Polypyridyl Ligands Research Articles

Design, synthesis, DNA-binding affinity, cytotoxicity, apoptosis, and cell cycle arrest of Ru(II) polypyridyl complexes

A novel polypyridyl ligand CNPFIP (CNPFIP=2-(5(4-chloro-2-nitrophenyl)furan-2-yl)-1H-imidazo[4,5f][1,10]phenanthroline) and its mononuclear Ru(II) polypyridyl complexes of [Ru(phen)2CNPFIP]2+(1) (phen=1,10-phenanthroline), [Ru(bpy)2CNPFIP]2+(2) (bpy=2,2′-bipyridine), and [Ru(dmb)2CNPFIP]2+(3) (dmb=4,4′-dimethyl-2,2′-bipyridine) have been synthesized successfully and characterized thoroughly by elemental analysis, UV/Vis, IR, NMR, and ESI-MS. The interaction of the Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by absorption titration, fluorescence, viscosity measurements. The experimental results suggest that three complexes bind to CT-DNA through an intercalative mode and the DNA-binding affinity of complex 1 is greater than that of complexes 2 and 3. The photocleavage of plasmid pBR322 DNA by ruthenium complexes 1, 2, and 3 was investigated. We have also tested three complexes for their antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. The in vitro cytotoxicity of these complexes was evaluated by MTT assay, and complex 1 shows higher cytotoxicity than 2 and 3 on HeLa cells. The induced apoptosis and cell cycle arrest of HeLa cells were investigated by flow cytometry for 24h. The molecular docking of ruthenium complexes 1, 2, and 3 with the active site pocket residues of human DNA TOP1 was performed using LibDock.

Polypyridyl iron(II) complexes showing remarkable photocytotoxicity in visible light

Iron(II) complexes of polypyridyl ligands (B), viz. [Fe(B)2]Cl2 (1 and 2) of N, N, N-donor 2-(2-pyridyl)-1,10-phenanthroline (pyphen in 1) and 3-(pyridin-2-yl)dipyrido[3,2-a:2’,3’-c]phenazine (pydppz in 2), are prepared and characterized. They are 1:2 electrolytes in aqueous DMF. The diamagnetic complexes exhibit metal to ligand charge transfer band near 570 nm in DMF. The complexes are avid binders to calf thymus DNA giving binding constant (K b) values of ∼106 M−1 suggesting significant intercalative DNA binding of the complexes due to presence of planar phenanthroline bases. Complex 2 exhibits significant photocytotoxicity in immortalized human keratinocyte cells HaCaT and breast cancer cell line MCF-7 giving IC50 values of 0.08 and 13 μM in visible light (400–700 nm). Complex 2 shows only minor dark toxicity in HaCaT cells but is non-toxic in dark in MCF-7 cancer cells. The light-induced cellular damage follows apoptotic pathway on generation of reactive oxygen species as evidenced from the dichlorofluorescein diacetate (DCFDA) assay. Iron(II) complex of pyridyldipyridophenazine base shows remarkable photocytotoxic effect in MCF-7 and HaCaT cell lines upon visible light irradiation (400–700 nm) via apoptotic pathway on generation of reactive oxygen species.

Investigation of antibacterial activity and related mechanism of a ruthenium(II) polypyridyl complex

Metal based drug represents a novel group of antimicrobial agents with potential application for the control of bacterial and fungal infections. In this study, we fabricate ruthenium(II) complex containing the polypyridyl ligands, namely [Ru(phen)2(tip)] (ClO4)2 (RuTh) and carefully investigate its antibacterial activities against both the Gram-negative (G−) bacteria Escherichia coli (E. coli) and the Gram-positive (G+) bacteria Staphylococcus aureus (S. aureus). The RuTh is more toxic to S. aureus than that to E. coli. The antibacterial effects of RuTh are further investigated, revealing specific mechanisms. The results demonstrate that RuTh functions as a bactericide against the E. coli and S. aureus through disrupting bacterial cell wall integrity and its cellular components.

