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A series of diindeno[2,1-b:2',1'-h]biphenylenes with open-shell singlet ground states and interesting properties were prepared. The studied compounds consist of p-quinodimethane moieties, which suffer from geometric perturbation with bond angles of around 90°. The substituent effects on structural parameters, local aromaticity, and properties were systematically explored.

A dimeric dithiolate-bridged species, [Fe(NO)(PS2)]

A new tridentate and rigid ligand containing S,N-hetero donor, the 1H-1,8-naphthyridine-2-thione (Hnpt), is designed and developed to build up the first homonuclear nickel string supported by the m...

Carbon monoxide (CO) plays an important role in signaling in cells, making its use as a therapeutic tool highly intriguing. Reduced burst emissions are important to avoid the cytotoxicity and tissue damage caused by CO. Here, we developed a stable diiron carbonyl [FeFe] hydrogenase agent that enables prolonged CO release activity (half-life of over 9 h) in cells. The integrated analysis allowed the identification of the key intermediate sites and CO accumulations with subcellular resolution. We observed that the [FeFe]

Grafting of organic groups on the surface of metal-oxide clusters greatly enhances the Li+ ion capacity. Triply organo-substituted polyoxometalates (RN-POMs) display an excellent Li+ ion capacity (...

We report the syntheses, structures, magnetic and electrochemical properties of MRhRh metal cores helically wrapped by four dpa− (2,2′-dipyridylamide) ligands. We successfully synthesized the precursor Rh2(dpa)4 (1) in high yield and characterized its structure including its oxidized form (1+) which facilitated the syntheses of this series of metal springs. By the reactions of (1) and the metal ions of group 7 to group 12 (M = Mn(2), Fe(3), Co(4), Ni(5), Cu(6), Pd(8), Pt(9), Ru(10), Ir(11) and Rh(12)), ten MRh2(dpa)4Cl2 complexes were successfully isolated. Note that Cd(7) can only be obtained by the one-pot method. The yield of Rh3(dpa)4Cl2 (12) is also improved by this stepwise method. The oxidized complexes [MRh2(dpa)4Cl2](PF6) (M: Ni(5+), Ru(10+), Ir(11+)) are also synthesized for the studies of electronic structures and magnetic properties. The X-ray diffraction technique is applied to characterize all of their structures. The results of these structural, magnetic, and electrochemical studies provide us with in-depth knowledge and comprehensive insight into metal–metal bonds and interactions for this new series of metal strings. In particular, four metal–metal bonds with short distances are found: Pd–Rh (2.372(13) A), Pt–Rh (2.385(7) A), Ru–Rh (2.33(3) A), and Ir–Rh (2.373(5) A). The remaining ones show no evidence of covalent metal bonds judging from their metal–metal distances, magnetic behaviour, and redox couples in electrochemical analysis. Besides, two unique tetranuclear MRhRhM(dpa)4X2 (M: Cu+(13) and Ag+(14)) complexes with a Rh2(dpa)4 framework are developed. Four metals are aligned linearly. This coordination mode of metal strings provides a unique synthetic route for constructing longer metal chains from a smaller number of dentate ligands.

Nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) are complementary tools for studying the vibrational and geometric structures of specific isotopically labeled molecular systems. Here we apply NRVS and DFT to characterize the trans-[57Fe(η2-H2)(H)(dppe)2][BPh4] [dppe = 1,2-bis(diphenylphosphino)ethane] complex. Heretofore, most NRVS observations have centered on the spectral region below 1000 cm-1, where the 57Fe signal is strongest. In this work, we show that state-of-the-art synchrotron facilities can extend the observable region to 2000 cm-1 and likely beyond, in measurements that require less than 1 day. The 57Fe-H stretch was revealed at 1915 cm-1, along with the asymmetric 57Fe-H2 stretch at 1774 cm-1. For a small fraction of the H2-dissociated product, the 57Fe-H stretch was detected at 1956 cm-1. The unique sensitivity to 57Fe motion and the isolated nature of the Fe-H/H2 stretching modes enabled NRVS to quantitatively analyze the sample composition.

