·MeCN_Tb) does not display such properties. The values of the effective energy barrier for magnetization reversal are 13.1 cm−1 for 7·MeCN_Dy, 14.8 cm−1 for 17_Tb, and 31.0 cm−1 for 18_Dy. The enhanced/improved properties of 17_Tb and 18_Dy, compared to those of 6_Tb and 7_Dy, have been correlated with the different supramolecular structural features of the two families. The molecules [Ln(NO3)3(salanH)2(MeOH)] of complexes 17_Tb and 18_Dy are by far better isolated (allowing for better slow magnetic relaxation properties) than the molecules [Ln(NO3)3(salanH)2(H2O)] in 6·MeCN_Tb and 7·MeCN_Dy. The perspectives of the present initial studies in the Ln(III)/salanH chemistry are discussed.

The synthesis and characterization of the dinuclear Cu(II) complex [Cu(μ 2 -OH){Ph 2 P(O)NP(O)Ph 2 -κ 1 O,O′}(1,10-phen-κ 2 N,N′)] 2 ·2H 2 O (1), 1,10-phen = 1,10-phenanthroline, is described. X-ray crystallographic studies reveal that the Cu(II) centers of 1 are bridged by two OH − groups and are coordinated by the (O,O) = Ph 2 P(O)NP(O)Ph 2 − ligand in a monodentate fashion, unprecedented for Cu(II). The crystal lattice of 1 also contains H 2 O molecules, which are involved in the formation of a hydrogen bonding network with bridging OH − groups and noncoordinated O atoms of the (O,O) ligand. These H 2 O molecules are arranged in the crystal lattice of 1 as tetrameric clusters. The packing of molecules in the structure of 1 was investigated by Hirshfeld Surface analysis. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.

In this work, the structural and spectroscopic characterization of trans-[Ni(OPPh2)(EPPh2)N)2(dmso)2], E = S, Se, complexes is described. These Ni(II) complexes contain two chelating (O,E) = [(OPPh2)(EPPh2)N)]− ligands, as well as two dimethyl sulfoxide (dmso) molecules coordinated via their O atoms. X-ray crystallography studies revealed a highly anisotropic pseudo-octahedral trans-NiO4E2 coordination environment, extending the literature dataset of their trans-[Ni(O,E)2(sol)2], sol = dmf, thf, counterparts. Collectively considered, these six complexes contain similar coordination spheres, exhibiting, however, subtle structural differences due to the nature of the donor atom (E) and solvent molecule (sol) coordinated to Ni(II). The spin Hamiltonian parameters of S = 1 trans-[Ni(O,Se)2(dmso)2], E = S, Se, were accurately determined by high-frequency and -field EPR spectroscopy, applying a methodology already used for trans-[Ni(O,E)2(sol)2], sol = dmf, thf. Magnetostructural correlations are explored between all members of this sub-family of Ni(II) complexes. © 2018 Elsevier Ltd

Herein, we present the preparation and characterization of two nickel dithiolene complexes, namely [Ni(C3S2C2Ph22)] (1) and [Ni(C3p-OMe-C6H42)] (2). X-ray diffraction data for 2 collected on single crystals reveal that the complex is a neutral mononuclear entity with symmetric square planar geometry around the metal center. Electrochemical, photophysical, and theoretical studies have been employed to characterize and to probe both compounds under study in photoinduced hydrogen evolution experiments. Catalyst (2) performs better than catalyst (1), reaching 73 TONs over a 5 h period with [Ru(bpy)3]Cl2 as photosensitizer, in MeCN–water solvent mixture with ascorbate at pH 4 as a sacrificial electron donor. The different catalytic activity between the two compounds is discussed based on their different electronic properties. © 2018 Elsevier Ltd

