Dianionic Tridentate Research Articles

Molecular Routes to Two-Dimensional Metal Dichalcogenides MX2 (M = Mo, W; X = S, Se).

New synthetic access to two-dimensional transition metal dichalcogenides (TMDCs) is highly desired to exploit their extraordinary semiconducting and optoelectronic properties for practical applications. We introduce here an entirely novel class of molecular precursors, [MIV(XEtN(Me)EtX)2] (MIV = MoIV, WIV, X = S, Se), enabling chemical vapor deposition of TMDC thin films. Molybdenum and tungsten complexes of dianionic tridentate pincer-type ligands (HXEt)2NR (R = methyl, tert-butyl, phenyl) produced air-stable monomeric dichalcogenide complexes, [W(SEtN(Me)EtS)2] and [Mo(SEtN(Me)EtS)2], displaying W and Mo centers in an octahedral environment of 4 S and 2 N donor atoms. Owing to their remarkable volatility and clean thermal decomposition, both Mo and W complexes, when used in the chemical vapor deposition (CVD) process, produced crystalline MoS2 and WS2 thin films. X-ray diffraction analysis and atomic-scale imaging confirmed the phase purity and 2D structural characteristics of MoS2 and WS2 films. The new set of ligands presented in this work open ups convenient access to a scalable and precursor-based synthesis of 2D transition metal dichalcogenides.

Cytotoxic homoleptic Ti(iv) compounds of ONO-type ligands: synthesis, structures and anti-cancer activity.

Eight Ti(iv) compounds 1-8, of the type [Ti(Ln)2] where Ln is a variously substituted dianionic tridentate acylhydrazone, were synthesized by reacting the appropriate hydrazide with 2-hydroxybenzaldehyde or 2'-hydroxyacetophenone and titanium(iv) tetra(isopropoxide) in a 2 : 2 : 1 molar ratio. The solid-state structures of 1-6 and 7·CH2Cl2 were deduced from the single crystal X-ray diffraction data, which indicated that each L2- ligand is fully deprotonated and coordinated to the Ti(iv) cation via the enolic oxygen, the imino nitrogen and the phenolic oxygen atoms (ONO donor set) in an enol tautomeric form, the metal assuming the distorted octahedral geometry. The structures of pro-ligands H2L3 and H2L5 are also reported. All complexes displayed high hydrolytic stability. In vitro cytotoxicity assays towards human ovarian A2780 and colon HT-29 cancer cell lines revealed the activity dependence on the acylhydrazone substituents, with electron-donating groups on the phenolato units enhancing the solubility and promoting cytotoxicity. The lead compound 5 of this study presents IC50 values of 2.5 ± 0.2 and 4.2 ± 0.6 μM for ovarian A2780 and colon HT-29 human cancer cells, respectively.

The mononuclear MoO2 2+ complexes with stereochemically rigid 4-aminobenzhydrazide based ligands

A range of dioxidomolybdenum(VI) complexes has displayed very high catalytic activities and exquisite selectivity. The dioxidomolybdenum(VI) mononuclear complexes with 4-aminobenzoylhydrazone ligands (salicylaldehyde (H2L1), 3- methoxysalicylaldehyde (H2L2), or 4- methoxysalicylaldehyde 4-aminobenzoylhydrazone (H2L3) being of the type cis-[MoO2L1-3(D)] ; D = MeOH, EtOH, H2O, dmf] have been prepared and structurally characterized. The crystal structure analysis of mononuclear complexes (Fig.1.) reveals distorted octahedral Mo(VI) coordination by ONO donor atoms from dianionic tridentate 4- aminobenzoylhydrazone ligands, two oxido oxygen atoms from the MoO22+ moiety and the oxygen atom from coordinated alcohol molecules (D = MeOH, EtOH).The molybdenum oxido groups of the MoO22+ moiety show the expected mutual cis configuration and are located trans to the imine nitrogen atom and coordinated alcohol molecule. The bond distances range around Mo follows trend: Mo-Ot < Mo-O(phenolate) < Mo- O(hydrazone part) < Mo-N< MoO(ROH ; R=Me, Et). The bicyclic system of two chelate rings is slightly folded along the axis of molybdenum- imino bond and by the offset of metal centre apart from chelate planes towards the terminal oxygen atom. The most deviation from chelate rings coplanarity is shown by the phenolate oxygen atom due to its participation in intermolecular interactions. The complexes were tested for catalytic epoxidation of cyclooctene under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide (TBHP) as an oxidant. Due to trans effect of oxido oxygen atom, Mo-O(D) bond is the longest bond distance within molybdenum coordination sphere and it expected to be the point of maximum catalytic reactivity of the complexes. It is previously shown that pentacoordinated molybdenum systems activate oxidizing agent TBHP through adduct formation assisted by the O–H…O hydrogen bond. Another explanation of the substituent influence is p-π conjunctive effect with methoxy group due to increasing electron density of the phenyl ring.

