Dinuclear System Research Articles

Family of Quasi-Isotropic MnII and Mn2II Complexes Exhibiting Slow Relaxation of the Magnetization.

Slow relaxation of magnetization has been studied for a family of mononuclear MnII complexes and one ferromagnetic dinuclear system, all of them presenting very weak anisotropy. Complexes with formula [{NiL1Mn(H2O)2(MeOH)}{NiL1}2](ClO4)2 (1), [Mn{NiL1}2](ClO4)2 (2), [Mn{NiL2}2](ClO4)2 (RR-L22-, 3RR, SS-L22-, 3SS), [Mn{NiL3}2](ClO4)2 (RR-L32-, 4RR, SS-L32-, 4SS) and (μ1,1-N3)2[Ni2Mn2(L1)2(N3)2] (5) are derived from compartmental Schiff bases, in which the NiII environment is square planar and thus diamagnetic. All of the systems have been structurally and magnetically characterized. Zero field splitting (D) values for the MnII cations have been obtained from EPR spectroscopy and NEVPT2 calculations. The slow relaxation of the magnetization for 1-5 has been studied by means of ac magnetometry and rationalized on the basis of their low, but not zero, anisotropy, providing the first example of a polynuclear MnII complex, with S = 5 ground state, exhibiting slow relaxation.

Bayesian uncertainty quantification for synthesizing superheavy elements

To improve the theoretical prediction power for synthesizing superheavy elements beyond Og, a Bayesian uncertainty quantification method is employed to evaluate the uncertainty of the calculated evaporation residue cross sections (ERCS) for the first time. The key parameters of the dinuclear system model (DNS-sysu), such as the diffusion parameter a, the damping factor Ed, and the level-density parameter ratio af/an are systematically constrained by the Bayesian analysis of recent ERCS data. One intriguing behaviour is shown that the optimal incident energies (OIE) corresponding to the largest ERCS weakly depend on the fission process. We also find that these parameters are strongly correlated and the uncertainty propagation considering the parameters independently is not reasonable. The 2σ confidence level of posterior distributions for a=0.586−0.002+0.002 fm, Ed=25.65−3.41+3.43 MeV, and af/an=1.081−0.021+0.021 are obtained. Furthermore, the confidence levels of the ERCS and OIE for synthesizing Z = 119 via the reactions Cr54+243Am, Ti50+249Bk, and V51+248Cm are predicted. This work sets the stage for future analyses to explore the OIE and reaction systems for the synthesis of superheavy elements.

Possibility of synthesizing Z = 119 superheavy nuclei with Z > 20 projectiles* *Supported by the National Natural Science Foundation of China (12175064, U2167203) and the Outstanding Youth Science Foundation of Hunan Province, China (2022JJ10031)

We employ the dinuclear system (DNS) model combined with a statistical model to calculate the evaporation residue cross sections of the reaction systems Ca + Am, Ca + Cm, and Ca + Bk. The theoretical results successfully reproduce the experimental trends in the 3n and 4n evaporation channels of these reaction systems. To synthesize the new element , we predict the evaporation residue cross sections for three reaction systems ( Cr + Am, V + Cm, and Ti + Bk) to select the most promising projectile-target combinations. We also note that the maximum cross sections predicted by our model and other methods appear to be below the detection limits of current experimental facilities, given the projectile-target combinations feasible under current experimental conditions. Therefore, synthesizing superheavy nuclei with will require improvements in beam intensity, detection techniques, and effective separation methods.

Survival probabilities of compound superheavy nuclei towards element 119

To synthesize superheavy element 119 is becoming a highly concerned issue as several experimental projects in major laboratories are being pursued. This work studied the survival probabilities of compound superheavy nuclei after multiple neutron emissions based on microscopic energy dependent fission barriers, demonstrating a significant role of triaxial deformation in decreasing the first fission barriers in the heaviest region. Together with the fusion cross sections by the dinuclear system model, the optimal energy and the residual cross section of 243Am(48Ca, 3n)288Mc are reproduced. Finally the cross sections and optimal beam energies of 54Cr+243Am and 50Ti+249Bk reactions are estimated, providing clues for the synthesis of new elements.