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}6 complexes (the Enemark-Felthan notation), [Fe(NO)(TMSPS2)(TMSPS2H)] (1, TMSPS2H2 = 2,2'-dimercapto-3,3'-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe(TMSPS2)(TMSPS2CH3)] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH···ON-Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (νNO) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of νNO from 1833 (1) to 1823 cm-1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe(TMSPS2)2] (4). In contrast with the common acid-base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [MnIII(TMSPS3)(DABCO)] (TMSPS3H3 = (2,2'2''-trimercapto-3,3',3''-tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)(TMSPS3)]- (5-) with a {MnNO}6 electronic configuration, whereas [MnIII(TMSPS3)(DABCO)] reacts with NO gas for the formation of a {MnNO}5 species, [Mn(NO)(TMSPS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [MnIII(TMSPS3)(DABCO)].

Five heterometallic pentanuclear metal strings were prepared by stepwise synthesis from two to three and four kinds of metals aligned in one chain. In particular, NiPtCo2Pd(tpda)4Cl2 (5) possesses four different metals, and the SQUID measurement shows that Ni2+ is the only magnetically active center. Besides, the shortest Co(ii)-Co(ii) single bond (2.105(9) A), so far, is reported.

Hexa-peri-hexabenzocoronene (HBC) derivatives tend to form discotic columnar liquid crystalline (DCLC) phases capable of charge transport and anisotropic photoresponses. However, their noncovalentl...

A series of diindeno[2,1

A diiron complex containing a bridging hydride and a protonated terminal thiolate of the form [(μ,κ2-bdtH)(μ-PPh2)(μ-H)Fe2(CO)5]+ has been investigated through 57Fe nuclear resonance vibrational spectroscopy (NRVS) and interpreted using density functional theory (DFT) calculations. We report the Fe–μH–Fe wagging mode, and indications for Fe–μD stretching vibrations in the D-isotopologue, observed by 57Fe-NRVS. Our combined approach demonstrates an asymmetric sharing of the hydride between the two iron sites that yields two nondegenerate Fe–μH/D stretching vibrations. The studied complex provides an important model relevant to biological hydrogen catalysis intermediates. The complex mimics proposals for the binuclear metal sites in [FeFe] and [NiFe] hydrogenases. It is also an appealing prototype for the ‘Janus intermediate’ of nitrogenase, which has been proposed to contain two bridging Fe–H–Fe hydrides and two protonated sulfurs at the FeMo-cofactor. The significance of observing indirect effects of the bridging hydride, as well as obstacles in its direct observation, is discussed in the context of biological hydrogen intermediates., Fe–H–Fe bridging iron hydrides in model systems and metalloenzymes: benefits and challenges in revealing their vibrational signatures using NRVS spectroscopy and DFT calculations.

Nine polymeric and discrete complexes including a couple of genuine supramolecular isomers have been successfully prepared from divalent transition metal ions (Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) and unsymmetrical quasi semirigid pyridinecarboxylate isomers, InMe-n-py (n = 2, 3, 4). Structural analyses reveal that the unsymmetrical quasi semirigid ligands manage the metal(II) ions to form discrete (0D) armed metallocycle and dinuclear paddlewheel molecule, 1D ribbon, simple 2D rhombus (4,4) grid, 2D chiral wavy square (4,4) grid, and 2D double-edged layer with decorated (4,4) topology. Noncovalent hydrogen bonds and aromatic stacking interactions are found to be accessorial secondary interactions that are helpful for the extension and stabilization of the final inorganic−organic hybrid supramolecular networks of metal(II) complexes. Positional isomerism and conformational diversity of the unsymmetrical quasi semirigid ligands and the coordination preference of divalent metal ions play key roles in dominating structure variation and network complexity. Thermogravimetric analysis of mass loss showed that the frameworks of these complexes are thermally stable up to ca. 220–400 °C. Variable-temperature, solid-state magnetic susceptibility studies suggest that Mn(II) complexes 1 and 2 exhibit antiferromagnetic exchange coupling.

Diindeno-fused dibenzo[a,h]anthracene 6 and diindeno-fused dibenzo[c,l]chrysene 9 contain the key moieties 1,4-quinodipropene (1,4-QDP) and 2,6-naphthoquinodipropene (2,6-NQDP), respectively, and they both have an open-shell singlet ground state. The latter compound exhibits a strong biradical character and interesting properties, including a low ΔET-S (2.44 kcal mol-1 ), a small HOMO-LUMO gap (1.06 eV), a wide photoabsorption range (250-1172 nm), and a large two-photon absorption cross-section (σ=1342±56 GM). This work verifies that 6 has a slightly larger HOMO-LUMO gap and ΔET-S than its helical isomer diindeno[2,1-f:1',2'-j]picene (DIP), but is a much stronger two-photon absorber, verifying the important effect of geometry on the photophysical properties.

