Search

The equimolar reaction between 1,9-bis(N,N-dimethylaminomethyl)-5,5′-diphenyldipyrromethane, H2L1 or 1,9-bis(3,5-dimethylpyrazolylmethyl)-5,5′-diethyldipyrromethane, H2L2 and [NiCl2(DME)] in the presence of KH yielded the neutral mononuclear nickel(II) complexes [Ni(L1)-κ4N,N,N,N], 1 and [Ni(L2)-κ4N,N,N,N], 2, respectively. Their X-ray structures revealed the formation of triple chelation by the ligand in both structures with quite different nickel(II)-surrounded square planar geometries owing to the steric difference between –NMe2 and 3,5-dimethylpyrazolyl groups. While the –NMe2 group substituted ligand L1 afforded nickel complex 1 with a plane of symmetry, 3,5-dimethylpyrazole substituted L2 rendered helical chirality in the structure of complex 2. Both the enantiomers (Δ and Λ) of complex 2 were observed in the crystal lattice. Their solution state behaviors were consistent with the solid-state structures as monitored by 1H NMR spectroscopy. Both the enantiomers of complex 2 were present in a dynamic equilibrium in solution and studied by variable temperature 1H NMR spectroscopy. Similar to the chiral complex, the corresponding ligand H2L2 also exhibited chirality as shown by its crystal structure and the two ligand enantiomers participated in a very fast dynamic interconversion, which became slower upon metalation. [ABSTRACT FROM AUTHOR]

The synthesis of a series of mononuclear, dicationic CoII funnel complexes is reported herein. Three ligands Calix‐TMPAX present a calix[6]arene cone closed at its small rim by a tris(2‐pyridylmethyl)amine (TMPA) unit and differ by the nature of three cavity walls, anisole, phenol or quinone. The X‐ray diffraction structure of [CoII(MeCN)Calix‐TMPAOMe](ClO4)2 displays a trigonal bipyramidal geometry, with Co bound to all 4 nitrogen atoms of the TMPA cap, and to one MeCN guest molecule buried inside the calixarene cavity. All complexes were fully characterized in solution as high spin 5‐coordinate species using various techniques, including 1H NMR spectroscopy. For comparison purpose, an analogous CoII complex based on the TMPACH2OH ligand, devoid of a calixarene core, was synthetized. Its X‐ray structure shows a dicationic 7‐coordinate cobalt(II) center in the N4O3 environment provided by the ligand, leaving no space for exogenous ligand binding. This contrasts with the 5‐coordinate complexes obtained with the calix‐ligands that allow guest‐ligand binding and exchange. A brief overview of the coordination properties of the calix‐complexes, compared to those obtained with TMPA ligands, devoid of a cavity, highlights major differences in terms of complexation kinetics, geometry, coordination to the labile site, anion affinity, nuclearity, and stability. [ABSTRACT FROM AUTHOR]

Three new tridentate copper(II) N-heterocyclic carbene (NHC) complexes have been obtained and characterized with symmetrical C-4 substitutions on their pendent pyridine rings. Substitutions including methyl (Me), methoxy (OMe), and chloro (Cl) groups, which extend the library pincer Cu-NHC complexes under investigation, modify the impact of pyridinyl basicity on NCN pincer complexes. Both ligand precursors and copper(II) complexes are characterized using a range of techniques, including nuclear magnetic resonance (NMR) spectroscopy for 1H, 13C, 31P, and 19F nuclei, electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography, cyclic voltammetry, and UV-Vis spectroscopy. The pyridine substitutions lead to minimal changes to bond lengths and angles in the X-ray crystal structures of these related complexes; there is a pronounced impact on the electrochemical behavior of both the ligand precursors and copper complexes in the solution. The substitution in the pyridinyl units of these complexes show an impact on the catalytic reactivity of these complexes as applied to a model C–N bond-forming reaction (CEL cross-coupling) under well-established conditions; however, this observation does not correlate to the expected change in basicity in these ligands. [ABSTRACT FROM AUTHOR]

A novel tridentate ligand featuring an acridine core and pyrazole rings, namely 2,7- di-tert-butyl-4,5-di(pyrazol-1-yl)acridine, L, was designed and used to create two ruthenium(II) complexes: [RuL2](PF6)2 and [Ru(tpy)L](PF6)2. Surprisingly, the ligand adopted different coordination modes in the complexes: facial coordination for the homoleptic complex and meridional coordination for the heteroleptic complex. The electronic absorption and electrochemical properties were evaluated. Although both complexes exhibited favorable electronic properties for luminescence, neither emitted light at room temperature nor at 77 K. This study highlights the complex interplay between ligand design, coordination mode, and luminescence in ruthenium(II) complexes. [ABSTRACT FROM AUTHOR]

In 1977 Weiss and Grimes, by means of mass spectrometry and 1H and 11B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η5‐C5H5)Fe(B5H10), isoelectronic with ferrocene. In this work, by means of high‐level quantum‐chemical computations, we confirm the experimental structures of the two isomers with their corresponding energies, and assign the reported 1H and 11B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the B5H10− ligand – an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion C5H5− – when attached to the (η5‐C5H5)Fe+ moiety, thus resulting in a more stable ferraborane isomer II. [ABSTRACT FROM AUTHOR]

In 1977 Weiss and Grimes, by means of mass spectrometry and 1H and 11B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η5‐C5H5)Fe(B5H10), isoelectronic with ferrocene. In this work, by means of high‐level quantum‐chemical computations, we confirm the experimental structures of the two isomers with their corresponding energies, and assign the reported 1H and 11B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the B5H10− ligand – an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion C5H5− – when attached to the (η5‐C5H5)Fe+ moiety, thus resulting in a more stable ferraborane isomer II. [ABSTRACT FROM AUTHOR]

We report the stepwise synthesis of a novel series of heterometallic gold(I)/palladium(II) complexes supported by heteroditopic imidazol‐2‐ylidene/triazol‐5‐ylidene ligands. All new compounds were characterized by means of 1H and 13C NMR spectroscopy, melting points, and elemental analyses. The versatility of the ligand platforms, additionally allows for the preparation of cationic chelate biscarbenic palladium(II) complexes through full deprotonation of the mixed azolium precursors. Characterization studies were completed by the determination of the molecular structures of some synthetic intermediates. The new biscarbenic palladium(II) complexes were tested as catalysts in the cross‐coupling of boronic acid to a variety of chloroarenes and the hydrosilylation of terminal alkynes. Both catalytic processes provide good to excellent yields under low catalyst loadings. [ABSTRACT FROM AUTHOR]

