Weak Bimetal Coupling-Assisted MN4 Catalyst for Enhanced Carbon Dioxide Reduction Reaction.

The design of multimetal catalysts holds immense significance for efficient CO2 capture and its conversion into economically valuable chemicals. Herein, heterobimetallic catalysts (MiMo)L were exploited for the CO2 reduction reactions (CO2RR) using relativistic density functional theory (DFT). The octadentate Pacman-like polypyrrolic ligand (H4L) accommodates two metal ions (Mo, W, Nd, and U) inside (Mi) and outside (Mo) its month, rendering a weak bimetal coupling-assisted MN4 catalytically active site. Adsorption reactions have access to energetically stable coordination modes of -OCO, -OOC, and -(OCO)2, where the donor atom(s) are marked in bold. Among all of the species, (UiMoo)L releases the most energy. Along CO2RR, it favors to produce CO. The high-efficiency CO2 reduction is attributed to the size matching of U with the ligand mouth and the effective manipulation of the electron density of both ligand and bimetals. The mechanism in which heterobimetals synergetically capture and reduce CO2 has been postulated. This establishes a reference in elaborating on the complicated heterogeneous catalysis.

Enrichment and immobilization of heavy metal ions from wastewater by nanocellulose/carbon dots-derived composite.

Heavy metal ions (HMIs) have been widely applied in various industries because of their excellent physicochemical properties. However, their discharging without appropriate treatment brought about serious pollution problems. So it is desirable but challenging to rapidly and completely clean up these toxic pollutants from water, especially utilizing environmentally friendly and naturally rich biomass materials. In this work, we prepared nanocellulose/carbon dots/magnesium hydroxide (CCMg) ternary composite using cotton via a simple hydrothermal method. The removal mechanism towards Cd2+ and Cu2+ was investigated using a combination of experimental techniques and density functional theory calculations. CCMg shows a good ability to remove HMIs. It is realized that the interaction between each component of CCMg and cadmium nitrate is mainly of hydrogen/dative bonds. Cadmium nitrate is preferentially enriched by the Mg(OH)2 moiety, proved by calculated thermodynamics, interfacial interactions and charges. After transformation, the cadmium carbonate precipitate is fixed on the surface by nanocellulose (NC) via chemical coupling; and of interest is that copper ion precipitates in the form of basic sulfate. Due to its high adsorption effect and simple recovery operation, CCMg is having a wide range of application prospects as a water treatment agent.

Tuning the Alkyl Chain of Nitrilotriacetamide for Selectively Extracting Trivalent Am over Eu Ions.

The successful management and safe disposal of high-level nuclear waste necessitate the efficient separation of actinides (An) from lanthanides (Ln), which has emerged as a crucial prerequisite. Mixed donor ligands incorporating both soft and hard donor atoms have garnered interest in the field of An/Ln separation and purification. One such example is nitrilotriacetamide (NTAamide) derivatives, which have demonstrated selectivity in extracting minor actinide Am(III) ions over Eu(III) ions. Nevertheless, the Am/Eu complexation behavior and selectivity remain underexplored. In the work, a comprehensive and systematic investigation has been conducted for [M(RL)(NO3)3] complexes (M = Am and Eu) utilizing relativistic density functional theory. The NTAamide ligand (RL) is substituted with various alkyl groups, namely, methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl. Thermodynamic calculations show that the alkyl chain length in NTAamide is capable of tuning the separation selectivity of Am and Eu. Moreover, the differences in calculated free energies between Am and Eu complexes are more negative for R = Bu-Oct than Me-Pr. This indicates that elongation of the alkyl chain can increase the efficiency of selective separation of Am(III) from Eu(III). Based on the quantum theory of atoms in molecules and charge decomposition analyses, it has been observed that the strength of Am-RL bonds is higher than that of Eu-RL bonds. This disparity is attributed to a greater degree of covalency in Am-RL bonds and a higher level of charge transfer from ligands to Am within complexes containing these bonds. Energies of occupied orbitals with the central N character are recognized overall lower for [Am(OctL)(NO3)3] than for [Eu(OctL)(NO3)3], indicative of stronger complexation stability of the former. These results offer valuable insights into the separation mechanism of NTAamide ligands, which can help guide the development of more powerful agents for An/Ln separation in future applications.

