Tris Complexes Research Articles

Dinuclear zinc(II) complex with tris(2-aminoethyl)amine ligand: synthesis, structure and properties

Abstract The dinuclear complex tris(2-aminoethyl)aminezinc(II)-μ-cyanothreecyanozincate(II) hemihydrate, [Zn(tren)Zn(μ-CN)(CN)3]·0.5H2O (1) (tren = tris(2-aminoethyl)amine), has been synthesized and characterized by spectral (FT-IR and Raman), elemental, thermal analysis (TG, DTG and DTA) as well as single crystal X-ray diffraction techniques. The asymmetric unit is composed of two Zn(II) ions, one tren ligand, four cyanide ligands and a half crystal water molecule which is situated at the special position. Zn1 ion exhibits tetrahedral coordination geometry with four carbon atoms of four cyanide ligands. Zn2 ion is five-coordinated by five nitrogen atoms from one tren and one cyanide ligands in a trigonal bipyramid coordination geometry. The cyanide nitrogen is in the axial position. Adjacent dinuclear units are connected by hydrogen bonding interactions to form three dimensional network. The decomposition reaction takes place in the temperature range 30–700 °C in the static air atmosphere.

Stabilizing coordinated radicals via metal-ligand covalency: a structural, spectroscopic, and theoretical investigation of group 9 tris(dithiolene) complexes.

Proper assignment of redox loci in coordination complexes with redox-active ligands to either the metal or the ligand is essential for rationalization of their chemical reactivity. However, the high covalency endemic to complexes of late, third-row transition metals complicates such assignments. Herein, we systematically explore the redox behavior of a series of group 9 tris(dithiolene) complexes, [M(mnt)3]3– (M = Ir, Rh, Co; mnt = maleonitriledithiolate). The Ir species described comprise the first examples of homoleptic Ir dithiolene complexes. The enhanced metal–ligand covalency of the Ir–S interaction leads to remarkable reactivity of [Ir(mnt)3]3– and stabilization of mononuclear [Ir(mnt)3]2– complex ions as well as dimerized versions featuring weak, covalent, intermolecular S–S bonds. The dianionic Rh and Co analogues are, in contrast, highly unstable, resulting in the rapid formation of [Rh2(mnt)5]4– and [Co(mnt)2]22–, respectively. The synthesized complexes were studied by single-crystal X-ray diffraction, X-ray absorption spectroscopy, optical spectroscopy, magnetometry, density functional theory, and spectroscopy-oriented configuration interaction calculations. Spectroscopic and theoretical analyses suggest that the stability of [Ir(mnt)3]2– may be attributed to dilution of ligand radical character by a high degree of Ir 5d character in the singly occupied molecular orbital.

Tris(2,2'-azobispyridine) complexes of copper(II): X-ray structures, reactivities, and the radical nonradical bis(ligand) analogues.