From the perspective of possible antiviral and antibacterial activity of vanadium‐based complexes, we report the synthesis of new Schiff base ligand (L4) and a new Schiff‐base‐vanadium complex (C2). Both the ligand and the complex were characterized by Fourier transform infrared spectroscopy and Nuclear magnetic resonance techniques. Single‐crystal X‐ray Diffraction analysis has been used to confirm the structure of ligand L4 and complex C2. In addition, L1–4 and C1–3 were tested for their antibacterial effects against Escherichia coli and Staphylococcus aureus. Among the compounds, L2 demonstrated the most potent inhibition of both bacteria, exhibiting the lowest values for minimum inhibitory concentration (CMI) and minimum bactericidal concentration (CMB) (CMI = 0.16, CMB = 0.31 against E. coli, and CMI = CMB = 0.16 against S. aureus). Additionally, L2 produced the largest inhibition zones with diameters of 15.5 ± 0.15 against E. coli and 14.5 ± 0.04 against S. aureus. Furthermore, the antiviral efficacy of L1, L2, L4, C1, C2, and C3 against RNA viruses was assessed. C2 and C3 exhibited the most potent antiviral activity among the tested compounds. [ABSTRACT FROM AUTHOR]

Carboxylate complexes have risen to prominence in the field of water oxidation catalysis. Here for the first time we use the higher valence of phosphinates [P(V)] relative to that of carboxylates [C(IV)] to increase ligand denticity. We describe the synthesis and characterization of a new dianionic pentadentate ligand, bcpq2− that contains a tridentate 2,2'‐bipyridine‐6‐carboxylato moiety, in addition to a 6'‐phosphinato substituent that acts as fourth ligand and bears a side arm containing a quinoline, the fifth ligand. The new bcpq ligand allows formation of [Ru(II)(bcpq)(L)] (2 a–b, L=picoline or isoquinoline) and in preliminary results, of a Co(II) complex. NMR spectroscopy, X‐ray diffraction, cyclic voltammetry, differential pulse and square wave voltammetry were used to characterize 2 a–b, with 2 b being characterized more extensively as a catalyst. Bulk electrolysis over 15 h at pH 7 was also used, showing that 2 b gave 100±5 % faradaic efficiency and remained completely homogeneous, whereas 1 b was no longer homogeneous; this comparison conclusively shows the advantage of the added denticity in the electrocatalytic context. Replacing carboxylate with P(V) phosphinate with an added arm may be used in other ligand systems to enhance the durability of homogeneous catalysts. [ABSTRACT FROM AUTHOR]

The new diiron(I) complexes [Fe2Cp2(μ‐CO){μ‐k3C,kN‐C(R1)C(R2)C(CN)NMe(R)}], 3 a–o (R=alkyl or 4‐C6H4OMe; R1=alkyl, aryl, ferrocenyl (Fc), thiophenyl, CO2Me or SiMe3; R2=H, Me or CO2Me) were synthesized in moderate to high yields from the thermal decarbonylation of the bis‐carbonyl precursors 2 a–o, and were structurally characterized by IR and NMR spectroscopy, and single crystal X‐ray diffraction in four cases. Electrochemical behavior of one complex was also investigated. Complexes 3 a–o comprise a highly functionalized, multisite amino‐(cyano)allylidene ligand, including metal coordination of a tertiary amine group. Selected complexes displayed negligible to moderate catalytic activity in CO2/propylene oxide coupling, working under ambient conditions. Additionally, they were investigated as catalysts for the conversion of benzaldehyde to the corresponding borate ester 6 a, using pinacolborane (HBpin) as the borylating agent. Most complexes achieved good conversions at room temperature with 1 % catalyst loading, and data highlight the significant influence of the multisite ligand substituents on the catalytic performance. Notably, complex 3 m (featuring R=4‐methoxyphenyl, R1=Fc, R2=H) displayed the highest activity and effectively catalyzed the hydroboration of various aldehydes and ketones. A plausible mechanistic cycle involves metal coordination of the carbonyl substrate, its activation being possibly facilitated by intramolecular interactions. [ABSTRACT FROM AUTHOR]

While π‐complexes of C=C bonds are ubiquitous in organometallic chemistry, analogous complexes of the isoelectronic but strongly polarized B=N double bond of aminoboranes are extremely scarce. To address this gap, a diphosphine‐aminoborane ligand (PhDPBAiPr) is introduced and its coordination with group 10 metals is investigated. The B=N bond does not coordinate to the metal in Pt(0) and Pd(II) complexes. In contrast, side‐on coordination of the B=N bond is observed in the Ni(0) complex (PhDPBAiPr)Ni(NCPh), and the X‐ray crystal structure reveals B−N bond elongation compared to the free ligand. The choice of co‐ligand strongly influences the presence or absence of side‐on coordination at Ni(0) as evidenced by NMR spectroscopy. While the B=N π‐complex is geometrically similar to C=C analogues, a bonding analysis reveals that the interaction of the B=N motif with the electron‐rich Ni(0) center is best described as 3c4e hyperbond, in which Ni and N are competing for the empty orbital on B. [ABSTRACT FROM AUTHOR]

A low‐valent GaI complex with the superbulky β‐diketiminate ligand DIPePBDI (HC[C(Me)N−DIPeP]2, DIPeP=2,6‐C(H)Et2‐phenyl)) was obtained by reduction of (DIPePBDI)GaI2 (1) with KC8 in toluene. Considering that (BDI)GaI and analogue (BDI)AlI complexes are prone to decomposition and can generally only be obtained in low yields (20–40 %), the quantitative formation of (DIPePBDI)GaI (2) is remarkable and no doubt related to its excellent thermal stability even in refluxing toluene. Although the low‐valent metal center in 2 is sterically protected by the superbulky DIPePBDI ligand, it is readily oxidized by N2O to give intermediate (DIPePBDI)Ga=O which readily decomposed by abstracting a proton from the backbone Me‐substituent. Reaction with trimethylsilyl azide gave an intermediate imido complex (DIPePBDI)Ga=N(SiMe3)2 which reacted with a second equivalent of Me3SiN3 to a mixture of an azide/amido complex (DIPePBDI)GaN3[N(SiMe3)2] (4) and a tetrazagallole complex (DIPePBDI)Ga[N4(SiMe3)2] (5) in a 1 : 2 ratio. Whereas the azide/amido complex 4 could be structurally characterised, the tetraazagallole complex 5 was identified by NMR spectroscopy. DFT calculations on (DIPePBDI)GaI (2) and its reaction products complement this study. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of three families of coordination complexes synthesized from 4′‐phenyl‐2,2′:6′,2′′‐terpyridine (8, Ph‐TPY), 4′‐(4‐chlorophenyl)‐2,2′:6′,2′′‐terpyridine (9, ClPh‐TPY) and 4′‐(4‐methoxyphenyl)‐2,2′:6′,2′′‐terpyridine (10, MeOPh‐TPY) ligands with the divalent metals Co2+, Fe2+, Mn2+ and Ni2+ are reported. The compounds were synthesized from a 1:2 mixture of the metal and ligand, resulting in a series of complexes with the general formula [M(R‐TPY)2](ClO4)2 (where M = Co2+, Fe2+, Mn2+ and Ni2+, and R‐TPY = Ph‐TPY, ClPh‐TPY and MeOPh‐TPY). The general formula and structural and supramolecular features were determinated by single‐crystal X‐ray diffraction for bis(4′‐phenyl‐2,2′:6′,2′′‐terpyridine)nickel(II) bis(perchlorate), [Ni(C21H15N3)2](ClO4)2 or [Ni(Ph‐TPY)2](ClO4)2, bis[4′‐(4‐methoxyphenyl)‐2,2′:6′,2′′‐terpyridine]manganese(II) bis(perchlorate), [Mn(C22H17N3O)2](ClO4)2 or [Mn(MeOPh‐TPY)2](ClO4)2, and bis(4′‐phenyl‐2,2′:6′,2′′‐terpyridine)manganese(II) bis(perchlorate), [Mn(C21H15N3)2](ClO4)2 or [Mn(Ph‐TPY)2](ClO4)2. In all three cases, the complexes present distorted octahedral coordination polyhedra and the crystal packing is determined mainly by weak C—H...π interactions. All the compounds (except for the Ni derivatives, for which FT–IR, UV–Vis and thermal analysis are reported) were fully characterized by spectroscopic (FT–IR, UV–Vis and NMR spectroscopy) and thermal (TGA–DSC, thermogravimetric analysis–differential scanning calorimetry) methods. [ABSTRACT FROM AUTHOR]

