Synthesis, characterization and third-order nonlinear optical properties of a dodecaruthenium organometallic dendrimer with a zinc(ii) tetraphenylporphyrin core

A new Zn(ii) porphyrin-based dendrimer (5(2)) containing twelve Ru(ii) alkynyl fragments, has been prepared following a convergent approach in two steps from 5,10,15,20-tetra(4-ethynylphenyl)porphyrinatozinc(ii) (6). The cubic nonlinear optical (NLO) properties of 5(2) and other derivatives of 6 have been measured by third-harmonic generation (THG) at 1907 nm and by Z-scan over the spectral range 500-1700 nm, revealing the remarkable NLO response of 5(2) in the near-IR range. These results highlight the beneficial role of the extended cross fourchee-like polymetallic structure of 5(2) on its third-order NLO properties.This research was supported by grants from the “Region Bretagne” (A. M. and G. G.) and the Australian Research Council (M. G. H.). The CNRS (PICS programs No. 5676 & 7106 and LIA Redochrom) and UEB/FEDER/RTR-Bresmat (EOPT 11MF422-02 Porphamp) are acknowledged for financial support. T. G., S. K. and J.-F. H. thank GENCI (Grand Equipment National de Calcul Intensif ) for HPC resources project GENCI A0030807367-gen7367). Drs. M. Reynolds (UMR 8537), A. Bondon and O. Mongin (UMR 6226) are acknowledged for assistance during spectroscopic characterizations

Theoretical approach for new molecular organometallic wire-based devices

Les fils moléculaires, systèmes organiques conjugués incorporant plusieurs greffons organométalliques, constituent une famille de composés de grand intérêt pour l'électronique moléculaire. Les travaux présentés dans ce manuscrit s'inscrivent dans la suite logique de précédentes études de ces complexes de métaux de transition et constituent une analyse théorique, s'appuyant sur la fonctionnelle de la densité, de l'arrangement structural et des propriétés physiques de nouveaux assemblages moléculaires aux propriétés électroniques ou optiques originales. Ce manuscrit se divise en deux parties distinctes. La première traite de l'emploi des fils moléculaires organométalliques dans le domaine des automates cellulaires quantiques, un nouveau paradigme pour l'électronique fondé sur la localisation des charges de cellules moléculaires comme digit binaire et sur les répulsions coulombiennes comme moyen de transfert de l'information. Le concept, le moyen d'application à l'échelle moléculaire et l'étude de différents composés virtuels y sont développés. La seconde partie porte sur l'introduction de greffons organométalliques au sein de composés ayant des propriétés optiques linéaires et non linéaires et leur influence sur ces dernières. Deux familles de composés ont été étudiés : des systèmes émissifs à base de cycle phosphole et des dendrimères organométalliques à cœur porphyrine.Molecular wires, conjugated organic systems bearing several organometallic fragments, form a family of compounds of great interest for molecular electronics. The research works in this manuscript follow on from previous studies of transition metal complexes and constitute a density functional theory-based analysis of both structural arrangement and physical properties of new molecular devices, with unusual electronic or optical properties. This manuscript is divided in two parts. The first one concerns the application of molecular organometallic wires in the quantum cellular automata field, a new paradigm for electronics based on the charge configuration of a molecular cell as a binary digit and using Coulombic repulsion as an information transfer mode. Both the concept, its application to molecular scale et the study of several virtual compounds are discussed. The second part focuses on the incorporation of organometallic fragments in optical active compounds with linear or nonlinear properties, and the influence of metals on those properties. Two compound families have been studied: phosphole-based conjugated emitters and organometallic porphyrine-based dendrimers

Zwitterionic Mixed-Valence Species for the Design of Neutral Clocked Molecular Quantum-Dot Cellular Automata

International audienceMixed-valence compounds can be used for the design of molecular quantum-dot cellular automata (QCA). Here, we investigate the QCA properties of a three-dot "Y"-shaped functionalized zwitterionic neutral -carborane model 1-(3,5-{Cp(dHpe)Fe-C≡C-}(CH))-10-Cp(dHpe)Fe-C≡C--1-CBH () (Cp = cyclopentadienyl (η-CH) and dHpe = 1,2-bis(phosphino)ethane (HPCHCHPH)) as a neutral clocked molecular half-cell. DFT results clearly demonstrate that can display simultaneously the two most basic properties necessary for clocked QCA operation, i.e., bistable switching behavior and clocked control. This is possible due to the three stable states (two active and one null) of , corresponding to occupation of each of the three iron-ethynyl groups by the positive charge. In addition, the proximal electronic bias effects can be overcome by the zwitterionic nature of , which could be imposed by external counterions, rendering these effects more predictable

Enhanced Cooperativity in Supported Spin-Crossover Metal-Organic Frameworks

The impact of surface deposition on cooperativity is explored in Au(111)-supported self-assembled metal-organic frameworks (MOFs) based on Fe(II) ions. Using a thermodynamic model, we first demonstrate that dimensionality reduction combined with deposition on a metal surface is likely to deeply enhance the spin-crossover cooperativity, going from γ = 16 K for the bulk material to γ2D = 386 K for its 2D supported derivative. On the basis of density functional theory, we then elucidate the electronic structure of a promising Fe-based MOF. A chemical strategy is proposed to turn a weakly interacting magnetic system into a strongly cooperative spin-crossover monolayer with γMOF = 83 K. These results open a promising route to the fabrication of cooperative materials based on SCO Fe(II) platforms

Electronic Properties of Poly-Yne Carbon Chains and Derivatives with Transition Metal End-Groups

