Metal-organic chains constructed from pre-organized N2S2 donor ligands

Three new N₂S₂ donor ligands 1,1′-((2-(2-(phenylthio)phenylthio)phenyl)methylene)bis(3,5-R-1H-pyrazole), R = H (L^H), R = Me (L^Me), R = i-Pr (L^i-Pr) have been prepared and characterized. These bifunctional ligands incorporate two distinct chelate donor systems, by virtue of the presence of bispyrazole and bisthioether functions. The preferred conformation of these ligands is such that the N₂ and S₂ donor moieties may be oriented in opposite directions, thus favoring the formation of molecular chains when treated with AgBF₄. The X-ray structures of Ag(I) complexes show that, depending on the steric hindrance present on the pyrazole rings, these ligands behave as κ⁴-SSNN-μ bridging tetradentate (when R = H), or κ³-SNN-μ bridging tridentate (when R = Me, i-Pr). Interestingly, [Ag(L^H)]BF₄ crystallizes in the chiral space group P4₁, with the molecular chain that is folded around the 4₁ screw axis.     

Three-dimensional acentric coordination polymers formed from the linkage of cobalt and nickel malonate quadratic layers through a kinked organodiimine: Synthesis,structure, thermal properties and magnetochemistry

Hydrothermal synthesis has afforded a pair of isostructural acentric three-dimensional coordination polymers {[M₂(malonate)₂(dpa)(H₂O)₂] · 2H₂O}_n (M = Co, 1; M = Ni, 2; dpa = 4,4′-dipyridylamine), which were structurally characterized via single-crystal X-ray diffraction and spectroscopically and thermally analyzed. Both materials exhibit exotridentate malonate ligands conjoining metal atoms into grid-like [M(malonate)(H₂O)]_n layers; in turn, these are connected into 3-D sqp lattices (4⁴6⁶ topology) through tethering dpa ligands. The central kink and inter-ring torsion within the dpa ligands enforces the acentric Aba2 space group of crystals of 1 and 2. Antiferromagnetic coupling (g = 2.08(2), J = –1.05(8) cm⁻³) was observed within the malonate-bridged layer motifs within the cobalt derivative 1. In contrast, the nickel congener 2 exhibited ferromagnetic coupling (g = 2.201(1), J = 0.289(1) cm⁻³).     

Neutral and cationic cyclometallated Ir(III) complexes of anthra[1,2-d]imidazole-6,11-dione-derived ligands: Syntheses, structures and spectroscopic characterisation

The syntheses of two new ligands and five new heteroleptic cyclometallated Ir(III) complexes are reported. The ligands are based upon a functionalised anthra[1,2-d]imidazole-6,11-dione core giving LH¹⁻³ incorporating a pendant pyridine, quinoline or thiophene unit respectively. Neutrally charged, octahedral complexes [Ir(ppy)₂(L¹⁻³)] are chelated by two cyclometallated phenylpyridine (ppy) ligands and a third, ancillary deprotonated ligand L¹⁻³, whilst cationic analogues could only be isolated for [Ir(ppy)₂(LH¹⁻²)][PF₆]. X-ray crystal structures for [Ir(ppy)₂(L¹)], [Ir(ppy)₂(LH¹)][PF₆] and [Ir(ppy)₂(L²)] showed the complexes adopt a distorted octahedral coordination geometry, with the anthra[1,2-d]imidazole-6,11-dione ligands coordinating in a bidentate fashion. Preliminary DFT calculations revealed that for the complexes of LH¹ and LH² the LUMO is exclusively localized on the ancillary ligand, whereas the nature of the HOMO depends on the protonation state of the ancillary ligand, often being composed of both Ir(III) and phenylpyridine character. UV-vis. and luminescence data showed that the ligands absorb into the visible region ca. 400 nm and emit ca. 560 nm, both of which are attributed to an intra-ligand CT transition within the anthra[1,2-d]imidazole-6,11-dione core. The complexes display absorption bands attributed to overlapping ligand-centred and ¹MLCT-type electronic transitions, whilst only [Ir(ppy)₂(L²)] appeared to possess typical ³MLCT behaviour (λ_em = 616 nm; τ = 96 ns in aerated MeCN). The remaining complexes were generally visibly emissive (λ_em ≈ 560-570 nm; τ < 10 ns in aerated MeCN) with very oxygen-sensitive lifetimes more indicative of ligand-centred processes.     

