Spectrophotometric Studies of V(V) Complexes of N-Methylaminothioformyl-N′-phenylhydroxylamine

The violet-colored complexes of V(V) and N-methylaminothio-formyl-N′-phenylhydroxylamine are extractable into chloroform. The spectrophotometric studies have shown that 1:3 and 1:4 (metal:ligand) complexes predominate in the acidity range 6.5–9 N and 9.5–10.5 N HCl, respectively. The values of stability constants, stepwise and overall, have been calculated by following extended Leden and Yatsimirskii methods. The analytical suitability of the reagent for the microdetermination of vanadium has also been investigated.     

Syntheses of Binuclear Copper(I) Complexes Containing Benzimidazole

1 INTRODUCTION Procedures to synthesize copper(I) complexes are of great interest due to the diversity of products resulting from almost the same methodology. It has been long known that four-electron-donordipho- sphine compounds Ph2P(CH2)nPPh2 are excellent bi- dentate ligands[1, 2]. The chelating tendency of bis- (diphenylphosphino) methane is one of the dipho- sphine ligands most suitable to lock two metal atoms together in close proximity[3]. Many examples of bi- or polynuclear com…     

Monomeric and dimeric products of protonation of dioxotetracyanometalates(IV)—I: Complexes of tungsten(IV)

A series of tungsten(IV) complexes of formula Me₃[WO(OH)(CN)₄]xH₂O and Me₆[W₂O₃(CN)₈]xH₂O (where Me = Na, K) have been synthesized. The solids obtained were characterized by chemical analysis, thermogravimetric and differential thermal analysis, IR, Raman and visible spectrophotometry and magnetic susceptibility measurements. The analysis of the IR and Raman spectra has led to an assignment of the fundamental vibrations which was supported by studies of IR spectra of the deuterated and anhydrous salts.     

Facile Synthesis of Luminescent Ir–Pt–Ir Trimetallic Complexes

A new class of luminescent, heterotrimetallic supramolecular constructs partnering two bis-cyclometalated iridium centers with a diimine platinum acetylide center is introduced. Whereas most supramolecular constructs featuring cyclometalated iridium involve elaborate bridging ligands and are prepared under forcing conditions with low to moderate yields, the three Ir–Pt–Ir complexes described here are prepared at room temperature from simple precursors and isolated in near-quantitative yields. ESI-MS, NMR spectroscopy, and diffusion ordered spectroscopy confirm the identity and homogeneity of the trimetallic products. In comparison with monometallic model complexes, analysis of UV/Vis absorption, steady-state photoluminescence and time-resolved emission reveals the impacts of supramolecular assembly on the photophysical properties. UV/Vis absorption and cyclic voltammetry suggest perturbation of some frontier orbital energies as a result of assembly, and the emission spectra and lifetimes reveal efficient excited-state energy transfer via a Dexter mechanism, and show that the site of luminescence (platinum or iridium) depends on the identity of the cyclometalating ligand bound to iridium.     

Trace Ir(Ⅲ) complex enhanced electrochemiluminescence of AIE-active Pdots in aqueous media

Trace Ir(Ⅲ) complex enhanced aggregation-induced electrochemiluminescence(AIECL) of poly-tetraphenylethene(p TPE) in aqueous media was investigated for the first time. The poly-TPE end-capped by Ir(Ⅲ) complex(Ir@p TPE) and its corresponding model polymer poly-TPE(Ph@pTPE) could be synthesized by Suzuki coupling polymerization reaction of 1,2-bis(4-bromophenyl)-1,2-diphenylethene(M-1) with 1,2-diphenyl-1,2-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethene(M-2) and the continuous Suzuki coupling end-capped reaction of poly-TPE-pinacol boronate with(pq)2 Ir(pico)Br and bromobenzene, respectively. Subsequently, the corresponding Ir@p TPE Pdots and Ph@p TPE Pdots encapsulated with poly(styrene-co-maleicanhydride)(PSMA) could be obtained by nanoprecipitation method. Compared with Ph@p TPE Pdots, the Ir@p TPE Pdots with a trace amount of Ir(Ⅲ) complex(1.34‰ of Ir(Ⅲ) content, wt) could exhibit 9.9-fold enhancement of the electrochemiluminescence(ECL) signal for visual emission. This work provided a novel strategy on designing highly efficient ECL materials based on trace Ir(Ⅲ)-end capping AIE-active polymer dots.     

