Heteroleptic Co(III) bisdithiocarbamato-dithione complexes: Synthesis, structure and bonding of [Co(Et₂dtc)₂(R₂pipdt)]BF₄ (R = Me, 1; Ph, 2; pipdt = piperazin-2,3-dithione) complexes

The reaction between the binuclear cobalt complex, [Co2(Et2dtc)5]+, and Me2pipdt and Ph2pipdt ligands has provided almost quantitatively the cobalt tris-chelate heteroleptic complexes [Co(Et2dtc)2(R2pipdt)]BF4 (1 and 2). The molecular structure of 2 shows the metal in a distorted octahedral geometry. The nature of the bonding in these complexes has been elucidated with the support of DFT TD-DFT calculations. Both chelating S,S donors work as weak-field ligands. The comparison of the chemical reactivity for the homoleptic dithiocarbamate complex [Co(Et2dtc)3] and the heteroleptic [Co(Et2dtc)2(Ph2pipdt)]+ derivative shows that the global softness σ is significantly higher in [Co(Et2dtc)2(Ph2pipdt)]+ than in the homoleptic dithiocarbamate complex, due to a reduction of nephelauxetic effect induced by the dithioxamide ligand. The kinetics for the reaction between the reagents in CH2Cl2 has been followed spectrophotometrically as a function of temperature in pseudo-first order conditions with respect to R2pipdt ligands. Kinetic results further support a reaction mechanism involving a one-end reversible dissociation of the [Co2(Et2dtc)5]+ dimer forming a reactive cobalt(III)dithiocarbamato center susceptible to attack by nucleophiles. The effectiveness and versatility of the above reaction is an easy and clean method to provide heteroleptic-dithiocarbamates with a variety of suitable ligands of interest for applicative purposes.</p

Spectral Tuning and Emission Enhancement through Lanthanide Coordination in a Dual Visible–Near-Infrared Emissive Cyanide-Bridged Heterometallic Ru(II)–Er(III) Complex

Owing to their unique luminescent properties and photosensitizing capability, cyanoruthenium(II) complexes with diimine ligands are the subject of intense research striving for routes for tuning their electronic properties and improving their emission quantum yield. In this work, we describe a heterometallic d-f cyanide-bridged Ru(II)–Er(III) assembly obtained by the direct reaction of trivalent erbium salt with the neutral [Ru(bipy)2(CN)2] (bipy = 2,2′-bipyridine) metalloligand. This strategy allows for accommodating inorganic negatively charged anions such as nitrate and oxalate in the coordination sphere of the lanthanide ion. As a result, a dimeric tetranuclear discrete molecular architecture is obtained, where the two constituting monomeric Ru(II)-CN-Er(III) units are bridged by an oxalate anion coordinating two Er(III) ions in a bis-bidentate fashion. Strikingly, this heterometallic compound shows intense dual emission in the visible and near-infrared spectral ranges under single-wavelength excitation in both solution and the crystalline state. The effect of Er(III) coordination through a cyanide bridge is thoroughly discussed, also with the support of DFT calculations, to highlight the factors that induce the observed spectral hypsochromism and, more importantly, the remarkable 10-fold-increased emission quantum yield of the [Ru(bipy)2(CN)2] moiety in the visible range. We show that the described coordination mode induces an energy raise of the emissive triplet metal-to-ligand charge transfer (3MLCT) state and even a more pronounced lifting of the nonemissive Ru(II) triplet metal-centered (3MC) states, suppressing thermal deactivation channels. Furthermore, owing to the reduced number of water molecules and quenching groups surrounding the lanthanide ion in the molecular architecture, relatively intense erbium emission at 1.5 μm telecom wavelength is detected through sensitization from the Ru(II) metalloligand. We suggest that this compound can find applications as an efficient solid-state dual emitter

Structural Diversity and Physical Properties of Paramagnetic Molecular Conductors Based on Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and the Tris(chloranilato)ferrate(III) Complex