International audience; The synthesis, structural characteristics, and photophysical properties of luminescent Cu-rich bimetallic superatomic clusters [Au@Cu-12((S2CNPr2)-Pr-n)(6)(C CPh)(4)](+) (1a(+)), [Au@Cu-12{S2P(OR)(2)}(6)(C CPh)(4)](+) (2(+)), (2a(+) = Pr-i; 2b(+) = Pr-n), [Au@Cu-12{S2P(C2H4Ph)(2)}(6)(C CPh)(4)](+) (2c(+)), and [Ag@Cu-12{S2P((OPr)-Pr-n)(2)}(6)(C CPh)(4)](+) (3(+)) were studied. Compositionally uniform clusters 1(+)-3(+) were isolated from the reaction of dithiolato-stabilized, polyhydrido copper clusters with phenylacetylene in the presence of heterometal salts. By using X-ray diffraction, the structures of 1a(+), 2a(+), 2b(+), and 3(+) were able to be determined. ESI-mass spectrometry and elemental analysis confirmed their compositions and purity. The structural characteristics of these clusters are similar with respect to displaying gold (or silver)-centered Cu-12 cuboctahedra surrounded by six dithiocarbamate/dithiophosph(in)ate and four alkynyl ligands. The doping of Au and Ag atoms into the polyhydrido copper nanoclusters significantly enhances their PL quantum yields from Ag@Cu-12 (0.58%) to Au@Cu-12 (55%) at ambient temperature in solution. In addition, the electrochemical properties of the new alloys were investigated by cyclic voltammetry.

Nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) are complementary tools for studying the vibrational and geometric structure of specific isotopically-labeled molecular systems. Here we apply NRVS and DFT to characterize the trans-[(57)Fe(η(2)-H(2))(H)(dppe)(2)][BPh(4)] complex. Heretofore, most NRVS observations have centered on the spectral region below 1000 cm(−1) where the (57)Fe signal is strongest. In this work, we show that state-of-the-art synchrotron facilities can extend the observable region to 2000 cm(−1) and likely beyond, in measurements that require less than one day. The (57)Fe–H stretch was revealed at 1915 cm(−1), along with the asymmetric (57)Fe–H(2) stretch at 1774 cm(−1). For a small fraction of the H(2)-dissociated product, the (57)Fe–H stretch was detected at 1956 cm(−1). The unique sensitivity to (57)Fe motion and the isolated nature of the Fe–H/H(2) stretching modes enabled NRVS to quantitatively analyze the sample composition.

We report the syntheses, structures, magnetic and electrochemical properties of MRhRh metal cores helically wrapped by four dpa- (2,2'-dipyridylamide) ligands. We successfully synthesized the precursor Rh2(dpa)4 (1) in high yield and characterized its structure including its oxidized form (1+) which facilitated the syntheses of this series of metal springs. By the reactions of (1) and the metal ions of group 7 to group 12 (M = Mn(2), Fe(3), Co(4), Ni(5), Cu(6), Pd(8), Pt(9), Ru(10), Ir(11) and Rh(12)), ten MRh2(dpa)4Cl2 complexes were successfully isolated. Note that Cd(7) can only be obtained by the one-pot method. The yield of Rh3(dpa)4Cl2 (12) is also improved by this stepwise method. The oxidized complexes [MRh2(dpa)4Cl2](PF6) (M: Ni(5+), Ru(10+), Ir(11+)) are also synthesized for the studies of electronic structures and magnetic properties. The X-ray diffraction technique is applied to characterize all of their structures. The results of these structural, magnetic, and electrochemical studies provide us with in-depth knowledge and comprehensive insight into metal-metal bonds and interactions for this new series of metal strings. In particular, four metal-metal bonds with short distances are found: Pd-Rh (2.372(13) Å), Pt-Rh (2.385(7) Å), Ru-Rh (2.33(3) Å), and Ir-Rh (2.373(5) Å). The remaining ones show no evidence of covalent metal bonds judging from their metal-metal distances, magnetic behaviour, and redox couples in electrochemical analysis. Besides, two unique tetranuclear MRhRhM(dpa)4X2 (M: Cu+(13) and Ag+(14)) complexes with a Rh2(dpa)4 framework are developed. Four metals are aligned linearly. This coordination mode of metal strings provides a unique synthetic route for constructing longer metal chains from a smaller number of dentate ligands.

