Syntheses, structures, and mesomorphic properties of two series of oxovanadium(IV) salen and salpn complexes with 4-substituted long alkoxy chains

Two series of oxovanadium(IV) salen and salpn complexes containing 4-substituted alkoxy chains of aromatic rings, [VO((4-C_nH_2n+1O)₂salen)] (n = 3 (1), 4 (2), 6 (3), 8 (4), 10 (5), 12 (6), 14 (7), 16 (8), 18 (9), and 20 (10) and salen = N,N′-ethylenebis(salicylideneiminato)), and [VO((4-C_nH_2n+1O)₂salpn)] (n = 8 (11), 10 (12), 12 (13), 14 (14), 16 (15), and 18 (16) and salpn = N,N′-propylenebis(salicylideneiminato)), have been prepared and their mesomorphic properties have been investigated. The crystal structures of 1-9 except for 7 by an X-ray crystallographic analysis have been revealed. Complexes 4-9 in the solid state have been confirmed as novel bilayer crystal structures composed of only the VO(IV) complex without linear chains via the VO units. The VO(IV) complexes with longer alkoxy chains of 8-10 transferred from the bilayer crystal to the bilayer metallomesogens (liquid crystals). Based on the X-ray analyses and the precise extinction rules for 8-10 with the bilayer metallomesogens, complexes 8-10 were identified as the liquid crystalline (M(Pa2₁)) phase derived from 80 layer groups. On the other hand, the 4-alkoxysalpn complexes of 14-16 showed the unusual rectangular columnar mesophase (Col_r) with the linear chain via the VO units supported by the existence of the VO stretching band characteristic of weak linear chain formation via the VO units in the liquid crystal.     

Divanadium(V) complexes with 4-R-benzoic acid (1-methyl-3-oxo-butylidene)-hydrazides: Syntheses, structures and properties

In acetonitrile, reactions of bis(acetylacetonato)oxidovanadium(IV) ([VO(acac)₂]) with 4-R-benzoylhydrazine in 1:1 mole ratio provide coordinatively symmetrical complexes (1-5) of the {OV(μ-O)VO}⁴⁺ motif in 40-47% yields. On the other hand, in methanol the same reactants provide complexes (6-10) containing the {OV(μ-OMe)₂VO}⁴⁺ core in 37-50% yields. In both series of complexes, the ligand is the O,N,O-donor deprotonated Schiff base system 4-R-benzoic acid (1-methyl-3-oxo-butylidene)-hydrazide formed by template condensation of acac⁻ with 4-R-benzoylhydrazine (R = H, Cl, OMe, NO₂ and NMe₂). All the complexes have been characterized by elemental analysis, magnetic and spectroscopic (IR, UV-Vis and NMR) measurements. Molecular structures of three representative complexes (4, 6 and 7) have been determined by X-ray crystallography. In each complex, the dianionic planar ligand is coordinated to the metal centre via the enolate-O, the imine-N and the O-atom of the deprotonated amide functionality. Cyclic voltammetric measurements in dichloromethane revealed that complexes 1-5 are redox inactive, while complexes 6-10 display a metal centred reduction in the potential range −0.06 to 0.0.32 V (versus Ag/AgCl).     

Synthesis, characterization and ethylene oligomerization behavior of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridylnickel dihalides

A series of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (L1-L6) was synthesized and fully characterized. They reacted with NiCl₂ or (DME)NiBr₂ to form the corresponding N^N^N tridentate nickel dichlorides (C1-C6) or dibromides (C7-C12). All nickel complexes were characterized by elemental analysis and infrared spectroscopy, while the X-ray diffraction study reveals the distorted octahedral geometry of representative nickel dichloride complex C3 and nickel dibromide complex C7. All nickel complexes, activated with either Et₃Al₂Cl₃ or Et₂AlCl, showed good activities in ethylene oligomerization, and notably remarkably high selectivity of α-olefins was achieved in the presence of Et₃Al₂Cl₃. The chloro-substituted ligands enhanced the activities of complexes in ethylene polymerization.     