Expanding the family of heteroleptic oxidovanadium(IV) compounds with salicylaldehyde semicarbazones and polypyridyl ligands showing anti-Trypanosoma cruzi activity

Searching for prospective vanadium-based drugs for the treatment of Chagas disease, a new series of heteroleptic [VIVO(L-2H)(NN)] compounds was developed by including the lipophilic 3,4,7,8-tetramethyl-1,10-phenanthroline (tmp) NN ligand and seven tridentate salicylaldehyde semicarbazone derivatives (L1–L7). The compounds were characterized in the solid state and in solution. EPR spectroscopy suggests that the NN ligand is bidentate bound through both nitrogen donor atoms in an axial–equatorial mode. The EPR and 51V-NMR spectra of aerated solutions at room temperature indicate that the compounds are stable to hydrolysis and that no significant oxidation of VIV to VV takes place at least in 24h. The complexes are more active in vitro against Trypanosoma cruzi, the parasite responsible for Chagas disease, than the reference drug Nifurtimox and most of them are more active than previously reported [VIVO(L-2H)(NN)] complexes of other NN co-ligands. Selectivity towards the parasite was analyzed using J-774 murine macrophages as mammalian cell model. Due to both, high activity and high selectivity, L2, L4, L5 and L7 complexes could be considered new hits for further drug development. Lipophilicity probably plays a relevant role in the bioactivity of the new compounds. The [VIVO(L-2H)(NN)] compounds were designed aiming DNA as potential molecular target. Therefore, the novel L1–L7 tmp complexes were screened by computational modeling, comparing their DNA-binding features with those of previously reported [VIVO(L-2H)(NN)] compounds with different NN co-ligands. Whereas all the complexes interact well with DNA, with binding modes and strength tuned in different extents by the NN and semicarbazone co-ligands, molecular docking suggests that the observed anti-T. cruzi activity cannot be explained upon DNA intercalation as the sole mechanism of action.

Kinetics and Thermodynamics of Formation and Electron‐Transfer Reactions of Surfactant Cobalt(III) Complexes Containing Polypyridyl Ligands with Fe(CN)64−in Microheterogeneous Environment

ABSTRACTThe electron‐transfer reaction of some surfactant cobalt(III) complexes,cis‐[Co(ip)2(C12H25NH2)2]3+1,cis‐[Co(dpq)2(C12H25NH2)2]3+2, andcis‐[Co(dpqc)2(C12H25NH2)2]3+3(ip = imidazo[4,5‐f][1,10]phenanthroline, dpq = dipyrido[3,2‐d:2′‐3′‐f]quinoxaline, dpqc = dipyrido[3,2‐a:2′,4′‐c](6,7,8,9‐tetrahydro)phenazine, C12H25NH2= dodecylamine) with the Fe(CN)64−ion has been investigated in microheterogeneous media (micelles, β‐cyclodextrin) at different temperatures by the spectrophotometric method under pseudo‐first‐order conditions using an excess of the reductant. Experimentally, the reaction was found to be second order and the electron transfer postulated as an outer sphere. The rate constant for the electron‐transfer reaction in micelles was found to increase with an increase in the initial concentration of the surfactant–cobalt(III) complex. This peculiar behavior of dependence of the second‐order rate constant on the initial concentration of one of the reactants has been attributed to the presence of various concentrations of micelles under different initial concentrations of the surfactant–cobalt(III) complex in the reaction medium. Inclusion of the long aliphatic chain of the surfactant complex ion into β‐cyclodextrin leads to decrease in the rate constant. Kinetic data and activation parameters are interpreted in terms of an outer‐sphere electron‐transfer mechanism. All these results have been interpreted in terms of the hydrophobic effect and the reactants with the opposite charge.

Coordination assemblies of CdIIwith 2,2′:6′,2′′-terpyridine (terpy), 2,3,5,6-tetra-(2-pyridyl)pyrazine (tppz) and pseudohalide ions – structural diversification and luminescence properties

Nine new terpy- or tppz-containing cadmium(II) coordination compounds, [Cd(μ1,5-dca)(NO3)(terpy)]n (1), [Cd(μ1,5-dca)(terpy)(H2O)]n·n(dca) (2), [Cd(μ1,3-N3)(NO3)(terpy)]n (3), [Cd(N3)(NO3)(terpy)(H2O)] (4), [Cd2(μ1,1-N3)2(N3)2(terpy)2] (5), [Cd(μ1,5-dca)(NO3)(tppz)]n (6), [Cd(dca)(NO3)(tppz)(H2O)] (7), [Cd2(μ1,1-N3)2(NO3)2(μ-tppz)]n·2nMeOH (8) and [Cd2(μ1,1-N3)(μ1,3-N3)(m-tppz)]n (9), have been successfully synthesized in the reaction of Cd(NO3)2 with multidentate N-heterocyclic ligands and inorganic ions (N3− and N(NC)2− abbreviated as dca−). The resulting compounds were structurally characterized by single crystal X-ray diffraction analysis and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (XRPD), and thermogravimetric analyses (TGA). The X-ray studies demonstrated a cooperative impact of the polypyridyl ligand and the auxiliary inorganic ion on the final molecular architectures of cadmium(II) coordination compounds. Different topologies, ranging from mononuclear molecular to two-dimensional coordination networks, were confirmed for 1–9. The photoluminescence behaviour of 1–9 was also discussed. All of these coordination compounds are luminescent in the solid state, with the emission maxima varying in the visible light region within the range of 460–600 nm. The difference in emission behaviour for 1–9 is attributed to the coordination environments of the metal ions and the rigidity of solid-state crystal packing.