The coupling of graphene, graphitic carbon nitride and cellulose to fabricate zinc oxide-based sensors and their enhanced activity towards air pollutant nitrogen dioxide.

It is desirable but challenging to sense toxic nitrogen dioxide (NO2) for it has become one of the most prominent air pollutants. Zinc oxide-based gas sensors are known to detect NO2 gas efficiently, however, the sensing mechanism and involved intermediates structures remain underexplored. In the work, a series of sensitive materials, including zinc oxide (ZnO) and its composites ZnO/X [X = Cel (cellulose), CN (g-C3N4) and Gr (graphene)] have been comprehensively examined by density functional theory. It is found that ZnO favors adsorbing NO2 over ambient O2, and produces nitrate intermediates; and H2O is chemically held by zinc oxide, in line with the non-negligible impact of humidity on the sensitivity. Of the formed composites, ZnO/Gr exhibits the best NO2 gas-sensing performance, which is proved by the calculated thermodynamics and geometrical/electronic structures of reactants, intermediates and products. The interfacial interaction has been elaborated on for composites (ZnO/X) as well as their complexes (ZnO- and ZnO/X-adsorbates). The current study well explains experimental findings and opens up a way to design and unearth novel NO2 sensing materials.

Confinement effect of network-structured carbon dots/cellulose nanofiber/magnesium hydroxide for enhanced heavy metal ions capture and immobilization.

To solve pollution problem of heavy metal ions (HMIs) and recover them for sustainable development, a high-efficient-sewage treatment agent, carbon dots/cellulose nanofiber/Mg(OH)2 (CCMg), has been fabricated via a simple hydrothermal method. A variety of characterizations show that cellulose nanofiber (CNF) formed a layered-net structure. Hexagonal Mg(OH)2 flakes of about 100 nm has been attached on CNF. Carbon dots (CDs) around 10-20 nm in size were produced from CNF and distributed along CNF. The extraordinary structural feature endows CCMg with high removal performance towards HMIs. The up-taken capacities reach 992.8 and 667.3 mg g-1 for Cd2+ and Cu2+, respectively. The composite bears excellent durability in treating wastewater. Notably, the qualification of the drinking water can be satisfied while applying CCMg to handle Cu2+ wastewater. The mechanism of removal process has been proposed. Practically, Cd2+/Cu2+ ions were immobilized by CNF due to the space confinement effect. It achieves the facile separation and recovery of HMIs from the sewage, and more importantly, eliminates the risk of secondary contamination.

Uranium-Doped Zinc, Copper, and Nickel Oxides for Enhanced Catalytic Conversion of Furfural to Furfuryl Alcohol: A Relativistic DFT Study.

Transition metal oxides (TMOs) and actinide ones (AnOs) have been widely applied in catalytic reactions due to their excellent physicochemical properties. However, the reaction pathway and mechanism, especially involving TM-An heterometallic centers, remain underexplored. In this respect, relativistic density functional theory (DFT) was used to examine uranium-doped zinc, copper, and nickel oxides for their catalytic activity toward the conversion of furfural to furfuryl alcohol. A comparison was made with their undoped TMOs. It was found that the three TMOs were capable of catalyzing the reaction, where the free energies of adsorption, hydrogenation, and desorption fell between -33.93 and 45.00 kJ/mol. The uranium doping extremely strengthened the adsorption of CuO-U and NiO-U toward furfural, making hydrogenation or desorption much harder. Intriguingly, ZnO-U showed the best catalytic performance among all six catalyst candidates, as its three reaction energies were very small (-10.54-8.12 kJ/mol). The reaction process and mechanism were further addressed in terms of the geometrical, bonding, charge, and electronic properties.

Theoretical Investigation of Catalytic Water Splitting by the Arene-Anchored Actinide Complexes.