Iridium assisted S-H and C-H activation of benzaldehyde thiosemicarbazones. Synthesis, structure and electrochemical properties of the resulting complexes

Reaction of five 4-R-benzaldehyde thiosemicarbazones (R = OCH₃, CH₃, H, Cl and NO₂) with [Ir(PPh₃)₃Cl] in refluxing ethanol in the presence of a base (NEt₃) affords complexes of three different types, viz. 1-R, 2-R and 3-R. In the 1-R complexes the thiosemicarbazone is coordinated to iridium as a monoanionic bidentate N,S-donor forming a four-membered chelate ring. Two triphenylphosphines, a hydride and a chloride are also coordinated to the metal center. The 2-R complexes are very similar in composition and stereochemistry to the corresponding 1-R complexes, except that a second hydride is bound to iridium instead of the chloride. In the 3-R complexes, the thiosemicarbazones are coordinated to iridium as dianionic tridentate C,N,S-donors forming two adjacent five-membered chelate rings. Two triphenylphosphines and a hydride are also coordinated to the metal center. Structures of the 1-NO₂, 2-NO₂ and 3-NO₂ complexes have been determined by X-ray crystallography. Reaction of the same 4-R-benzaldehyde thiosemicarbazones with [Ir(PPh₃)₃Cl] in refluxing toluene in the presence of NEt₃ affords complexes of two types, viz. 3-R and 4-R. The 4-R complexes are very similar in composition and stereochemistry to the corresponding 3-R complexes, except that a chloride is bound to iridium instead of the hydride. Structure of the 4-CH₃ complex has been determined by X-ray crystallography. In all the complexes the two PPh₃ ligands are trans. All the complexes show intense MLCT transitions in the visible region. Cyclic voltammetry on the complexes shows an Ir(III)-Ir(IV) oxidation on the positive side of SCE followed by an oxidation of the coordinated thiosemicarbazone. A reduction of the coordinated thiosemicarbazone is also observed on the negative side of SCE.     

Synthesis, crystal structure and magnetic characterization of a series of four phenoxo-bridged binuclear manganese(III) Schiff base complexes

A family of four new phenoxo-bridged binuclear manganese(III) complexes of the general formula, [Mn(L)(X)]₂ where L = [N,N′-bis(salicylidene)]propane-1,2-diamine and X = salicylaldehyde anion (sal⁻) (1); NCS⁻ (2); NCO⁻ (3) and [Mn(L′)(N₃)]₂·2C₂H₅OH (4) where L′ = [N,N′-bis(2-hydroxyacetophenylidene)]propane-1,2-diamine has been prepared. The syntheses have been achieved by reacting manganese perchlorate with 1,2-diaminopropane and salicylaldehyde (or 2-hydroxyacetophenone for 4) or along with the respective pseudohalides so that the tetradentate Schiff base H₂L or H₂L′ is obtained in situ to bind the Mn(III) ion. The complexes have been characterized by IR spectroscopy, elemental analysis, crystal structure analysis and variable-temperature magnetic susceptibility measurements. The single crystal X-ray diffraction studies show that the compounds are isostructural containing dimeric Mn(III) units with bridging phenolate oxygen atoms. Low temperature magnetic studies indicate that the complexes 1-3 exhibit intradimer ferromagnetic exchange as well as single-molecule magnet (SMM) behavior while complex 4 is found to undergo an intradimer antiferromagnetic coupling.     