Tris(abpy) complexes of types mer-[Cu(II)(abpy)3][PF6]2 (mer-1(2+)[PF6(–)]2) and ctc-[Cu(II)(abpy)2(bpy)][PF6]2 (ctc-2(2+)[PF6(–)]2) were successfully isolated and characterized by spectra and single-crystal X-ray structure determinations (abpy = 2,2′-azobispyridine; bpy = 2,2′-bipyridine). Reactions of mer-1(2+) and ctc-2(2+) ions with catechol, o-aminophenol, p-phenylenediamine, and diphenylamine (Ph–NH–Ph) in 2:1 molar ratio afford [CuI(abpy)2](+) (3(+)) and corresponding quinone derivatives. The similar reactions of [Cu(II)(bpy)3](2+) and [Cu(II)(phen)3](2+) with these substrates yielding [Cu(I)(bpy)2](+) and [Cu(I)(phen)2](+) imply that these complexes undergo reduction-induced ligand dissociation reactions (phen = 1,10-phenanthroline). The average −N═N– lengths in mer-1(2+)[PF6(–)]2 and ctc-2(2+)[PF6(–)]2 are 1.248(4), while that in 3(+)[PF6(–)]·2CH2Cl2 is relatively longer, 1.275(2) Å, due to dCu → πazo* back bonding. In cyclic voltammetry, mer-1(2+) exhibits one quasi-reversible wave at −0.42 V due to Cu(II)/Cu(I) and abpy/abpy(•–) couples and two reversible waves at −0.90 and −1.28 V due to abpy/abpy(•–) couple, while those of ctc-2(2+) ion appear at −0.44, −0.86, and −1.10 V versus Fc(+)/Fc couple. The anodic 3(2+)/3(+) and the cathodic 3(+)/3 redox waves at +0.33 and −0.40 V are reversible. The electron paramagnetic resonance spectra and density functional theory (DFT) calculations authenticated the existence of abpy anion radical (abpy(•–)) in 3, which is defined as a hybrid state of [Cu(I)(abpy(0.5•–))(abpy(0.5•–))] and [Cu(II)(abpy(•–))(abpy(•–))] states. 3(2+) ion is a neutral abpy complex of copper(II) of type [Cu(II)(abpy)2](2+). 3 exhibits a near-IR absorption band at 2400–3000 nm because of the intervalence ligand-to-ligand charge transfer, elucidated by time-dependent DFT calculations in CH2Cl2.

Low‐temperature bleaching of cotton fabric using a copper‐based catalyst for hydrogen peroxide

Hydrogen peroxide can be catalysed to bleach cotton fibres at a temperature of 70 °C by incorporating the copper‐based catalyst [Cu(TPMA)Cl]ClO4·1/2H2O in the bleaching solution. The effects of pH, temperature, and concentration of catalyst and hydrogen peroxide on bleaching effectiveness were evaluated. The effects of other transition metal complexes of tris(2‐pyridylmethyl)amine were also examined. The bleaching mechanism was investigated by studying the active species. The results showed that a satisfactory whiteness index could be obtained at low temperature with the copper‐based catalyst, and it also had a competitive advantage in protecting cellulose from severe chemical damage. Cu(i)TPMA(OOH)− was the active species in bleaching.

Growth, hyperpolarizability, characterization and theoretical studies of NLO active tris(allylthiourea)mercury(II) chloride

Single crystals of tris(allylthiourea)mercury(II) chloride (TATMC) have been grown by slow evaporation solution growth technique. It belongs to the trigonal system with noncentrosymmetric space group R3c and the cell parameters are, a=b=11.4443(3)Å, c=28.1142(6)Å, V=3188.85(14)Å3, α=β=90°, γ=120° and Z=6. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown specimen and it closely resembles the simulated one from the single crystal XRD data. Good reflectance in the visible region is observed and the band gap energy is estimated using diffuse reflectance data by the application of Kubelka–Munk algorithm. The functional groups are identified by Fourier transform infrared spectral analysis and compared with theoretical spectrum. The crystal is stable up to the melting point and the mechanistic behavior is ascertained by microhardness studies. The second harmonic generation efficiency of TATMC is estimated by Kurtz and Perry powder technique. The first-order molecular hyperpolarizabilities of some tris(allylthiourea) complexes have been evaluated using density functional theory (DFT) employing B3LYP functional, LanL2DZ as basis set and results rationalized. The optimized geometry closely resembles the ORTEP. The Hirshfeld surface analysis is carried out using HF method with 3-21G as basis set. Investigation of the intermolecular interactions and crystal packing via Hirshfeld surface analysis, derived by single crystal XRD data, reveals the close contacts associated with strong interactions.

Rapid water oxidation electrocatalysis by a ruthenium complex of the tripodal ligand tris(2-pyridyl)phosphine oxide.