Actinide complexes, which could enable the electrocatalytic H2O reduction, are not well documented because of the fact that actinide-containing catalysts are precluded by extremely stable actinyl species. Herein, by using relativistic density functional theory calculations, the arene-anchored trivalent actinide complexes (Me,MeArO)3ArAn (marked as [AnL]) with desirable electron transport between metal and ligand arene are investigated for H2 production. The metal center is changed from Ac to Pu. Electron-spin density calculations reveal a two-electron oxidative process (involving high-valent intermediates) for complexes [AnL] (An = P-Pu) along the catalytic pathway. The electrons are provided by both the actinide metal and the arene ring of ligand. This is comparable to the previously reported uranium catalyst (Ad,MeArO)3mesU (Ad = adamantine and mes = mesitylene). From the thermodynamic and kinetic perspectives, [PaL] offers appreciably lower reaction energies for the overall catalytic cycle than other actinide complexes. Thus, the protactinium complex tends to be the most reactive for H2O reduction to produce H2 and has the advantage of its experimental accessibility.

A New Concept of Radiation Detection Based on a Fluorochromic and Piezochromic Nanocluster.

Developing materials that possess colorimetric responses to external stimuli is a promising strategy for addressing the current challenges in radiation dosimetry. Currently, colorimetric ionizing-radiation-responsive materials remain underexplored, and those with multistimuli response are rare. Herein, the integration of thorium cation and photoresponsive terpyridine carboxylate ligand gives rise to a thorium nanocluster, Th-101, which displays the second case of fluorochromic response and unprecedented piezochromic behavior among all actinide materials. The emission color of Th-101 exhibits a gradual transition from blue to cyan to green upon irradiation with accumulated dose, which renders colorimetric dosimetry of ionizing radiation based on a red-green-blue (RGB) concept. Further fabricating Th-101 into a custom-built optoelectronic device allows for on-site quantification of radiation dose with merits of ease of operation, rapid readout, and cost-effectiveness.

CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties.

Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO2, which to some extent resolves the environmental concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, [b-ONO]M≡CCH3(THF)2 ([b-ONO] = {(C6H4[C(CF3)2O])2N}3-; M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO2 cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The M≡C moiety in the complexes turns out to be the active site for the [2 + 2] cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M-C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M-O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.

Experimental and first-principle computational exploration on biomass cellulose/magnesium hydroxide composite: Local structure, interfacial interaction and antibacterial property.

The specification of the local structure and clarification of interfacial interactions of biomass composites is of tremendous significance in synthesizing novel materials and advancing their performance in various demanding applications. However, it remains challenging due to the limitations of experimental techniques, particularly for the manner that biomass composites commonly have hydrogen bonds involved in the vicinity of active sites and interfaces. Herein, the cellulose/Mg(OH)2 nanocomposite has been synthesized via a simple hydrothermal approach and examined by density functional theory (DFT) calculations. The composite exhibits a layered morphology; Mg(OH)2 flakes are around 50 nm in size and well-dispersed. They either anchor onto the cellulose surface or intercalate between layers. The specific composite structure was confirmed theoretically, in line with XRD, SEM and TEM observations. The interfacial interactions were found to be hydrogen bonding. The average adsorption energy per hydroxyl group was computed to be within -0.47 and -0.26 eV for a composite model comprising three cellulose chains and a two-layered Mg(OH)2 cluster. The combined computational/experimental results allow to postulate the antibacterial mechanism of the nanocomposite.

Van der Waals enhanced interfacial interaction in cellulose/zinc oxide nanocomposite coupled by graphitic carbon nitride.

In-depth understanding of interfacial property is the key to guiding the synthesis of biomass composites with desired performance. However, the exploration is of great challenge due to limitations of experimental techniques in locating hydrogen, requiring large/good crystals and detecting a weak interaction like van der Waals (vdW). Herein, we experimentally and computationally investigated the composite cellulose/zinc oxide/g-C3N4. Hydrothermal synthesis afforded cellulose/ZnO, and then fabricated the ternary composite by adding g-C3N4 under ultrasonic condition. Three components are found to co-exist in the composite, and the ZnO nanoparticle is attaching to cellulose and coupling with g-C3N4. These experimental findings were corroborated by relativistic DFT calculations. The interfacial coupling is elaborated as contributions of dative bonds, hydrogen bonds and vdW interaction. The vdW is increased by a factor of 4.23 in the ZnO/g-C3N4 interface. This improves electron-hole separation and offers prospective application of the composite in photocatalysis, antibacteria and gas sensing.

2D-layered Mg(OH)2 material adsorbing cellobiose via interfacial chemical coupling and its applications in handling toxic Cd2+ and UO22+ ions.