Five heterometallic pentanuclear metal strings were prepared by stepwise synthesis from two to three and four kinds of metals aligned in one chain. In particular, NiPtCo2Pd(tpda)4Cl2 (5) possesses four different metals, and the SQUID measurement shows that Ni2+ is the only magnetically active center. Besides, the shortest Co(ii)-Co(ii) single bond (2.105(9) Å), so far, is reported.

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}

A series of high and low symmetry hexa-peri-hexabenzocoronene derivatives, compounds 1–3, was successfully synthesized and applied for corrosion resistance on iron surfaces. In particular, compound 1 exhibited excellent anti-corrosion behavior, as demonstrated by electrochemical impedance spectroscopy (EIS) and contact angle (CA) measurements. A high resistance of 186.7 kΩ/cm2 and excellent hydrophobicity (CA ∼143.9°) with brine solution were obtained. The discotic columnar liquid crystals (DCLCs) coating on the iron surface provide protection under various environments, including exposure to air and solutions with different pH values. This characteristic is attributed to the excellent hydrophobicity and self-healing properties of discotic columnar liquid crystals.

Atomically precise Cu-rich bimetallic superatom clusters have been synthesized by adopting a galvanic exchange strategy. [Cu@Cu12 (S2 CNn Bu2 )6 (C≡CPh)4 ][CuCl2 ] (1) was used as a template to generate compositionally uniform clusters [M@Cu12 (S2 CNn Bu2 )6 (C≡CPh)4 ][CuCl2 ], where M=Ag (2), Au (3). Structures of 1, 2 and 3 were determined by single crystal X-ray diffraction and the results were supported by ESI-MS. The anatomies of clusters 1-3 are very similar, with a centred cuboctahedral cationic core that is surrounded by six di-butyldithiocarbamate (dtc) and four phenylacetylide ligands. The doped Ag and Au atoms were found to preferentially occupy the centre of the 13-atom cuboctahedral core. Experimental and theoretical analyses of the synthesized clusters revealed that both Ag and Au doping result in significant changes in cluster stability, optical characteristics and enhancement in luminescence properties.

International audience; We have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu{SCNR}{C[triple bond, length as m-dash]CR'}](PF), (where : R = Bu, R' = COMe; : R = Bu, R' = COEt; : R = Pr, R' = COEt; : R = Pr, R' = 3,5-(CF)CH); [Cu(μ-S){SCNR}{C[triple bond, length as m-dash]CR'}], ; [Cu(μ-Cl){SCNR}{C[triple bond, length as m-dash]CR'}](PF), (where : R = Bu, R' = Ph); [Cu(μ-Br){SCN Bu}{C[triple bond, length as m-dash]CPh}](PF), ; and [Cu(μ-Cl)(μ-Cl){SCN Bu}{C[triple bond, length as m-dash]CCOMe}]. Cluster is the first structurally characterized copper cluster having a Cu centered cuboctahedral arrangement, a miniature of the bulk copper structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms was confirmed by XANES. Inverse coordination clusters are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu) in nanoclusters can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br ≈ Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS, H, C NMR, IR, UV-visible, emission spectroscopy, and the structures , , and were established by X-ray diffraction analysis.

The CoRu2(dpa)4Cl2 (1) (dpa: 2,2′-dipyridylamide) is synthesized by the reaction of Ru2(OAc)4Cl and Co3(dpa)4Cl2. By mixing 1 with NH3, Co2+ can be removed and result in the formation of unique binuclear complex 4,0-Ru2(dpa)4Cl (2) featuring one coordination pocket supported by free pyridine groups. Hence, this complex can act as an outstanding precursor for the formation of heterotrimetallic chains with MRu2 cores. A series of M–Ru25+ complexes (M = Co2+ (3), Ag+ (4), Mn2+ (5), Fe2+ (6), Zn2+ (7), Cd2+ (8), Pd2+ (9), Rh2+ (10), and Ir2+ (11)) were prepared and isolated, representing the most complete series of heterotrimetallic chains to date. All these metal string complexes are in a linear trimetallic framework helically wrapped by four dpa− ligands, characterized by X-ray diffraction measurements. The bending of the trinuclear metal cores in RhRu2 (10) and IrRu2 (11) (∠Ru–Ru–Rh: 167.58° and ∠Ru–Ru–Ir: 167.61°) indicates that a heterometallic metal–metal bonds (Ru–Rh; Ru–Ir) are generated. The studies from DFT calculation of 10 and 11 coincide with the experimental results. Furthermore, the M⋯Ru25+ distances are regulated by the factors including the bonding force of M–pyridyl and the static repulsion between M and Ru25+ unit. Interestingly, the trend for these distances is in line with that observed in trans-M(py)4Cl2 complexes.

