Spectroscopy and photophysics of binuclear ruthenium(II) complexes with nitrogen-containing heterocyclic bridging ligands

The absorption spectra at room temperature and the spectra, the quantum yields, and the decay times of the luminescence at 77 K of binuclear complexes [X(bpy)₂Ru(BL)Ru(bpy)₂Cl]²⁺ (bpy = 2,2′-bipyridyl; X = Cl, BL = pyrazine, 4,4′-bipyridyl, trans-1,2-bis(4-pyridyl)ethylene, and trans-1,2-bis(4-pyridyl)ethane and X = NO₂, BL = 4,4′-bipyridyl) in alcoholic (4: 1 EtOH-MeOH) solutions are studied. It is shown that the interaction between the metal centers (MCs) of the complexes affects the characteristics of the electronically excited states (EESs) of each of them and facilitates increasing the transition dipole moment Ru(d_π)→BL(π_*). The deactivation rate constants of the lowest electronically excited metal-to-ligand charge transfer (³MLCT) state of the complexes are determined. In an asymmetric binuclear complex, the energy transfer from MC(NO₂) to MC(Cl) is revealed, with the rate constant of this transfer being not smaller than 3.2 × 10¹⁰ s^?1.     

Spectroscopy and quantum-chemical calculations of nitro-bis-bipyridyl complexes of ruthenium(II) with 4-substituted pyridine ligands

The luminescence, absorption, and luminescence excitation spectra of complexes cis-[Ru(bpy)₂(L)(NO₂)]⁺ [bpy = 2,2′-bipyridyl, L = pyridine, 4-aminopyridine, 4-dimethylaminopyridine, 4-picoline, isonicotinamide, or 4,4′-bipyridyl] in alcoholic (4 : 1 EtOH–MeOH) solutions are studied at 77 K. A linear correlation is established between the energy of the lowest electronically excited metal-toligand charge transfer state d_π(Ru) → π*(bpy) of the complexes and the pK_a parameter of the free 4-substituted pyridines used as ligands L. The B3LYP/[6-31G(d)+LanL2DZ(Ru)] hybrid density functional method is used to optimize the geometry of complexes and calculate their electronic structure and the charge distribution on the atoms of the nearest environment of ruthenium(II) ions. It is shown that there exists a mutually unambiguous correspondence between the charge on the nitrogen atom of ligands L coordinated in the complex and the pK_a parameter of ligands. The calculated energies of the electronically excited metal-to-ligand charge transfer states of complexes linearly (correlation coefficient 0.99) depend on the charge on the nitrogen atom of ligands L, which completely agrees with the experimental data.     

Spectroscopic and quantum-chemical investigations of chloro-bis-bipyridyl complexes of ruthenium(II) with 4-substituted pyridine ligands

The luminescence spectra of cis-[Ru(bpy)₂(L)Cl]⁺ (bpy is 2,2′-bipyridyl; L is pyrazine, pyridine, 4-amino-pyridine, 4-picolin, isonicotinamide, 4-cyanopyridine, or 4,4′bipyridyl) complexes are studied in alcoholic (4: 1 EtOH-MeOH) solutions at 77 K. A linear correlation is found between the energy of the lowest electronically excited metal-to-ligand charge transfer (³MLCT) state d _π(Ru) → π* (bpy) and the parameter pK _a of the free 4-substituted pyridines and pyrazine used as ligands L. The [B3LYP/6-31G + LanL2DZ(Ru)] hybrid method of the density functional theory is used to optimize the geometry of complexes and calculate their electronic structure and the charge distribution on the atoms of the nearest environment of the ruthenium ion. It is shown that there exists a linear unambiguous correlation between the negative charge on the nitrogen atom (qN ^L) of ligands L coordinated in the complex and the parameters pK _a of free ligands. The calculated energies of ³MLCT excited states almost linearly (correlation coefficient 0.958) depend on the charge qN ^L, which completely agrees with experimental data.     