Redox-active antifungal cobalt(II) and copper(II) complexes with sterically hindered o-aminophenol derivatives

Co(II) complexes with 4,6-di(tert-butyl)-2-aminophenol (HL^I) and 2-anilino-4,6-di(tert-butyl)phenol (HL^II) have been synthesized and characterized by means of physico-chemical methods. The compounds HL^I and HL^II coordinate in their singly deprotonated forms and behave as bidentate O,N-coordinated ligands; their low-spin Co(II) complexes are characterized by CoN₂O₂ coordination modes and square planar geometry. Both the free ligands and their Co(II) and Cu(II) complexes (we have produced and characterized the latter before) exhibit a pronounced antifungal activity against Aspergillus niger, Fusarium spp., Mucor spp., Penicillium lividum, Botrytis cinerea, Alternaria alternata, Sclerotinia sclerotiorum, Monilia spp., which in a number of cases is comparable with that of Nystatin and Terbinafine or even higher. The reducing properties of the ligands and their metal(II) complexes, as well as their antifungal activities, were found to decrease in the order: Cu(L^I)₂ > Cu(L^II)₂ ? Co(L^I)₂ > Co(L^II)₂ > HL^I > HL^II.     

Redox-active metal(II) complexes of sterically hindered phenolic ligands: Antibacterial activity and reduction of cytochrome c

The synthesis and physico-chemical characterization of Fe(II) and Mn(II) complexes of 4,6-di-tert-butyl-3[(2-hydroxyethyl)sulphanyl]-1,2-dihydroxybenzene (HL^I) and 2-amino-4,6-di-tert-butylphenol (HL^II) were carried out. Antibacterial activity of the Co(II), Fe(II) and Mn(II) complexes was evaluated in comparison with Cu(II) complexes and three common antibiotics; it was found to follow the order: (1) Сu(L^I)₂ > Сo(L^I)₂ > Fe(L^I)₂ ? Mn(L^I)₂ > HL^I; (2) Сu(L^II)₂ > Сo(L^II)₂ > HL^II > Fe(L^II)₂ ? Mn(L^II)₂; and their reducing ability (determined electrochemically) followed the same order. Spectrophotometric investigation was carried out in order to estimate the rate of the reduction of bovine heart сytochrome c with the ligands and their metal(II) complexes. NADPH:cytochrome P450-reductase was found to increase the rate of сytochrome c reduction with HL^I and HL^II ligands, while adrenodoxin in couple with NAD(P)H: adrenodoxin reductase had no substantial effect thereon. It was shown that the reduction of сytochrome c with these compounds cannot be related solely to the facility of their oxidation оr ionization.     

A tetranuclear complex from the employment of pyridine-2,6-dimethanol in copper(II) nitrate chemistry: Synthetic,structural and magnetic studies

The use of pyridine-2,6-dimethanol (pdmH₂) in copper(II) nitrate chemistry is reported. The reaction of Cu(NO₃)₂·3H₂O with one equivalent of pdmH₂ in MeCN affords the known mononuclear complex [Cu(pdmH₂)₂](NO₃)₂ (1) in high-yield. The reaction of 1 and NaOMe in an 1:1 ratio, as well as the reaction between Cu(NO₃)₂·3H₂O, pdmH₂ and NaOMe in an 1:1:1 ratio, in MeOH gives the tetranuclear complex [Cu₄(NO₃)₂(pdmH)₄(H₂O)(MeOH)](NO₃)₂ (2) in moderate yields. The cation of 2 possesses a slightly distorted tetrahedral Cu₄ topology with a [Cu₄(μ₂-OR)₄]⁴⁺ core. The pdmH⁻ ions behave as η¹:η¹:η²:μ₂ ligands. Strong intramolecular hydrogen bonds and π–π stacking interactions provide thermodynamic stability on compound 2. Variable-temperature, solid-state dc magnetic studies were carried out on complex 2 in the 2.0–300 K range. The data indicate predominant antiferromagnetic exchange interactions and a resulting S = 0 ground state, which is expected for a solely, μ₂-alkoxide-bridged system with obtuse Cu–O–Cu bond angles that magnetically behaves as a Cu₄ ring. A simplified 1 − J model was found to be adequate to describe the variable-temperature dc susceptibility data. The data were fitted to the appropriate equation derived from the Hamiltonian H = −J₁(S₁ · S₂ + S₂ · S₄ + S₃ · S₄ + S₁ · S₃), giving the parameters J₁ = −99.5 cm⁻¹ and g = 2.11(4). The combined work demonstrates the ligating flexibility of the pdmH₂ chelate and its usefulness in the synthesis of oligo- and polynuclear Cu^II_x clusters with interesting structural and magnetic properties, without requiring the co-presence of carboxylate ligands.     