We show that synthetic [FeFe]-hydrogenase mimics embedded within liposomes can be immobilized on high-surface-area carbon blacks for the construction of a three-dimensional (3D) electrode for H2 production in neutral aqueous media. In this design, the bilayer vesicles (liposomes) serve as a water-insoluble electrocatalyst carrier, facilitating access of the embedded catalysts to aqueous solution. Fast electron-transfer rates and low overpotentials are achieved compared to water-soluble catalysts. The electron-transfer rate constant between the embedded [(μ-bdt)Fe2(CO)6] (bdt=1,2-benzenedithiolate; 1) and the electrode is estimated to be 1.33±0.15 s−1. Immobilized [(μ,κ2-bdt-Me)(μ-PPh2)Fe2(CO)5] (Me=methyl; 3) is able to catalyze H2 production in Na2SO4(aq) solution (pH=7) at −1.06 V (vs. SHE) with an overpotential of approximately 400 mV. The reported general method for the construction of 3D electrodes paves the way to potential applications of molecular catalysts in energy devices.

The synthesis, via a co-reduction method, of the first Pd-containing silver-rich 21-metal-atom nanocluster passivated by dithiolates, [PdAg20{S2P(OnPr)2}12] (1), is reported. 1 is an 8 electron superatom isoelectronic to [Ag21{S2P(OiPr)2}12]+. The doping of Pd in 1 leads to its high stability against degradation in solution and shows red emission in MeTHF at 77 K. In addition, we report the X-ray crystal structure of a multi-palladium doped silver nanocluster, [Pd6Ag14(S){S2P(OnPr)2}12] (2), for the first time. Its X-ray structure exhibits a sulfide-centered Pd6Ag2 rhombohedron surrounded by twelve additional silver atoms with S6 symmetry. The XPS study and DFT calculations indicate that 2 contains Pd(0) and Ag(i) metals. A significant decrease in the electrochemical gap was observed in the SWVs of 2.

The structurally precise Cu-rich hydride nanoclusters [PdCu14 H2 (dtc/dtp)6 (C≡CPh)6 ] (dtc: di-butyldithiocarbamate (1); dtp: di-isopropyl dithiophosphate (2)) were synthesized from the reaction of polyhydrido copper clusters [Cu28 H15 (S2 CNn Bu2 )12 ]+ or [Cu20 H11 {S2 P(Oi Pr)2 }9 ] with phenyl acetylene in the presence of Pd(PPh3 )2 Cl2 . Their structures and compositions were determined by single-crystal X-ray diffraction and the results supported by ESI-mass spectrometry. Hydride positions in 1 were confirmed by single-crystal neutron diffraction. Each hydride is connected to one Pd0 and four CuI atoms in slightly distorted trigonalbipyramidal geometry. The anatomies of clusters 1 and 2 are very similar and DFT calculations allow rationalizing the interactions between the encapsulated [PdH2 ]2- unit and its Cu14 bicapped icosahedral cage. As a result, Pd has the highest coordination number (14) so far recorded.

Dioxygen activation by FeII thiolate complexes is relatively rare in biological and chemical systems because the sulfur site is at least as vulnerable as the iron site to oxidative modification. O2 activation by FeII-SR complexes with thiolate bound trans to the O2 binding site generally affords the FeIV[double bond, length as m-dash]O intermediate and oxidized thiolate. On the other hand, O2 activation by Fe(ii)-SR complexes with thiolate bound cis to the O2 binding site generates FeIII-O-FeIII or S-oxygenated complexes. The postulated FeIV[double bond, length as m-dash]O intermediate has only been identified in isopenicillin N synthase recently. We demonstrated here that O2 activation by a dinuclear FeII thiolate-rich complex produces a mononuclear FeIII complex and water with a supply of electron donors. The thiolate is bound cis to the postulated dioxygen binding site, and no FeIII-O-FeIII or S-oxygenated complex was observed. Although we have not detected the transient intermediate by spectroscopic measurements, the FeIV[double bond, length as m-dash]O intermediate is suggested to exist by theoretical calculation, and P-oxidation and hydride-transfer experiments. In addition, an unprecedented FeIII-O2-FeIII complex supported by thiolates was observed during the reaction by using a coldspray ionization time-of-flight mass (CSI-TOF MS) instrument. This is also supported by low-temperature UV-vis measurements. The intramolecular NHO[double bond, length as m-dash]FeIV hydrogen bonding, calculated by DFT, probably fine tunes the O2-activation process for intramolecular hydrogen abstraction, avoiding the S-oxygenation at cis-thiolate.