A study of the liquid–liquid extraction of ReO4− anions from hydrochloric acid solutions using the ionic liquid Aliquat 336 (QCl: trialkyl(C8–C10)methylammonium chloride) via the well-known method of slope analysis along with the determination of the process parameters is presented. This study employs CCl4, CHCl3 and C6H12 as diluents. This study was carried out at room temperature (22 ± 2) °C and an aqueous/organic volumetric ratio of unity. The ligand effect on the complexation properties of ReO4− is quantitatively assessed in different organic media. The organic extract in chloroform media is examined through 1H, 13C and 15N NMR analysis as well as the HRMS technique and UV-Vis spectroscopy in order to view the anion exchange and ligand coordination in the organic phase solution. Final conclusions are given highlighting the role of the molecular diluent in complexation processes and selectivity involving ionic liquid ligands and various metal s-, p-, d- and f-cations. ReO4− ions have shown one of the best solvent extraction behaviors compared to other ions. For instance, the Aliquat 336 derivative bearing Cl− functions shows strongly enhanced extraction as well as pronounced separation abilities towards ReO4−. [ABSTRACT FROM AUTHOR]

Alkaloids are among the most important and best-known secondary metabolites as sources of new drugs from medicinal plants and marine organisms. A phytochemical investigation of the whole plant of Crinum asiaticum var. sinicum resulted in the isolation of seven alkaloids (1–7), including one new dimeric compound, bis-(-)-8-demethylmaritidine (1). Their structures were elucidated using NMR and HR-ESI-MS. The absolute configuration of new compound 1 was established by circular dichroism spectroscopy. All isolated compounds were evaluated for their inhibitory effects on acetylcholinesterase (AChE) activity in vitro. Among them, compound 1 exhibited the most potent AChE inhibition. Moreover, molecular docking and molecular dynamics simulations were carried out for the most active compound to investigate their binding interactions and dynamics behavior of the AChE protein-ligand complex. Therefore, compound 1 may be a potential candidate for effectively treating Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Six red-light-emitting Eu(III) complexes having a β-hydroxyketone as ligand and heterocyclic ring containing compounds as ancillary ligands were synthesized to explore their use in displays and optoelectronics. The coordinating behavior of complexes was determined by various techniques such as FTIR (Fourier transform infrared), 1H-NMR (Nuclear magnetic resonance), and 13C-NMR that establishes a bonding of ligand and ancillary ligand with the Eu(III) ion. Morphology and purity were investigated through XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDS (energy-dispersive X-ray spectroscopy) analyses that suggest semicrystalline and pure complex formation. Thermal analysis of complexes by TGA/DTG (thermogravimetric/derivative thermogravimetric) indicates that complexes are stable upto 200 ºC temperature making them suitable for use in display devices. Analysis of the photophysical properties was carried out in both solid and solution states using PL (photoluminescence) studies, color parameters, J–O (Judd–Ofelt) analysis and bandgap. Most emissive transition (5D0 → 7F2) is responsible for the red emission in the complexes. The CIE (Commission International de I'Eclairage) coordinates of complexes also indicate the red emission on UV excitation. The bandgap which was obtained in the range of 2.54–3.02 eV reveals the semiconducting behavior of complexes. Values of J–O parameters and Ω2 in the complexes reflect asymmetric chemical environment around Eu (III) and less covalence and the Ω4 indicates that complexes are less rigid. Bandgap calculated through DFT (density function theory) for complexes is in range of 2.37–2.77 eV, and intensity parameters (J–O), energy transfer rates, and spherical coordinates were determined by LUMPAC software. The computational data are in good harmony with the experimental data. Further biological aspects of complexes were studied using antioxidant and antimicrobial studies. [ABSTRACT FROM AUTHOR]

Select triphenyl stannanes bearing either a formally sp2 or sp3 hybridized amine, viz 2-(pyC2H4)SnPh3 (2: py = pyridinyl), 4-(pyC2H4)SnPh3 (3), 2-(pzC2H4)SnPh3 (4: pz = pyrazyl), and Me2N(CH2)3SnPh3 (6), were prepared and characterized by NMR spectroscopy (119Sn, 13C, 1H), and additionally, in the case of 2, by single crystal X-ray diffraction. Bromination of 2 to yield 2-(pyC2H4)SnPhBr2 (8) was achieved in good yield. X-ray crystallographic analysis of 8 revealed two unique molecules with 5-coordinate Sn centers featuring Sn-N distances of 2.382 (5) and 2.363 (5) Å, respectively. The calculated structures of the non- and hypercoordinating C,N-stannanes (1–9) were in good agreement with available crystallographic data. The relative stabilities of hyper- and non-hypercoordinating conformers obtained from conformational sampling were determined by comparison with reference conformers and by natural bond orbital (NBO) energetic analyses. Reduction of 8 to the dihydride species, 2-(pyC2H4)SnPhH2 (9), and subsequent conversion to the polystannane, -[2-(pyC2H4)SnPh]n- (15), by transition metal-catalyzed dehydropolymerization was also achieved. Evidence for the decomposition of 15 into a redistributed distannoxane, {2-(pyC2H4)SnPh2}2O (16), was also observed. [ABSTRACT FROM AUTHOR]

Reaction of (arylimido)niobium(V) tris(diethylamide) complexes, Nb(NAr)(NEt2)3, prepared by treating Nb(NAr)Cl3(dme) (dme=1,2‐dimethoxyethane) with 3.0 equiv. of LiNEt2, with 1.0 equiv. of phenol afforded the corresponding phenoxide complexes, Nb(NAr)(NEt2)2(O‐2,6‐R2C6H3) [1 a–c, 2 a–c; Ar=2,6‐Me2C6H3 (1) 2,6‐iPr2C6H3 (2); R=tBu (a), iPr (b), Me (c)], which were identified by NMR spectroscopy, elemental analysis and the structures for 2 b, c were determined by X‐ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