Electrocrystallization of bis­(ethylenedithio)­tetrathiafulvalene (BEDT-TTF) in the presence of the tris­(chloranilato)­ferrate­(III) [Fe­(Cl₂An)₃]^3– paramagnetic chiral anion in different stoichiometric ratios and solvent mixtures afforded three different hybrid systems formulated as [BEDT-TTF]₃[Fe­(Cl₂An)₃]·3CH₂Cl₂·H₂O (<b>1</b>), δ-[BEDT-TTF]₅[Fe­(Cl₂An)₃]·4H₂O (<b>2</b>), and α‴-[BEDT-TTF]₁₈[Fe­(Cl₂An)₃]₃·3CH₂Cl₂·6H₂O (<b>3</b>). Compound <b>1</b> presents an unusual structure without the typical alternating organic and inorganic layers, whereas compounds <b>2</b> and <b>3</b> show a segregated organic–inorganic crystal structure where layers formed by Λ and Δ enantiomers of the paramagnetic complex, together with dicationic BEDT-TTF dimers, alternate with layers where the donor molecules are arranged in the δ (<b>2</b>) and α‴ (<b>3</b>) packing motifs. Compound <b>1</b> behaves as a semiconductor with a much lower conductivity due to the not-layered structure and strong dimerization between the fully oxidized donors, whereas <b>2</b> and <b>3</b> show semiconducting behaviors with high room-temperature conductivities of ca. 2 S cm^–1 and 8 S cm^–1, respectively. The magnetic properties are dominated by the paramagnetic <i>S</i> = 5/2 [Fe­(Cl₂An)₃]^3– anions whose high-spin character is confirmed by electron paramagnetic resonance and magnetic susceptibility measurements. The correlation between crystal structure and conductivity behavior was studied by means of tight-binding band structure calculations, which support the observed conducting properties

Structural Diversity and Physical Properties of Paramagnetic Molecular Conductors Based on Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and the Tris(chloranilato)ferrate(III) Complex

Electrocrystallization of bis­(ethylenedithio)­tetrathiafulvalene (BEDT-TTF) in the presence of the tris­(chloranilato)­ferrate­(III) [Fe­(Cl₂An)₃]^3– paramagnetic chiral anion in different stoichiometric ratios and solvent mixtures afforded three different hybrid systems formulated as [BEDT-TTF]₃[Fe­(Cl₂An)₃]·3CH₂Cl₂·H₂O (<b>1</b>), δ-[BEDT-TTF]₅[Fe­(Cl₂An)₃]·4H₂O (<b>2</b>), and α‴-[BEDT-TTF]₁₈[Fe­(Cl₂An)₃]₃·3CH₂Cl₂·6H₂O (<b>3</b>). Compound <b>1</b> presents an unusual structure without the typical alternating organic and inorganic layers, whereas compounds <b>2</b> and <b>3</b> show a segregated organic–inorganic crystal structure where layers formed by Λ and Δ enantiomers of the paramagnetic complex, together with dicationic BEDT-TTF dimers, alternate with layers where the donor molecules are arranged in the δ (<b>2</b>) and α‴ (<b>3</b>) packing motifs. Compound <b>1</b> behaves as a semiconductor with a much lower conductivity due to the not-layered structure and strong dimerization between the fully oxidized donors, whereas <b>2</b> and <b>3</b> show semiconducting behaviors with high room-temperature conductivities of ca. 2 S cm^–1 and 8 S cm^–1, respectively. The magnetic properties are dominated by the paramagnetic <i>S</i> = 5/2 [Fe­(Cl₂An)₃]^3– anions whose high-spin character is confirmed by electron paramagnetic resonance and magnetic susceptibility measurements. The correlation between crystal structure and conductivity behavior was studied by means of tight-binding band structure calculations, which support the observed conducting properties

Synthesis and Physical Properties of K₄[Fe(C₅O₅)₂(H₂O)₂](HC₅O₅)₂·4H₂O (C₅O₅^2– = Croconate): A Rare Example of Ferromagnetic Coupling via H-bonds