The first structurally characterized copper cluster with a Cu13 centered cuboctahedral arrangement, a model of the bulk copper fcc structure, was observed in [Cu13(S2CNnBu2)6(C≡CR)4](PF6) (R=C(O)OMe, C6H4F) nanoclusters. Four of the eight triangular faces of the cuboctahedron are capped by acetylide groups in μ3 fashion, and each of the six square faces is bridged by a dithiolate ligand in μ2,μ2 fashion, which leads to a truncated tetrahedron of twelve sulfur atoms. DFT calculations are fully consistent with the description of these Cu13 clusters as two-electron superatoms, that is, a [Cu13]11+ core passivated by ten monoanionic ligands, with an a1 HOMO containing two 1S jellium electrons.

Reactants slow diffusion of Ag(I) salts with 3,4′-bis(pyridylmethyl)amine (3,4′-bpma), an unsymmetric bis-pyridyl ligand equipped with a non-innocent amine backbone, afforded polymeric coordination adducts 1–5 having a general formula {[Ag(3,4′-bpma)(solv)]X}n (solv = H2O, CH3OH, and none; X= CF3CO2–, BF4–, ClO4–, CF3SO3–, and SbF6–). Single-crystal X-ray diffraction (SCXRD) analyses reveal that colorless crystals of Ag(I) coordination polymers (CPs) 1–5 have very similar one-dimensional (1D) non-flat chain structures, which are preferentially depicted as a “zipper-like” rather than a ladder-like or a double-stranded chain topologies. The 3,4′-bpma ligand in these Ag(I) CPs displays a μ3-bridging mode with a gauche–trans (1,4, and 5) and a trans–trans (2 and 3) conformations. Noteworthy, anions do not show strong influence on structural modulation of Ag(I) CPs in the solid state, but really affect CP conformations and packing fashions, indicative of a ligand-dominated assembly process for such a Ag(I)–3,4′-bpma system. Thermal stabilities and solid-state photoluminescence properties of crystalline materials 1–5 were investigated.

Both the reduced and the protonated states of diiron dithiolate complexes, which are key intermediate species for the electrocatalytic production of hydrogen, have been spectroscopically and theoretically investigated in this study. Five important states in the process of H2 evolution have been characterized. In the presence of a superacid, protonation occurs onto the Fe–Fe vector of [(μ-xdt)Fe2(CO)6] (xdt: pdt, 1,3-propanedithiolate; edt, 1,2-ethanedithiolate; bdt, 1,2-benzenedithiolate) to yield the cationic μ-H species (the C state). A single reduction at 193 K leads to the neutral species (the CE state), with similar structures for the pdt and edt bridgeheads. The CE species of the bdt analogue is unstable under the same conditions. An open structure resulting from the rupture of one Fe–S bond is suggested by DFT calculations. Subsequently, a second reduction induces a dramatic structural rearrangement in which the CEE state possesses an open structure exhibiting a μ-H and a μ-CO group. Protonation on...

International audience; Herein we report a crystal structure of [Au0.5Ag0.5@Ag20{S2P(OiPr)2}12](PF6) [Cl@Ag8{S2P(OiPr)2}6](PF6) (1), which compositions were supported by positive-mode electrospray ionization mass spectrometry. The structural elucidation indicates that the encapsulated atom of an Ag13 the entered icosahedron can be replaced by a gold atom. Surprisingly, the capping Ag atoms on the surface of an icosahedron in 1 reveal a different arrangement from the previously reported [Ag21{S2P(OiPr)2}12](PF6) of C3 symmetry. Besides, the preference for the central silver atom being oxidized by Au(I) is rationalized by the DFT calculations on three different computed [AuAg20{S2PH2}12]+ models having C1, C3, and T symmetry, respectively.

The intrinsic catalytic property of a Fe–S complex toward H2 evolution was investigated in a wide range of acids. The title complex exhibited catalytic events at −1.16 and −1.57 V (vs Fc+/Fc) in the presence of trifluoromethanesulfonic acid (HOTf) and trifluoroacetic acid (TFA), respectively. The processes corresponded to the single reduction of the Fe-hydride-S-proton and Fe-hydride species, respectively. When anilinium acid was used, the catalysis occurred at −1.16 V, identical with the working potential of the HOTf catalysis, although the employment of anilinium acid was only capable of achieving the Fe-hydride state on the basis of the spectral and calculated results. The thermodynamics and kinetics of individual steps of the catalysis were analyzed by density functional theory (DFT) calculations and electroanalytical simulations. The stepwise CCE or CE (C, chemical; E, electrochemical) mechanism was operative from the HOTf or TFA source, respectively. In contrast, the involvement of anilinium acid mo...

