CuII Complexes Research Articles

Oxygen Transfer from Trimethylamine N‐Oxide to CuI Complexes Supported by Pentanitrogen Ligands

[N,N‐bis(1‐methyl‐2‐benzimidazolyl)methyl‐N‐(bis‐2‐pyridylmethyl)amine] (L1) and [N,N‐bis(2‐quinolylmethyl)‐N‐bis(2‐pyridyl)methylamine] (L2) were employed to prepare CuII and CuI complexes for spectroscopic and structural characterization. [L1CuII(H2O)](NO3)2 and [L2CuII(NO3)]NO3 have Jahn–Teller distorted octahedral geometries and give rise to isotropic EPR spectra in frozen solution. [L1CuI(CH3CN)]OTf and [L2CuI(CH3CN)]OTf have distorted trigonal bipyramidal and tetrahedral solid‐state structures, respectively. The N‐donors display labile behavior in solution, based on variable‐temperature 1H NMR studies. Addition of trimethylamine N‐oxide (Me3NO) to solutions of [L1CuI(CH3CN)]OTf and [L2CuI(CH3CN)]OTf resulted in diamagnetic species tentatively assigned as the corresponding adducts upon replacement of coordinated acetonitrile, based on 1H NMR spectroscopy. Heating [L1CuI(CH3CN)]OTf to 50–60 °C in the presence of Me3NO resulted in its cupric analogue [L1CuII(CH3CN)]2+, as well as a small amount of 2‐dipyridylketone, along with other oxidation by‐products. In the case of [L2CuI(CH3CN)]OTf, the reaction with Me3NO resulted in the cupric complex bis(2‐quinolinecarboxamidato)copper(II), along with 2‐dipyridylketone as oxidation products.

Mechanism Change of (+)-Nonlinear Effect in a Phase Separation System in a CuII-Catalyzed Asymmetric Friedel-Crafts Reaction Using a C2-Chiral Dioxolane-Containing-Bisamidine Ligand, Naph-diPIM-dioxo-iPr

Abstract A CuII complex of bisamidine ligand LS, chirally modified naphtho[1,2-b:7,8-b′]dipyrroloimidazole (Naph-diPIM), catalyzes the enantioselective Friedel-Crafts (FC) reaction of indole (1a) with ethyl trifluoropyruvate (2) to give quantitatively the FC adduct 3a with a 98:2 S/R enantiomer ratio (er). The reaction shows no nonlinear effect (NLE) under the standard conditions of [1a] = [2] = 100 mM; [Cu(OTf)2] = [LS + LR] = 0.10 mM; CPME; and 0 °C irrespective of the catalyst aging temperature. A five-fold increase in the catalyst concentration (0.50 mM) changes the situation, leading to a strong (+)-NLE with phase separation of a white solid. The NLE is expressed by the Noyori-type mechanism: Aggregate of heterochiral dimer CuLSCuLR is separated from the reaction system (Khetero > 1 > Khomo). Furthermore, a strong (+)-NLE is observed via a purple solid liberation even with [CuII] = 0.10 mM after the catalyst aging at 100 °C in the presence of an excess amount of chiral ligand. A mechanistic study has revealed i) that the sterically disfavored homochiral 1:2 complex CuLSLS is more stabilized by an intramolecular n-π* interaction than the sterically favored heterochiral 1:2 complex CuLSLR and ii) that the (+)-NLE originates from the phase separation of heterochirally interacted (CuLSLSCuLRLR).

Template Synthesis, Characterization, Antioxidant Effects, DNA Cleavage and Antimicrobial Studies of ZnII, NiII, MnII, CuII and CoII Complexes Containing Pyridazinone Moiety