The reaction of the croconate dianion (C₅O₅)^2– with a Fe­(III) salt has led, unexpectedly, to the formation of the first example of a discrete Fe­(II)–croconate complex without additional coligands, K₄[Fe­(C₅O₅)₂(H₂O)₂]­(HC₅O₅)₂·4H₂O (<b>1</b>). <b>1</b> crystallizes in the monoclinic <i>P</i>2₁/<i>c</i> space group and presents discrete octahedral Fe­(II) complexes coordinated by two chelating C₅O₅^2– anions in the equatorial plane and two trans axial water molecules. The structure can be viewed as formed by alternating layers of <i>trans</i>-diaquabis­(croconato)­ferrate­(II) complexes and layers containing the monoprotonated croconate anions, HC₅O₅^–, and noncoordinated water molecules. Both kinds of layers are directly connected through a hydrogen bond between an oxygen atom of the coordinated dianion and the protonated oxygen atom of the noncoordinated croconate monoanion. A H-bond network is also formed between the coordinated water molecule and one oxygen atom of the coordinated croconate. This H-bond can be classified as strong–moderate being the O···O bond distance (2.771(2) Å) typical of moderate H-bonds and the O–H···O bond angle (174(3)°) typical of strong ones. This H-bond interaction leads to a quadratic regular layer where each [Fe­(C₅O₅)₂(H₂O)₂]^2– anion is connected to its four neighbors in the plane through four equivalent H-bonds. From the magnetic point of view, these connections lead to an <i>S</i> = 2 quadratic layer. The magnetic properties of <b>1</b> have been reproduced with a 2D square lattice model for <i>S</i> = 2 ions with <i>g</i> = 2.027(2) and <i>J</i> = 4.59(3) cm^–1. This model reproduces quite satisfactorily its magnetic properties but only above the maximum. A better fit is obtained by considering an additional antiferromagnetic weak interlayer coupling constant (<i>j</i>) through a molecular field approximation with <i>g</i> = 2.071(7), <i>J</i> = 2.94(7) cm^–1, and <i>j</i> = −0.045(2) cm^–1 (the Hamiltonian is written as <i>H</i> = –<i>JS_iS_j</i>). Although this second model might still be improved since there is also an extra contribution due to the presence of ZFS in the Fe­(II) ions, it confirms the presence of weak ferromagnetic Fe–Fe interactions through H-bonds in compound <b>1</b> which represents one of the rare examples of ferromagnetic coupling via H-bonds

Fully Efficient Direct Yb-to-Er Energy Transfer at Molecular Level in a Near-Infrared Emitting Heterometallic Trinuclear Quinolinolato Complex

Combined chemical/photophysical studies on the mixed Yb–Er trinuclear lanthanide quinolinolato compound Yb₂ErQ₉ and on the corresponding Yb₃Q₉ analogue have been performed. In the mixed-metal molecular species, the ligands, acting as a bridge, allow the two metals to lie at optimal distance for direct Yb-to-Er resonance energy transfer, which reaches nearly unitary efficiency. The obtained results show that polynuclear lanthanide complexes provide a suitable strategy for achieving effective erbium sensitization in solution-processable molecular materials

Optical Sensitivity Gain in Silica-Coated Plasmonic Nanostructures

Ultrathin films of silica realized by sol-gel synthesis and dip-coating techniques were successfully applied to predefined metal/polymer plasmonic nanostructures to spectrally tune their resonance modes and to increase their sensitivity to local refractive index changes. Plasmon resonance spectral shifts up to 100 nm with slope efficiencies of ∼8 nm/nm for increasing layer thickness were attained. In the ultrathin layer regime (<10 nm), which could be reached by suitable dilution of the silica precursors and optimization of the deposition speed, the sensitivity of the main plasmonic resonance to refractive index changes in aqueous solution could be increased by over 50% with respect to the bare plasmonic chip. Numerical simulations supported experimental data and unveiled the mechanism responsible for the optical sensitivity gain, proving an effective tool in the design of high-performance plasmonic sensors