Synthesis, characterization, and protein tyrosine phosphatases inhibition activities of oxovanadium(IV) complexes with Schiff base and polypyridyl derivatives

Seven new mixed-ligand vanadyl complexes, [V^IVO(5-Br-SAA)(NN)] and [V^IVO(2-OH-NAA)(NN)] (1-7) (5-Br-SAA for 5-bromosalicylidene anthranilic acid, 2-OH-NAA for 2-hydroxy-1-naphthaldehyde anthranilic acid and NN for N,N′-donor heterocyclic base, namely, 2,2′-bipyridine (bpy, 1 and 5), 1,10-phenanthroline (phen, 2 and 6), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq, 3 and 7), dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 4)), were synthesized and characterized. X-ray crystal structure of [V^IVO(5-Br-SAA)(phen)] revealed a distorted octahedral geometry with the Schiff base ligand coordinated in a tridentate ONO-fashion and the phenanthroline ligand in a bidentate fashion. Density-functional theory (DFT) calculations suggest a similar structure and the same coordination mode for all the other oxovanadium complexes synthesized. Biochemical assays demonstrate that the mixed-ligand oxovanadium(IV) complexes are potent inhibitors of protein tyrosine phosphatase 1B (PTP1B), with IC₅₀ values approximately 41-75 nM. Kinetics assays suggest that the complexes inhibit PTP1B in a competitive manner. Notably, they had moderate selectivity of PTP1B over T-cell protein tyrosine phosphatase (TCPTP) (about 2-fold) and good selectivity over Src homology phosphatase 1 (SHP-1) (about 4∼7-fold). Thus, these mixed-ligand complexes represent a promising class of PTP1B inhibitors for future development as anti-diabetic agents.     

Salicylamide and salicylglycine oxidovanadium complexes with insulin-mimetic properties

Reaction of N-(2-hydroxybenzyl)-N-(2-picolyl) glycine (H₂papy) with VOSO₄ in water gives the oxidovanadium(V) oxido-bridged dimer [{(papy)(VO)}₂ μ-O)] (1). Similarly, reaction of N-(2-hydroxybenzyl) glycine (H₂glysal) with VOSO₄ gives [(glysal)VO(H₂O)] (2) and reaction of salicylamide (Hsalam) with VOSO₄ in methanol gives [(salam)₂VO] (3). The crystal structure of the oxido-bridged complex 1 is reported. The insulin-mimetic activity of all three complexes was evaluated with respect to their ability to phosphorylate protein kinase B (PKB). The speciations of complexes 1 and 2 were studied over the pH range 2-10. Complex 1 shows greater stability over the whole pH range but only 2 and 3 exhibit an insulin-mimetic effect.     

Synthesis, characterization and anti-diabetic effect of bis[(1-R-imidazolinyl)phenolato]oxovanadium(IV) complexes

The five-coordinate oxovanadium(IV) complexes; [VO(pimin)₂] (1a), [VO(Etpimin)₂] (2) and [VO(EtOHpimin)₂] (3), were prepared by reacting the ligands; 2-(2′-hydroxyphenyl)-1H-imidazoline (piminH), 2-(2′-hydroxyphenyl)-1-ethylimidazoline (EtpiminH) and 2-(2′-hydroxyphenyl)-1-ethanolimidazoline (EtOHpiminH), with VOSO₄. The complexes were characterized by elemental analysis, IR, UV-Vis and cyclic voltammetry. All complexes show VO stretching vibrations between 932 and 987 cm⁻¹. The presence of three d-d transition occurring between 400 and 625 nm and the irreversible oxidation (V^IV → V^V) between 400 and 490 mV confirm the d¹ electronic configuration of the complexes. The solid state structures of [VO(pimin)₂] (1a) and its autoxidation hydrolysis product [VO₂(pimin)(piminH′)] (1b) were determined by single crystal X-ray diffraction. The geometry of [VO(pimin)₂] was found to be intermediate between trigonal bipyramidal and square pyramidal and sits on a crystallographic twofold axis, while the geometry of [VO₂(pimin)(piminH′)] was distorted trigonal bipyramidal. Potentiometric titrations were used to determine the protonation and stability constants for the ligands and oxovanadium(IV) complexes, respectively. The species existing over a biological pH range were also investigated. The in vitro studies indicated that the oxovanadium(IV) complexes were effective in enhancing glucose uptake in the 3T3-L1 adipocytes, C2C12 muscle cells and Chang liver cell lines. In these cell lines, the anti-hyperglycemic effect was equivalent to or surpassed the effect of metformin.     