Bu çalışmada template metodu ile o-aminofenol, 5-benzoil-4-hidroksi-2-metil-6-fenil-2Hpiridazin-3-on ve ZnII, NiII, MnII, CuII ve CoII metal tuzlarından türeyen beş yeni Schiff baz kompleksi sentezlenmiştir. Metal kompleksler elemental analiz, FT-IR, UV-Vis, kütle ve manyetik duyarlılık ile karakterize edilmiştir. Sentezlenen bileşiklerin antioksidan etkileri, DNA bölünmesi ve antimikrobiyal çalışmaları yapılmıştır. DPPH süpürme ve metal şelatlama aktivitesinin konsantrasyona bağlı olarak arttığı bulunmuştur. En yüksek DPPH aktivitesi ve demir iyon şelatlama aktivitesi Zn bileşiğinden elde edildi. Sentezlenen tüm bileşikler, Mn>Zn=Ni=Co>Cu sırasına gore E. hirae’ye karşı antibakteriyal aktivite sergilerken, sadece Ni bileşiği test edilen tüm organizmalara karşı, özellikle de L. pneumophila subsp. pneumophila’ya 13 mm’ye eşit inhibisyon zon değerinde antimikrobiyal aktivite göstermiştir.

Spectroscopy driven DFT computation for a structure of the monomeric Cu2+-Curcumin complex and thermodynamics driven evaluation of its binding to DNA: Pseudo-binding of Curcumin to DNA

In an attempt to overcome limitations of Curcumin from being an important molecule in biology and medicine, a monomeric complex of CuII [Cu(Cur)(OCOCH3)(H2O)] was prepared. Physico-chemical studies in solution using copper acetate and Curcumin indicate formation of a 1:2 CuII:Curcumin species. However, attempts to prepare it always led to the formation of a 1:1 CuII:Curcumin species, if CuII-acetate was used as the starting material. In the absence of a single crystal or an appropriate powder X ray diffraction data that would allow solving of the structure, it was arrived at by spectroscopy guided DFT calculations. Unlike Curcumin, the prepared complex was stable under physiological conditions, an advance achieved through complex formation. Effective binding of the complex to DNA with an ability to enhance cellular uptake owing to the presence of CuII are other benefits of complex formation that might increase its cytotoxic potential. The complex has a reasonably strong affinity for DNA realized from binding constant values obtained with calf thymus DNA at different temperatures in the range 25 °C–35 °C. This enabled an evaluation of thermodynamic parameters (ΔH, ΔS and ΔG), that helped in determining the mode of binding between the complex and DNA as realized from a correlation of thermodynamic signatures to binding types. The study may be considered a case of pseudo-binding of Curcumin to DNA since the complex containing a Curcumin bound the metal ion does not dissociate in solution under physiological conditions, i.e. remains as one unit. Hence binding of the complex to DNA is also the binding of Curcumin to it present as one “single unit”, a major advancement based on a biophysical approach. Besides, aspects like stability of the complex in solution, prevention of degradation of Curcumin in aqueous buffer or biological milieu, binding with mammalian DNA are other aspects that are significant for use of the complex on biological targets.

Heterotrimetallic Cyanide-Bridged 3d-4d-5d Frameworks Based on a Photomagnetic Secondary Building Unit.

The rational design of coordination frameworks combining more than two different metal ions using a self-assembly approach is challenging because it rarely offers sufficient control over the building blocks at the actual self-assembly stage. In this work, we present a successful two-step strategy toward heterotrimetallic coordination frameworks by employing a new bimetallic [(NC)7MoIV-CN-PtIV(NH3)4-NC-MoIV(CN)7]4– secondary building unit (SBU). This anionic moiety has been isolated and characterized as a simple salt with an organic dppipH22+ cation (dppipH2)2[(NC)7MoIV-CN-PtIV(NH3)4-NC-MoIV(CN)7]·15H2O (1) (dppip = 1,4-di(4-pyridinyl)piperazine). The salt presents a second-order phase transition related to cation conformational change around 250 K and a photomagnetic effect after irradiation with 450 nm light at 10 K. When combined with aqueous solutions of MnII or CuII complexes, it forms either a one-dimensional chain [MnII(dpop)][MnII(dpop)(H2O)][(NC)7MoIV-CN-PtIV(NH3)4-NC-MoIV(CN)7]·36H2O (2) (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) or a photomagnetic two-dimensional honeycomb network [CuII(cyclam)]2[(NC)7MoIV-CN-PtIV(NH3)4-NC-MoIV(CN)7]·40.89H2O (3) (cyclam = 1,4,8,11-tetraazacyclotetradecane), both characterized by very large cavities in their structure filled with solvent molecules. Both 2 and 3 incorporate three different transition-metal ions and constitute a new family of 3d-4d-5d coordination frameworks. Moreover, compound 3 inherits the photomagnetic properties of the MoPtMo SBU.