Synthesis, characterization, DNA/BSA interactions and anticancer activity of achiral and chiral copper complexes.

Six novel copper(ii) complexes of [CuCl]ClO4 (), [Cu(acac)]PF6 (), [CuCl]2(PF6)2 (), [CuCl]2(PF6)2 (), [Cu(acac)]PF6 () and [Cu(acac)]PF6 (), ( = 1-naphthyl-N,N-[bis(2-pyridyl)methyl]amine, = R/S-1-naphthyl-N,N-[bis(2-pyridyl)methyl]ethanamine, acac = diacetone) were synthesized to serve as artificial nucleases. All complexes were structurally characterized using X-ray crystallography. The crystal structures showed the presence of distorted square-planar CuLCl (, and ) and distorted tetragonal-pyramidal CuL(acac) (, and ) geometry. The interaction of these complexes with calf thymus DNA (CT-DNA) was researched by means of several spectroscopy methods, which indicated that the complexes were bound to CT-DNA by an intercalation binding mode. DNA cleavage experiments revealed that the complexes exhibited remarkable DNA cleavage activities in the presence of H2O2, and single oxygen ((1)O2) or hydroxyl radicals may serve as the major cleavage active species. In particular, the in vitro cytotoxicity of the complexes on four human cancer cell lines (HeLa, MCF-7, Bel-7404 and HepG-2) demonstrated that the six compounds had broad-spectrum anti-cancer activity with low IC50 values. The stronger cytotoxicity and DNA cleavage activity of the chiral enantiomers compared with chiral analogues verified the influence of chirality on the antitumor activity of complexes. Meanwhile, the protein binding ability was revealed by quenching of tryptophan emission with the addition of complexes using BSA as a model protein. The results indicated that the quenching mechanism of BSA by the complexes was a static process.

Metal-organic microstructures: from rectangular to stellated and interpenetrating polyhedra.

Despite the tremendous progress made in the design of supramolecular and inorganic materials, it still remains a great challenge to obtain uniform structures with tailored size and shape. Metal-organic frameworks and infinite coordination polymers are examples of rapidly emerging materials with useful properties, yet limited morphological control. In this paper, we report the solvothermal synthesis of diverse metal-organic (sub)-microstructures with a high degree of uniformity. The porous and thermally robust monodisperse crystalline solids consist of tetrahedral polypyridyl ligands and nickel or copper ions. Our bottom-up approach demonstrates the direct assembly of these materials without the addition of any surfactants or modulators. Reaction parameters in combination with molecular structure encoding are the keys to size-shape control and structural uniformity of our metal-organic materials.

Catalytic water oxidation by ruthenium(II) quaterpyridine (qpy) complexes: evidence for ruthenium(III) qpy-N,N'''-dioxide as the real catalysts.

Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation-resistant and can stabilize high-oxidation-state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2 ](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze Ce(IV) -driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy-N,N'''-dioxide (ONNO) complexes [Ru(ONNO)(L)2 ](3+) which are the real catalysts for water oxidation.

DNA-binding and cytotoxic efficacy studies of organorhenium pentylcarbonate compounds

Seven organorhenium pentylcarbonate compounds (PC1-PC7) have been synthesized. DNA-binding studies of the PC-series compounds using electronic spectroscopy and gel electrophoresis suggest that the compounds presumably bind to DNA in an intercalative mode. The intrinsic binding constants for PC4, PC6, and PC7 were found to be 1.6 × 10(4), 3.9 × 10(4), and 4.2 × 10(4) M(-1), respectively. The X-ray structure determinations and density functional theory calculations indicate that the polypyridyl ligands in the compounds are nearly planar facilitating DNA binding through an intercalation mechanism. Cytotoxicity studies of 10 µM pentylcarbonate compounds against HTB-12 human astrocytoma brain cancer cells were studied for 48 h. It was observed that each of the pentylcarbonate compounds is active against the cancer cells. However, under analogous conditions, CRL-2005 rat astrocyte normal brain cells are not affected significantly.

