Cobalt complexes with hemilabile o-iminobenzoquinonate ligands: a novel example of redox-induced electron transfer.

The tetracoordinated square-planar CoIII complex (imSQC(O)Ph)CoIII(APC(O)Ph) (1) bearing a radical anion and the closed-shell o-amidophenolate forms of the functionalized o-aminophenol H2LC(O)Ph were synthesized. The intermediate spin state (SCo = 1) CoIII center was found for compound 1. The cyclic voltammogram of derivative 1 contains two oxidative processes and one reductive redox process as well as an additional multi-electron wave at high negative potentials above -2 V, which can involve both the ligand and metal center.

TD DFT insights into unusual properties of excited sandwich complexes: structural transformations and vibronic interactions in Rydberg-state bis(η-benzene)chromium.

Sandwich compounds represent the only class of organometallics revealing vibronic structures of Rydberg transitions in their gas-phase absorption and ionization spectra. This provides rare possibilities of verifying computational results for Rydberg-state metal complexes by comparison with experimental spectroscopic data. In this work, the lowest Ryberg p state of bis(η-benzene)chromium (1) corresponding to the 3d→ R4p transition has been modeled for the first time by TD DFT.

Cycloaddition versus Cleavage of the C=S Bond of Isothiocyanates Promoted by Digallane Compounds with Noninnocent α-Diimine Ligands.

Whereas the chemistry of single-bond activation by compounds of the main group elements has undergone some development in recent years, the cleavage of multiple bonds remains underexplored. Herein, the reactions of two digallanes bearing α-diimine ligands, namely, [L Ga-GaL ] (1, L =dpp-dad=[(2,6-iPr C H )NC(CH )] ) and [L Ga-GaL ] (2, L =dpp-bian=1,2-[(2,6-iPr C H )NC] C H ), with isothiocyanates are reported. Reactions of 1 or 2 with isothiocyanates in 1:2 molar ratio proceeded with [2+4] cycloaddition of the C=S bond across the C N Ga metallacycle with formation of C-C and S-Ga single bonds to afford [L (RN=C-S)Ga-Ga(S-C=NR)L ] (3, R=Me; 4, R=Ph) and [L (RN=C-S)Ga-Ga(S-C=NR)L ] (8, R=allyl; 9, R=Ph).

Amido Ca(ii) complexes supported by Schiff base ligands for catalytic cross-dehydrogenative coupling of amines with silanes.

A series of amido Ca complexes LCa[N(SiMe3)2](THF) (1-4) coordinated by Schiff base ligands L1-4 were synthesized via an amine elimination reaction between proligands L1-4H and a bisamido complex Ca[N(SiMe3)2]2(THF)2 in good yield. Unlike Ca[N(SiMe3)2]2(THF)2, the reactions of M[N(SiMe3)2]2(THF)2 (M = Yb, Sm) with proligands L1-4H do not lead to the formation of the target Ln(ii) amido complexes. The reaction of Yb[N(SiMe3)2]2(THF)2 with L1H is accompanied by intramolecular C-H bond activation of a quinoline ring and results in the formation of complex 6 coordinated by a new trianionic [NNNNOO] ligand.

Lanthanum Complexes with a Diimine Ligand in Three Different Redox States.

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian) with an excess of La metal in the presence of iodine (dpp-Bian/I = 2/1) in tetrahydrofuran (thf) or dimethoxyethane (dme) affords lanthanum(III) complexes of dpp-Bian dianion: deep blue [(dpp-Bian)LaI(thf)] (1, 84%) was isolated by crystallization of the product from hexane, while deep green [(dpp-Bian)LaI(dme)] (2, 93%) precipitated from the reaction mixture in the course of its synthesis. A treatment of complex 1 with 0.5 equiv of I in thf leads to the oxidation of the dpp-Bian dianion to the radical anion and results in the complex [(dpp-Bian)LaI(thf)] (3).

Amido Ca and Yb(II) Complexes Coordinated by Amidine-Amidopyridinate Ligands for Catalytic Intermolecular Olefin Hydrophosphination.