The sterically hindered salicylaldimine ligands with their copper(II) metal complexes: Synthesis,spectroscopy, electrochemical and thin-layer spectroelectrochemical features

The synthesis, structure, spectroscopic and electro-spectrochemical properties of sterically constrained Schiff-base ligands (L_nH) (n = 1, 2, and 3) (L = N-[m-(methylmercapto)aniline]-3,5-di-t-butylsalicylaldimine, m = 4, 3, and 2 positions, respectively) and their copper(II) complexes [Cu(L_n)₂] are described. Three new dissymmetric bidentate salicylaldimine ligands containing a donor set of ONNO were prepared by reaction of different primary amine with 3,5-di-t-butyl-2-hydroxybenzaldehyde (3,5-DTB). The copper(II) metal complexes of these ligands were synthesized by treating an methanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac)₂ · H₂O. The ligands and their copper complexes were characterized by FT-IR, UV–Vis, ¹H and ¹³C NMR and elemental analysis methods in addition to magnetic susceptibility, molar conductivity, and spectroelectrochemical techniques. Analytical data reveal that copper(II) metal complexes possess 1:2 metal–ligand ratios. On the basis of molar conductance, the copper(II) metal complexes could be formulated as [Cu(L_n)₂] due to their non-electrolytic nature in dimethylforamide (DMF). The room temperature magnetic moments of [Cu(L_n)₂] complexes are in the range of 1.82–1.90 B.M which are typical for mononuclear of Cu(II) compounds with a S = 1/2 spin state. The complexes did not indicate antiferromagnetic coupling of spin at this temperature. Electrochemical and thin-layer spectroelectrochemical studies of the ligands and complexes were comparatively studied in the same experimental conditions. The results revealed that all ligands displayed irreversible reduction processes and the cathodic peak potential values of (L₃H) are shifted towards negative potential values compared to those of (L₁H) and (L₂H). It is attributed to the weak-electron-donating methyl sulfanyl group substituted on the ortho (m = 2) position of benzene ring. Additionally, all copper complexes showed one quasi-reversible one-electron reduction process in the scan rates of 0.025–0.50 V s⁻¹, which are assigned to simple metal-based one-electron processes; [Cu(2+)(L_n)₂] + e⁻ → [Cu(1+)(L_n)₂]⁻. The spectral changes corresponding to the ligands and complexes during the applied potential in a thin-layer cell confirmed the ligand and metal-based reduction processes, respectively.     

Redox-active metal(II) complexes of sterically hindered phenolic ligands: Antibacterial activity and reduction of cytochrome c. Part II. Metal(II) complexes of o-diphenol derivatives of thioglycolic acid

The synthesis and physico-chemical characterization of Fe(II) and Mn(II) complexes of 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (HL^I) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfinyl]acetic acid (HL^II) were carried out. The investigation of the molecular and electronic structure of Cu(II), Ni(II), Zn(II), Fe(II) and Mn(II) complexes has been performed within the density functional theory (DFT) framework. The computed properties were compared to the experimental ones, and molecular structures of the compounds were proposed based on the array of spectral data and quantum chemical calculations. Antibacterial activity of the Fe(II) and Mn(II) complexes was evaluated in comparison with Cu(II), Co(II), Ni(II) and Zn(II) complexes and three standard antibiotics; it was found to follow the order: (1) Сu(L^I)₂ > Mn(L^I)₂ > HL^I > Ni(L^I)₂ > Zn(L^I)₂ > Fe(L^I)₂ > Co(H₂O)₂L^I; (2) Cu(L^II)₂ > Сo(L^II)₂ > Ni(L^II)₂ > Mn(H₂O)₂(L^II)₂ > Fe(L^II)₂ > HL^II > Zn(L^II)₂; their reducing ability (determined electrochemically) followed the same order. Spectrophotometric investigation was carried out in order to estimate the rate of the reduction of bovine heart сytochrome c with the ligands and their metal(II) complexes. The complexes Сu(L^I)₂, Mn(L^I)₂ and Co(L^II)₂ with the high reducing ability were found to be characterized by the highest rates of Cyt с reduction. NADPH:cytochrome P450-reductase had no substantial effect on the rate of сytochrome c reduction with HL^I and HL^II ligands.     