DFT Studies on Second-order Nonlinear Optical Response of Ir(C∧N)2(pic)Complexes

Density flmctional theory(DFT)was employed to calculate the geometrical structures,UV-Vis absorption spectra and second-order nonlinear optical(NLO)properties of a family of iridium(Ⅲ)complexes,which possess of different cyclometallated ligands(C∧N)and ancillary ligands[pyridme-2-carboxylate(pic)].It was found that the mo-dification of the LUMO energy levels was achieved by changing pic ligands and the energy gaps between the HOMO and LUMO were notably increased or decreased.In addition,the degree of conjugation was significantly changed with the substituent groups varied,which led to that the first hyperpolarizabilityβcould be effectively modulated.Through the analysis of time-dependent DFT(TD-DFT)results,we predicted that these studied complexes withπ→π^*charge transfer was beneficial to the large second-order NLO properties.Therefore,we hope that these studied iridium(III)complexes can be considered as versatile second-order NLO materials.     

Role of anions in the kinetics of the acid catalyzed dissociation of tris-(2,2′bipyridine) Fe(II) complex

Excess of Cl⁻ and NO₃⁻ ions bring about a significant increase in the rate of dissociation of the tris-(2,2′bipyridine) Fe(II) complex in HCl, HClO₄ and H₂SO₄ in a very narrow range of H⁺ concentration (∼0·1−0·3 M). Above and below this concentration range, these anions do not lead to significant variation in the rate of dissociation. This points to the involvement of these ions in a kinetic step which is only important in the rate expression in this narrow range. It is suggested that the anions occupy the coordination site left vacant by the partial dissociation of the complex leading to the half bonded intermediate. This would significantly lower the free energy of activation for the subsequent protonation step leading to complete dissociation and thus lead to acceleration. The lowering of the free energy of activation will be mainly due to an increase in entropy of this intermediate on account of charge reduction and lower rigidity due to lack of hydrogen bonding. The retarding effect of SO₄²⁻ concentrations and the unambiguously interpreted as its addition leads to simultaneous changes in H⁺ and HSO₄⁻ concentrations and the possibility of ion pair formation with the complex cannot be ruled out.     

Polymer-Supported Lewis Acid Catalysts. V. Complexes of Titanium Chloride or Stannic Chloride with Poly (βDiketone) Carrier

A polymer carrier containing (β-diketone groups was synthesized by a free radical polymerization of methacrylacetone monomer and combined with titanium tetrachloride or stannic chloride in chloroform to form two very stable complexes containing 19.5 and 18.3% CI which are equivalent to 1.40 mmol TiCl₄ complex beads and 1.28 mmol SnCl₄; complex beads, respectively. The two complexes showed good catalytic activity in many organic reactions such as acetalation, ketal formation, and esterification. The catalysts can be reused at least 8 times without losing their activity in organic reactions.     

Synthesis and characterization of chromium(I) bis(η-toluene) derivatives containing sterically demanding anions

The reaction of Cr(η⁶-CH₃C₆H₅)₂ with 1-benzoyl-6-hydroxy-6-phenyl fulvene, dbcpH, and with pentakis(methoxycarbonyl)cyclopentadiene, pcmcpH, proceeds with evolution of dihydrogen and the formation of the ionic derivatives [Cr(η⁶-CH₃C₆H₅)₂][X] ([X]⁻ = 1,2-dibenzoylcyclopentadienyl, [dbcp]⁻, pentakis(methoxycarbonyl)cyclopentadienyl, [pcmcp]⁻), which have been characterized by IR and EPR spectroscopies, X-ray diffraction and electrochemical techniques. The sterically demanding anions do not affect the structural and electronic properties of the cations in solution but strongly influence crystal packing. In fact, a rare cis-eclipsed conformation of the toluene rings is found for [Cr(η⁶-CH₃C₆H₅)₂][dbcp] · THF, whereas two independent complexes are observed in the unit cell of [Cr(η⁶-CH₃C₆H₅)₂][pcmcp], one with toluene rings in a cis-eclipsed conformation and the other in a staggered conformation (projections of methyl groups form an angle of 151°).     