Breast cancer (BrCa) remains an unmet medical need despite the revolutionary development of antibody treatments and protein kinase inhibitors. In the current study, a series of novel substituted pyridopyrazine derivatives have been rationally designed and evaluated as multi-kinase inhibitors in the PI3K pathway. The target compounds were prepared from 6-amino-2-picoline, which upon nitration and selective reduction was converted to suitably substituted 6-methyl-7-aminopyrido[2,3-b]pyrazines. Suitable manipulation of the former amines provided the designed analogues, which were then assessed in vitro against several BrCa cell lines using the MTT cytotoxicity assay. The most potent compounds underwent evaluation in a broad spectrum of protein kinases, while their pharmacokinetic parameters were measured by LC-MS/MS. In vivo evaluation of a hit compound (14a) was performed in a HER2 amplified BrCa xenograft model (HCC1954) and efficacy was determined using Western blot based phosphokinase assays and immunohistochemistry. This derivative showed low micromolar cytotoxic potency in all BrCa cell lines, a mild inhibition of the PI3Kα wild type and H1047R mutated enzyme and excellent pharmacokinetic parameters following oral and intraperitoneal administration at the designed dose of 10 mg/kg, with absence of in vivo phenotypic toxicity. Interestingly, compound 14a inhibited the growth of xenografted tumors. Analysis of excised tumors from the treated animals showed a significantly reduced population of Ki-67 positive cells, as well as downregulated levels of phosphorylated AKT, ERK1/2 and SRC compared to vehicle treated animals. Finally, the specificity of 14a was assessed in a panel of 31 kinases where a mild, but direct, inhibition of the MET receptor tyrosine kinase was observed. © 2016 Elsevier Masson SAS

Interaction of Cu(NO3)2 with phenyl 2-pyridyl ketoxime (PhPyCNOH) in the presence or absence of sodium diclofenac (Nadicl) leads to the formation of mono- or double-decker trinuclear clusters, respectively, characterized as inverse-9-metallacrown-3 accommodating dicl- or NO3- anions. The structures of [Cu3(PhPyCNO)3(μ3-O)(NO3)]2 (1) and [Cu3(PhPyCNO)3(μ3-OH)(dicl)2]·MeOH·0.5H2O (2·MeOH·0.5H2O) were determined by X-ray crystallography. Magnetic studies show a large antiferromagnetic interaction, whereas a discrepancy appears between the low-temperature magnetic data and that predicted from an isotropic Hamiltonian model, indicating the influence of antisymmetric interactions. By using a different magnetic model with antisymmetric terms, the low-temperature susceptibility and magnetization data were fitted. The EPR data support the observation that 2 has isosceles or lower magnetic symmetry, whereas the antisymmetric exchange mechanism is used to identify the reported g values of the spectra. EPR studies also revealed that complex 2 keeps its structure in solution. The complexes interact with calf-thymus DNA by intercalation. The complexes, as well as [Cu2(dicl)4(H2O)2] (3), bind to albumins with relatively high binding constants. The highest cytotoxicity of the diclofenac compounds was observed after 24 h of incubation, whereas HL-60 cells recovered after 72 h of incubation in the presence of each compound. Moreover, complex 3 was the most cytotoxic among the compounds, and complex 2 was as cytotoxic as Nadicl. Mono- and double-decker inverse-9-metallacrown-3 CuII compounds constructed with phenyl 2-pyridyl ketoxime ligands accommodating diclofenac or nitrato ligands, respectively, have been structurally characterized and their biological behavior has been evaluated in vitro. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The novel [Ni(Ph2P)2N(CH2)3Si(OCH3)3-P,ṔI2] complex (1) was synthesized and investigated by a variety of spectroscopic methods (IR, 1H and 31P NMR). The molecular structure of 1, determined by single crystal X-ray diffraction, was compared with those of the analogue [Ni(Ph2P)2N(CH2)3Si(OCH3)3-P,ṔCl2] complex (2) and the recently reported [NiiCPrP)2NH-P,ṔI2] complex. Complexes 1 and 2 were tested as homogeneous catalysts for the oligomerization of ethylene, leading to the formation of C4 and, to a smaller extent, C6 products, in moderate yields. © 2016 Ioannis Stamatopoulos et al. 2016.