Synthesis and crystal structures of new sodium phenolate compounds: coordination chemistry

Four new sodium complexes of phenolate and bisphenolate ligands have been synthesized and characterized by NMR spectroscopy and X-ray crystallography to study their coordination chemistry. The monoanionic tridentate [ONN] phenolate ligand gave a dimeric compound [Na2L2] (2), which crystallized in the orthorhombic crystal system, where the sodium ions have four coordination environments. The dianionic tridentate [ONO] phenolate ligand gave a dimeric [Na2(LIH)2] (4) compound in the tetragonal crystal system. The sodium ions Na(1) and Na(1ʹ) are four-coordinate both having a tetrahedral geometry with the O–Na–O angle being ca. 93°, the O^N^O ligand string comprising a tridentate ligand. Interestingly, despite the steric bulk of N(SiMe3)2, a mixture of compounds [NaL] (2) and NaN(SiMe3)2 was isolated as a dimeric structure [Na2L(N(SiMe3)2)]2 (5) crystallized in the monoclinic crystal system. Na(1) is four-coordinate bonding to the phenolic oxygen atom and two N atoms of the ligand L and the N of the N(SiMe3)2 ligand. The coordination around Na(1) is tetrahedrally distorted square planar with the ‘cis’ angles ranging from 75.11(4) to 117.40(5)° and the ‘trans’ angles being 140.87(4) and 154.82(5)°. Na(2) is three-coordinate, bonding to the two phenolate oxygen atoms and the N atom of the N(SiMe3)2 ligand. Na(2), however, is not coplanar with these atoms being displaced 0.42 Å from it. The coordination chemistry for 5 is very intriguing as the sodium ions have mixed four- and three-coordination numbers, probably due to the steric hindrance of the silylamide groups.

Cyclometalated ruthenium(II) carbonyl complexes containing 2-(biphenylazo)phenolate ligands: Synthesis, structure, DFT study and catalytic activity towards oxidation and transfer hydrogenation

Abstract 2-(Biphenylazo)phenol ligands with various functional groups at the para-position of the phenol moiety (R = CH3, H2L1; R = OCH3, H2L2; R = (CH3)3C, H2L3; R = Cl, H2L4) readily undergo, upon reaction with [RuHCl(CO)(EPh3)3] (E = P, As) in toluene, cyclometalation via a C H bond activation at the ortho-position to afford complexes of general formula [Ru(L)(CO)(EPh3)2] (E = P, L = L1, 1; E = P, L = L2, 2; E = P, L = L3, 3; E = P, L = L4, 4; E = As, L = L1, 5; E = As, L = L2, 6; E = As, L = L3, 7; E = As, L = L4, 8). The molecular structure of five complexes has been determined by single-crystal X-ray structure analysis. In each complexes, the 2-(biphenylazo)phenol ligand is coordinated to the metal center as a di-anionic tridentate CNO-ligand with two triphenylphosphine/triphenylarsine in the axial positions along with one carbonyl group in the plane of the CNO- ligand. These new cyclometalated 2-(biphenylazo)phenolate complexes show intense absorption in the visible and ultraviolet regions and the nature of these transitions has been analyzed by TD-DFT calculations. The redox behavior of the complexes was also studied by cyclic voltammetry, revealing an irreversible reduction of the metallic center. The cyclometalated ruthenium(II) complexes were used as catalysts for oxidation and transfer hydrogenation reactions and they were found to be active catalysts.