Vapour—liquid equilibria of dilute solutions of phenols in cyclohexane. Self-association of ortho-substituted phenols

Vapour—liquid equilibria of dilute solutions of ortho-substituted phenols in cyclohexane have been studied. The isopiestic apparatus and the operational procedure have been described. Eight mono- and di-substituted ortho-alkylphenols have been studied at 298.15 K using this technique; o-ethyl- and o-chlorophenol solutions have been studied at 298.15 and 323.15 K using the bubble-point method. The values of dimerization and polymerization constants are given. The practical osmotic coefficient of the solutions of diphenyl in cyclohexane at 298.15 K (serving as reference in isopiestic measurements) has been determined bythe bubble-point method, and the results represented by a polynomial.     

The vibrational spectra of complexes with planar monothio-oxamides—II. Complexes of N(s)-methylmonothio-oxamide

The new complexes Pd(SH₂)₂ · H₂O, M(SH) · H₂O (M = Ni, Pd, Pt) and M(SH) · 0.5H₂O (M = Cu, Zn), where SH₃ = N_(s)-methylmonothio-oxamide, have been prepared. The complexes were characterized by metal analyses, thermal methods and i.r., Raman and u.v./vis spectroscopic studies. The vibrational analyses of the complexes are given using NH/ND, CH₃/CD₃ and metal isotopicsubstitutions. The Ni(II), Pd(II), Pt(II) and Cu(II) compounds are square planar. The vibrational spectra show that in Pd(SH₂)₂ · H₂O the coordination occurs via the sulphur atom of the deprotonated thioamide group and the oxygen atom of the neutral primary amide group, in a bidentate chelated fashion. The doubly deprotonated SH²⁻ ion behaves as a bridging bis-bidentate ligand giving polymeric structures.     

Complexes of Cu(I) and Pd(II) with (+)-camphor and (–)-cavrone thiosemicarbazones: Synthesis,structure, and cytotoxicity of the Pd(II) complex

CuLCl, CuL¹Cl, PdLCl₂, and PdL¹Cl₂ complexes [L and L¹ being (+)-camphor and (–)-carvone thiosemicarbazones, respectively] have been synthesized. The structure of binuclear [Pd₂L²²Cl₄] complex has been determined by means of X-ray diffraction. The L² ligand (dehydrogenated (–)-carvone thiosemicarbazone) is coordinated via the bridging S atom to two Pd atoms. The complexes of Cu(I) and Pd(II) presumably have polynuclear and binuclear structure, respectively. These facts are in good agreement with IR and NMR spectroscopy as well as mass spectrometry data which indicate the coordination of L and L¹ ligands via the S atom. The influence of L¹ and PdL¹Cl₂ on viability of the Hep2 cell line has been studied. The PdL¹Cl₂ complex is more cytotoxic than L¹ ligand.     

Transition Metal Complexes with Thiosemicarbazide-Based Ligands. Part 37.* Synthesis and Study of the first Thiosemi-Carbazide-Derived Copper(I) Complexes: Crystal Structure of [2-(Diphenylphosphino)Benzaldehyde Thiosemicarbazonato(−1)] Copper(I)-Nitrate-Methanol Solvate

Abstract

The preparation and physical characterization of two copper(I) complexes Cu(HL)NO₃ and [Cu(HL)₂]NO₃·MeOh formed with a newly synthesized tridentate [S,N,P] HL = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone ligand and the crystal structure analysis of the latter have been carried out. An X-ray study of [Cu(HL)₂]NO₃·MeOH revealed a copper(I) ion coordinated tetrahedrally to S,N,P,P atoms donated by two HL ligands. One is tridentate [S,N,P], whereas the second HL ligand is monodentate, ligating only its phosphorus atom to the copper. The geometry around the four-coordinate Cu(I) is comparable with Cu{N,S,P,X} tetrahedra (X = N, P, or S) retrieved from the Cambridge Structural Database. In addition, with a restriction to Cu{N,P,X,X} (X = C,N,P) tetrahedra ‐ S is excluded ‐ ca. 60 structures against     