Tracking the dissolution-recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic, mass spectrometric and DFT study.

Methanol- and temperature-induced dissolution-recrystallization structural transformation (DRST) was observed among two novel CuII complexes. This is first time that the combination of X-ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear CuII complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time-dependent high-resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8-methoxyquinoline-κ2N,O)bis(thiocyanato-κN)copper(II), [Cu(NCS)2(C10H9NO)2], Cu1, to di-μ-methanolato-κ4O:O-bis[(8-methoxyquinoline-κ2N,O)(thiocyanato-κN)copper(II)], [Cu2(CH3O)2(NCS)2(C10H9NO)2], Cu2, viz. [Cu(SCN)2(L)2] (Cu1) → [Cu(L)2] → [Cu(L)]/L → [Cu2(CH3O)2(NCS)2(L)2] (Cu2). We screened the antitumour activities of L (8-methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1.

Triple Self-Sorting in Constitutional Dynamic Networks: Parallel Generation of Imine-Based CuI , FeII , and ZnII Complexes.

Three imine‐based metal complexes, having no overlap in terms of their compositions, have been simultaneously generated from the self‐sorting of a constitutional dynamic library (CDL) containing three amines, three aldehydes, and three metal salts. The hierarchical ordering of the stability of the three metal complexes assembled and the leveraging of the antagonistic and agonistic relationships existing between the constituents within the constitutional dynamic network corresponding to the CDL were pivotal in achieving the sorting. Examination of the process by NMR spectroscopy showed that the self‐sorting of the FeII and ZnII complexes depended on an interplay between the thermodynamic driving forces and a kinetic trap involved in their assembly. These results also exemplify the concept of “simplexity”—the fact that the output of a self‐assembling system may be simplified by increasing its initial compositional complexity—as the two complexes could self‐sort only in the presence of the third pair of organic components, those of the CuI complex.

The reactions of the Cu(II)-nitrilotris(methylenephosphonic acid) complex with alkyl radicals in aqueous solutions

The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were studied. The kinetics of formation of the transient complexes (ntp)CuIII-R fit pseudo first order rate laws. The mechanism of decomposition of the transient complex (ntp)CuIII-CH3 at pH ≥ 7 involves homolysis of the CuIII-C bond. However, at pH < 6 the decomposition mechanisms of the transient complexes (ntp)CuIII-R involve inter-molecular electron transfer to CuII(ntp)(H2O) and slow intra-molecular electron transfer.

Strong Visible-Light-Absorbing Cuprous Sensitizers for Dramatically Boosting Photocatalysis.

Developing strong visible-light-absorbing (SVLA) earth-abundant photosensitizers (PSs) for significantly improving the utilization of solar energy is highly desirable, yet it remains a great challenge. Herein, we adopt a through-bond energy transfer (TBET) strategy by bridging boron dipyrromethene (Bodipy) and a CuI complex with an electronically conjugated bridge, resulting in the first SVLA CuI PSs (Cu-2 and Cu-3). Cu-3 has an extremely high molar extinction coefficient of 162 260 m-1 cm-1 at 518 nm, over 62 times higher than that of traditional CuI PS (Cu-1). The photooxidation activity of Cu-3 is much greater than that of Cu-1 and noble-metal PSs (Ru(bpy)3 2+ and Ir(ppy)3 + ) for both energy- and electron-transfer reactions. Femto- and nanosecond transient absorption and theoretical investigations demonstrate that a "ping-pong" energy-transfer process in Cu-3 involving a forward singlet TBET from Bodipy to the CuI complex and a backward triplet-triplet energy transfer greatly contribute to the long-lived and Bodipy-localized triplet excited state.