International audience; Controlling the metal nanoclusters with atomic precision is highly difficult and further studies on their transformation reactions are even more challenging. Herein we report the controlled formation of a silver alloy nanocluster [AuAg19{S2P(OnPr)(2)}(12)] (1) from an Ag-20 template via a galvanic exchange route. X-ray structural analysis reveals that the alloy structure comprises of a gold-centered Ag-12 icosahedron, Au@Ag-12, capped by seven silver atoms. Interestingly upon reacting with one equiv. of silver(I) salt, (1) can transform into a higher nuclearity nanocluster, [Au@Ag-20{S2P(OnPr)(2)}(12)](+) (2). The conversion process is studied via ESI mass spectrometry and P-31 NMR spectroscopy. This kind of size-structural transformation at the single atom level is quite remarkable. Furthermore, the compositions of all the doped nanoclusters (1, 2) were fully characterized with ESI-MS and EDS. The blue shift depicted in the UV-visible and emission spectra of the doped nanoclusters (1, 2) compared with the precursor, Ag-20, demonstrates that the doping atoms have significant effects on the electronic structures.

Controlling the metal nanoclusters with atomic precision is highly difficult and further studies on their transformation reactions are even more challenging. Herein we report the controlled formation of a silver alloy nanocluster [AuAg19{S2P(OnPr)2}12] (1) from an Ag20 template via a galvanic exchange route. X-ray structural analysis reveals that the alloy structure comprises of a gold-centered Ag12 icosahedron, Au@Ag12, capped by seven silver atoms. Interestingly upon reacting with one equiv. of silver(i) salt, (1) can transform into a higher nuclearity nanocluster, [Au@Ag20{S2P(OnPr)2}12]+ (2). The conversion process is studied via ESI mass spectrometry and 31P NMR spectroscopy. This kind of size-structural transformation at the single atom level is quite remarkable. Furthermore, the compositions of all the doped nanoclusters (1, 2) were fully characterized with ESI-MS and EDS. The blue shift depicted in the UV-visible and emission spectra of the doped nanoclusters (1, 2) compared with the precursor, Ag20, demonstrates that the doping atoms have significant effects on the electronic structures.

The heterotrimetallic complexes [FeMFe(dpa)4 Cl2 ] (M=Ni (1), Pd (2), and Pt (3); dpa- =dipyridylamido) featuring two high-spin iron centers linked by Group 10 metals were synthesized and their physical properties were investigated. Oxidation of 1-3 with suitable oxidants in CH2 Cl2 solution yielded the mixed-valent species [1]+/2+ -[3]+/2+ . The solution properties of [1]0/+/2+ -[3]0/+/2+ were characterized by 1 H NMR and UV/Vis/NIR spectroscopy as well as spectroelectrochemisty. The mixed-valent states of [1]+ -[3]+ obtained by electrochemical or chemical oxidation are classified as class II valence delocalization. The solid-state structures of 1-3, [1]+ , [3]+ , and [1]2+ were determined by single-crystal X-ray diffraction analysis, exhibiting a linear metal framework with an approximate D4 symmetry. The spin states and magnetic properties were studied by using SQUID magnetometry, EPR and Mossbauer spectroscopy, and DFT calculations. Antiferromagnetic interactions between terminal high-spin iron centers are present within [1]0/+/2+ -[3]0/+/2+ and the |J| values increase with the central metal ion changing from Ni to Pt. The DFT calculations reproduce the antiferromagnetic coupling and ascribe it to a σ-type exchange pathway. The substitution of the central metal not only influences the spin-spin interactions but also the degree of electronic delocalization between the terminal iron sites along the Fe-M-Fe chains.