Complexes of group IIb metals with dithio oxamides—II. Vibrational analysis of ZnLX2(X = Cl,Br, I) complexes

With dithiooxamides, Zn(II) in acid media forms distorted tetrahedral complexes, which behave as non-electrolytes. The ligands act as bidentates with S, S coordination.A thorough vibrational analysis has been performed for the Zn(CH₃ NHCSCSNHCH₃)X₂(X = Cl, Br, I) and for the Zn[(CH₃)₂NCSCSN(CH₃)₂]X₂(X = Cl, Br, I) complexes.     

Recognition of amino acids and anions by a Zn(Ⅱ)-methylazacalix[4]pyridine complex

As a powerful macrocyclic host molecule with unique conformation and cavity structure that are fine-tuned by the bridging nitrogen atoms, methylazacalix[4]pyridine (MACP-4) has been shown to selectively recognize Zn2+ and form stable Zn(Ⅱ)-MACP-4 complexes both in solid state and solution with an association constant up to 5.97 (logKs). The molecular recognition of Zn(Ⅱ)-MACP-4 complexes towards various amino acids and anions with different geometry was investigated by using the spectral titration methods a...     

EPR of layered magnetic metal—amino acid salts. I. Cu(L-PHE)2

EPR measurements in single crystals of Cu(L-PHE)₂, the copper derivative of the amino acid L-phenylalanine, were performed at 300 K and 9.7 GHz. The gyromagnetic factor, g, and the linewidth of the single EPR line were measured in three perpendicular planes of the sample. The gyromagnetic tensor was obtained, and its principal values are g₁ = 2.211, g₂ = 2.134, and g₃ = 2.075. The single resonance is explained by the collapse of the resonances of the two magnetically non-equivalent copper sites due to the exchange interaction. The molecular g-factor of isolated copper ions is obtained from a model assuming axial symmetry. The results are g_| = 2.266 and g_⊥ = 2.075, indicating a d(x² - y²) ground orbital. The orientations of the molecules in the crystal obtained by this model are in agreement with the crystallographic values. The linewidth data support a model which assumes exchange narrowing of the magnetic dipolar interaction in a two-dimensional magnetic structure, an incomplete collapse of the hyperfine structure, and contributions arising from non-isotropic exchange. A mean value ¦J¦=0.19 K is calculated for the isotropic exchange interactions between one copper and its six copper neighbors in Cu(L-PHE)₂. Also, a lower limit ¦J′¦ > 0.02 K for the exchange coupling J′ between non-equivalent copper neighbors is obtained.     

Water insoluble polyacrylamide—V. Dilute solution properties of poly(N-acryloyl-o-aminobenzoic acid)

A high molecular weight poly(N-acryloyl-o-aminobenzoic acid) has been synthesized by radical polymerization in a mixed solvent medium. The polymer has been fractionated by fractional precipitation and the fractions characterized by viscometry, vapour pressure osmometry and gel permeation chromatography. Mark-Houwink-Kuhn-Sakurada relationships are developed for three solvents. The values of unperturbed dimensions, (〈R₀²〉/M)^0.5, are evaluated by application of two-parameter theories of the excluded volume effect, developed by Fixman, Kurata, Stockmayer and Roig and by Bueche and James and first order perturbation theory. Based on the value of the conformational parameter σ, the polymer is found to behave as a semiflexible polymer in solution as a result of the increased bulk of the lateral group.     

The i.r. spectra of ethylenediamine complexes—I. The tris(ethylenediamine) complexes of first transition series metal(II) sulphates

The i.r. spectra of the complex [Zn(en)₃]SO₄ and its ⁶⁴Zn-, ⁶⁸Zn-, ¹⁵N-, N₂D₄- and C₂D₄-labelled analogues have been determined over the range 4000-50 cm⁻¹. Band assignments are based on the isotopically induced shifts and also those which result from substitution of Zn(II) by the metal(II) ions of the first transition series: Mn(II), Fe(II), Co(II), Ni(II) and Cu(II). The spectrum of the Cu(II) complex yields evidence of Jahn—Teller distortion.