Titanium complexes containing tridentate [ONO] type Schiff base ligands for the cycloaddition reaction of CO2 to propylene oxide

New titanium complexes, TiLCl2(THF) and TiL2, containing the tridentate chiral Schiff-base ligand, L, prepared from the condensation reaction of 2,4-pentadione and (1R,2S)-(−)-1-aminoindanol, were synthesized and characterized by various analytical methods including X-ray crystallography. Ligand L acted as a dianionic tridentate ligand and, owing to a chiral center in the aminoindanol part, imparted chirality to its titanium complexes. The newly synthesized titanium complexes and previously reported analogous Ti complexes were used as catalysts in the cycloaddition of CO2 to propylene oxide as the first representatives of titanium complexes with tridentate Schiff base ligands to have been used for this purpose. These complexes provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activities with TOF values up to 131 h−1 in comparison with the previously reported catalyst systems.

Synthesis, characterization and single crystal structures of chiral Schiff base and its tetranuclear palladium complex with Pd[sbnd]O[sbnd]Pd bridging and Pd[sbnd]Pd bonds

A new chiral Schiff base ligand 2-{N-[(2S)-(1-hydroxy-3-phenylpropan-2-yl]ethanimidoyl} phenol ((S)H2L) was obtained by acid catalyzed condensation of (2S)-(−)-2-amino-3-phenyl-1-propanol with 2′-hydroxyacetophenone. The palladium complex was prepared by treating a solution of (S)H2L in acetone with a solution of Na2PdCl4 in water in 1:1 M ratio. The new ligand and its complex were characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy, polarimetry and elemental analysis and their molecular structures were determined by single crystal X-ray diffraction. Both the compounds crystallizes in monoclinic system in the space group P21. There exists an intra [OH⋯N (1.62(5) Å)] and intermolecular [OH⋯O (1.53(5) Å) and CH⋯O (2.59 Å)] hydrogen bonding and secondary interactions in the crystal of (S)H2L. The structure of the palladium complex was found very interesting wherein the ligand coordinated to metal center as tridentate dianionic (O−, N, O−) fashion, (S)-L, resulting in a tetranuclear palladium cluster, [Pd4((S)-L)4]. In these supramolecular structures phenolate oxygen coordinated to Pd(II) ion as PdO terminal bonds [1.934(12) - 1.977(11) Å] and the alkoxide oxygen coordinated as PdOPd bridging bonds [1.993(11) - 2.012(12) Å]. The PdN bond lengths found were in the range of 1.949(13) to 1.919(12) Å. There exists two asymmetric tetranuclear complex molecules in its crystal lattice. There exists very strong metal-metal bond interaction, Pd(2)Pd(3) [3.0410(18) Å] and Pd(6)Pd(7) [3.0517(19) Å] respectively in the two asymmetric units.

Electrocatalytic Water Oxidation by a Water-Soluble Copper(II) Complex with a Copper-Bound Carbonate Group Acting as a Potential Proton Shuttle.