Coulomb interaction dependence of optimal energy to synthesize superheavy elements

The production of superheavy elements beyond Z = 118 remains unattained through both cold and hot fusion techniques, primarily due to inadequate fusion reaction optimization involving projectile–target combinations and energy. Past efforts employed various theories to optimize these combinations. In our current study, we have successfully identified optimal fusion energies for synthesizing superheavy elements, employing an advance statistical model and dinuclear system models. The establishment of optimal energy governing rule is achieved through a comprehensive examination of the Coulomb interaction parameter, enabling precise determination of the optimal energy for successful fusion reactions in synthesizing superheavy elements. The confidence level of predicting optimal energies using the present formula varies between 97% to 99%. The predicted optimal energy using the present formula for five fusion reactions such as 208Pb(50Ti,1n)257Rf, 208Pb(50Ti,2n)256Rf, 209Bi(50Ti,1n)258Db, 208Pb(58Fe,1n)265Hs, and 244Pu(48Ca,4n)288Fl were studied and are in good agreement with each other. Furthermore, we predicted the Optimal energies for fusion reactions leading to synthesize the superheavy element Z = 119 and 120. The presented empirical rule will certainly bring a revolution in the synthesis of superheavy elements.

Investigation of decay mechanisms and associated aspects of exotic Nobeliumisotopes using the Skyrme energy density formalism

Abstract Persistent theoretical and experimental attempts have been made to investigate the
heavy ion induced reactions and their subsequent decay mechanisms in superheavy mass region.
In addition, the region of transfermium elements is itself of great interest because of the neutron
/ proton shell effects. Here, we aim to study the subsequent decay mechanisms of two isotopes of
Z = 102 nucleus, i.e. 248No and 250No.
The dynamical cluster-decay model (DCM) based on Quantum Mechanical Fragmen-
tation Theory (QMFT), is employed to conduct a comprehensive analysis of compound nucleus
(CN) and non-compound nucleus (nCN) mechanisms such as fusion-fission (ff), Quasi fission (QF)
and fast fission (FF), the role of centre of mass energy (Ec.m.) and angular momentum (ℓ) for
248No and 250No isotopes. The nuclear interaction potential is obtained using the Skyrme energy
density formalism (SEDF) in the domain of GSkI force parameters. The probability of compound nucleus formation
(PCN ) is determined using a function that depends on the centre of mass energy. The lifetimes for
the fusion-fission (ff) quasi fission (QF) channels are explored.
Here, CN and nCN decay mechanisms for two isotopes of Z = 102 nobelium are studied
over the wide range of centre-of-mass (Ec.m.) by including the quadrupole deformation (β2) and
optimum orientations (θopt.) of decaying fragments. The fragmentation potential, preformation
probability, neck length parameter and reaction cross-sections are explored. Further, the calcula-
tions are done for PCN in order to identify the decay modes of 248No and 250No isotopes. The
fusion-fission lifetimes and quasi fission lifetimes are compared with the dinuclear system (DNS)
approach. The most probable fragments such as 122Sn and 128T e are observed near to the magic shell closure Z = 50 and
N = 82. The ff and qf lifetime decreases with increase in the excitation energy.

Small cross section of the synthesis of darmstadtium in the Ca48+Th232 reaction

The smallness of the cross section of evaporation residues formed in the hot fusion reaction Ca48+Th232 is analyzed by the dinuclear system model (DNS). The capture probability has been calculated by solving the dynamical equations of motion for the relative distance between the centers of mass of the DNS nuclei. Fusion of nuclei is considered as evolution of the DNS to a stable compound nucleus. The fusion probability has a bell-like shape and quasifission is one of reasons causing smallness of the yield of the evaporation residues products. Another reason is the decrease of the fission barrier for the isotopes Dm275–285 related with the shell effects in the neutron structure. The agreement of the theoretical results obtained for the yield of the evaporation residues with the experimental data measured in the Factory of Superheavy Elements of Joint Institute for Nuclear Research is well. Published by the American Physical Society 2024

Angular distribution of products in multinucleon transfer reactions* *Supported by the Guangdong Major Project of Basic and Applied Basic Research (2021B0301030006), the National Natural Science Foundation of China (12175151, 12105181, 11847235), and the Steady Support Program for Higher Education Institutions of Shenzhen (20200817005440001)

A method based on the dinuclear system (DNS) is proposed to describe the angular distribution of products in multinucleon transfer (MNT) reactions. By considering fluctuation effects, the angular distributions of reactions involving 136Xe+208Pb, 136Xe+209Bi, 86Kr+166Er, 84Kr+209Bi, and 84Kr+208Pb are examined, demonstrating good agreement with experimental data. Moreover, the double differential cross-sections ( and ) of reactions 136Xe+208Pb and 136Xe+209Bi are analyzed to explore the mechanism of angular distribution in MNT reactions. Additionally, the optimal angles for detecting N=126 isotopes are determined via an analysis on the influence of proton and neutron numbers of the projectiles on the angular distribution of the N=126 isotopic line. The results of this study can provide valuable insights for experimental detection.