Strong Visible‐Light‐Absorbing Cuprous Sensitizers for Dramatically Boosting Photocatalysis

AbstractDeveloping strong visible‐light‐absorbing (SVLA) earth‐abundant photosensitizers (PSs) for significantly improving the utilization of solar energy is highly desirable, yet it remains a great challenge. Herein, we adopt a through‐bond energy transfer (TBET) strategy by bridging boron dipyrromethene (Bodipy) and a CuI complex with an electronically conjugated bridge, resulting in the first SVLA CuI PSs (Cu‐2 and Cu‐3). Cu‐3 has an extremely high molar extinction coefficient of 162 260 m−1 cm−1 at 518 nm, over 62 times higher than that of traditional CuI PS (Cu‐1). The photooxidation activity of Cu‐3 is much greater than that of Cu‐1 and noble‐metal PSs (Ru(bpy)32+ and Ir(ppy)3+) for both energy‐ and electron‐transfer reactions. Femto‐ and nanosecond transient absorption and theoretical investigations demonstrate that a “ping‐pong” energy‐transfer process in Cu‐3 involving a forward singlet TBET from Bodipy to the CuI complex and a backward triplet‐triplet energy transfer greatly contribute to the long‐lived and Bodipy‐localized triplet excited state.

Key Intermediate Species Reveal the Copper(II)-Exchange Pathway in Biorelevant ATCUN/NTS Complexes.

The amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards CuII ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped‐flow and microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate CuII complexes formed by glycyl–glycyl–histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two‐nitrogen coordination, t 1/2≈100 ms at pH 6.0 and the ability to maintain the CuII/CuI redox pair is the best candidate for the long‐sought reactive species in extracellular copper transport.

Key Intermediate Species Reveal the Copper(II)‐Exchange Pathway in Biorelevant ATCUN/NTS Complexes

AbstractThe amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards CuII ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped‐flow and microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate CuII complexes formed by glycyl–glycyl–histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two‐nitrogen coordination, t1/2≈100 ms at pH 6.0 and the ability to maintain the CuII/CuI redox pair is the best candidate for the long‐sought reactive species in extracellular copper transport.

Observation of field-induced single-ion magnet behavior in a mononuclear DyIII complex by co-crystallization of a square-planar CuII complex

Employing Cu(acac)2 to react with Dy(hfac)3(H2O)2 (where acac− = acetylacetonate and hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate), the first true 3d-4f metal-complex cocrystal with the composition of [Cu(acac)2·Dy(hfac)3(H2O)2] that only consists of reactants, was acquired and structurally characterized. Magnetic investigations revealed that the 4f coformer Dy(hfac)3(H2O)2 does not show slow magnetic relaxation behavior even under an applied dc field of 2000 Oe down to 1.9 K, while the obtained 3d-4f cocrystal displays evident slow magnetic relaxation behavior associated with single-ion magnet (SIM) characteristic under the same dc field. This phenomenon is further supported and elucidated by the results of theoretical calculations together with the analyses of their crystal structures. Thus our results first indicate that 3d-4f co-crystallization technique is a useful tool for improving the magnetic performance of lanthanide complexes.

Crystal structure and characterization of a new copper(II) chloride dimer with meth-yl(pyridin-2-yl-methyl-idene)amine.

The new copper(II) complex, namely, di-μ-chlorido-bis-{chlorido-[meth-yl(pyri-din-2-yl-methyl-idene)amine-κ2 N,N']copper(II)}, [Cu2Cl4(C7H8N2)2], (I), with the ligand 2-pyridyl-methyl-N-methyl-imine (L, a product of Schiff base condensation between methyl-amine and 2-pyridine-carbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the CuII ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitro-gen atoms from the bidentate chelate L [Cu-N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu-Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu⋯Cu separation in the dimer is 3.4346 (3) Å. In the crystal structure, the loosely packed dimers are arranged in stacks propagating along the a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear CuII complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E 1/2 = -0.037 V versus silver-silver chloride electrode (SSCE) assignable to the reduction peak of CuII/CuI in methanol as solvent.

Sterically Demanding AgI and CuI N-Heterocyclic Carbene Complexes: Synthesis, Structures, Steric Parameters, and Catalytic Activity.