Photophysics of the adsorbed bipyridyl complexes of ruthenium(II) with phosphines

Luminescence of the ruthenium(II) complexes cis-Ru(bpy)₂(CN)₂ (I), cis-[Ru(bpy)₂(PPh₃)CN](BF₄) (II), and cis-Ru(bpy)(dppe)(CN)₂ (III)[bpy=2.2′-bipyridyl, PPh₃=triphenylphosphine, dppe=1,2-bis(diphenylphosphino)ethane], adsorbed on silicon oxide (Aerosil) were studied at a temperature of 77 K. The luminescence spectra, decay times, and quantum yields were measured, and the intermolecular rate constants of radiative transitions and nonradiative decay of the excited electronic state with the metal-to-ligand charge transfer (MLCT) were determined. It is found that the adsorption of the complex is accompanied by a decrease in the energy of the radiative MLCT state and by a considerable acceleration of its nonradiative decay. It is concluded that the interaction of the complexes with the surface adsorption centers occurs via formation of a strong hydrogen bond with a hydroxyl-hydrate cover, the interaction of complexes in the ³MLCT state being stronger than in the ground state. The additive (in the number of phosphorus atoms coordinated to the central ruthenium ion), a shift of the absorption and luminescence bands to shorter wavelengths in the sequence of complexes I–III, is retained when the complexes transform from solutions to the absorbed state.     

Energy scan of cross sections for <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>–</Superscript> annihilation into quarkonia and light hadrons in the Belle experiment

The cross sections of the reactions e⁺e^– → ?(nS)π⁺π^? (n = 1, 2,3) and e⁺e^– → h _b (nP)π⁺π^? (n = 1, 2) are measured as a function of the cms collision energy from their thresholds up to 11.02 GeV using the data of the Belle experiment operating at the KEKB e⁺e^– collider. The peaks of the ?(10 860) and ?(11020) resonances are observed in the cross sections with an insignificant contribution of the continuum. The decay ?(11020) → h _b (nP)π⁺π^? is found to fully proceed through intermediate isovector states Z _b (10610) and Z _b (10650).     

Phenomenology of light- and strange-quark simultaneous production at high energies

This letter presents an extension of EPL116(2017)62001 to light- and strange-quark nonequilibrium chemical phase-space occupancy factors (γ_q,s). The resulting damped trigonometric functionalities relating γ_q,s to the nucleon-nucleon center-of-mass energies (\(\sqrt {{s_{NN}}} \)) looks very similar except different coefficients. The phenomenology of the resulting γ_q,s(\(\sqrt {{s_{NN}}} \)) describes a rapid decrease at \(\sqrt {{s_{NN}}} \) ? 7GeV followed by a faster increase up to ~20 GeV. Then, both γ_q,s become nonsensitive to \(\sqrt {{s_{NN}}} \). Although these differ from γ _s (\(\sqrt {{s_{NN}}} \))obtained at γ _q (\(\sqrt {{s_{NN}}} \))=1, various particle ratios including K⁺/π⁺, K^?/π^?, Λ/π^?, Λ?/π^?, Ξ⁺/π⁺, and Ω/π^?, can well be reproduced, as well. We conclude that γ_q,s(\(\sqrt {{s_{NN}}} \)) should be instead determined from fits of various particle yields and ratios but not merely from fits to the particle ratio K⁺/π⁺.     

Proton-proton interaction with high multiplicity at energy of 70 GeV (proposal)

The goal of the proposed experiment is to investigate the collective behavior of particles in the process of multiple hadron production in pp interaction pp → n _π π + 2N at the beam energy E_lab = 70 GeV. The domain of high multiplicity n _π = 30–40, or z = n/\(\bar n\) = 4–6, will be studied. Near the threshold of reaction n _π → 69, z → z_th = 8.2, all particles acquire small relative momentum Δq < 1/R, where R is the dimension of the particle production region. As a consequence of multiboson interference, a number of collective effects may show up: (a) a drastic increase in the partial cross section σ(n) of production of n identical particles is expected, compared with commonly accepted extrapolation; (b) the formation of jets consisting of identical particles may occur as a result of the multiboson Bose-Einstein correlation (BEC) effect; (c) a large fluctuation of charged n(π⁺,π^?) and neutral n(π⁰) components and onset of centauros or chiral condensate effects are anticipated; (d) an increase in the rate of direct γ as a result of the bremsstrahlung in the partonic cascade and annihilation of π⁺π^? → nγ in dense and cold pionic gas or condensate is expected. In the domain of high multiplicity z ≥ 5, a major part of the c.m. energy \(\sqrt s = 11.6\) GeV is materialized, leading to a high-density thermalized hadronic system. Under this condition, a phase transition to cold quark-gluon plasma (QGP) may occur. The search for QGP signatures like large intermittency in the phase-space particle distribution and an enhanced rate of direct photons will be performed. The experimental setup is designed for detection of rare high-multiplicity events. The experiment is to be carried out at the extracted proton beam of the IHEP U-70 accelerator. The required beam intensity is ～10⁷ s^?1. Under the assumption that the partial cross section σ(n _π = 35) = 10-1 nb, the anticipated counting rate is 10-1 events/h. The multiboson BEC enhancement may drastically increase the counting rate.     