The interfacial chemistry of nanocomposite materials is of overarching importance in the separation and purification science; moreover, its understanding helps to guide synthesis, clarify structure-property relationship and unearth novel applications. However, the composites feature rather complicated local structures and hydrogen bonds are often involved in the interface and the vicinity of active sites. In this regard, density functional theory first-principle calculations associated with experimental study have synergistically examined two-dimensional (2D) magnesium hydroxide material with different layers and their adsorption toward cellobiose. Hydrogen bonds are found responsible for the interfacial coupling, which make it vital to cover the dispersion correction in the calculation. The average adsorption energy ranges from -0.29 to -0.35 eV, falling well within the range of reported hydrogen-bonding strength. On the basis of calculated structural/interfacial properties and experimental findings, the 2D Mg(OH)2 in terms of three-layer model was unraveled to substitute toxic Cd2+ ion and sorb radioactive UO22+ that is coordinated by water and hydroxyl groups. These reactions are thermodynamically feasible. The ion-exchanging mechanism was proposed for cadmium removal and the outer-sphere adsorption one for uranium extraction.

Visible colorimetric dosimetry of UV and ionizing radiations by a dual-module photochromic nanocluster.

Radiation dosimeters displaying conspicuous response of irradiance are highly desirable, owing to the growing demand of monitoring high-energy radiation and environmental exposure. Herein, we present a case of dosimetry based on a discrete nanocluster, [Th6(OH)4(O)4(H2O)6](TPC)8(HCOO)4∙4DMF∙H2O (Th-SINAP-100), by judiciously incorporating heavy Th6 polynuclear centers as radiation attenuator and organic linkers as photo-responsive sensor. Interestingly, dual-module photochromic transitions upon multiple external stimuli including UV, ß-ray, and γ-ray are integrated into this single material. The striking color change, and more significantly, the visible color transition of luminescence in response to accumulating radiation dose allow an on-site quantitative platform for naked-eye detection of ionization radiations over a broad range (1-80 kGy). Single crystal X-ray diffraction and density functional theory calculations reveal that the dual-module photochromism can be attributed to the π(TPC) → π*(TPC) intermolecular charge transfer driven by enhanced π-π stacking interaction between the adjacent TPC moieties upon irradiation.

Relativistic DFT Probe for Reaction Energies and Electronic/Bonding Properties of Polypyrrolic Hetero-Bimetallic Actinide Complexes: Effects of Uranyl endo-Oxo Functionalization.

A series of hetero-bimetallic actinide complexes of the Schiff-base polypyrrolic macrocycle (L), featuring cation-cation interactions (CCIs), were systematically investigated using relativistic density functional theory (DFT). The tetrahydrofuran (THF) solvated complex [(THF)(OUVIOUIV)(THF)(L)]2+ has high reaction free energy (ΔrG), and its replacement with electron-donating iodine promotes the reaction thermodynamics to obtain uranyl iodide [(I)(OUVIOUIV)(I)(L)]2+ (UVI-UIV). Retaining this coordination geometry, calculations have been extended to other An(IV) (An = Th, Pa, Np, Pu), i.e., for the substitution of U(IV) to obtain UVI-AnIV. As a consequence, the reaction free energy is appreciably lowered, suggesting the thermodynamic feasibility for the experimental synthesis of these bimetallic complexes. Among all UVI-AnIV, the electron-spin density and high-lying occupied orbitals of UVI-PaIV show a large extent of electron transfer from electron-rich Pa(IV) to electron-deficient U(VI), leading to a more stable UV-PaV oxidation state. Additionally, the shortest bond distance and the comparatively negative Eint of the Pa-Oendo bond suggest more positive and negative charges (Q) of Pa and endo-oxo atoms, respectively. As a result of the enhanced Pa-Oendo bond and strong CCI in UVI-PaIV along with the corresponding lowest reaction free energy among all of the optimized complexes, uranyl species is a better candidate for the experimental synthesis in the ultimate context of environmental remediation.

Productive preparation of N-doped carbon dots from sodium lignosulfonate/melamine formaldehyde foam and its fluorescence detection of trivalent iron ions.