The Сd(II) complexes with redox amphoteric 2,6-di-(tert-butyl)-4-((2-hydroxyphenyl)imino)cyclohexa-2,5-dienone ligands L1 and L2 (adducts I, II, and III) are synthesized. The structures of coordinated complexes I, II, and III are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 1838319 (II) and 1838310 (III)) and confirmed by the 1Н, 13С, and 113Cd NMR spectroscopy (for complexes I and III) and IR spectroscopy data. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of six new iridium(III) complexes of stoichiometry, [Ir(Cp*Cl2(2abn)] (1), [Cp*Cl2Ir(µ-2abn)IrCl2Cp*] (2), [IrCp*Cl2(4abn)] (3), [Cp*Cl2Ir(µ-4abn)IrCl2Cp*] (4), [IrCp*Cl2(2-ampy)] (5) and [IrCp*Cl2(4-ampy)] (6) (Cp* =pentamethylcyclopentadienyl anion; 2- and 4abn = 2- and 4-aminobenzonitrile, respectively; 2- and 4-ampy = 2- and 4-aminopyridine, respectively). The new compounds have been prepared from [(IrCp*Cl)(µ-Cl)]2 by the addition of the ligands in appropriate proportions in dichloromethane and then precipitated using hexane. They have been characterized by C, H, N elemental analyses, thermogravimetric analysis, infrared spectroscopy,1H and 1H-1H Cosy nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry (ESI), and in the case of 1 and 5, by single-crystal X-ray diffraction, confirming the proposed structure. To the best of our knowledge, 1 is the first reported crystal structure of a neutral Cp*Ir complex with a benzonitrile-based ligand coordinated through the -CN group. The cytotoxic behavior of all compounds was studied against HeLa cells, but no measurable biological activity could be established. [ABSTRACT FROM AUTHOR]

The coordination and extraction properties of two related tripodal ligands differed by types of addition of the triazole fragment and linker length in the {2-[(4-Ph-1,2,3-triazol-1-yl)CH2CH2O]C6H4}3P(O) (L1) and {2-[(1-Ph-1,2,3-triazol-4-yl)CH2O]C6H4}3P(O) (L2) are compared. The structures of the complexes [Lа(NO3)3L1] (I) and [Lu(NO3)3L1] (II) are studied in the solid phase (elemental analysis, IR and Raman spectroscopy) and in solutions (IR and multinuclear 1H, 13C, and 31P NMR spectroscopy). A normal coordinate analysis at the TPSS-D4/Def2-SVP level is performed for an isolated molecule of the model complex [La{P(O),N3,N2-L3}(O,O-NO3)3] (L3 = {2-[(4-Me-1,2,3-triazol-1-yl)CH2CH2O]C6H4}3-P(O)). According to the set of spectral and quantum chemical data, ligand L1 exhibits the tridentate P(O),N2,N2 coordination in lanthanide complexes I and II. These are neutral complexes in the solid state and in CD3CN solutions, and the dynamic equilibrium of the neutral and ionic complexes is observed in CDCl3. Unlike ligand L1, ligand L2 exhibits the tetradentate P(O),N3,N3,N3 coordination in the [Ln(NO3)3L2] complexes with the same metals (Ln = La3+, Lu3+) in solutions. The efficiency of extraction of microquantities of f elements from the aqueous phase to 1,2-dichloroethane by compounds L1 and L2 is discussed in comparison with the structures of the complexes of both ligands in solutions. [ABSTRACT FROM AUTHOR]

The tremendous importance of dirhodium paddlewheel complexes for asymmetric catalysis is largely the result of an empirical optimization of the chiral ligand sphere about the bimetallic core. It was only recently that a H(C)Rh triple resonance 103Rh NMR experiment provided the long‐awaited opportunity to examine – with previously inconceivable accuracy – how variation of the ligands impacts on the electronic structure of such catalysts. The recorded effects are dramatic: formal replacement of only one out of eight O‐atoms surrounding the metal centers in a dirhodium tetracarboxylate by an N‐atom results in a shielding of the corresponding Rh‐site of no less than 1000 ppm. The current paper provides the theoretical framework that allows this and related experimental observations made with a set of 19 representative rhodium complexes to be interpreted. In line with symmetry considerations, it is shown that the shielding tensor responds only to the donor ability of the equatorial ligands along the perpendicular principal axis. Axial ligands, in contrast, have no direct effect on shielding but may come into play via the electronic cis ${cis}$ ‐effect that they exert onto the neighboring equatorial sites. On top of these fundamental interactions, charge redistribution within the core as well as the electronic trans ${trans}$ ‐effect of ligands of different donor strengths is reflected in the recorded 103Rh NMR shifts. [ABSTRACT FROM AUTHOR]

The report concerns expansion of the previously developed M-[O,N,C] [pyridine-2-phenolate-6-(σ-aryl)] catalyst system into rigid, coplanar bimetallic assemblies, which afford metal–metal distances that are predetermined yet amenable for cooperativity, as well as locked-in "syn" orientation of binding sites that offer the same direction of access for substrates. The binuclear complexes are generated in a regioselective manner to yield para hydrogen atoms (not ortho) at the central μ-aryl moiety, and have been characterised by multinuclear NMR spectroscopy. The "anti" (showing opposite directions of access) and mononuclear analogues have also been prepared for comparison purposes. Six syn-type bimetallic derivatives of Ti, Zr and Hf have been characterised by X-ray crystallography, to reveal metal–metal separations of 6.3–6.7 Å. For ethylene and ethylene/1-octene polymerisation reactions in conjunction with trityl borate, the syn-Ti2 catalysts display superior efficiencies and produced polymers with higher Mw values than for the anti and mono-Ti congeners, thus indicating the possibility of favourable enchainment interactions and cooperative reactivity. [ABSTRACT FROM AUTHOR]

Metal complexes, which, under physiologic conditions, show redox properties and are able to bind to DNA, are great tools to cleave the DNA chain. This aspect is of great importance for their use as antineoplastic drugs. We synthesized ligands derived from short-chain amino acids and from salicylaldehyde. The prepared ligands of the type of reduced Schiff bases were subsequently used for the preparation of copper(II) complexes. The aim of the study was in vitro testing of copper(II) complexes, where it was confirmed that they are capable of cleaving DNA. Their cytotoxic activity was also confirmed by the resazurin redox method on Saccharomyces cerevisiae based on preserved healthy mitochondrial function. [ABSTRACT FROM AUTHOR]