Electron transfer reactions of methionine peptides with photochemically generated ruthenium(III)–polypyridyl complexes

Abstract The dynamics of the oxidation of five methionine carrying peptides with six Ru(III)–polypyridyl complexes in aqueous acetonitrile medium have been followed by spectrophotometric technique. The electron transfer (ET) reaction of [Ru(NN) 3 ] 3+ complex (NN = polypyridyl ligand) with peptide containing methionine is sensitive to the change in the structure of ligand of Ru(III) complex and N-terminal component of the peptide Met-Gly Met-Ala Met-Ser Met-Val and Met-Leu. The reaction follows the overall second-order kinetics, first order each in the oxidant and the substrate. Based on the substituent and solvent effects, an outer-sphere electron transfer from the sulfur center of the peptide to Ru(III) has been proposed as the rate controlling step of the reaction. The ET nature of the reaction is confirmed from the recorded transient absorption spectrum of peptide containing methionine sulfur radical cation by laser flash photolysis technique. Marcus theory is successfully applied to the ET reaction.

Synthesis, characterization, and antitumor activity of unusual pseudo five coordinate gold(III) complexes: Distinct cytotoxic mechanism or expensive ligand delivery systems?

Gold(III) complexes bearing bidentate ligands based on the 1,10-phenanthroline and 2,2′-bipyridine scaffolds have shown promising anticancer activity against a variety of tumor cell lines. In particular, our laboratory has previously found that a pseudo five coordinate gold(III) complex possessing the 2,9-di-sec-butyl-1,10-phenanthroline ligand {[(di-sec-butylphen)AuCl3]} exhibits antitumor activity against a panel of five different lung and head–neck tumor cell lines. However, the [(di-sec-butylphen)AuCl3] complex was determined to be less active than the free 2,9-di-sec-butyl-1,10-phenanthroline ligand. In order to determine if this class of gold(III) complexes has a distinct mechanism of initiating tumor cell death or if these gold complexes simply release the polypyridyl ligand in the intracellular environment, structural analogues of the [(di-sec-butylphen)AuCl3] complex have been synthesized and structurally characterized. These structural congeners were prepared by using mono-alkyl and di-phenyl substituted 1,10-phenanthroline ligands, di-alkyl and di-phenyl substituted 4-methyl-1,10-phenanthroline ligands, and mono-alkyl 2,2′-bipyridine ligands. The redox stability of this library of distorted square pyramidal gold(III) complexes has been studied and the in vitro antitumor activity of gold(III) complexes and corresponding polypyridyl ligands has been determined. The [(di-n-butylphen)AuCl3] and [(mono-n-butylphen)AuCl3] complexes have been found to be significantly more potent at inhibiting the growth of A549 lung tumor cells than the clinically used drug cisplatin. More importantly, these two gold(III) complexes are significantly more active than their respective free ligands, providing evidence that this class of pseudo five coordinate gold(III) complexes has a mechanism of initiating tumor cell death that is independent of the free ligand.

A well-defined terminal vanadium(III) oxo complex.

The ubiquity of vanadium oxo complexes in the V+ and IV+ oxidation states has contributed to a comprehensive understanding of their electronic structure and reactivity. However, despite being predicted to be stable by ligand-field theory, the isolation and characterization of a well-defined terminal mononuclear vanadium(III) oxo complex has remained elusive. We present the synthesis and characterization of a unique terminal mononuclear vanadium(III) oxo species supported by the pentadentate polypyridyl ligand 2,6-bis[1,1-bis(2-pyridyl)ethyl]pyridine (PY5Me2). Exposure of [V(II)(NCCH3)(PY5Me2)](2+) (1) to either dioxygen or selected O-atom-transfer reagents yields [V(IV)(O)(PY5Me2)](2+) (2). The metal-centered one-electron reduction of this vanadium(IV) oxo complex furnishes a stable, diamagnetic [V(III)(O)(PY5Me2)](+) (3) species. The vanadium(III) oxo species is unreactive toward H- and O-atom transfer but readily reacts with protons to form a putative vanadium hydroxo complex. Computational results predict that further one-electron reduction of the vanadium(III) oxo species will result in ligand-based reduction, even though pyridine is generally considered to be a poor π-accepting ligand. These results have implications for future efforts toward low-valent vanadyl chemistry, particularly with regard to the isolation and study of formal vanadium(II) oxo species.