Using a chiral anomaly to determine the number of colors

The N_c dependence of PPPγ vertices, where P is a pseudoscalar meson and N_c is the number of colors, is analyzed with allowance for the N_c dependence of the quark charges. It is shown that the reactions Kγ → Kπ and π^±γ → π^±η and the decay η → π⁺π^?γ are the best processes for determining N_c. The cross section σ(π^?γ → π^?η) as measured by using the VES facility at IHEP agrees with the value of N_c=3.     

Estimating of CP-violation in <Emphasis Type="Italic">B</Emphasis><Superscript>0</Superscript>→ψ(2<Emphasis Type="Italic">S</Emphasis>)π<Superscript>0</Superscript> decay

I present estimates of CP-violating asymmetries in the non-leptonic charmonium two-body B⁰→ψ(2S)π⁰ decay and the same decays of B⁺→ψ(2S)π⁺ and B⁺→ψ(2S)K⁺ These estimates are based on QCD and improved QCD factorization approach making use of next-to-leading order (NLO) contributions. The CP-violating asymmetry for B⁰→ψ(2S)π⁰ decay is not available, according to the same calculations, it is expected if it can be measured in the future its value will be S_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.662 ± 0.197 and C_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.024 ± 0.007.     

The Structure of Radiative Tunnel Recombination Sites in Emulsion Microcrystals of AgBr(I)

To identify the structure of emissive tunnel recombination sites in the emulsion microcrystals of silver bromide AgBr(I) with iodine contaminations and to determine the role of an emulsion medium in their formation, the temperature dependence of the luminescence spectra in the range from 77 to 120 K, the kinetics of the growth of the maximum luminescence intensity value at λ ≈ 560 nm, and the luminescence flash spectrum stimulated by the infrared light are investigated. Two types of the AgBr_{1 – x}(I _x ) (x = 0.03) microcrystals—namely, obtained in an aqueous solution and on a gelatin substrate—are used in the studies. It is established that the emissive tunnel recombination sites with a luminescence maximum at λ ≈ 560 nm in AgBr_{1 – x}(I _x ) (x = 0.03) are the {(I _a ^- I _a ^- )Ag _i ⁺ } donor–acceptor complexes with the I _a ^- iodine ions located in neighbor anionic sites of the AgBr(I) crystal lattice, next to which the Ag _i ⁺ interstitial silver ion is positioned. With an increase in the temperature, the {(I _a ^- I _a ^- )Ag _i ⁺ } sites undergo structural transformation into the {(I _a ^- I _a ^- )Ag_in⁺} sites, where n = 2, 3, …. Moreover, the {(I _a ^- I _a ^- )Ag _in ⁺ } sites (n = 2) after the capture of an electron and hole also provide the tunnel recombination with a luminescence maximum at λ ≈ 720 nm. The influence of an emulsion medium consists in that gelatin interacts with the surface electron-localization sites, i.e., the interstitial silver ions Ag _in ⁺ , n = 1, 2, and forms the complexes {Ag _in ⁰ G⁺} (n = 1, 2) with them. The latter are deeper electron traps with a small capture cross section as compared to the Ag _in ⁺ sites (n = 1, 2) and that manifest themselves in that the kinetics of the luminescence growth in AgBr(I) to a stationary level at λ ≈ 560 nm is characterized by the presence of “flash firing.” At the same time, the luminescence flash stimulated by IR light, for which the Ag _in ⁺ (n = 1, 2) electron-localization sites are responsible, is absent. It is supposed that the electrons localized on the {Ag _in ⁺ G⁺} complexes (n = 2) retain the capability for emissive tunnel recombination with holes localized on paired iodine sites with a luminescence maximum at λ ≈ 750 nm.     

Effect of <Emphasis Type="Italic">Z′</Emphasis>-mediated flavor-changing neutral current on <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">ππ</Emphasis> decays

We study the effect of Z′-mediated flavor-changing neutral current on the B → ππ decays. The branching ratios of these decays can be enhanced remarkably in the nonuniversal Z′ model. Our estimated branching ratios B(B ⁰ → π ⁰ π ⁰) are enhanced significantly from their standard model (SM) value. For g′/g = 1, the branching ratios B(B ⁰ → π ⁰ π ⁰) are very close to the recently observed experimental values and for higher values of g′/g branching ratios are more. Our calculated branching ratios B(B ⁰ → π ⁺ π ^?) and B(B ⁺ → π ⁺ π ⁰) are also enhanced from the SM value as well as the recently observed experimental values. These enhancements of branching ratios from their SM value give the possibility of new physics.     