A series of amido Ca and Yb(II) complexes LM[N(SiMe)](THF) (1Yb, 1-4Ca) coordinated by amidine-amidopyridinate ligands L were synthesized via a transamination reaction between proligands LH and bisamido complexes M[N(SiMe)](THF) (M = Yb, Ca). The reactions of Yb[N(SiMe)](THF) with proligands LH-LH containing CF and CHF fragments do not allow for preparing the target Yb(II) complexes, while the Ca analogues were synthesized in good yields. Complexes 1Yb and 1-4Ca were evaluated as precatalysts for hydrophosphination of styrene, p-substituted styrenes, α-Me-styrene, and 2,3-dimethylbutadiene with various primary and secondary phosphines (PhPH, 2,4,6-MeCHPH, 2-CNHPH, PhPH, CyPH).

Liposomal Form of Tetra(Aryl)Tetracyanoporphyrazine: Physical Properties and Photodynamic Activity In Vitro.

Tetra(aryl)tetracyanoporphyrazines are the promising group of dyes for photodynamic therapy of tumors with unique combination of photosensitizer properties and sensitivity of fluorescence parameters to the environment viscosity. However, in vivo application of such hydrophobic photosensitizers requires using of drug carriers ensuring efficient delivery to the tumor site. The present study is focused on obtaining liposomes loaded with tetrakis(4-benzyloxyphenyl)tetracyanoporphyrazine and examining their properties depending on lipid composition.

Steric control in the metal-ligand electron transfer of iminopyridine-ytterbocene complexes.

A systematic study of reactions between Cp*Yb(THF) (Cp* = η-CMe, 1) and iminopyridine ligands (IPy = 2,6-PrCHN[double bond, length as m-dash]CH(CHN-R), R = H (2a), 6-CHO (2b), 6-CHS (2c), 6-CH (2d)) featuring similar electron accepting properties but variable denticity and steric demand, has provided a new example of steric control on the redox chemistry of ytterbocenes. The reaction of the unsubstituted IPy 2a with 1, either in THF or toluene, gives rise to the paramagnetic species Cp*Yb(IPy)˙ (3a) as a result of a formal one-electron oxidation of the Yb ion along with IPy reduction to a radical-anionic state. The reactions of 1 with substituted iminopyridines 2b-d, bearing aryl or hetero-aryl dangling arms on the 6 position of the pyridine ring occur in a non-coordinating solvent (toluene) only and afford coordination compounds of a formally divalent ytterbium ion, coordinated by neutral IPy ligands Cp*Yb(IPy) (3b-d).

Valence-Tautomeric Interconversion in a Bis(dioxolene)cobalt Complex with Iminopyridine Functionalized by a TEMPO Moiety. Phase Transition Coupled with Monocrystal Destruction.

Iminopyridine modified by TEMPO nitroxide was utilized for the synthesis of an octahedral bis(o-semiquinonato)cobalt complex. Variable-temperature magnetic susceptibility measurements detect a valence tautomeric transformation in the temperature range 200-300 K. A reproducible hysteresis loop of about 40 K width is observed on the magnetic moment temperature dependence in the transition region.

Regioisomerism in coordination chemistry: oxidative addition of a bifunctional ligand to palladium, stabilized with 1,2-bis(diphenylphosphino)ethane.

A unique phenomenon of regioisomerism in coordination chemistry was discovered: the reaction of a sterically hindered o-quinone annelated with a dithiete ring with Pddba in the presence of 1,2-bis(diphenylphosphino)ethane (dppe) gave a mixture of two regioisomers: catecholate 3Cat and dithiolate 3Dit. Both isomers were isolated in crystalline form and characterized by NMR, IR and X-ray diffractometry studies. DFT calculations reveal that the 3Dit species is more thermodynamically stable than the isomer 3Cat.

The Weakly Coordinating Tris(trichlorosilyl)silyl Anion.

Closely following the procedure for the preparation of the base-stabilized dichlorosilylene complex NHC ⋅SiCl reported by Roesky, Stalke, and co-workers (Angew. Chem. Int.

Redox-Active Ligand-Assisted Two-Electron Oxidative Addition to Gallium(II).

The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η -All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7).

Gallium Hydrides with a Radical-Anionic Ligand.

The reaction of ClGaH with a sodium salt of the dpp-Bian radical-anion (dpp-Bian)Na (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) affords paramagnetic gallane (dpp-Bian)Ga(Cl)H (1). Oxidation of (dpp-Bian)Ga-Ga(dpp-Bian) (2) with NO results in the dimeric oxide (dpp-Bian)Ga(μ-O)Ga(dpp-Bian) (3). A treatment of the oxide 3 with phenylsilane affords paramagnetic gallium hydrides (dpp-Bian)GaH (4) and (dpp-Bian)Ga{OSi(Ph)H}H (5) depending on the reagent's stoichiometry.