The photophysics of fac-[Re(CO)3(NN)(bpa)]+ complexes: a theoretical/experimental study

The influence of the polypyridyl ligand on the photophysics of fac-[Re(CO)3(NN)(bpa)](+), bpa = 1,2-bis-(4-pyridyl)ethane and NN = 1,10-phenanthroline (phen), pyrazino[2,3-f][1,10]-phenanthroline (dpq), and dipyrido[3,2-a:2'3'-c]phenazine (dppz) has been investigated by steady state and time-resolved emission spectroscopy combined with theoretical calculations using time-dependent density functional theory (TD-DFT). The fac-[Re(CO)3(phen)(bpa)](+) is a typical MLCT emitter in acetonitrile with ϕ = 0.11 and τ = 970 ns. The emission lifetime and quantum yield decrease significantly in fac-[Re(CO)3(dpq)(bpa)](+) (ϕ = 0.05; τ = 375 ns) due to the presence of a close lying dark charge transfer state located at the pyrazine ring of dpq, as indicated by TD-DFT data. The luminescence of these complexes is quenched by hydroquinone with kq = (2.9 ± 0.1) × 10(9) and (2.6 ± 0.1) × 10(9) L mol(-1) s(-1), respectively, for NN = phen or dpq. These values are increased respectively to (4.6 ± 0.1) × 10(9) and (4.2 ± 0.1) × 10(9) L mol(-1) s(-1) in the 1 : 1 H2O-CH3CN mixture. In this medium Stern-Volmer constants determined by steady-state and time-resolved measurements differ from each other, which is indicative of static quenching, i.e. the pre-association of hydroquinone and the complexes through hydrogen bonding between the remote N-atom in the bpa ligand (KA ≅ 1-2 × 10(1) L mol(-1)), followed by a concerted proton-electron transfer. In contrast to other investigated complexes, fac-[Re(CO)3(dppz)(bpa)](+) is weakly emissive in acetonitrile at room temperature (ϕ ≅ 10(-4)) and does not exhibit a rigidochromic effect. This photophysical behaviour as well as TD-DFT data indicate that the lowest lying triplet excited state can be described as (3)ILdppz. The results provide additional insight into the influence of the polypyridyl ligand on the photophysical properties of Re(I) complexes.

New water oxidation chemistry of a seven-coordinate ruthenium complex with a tetradentate polypyridyl ligand.

The mononuclear ruthenium(II) complex [Ru](2+) (Ru = Ru(dpp)(pic)2, where dpp is the tetradentate 2,9-dipyrid-2'-yl-1,10-phenanthroline ligand and pic is 4-picoline) reported by Thummel's group (Inorg. Chem. 2008, 47, 1835-1848) that contains no water molecule in its primary coordination shell is evaluated as a catalyst for water oxidation in artificial photosynthesis. A detailed theoretical characterization of the energetics, thermochemistry, and spectroscopic properties of intermediates allowed us to interpret new electrochemical and spectroscopic experimental data, and propose a mechanism for the water oxidation process that involves an unprecedented sequence of seven-coordinate ruthenium complexes as intermediates. This analysis provides insights into a mechanism that generates four electrons and four protons in the solution and a gas-phase oxygen molecule at different pH values. On the basis of the calculations and corroborated substantially by experiments, the catalytic cycle goes through [(2)Ru(III)](3+) and [(2)Ru(V)(O)](3+) to [(1)Ru(IV)(OOH)](3+) then [(2)Ru(III)(···(3)O2)](3+) at pH 0, and through [(3)Ru(IV)(O)](2+), [(2)Ru(V)(O)](3+), and [(1)Ru(IV)(OO)](2+) at pH 9 before reaching the same [(2)Ru(III)(···(3)O2)](3+) species, from which the liberation of the weakly bound O2 might require an additional oxidation to form [(3)Ru(IV)(O)](2+) to initiate further cycles involving all seven-coordinate species.

Controlling ground and excited state properties through ligand changes in ruthenium polypyridyl complexes.