We report a class of compounds in which both PIII−X and PI forms featuring the same ligand are stable and readily cycled with each other. A series of PIII−X (X=Cl, Br, I) dicationic triflate salts supported by benzyl‐ and allyl‐substituted 2,6‐bis(benzimidazole‐2‐yl)pyridine (BZIMPY) ligands is synthesized. Surprisingly, treatment of these with R3PO (R=Et, Oct) results in reduction to BZIMPY‐ligated PI monocationic triflate salts while treatment with Ph3P reduces but also substitutes the compound to produce Ph3P‐BZIMPY‐ligated PI dicationic triflate salts. The mechanisms of these surprising reductions are probed experimentally and rationalized computationally. The PIII−X dications are shown to be strong Lewis acids both experimentally and computationally and to readily behave as X+, PX, and P+ transfer agents in reactions with phosphines, NHCs, and diazabutadienes. The PI mono‐ and dications are shown to be very effective P+ transfer agents when treated similarly. Oxidation from a monocationic PI salt back to the dicationic PIII−X (X=Cl, Br) salt was achieved by treatment with N‐chlorosuccinimide (NCS) or N‐bromosuccinimide (NBS). Full characterization is reported using multinuclear nuclear magnetic resonance spectroscopy, elemental analysis, and single‐crystal X‐ray diffractometry where suitable crystals were isolated. [ABSTRACT FROM AUTHOR]

1,2-Bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene (ArBIG-bian) reacts with an excess of ytterbium metal in 1,2-dimethoxyethane (DME) to afford solvent-free ytterbium complex of ArBIG-bian dianion, [(ArBIG-bian)Yb]. The reaction of [(ArBIG-bian)Yb] with 2,2′-bipyridine (bpy) (1 to 2) in DME proceeds with the electron transfer from the metal to the bpy and results in ytterbium(III) derivative [(ArBIG-bian)Yb(bpy)2], containing both neutral and radical-anionic bpy ligands. The newly prepared compounds were characterized by IR, NMR spectroscopy. The molecular structure of [(ArBIG-bian)Yb(bpy)2] was determined by single crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

"2+1B" tricarbonyl complexes of the general formula [M(CO)3(N^N)CN(CH2)4CH(COOMe)SC10H21]-ClO4, where M = 99mTc or Re, N^N = 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), were prepared by the reaction of [M(CO)3(N^N)(MeOH)]ClO4 with methyl 2-(decylthio)-6-isocyanohexanoate in methanol. The rhenium complexes were isolated and characterized by 1H NMR and IR spectroscopy. The formation of technetium-99m complexes was confirmed by HPLC. The lipophilicity of the technetium complexes was measured. [ABSTRACT FROM AUTHOR]

By exploiting coordination‐driven self‐assembly, high yields of two 818 molecular metalla‐knots could be obtained using a thiazole‐moiety‐containing asymmetric dipyridyl ligand 2‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylethynyl)benzo[d]thiazole (L1), as confirmed using X‐ray crystallographic analysis, electrospray ionization‐time‐of‐flight/mass spectrometry (ESI‐TOF/MS), and detailed liquid‐state nuclear magnetic resonance (NMR) spectroscopy. To modulate the self‐assembled structures, m‐chloroperbenzoic acid (m‐CPBA) was utilized to oxidize thiazole‐based ligand L1 to N‐thiazole‐oxide‐based ligand 2‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylethynyl)benzo[d]thiazole 3‐oxide (L2), which enabled the selective construction of the corresponding tetranuclear macrocycles. Notably, two molecular metalla‐knots could be topologically transformed from 818 knots to simple monocycles because the L1 alkyne bond was inert toward m‐CPBA, as confirmed by liquid‐state NMR spectroscopy, ESI‐TOF/MS, and elemental analysis. [ABSTRACT FROM AUTHOR]

Zinc complexes X2Zn(L) (X = Et, OAc, OC(O)CF3)) were synthesized in which 1,10-phenanthrolines containing substituents at positions 2, 4, 7, and 9 were used as bidentate ligand L. The structures of the complexes were confirmed by NMR spectroscopy and elemental analysis. The structures of three complexes were investigated by X-ray diffraction analysis. The complexes have been studied as initiators of ε-caprolactone, L- and rac-lactides polymerization. [ABSTRACT FROM AUTHOR]

A new series of protic amines containing cyclic amidine substituents in their side arms were synthesised from iminodiacetonitrile and 1,2- and 1,3-diamines. These amidine-anchored protic amines were treated with MnBr(CO)5 resulting in the formation of cationic mononuclear Mn(I) complexes with a facial coordination mode. Crystallographic analysis revealed that the C–O bond lengths of the carbonyl ligands, located at the trans position to the amidine, were marginally longer compared to those to typical phosphine- and other N(sp2)-anchors. This observation suggests that the amidine side arm possesses a strong electron donating ability. In the catalytic application of transfer hydrogenation of acetophenone, a Mn complex featuring a six-membered ring amidine anchor showed relatively high activity, possibly due to a high electron density of the metal, as estimated from the NH signal in the proton nuclear magnetic resonance (1H NMR) spectroscopy. Furthermore, cyclic voltammetry measurements revealed that the redox properties varied depending on the structure of amidine. Specifically, a Mn complex with readily accessible electron acceptance exhibited a significant increase in current under CO2. This behaviour demonstrated catalytic activity in the electrochemical reduction of CO2. [ABSTRACT FROM AUTHOR]

A series of thirty novel tetracarboxylatoplatinum(IV) complexes in trans-configuration featuring combinations of mixed ammine, methylamine, dimethylamine, and cyclopentylamine ligands as well as acetato/propanoato and trifluoropropanoato ligands was synthesised. The platinum(IV) complexes were characterised by one- and two-dimensional multinuclear NMR spectroscopy (1H, 13C, 15N, 19F, 195Pt), ESI-MS, elemental analysis, and X-ray diffraction. Additional parameters such as reduction behaviour and lipophilicity were measured via NMR spectroscopy and RP-HPLC, revealing slow reduction and a broad spectrum of log kw values in line with the respective ligand combination. In order to determine structure–activity relationships, cytotoxic activity was evaluated via the MTT assay in three human cancer cell lines (CH1/PA-1, ovarian teratocarcinoma, SW480, colon adenocarcinoma, A549, non-small-cell lung carcinoma). The induction of apoptosis and necrosis was determined in SW480 cells via the flow-cytometric annexin V/PI assay. In general, a tendency of higher lipophilicity leading to higher cytotoxicity was noticed. In contrast, lipophilicity alone plays a subordinate role for the induction of apoptosis, which strongly depends on the combination of am(m)ine and trifluoropropanoato ligands. [ABSTRACT FROM AUTHOR]