Ternary oxovanadium(IV) complexes with amino acid-Schiff base and polypyridyl derivatives: synthesis, characterization, and protein tyrosine phosphatase 1B inhibition

To investigate the structure-activity relationship of vanadium complexes in inhibiting protein tyrosine phosphatase1B (PTP1B), eight mixed-ligand oxovanadium(IV) complexes, [V^IVO(SalAla)(NN)] (H₂SalAla for salicylidene alanine, NN for N,N′-donor heterocyclic base, namely, 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq, 3), dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 4)), [V^IVO(SalLys)(dpq)] (5), [V^IVO(SalLys)(dppz)] (6), [V^IVO(SalAsp)(dppz)], (7) and [V^IVO(SalTrp)(dppz)] (8)), of which 3-8 are new, have been prepared and characterized by elemental analysis, infrared, UV-visible, electrospray ionization mass spectrometry and conductivity. The molar conductance data confirmed the non-electrolytic nature of the complexes in DMSO solution. The coordination in [V^IVO (SalAla)(phen)] (2) was confirmed by X-ray crystal structure analysis. The oxidation state of V(IV) with d¹ configuration in 2 was confirmed by EPR. The speciation of VO-SalAla-phen in aqueous solution was investigated by potentiometric pH titrations. The results indicate that the main species are two ternary complexes at the pH range 7.0-7.4. Biochemical assays demonstrate that the mixed-ligand oxovanadium(IV) complexes are potent inhibitors of PTP1B with IC₅₀ values in the range of 62-597 nM, approximately 3-10 fold weaker in potency than those of similar mixed-ligand oxovanadium(IV) complexes of salicylidene anthranilic acid (SAA) derivative with polypyridyl ligands, except complex 8, which exhibits comparable or better inhibition activity than those of the mixed-ligand oxovanadium(IV) complexes of SAA derivative with polypyridyl ligands. The results demonstrate that the structures of vanadium complexes influence the PTP1B inhibition activity. Kinetics assays reveal that complex 2 inhibits PTP1B in a competitive manner.     

Synthesis, characterization, and properties of binuclear ruthenium complexes with dendritic side chains on their bridges

Three binuclear ruthenium complexes with dendritic side chains, 1,4-[RuCl(CO)(PMe₃)₃CHCH]₂C₆H₂-2,5-(G_n)₂ with G_n = G₀ (1), G₁ (2), and G₂ (3), have been synthesized by the reactions of the corresponding diethynylaryls with the ruthenium hydride complex [RuHCl(CO)(PPh₃)₃] and subsequent ligand exchange with PMe₃. The complexes have been characterized by elemental analysis, NMR, and UV-Vis spectrophotometry. The structure of complex 1 has been determined by X-ray crystallography. Their electrochemical properties have been investigated. Electrochemical studies in solution may imply that the two metal centers in complexes 1-3 have good electronic communications between each other. However, the electron communication is not effectively enhanced with increasing generation of the dendrons in solution.     

Coordination polymers of 1,8-bis(2-methylthioethoxy)anthraquinone and 1,5-bis(2-methylthioethoxy)anthraquinone with Ag(I): Synthesis and X-ray crystallography

The reaction of 2-(methylthioethanol) with 1,8-dichloroanthraquinone and 1,5-dichloroanthraquinone in THF with base produces 1,8-bis(2-methylthioethoxy)anthraquinone (1) and 1,5-bis(2-methylthioethoxy)anthraquinone (2), respectively. Silver(I) complexes of 1 and 2 have been synthesized after combination with [Ag(CH₃CN)₄]BF₄ in 1:1 M ratio to yield, [(1,8-bis(2-methylthioethoxy)anthraquinone)Ag]BF₄, (3) and [(1,5-bis(2-methylthioethoxy)anthraquinone)Ag·CH₃CN]BF₄, (4). X-ray crystal structures of the free ligand (1) and the Ag(I) complexes (3 and 4) are reported. The intraannular carbonyl group forms a coordinate-covalent bond with Ag(I) and, in the solid state, both silver(I) complexes are found as coordination polymers.     