The tris(2-pyridyl)phosphine oxide (Py3PO) complex [Ru(Py3PO)(bpy)(OH2)]2+ (bpy is 2,2'-bipyridine) is a pH-dependent water oxidation electrocatalyst that accelerates dramatically with increasing pH-up to 780 s-1 at pH 10 (∼1 V overpotential). Despite retaining the pentakis(pyridine) ligand arrangement common to previously reported catalysts, the tripodal Py3PO ligand framework supports much faster electrocatalysis. The early stages of the catalytic cycle are proposed to follow the typical pattern of single-site ruthenium catalysts, with two sequential 1H+/1e- proton-coupled electron transfer (PCET) oxidations, but the pH-dependent onset of catalysis and rapid rates are distinguishing features of the present system.

Rapid water oxidation electrocatalysis by a ruthenium complex of the tripodal ligand tris(2-pyridyl)phosphine oxide

Rapid water oxidation electrocatalysis by a ruthenium complex of the tripodal ligand tris(2-pyridyl)phosphine oxide

Effect of Catalytic Aquathermolysis on High-Molecular-Weight Components of Heavy Oil in the Ashal’cha Field

We have studied the effect of catalytic aquathermolysis on the high-molecular-weight components of crude oil in the Ashal’cha field (Republic of Tatarstan). We used an iron(III) tris(acetylacetonate) complex as the catalyst. The change in the structure and composition of the resins and asphaltenes in aquathermolysis was studied by PMR and IR spectroscopy.

Mechanism, reactivity, and selectivity of the iridium-catalyzed C(sp3)-H borylation of chlorosilanes.

The iridium-catalyzed C(sp3)-H borylation of methylchlorosilanes is investigated by means of density functional theory, using the B3LYP and M06 functionals. The calculations establish that the resting state of the catalyst is a seven-coordinate Ir(v) species that has to be converted into an Ir(iii)tris(boryl) complex in order to effect the oxidative addition of the C-H bond. This is then followed by a C-B reductive elimination to yield the borylated product, and the catalytic cycle is finally completed by the regeneration of the active catalyst over two facile steps. The two employed functionals give somewhat different conclusions concerning the nature of the rate-determining step, and whether reductive elimination occurs directly or after a prior isomerization of the Ir(v) hydride intermediate complex. The calculations reproduce quite well the experimentally-observed trends in the reactivities of substrates with different substituents. It is demonstrated that the reactivity can be correlated to the Ir-C bond dissociation energies of the corresponding Ir(v) hydride intermediates. The effect of the chlorosilyl group is identified to originate from the α-carbanion-stabilizing effect of the silicon, which is further reinforced by the presence of an electron-withdrawing chlorine substituent. Furthermore, the source of selectivity for the borylation of primary over secondary C(sp3)-H can be explained on a steric basis, by repulsion between the alkyl group and the Ir/ligand moiety. Finally, the difference in the reactivity between C(sp3)-H and C(sp2)-H borylation is investigated and rationalized in terms of distortion/interaction analysis.

Synthesis and catalytic activity of homoleptic lanthanide-tris(cyclopropylethinyl)amidinates

New unsolvated, homoleptic lanthanide(iii) tris(cyclopropylethinylamidinate) complexes of the type [c-C3H5–CC–C(NR)2]3Ln (R = iPr, cyclohexyl; Ln = Nd, Sm, Ho) have been prepared and the crystal structure of the holmium derivative [c-C3H5–CC–C(NiPr)2]3Ho has been confirmed by X-ray diffraction.

Group VI metal complexes of tris(diphenylphosphinomethyl)phenylborate: modulation of ligand donation via coordination of M(CO)3 units at the borate phenyl substituent.