Study of the reaction π–<Emphasis Type="Italic">A</Emphasis> π<Superscript>+</Superscript>π<Superscript>–</Superscript>π<Superscript>–</Superscript><Emphasis Type="Italic">A</Emphasis> at large statistics with VES setup

Partial wave analysis of the π–A π⁺π^–π^– system produced by 29 GeV/cπ^– beam on a beryllium target is presented. About 30 × 10⁶ |events in the wide t′|range 0–0.8 GeV²/c ² are collected with upgraded VES setup. The size of the data sample is 2.5 times larger than one previously analyzed by VES. Data are analyzed using formalism of the density matrix with unlimited rank. We discuss status of the a ₁(1420) a ₂(1700) a ₃(1875) states and a structure of exotic ρ(770)π P-wave with J ^PC = 1^-+. Parameters of a ₃(1875) are estimated as M = 1985 ± 20 MeV/c ², Γ = 200 ± 50 MeV/c ² (preliminary).     

Ds+ → π+ π+ π− decay: The $$1^3 P_0 s\bar s$$ component in scalar-isoscalar mesons

We calculate the processes \(D_s^ + \to \pi ^ + s\bar s\) and D _s ⁺ → π⁺resonance, respectively, in the spectator and W-annihilation mechanisms. The data on the reaction D _s ⁺ → π⁺ρ⁰, which is due to the W-annihilation mechanism only, point to a negligibly small contribution of the W annihilation to the production of scalar-isoscalar resonances D _s ⁺ ?π⁺f₀. As to spectator mechanism, we evaluate the \(1^3 P_0 s\bar s\) component in the resonances f₀(980), f₀(1300), and f₀(1500) and broad state f₀(1200–1600) on the basis of data on the decay ratios D _s ⁺ ?π⁺f₀/(D _s ⁺ ?π⁺_θ). The data point to a large \(s\bar s\) component in the \(f_0 (980):40 \lesssim s\bar s \lesssim 70\% \). Nearly 30% of the \(1^3 P_0 s\bar s\) component flows to the mass region 1300–1500 MeV, being shared by f₀(1300), f₀(1500), and broad state f₀(1200–1600): the interference of these states results in a peak near 1400 MeV with the width around 200 MeV. Our calculations show that the yield of the radial-excitation state\(2^3 P_0 s\bar s\)is relatively suppressed, \({{\Gamma (D_s^ + \to \pi ^ + (2^3 P_0 s\bar s))} \mathord{\left/ {\vphantom {{\Gamma (D_s^ + \to \pi ^ + (2^3 P_0 s\bar s))} {\Gamma (D_s^ + \to \pi ^ + (1^3 P_0 s\bar s))}}} \right. \kern-\nulldelimiterspace} {\Gamma (D_s^ + \to \pi ^ + (1^3 P_0 s\bar s))}} \lesssim 0.05\).     

Der Zerfall des 1,5 min-Isomers Co54m

Co^54m (T _1/2=1.43 min) was produced in iron-foils by irradiation with_dE=19 MeV deuterons. The gamma ray spectrum was investigated using a NaJ(Tl) scintillation spectrometer, a coincidence circuit and a Ge(Li)-counter. There were observed three gamma rays having the following energies and intensities per Co_54m decay: 411 keV (0.97±0.07), 1130keV (0.98±0.05), 1407 keV (1.00±0.05). The directional correlation between the pairs of gamma rays were determined. These results correspond to spin and parityJ _π=2⁺ for the 1407 keV,J _π=4⁺ for the 2537 keV, andJ _π=6⁺ for the 2948 keV energy level of Fe⁵⁴. The last-mentioned level was not excited in previous scattering experiments. Our results are compatible withE=210keV andJ _π=6⁺ or 7⁺ of the isomeric state of Co^54m .     

Synthesis,Characterization and Luminescence Sensitivity with Variance in pH,DNA and BSA Binding Studies of Ru(II) Polypyridyl Complexes

Three ruthenium(II) polypyridyl complexes, [Ru(phen)₂(mip)](ClO₄)₂ (1) (phen =1,10-Phenanthroline), [Ru(bpy)₂(mip)](ClO₄)₂ (2) (bpy = 2,2’bipyridyl) and [Ru(dmb)₂(mip)](ClO₄)₂ (3) (dmb = 4, 4′-dimethyl 2, 2′-bipyridine), were synthesized with an intercalative ligand mip (2-morpholino-1H-imidazo[4,5-f][1, 10]phenanthroline) and characterized by ¹H, ¹³C–NMR, IR, UV-vis, mass spectra and elemental analysis. pH effect, ion selectivity (cations, anions) and solvent sensitivity of complexes were studied. The interaction of these complexes with DNA was performed using absorption, emission spectroscopy and viscosity measurements. The experimental results indicated that the two complexes interacted with calf thymus DNA (CT-DNA) by intercalative mode. BSA (Bovine Serum Albumin) protein binding of these complexes was studied by UV-visible and fluorescence techniques. The binding capacity of these complexes was explained theoretically by molecular docking method.     