Effect of the charge asymmetry and orbital angular momentum in the entrance channel on the hindrance to complete fusion

The hindrance to complete fusion is studied as a function of the charge asymmetry of colliding nuclei and orbital angular momentum of the collision. The formation and evolution of a dinuclear system (DNS) in the heavy-ion collisions at energies near the Coulomb barrier is calculated in the framework of the DNS model. The DNS evolution is considered as nucleon transfer between its fragments. The results prove that a hindrance at formation of a compound nucleus (CN) is related with the quasifission process, which is breakup of the DNS into products instead to reach the equilibrated state of the CN. The role of the angular momentum in the charge (mass) distribution of the reaction products for the given mass asymmetry of the colliding nuclei has been demonstrated. The results of this work have been compared with the measured data for the quasifission yields in the C12+Pb204 and Ca48+Er168 reactions to show the role of the mass asymmetry of the entrance channel. Published by the American Physical Society 2024

Enabling nucleophilic reactivity in molecular calcium fluoride complexes

Calcium fluoride is the ultimate source of all fluorochemicals. Current synthetic approaches rely on the use of HF, generated from naturally occurring fluorspar and sulfuric acid. Methods for constructing E–F bonds directly from CaF2 have long been frustrated by its high lattice energy, low solubility and impaired fluoride ion nucleophilicity. Little fundamental understanding of the reactivity of Ca–F moieties is available to guide methodology development; well-defined molecular species containing Ca–F bonds are extremely rare, and existing examples are strongly aggregated and evidence no nucleophilic fluoride delivery. Here, by contrast, we show that by targeting anionic systems of the type [Ln(X)2CaF]−, monomeric calcium fluoride complexes containing single Ca–F bonds can be synthesized, including via routes involving fluoride abstraction from existing C–F bonds. Comparative structural and spectroscopic studies of mono- and dinuclear systems allow us to define structure–activity relationships for E–F bond formation from molecular calcium fluorides.

Dinuclear Zn-Catalytic System as Brønsted Base and Lewis Acid for Enantioselectivity in Same Chiral Environment.

Zinc (Zn) is a crucial element with remarkable significance in organic transformations. The profusion of harmless zinc salts in the Earth's outer layer qualifies zinc as a noteworthy contender for inexpensive and eco-friendly reagents and catalysts. Recently, widely recognized uses of organo-Zn compounds in the field of organic synthesis have undergone extensive expansion toward asymmetric transformations. The ProPhenol ligand, a member of the chiral nitrogenous-crown family, exhibits the spontaneous formation of a dual-metal complex when reacted with alkyl metal (R-M) reagents, e.g., ZnEt2. The afforded Zn complex possesses two active sites, one Lewis acid and the other Brønsted base, thereby facilitating the activation of nucleophiles and electrophiles simultaneously within the same chiral pocket. In this comprehensive analysis, we provide a thorough account of the advancement and synthetic potential of these diverse catalysts in organic synthesis, while emphasizing the reactivity and selectivities, i.e., dr and ee due to the design/structure of the ligands employed.

Dinuclear group IV metal complexes based on a bis(indenyl)-(E/Z)-stilbene platform: a potential prototype of "photoswitchable" catalysts for olefin polymerization.

The preparation of dizirconium complexes based on a novel bis(indenyl)-(E/Z)-stilbene platform was explored. Negishi coupling between the in situ-generated diorganozincates obtained from the respective o/m/p-(E/Z)-dibromostilbenes and the bromo-functionalized zirconocene (η5-Cp*)(η5-2-methyl-4-bromoindenyl)ZrCl2, or, alternatively, the preparation of bis(indene)stilbene pro-ligands {o/m/p-(E/Z)-BisIndSB}H2 through Negishi coupling of the corresponding dibromostilbenes with 4-bromoindene and subsequent metallation/transmetallation with Cp*ZrCl3 or Zr(NMe2)4, allowed the preparation of a series of dinuclear complexes. These were analyzed by NMR spectroscopy and some of them by iASAP-mass spectrometry and by X-ray diffraction studies. Experimental results were compared with DFT modelling of the targeted dinuclear complexes evidencing that the (E)-complexes are more stable by 7-11 kcal mol-1 than their (Z)-analogues. Thermal, uncontrolled isomerization of (Z)- to (E)-stilbene platform was observed experimentally for some systems, in the course of their synthesis, either from the (Z)-dibromostilbene reagent or on the dinuclear complexes resulting from the Negishi coupling. Photoisomerization of the (E)- and (Z)-{BisIndSB}H2 proligands and of complexes {o-(E)-BisIndSB}(Zr(NMe2)3)2 and {m-(E)-BisIndSB}(ZrCl2Cp*)2 was investigated under a variety of conditions. It proved effective for the proligands but induced decomposition of the dizirconium complexes. Time-dependent DFT (TD-DFT) computations were performed to identify unambiguously the nature of the observed absorption bands and account for decomposition of the complexes. Preliminary ethylene/1-hexene homo- and copolymerization investigations did not evidence putative cooperativity phenomena within these dinuclear systems nor significantly differentiated behavior between the (Z)- and (E)-isomers of a given type of complex under the reaction conditions investigated.