A series of d(6) metal complexes of tris(diphenylphosphinomethyl)phenylborate ([PhB(CH2PPh2)3](-), PhBP3), including [Et4N][M(CO)3(PhBP3)] (M = Cr, Mo, W), inaugural group VI metal tris(phosphino)borate complexes, and zwitterionic Mn(CO)3(PhBP3) have been synthesized and fully characterized. An analysis of IR ν(CO) data for [Et4N][M(CO)3(PhBP3)] indicates that PhBP3 is significantly less strongly donating than Tp towards zerovalent M(CO)3 fragments; PhBP3 does not function as a strongly donating scorpionate in this system as its does towards cationic metal fragments suggesting that PhBP3 may not function as an effective surrogate of hydrotris(1-pyrazolyl)borate towards zerovalent metals. While the metal centers of [Et4N][M(CO)3(PhBP3)] are very likely still more electron-rich than those of M(CO)3(triphos), the anions of [Et4N][M(CO)3(PhBP3)] do not provide robust oxidative addition products analogous to those of M(CO)3(triphos). A new bi-functional role for PhBP3 was investigated via the synthesis of seven structurally characterized bimetallics in which zerovalent M(CO)3 and monovalent [Mn(CO)3](+) fragments bind the three phosphine atoms and the borate phenyl substituent. IR ν(CO) data support modest attenuation of PhBP3 donor ability at phosphorus upon η(6)-phenyl substituent binding, representing a new inductive strategy for tuning tris(phosphino)phenylborate donation at the κ(3)-phosphine-bound metal fragment.

Ferrocene and cobaltocene derivatives for non-aqueous redox flow batteries.

Ferrocene and cobaltocene and their derivatives are studied as new redox materials for redox flow cells. Their high reaction rates and moderate solubility are attractive properties for their use as active materials. The cyclability experiments are carried out in a static cell; the results showed that these materials exhibit stable capacity retention and predictable discharge potentials, which agree with the potential values from the cyclic voltammograms. The diffusion coefficients of these materials are 2 to 7 times higher than those of other non-aqueous materials such as vanadium acetylacetonate, iron tris(2,2'-bipyridine) complexes, and an organic benzene derivative.

Heteroleptic chromium(III) tris(diimine) [Cr(N^N)2(N′^N′)]3 + complexes

A series of heteroleptic tris(diimine) complexes of chromium(III) is reported and the crystal structures of {4[Cr(bpy)2(phen)][PF6]3}·11MeCN and 4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O are described. The combined effects of a 1:3 cation: anion ratio and lattice solvent molecules are discussed, in particular in the context of the influence on intercation embraces. The presence of the methyl substituents in {4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O results in Me–πbpy contacts becoming the dominant packing interactions and in the assembly of motifs distinct from those in {4[Cr(bpy)2(phen)][PF6]3}·11MeCN.

Synthesis, characterization, single crystal XRD, in vitro antimicrobial and cytotoxicity study of tris(ethylenediamine)cobalt(III)chloride oxalate trihydrate

The complex tris(ethylenediamine)cobalt(III)chloride oxalate trihydrate [Co(en)3]Cl(C2O4)·3H2O crystallizes in the monoclinic space group C2/c with the following unit cell parameters a=19.9318 (13), b=9.3344 (4), c=19.0881 (13) Å β=96.846(3)°, Z=8. The crystal structure was solved by direct methods and refined by full matrix least squares procedures to a final R value of 0.0314 for 4330 observed reflections. The reported cobalt complex is six co-ordinated through amine nitrogen with distorted octahedral geometry. There are uncoordinated chloride and oxalate ions along with the water molecules. In-vitro antimicrobial activity was studied against various test organisms and found to be good. From in-vitro cytotoxic activity of the synthesized complex, the IC50 value was found to be 55.85μg/ml.