Water-soluble copper(II) complexes of the dianionic tridentate pincer ligand N,N'-2,6-dimethylphenyl-2,6-pyridinedicarboxamidate (L) are catalysts for water oxidation. In [L-CuII-DMF] (1, DMF = dimethylformamide) and [L-CuII-OAc]- (2, OAc = acetate), ligand L binds CuII through three N atoms, which define an equatorial plane. The fourth coordination site of the equatorial plane is occupied by DMF in 1 and by OAc- in 2. These two complexes can electrocatalyze water oxidation to evolve O2 in 0.1 M pH 10 carbonate buffer. Spectroscopic, titration, and crystallographic studies show that both 1 and 2 undergo ligand exchange when they are dissolved in carbonate buffer to give [L-CuII-CO3H]- (3). Complex 3 has a similar structure as those of 1 and 2 except for having a carbonate group at the fourth equatorial position. A catalytic cycle for water oxidation by 3 is proposed based on experimental and theoretical results. The two-electron oxidized form of 3 is the catalytically active species for water oxidation. Importantly, for these two oxidation events, the calculated potential values of Ep,a = 1.01 and 1.59 V vs normal hydrogen electrode (NHE) agree well with the experimental values of Ep,a = 0.93 and 1.51 V vs NHE in pH 10 carbonate buffer. The potential difference between the two oxidation events is 0.58 V for both experimental and calculated results. With computational evidence, this Cu-bound carbonate group may act as a proton shuttle to remove protons for water activation, a key role resembling intramolecular bases as reported previously.

Rare‐Earth Complexes Coordinated by ansa‐Bis(amidinate) Ligands with m‐Phenylene, 2,6‐Pyridinediyl, and SiMe2 Linkers

The salt‐metathesis reactions of anhydrous LnCl3 (Ln = Y, Er) with [1,3‐C6H4{NC(Ph)NSiMe3}2Li2(thf)2]2 (1; thf = tetrahydrofuran) in a 2:1 molar ratio in thf afford tris(amidinate) complexes [(1,3‐C6H4{NC(Ph)NSiMe3}2)3Y(thf)Y(µ‐Cl)Li(thf)3] (3) and [(1,3‐C6H4{NC(Ph)NSiMe3}2)3Er2(µ‐Cl)Li(thf)3] (4), which feature bridging coordination of the amidinate ligands to two Ln3+ ions. The reactions of the dilithium derivative of the related bis(amidine) with a 2,6‐pyridinediyl linker, [2,6‐C5H3N{NC(tBu)N(2,6‐Me2C6H3)}2]2–, with LnCl3 (Ln = Y, Er) result in the formation of mononuclear chlorido bis(ligand) ate complexes [{(2,6‐C5H3N)(NC{tBu}N{2,6‐Me2C6H3})2}({2,6‐C5H3N}{NC(tBu)N(2,6‐Me2C6H3)}{NC(tBu)NH(2,6‐Me2C6H3)})LnCl][Li(dme)3] [Ln = Y (5), Er (6); dme = 1,2‐dimethoxyethane]. The Ln3+ ions in these complexes are coordinated by one dianionic tridentate amidopyridinate–amidinate ligand, and the second ligand is a monoanionic amidopyridinate. The reaction of YbCl3 with [(Me2Si{NC(Ph)N(2,6‐iPr2C6H3)}2)2Li3][Li(thf)4], which contains a short SiMe2 linker, in a 2:1 molar ratio in thf afforded the bis(amidinate)chloridoytterbium complex [(Me2Si{NC(Ph)N(2,6‐iPr2C6H3)}2)2(Yb2Cl)(µ‐Cl)2Li(thf)3] (8). The magnetic properties of 4 were investigated through superconducting quantum interference device (SQUID) magnetometry.

Ru(III) mediated C[sbnd]H bond activation of N-(naphthyl)salicylaldimine and related Schiff base ligands: Synthesis, structure, DFT study and catalytic activity

New family of cyclometalated ruthenium(III) Schiff base complexes of the general composition [Ru(LON)(LCNO)(EPh3)] (L=Schiff base ligands of CNO- and ON-donors; E=P, As) have been synthesized and characterized by elemental analysis, FT–IR, UV–Vis and EPR spectral methods. The molecular structure of one of the complexes [Ru(LON)(LCNO)(PPh3)] (5) was determined by X-ray crystallography. The Schiff base ligands readily undergo cyclometalation with the ruthenium metal precursor by CH activation at the peri-position. These Schiff base ligands coordinated to metal center as di-anionic tridentate CNO-donor and bi-dentate ON-donor in these cycloruthenium complexes. TD–DFT calculations were also carried out for the complex (5). The catalytic activity of the complex [Ru(LON)(LCNO)(PPh3)] (5) was performed and found to be an efficient catalyst for the transfer hydrogenation of ketones with excellent conversion in the presence of i-PrOH/KOH at 80°C in 2h.