Synthesis,molecular and supramolecular structure,spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound

The synthesis, molecular and supramolecular structure, spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound [(UO₂)₂(L)₂(dimethylformamide)₂] (1) derived from the Schiff base ligand H₂L, obtained on condensation of 3-methoxysalicylaldehyde with 2-aminoethanol, have been described. The compound has been characterized by IR, UV–Vis, NMR and mass spectra, as well as by single crystal X-ray structure determination. The title compound crystallizes in the monoclinic P2₁/n space group with the following unit cell parameters a = 10.5713(2) Å, b = 11.9895(2) Å, c = 12.9372(2) Å, β = 102.773(3)° and Z = 2. The structure of 1 reveals that it is a dialkoxo-bridged dinuclear compound of uranium(VI) containing two deprotonated ligands, [L]²⁻, two dimethylformamide (dmf) molecules and two UO₂²⁺ centers. The coordination geometry around the uranium(VI) center is distorted pentagonal bipyramidal; two uranyl oxygens occupy the axial positions, while the basal pentagonal plane is defined by a phenoxo oxygen, two bridging alkoxo oxygens, one imine nitrogen, and one dmf oxygen. Three C–H?O type hydrogen bonds involving one uranyl oxygen, two dmf hydrogens and the imine hydrogen link the dinuclear units into a two-dimensional network. The ESI-MS spectrum of 1 in dimethylsulfoxide exhibits two peaks at m/z = 464.17 and 927.26, which are assignable to [(UO₂)₂L₂H]⁺ (60%) and [(UO₂)₂LH]⁺ (100%) cations, respectively. Cyclic voltammetric measurements of 1 reveal that the uranium(VI) center is reduced quasireversibly at E_1/2 = −1112 mV with ΔE_P = 97 mV.     

Comparison of crystal structures and magnetic properties of two Co(II) complexes containing different dicarboxylic acid ligands

Two novel cobalt(II) complexes, [Co(μ-succinato)(H₂O)₂(pyridine)₂]_n1 and {[Co₂(μ-H₂O)(μ-glutarato)₂(pyridine)₂]·pyridine}_n2 have been synthesized by a wet chemistry method. In complex 1, the Co(II) ions are linked through succinate ligands to created one-dimensional polymeric chain along the b-axis. Complex 2 consists of a polymeric chain of dinuclear Co(II) moieties in which two cobalt(II) ions are linked through a bridging water and two bridging carboxylate groups from two glutarate ligands. The glutarate ligands in complex 2 display two coordination modes, interbinuclear bridging and intrabinuclear bridging. All the bond angles of the alkyl chain in complex 2 are between 115.7° and 118.5°, supporting the gauche conformation. Free pyridine molecules were found in the cavities between the chains. Two strong intramolecular hydrogen bonds are observed between the coordinated water and the uncoordinated carboxylate oxygen atom in both complexes. Complex 2 is further stabilized by π–π stacking of pyridine molecules. Complex 1 is a paramagnet (C = 3.50(1) cm³ K mol and θ = −5.0(5) K) and complex 2 exhibits a broad maximum at 4 K due to weak coupling within the dimeric unit.     