Influence of temperature-dependent shell corrections on the prediction of production cross sections for superheavy nuclei

In the framework of the dinuclear system model, we introduce a formula accounting for temperaturedependent shell corrections to assess their influence on the fission barrier calculations and, consequently, the survival probability of excited nuclei. Our approach considers the excitation energy’s effect on the fission barrier, a crucial aspect in determining the likelihood of a nucleus persisting. Leveraging experimental data with associated errors, we constrain the region of the shell correction damping factor. Employing this refined methodology, we predict the production cross sections for the novel superheavy element (SHE) with atomic number Z=119. Specifically, at the 54Cr(243Am,3n)294119 reaction, cross sections are anticipated to range between 3-27 femtobarns (fb), while for the 51V(248Cm,3n)296119 reaction, they are projected to span 21-180 fb. These predictions offer valuable insights into the formation dynamics of this exotic superheavy element.

Exploring a Mitochondria Targeting, Dinuclear Cyclometalated Iridium (III) Complex for Image-Guided Photodynamic Therapy in Triple-Negative Breast Cancer Cells.

Photodynamic therapy (PDT) has emerged as an efficient and noninvasive treatment approach utilizing laser-triggered photosensitizers for combating cancer. Within this rapidly advancing field, iridium-based photosensitizers with their dual functionality as both imaging probes and PDT agents exhibit a potential for precise and targeted therapeutic interventions. However, most reported classes of Ir(III)-based photosensitizers comprise mononuclear iridium(III), with very few examples of dinuclear systems. Exploring the full potential of iridium-based dinuclear systems for PDT applications remains a challenge. Herein, we report a dinuclear Ir(III) complex (IRDI) along with a structurally similar monomer complex (IRMO) having 2-(2,4-difluorophenyl)pyridine and 4'-methyl-2,2'-bipyridine ligands. The comparative investigation of the mononuclear and dinuclear Ir(III) complexes showed similar absorption profiles, but the dinuclear derivative IRDI exhibited a higher photoluminescence quantum yield (Φp) of 0.70 compared to that of IRMO (Φp = 0.47). Further, IRDI showed a higher singlet oxygen generation quantum yield (Φs) of 0.49 compared to IRMO (Φs = 0.28), signifying the enhanced potential of the dinuclear derivative for image-guided photodynamic therapy. In vitro assessments indicate that IRDI shows efficient cellular uptake and significant photocytotoxicity in the triple-negative breast cancer cell line MDA-MB-231. In addition, the presence of a dual positive charge on the dinuclear system facilitates the inherent mitochondria-targeting ability without the need for a specific targeting group. Subcellular singlet oxygen generation by IRDI was confirmed using Si-DMA, and light-activated cellular apoptosis via ROS-mediated PDT was verified through various live-dead assays performed in the presence and absence of the singlet oxygen scavenger NaN3. Further, the mechanism of cell death was elucidated by an annexin V-FITC/PI flow cytometric assay and by investigating the cytochrome c release from mitochondria using Western blot analysis. Thus, the dinuclear complex designed to enhance spin-orbit coupling with minimal excitonic coupling represents a promising strategy for efficient image-guided PDT using iridium complexes.

Oxidative Addition and β-Hydride Elimination by a Macrocyclic Dinickel Complex: Observing Bimetallic Elementary Reactions.