Influence of the monodentate ancillary ligand on the photophysical properties of Pt(II) complexes bearing a symmetric dianionic tridentate luminophore

Abstract Herein we present a study of the influence of the ancillary ligand on the photophysical properties of Pt(II) complexes with a symmetric tridentate luminophore. Starting from a previously used bulky triphenylphosphane (PPh3) as the monodentate ancillary ligand, progressively smaller ancillary ligands were introduced, namely a PPh2Me and a PPhMe2 and finally compared with a planar 4-amylpyridine. We observed that the emission wavelength of the monomer was not influenced by the monodentate ligand, and that excimer formation only occurs for the fully planar complex. Surprisingly, intermolecular deactivation pathways can be largely suppressed even with the smallest phosphane. This knowledge is important for the design and realization of triplet emitters for optoelectronic devices.

New pillared dioxomolybdenum(VI) complexes with ONS donor ligands and 4,4′-azopyridine spacer: 3D metal-organic supramolecular architectures and DFT calculations

Two new pillared binuclear dioxomolybdenum(VI) complexes [(MoO2L1)2(4,4′-azpy)] (1) and [(MoO2L2)2(4,4′-azpy)] (2) have been synthesized by the reaction of MoO2(acac)2 with Schiff base ligands (H2L1 and H2L2) derived from 2-hydroxyacetophenone and S-benzyl/S-methyl dithiocarbazates respectively and 4,4′-azopyridine as a spacer. Crystal and molecular structures of the investigated binuclear complexes 1 and 2 were determined by single crystal X-ray diffraction. The two complexes have similar centrosymmetric dimeric structures in which each molybdenum atom occupies distorted octahedral six-coordinate environments being bonded to a dianionic tridentate ONS donor ligand via phenolate oxygen, imine nitrogen and thioenolate structure as well as two terminal oxygen atoms and a nitrogen atom of the bridging 4,4′-azpy ligand. Complexes 1 and 2 give rise to 3D metal-organic supramolecular frameworks having rectangular cavities formed via hydrogen bonding and π-π stacking interactions. The complexes were further characterized by elemental analysis, spectroscopic methods (IR, 1H NMR and UV–vis), electrochemical study and thermogravimetric analysis. DFT calculations were used to study the electronic properties of the complexes.

Nickel(II) Schiff base complexes: Synthesis, characterization and catalytic activity in Kumada–Corriu cross-coupling reactions

The syntheses of ten new Ni(II) complexes 5a–5j with H2L tridentate (ONO) Schiff-base ligand (2-((2-oxybenzylidene)amino)phenolate) have been described and fully characterized by means of elemental analysis, FT–IR, electronic, 1H NMR and 13C NMR spectroscopy and single-crystal X-ray diffraction. In all [Ni(L)B] complexes (where B are imidazole, 4-benzylpyridine, 2-methyl-5-ethylpyridine, 3-hydroxymethylpyridine, 2-methylbenzimidazole, 2,6-dimethylpyridine, 4-methylpyridine, 2-isopropylbenzimidazole, 4-methylpiperidine or triphenylphosphine) the Schiff base completely deprotonates and coordinates to the metal ion as a dianionic tridentate ligand via the donor oxygens and nitrogen atoms. The coordination number of Ni(II) atoms is four with distorted square-planar stereochemistry. This is in a good agreement with the ligand field band position in their electronic spectra, as well as with the X-ray structure analysis for all complexes under study. Six selected complexes are used as catalysts for Kumada–Corriu cross-coupling reactions and exhibit a moderate to good catalytic activity in the synthesis of biaryl derivatives.