Signature splitting in two quasiparticle rotational bands of <Superscript>180,182</Superscript>Ta

The signature splittings in K^π = 1 ⁺: 7 /2[404] _π?9 /2[624] _ν, K^π = 0^?: 9 /2[514] _π?9 /2[624] _ν bands of ¹⁸⁰Ta and K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1^?: 5 /2[402] _π?3 /2[512] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands of ¹⁸²Ta are analysed within the framework of two-quasiparticle rotor model. The phase as well as magnitude of the experimentally observed signature splitting in K^π = 1⁺ band of ¹⁸⁰Ta, which could not be explained in earlier calculations, is successfully reproduced. The conflict regarding placement of a 12 ⁺ level in K^π = 1 ⁺: 7 /2 ⁺[404] _π?9 /2 ⁺[624] _ν ground-state rotational band of ¹⁸⁰Ta is resolved and tentative nature of K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands observed in ¹⁸²Ta is confirmed. As a future prediction for experimentalists, these two-quasiparticle structures observed in ¹⁸⁰Ta and ¹⁸²Ta are extended to higher spins.     

Control of Quantum Echo and Bell State Swapping of Two Atomic Qubits in the Two-Mode Vacuum Field Environment

We investigate quantum echo control and Bell state swapping for two atomic qubits (TAQs) coupling to two-mode vacuum cavity field (TMVCF) environment via two-photon resonance. We discuss the effect of initial entanglement factor ?? and relative coupling strength R=g₁/g₂ on quantum state fidelity of TAQs, and analyze the relation between three kinds of quantum entanglement(C(ρ_a),C(ρ_f),S(ρ_a)) and quantum state fidelity, then reveal physical essence of quantum echo of TAQs. It is shown that in the identical coupling case R=1, periodic quantum echo of TAQs with π cycle is always produced, and the value of fidelity can be controlled by choosing appropriate ?? and atom-filed interaction time. In the non-identical coupling case R≠1, quantum echoes with periods of π, 2π and 4π can be formed respectively by adjusting R. The characteristics of quantum echo results from the non-Markovianity of TMVCF environment, and then we propose Bell state swapping scheme between TAQs and two-mode cavity field.     

Optical oxygen sensing materials based on trinuclear starburst ruthenium(II) complexes assembled in mesoporous silica

The preparation and oxygen sensing properties of optical materials based on two trinuclear starburst ruthenium(II) complexes: [Ru₃(bpy)₆(TMMB)]⁶⁺ (1) and [Ru₃(phen)₆(TMMB)]⁶⁺ (2) (bpy=2,2′-bpyridine, phen=1,10-phenathroline, TMMB=1,3,5-tris[2-(2′-pyridyl)benzimidazoyl]methylbenzene) assembled in two mesoporous silicate (MS) are described in this paper. The luminescence of Ru complexes/silicate assemble materials can be quenched by molecular oxygen with good sensitivity (I₀/I₁>5 for 2/MS and I₀/I₁>3 for 1/MS), indicating that trinuclear starburst Ru(II) complexes/MS systems are sensitive to oxygen molecules.     

Description of mixed symmetry states in <Superscript>96</Superscript>Ru using IBM-2

We have investigated the properties of low-lying states in ⁹⁶Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of ⁹⁶Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 4₂ ⁺ and 4₁ ⁺ states has been reproduced nicely. The calculated results show that the M1 transition strength of B(M1; 4₂ ⁺ → 4₁ ⁺) in ⁹⁶Ru can be described successfully by the IBM-2.     

<Emphasis Type="Italic">B</Emphasis> → ππ decays: Branching ratios and <Emphasis Type="Italic">CP</Emphasis> asymmetries

Theoretically motivated smallness of the penguin amplitude in B → ππ decays allows one to calculate the value of the unitarity-triangle angle α(ø ₂) with good accuracy. The relatively large branching ratio of the decay into π ⁰ π ⁰ is explained by the large value of FSI phase difference between decay amplitudes with I = 0 and I = 2.