Synthesis, structural characterization and electrochemical activity of oxidovanadium(IV/V) complexes of a diprotic ONS chelating ligand

The present work reports the chemistry of a few oxidovanadium(IV) and (V) complexes of the ONS chelating ligand S-benzyl-β-N-(2-hydroxyphenylethylidine) dithiocarbazate (H₂L). Major objective of this work is to arrive at some general conclusions about the influence of binding environment generated by the replacement of an O-donor center by a S-donor point in a ligand (of a similar arrangement of the other O- and N-donor points) on the redox behavior and on the structural features of comparable [VO(OEt)(ONS)] and [VO(OEt)(ONO)] complexes. Synthesis, characterization by various physicochemical techniques (UV-Vis, IR, EPR and elemental analysis), exploration of electrochemical activity of the oxidovanadium(V) complex [V^VO(OEt)L] (1), the mixed ligand complex [V^VO(N-O)L] (3) (where N-O is the mono anion of 8-hydroxyquinoline) and a binuclear complex [V^VO(OEt)L]₂(μ-4,4′-bipy) (2) are reported. Similar studies on of mixed ligand oxidovanadium(IV) complexes of the formula [V^VO(N-N)L] (4,5) (where N-N = 2,2′-bipy and o-phen) are also presented here. The [V^VO(OEt)L] complex is pentacoordinated and distorted square pyramidal, while the [V^IV(N-N)L] complexes are hexacoordinated and octahedral. Structural features of the complex 1 were compared with the corresponding aspects of the previously reported analogous complex [V^VO(OEt)(ONO)] (1′).     

Heterocyclic thioamide derivatives of coinage metals (Cu, Ag): Synthesis, structures and spectroscopy

Heterocyclic thioamides, namely, imidazolidine-2-thione (imdzSH), 1-methyl-1, 3-imidazoline-2-thione (mimzSH), thiazolidine-2-thione (tzdSH) and 2,4-dithiouracil (dtucH₂) with silver(I)/copper(I) salts in presence of triphenyl phosphine (PPh₃) have yielded complexes of different nuclearity: mononuclear, [Ag(η¹-S-HL)(PPh₃)₂Cl] (HL = imdzSH 1, mimzSH 2, tzdSH 3), dinuclear, [Ag₂(η¹-S-tzdSH)₂(μ-S-tzdSH)₂(PPh₃)₂](NO₃)₂4, and polynuclear, {Cu(μ-S,S-dtucH₂)(PPh₃)₂X} (X = Cl 5, Br 6, I 7). All complexes have been characterized using analytical data, IR and multinuclear NMR spectroscopy (¹H, ¹³C and ³¹P) and single crystal X-ray crystallography. The thio-ligands are bonded to the metal centers as neutral sulfur donors. The geometry around each metal center is distorted tetrahedral. Complexes 5-7 represent first examples of polymers of 2,4-dithiouracil in its coordination chemistry with metal salts. The hydrogen bonding interactions lead to the formation of 1D (2, 3, 7) and 2D (1, 4-6) sheet structures.     

Palladium(II) complexes of quinolinylaminophosphonates: synthesis, structural characterization, antitumor and antimicrobial activity