The capture and storage of solar energy requires chromophores that absorb light throughout the solar spectrum. We report here the synthesis, characterization, electrochemical, and photophysical properties of a series of Ru(II) polypyridyl complexes of the type [Ru(bpy)2(N-N)](2+) (bpy = 2,2'-bipyridine; N-N is a bidentate polypyridyl ligand). In this series, the nature of the N-N ligand was altered, either through increased conjugation or incorporation of noncoordinating heteroatoms, as a way to use ligand electronic properties to tune redox potentials, absorption spectra, emission spectra, and excited state energies and lifetimes. Electrochemical measurements show that lowering the π* orbitals on the N-N ligand results in more positive Ru(3+/2+) redox potentials and more positive first ligand-based reduction potentials. The metal-to-ligand charge transfer absorptions of all of the new complexes are mostly red-shifted compared to Ru(bpy)3(2+) (λmax = 449 nm) with the lowest energy MLCT absorption appearing at λmax = 564 nm. Emission energies decrease from λmax = 650 nm to 885 nm across the series. One-mode Franck-Condon analysis of room-temperature emission spectra are used to calculate key excited state properties, including excited state redox potentials. The impacts of ligand changes on visible light absorption, excited state reduction potentials, and Ru(3+/2+) potentials are assessed in the context of preparing low energy light absorbers for application in dye-sensitized photoelectrosynthesis cells.

Controlled Electropolymerization of Ruthenium(II) Vinylbipyridyl Complexes in Mesoporous Nanoparticle Films of TiO2

AbstractSurface‐initiated, oligomeric assemblies of ruthenium(II) vinylpolypyridyl complexes have been grown within the cavities of mesoporous nanoparticle films of TiO2 by electrochemically controlled radical polymerization. Surface growth was monitored by cyclic voltammetry as well as UV/Vis and X‐ray photoelectron spectroscopy. Polymerization occurs by a radical chain mechanism following cyclic voltammetry scans to negative potentials where reduction occurs at the π* levels of the polypyridyl ligands. Oligomeric growth within the cavities of the TiO2 films occurs until an average of six repeat units are added to the surface‐bound initiator site, which is in agreement with estimates of the internal volumes of the pores in the nanoparticle films.

Ir(N^N^N)(C^N)L]+: A New Family of Luminophores Combining Tunability and Enhanced Photostability

The relatively unexplored luminophore architecture [Ir(N^N^N)(C^N)L](+) (N^N^N = tridentate polypyridyl ligand, C^N = 2-phenylpyridine derivative, and L = monodentate anionic ligand) offers the stability of tridentate polypyridyl coordination along with the tunability of three independently variable ligands. Here, a new family of these luminophores has been prepared based on the previously reported compound [Ir(tpy)(ppy)Cl](+) (tpy = 2,2':6',2″-terpyridine and ppy = 2-phenylpyridine). Complexes are obtained as single stereoisomers, and ligand geometry is unambiguously assigned via X-ray crystallography. Electrochemical analysis of the materials reveals facile HOMO modulation through ppy functionalization and alteration of the monodentate ligand's field strength. Emission reflects similar modulation shifting from orange to greenish-blue upon replacement of chloride with cyanide. Many of the new compounds exhibit impressive room temperature phosphorescence with lifetimes near 3 μs and quantum yields reaching 28.6%. Application of the new luminophores as photosensitizers for photocatalytic hydrogen generation reveals that their photostability in coordinating solvent is enhanced as compared to popular [Ir(ppy)2(bpy)](+) (bpy = 2,2'-bipyridine) photosensitizers. Yet, the binding of their monodentate ligand emerges as a source of instability during the redox processes of cyclic voltammetry and mass spectrometry. DFT modeling of electronic structure is provided for all compounds to elucidate experimental properties.

Synthesis, structure, characterization and photophysical properties of copper(i) complexes containing polypyridyl ligands

Two novel photoluminescent copper(i) complexes have been successfully synthesized and characterized. Both complexes showed interesting photophysical properties.

Heterobimetallic Complexes of Polypyridyl Ligands Containing Paramagnetic Centers: Synthesis and Characterization by IR and EPR

Ligands containing linked dipicolylamine (dpa) and bipyridine sites have been explored as platforms for the synthesis of heterometallic complexes containing the paramagnetic metals Cu(2+) and Co(2+). IR and EPR studies on the bimetallic complexes and simplified model compounds support dpa-selective binding by both of these metals. The IR spectra have also been compared to those of diamagnetic Rh(+), Zn(2+), and Pd(2+) complexes whose metal binding sites had been independently determined through NMR techniques. The binding preferences have been used to control selective metalation in the synthesis of heterometallic Pt/Cu, Pd/Cu, and Rh/Cu complexes.