Considering necessity of application of Schiff base ligands, containing hydrazone moiety, there were synthesized 2-hydroxy-1-naphtaldehyde acetylhydrazone and its metal complexes. A tridentate ligand with hydrazone moiety was synthesized on the basis of acetylhydrazine and 2-hydroxy-1-naphthoic aldehyde. The characterization and structure of it was identified by IR, UV- and NMR-spectroscopy. The electronic absorption spectrum of the ligand shows absorption bands in the range of max 237-320 nm. 1H NMR (300 MHz, CD4O):  6.90-8.21, 9.31, 10.52. Recrystallization occured from an ethanol. Melting point of the ligand was 21530C. Yield was 80%. There were acquired complexes of the Schiff base ligand with zinc and manganese. Colored solid complexes of zinc and manganese (II), respectively, yellow and brown colors with the obtained ligand were synthesized in ethanol medium. Yield for complexes was 75 and 73 %, respectively for zinc and manganese complex. The molar ratio of ligand and metal in the complex was 2:1. The structure of the complexes was confirmed by elemental analysis, IR-, UV-, and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] An unusual neutral dinuclear palladium(II) complex with two head-to-head orientated μ- P , S -bridging ligands was obtained by the reaction of Pd(MeCN) 2 Cl 2 with (1 R ,5 R)-3-(4-phenylthiobutoxy)-2,4-diphenyl-2,4-diaza-3-phospha-bicyclo[3.4.0]nonane. The dimeric structure of the complex in the solid state and in solution was thoroughly confirmed using appropriate analytical techniques: single crystal X-ray diffraction analysis, HRMS, FTIR and NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Ruthenium complexes of phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh2C(=O)NHR}Cl2; R = iPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh2C(=O)N(R)C(=O)N(H)R}Cl2; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl2]2 (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single-crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ2-P,N-PPh2C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The biomolecular interactions of two previously reported cycloplatinated complexes, [Pt(C^N)(SMe2)(OCOCF3)] (C^N = deprotonated benzo[h]quinoline (bhq), 1, or deprotonated 2-phenylpyridine (ppy), 2), with bovine serum albumin (BSA) were investigated using various spectroscopic techniques. Structural characterization of 1 and 2 by NMR, UV-vis spectroscopies and conductivity measurements in aqueous media revealed that the TFAc functions as a leaving group ligand and is rapidly replaced by water molecules to form cationic cycloplatinated complexes having an aqua ligand, [Pt(C^N)(SMe2)(H2O)]+[CF3COO]−. Fluorescence titration of BSA indicated a strong binding interaction between Pt(II) compounds and protein with a static quenching mechanism. The thermodynamic parameters (ΔH°, ΔG° and ΔS°) showed that the binding was exothermic, involving main noncovalent hydrophobic forces and ionic interactions. As revealed by the displacement experiment, while 1 could bind to subdomain IIIA (site II) of albumin, the binding sites of 2 were mostly located at subdomain IIA (site I). The synchronous fluorescence spectra indicate that the cycloplatinated compounds induce structural changes in the protein structure. Moreover, far-UV CD spectroscopy is in agreement with a reduction of the α-helix content of albumin through binding. Further evidence for noncovalent association was obtained from inductively coupled plasma-optical emission spectroscopy (ICP-OES). In addition, the cytotoxicity investigation of 1 as a model complex against two human leukemic cancer cell lines (K562 and HL-60), MCF-7 (human breast adenocarcinoma), U-87MG (human glioblastoma cell line) and HT-29 (human colorectal adenocarcinoma cell line) suggested that 1 is more cytotoxic than cisplatin against HL-60 and generally toxic toward K562, MCF-7 and U-87MG. Finally, the quantitative structure–activity relationship (QSAR) was applied to correlate the structure of some cycloplatinated complexes including 1 and 2 with the SA albumin binding constant. [ABSTRACT FROM AUTHOR]

Several trivalent and pentavalent vanadium complexes bearing 8-anilide-5,6,7-trihydroquinoline ligands were synthesized. These vanadium complexes were identified by elemental analysis, FTIR spectroscopy and NMR. Single crystals of trivalent vanadium complexes V2, V3′, and V4 and pentavalent vanadium complexes V5 and V7 were further obtained and identified by X-ray single crystal diffraction. In addition, the catalytic performance of these catalysts was adjusted by controlling the electronic and steric effects of substituents in the ligands. In the presence of diethylaluminium chloride, complexes V5–V7 displayed high activity (up to 82.8 × 106 g molV−1 h−1) and good thermal stability toward ethylene polymerization. In addition, the copolymerization ability of complexes V5–V7 was evaluated, and complexes V5–V7 displayed high activity (up to 105.6 × 106 g molV−1 h−1) and high copolymerization ability toward ethylene/norbornene copolymerization. By adjusting the polymerization conditions, copolymers with norbornene insertion ratios of 8.1%–30.9% can be obtained. Complex V7 was further studied for ethylene/1-hexene copolymerization, and the obtained copolymer displayed a moderate 1-hexene insertion ratio of 1.2%. Complex V7 displayed high activity and high copolymerization ability while having thermal stability. The results showed that 8-anilide-5,6,7-trihydroquinoline ligands with fused rigid-flexible rings were beneficial for vanadium catalysts. [ABSTRACT FROM AUTHOR]

New tetraphosphoryl tripodal ligands on the triphenylphosphine oxide platform [2-Ph2P(O)(CH2)nOC6H4]3PO with different linker length (n = 3, 4) were synthesized. Their composition and structure were determined by elemental analysis, IR and multinuclear (1H, 13C, and 31P) NMR spectroscopy, and X-ray diffraction analysis. Extraction properties of the ligands were studied using the example of extraction of microamounts of f-elements from an aqueous phase into 1,2-dichloroethane. [ABSTRACT FROM AUTHOR]

A series of ruthenium bis(σ‐B−H) borate complexes 1–4 have been prepared by a salt‐elimination protocol using lithium monoaryl trihydroborates Li[ArBH3] (R=Ph, 3,5‐(CF3)2C6H3, o‐tol or Mes) and the corresponding metal halide Cp*Ru(PCy3)Cl. All of these bis(σ‐B−H) borate complexes are stable at room temperature and isolated in good yields (70–92 %). Additionally, treatment of 4 with the hydride abstracting agent B(C6F5)3 generated rare cationic bis(σ‐B−H) borane complex 5. Crystallographic characterization data are provided for 3 and 5. All these new complexes were fully characterized by multinuclear NMR spectroscopy and elemental analysis. [ABSTRACT FROM AUTHOR]