Preparation,spectroscopic characterization and X-ray crystal and molecular structures of nickel(II), copper(II) and zinc(II) complexes of the Schiff base formed from isatin and S-methyldithiocarbazate (Hisa-sme)

Complexes of general formula, [M(isa-sme)₂] · n(solvate) [M = Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺; isa-sme = monoanionic form of the Schiff base formed by condensation of isatin with S-methyldithiocarbazate; n = 1 or 1.5; solvate = MeCN, DMSO, MeOH or H₂O] have been synthesized and characterized by a variety of physicochemical techniques. An X-ray crystallographic structure determination of the [Ni(isa-sme)₂] · MeCN complex reveals a six-coordinate, distorted octahedral geometry. The two uninegatively charged, tridentate, Schiff base ligands are coordinated to the nickel(II) ion meridionally via the amide O-atoms, the azomethine N-atoms and the thiolate S-atoms. By contrast, the crystal structure of [Zn(isa-sme)₂] · MeOH shows a four-coordinate distorted tetrahedral geometry. The two dithiocarbazate ligands are coordinated as N, S bidentate chelates with the amide O-atom not coordinated. The structure of the copper(II) complex [Cu(isa-sme)₂] · DMSO is complicated and comprises two different complexes in the asymmetric unit, one four- and the other five-coordinate. The four-coordinate copper(II) has a distorted (flattened) tetrahedral geometry as seen in the Zn(II) analogue whereas the five-coordinate copper(II) has a distorted square-pyramidal geometry with one ligand coordinated to the copper(II) ion as a tridentate (N, S, O) ligand and the other coordinated as a bidentate N, S chelate. EPR spectroscopy indicates that in solution only one form is present, that being a distorted tetrahedral complex.     

Ru(η-1,3,5-cyclooctatriene)(η-dimethyl fumarate)2: a novel, versatile zerovalent ruthenium complex with electron-deficient olefinic ligands

The reactivity of a novel zerovalent ruthenium complex, Ru(η⁶-cot)(η²-dmfm)₂ (cot = 1,3,5-cyclooctatriene, dmfm, =dimethyl fumarate), which is readily prepared from Ru(η⁴-cod)(η⁶-cot) (cod = 1,5-cyclooctadiene) and dmfm was examined. The reaction with monodentate phosphine or amine ligands gave Ru(η⁶-cot)(dmfm)(L) (L = ligand) via dissociation of dmfm. Among bidentate phosphines, dppm (dppm = bis(diphenylphosphino)methane) reacted to give Ru(η⁴-cot)(dmfm)(dppm) along with releasing a dmfm ligand. In the case of dppe (dppe = 1,2-bis(diphenylphosphino)ethane), two types of complexes were obtained depending on the reaction conditions, Ru(dmfm)(dppe)₂ and an alkyl alkenyl complex; in the formation of the latter complex, sp² C-H bond activation of dmfm occurred. Ru(η⁴-cot)(dmfm)(N^?N) and Ru(dmfm)₂ (N^?N^?N) were formed by reacting with bidentate and tridentate nitrogen ligands. The reactions with arenes gave π-coordinated complexes, Ru(η⁶-arene)(dmfm)₂. p-Quinones and a p-biqunone reacted to give Ru(η⁶-cot)(p-quinone) and {Ru(η⁶-cot)}₂(p-biquinone), respectively, along with the dissociation of two dmfm ligands. It was found that low-valent ruthenium complexes preferably bear both electron-donating and accepting ligands simultaneously to be thermodynamically stable.     

Preparation and structural characterization of nickel(II), cobalt(II), zinc(II) and tin(IV) complexes of the isatin Schiff bases of S-methyl and S-benzyldithiocarbazates

The molecular structures of the isatin Schiff bases of S-methyldithiocarbazate (Hisasme) and S-benzyldithiocarbazate (Hisasbz) have been determined by X-ray diffraction and their complexes of general formula [ML₂]·n(solvate) [M = Co²⁺, Ni²⁺, Zn²⁺; L = anionic forms of Hisasme or Hisasbz; solvate = DMF, DMSO; n = 1, 2] and [Sn(L)Ph₂Cl]·nMeOH (n = 0, 1) have been synthesized and characterized by a variety of physicochemical techniques and X-ray diffraction. The bis-ligand complexes, [Ni(isasbz)₂]·2DMSO and [Co(isasme)₂]·DMF have a six-coordinate, distorted octahedral geometry with the two uninegatively charged tridentate ONS ligands coordinated to the metal ions meridionally via the amide O-atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. By contrast, the crystal structure of [Zn(isasbz)₂]·2DMF shows a four-coordinate distorted tetrahedral geometry with the two Schiff bases coordinated as NS bidentate ligands via the azomethine nitrogen atoms and the thiolate sulfur atoms. Steric constraints of the rigid tridentate ligands lead to unusual ‘pseudo-coordination’ of the O-donors which occupy sites close to the metal but too distant to be considered as true coordinate bonds.The crystal structures of the tin(IV) complexes [SnLPh₂Cl]·nMeOH (L = isasme and isasbz; n = 0, 1) also show that the Schiff bases act as monoanionic bidentate NS chelating agents coordinating the tin(IV) ion via the azomethine nitrogen atoms and the thiolate sulfur atoms, the tin atom in each complex is five-coordinate with a highly distorted geometry intermediate of square pyramidal and trigonal bipyramidal. Again Sn?O contacts are weak and do not qualify as coordinate bonds.     