Interaction between chiral ions: synthesis and characterization of tartratovanadates(V) with tris(2,2′-bipyridine) complexes of iron(II) and nickel(II) as cations

Four new compounds composed of chiral complex cations and anions: Δ-[Fe(bpy)3] Λ-[Fe(bpy)3][V4O8((2R,3R)-tart)2]·12H2O (1), Δ-[Fe(bpy)3]2Λ-[Fe(bpy)3]2[V4O8((2R,3R)-tart)2][V4O8((2S,3S)-tart)2]·24H2O (2), Δ-[Ni(bpy)3]Λ-[Ni(bpy)3][V4O8((2R,3R)-tart)2]·12H2O (3) and Δ-[Ni(bpy)3]2Λ-[Ni(bpy)3]2[V4O8((2R,3R)-tart)2][V4O8((2S,3S)-tart)2]·24H2O (4) have been prepared. The compounds have been characterized by spectral methods, and their thermal decomposition was studied by simultaneous DTA, TG measurements. The final products after dynamic decomposition and additional heating were Fe2V4O13 for 1 and 2 and Ni(VO3)2 for 3 and 4. The crystal structures determined for 1, 2 and 4 have evidenced that 1 is “hemiracemic” and 2 and 4 are “fully racemic” compounds.

Two-photon sensitized visible and near-IR luminescence of lanthanide complexes using a fluorene-based donor-π-acceptor diketonate.

A fluorene-based donor-acceptor ligand was successfully employed to sensitize visible and near-IR emitting lanthanide centers. The ligand construct is based on a donor-π-acceptor architecture with diphenylamino acting as the donor and a fluorenyl π bridge derivatized with a trifluoroacetonate moiety acting as both a strong acceptor and the classic bidentate scaffold for complexing metals. (1)H NMR analysis in the polar solvents THF and CDCl3 revealed the enolic form of the diketone dominant in solution equilibria at room temperature. This preferred cis-enol form binds strongly to the lanthanide(III) ions (Ln = Eu, Sm, Dy, Tb, Yb, Nd, Er, and Gd) in the presence of phenanthroline affording the resulting ternary tris(diketonates) complexes with 1,10-phenanthroline. Detailed characterization of these complexes was conducted, with particular emphasis on linear and nonlinear photophysical properties. Steady-state and time-resolved emission spectroscopy and overall photoluminescence quantum yield (PLQY) measurements were performed on all the complexes. Sizeable visible and near-IR efficiency for europium (room temperature, visible), samarium (low temperature, visible) and ytterbium, neodymium and erbium (room temperature, near-IR) was displayed, with long luminescent lifetimes for the europium and samarium complexes of 85 and 70 μs, respectively Measurement of the luminescence decay for the Yb complex at 976 nm, Nd complex at 874 nm, and Er complex at 1335 nm yielded mono-exponential decay curves, with lifetimes of ~13 μs, ~1.6 μs, and ~2.5 μs, respectively, inferring that the emission was generated by a single species. In addition, fluorescence anisotropy and two-photon absorption (2PA) spectra (via Z-scan) were obtained for the ligand and europium complex, revealing a maximum 2PA cross section of 340 GM for the latter upon excitation at 760 nm. A quadratic relationship was found by varying laser excitation power vs. luminescence intensity of the europium complex, confirming sensitization via two-photon excitation.

Structural dynamics of ionic materials mapped by femtosecond x-ray diffraction

Relocation of electronic charge plays a key role for functional processes in condensed-phase molecular materials. X-ray diffraction with a femtosecond time resolution allows for spatially resolving transient atomic arrangements and charge distributions [1]. In particular, time-dependent spatial maps of electron density have been derived from x-ray powder diffraction patterns measured with a 100 fs time resolution. In this talk, new results on electron dynamics in transition metal complexes and on field-driven charge relocations in elementary ionic materials will be presented. Crystals containing a dense array of Fe(II)-tris(bipyridine) complexes and their PF6 counterions display pronounced changes of electron density that occur within the first 100 fs after two photon excitation of a small fraction of the complexes [2]. Electron density maps reveal a transfer of electronic charge from the Fe atoms and - so far unknown - from the PF6 counterions to the bipyridine units. The charge transfer displays pronounced Coulomb-mediated many-body features, affecting approximately 30 complexes around the directly excited one. As a second topic, electron relocations induced by strong external optical fields will be discussed [1,3]. This interaction mechanism allows for generating coherent superpositions of valence and conduction band quantum states and inducing fully reversible charge dynamics. While the materials LiBH4 and NaBH4 display electron relocations from the (BH4)- ions to the neighboring Li+ and Na+ ions, LiH exhibits an electron transfer from Li to H. The latter is a manifestation of electron correlations and in agreement with theoretical calculations.