Five dinuclear copper(I) complexes of the type [Cu{κN,κN′-5-R-NC4H2-2-C(H)＝N(2,6-iPr2C6H3)}]2 (1a–e; R = 2,4,6-iPr3C6H2 (a), R = 2,6-Me2C6H3 (b), R = 3,5-(CF3)2C6H3 (c), R = 2,6-(OMe)2C6H2 (d), R = CPh3 (e)) were prepared by the reaction of the respective 5-R-2-iminopyrrolyl potassium salts KLa–e and [Cu(NCMe)4]BF4 in moderate yields. These new copper(I) complexes were characterized by NMR spectroscopy, elemental analysis and, in selected cases, by single crystal X-ray diffraction and their structural and electronic features further analyzed by DFT calculations and cyclic voltammetry, respectively. X-ray diffraction studies reveal dimeric Cu structures assembled by 2-iminopyrrolyl bridging ligands adopting a transoid conformation (complexes 1a and 1d), while complexes 1c and 1e displayed a cisoid conformation of those moieties, with respect to the Cu(I) centers. Additionally, VT-1H NMR and 1H–1H NOESY NMR experiments on complexes 1a–e exhibited complex fluxional processes in solution, assigned to a conformational inversion of the respective Cu2N4C4 metallacycles in all complexes but 1c, accompanied by a cisoid–transoid isomerization in the cases of complexes 1d,e. The Cu(I) complexes were also analyzed by cyclic voltammetry, where all complexes exhibit two oxidation processes, where the first oxidation is reversible, with the exception of 1b and 1c, which also show the highest oxidation potentials. The oxidation potentials follow clear trends related to the structural parameters of the complexes, in particular the Cu⋯Cu distance and the Cu2N4C4 macrocycles torsion angles. All new 5-substituted-2-iminopyrrolyl Cu(I) complexes 1a–e served as catalysts for azide–alkyne cycloaddition (CuAAC) reactions, being able to generate the respective 1,2,3-triazole products in yields as high as 82% and turnover frequencies (TOFs) as high as 859 h−1, after optimizing the conditions. The activity, as measured by the TOF, is in accordance with the oxidation potential of the corresponding complexes, the easier the oxidation, the higher the TOF value. Complex 1-H, where R = H, proved to be a poor catalyst for the same reactions, indicating that the 5-substitution in the ligand framework is crucial in stabilizing any potential catalytic species. [ABSTRACT FROM AUTHOR]

Synthesis, bonding and chemistry of mono‐ and bimetallic complexes supported by chelating thiolato ligands have been established. Treatment of [Cp*VCl2]3 (1) with [LiBH4 ⋅ THF] followed by the addition of ethane‐1,2‐dithiol led to the formation of an EPR active bimetallic vanadium thiolato complex [(Cp*V){μ‐(SCH2CH2S)‐κ2S,S′)2{V(SCH2CH2S‐SH)}] (2). In complex 2, two ethane‐1,2‐dithiolato ligands are symmetrically coordinated to two vanadium atoms through μ‐S atoms. Interestingly, when similar reactions were carried out with heavier group 5 metal precursors, such as [Cp*NbCl4] (3 a), it afforded monometallic thiolato complex [Cp*Nb(SCH2CH2S)(SCH2CH2S−CH2S)] (4 a). On the other hand, the Ta‐analogue [Cp*TaCl4] (3 b) yielded thiolato species [Cp*Ta(SCH2CH2S)(SCH2CH2S−CH2S)] (4 b) and [Cp*Ta(SCH2CH2S) (SCH2CH2S−S)] (5). In complexes 4 a and 4 b, one ethane‐1,2‐dithiolato and one trithiolato ligand are coordinated to Nb and Ta centers, respectively. Whereas, in complex 5, one ethane‐1,2‐dithiolato and one 2‐disulfanylethanethiolato is coordinated to the Ta center. Moreover, the photolytic reaction of 5 with [Mo(CO)5 ⋅ THF] yielded heterobimetallic thiolato complex [(Cp*Ta){μ‐(SCH2CH2S)‐κ2S,S′}{μ‐(SCH2CH2S−CH2(CH3)S)κ2S′′ : κ1S‐′′′′ : κ1S′′′′′}{Mo(CO)3}] (6). All the complexes have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction studies. Further, computational analyses were performed to provide an insight into the bonding of these complexes. [ABSTRACT FROM AUTHOR]

This review gives a comprehensive account in terms of the synthesis, characterization and biological application of bisthiosemicarbazone ligands and their metal complexes that have been reported until 2022. Their coordination chemistry with p and d block elements, where the structure is solved by single crystal X‐ray crystallography is explored. Complexes are placed group‐wise and their structure as well as bonding aspects are discussed separately. Various spectroscopic techniques for the characterization of ligands and their complexes like infrared (IR), ultraviolet‐visible (UV–Vis), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) (1H, 13C, 31P, 59Co, 119Hg) are discussed. Complexes formed by bisthiosemicarbazones are generally mononuclear; however, in some cases, binuclear or polynuclear complexes have also been found. Square planar, square pyramidal, octahedral, and pentagonal pyramidal are some of the common geometries exhibited by these complexes. Structure–activity relationship was established for substituted and unsubstituted diimine bisthiosemicarbazone complexes of different metal ions. The effect of co‐ligands on biological activity is also discussed. [ABSTRACT FROM AUTHOR]

Simple nucleophilic aliphatic substitution gives access to mono- and diphosphine ligands with a CpC group in the backbone. The monophosphine ligand coordinates to gold(I) via the phosphine site, to thallium(I) via the cyclopentadienyl site and to ruthenium(II) via a combination of both, resulting in an ansa-type structure. Coordination with the cyclopentadiene site is not possible for the diphosphine ligand. In this case, monodentate coordination to gold(I) and bidentate coordination to the [PdCl(μ2-Cl)]2, the [Rh(CO)(μ2-Cl)]2, and the Rh(CO)Cl fragment is observed, showing the variability in coordination modes possible for the long-chain diphosphine ligand. Ligands and complexes were characterized by means of NMR and IR spectroscopy, elemental analysis and X-ray structure analysis. [ABSTRACT FROM AUTHOR]

The chelating aluminum complex [2-(Me2NCH2)C2B10H10]AlX2 (X = Br 3, CH3 4) was synthesized using 2-dimethylaminomethyl-o-carboranyl lithium (LiCabN, 2) with aluminum tribromide (AlBr3) or dimethylaluminum bromide (Me2AlBr), resulting in a modest yield. Compound 4 was obtained by reacting compound 3 with methyllithium (CH3Li) in toluene. All compounds were characterized using infrared (IR) spectroscopy; 1H, 11B, 13C nuclear magnetic resonance (NMR) spectroscopy; and X-ray crystallography. X-ray structural studies of CabNAlBr2 (3) and CabNAlMe2 (4) (CabN = 2-dimethylaminomethyl-o-carboranyl) indicated that the aluminum atom was located at the center of a distorted tetrahedron. Crystal structures of CabNAlBr2 (3) [a = 8.9360(3) Å, b = 12.0358(9) Å, c = 14.7730(4) Å, α = β = γ = 90°] and CabNAlMe2 (4) [a = 8.9551(3) Å, b = 11.9126(9) Å, c = 14.7711(4) Å, α = β = γ = 90°] were obtained. The reactivity of aluminum complexes 3 and 4 with Lewis bases, such as H2O, pyridine, alkylamines, and arylamines, confirmed their rapid decomposition due to the strong Lewis acidity of aluminum metals. [ABSTRACT FROM AUTHOR]