The dinickel(I) complex Ni2 (tBu PONNOPONNO), featuring a planar macrocyclic diphosphoranide ligand tBu PONNOPONNO, offers a unique architectural platform for observing bimetallic elementary reactions. Oxidative addition reactions of alkyl halides produce dinickel(II) complexes of the type Ni2 (μ-R)(μ-X)(tBu PONNOPONNO). However, when R=Et β-hydride elimination is observed to form a dinickel monohydride, with the rate dependent on the nature of X. DFT studies suggest a new mechanism for bimetallic β-hydride elimination, where the rate dependence arises from the steric pressure imposed by the X group on the opposing trans face of the dinickel macrocycle. This work enhances understanding of bimetallic elementary reactions, particularly β-hydride elimination, which have not been well-explored for dinuclear systems.

Evaporation residue cross sections of superheavy nuclei based on optimized nuclear data* *Supported by the National Natural Science Foundation of China (12175170, 11675066)

This study proposes an optimized method for estimating atomic nucleus masses by combining the finite-range droplet model (FRDM) with the support vector machine algorithm. The optimization process significantly improves the accuracy of the FRDM by reducing the root mean square error from 0.606 to 0.253 MeV. The optimized mass data obtained from this method are then used to calculate the evaporation residue cross-sections (ERCSs) for fusion-evaporation reactions, employing the di-nuclear system model. The experimental results for the 48Ca+238U reaction are relatively well reproduced using these optimized mass data. Additionally, the study investigates the impact of mass uncertainties on fusion and survival probabilities. By considering the mass uncertainties, the ERCSs for new elements 119 and 120 are predicted based on the obtained optimized mass data.

A Dinuclear Re Complex as a Multi Talent – Photocatalysis and Electrocatalysis combined with Spectroscopy

AbstractMononuclear rhenium complexes have been widely studied as photo‐ and electrocatalysts. However, dinuclear systems with cooperative properties have rarely been investigated. On the basis of two homobimetallic rhenium complexes, we report the synthesis and characterization of two isomers and their photo‐ and electrochemical properties. By combining the respective isomer with the photosensitizer [Ir(dFppy)3] (Ir, dFppy=2‐(4,6‐difluorophenyl) pyridine)) enhanced CO2 to CO transformation could be observed and by further spectroscopic investigations the reaction mechanism could be fathomed. The observed enhanced catalytic activity compared to monometallic systems derives from the cooperative Re−Re interaction through two electron reduction on the complex (and thereby formation of an intermediate species with a Re−Re bond). Using LSV measurements the cooperative CO2 activation was also observed for one of the isomers, cisL1‐Re2Cl2, in electrocatalytic measurements. The two isomers have a somewhat lower catalytic activity than earlier prepared geometric isomers, but show better catalytic properties than their mononuclear counterpart.

Investigation on the Quasifission hindrance to synthesis 298Og

Formation of a compound nucleus and production of its evaporation residue are hindered by quasi-fission process. It reduces the evaporation residue cross section since it takes place before the target and projectile combines to form a composite nucleus. We study the quasifission barriers (Bqf) for 14 fusion reactions in the formation of superheavy element 298Og within the framework of the di-nuclear system model. In particular, the influence of entrance channel parameters on quasifission barriers has been investigated. We notice that the quasifission barriers decreases with an increase in angular momentum and fusion barrier height. We constructed semi-empirical formulae for Bqf as a function of mean fissility. The fusion reaction 48Ca+250Cf poses larger Bqf. The larger evaporation cross section is observed for this fusion reaction for 3n evaporation channel with the cross-section of 0.81pb. Similarly, a smaller evaporation cross-section of about 0.033pb is observed for 51Cr+247Pu fusion reaction for 4n evaporation channel with both projectile and target being deformed, unlike to the previous reaction with spherical projectile and deformed target.

A Nuclearity-Dependent Enantiodivergent Epoxide Opening via Enthalpy-Controlled Mononuclear and Entropy-Controlled Dinuclear (Salen)Titanium Catalysis.

A nuclearity-dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)TiIII complex and its self-assembled oxygen-bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy-controlled enantio-differentiation mode in mononuclear catalysis, whereas an entropy-controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity-distinct transition-metal complexes.

A Nuclearity‐Dependent Enantiodivergent Epoxide Opening via Enthalpy‐Controlled Mononuclear and Entropy‐Controlled Dinuclear (Salen)Titanium Catalysis

AbstractA nuclearity‐dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)TiIII complex and its self‐assembled oxygen‐bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy‐controlled enantio‐differentiation mode in mononuclear catalysis, whereas an entropy‐controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity‐distinct transition‐metal complexes.