Bis-Tridentate Iridium(III) Phosphors Bearing Functional 2-Phenyl-6-(imidazol-2-ylidene)pyridine and 2-(Pyrazol-3-yl)-6-phenylpyridine Chelates for Efficient OLEDs

Proligands to the monoanionic tridentate chelate 4-(tert-butyl)-2-(2,4-difluorophenyl)-6-(3-isopropyl-imidazol-2-ylidene)pyridine ((phpyim-H2)PF6) and dianionic tridentate chelates derived from functional 2-pyrazol-3-yl-6-phenylpyridine chelates, i.e. L1-H2–L5-H2, have been synthesized and characterized. Treatment of (phpyim-H2)PF6 with [Ir(COD)(μ-Cl)]2 in the presence of sodium acetate, followed by heating at 200 °C with 1 equiv of the dianionic chelate, afforded the respective charge-neutral, bis-tridentate Ir(III) complexes [Ir(phpyim)(Ln)] (1–5; n = 1–5). The hydride complex [Ir(phpyim)(L5-H)(H)] (6) was made when the “one-pot” reaction of (phpyim-H2)PF6, [Ir(COD)(μ-Cl)]2, and L5-H2 was carried out at 140 °C. Complex 6 is likely an intermediate in the formation of 5, as it is converted to 5 on heating to 200 °C. Compounds 1–6 have been characterized by NMR spectroscopy and, in the cases of 1, 5, and 6, by X-ray structural analysis. TD-DFT computations confirmed that the emission bands are derived from...

Monoorgano-gallium and –indium complexes derived from dianionic tridentate ONO Schiff bases: Synthesis, crystal structures and photoluminescence

Reactions of triorgano-gallium and –indium etherates with N′-(2-hydroxybenzylidine)benzohydrazide and N′-(2-hydroxy-3-methoxybenzylidine)benzohydrazide in refluxing benzene afforded complexes of composition [{RM}{–O(C6H3R′-3)CHN–NC(C6H5)O–}] (MGa, In; RMe, Et; R′H, OMe). These complexes have been characterized by elemental analysis, IR, UV-vis, and NMR (1H and 13C{1H}) spectroscopy. The molecular structures of [{MeGa}{–O(C6H4)CHN–NC(C6H5)O–}]2 (1), [{MeGa}{–O(C6H3–OMe)CHN–NC(C6H5)O–}]2 (2) and [{EtGa}{–O(C6H3–OMe)CHN–NC(C6H5)O–}]2 (6) were established by X-ray crystallography. These complexes adopt a dimeric structure with phenolate oxygen bridges with the gallium atom acquiring a distorted square pyramidal configuration. These complexes are emissive in toluene solution at room temperature.

Aluminium, gallium and indium complexes supported by a chiral phenolato-prolinolato dianionic ligand

AbstractCongeneric complexes (

Synthesis, characterization, structure and catalytic activity of (NNN) tridentate azo-imine nickel(II), palladium(II) and platinum(II) complexes

The newly designed tridentate ligand, 2,2′-(bisdiamino)azobenzene, H2L, 1 derived from the oxidative coupling of o-phenylenediamine in presence of NaOH base, upon reaction with Ni(II), Pd(II) and Pt(II) separately in methanol yielded [(HL)Ni(PPh3)]ClO4, 2, [(HL)Pd(PPh3)]ClO4, 3 and [(L)Pt(PPh3)], 4 which were characterized by spectral data and authenticated by single crystal X-ray diffraction of 1–4. The diffraction analysis revealed that the ligand binds the metals (Ni(II), Pd(II)) in monoanionic and Pt(II) in dianionic tridentate (N,N,N) fashion offering distorted square planar geometry where fourth position is occupied by one PPh3 group. One ClO4− ion satisfies the charge of the former aggregate [(HL)Ni(PPh3)]+ and [(HL)Pd(PPh3)]+. Suzuki and Heck coupling reactions were carried out, in presence of air and moisture, using [(HL)Pd(PPh3)]ClO4, 3 as catalysts for a variety of substrates.