Polymeric chelating ligands based on styrene and unsaturated -diketone 5-methyl-5-hexene-2,4-dione (MHD) were prepared by radical copolymerization initiated by benzoyl peroxide in benzene solution at the volume ratios of monomers styrene:MHD=1:30 and 1:10. In this case, β-diketone was added to the system by conventional (simultaneous) and compensatory (equal portions at conversions of 0, 5, and 10%) methods. The resulting products were studied by IR and ¹H NMR spectroscopies. It has been shown that macrochelates obtained on the basis of such ligands differ in their structure and as a consequence in their macroinitiating ability in the grafting of vinyl monomers. Polymeric ligands synthesized at the ratio of 1:10, regardless of the preparation method, form mixedligand complexes in the subsequent complexation reaction with cobalt(II) acetate, which exhibit weak activity in styrene grafting and are not effective in the case of methyl methacrylate. The use of a small amount of MHD (1:30) in combination with the compensatory synthesis method leads to the predominant formation of intramolecular complexes of the β-diketonate type, which are more active macroinitiators in the graft polymerization of styrene and methyl methacrylate than those obtained by the traditional simultaneous method of adding MHD. [ABSTRACT FROM AUTHOR]

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems of modern chemistry and advanced bioimaging. Three new iridium [Ir(N^C)2(N^N)]+ complexes with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives and different di-imine chelate ligands have been synthesized and characterized by mass spectrometry and NMR spectroscopy. The periphery of these complexes is decorated with three relatively small "double-tail" oligo(ethylene glycol) fragments. All these complexes exhibit phosphorescence; their photophysical properties have been thoroughly studied, and quantum chemical calculations of their photophysical properties were also performed. It turned out that the changes in the nature of the di-imine ligand greatly affected the character of the electronic transitions responsible for their emission. Two complexes in this series show the desired photophysical characteristics; they demonstrate appreciable quantum yield (14–15% in degassed aqueous solutions) and a strong response to the changes in oxygen concentration, ca. three-fold increase in emission intensity, and an excited state lifetime upon deaeration of the aqueous solution. The study of their photophysical properties in model biological systems (buffer solutions containing fetal bovine serum—FBS) and cytotoxicity assays (MTT) showed that these complexes satisfy the requirements for application in bioimaging experiments. It was found that these molecular probes are internalized into cultured cancer cells and localized mainly in mitochondria and lysosomes. Phosphorescent lifetime imaging (PLIM) experiments showed that under hypoxic conditions in cells, a 1.5-fold increase in the excitation state lifetime was observed compared to aerated cells, suggesting the applicability of these complexes for the analysis of hypoxia in biological objects. [ABSTRACT FROM AUTHOR]

Herein, a new Ru(II)-arene complex [(p-cymene)RuCl(bpyNO)]Cl, 1, bearing 5-methyl-[2,2′-bipyrimidine]-1-N-oxide (bpyNO, B) as a nitrogen donor ligand, has been prepared by reaction of [(p-cymene)RuCl(μ-Cl)]2, A, and bpyNO. The complex 1 was characterized by means of NMR spectroscopy, HR ESI-Mass, and X-ray crystallography techniques. The optical characteristics of these compounds in the ground state were investigated, and the findings were corroborated by calculations using density functional theory (DFT) and time-dependent DFT (TD-DFT). It was determined by a number of different approaches that every compound had suitable stability in biological media. On several different human cancer cell lines, including lung (A549), breast (MCF7), and cervical (HeLa) cells, and a normal cell line, lung fibroblasts (MRC5), the cytotoxic activities of A, B, 1, and another Ru(II) complex [(p-cymene)RuCl(bpy)]Cl, 2, bpy = 2,2′-bipyridine, were tested. Complex 1 demonstrated good to moderate anti-cancer activity. The effect of 1 on the proliferation of the non-tumorigenic cell line, MRC5, was more selective than that of cisplatin in distinguishing cancerous and non-cancerous cell lines. Furthermore, the most cytotoxic complex, 1, induces apoptosis, which causes cell death in the MCF-7 cancer cell line. Electrophoresis mobility shift assay and molecular docking were also performed in order to determine how and in which orientation these Ru(II) complexes are able to bind to DNA. [ABSTRACT FROM AUTHOR]

Multinuclear complexes of heavy metals, such as tungsten, have demonstrated considerable potential as candidates for advanced radiocontrast agents. Of particular interest is the development of stable non-ionic compounds with high metal content and reasonably low osmolality in solution. Accordingly, we have synthesized a series of neutral W(V) complexes that contain the W2O2(µ-O)2 core and amino acids or disubstituted EDTA derivatives as ligands. The compounds were prepared from the oxalatotungstate(V) complex via a convenient procedure utilizing microwave heating. Their detailed characterization was accomplished by electrospray ionization high-resolution mass spectrometry (ESI-HRMS), 1H and 13C NMR spectroscopy, elemental analysis, and X-ray crystallography. Further experiments to evaluate the utility of the complexes as radiocontrast media were precluded by their poor aqueous solubility. [ABSTRACT FROM AUTHOR]

Four divinylphenylene-bridged diruthenium complexes [{Ru(CO)(PiPr3)2(L-κ2[N,O]–)}2(μ-CH=CH-C6H4-CH=CH-1,4)] (2a–2d) with N,O-chelating 2-hydroxypyridine and 2-hydroxy- or 8-hydroxyquinoline ligands are presented. They were studied by NMR spectroscopy, electrochemical methods and, in their neutral and oxidized states, by IR, UV/Vis/NIR and, if applicable, by EPR spectroscopy. The experimental studies are complimented by (TD-)DFT calculations. Our results indicate that the pyridine-olate complexes 2a,b exist as three isomers with a ratio of about 78:20:2 that differ with respect to the orientation of the N and O donors relative to the CO and alkenyl ligands in the equatorial coordination plane. Only the isomer with both imine N donors trans to the alkenyl ligand is observed for complexes 2c,d with quinolinato ligands. All complexes undergo two consecutive, chemically and electrochemically reversible one-electron oxidations at low potentials. Our results indicate strong contributions of the divinylphenylene bridge to the redox processes and an even delocalization of the electron hole and the unpaired spin density over the entire π-conjugated divinylphenylene diruthenium backbone with only minor involvement of the peripherally attached κ2[N,O]– donor ligands. [ABSTRACT FROM AUTHOR]

The possibility of the complex formation of three bispidines with copper(ii) chloride and acetate in a deuterated DMF solution was studied by NMR titration. For all ligands, the formation of complexes with copper(ii) chloride was clearly detected based on the changes in the signals in the proton NMR spectra. The formation of complexes with copper(ii) acetate was not observed for any of the ligands. The results of the study can be used in the design of metal complex catalysts for the Henry reaction. [ABSTRACT FROM AUTHOR]

"2+1" tricarbonyl compexes [M(CO)3(N^N)CN(CH2)10COOMe]ClO4, where M = Tc or Re, N^N = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen), were prepared by the reaction of [M(CO)3(N^N)(MeOH)]ClO4 with methyl 11-isocyanoundecanoate in methanol. The complexes were isolated and characterized by IR and 1H NMR spectroscopy and by elemental analysis. The resistance of the "2+1" tricarbonyl complexes obtained to transchelation with histidine was evaluated. [ABSTRACT FROM AUTHOR]