Facile activation of alkynes with a boraguanidinato-stabilized germylene: a combined experimental and theoretical study.

A boraguanidinato-stabilized germylene, [(i-Pr)NB(N-2,6-MeCH)]Ge, reacts with alkynes RC[triple bond, length as m-dash]CR selectively in a 2 : 1 molar ratio to afford 3,4-R,R'-1,2-digermacyclobut-3-enes 1a-e as the products of formal [2 + 2 + 2] cyclization [R/R' = Me/Me (1a), Ph/Ph (1b), Ph/H (1c), t-Bu/H (1d) and Cy/H (1e)]. Ferrocenyl-substituted alkynes react similarly, yielding the corresponding ferrocenylated 3,4-R,R'-1,2-digermacyclobut-3-enes 2a-d [where R/R' = Fc/H (2a), Fc/Me (2b), Fc/Ph (2c), and Fc/Fc (2d); Fc = ferrocenyl]. By contrast, only one of the triple bonds available in conjugated diynes RC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CR is activated with the germylene, while the second one remains intact even in the presence of an excess of the germylene.

Ytterbium and Europium Complexes of Redox-Active Ligands: Searching for Redox Isomerism.

The reaction of (dpp-Bian)Eu(dme) (3) (dpp-Bian is dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; dme is 1,2-dimethoxyethane) with 2,2'-bipyridine (bipy) in toluene proceeds with replacement of the coordinated solvent molecules with neutral bipy ligands and affords europium(II) complex (dpp-Bian)Eu(bipy) (9). In contrast the reaction of related ytterbium complex (dpp-Bian)Yb(dme) (4) with bipy in dme proceeds with the electron transfer from the metal to bipy and results in (dpp-Bian)Yb(bipy)(bipẏ) (10) - ytterbium(III) derivative containing both neutral and radical-anionic bipy ligands. Noteworthy, in both cases dianionic dpp-Bian ligands retain its reduction state.

Sensitization of NIR luminescence of Yb by Zn chromophores in heterometallic complexes with a bridging Schiff-base ligand.

Herein, complexes [ZnL] (1), {(HO)Zn(μ-L)Yb[OCH(CF)]} (2), {[(CF)HCO]Zn(μ-L)Yb[OCH(CF)](μ-OH)} (3), and [(HO)Ln(L)] (Ln = Yb (4) and Gd (5)) containing a bridging Schiff-base ligand (HL = N,N'-bis(3-methoxy salicylidene)phenylene-1,2-diamine) were synthesized. The compounds 1-4 were structurally characterized. The ytterbium derivatives 2-4 exhibited bright NIR metal-centred photoluminescence (PL) of Yb ion under one- (λ = 380 nm) and two-photon (λ = 750 nm) excitation.

DFT-Supported Threshold Ionization Study of Chromium Biphenyl Complexes: Unveiling the Mechanisms of Substituent Influence on Redox Properties of Sandwich Compounds.

High-resolution mass-analyzed threshold ionization (MATI) spectra of (η -Ph ) Cr and (η -Ph )(η -PhMe)Cr demonstrate that the Ph groups work as electron donors, decreasing the ionization energy of the gas-phase bisarene complexes. In contrast to electrochemical data, a close similarity of the Ph and Me group effects on the oxidation of free sandwich molecules has been revealed. However, DFT calculations testify for the opposite shifts of the electron density caused by the Me and Ph substituents in the neutral complexes, the latter behaving as an electron-accepting fragment.

Noninnocent ligands: heteroleptic nickel complexes with α-diimine and 1,2-diketone derivatives.

Reaction of the Ni-Ni-bonded compound [(NiL˙)] (1, L = [(2,6-iPrCH)NC(Me)]) with various 1,2-diketones afforded a series of heteroleptic complexes: [LNi(PhC(O)-C(O)Ph)] (2), [LNi(PhC(O)-C(O)Me)] (3), [LNi(3,5-tBuCHO)] (4), and [(LNi){μ-η,η-(MeC(O)-C(O)Me)}(NiL)] (5). Furthermore, the complex [Na(EtO)][LNi{PhC(O)-C(O)Ph}] (6) was obtained by the reduction of 2 with 1.0 equiv.

Ferromagnetic Coupling in the Heterospin Bis-Catecholato-Manganese(IV) Complex with Pyridine Substituted by Nitronyl-nitroxide.