Pyridylamido Bi-Hafnium Olefin Polymerization Catalysis: Conformationally Supported Hf···Hf Enchainment Cooperativity

Homobimetallic Hf(IV) complexes, L2-Hf2Me5 (3) and L2-Hf2Me4 (4) (L2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)methylene)]bis(2,6-diisopropylaniline}), were synthesized by reaction of the free ligand L2 with the appropriate Hf precursor and were characterized in solution (NMR) and in the solid state (X-ray diffraction). In 3, L2 acts as a dianionic tridentate ligand for one Hf metal center and as a monoanionic bidentate ligand for the other, whereas in 4, both Hf units are tricoordinated to opposite sides of L2. In the solid state, the Hf···Hf distance is significantly different in 3 vs 4 (6.16 vs 8.06 A, respectively), but in solution, the structural dynamics of the two linked metallic units in bis-activated complex 3 accesses conformers with far closer Hf···Hf distances (∼3.2 A). Once activated with Ph3C+B(C6F5)4– (B1) or PhNMe2H+B(C6F5)4– (NB), 3 exhibits pronounced bimetallic cooperative effects in ethylene homopolymerization and ethylene +1-octene copolymerization vs ...

Synthesis and molecular structure of ruthenium(III) benzoylhydrazone complexes: Substituents effect on transfer hydrogenation of ketones

An easy and convenient synthesis of a new series of octahedral ruthenium(III) complexes bearing benzoylhydrazone of general formula [Ru(L)Cl(PPh3)2] (where L = 2-hydroxy-1-naphthaldehyde benzoylhydrazone) has been reported. The composition of all the complexes has been unequivocally characterized by microanalysis, IR, electronic, magnetic and EPR spectroscopic techniques. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors and coordinate to ruthenium via the phenolic oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The complexes exhibit moderately strong ligand-to-metal charge transfer transitions in the visible region and intraligand transition in the UV region. Magnetic moment of the complexes (298 K) lies in the range 1.72–1.97 μB reveals the presence of one unpaired electron in the metal centre. The low spin mononuclear Ru(III) benzoylhydrazone complexes display rhombic EPR spectral pattern in frozen solution. The molecular structure of two of the complexes has been established by single crystal X-ray crystallography and indicates the presence of a distorted octahedral geometry in these complexes. Further, the complexes 1–5 have been proven to catalyse the transfer hydrogenation of linear, cyclic and aromatic ketones to their corresponding secondary alcohols in the presence of i-PrOH/KOH at 82 °C and the maximum conversion is up to 99%. The effect of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time and catalyst loading is also reported.

A study on the effect of dianionic tridentate ligands on the radiative and nonradiative processes for gold(III) alkynyl systems by a computational approach.

Gold(III) alkynyl complexes with dianionic tridentate pincer ligands have received growing attention recently because of their rich luminescence behavior and their potential applications in areas such as optoelectronics and sensors. In this study, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed to investigate the radiative and nonradiative processes for the gold(III) alkynyl complexes with different dianionic tridentate ligands, [Au(C^N^C)(C≡CC6H5)] (1; C^N^C = 2,6-diphenylpyridine), [Au(C(Np)^N^C(Np))(C≡CC6H5)] [2; C(Np)^N^C(Np) = 2,6-di(2-naphthyl)pyridine], [Au(N^N^N)(C≡CC6H5)] [3; N^N^N = 2,6-bis(benzimidazol-2'-yl)pyridine], and [Au(C^C^N)(C≡CC6H5)] [4; C^C^N = 3-(2-pyridyl)biphenyl]. It has been found that the electronic properties of the tridentate ligand could have a significant impact on the radiative and nonradiative processes. This study provides an in-depth understanding on the effect of the dianionic pincer ligands on the different photophysical behaviors among the gold(III) alkynyl complexes and crucial information for the future design of gold(III) complexes in various applications.