Electrochemical Reaction of Tris(1,10-phenanthroline)Iron Complexes in Some Amide-Type Ionic Liquids

Electrochemical behavior of a charged species in ionic liquids have been known to depend on the physicochemical properties of the ionic liquids[1-4]. Diffusion of the charged species is affected not only by the viscosity of the ionic liquids but also by the coulombic interaction between the charged species and the ions composing the ionic liquids. Thus, Stokes-Einstein relation is generally inapplicable to diffusion of charge species in ionic liquids. The electron transfer rates are also influenced by the viscosity and the coulombic interaction, which is considered related to the outer component of reorganization energy. Furthermore, the reaction entropy of the redox couples without change of their coordination environment has been found to relate to the coulombic interaction[5,6]. We have reported these results with tris(2,2'-bipyridine) complexes of iron and ruthenium in some ionic liquids. In the present study, electrochemical reactions of tris(1,10-phenanthroline)iron and tris(2,2'-bipyridine)iron complexes were investigated in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA–) ionic liquids in order to elucidate the effects of the charge density of the redox species on electrode kinetics and reaction entropy. The diffusion coefficient of [Fe(phen)3] n+ was smaller than that of [Fe(bpy)3] n+ (n = 2 and 3) in BMPTFSA and EMITFSA. The ratios of diffusion coefficients of [Fe(phen)3]3+ to [Fe(phen)3]2+ were larger than those of [Fe(bpy)3]3+ to [Fe(bpy)3]2+, indicating the coulombic interaction of TFSA– with [Fe(phen)3] n+ is weaker than that with [Fe(bpy)3] n+ since the size of [Fe(phen)3] n+ is larger than that of [Fe(bpy)3] n+. The rate constants for [Fe(phen)3]3+/2+ were close to those for [Fe(bpy)3]3+/2+. On the other hand, the reaction entropy for [Fe(phen)3]3+/2+ was smaller than that for [Fe(bpy)3]3+/2+, reflecting the difference in the charge densities.

Synthesis and characterisation of unsymmetrical Zr(IV) amine tris(phenolate) complexes and their application in ROP of rac-LA.

Unsymmetrical amine tris(phenolate) ligands have been prepared and complexed to Zr(iv). In the solid-state dimeric species are observed, which persist in solution. The complexes show interesting coordination chemistry and the nature of which is discussed. These complexes are analogues of a highly stereoselective C3-symmetric Zr(iv) amine tris(phenolate) alkoxide and have been prepared, characterised and trialled for the ring-opening of rac-lactide providing insight into the effect of symmetry and ligand steric bulk on selectivity. The polymerisations have been investigated in solution and under the industrially preferred melt conditions (130 °C). The rate law for the ROP has been determined - with Zr2()2(O(i)Pr)2, a pseudo first order dependency was seen, however for Zr2()2(O(i)Pr)2 this changed to a half order dependency in initiator.

Tris‐cyclometalated Iridium(III) Complexes with Three Different Ligands: a New Example with 2‐(2,4‐Difluorophenyl)pyridine‐Based Complex

AbstractAn iridium(III) complex comprising three different cyclometalated phenylpyridine‐based ligands was designed and synthesized. Interestingly, mixed‐ligand complexes could be obtained by using a simple and straightforward procedure. A tris(heteroleptic) IrIII complex was obtained as a mixture of stereoisomers that could not be separated. Photophysical properties of the tris(heteroleptic) complex was investigated by UV/VIS absorption and luminescence spectroscopy, and compared with those of the parent homoleptic complexes. Modelling by time‐dependent density functional theory (TD‐DFT) was also performed to elucidate the nature and the location of the excited state, and to support the experimental results.