A new bis(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py ligands was synthesized and characterized [4-NIT-Py = pyridine substituted at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination core of the metal and in the chelate cycles that are representative of the charge distribution between the metal and ligands displayed a Mn(IV)(Cat) charge distribution.

LMCT facilitated room temperature phosphorescence and energy transfer in substituted thiophenolates of Gd and Yb.

To obtain luminescent lanthanide complexes with a low energy LMCT state the 2-(2'-mercaptophenyl)benzothiazolates, Ln(SSN), and 2-(2'-mercaptophenyl)benzoxazolates, Ln(OSN) (Ln = Gd, Yb), were synthesized by the reaction of amides Ln[N(SiMe)] with respective thiophenols. Ytterbium complexes were structurally characterized by X-ray diffraction analysis. Cyclic voltammetry revealed that the deprotonated mercaptophenyl ligands have significantly lower oxidation potentials than their phenoxy analogues and some β-diketones.

Protonated paramagnetic redox forms of di--quinone bridged with -phenylene-extended TTF: A EPR spectroscopy study.

The chemical oxidation and reduction processes of deprotonated, direduced -quinone-exTTF--quinone in protic solvents were studied by EPR spectroscopy. The formation of relatively stable paramagnetic protonated redox forms of the parent triad was very surprising. The character of spin-density distribution in the semiquinone-quinone and semiquinone-catechol redox forms indicates that the -phenylene-extended tetrathiafulvalene connector provides a quite effective electronic communication channel between dioxolene coordination sites.

Imaging tumor microscopic viscosity in vivo using molecular rotors.

The microscopic viscosity plays an essential role in cellular biophysics by controlling the rates of diffusion and bimolecular reactions within the cell interior. While several approaches have emerged that have allowed the measurement of viscosity and diffusion on a single cell level in vitro, the in vivo viscosity monitoring has not yet been realized. Here we report the use of fluorescent molecular rotors in combination with Fluorescence Lifetime Imaging Microscopy (FLIM) to image microscopic viscosity in vivo, both on a single cell level and in connecting tissues of subcutaneous tumors in mice.

Effective delivery of porphyrazine photosensitizers to cancer cells by polymer brush nanocontainers.

Efficient drug delivery can be assigned to tasks that attract the most acute attention of researchers in the field of anticancer drug design. We have reported the first case of using amphiphilic polymer brushes as nanocontainers for photosensitizer delivery to cancer cells. Regular graft-copolymers of hydrophobic polyimides with hydrophilic polymethacrylic acid side chains were loaded with photosensitive dye tetra(4-fluorophenyl)tetracyanoporphyrazine (Pz) providing a sufficiently stable homogeneous fraction of fluorescent Pz-loaded nanoparticles with a size of 100-150 nm.

The First Lanthanide Complexes with a Redox-Active Sulfur Diimide Ligand: Synthesis and Characterization of [LnCp* (RN=) S], Ln=Sm, Eu, Yb; R=SiMe.

The first lanthanide complexes with a redox-active sulfur diimide ligand, [LnCp* (Me SiN=) S] (Ln=Sm, Eu, Yb; Cp*=η -C Me ), are reported. The complexes were synthesized by using [LnCp* (THF) ] and (Me SiN=) S and have been thoroughly characterized by single-crystal X-ray diffraction, EPR spectroscopy, UV/Vis/NIR electronic absorption spectroscopy and SQUID magnetometry. The results, as interpreted by CASSCF/SOC-RASSI calculations providing a non-perturbative treatment of spin-orbit coupling, indicate that these paramagnetic complexes are best described as Ln and [(Me SiN=) S] adducts.

Ligand "Brackets" for Ga-Ga Bond.

The reactivity of digallane (dpp-Bian)Ga-Ga(dpp-Bian) (1) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) toward acenaphthenequinone (AcQ), sulfur dioxide, and azobenzene was investigated. The reaction of 1 with AcQ in 1:1 molar ratio proceeds via two-electron reduction of AcQ to give (dpp-Bian)Ga(μ2-AcQ)Ga(dpp-Bian) (2), in which diolate [AcQ](2-) acts as "bracket" for the Ga-Ga bond. The interaction of 1 with AcQ in 1:2 molar ratio proceeds with an oxidation of the both dpp-Bian ligands as well as of the Ga-Ga bond to give (dpp-Bian)Ga(μ2-AcQ)2Ga(dpp-Bian) (3).