Due to its good properties and low cost, melamine formaldehyde foam has been widely used in cars, furniture and construction. However, how to recycle the spent foam still remains challenging for scientists. In this work, a new method was designed to prepare N-doped carbon dot (NCD) materials by calcining sodium lignin sulfonate/melamine formaldehyde foam (LSMF) via one step. TEM, IR and XPS were used to characterize the structure and morphology of newly-synthesized NCDs. It is shown that carbon powder is obtainable by calcination. Since it derives from the collapse of the foam structure of LSMF, the carbon powder can almost completely dissolve in deionized water. The particle size ranges from 5 to 20 nm. The fluorescence properties of NCDs were studied by fluorescence spectroscopy. A strong emission has been detected at 580 nm with the quantum yield of 2.94%. When applying NCDs to detect various metal ions, there is a significant fluorescence quenching effect and good selectivity for Fe3+. The mechanism has been hypothesised. Our study provides a method for productive preparation of NCDs from spent foam.

Main-Group Metals Stabilized Polypyrrolic Uranyl(V) Complexes via Cation-Cation Interaction with the Uranyl exo-Oxo Atom: A Relativistic Density Functional Theory Study.

To explore the innovative uranyl(V) complexes by deeply understanding their coordination stability, relativistic density functional theory calculations have been performed to investigate the experimentally reported [(py)(R2AlOUVO)(py)(H2L)] [R = Me (1), iBu (2)] and [{(py)3MOUVO}(py)(H2L)] [M = Li (3), Na (4), K (5)] and their uranyl(VI) counterparts. Structural and topological analyses along with transformation-reaction energies and redox potentials were systematically studied. Geometrical and quantum theory of atoms in molecules analyses implied a linear U-Oexo-M feature in 1-3 and a bent one in 4 and 5. The calculated free energies (ΔrG) of reactions transforming 1/2 into 3/4/5 confirmed a higher stability of the latter ones, which were further corroborated by their reduction potentials (E0). The E0 value of 5 versus uranyl(VI) is close to its experimental value, particularly in solvation with spin-orbit coupling. The highest occupied and lowest unoccupied molecular orbitals of uranyl(V) and uranyl(VI) have predominant U(5fδ) character. Compared to mononuclear uranyl(VI), the coordination of aluminum and alkali metals to uranyl exo-oxo significantly contributes to the stabilization of uranyl(V) by altering the E0 value from -1.59 to -0.85, -0.91, -1.33, -1.50, and -1.46 V, respectively. The calculation results show a more positive E0 than that of the precursor 6VI/6 without exo-oxo coordination. The calculated E0 values of 3-5 are certainly more negative than those of 1 and 2. The alkali metals were found to activate U═O bonds more easily/readily than aluminum by coordination to the exo-oxo atom. In brief, the uranyl exo-oxo cation-cation-interaction enhanced the reduction ability from its uranyl(VI) analogue and raised the stability of the UV center.

Actinyl-Modified g-C3N4 as CO2 Activation Materials for Chemical Conversion and Environmental Remedy via an Artificial Photosynthetic Route.

With the reported CO2 activation for the oxidation of benzene to phenol (-ENE → -OL) by the graphitic carbon nitride g-C3N4 (CN) via an artificial photosynthetic route as inspiration, high-valent actinyls (AnmO2)n+ (An = U, Np, Pu; m = VI, V; n = 2, 1) have been introduced for its further modification. Our calculations indicate thermodynamic spontaneity in the feasibility of g-C3N4-(AnmO2)n+ (CN-Anm) formation. The magnificent structural and electronic properties of CN-Anm are utilized for CO2 activation in terms of the rarely studied -ENE → -OL conversion. The calculated free energies show that most steps of the catalytic cycle are favored by CN-Anm complexes. The first step (carbamate formation) is slightly endothermic in all cases, where CN-U is 0.51 eV higher than CN and CN-Pu is -0.01 eV lower. All benzene addition reactions release energy, with that for CN-U being the lowest. The phenolate formation is favored by some actinyl complexes over CN, and CN-U is only 0.23 eV higher. The phenol release (resulting in formamide complexes) and CO desorption are exothermic for all CN-Anm. The overall process suggests the improved catalytic performance of actinyl-modified CN materials, and the slightly depleted uranyl-carbon nitride could be one of the promising catalysts.