The CoRu

A templated galvanic exchange performed on [Ag20 {Se2 P(OiPr)2 }12 ] of C3 symmetry with three equiv AuI yields a mixture of [Au1+x Ag20-x {Se2 P(OiPr)2 }12 ]+ (x=0-2) from which [Au@Ag20 {Se2 P(OiPr)2 }12 ]+ and [Au@Au2 Ag18 {Se2 P(OiPr)2 }12 ]+ are successfully characterized to have T and C1 symmetry, respectively. Crystal structural analyses combined with DFT calculations on the model compounds explicitly demonstrate that the central Ag0 of Ag20 being oxidized by AuI migrates to the protecting atomic shell as a new capping AgI , and both second and third Au dopants prefer occupying non-adjacent icosahedron vertices. The differences in symmetry, T and C1 , are manifested in the spatial orientation of their protecting atomic shell composed of eight capping Ag atoms as well as re-construction upon the replacement of Ag atoms on the vertices of AuAg12 icosahedral core with second and third Au dopants. As a result, a unique pathway for substitutional-doped clusters with increased nuclearity is proposed.

Atomically precise Cu-rich bimetallic superatom clusters have been synthesized by adopting a galvanic exchange strategy. [Cu@Cu

Biomimetic diiron complexes bearing redox non-innocent ligands are discussed in this review. The complexes are synthesized to model the active site of [FeFe] hydrogenase in order to elucidate the catalytic mechanism of H2 evolution and design superior artificial catalysts. Employment of the redox active ligands serves an important factor to modulate electronic structure of the Fe2 core as the similar functionality exerted by the [4Fe4S] cofactor within the H-cluster. Different types of redox active ligands are summarized. The influence of their ligation is observable in spectroscopy as well as cyclic voltammetry, and studied by theoretical calculation.

A reversible and temperature-dependent proton-relay process is demonstrated for a Fe2 complex possessing a terminal thiolate in the presence of nitrogen-based acids. The terminal sulfur site (S(t) ) of the complex forms a hydrogen-bond interaction with N,N-dimethylanilinium acid at 183 K. The Fe2 core, instead, is protonated to generate a bridging hydride at 298 K. Reversibility is observed for the tautomerization between the hydrogen-bonded pair and the Fe-hydride species. X-ray structural analysis of the hydrogen-bonded species at 193 K reveals a short N(H)⋅⋅⋅S(t) contact. Employment of pyridinium acid also results in similar behavior, with reversible proton-hydride interconversion. DFT investigation of the proton-transfer pathways indicates that the pKa value of the hydrogen-bonded species is enhanced by 3.2 pKa units when the temperature is decreased from 298 K to 183 K.

The first atomically and structurally precise silver-nanoclusters stabilized by Se-donor ligands, [Ag20 {Se2 P(Oi Pr)2 }12 ] (3) and [Ag21 {Se2 P(OEt)2 }12 ]+ (4), were isolated by ligand replacement reaction of [Ag20 {S2 P(Oi Pr)2 }12 ] (1) and [Ag21 {S2 P(Oi Pr)2 }12 ]+ (2), respectively. Furthermore, doping reactions of 4 with Au(PPh3 )Cl resulted in the formation of [AuAg20 {Se2 P(OEt)2 }12 ]+ (5). Structures of 3, 4, and 5 were determined by single-crystal X-ray diffraction. The anatomy of cluster 3 with an Ag20 core having C3 symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag21 and Au@Ag20 core of Oh symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag13 and Au@Ag12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen-passivated silver nanoparticles, which have been theoretically confirmed as 8-electron superatoms.

The first structurally characterized copper cluster with a Cu

International audience; The synthesis and structural determination of a silver nanocluster [Ag20 {S2 P(OiPr)2 }12 ] (2), which contains an intrinsic chiral metallic core, is produced by reduction of one silver ion from the eight-electron superatom complex [Ag21 {S2 P(OiPr)2 }12 ](PF6 ) (1) by borohydrides. Single-crystal X-ray analysis displays an Ag20 core of pseudo C3 symmetry comprising a silver-centered Ag13 icosahedron capped by seven silver atoms. Its n-propyl derivative, [Ag20 {S2 P(OnPr)2 }12 ] (3), can also be prepared by the treatment of silver(I) salts and dithiophosphates in a stoichiometric ratio in the presence of excess amount of [BH4 ](-) . Crystal structure analyses reveal that the capping silver-atom positions relative to their icosahedral core are distinctly different in 2 and 3 and generate isomeric, chiral Ag20 cores. Both Ag20 clusters display an emission maximum in the near IR region. DFT calculations are consistent with a description within the superatom model of an 8-electron [Ag13 ](5+) core protected by a [Ag7 {S2 P(OR)2 }12 ](5-) external shell. Two additional structural variations are predicted by DFT, showing the potential for isomerism in such [Ag20 {S2 P(OR)2 }12 ] species.