Three types of palladium(II) halide complexes of quinolinylaminophosphonates have been synthesized and studied. Diethyl and dibutyl [α-anilino-(quinolin-2-ylmethyl)]phosphonates (L1, L2) act as N,N-chelate ligands through the quinoline and aniline nitrogens giving complexes cis-[Pd(L1/L2)X₂] (X═Cl, Br) (1-4). Their 3-substituted analogues [α-anilino-(quinolin-3-ylmethyl)]phosphonates (L3, L4) form dihalidopalladium complexes trans-[Pd(L3/L4)₂X₂] (5-8), with trans N-bonded ligand molecules only through the quinoline nitrogen. Dialkyl [α-(quinolin-3-ylamino)-N-benzyl]phosphonates (L5, L6) give tetrahalidodipalladium complexes [Pd₂(L5/L6)₃X₄] (9-12), containing one bridging and two terminal ligand molecules. The bridging molecule is bonded to the both palladium atoms, one through the quinoline and the other through the aminoquinoline nitrogen, whereas terminal ligand molecules are coordinated each only to one palladium via the quinoline nitrogen. Each palladium ion is also bonded to two halide ions in a trans square-planar fashion. The new complexes were identified and characterized by elemental analyses and by IR, UV-visible, ¹H, ¹³C and ³¹P nuclear magnetic resonance and ESI-mass spectroscopic studies. The crystal structures of complexes 1-4 and 6 were determined by X-ray structure analysis. The antitumor activity of complexes in vitro was investigated on several human tumor cell lines and the highest activity with cell growth inhibitory effects in the low micromolar range was observed for dipalladium complexes 11 and 12 derived from dibutyl ester L6. The antimicrobial properties in vitro of ligands and their complexes were studied using a wide spectrum of bacterial and fungal strains. No specific activity was noted. Only ligands L3 and L4 and tetrahalidodipalladium complexes 9 and 11 show poor activities against some Gram positive bacteria.     

Photocytotoxicity and near-IR light DNA cleavage activity of oxovanadium(IV) Schiff base complexes having phenanthroline bases

Oxovanadium(IV) complexes [VO(L)(B)] (1-3), where H₂L is a Schiff base ligand 2-(2-hydroxybenzylideneamino)phenol and B is 1,10-phenanthroline (phen for 1), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq for 2) or dipyrido[3,2-a:2′,3′-c]phenazine (dppz for 3), have been prepared, characterized and their DNA binding property and photo-induced DNA cleavage activity studied. Complex 3 which is structurally characterized by X-ray crystallography shows the presence of an oxovanadium(IV) moiety in a six coordinate VO₃N₃ coordination geometry. The complexes show a d-d band within 800-850 nm in DMF. The complexes display an oxidative response near 0.7 V versus SCE for V(V)-V(IV) and a reductive response within −1.1 to −1.3 V due to V(IV)-V(III) couple in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA giving binding constant values of 4.2 × 10⁴ to 1.2 × 10⁵ M⁻¹. The complexes do not show any “chemical nuclease” activity in dark. The dpq and dppz complexes are photocleavers of plasmid DNA in UV-A light of 365 nm via ¹O₂ pathway and in near-IR light (752.5 to 799.3 nm IR optics) by HO^• pathway. Complex 3 exhibits significant photocytotoxicity in visible light in HeLa cells giving IC₅₀ value of 13 μM, while it is less toxic in dark (IC₅₀ = 97 μM).     

Extended structures of three new coordination polymers based on 1,10-phenanthroline derivatives and 1,4-benzenedicarboxylate mixed ligands: Preparation, structural characterization and properties

Three coordination polymers, namely, [Cd(HOIP)₂(1,4-bdc)] (1), [Cu(HOIP)(1,4-bdc)] (2) and [Cu(PDIP)(1,4-bdc)] (3) (HOIP = 2-(4-hydroxylbenzene) imidazo[4,5-f]1,10-phenanthroline, PDIP = 2-(3-pyridine) imidazo[4,5-f]1,10-phenanthroline, and 1,4-bdc = 1,4-benzenedicarboxylate), have been synthesized under the hydrothermal conditions. All complexes have been characterized by elemental analyses, IR and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 possesses infinite one-dimensional (1D) chain bridged by 1,4-bdc ligands, complexes 2 and 3 both exhibit two-dimensional (2D) (4,4) network structures based on dinuclear [Cu₂O₂] units. However, the weak interactions are different in complexes 1-3. Moreover, the thermal properties of all complexes, fluorescence property of 1, and the electrochemical behavior of 3 are also reported in this paper.     