The synthesis and full characterization of new air‐stable AgI and CuI complexes bearing structurally bulky expanded‐ring N‐heterocyclic carbene (erNHC) ligands is presented. The condensation of protonated NHC salts with Ag2O afforded a collection of AgI complexes, and their first use as ligand transfer reagents led to novel isostructural CuI or AuI complexes. In situ deprotonation of the NHC salts in the presence of a copper(I) source, provides a library of new CuI complexes. The solid‐state structures feature large N‐CNHC‐N angles (118–128°) and almost identical angles between the aryl groups on the nitrogen atoms and the plane of the N‐C‐N unit of the carbene (i.e. torsion angles close to 0°). Among the steric parameters, the percent buried volume (%V bur) values span easily in the 50–57 % range, and that one of (9‐Dipp)CuBr complex (%V bur=57.5) overcomes to other known erNHC–metal complexes reported to date. Preliminary catalytic experiments in the copper‐catalyzed coupling between N‐tosylhydrazone and phenylacetylene, afforded 76–93 % product at the 0.5–2.5 mol % catalyst loading, proving the stability of CuI erNHC complexes at elevated temperatures (100 °C).

Cyclic (Amino)(aryl)carbenes Enter the Field of Chromophore Ligands: Expanded π System Leads to Unusually Deep Red Emitting CuI Compounds.

A series of copper(I) complexes bearing a cyclic (amino)(aryl)carbene (CAArC) ligand with various complex geometries have been investigated in great detail with regard to their structural, electronic, and photophysical properties. Comparison of [CuX(CAArC)] (X = Br (1), Cbz (2), acac (3), Ph2acac (4), Cp (5), and Cp* (6)) with known CuI complexes bearing cyclic (amino)(alkyl), monoamido, or diamido carbenes (CAAC, MAC, or DAC, respectively) as chromophore ligands reveals that the expanded π-system of the CAArC leads to relatively low energy absorption maxima between 350 and 550 nm in THF with high absorption coefficients of 5-15 × 103 M-1 cm-1 for 1-6. Furthermore, 1-5 show intense deep red to near-IR emission involving their triplet excited states in the solid state and in PMMA films with λemmax = 621-784 nm. Linear [Cu(Cbz)(DippCAArC)] (2) has been found to be an exceptional deep red (λmax = 621 nm, ϕ = 0.32, τav = 366 ns) thermally activated delayed fluorescence (TADF) emitter with a radiative rate constant kr of ca. 9 × 105 s-1, exceeding those of commercially employed IrIII- or PtII-based emitters. Time-resolved transient absorption and fluorescence upconversion experiments complemented by quantum chemical calculations employing Kohn-Sham density functional theory and multireference configuration interaction methods as well as temperature-dependent steady-state and time-resolved luminescence studies provide a detailed picture of the excited-state dynamics of 2. To demonstrate the potential applicability of this new class of low-energy emitters in future photonic applications, such as nonclassical light sources for quantum communication or quantum cryptography, we have successfully conducted single-molecule photon-correlation experiments of 2, showing distinct antibunching as required for single-photon emitters.

Computational Clarification of Synergetic RuII/CuI-Metallaphotoredox Catalysis in C(sp3)–N Cross-Coupling Reactions of Alkyl Redox-Active Esters with Anilines

The C–N coupling of alkyl electrophiles for amine synthesis is a less-developed area in comparison with that of aryl electrophiles largely because of the difficulty in product-generating C(sp3)–N reductive elimination. The recent work by Hu et al. (Nat. Catal. 2018, 1, 120–126) developed an effective strategy for the C–N coupling of alkyl redox-active esters with anilines by merging photoredox catalysis and copper catalysis with an oxoacetic acid ligand (LH2). Here, we present a DFT-based computational study to understand how the special dual catalysis works in a cooperative fashion with the assistance of the ligand. Photoredox catalysis is found to occur most possibly through an oxidative quenching mechanism (RuII/*RuII/RuIII/RuII) with Et3N as the quencher rather than with the experimentally proposed copper complex. Copper catalytic cycle (CuI/CuII/CuIII/CuI) is predicted to proceed via a CuI-oxidation-first pathway instead of the hypothetical aniline-deprotonation-first pathway in the experiment, and the most likely catalytic active species is identified as the CuILH complex. With the RuII/CuI-metallaphotoredox catalysis, the most feasible mechanism for the C(sp3)–N cross-coupling involves six steps: (i) generation of cyclohexyl radical (Cy•) via the single electron transfer (SET) from photoexcited *RuII to the complex of redox-active ester with CuI, (ii) coordination of aniline to CuI center, (iii) Cy• radical addition to CuI center, (iv) SET between CuII-cyclohexyl aniline complex and generated Et3N•+, (v) deprotonation of aniline, and (vi) reductive elimination of the CuIII-cyclohexyl amido intermediate to produce the C(sp3)–N coupling product. The CuI complex is identified to play a dual role in the title reaction, which acts as the promoter in oxidative quenching process and as the catalyst in the copper catalytic cycle.