International audienceDuring the last three decades, experimental chemists have forged a plethora of bimetallic molecular wires in which two redox-active metal termini are linked by a carbon-rich bridge. Their extensive redox chemistry with multiple, stepwise, one-electron oxidation processes provide them with some interesting electronic and/or magnetic properties for potential applications. The nature of both the metal end-groups and the carbon bridge has a significant effect on the redox process, which is of paramount importance for the design of these systems. Indeed, examples of mono-oxidized complexes range from weakly coupled mixed-valence species through more strongly coupled systems in which the bridging ligand can be intimately involved in electron transfer processes. Similarly, di-oxidized species can encompass difference in magnetic behavior depending upon not only the nature of the framework of the systems but also the torsion angle between the terminal spin carriers, which allows the inversion of the singlet vs. triplet ground states. Theoretical quantum chemical computations have greatly assisted the development of this field of research. This review illustrates how, in synergy with experiments, computational results can provide additional valuable information on the nature of the localized vs. delocalized electronic communication in the mono-oxidized mixed-valence species, or the magnetic coupling differences and characteristics of the di-oxidized complexes

Theoretical and DFT Study of Atypical Pentanuclear [(iPr3P)Ni]5Hn (n = 4, 6, 8) Clusters: What are the Rules?

The structural, bonding and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron rich iPr3P of the type [(iPr3P)Ni]5Hn (n = 4, 6, 8) (H4, H6, H8) and their anionic models where iPr3P are substituted by H− (H4, H6, H8) were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with low singlet-triplet gaps for H4 and H6, similar to previously reported experimental values. Molecular orbital theory description clusters were investigated using the simplified model complexes [HNi]5Hn5– (n = 4, 6, 8) (H4, H6, H8). The results show that there are three skeletal electron pairs (SEPs) in H4. The addition of two molecules of H2 to form H6 and H8 results in the partial or full occupation of two degenerate MOs (e* set) that give two SEPs and one SEP, respectively. Indeed, the occupation of these low-lying weakly antibonding orbitals govern the multielectron chemistry available for these clusters, and play a role in their unique reactivity

Autoimmune thrombotic thrombocytopenic purpura associated with disseminated sarcoidosis: A case report

Abstract Sarcoidosis is an inflammatory disease known to be associated with multiple autoimmune disorders. There is a restricted number of descriptions of the association between sarcoidosis and autoimmune thrombotic thrombocytopenic purpura (aTTP). We present the case of a 63‐year‐old woman admitted to the hospital to investigate a possible sarcoidosis who had hemolytic anemia and thrombocytopenia, with low ADAMTS13 activity and anti‐ADAMTS13 antibodies, leading to a diagnosis of aTTP. Sarcoidosis was later confirmed and the two conditions evolved separately after 6 months, questioning the link between them. Clinicians should be aware of this rare cause of thrombocytopenia in patients with sarcoidosis, as aTTP is a life‐threatening condition

Enhanced Cooperativity in Supported Spin-Crossover Metal-Organic Frameworks

International audienceThe impact of surface deposition on cooperativity is explored in Au(111)-supported self-assembled metal-organic frameworks (MOFs) based on Fe(II) ions. Using a thermodynamic model, we first demonstrate that dimensionality reduction combined with deposition on a metal surface is likely to deeply enhance the spin-crossover cooperativity, going from gamma(3D) = 16 K for the bulk material to gamma(supp)(2D) = 386 K for its 2D supported derivative. On the basis of density functional theory, we then elucidate the electronic structure of a promising Fe-based MOF. A chemical strategy is proposed to turn a weakly interacting magnetic system into a strongly cooperative spin-crossover monolayer with gamma(Au(111))(MOF) = 83 K. These results open a promising route to the fabrication of cooperative materials based on SCO Fe(II) platforms

Theoretical and DFT Study of Atypical Pentanuclear [(iPr3P)Ni]5Hn (n = 4, 6, 8) Clusters: What are the Rules?

International audienceThe structure, bonding, and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron-rich iPr3P of the type [(iPr3P)Ni]5Hn (n = 4, 6, 8; H4, H6, H8) and their anionic models where iPr3P are substituted by H– (H4′, H6′, H8′) were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with small singlet–triplet gaps for H4 and H6, similar to previously reported experimental values. Molecular orbital theory description clusters were investigated using the simplified model complexes [HNi]5Hn5– (n = 4, 6, 8; H4′, H6′, H8′). The results show that there are three skeletal electron pairs (SEPs) in H4′. The addition of two molecules of H2 to form H6′ and H8′ results in the partial or full occupation of two degenerate MOs (e* set) that give two SEPs and one SEP, respectively. Indeed, the occupation of these low-lying weakly antibonding orbitals governs the multielectron chemistry available for these clusters and plays a role in their unique reactivity

Theoretical and DFT Study of Atypical Pentanuclear [(^<i>i</i>Pr₃P)Ni]₅H_<i>n</i> (<i>n</i> = 4, 6, 8) Clusters: What are the Rules?

The structure, bonding, and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron-rich iPr3P of the type [(iPr3P)Ni]5Hn (n = 4, 6, 8; H4, H6, H8) and their anionic models where iPr3P are substituted by H– (H4′, H6′, H8′) were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with small singlet–triplet gaps for H4 and H6, similar to previously reported experimental values. Molecular orbital theory description clusters were investigated using the simplified model complexes [HNi]5Hn5– (n = 4, 6, 8; H4′, H6′, H8′). The results show that there are three skeletal electron pairs (SEPs) in H4′. The addition of two molecules of H2 to form H6′ and H8′ results in the partial or full occupation of two degenerate MOs (e* set) that give two SEPs and one SEP, respectively. Indeed, the occupation of these low-lying weakly antibonding orbitals governs the multielectron chemistry available for these clusters and plays a role in their unique reactivity