A series of oxo-vanadium(IV) complexes containing mixed ligands of poly(pyrazolyl)borate and organic carboxylic acid: Synthesis, structural characterization and primary study of bromination reaction activities

A series of oxo-vanadium(IV) complexes: Tp^∗VO(pzH^∗)(CH₃COO) (1), Tp^∗VO(pzH^∗)(CCl₃COO) (2), Tp^∗VO(pzH^∗)(C₆H₅COO) (3), Tp^∗VO(pzH^∗)(m-NO₂-C₆H₄COO)·CH₃CN (4) and [Tp^∗VO(pzH^∗)(H₂O)]⁺[m-NO₂-C₆H₄-SO₃]⁻·CH₃OH (5) (Tp^∗ = hydrotris(3,5-dimethylpyrazolyl)borate; pzH^∗ = 3,5-dimethylpyrazole) are synthesized in methanol solution under physiological conditions. They are characterized by elemental analysis, IR, UV-Vis and X-ray crystallography. Structural analyses show that the vanadium atoms in complexes 1-5 are all in a distorted-octahedral environment with the N₄O₂ donor set, and intra- or inter-hydrogen bonding linkages have been also observed in each complex. Bromination reaction activity of the complexes has been evaluated by the method with phenol red as organic substrate in the presence of H₂O₂, Br⁻ and phosphate buffer, indicating that they can be considered as potential functional model vanadium-dependent haloperoxidases. In addition, thermal analysis and quantum chemistry calculations were also performed and discussed in detail.     

Synthesis, structure, and catalytic ethylene oligomerization of nickel(II) and cobalt(II) complexes with symmetrical and unsymmetrical 2,9-diaryl-1,10-phenanthroline ligands

A series of nickel(II) and cobalt(II) complexes, NiX₂L (X = Cl, Br; 1-6) and CoCl₂L (7-9), with 2,9-diaryl-1,10-phenanthroline ligands (L¹-L³) have been synthesized and characterized by elemental analysis, UV-Vis, IR spectroscopy, and X-ray crystal structural study (for 1, 4-7, 9). The solid-state structures of 1, 5-7 and 9 show four-coordinate, slightly flattened tetrahedral geometry at the Ni(II) or Co(II) center, while 4 is five-coordinated (square-pyramidal), containing a THF molecule as an auxiliary ligand. The title complexes (1-9) display good catalytic activities in ethylene oligomerization when activated with methylaluminoxane (MAO). While the Co(II) precatalysts produce primarily C₄ isomers, the Ni(II) complexes give ethylene dimers and trimers at normal pressure. The activities and yields of linear α-olefins increase with increasing ethylene pressure for the Ni(II) complexes, leading to more high-molar-mass products (C₈-C₁₈). Complex 6 displays the best catalytic activity among the complexes studied (up to 1518 kg/mol[Ni] h at 10 atm).     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

New insight in coordination of vic-dioximes: Bis- and tris(E,E-dioximato)Ni(II) complexes

N,N′-Bis[allylamino]glyoxime, N,N′-bis[anilino]glyoxime, and N,N′-bis[1,2,3,4-tetrahydro-5-naphthalenamino]glyoxime have been prepared from corresponding amines and (E,E)-dichloroglyoxime. These ligands gave orange-red compound with NiCl₂ in less acidic medium (pH ∼ 5) that are bis(E,E-dioximato)nickel(II) complexes {[(E,E)-Ni(HL)₂]} (1a-3a) and green compounds in acidic medium (pH ∼ 2) that are tris(E,E-dioximato)nickel(II) dichloride complexes {[(E,E)-Ni(LH₂)₃]Cl₂} (1b-3b). The crystal structures of all complexes have been determined by X-ray diffraction on a single crystal. The study of absorption spectra of these two types of complexes shows that they may be converted to each other by addition of acids (1a-3a) or bases (1b-3b) and there is no way for the amphi form.