A new family of pyrazolyl-based anionic bidentate ligands and crystal structure of bis(N-phenyl-2-pyrazolyl-1-carboximidothioato)copper(II)

Three new N,S-donor bidentate pyrazolyl-based ligands abbreviated as [PhNCSPz]⁻, 1, [PhNCSPz^Me2]⁻, 2, and [PhNCSPz^Ph2]⁻, 3, have been synthesized in THF by direct mixing of phenylisothiocyanide with suspension of appropriate sodium-pyrazolate salts and characterized by the common spectroscopic and analytical methods. The Cu(II) complexes of these anionic chelate ligands have been characterized and the crystal structure of Cu(PhNCSPz)₂, 4, has been determined. The space group of complex is P2₁c, with a = 5.9313(3), b = 21.206(1) Å, c = 8.0667(4) Å, β = 103.822(1)°.     

Stereoselective synthesis of cobalt(III) anionic complexes with chiral pyruvylaminoacid oximes and metal–ligand interactions in aqueous solution

A series of cobalt(III) anionic complexes with hydroxyimino analogs of dipeptides – oximes of pyruvylglycine, pyruvyl-l-alanine, pyruvyl-l-methionine and pyruvyl-l-phenylalanine (H₂pamaco, amac = amino acid) of composition Cat₃[Co(H₋₁pamaco)₂] · nH₂O (Cat – a monovalent metal cation) has been synthesized and investigated by UV–Vis, CD and ¹H NMR spectroscopy. It was established that for the two latter ligands, non-racemic mixtures of two diastereomeric complexes were formed as a result of synthesis. In comparison with the complex containing pyruvyl-l-alanine, in which the relative content of R (C₂) and S (C₂) isomers is approximately equal, the presence of bulky substituents in the molecules of Met- and Phe-containing ligands results in a significant discrimination in formation of the S (C₂) isomer. This conclusion was drawn upon analysis of the CD and NMR spectral data as well as from molecular modeling. The relative content of the diastereomers was evaluated on the basis of NMR data. The protonation constants of the ligands have been determined in aqueous solution by glass electrode potentiometry, whereas their interactions with Co(II) were studied both under argon and oxygen atmosphere.     

Chemistry related to cluster-borane analogues of the cyclopentadienide anion and ferrocene: New developments

A review on cluster-borane analogues of the cyclopentadienide anion (Cp) and ferrocene is presented. Analogues of Cp that have been so far isolated and characterised are the 11-vertex triheteroboranes of general structure [nido-E₃B₈H₈]⁻ (where E = CH or P and their combinations), the molecules of which contain an open pentagonal face. These anions were used as effective ligands for the preparation of “half- and full-sandwich” complexes [CpFeE₃B₈H₈] and [Fe(E₃B₈H₈)₂], respectively - analogues of ferrocene. Developments in this area of cluster-borane chemistry that include recent results in the synthesis and Fe-complexation reactions of 11-vertex tricarbaboranes (tricarbollides), phosphadicarbollides, and diphosphacarbollides are the subject of this work.     