Let’s talk about porn! On Youth, Gender and Pornography in Sweden

A simple change of the substituents in the bridging ligand allows tuning of the ordering temperatures, <i>T</i>_c, in the new family of layered chiral magnets A­[M^IIM^III(X₂An)₃]·G (A = [(H₃O)­(phz)₃]⁺ (phz = phenazine) or NBu₄⁺; X₂An^2– = C₆O₄X₂^2– = 2,5-dihydroxy-1,4-benzoquinone derivative dianion, with M^III = Cr, Fe; M^II = Mn, Fe, Co, etc.; X = Cl, Br, I, H; G = water or acetone). Depending on the nature of X, an increase in <i>T</i>_c from ca. 5.5 to 6.3, 8.2, and 11.0 K (for X = Cl, Br, I, and H, respectively) is observed in the MnCr derivative. Furthermore, the presence of the chiral cation [(H₃O)­(phz)₃]⁺, formed by the association of a hydronium ion with three phenazine molecules, leads to a chiral structure where the Δ-[(H₃O)­(phz)₃]⁺ cations are always located below the Δ-[Cr­(Cl₂An)₃]^3– centers, leading to a very unusual localization of both kinds of metals (Cr and Mn) and to an eclipsed disposition of the layers. This eclipsed disposition generates hexagonal channels with a void volume of ca. 20% where guest molecules (acetone and water) can be reversibly absorbed. Here we present the structural and magnetic characterization of this new family of anilato-based molecular magnets

New BDH-TTP/[M^III(C₅O₅)₃]^3– (M = Fe, Ga) Isostructural Molecular Metals

Two new isostructural molecular metals(BDH-TTP)₆[M^III(C₅O₅)₃]·CH₂Cl₂ (BDH-TTP = 2,5-bis­(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, where M = Fe (<b>1</b>) and Ga (<b>2</b>))have been prepared and fully characterized. Compound <b>1</b> is a molecular conductor showing paramagnetic behavior, which is due to the presence of isolated [Fe­(C₅O₅)₃]^3– complexes with high-spin <i>S</i> = ⁵/₂ Fe­(III) metal ions. The conductivity originates from the BDH-TTP organic donors arranged in a κ-type molecular packing. At 4 kbar, compound <b>1</b> behaves as a metal down to ∼100 K, showing high conductivity (∼10 S cm^–1) at room temperature. When applying a pressure higher than 7 kbar, the metal–insulator (M-I) transition is suppressed and the compound retains the metallic state down to low temperatures (2 K). For <b>1</b>, ESR signals have been interpreted as being caused by the fine structure splitting of the high-spin (<i>S</i> = ⁵/₂) state of Fe­(III) in the distorted octahedral crystal field from the ligands. At 4 kbar, the isostructural compound <b>2</b> behaves as a metal down to ∼100 K, although it is noteworthy that the M-I transition is not suppressed, even at pressures of 15 kbar. For <b>2</b>, only the signal assigned to delocalized π-electrons has been observed in the ESR measurements

New BDH-TTP/[M^III(C₅O₅)₃]^3– (M = Fe, Ga) Isostructural Molecular Metals

Two new isostructural molecular metals(BDH-TTP)₆[M^III(C₅O₅)₃]·CH₂Cl₂ (BDH-TTP = 2,5-bis­(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, where M = Fe (<b>1</b>) and Ga (<b>2</b>))have been prepared and fully characterized. Compound <b>1</b> is a molecular conductor showing paramagnetic behavior, which is due to the presence of isolated [Fe­(C₅O₅)₃]^3– complexes with high-spin <i>S</i> = ⁵/₂ Fe­(III) metal ions. The conductivity originates from the BDH-TTP organic donors arranged in a κ-type molecular packing. At 4 kbar, compound <b>1</b> behaves as a metal down to ∼100 K, showing high conductivity (∼10 S cm^–1) at room temperature. When applying a pressure higher than 7 kbar, the metal–insulator (M-I) transition is suppressed and the compound retains the metallic state down to low temperatures (2 K). For <b>1</b>, ESR signals have been interpreted as being caused by the fine structure splitting of the high-spin (<i>S</i> = ⁵/₂) state of Fe­(III) in the distorted octahedral crystal field from the ligands. At 4 kbar, the isostructural compound <b>2</b> behaves as a metal down to ∼100 K, although it is noteworthy that the M-I transition is not suppressed, even at pressures of 15 kbar. For <b>2</b>, only the signal assigned to delocalized π-electrons has been observed in the ESR measurements