Fabrication of dually N/S-doped carbon from biomass lignin: Porous architecture and high-rate performance as supercapacitor.

The lignin amine (LA) was exploited to prepare dually N/S-doped carbon (NSC), which was endowed with intriguing porous structure by Fe3O4 template. N and S elements, originating from LA, are doped into the materials. NSC possesses diverse-scale 3D pores. The macropores are made by Fe3O4, which facilitate to produce meso and micro pores on their walls by KOH activation. The sample prepared at 700 °C (NSC-700) is found to have the largest specific surface area (1199 cm2 g-1) and specific capacity (241 F g-1 at current density of 1 A g-1). Its capacity is 260% as high as that of lignin amine carbon (LAC) prepared without adding Fe3O4. Excellent rate performance is unraveled because of possessing 82% specific capacity at 20 A g-1 and 27.2 Wh kg-1 energy density at 10000 W kg-1 power density. Moreover, the specific capacity maintains 95.0% after 3000 cycles, indicating good electrochemical stability. The good electrical performance of NSC-700 is attributed to its interesting electronic properties that are induced by special pore structure. Because of having merits such as high rate performance, long life, large specific capacity and low cost, our NSC is anticipated to be a promising capacitor as electrode material.

Occurrence of polyoxouranium motifs in uranyl organic networks constructed by using silicon-centered carboxylate linkers: structures, spectroscopy and computation.

Four novel polyoxouranium-based uranyl carboxylates have been constructed by using a combination of three silicon-centered carboxylate ligands and polyoxouranium building blocks. Interesting oligomerization of the uranyl groups from three types of tetrameric units in 1 and 2 to octameric [(UO2)8(µ3-OH)6(µ2-OH)2(H2O)4]8+ in 3 and ultimately infinite polyoxouranium chains in 4 was observed. The 3D structure of 2 contains two different linear tetramers, whose structures are totally different from seven types of tetranuclear motifs previously observed in uranyl carboxylates. Compound 3 displays a rare octanuclear polyoxouranium brick; it is fabricated by the association of eight uranyl units in pentagonal-bipyramidal geometry that involves the edge-sharing polyhedral connection mode, which are further linked by four isolated UO7 pentagonal bipyramids to create a complicated 3D framework. These newly synthesized hybrid materials were extensively characterized by single crystal analysis, thermogravimetric analysis (TG) and different spectroscopic techniques (IR, UV-vis, and luminescence spectroscopy), which show well-resolved characteristic "five-finger" emission of the uranyl ions under excitation at 420 nm. Relativistic density functional theory (DFT) was used to explore five model compounds that theoretically simulate experimental real compounds. Experimental spectroscopy was rationalized by electronic-structure analysis.

Redox and structural properties of accessible actinide(ii) metallocalixarenes (Ac to Pu): a relativistic DFT study.

The redox properties of actinides play a significant role in manipulating organometallic chemistry and energy/environment science, for being involved in fundamental concepts (oxidation state, bonding and reactivity), nuclear fuel cycles and contamination remediation. Herein, a series of trans-calix[2]pyrrole[2]benzene (H2L2) actinide complexes (An = Ac-Pu, and oxidation states of +II and +III) have been studied by relativistic density functional theory. Reduction potentials (E 0) of [AnL2]+/[AnL2] were computed within -2.45 and -1.64 V versus Fc+/Fc in THF, comparable to experimental values of -2.50 V for [UL1e]/[UL1e]- (H3L1e = (Ad,MeArOH)3mesitylene and Ad = adamantyl) and -2.35 V for [U(CpiPr)2]+/[U(CpiPr)2] (CpiPr = C5 iPr5). The E 0 values show an overall increasing trend from Ac to Pu but a break point at Np being lower than adjacent elements. The arene/actinide mixed reduction mechanism is proposed, showing arenes predominant in Ac-Pa complexes but diverting to metal-centered domination in U-Pu ones. Besides being consistent with previously reported those of AnIII/AnII couples, the changing trend of our reduction potentials is corroborated by geometric data, topological analysis of bonds and electronic structures as well as additional calculations on actinide complexes ligated by tris(alkyloxide)arene, silyl-cyclopentadiene and octadentate Schiff-base polypyrrole in terms of electron affinity. The regularity would help to explore synthesis and property of novel actinide(ii) complex.