Phenanthrene‐Fused‐Quinoxaline as a Key Building Block for Highly Efficient and Stable Sensitizers in Copper‐Electrolyte‐Based Dye‐Sensitized Solar Cells

AbstractDye‐sensitized solar cells (DSSCs) based on CuII/I bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open‐circuit voltages (VOC, more than 1 V). However, their short‐circuit photocurrent density (JSC) has remained modest. Increasing the JSC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO2 film and fast regeneration by the CuI complex. Herein, we report two new D‐A‐π‐A‐featured sensitizers termed HY63 and HY64, which employ benzothiadiazole (BT) or phenanthrene‐fused‐quinoxaline (PFQ), respectively, as the auxiliary electron‐withdrawing acceptor moiety. Despite their very similar energy levels and absorption onsets, HY64‐based DSSCs outperform their HY63 counterparts, achieving a power conversion efficiency (PCE) of 12.5 %. PFQ is superior to BT in reducing charge recombination resulting in the near‐quantitative collection of photogenerated charge carriers.

Phenanthrene‐Fused‐Quinoxaline as a Key Building Block for Highly Efficient and Stable Sensitizers in Copper‐Electrolyte‐Based Dye‐Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) based on Cu(II/I) bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open-circuit voltages ( V OC , > 1 V). However, their short-circuit photocurrent density ( J SC ) has remained modest. The challenge for increasing the J SC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO 2 film and fast regeneration by the Cu(I) complex. Here, we report two new D-A-π-A featured sensitizers coded HY63 and HY64 , which employ either benzothiadiazole (BT) or phenanthrene-fused-quinoxaline (PFQ) as the auxiliary electron-withdrawing acceptor moiety. In spite of very similar energy levels and absorption onsets, HY64 -based DSSCs outperform largely their HY63 counterpart, achieving an outstanding power conversion efficiency (PCE) of 12.5% with superior stability. In depth studies of interfacial charge carrier dynamics show that PFQ is superior to BT in retarding charge recombination resulting in near quantitative collection of photogenerated charge carriers.

Synthesis and characterization of dimeric Schiff base CoII, NiII, CuII complexes for their catalytic application of aerobic oxidation of alcohol and interaction with biomolecules

Three new transition metal (Co(II), Ni(II) and Cu(II)) complexes of Schiff’s base ligand were prepared in situ by refluxing stoichiometric amounts of respective metal salts with 2-hydroxy-1-naphthaldehyde and 2-picolylamine. The structural feature of the synthesized complexes was derived from spectral (FT-IR, UV–Vis and ESI-mass) studies and elemental analysis. The single crystal X-ray diffraction analysis of complex 3 showed the structure as dimeric form [Cu(2-hnppa)Cl]2 and each copper atom is penta-coordinated. The calculated τ value of [Cu(2-hnppa)Cl]2 was 0.25 (where α = 157.84 and β = 172.18) indicating the square pyramidal geometry. Binding of these complexes (1–3) with calf thymus DNA was investigated by UV–Vis, fluorescence, viscosity measurements and computer aided molecular docking studies and the Kb value of complexes 1–3 were 2.4 × 105, 5.9 × 105 and 2.0 × 104M−1, respectively. The relative binding energies of the metal complexes 1–3 docked with DNA were −151.82, −151.86 and −151.80 eV, respectively. Complexes (1–3) exhibited a good binding capability with bovine serum albumin (BSA) with relatively high binding constant values. The complexes also act as a catalyst that enables efficient aerobic oxidation of a broad range of alcohols (benzyl alcohol, n-octanol) to the corresponding aldehydes at room temperature with ambient air as the oxidant.