Vanadiumoxo–aroylhydrazone complexes: Synthesis,structure and DFT calculations

The aroylhydrazone Schiff base ligands (E)-N’-(2-hydroxybenzylidene)benzohydrazide = H₂L¹, (E)-N’-(2-hydroxy-3-methoxybenzylidene)benzohydrazide = H₂L² and = (E)-N’-(5-bromo-2-hydroxybenzylidene)benzohydrazide = H₂L³ gave the vanadium(V)oxo-aroylhydrazone complexes [V^VOL¹(OCH₃)(OHCH₃] (1), [V^VOL²(OCH₃)(OHCH₃]·CH₃OH (2) and [V^VOL³(OCH₃)(OHCH₃] (3) on reaction with vanadium(IV) oxide acetylacetonate. The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV–Vis, ¹H NMR). Single crystal X-ray analysis was performed with 3. In methanol solution six-coordinated V^VOL³(OCH₃)(OHCH₃) was formed. V^IV was oxidized to V^v by aerial oxygen in the synthesis. In the VO₅N coordination sphere the alcohol oxygen lies trans to the oxo oxygen. The general V–O bond length order is oxo < methoxylato < phenoxidic < enolato < alcoholic. The complexes are mononuclear, but intermolecular O–H?N hydrogen bonding affords a zigzag chain. DFT calculations on complex 3 reproduced the geometric parameters, IR and UV–Vis spectroscopic data well in a reasonable range.     

Cu(II) and Pd(II) complexes of N-(2-hydroxybenzyl)aminopyridines

N-(2-Hydroxybenzyl)aminopyridines (Lⁱ) react with Cu(II) and Pd(II) ions to form complexes in the compositions Cu(Lⁱ)₂(CH₃COO)₂ · nH₂O (n = 0, 2, 4), Pd(Lⁱ)₂Cl₂ · nC₂H₅OH (n = 0, 2) and Pd(L²)₂Cl₂ · 2H₂O. In the complexes, the ligands are neutral and monodentate which coordinate through pyridinic nitrogen. Crystal data of the complexes obtained from 2-amino pyridine derivative have pointed such a coordinating route and comparison of the spectral data suggests the validity of similar complexation modes of other analog ligands. Cu(II) complex of N-(2-hydroxybenzyl)-2-aminopyridine (L¹), [Cu(L¹)₂(CH₃COO)₂] has slightly distorted square planar cis-mononuclear structure which is built by two oxygen atoms of two monodentate carboxylic groups disposed in cis-position and two nitrogen atoms of two pyridine rings. The remaining two oxygen atoms of two carboxylic groups form two Cu and H bridges containing cycles which joint at same four coordinated copper(II) ion. IR and electronic spectral data and the magnetic moments as well as the thermogravimetric analyses also specify on mononuclear octahedric structure of complexes [Cu(L²)₂(CH₃COO)₂ · 2H₂O] and [Cu(L³)₂(CH₃COO)₂ · 4H₂O] where L² and L³ are N-(2-hydroxybenzyl)-2- or 3-aminopyridines, respectively.     

Synthesis, characterization, and near-infrared luminescent properties of the ternary thulium complex covalently bonded to mesoporous MCM-41

The crystal structure of a ternary Tm(DBM)₃phen complex (DBM=dibenzoylmethane; phen=1, 10-phenanthroline) and the synthesis of hybrid mesoporous material in which the complex covalently bonded to mesoporous MCM-41 are reported. Crystal data: Tm(DBM)₃phen C₅₉H₄₇N₂O₇Tm, monoclinic, P21/c, a=19.3216(12) Å, b=10.6691(7) Å, c=23.0165(15) Å, α=90°, β=91.6330(10)°, γ=90°, V=4742.8(5) Å³, Z=4. The properties of the Tm(DBM)₃phen complex and the corresponding hybrid mesoporous material [Tm(DBM)₃phen-MCM-41] have been studied. The results reveal that the Tm(DBM)₃phen complex is successfully covalently bonded to MCM-41. Both Tm(DBM)₃phen complex and Tm(DBM)₃phen-MCM-41 display typical near-infrared (NIR) luminescence upon excitation at the maximum absorption of the ligands, which contributes to the efficient energy transfer from the ligands to the Tm³⁺ ion, an antenna effect. The full width at half maximum (FWHM) centered at 1474 nm in the emission spectrum of Tm(DBM)₃phen-MCM-41 is 110 nm, which is the potential candidate of broadening amplification band from C band (1530-1560 nm) to S⁺ band (1450-1480 nm) in optical area.