Experimental and theoretical studies of the electronic transport of an extended curcuminoid in graphene nano-junctions.

Exploiting the potential of curcuminoids (CCMoids) as molecular platforms, a new 3.53 nm extended system (pyACCMoid, 2) has been designed in two steps by reacting a CCMoid with amino-terminal groups (NH-CCMoid, 1, of 1.79 nm length) with polycyclic aromatic hydrocarbon (PAH) aldehydes.

Intrinsic Permeation and Anti-Inflammatory Evaluation of Curcumin, Bisdemethoxycurcumin and Bisdemethylcurcumin by a Validated HPLC-UV Method.

Curcumin shows anti-inflammatory activity, and it has been widely investigated for neurodegenerative diseases, adjuvant treatment in AIDS and antitumor activity against different tumors, among other activities. The goal of this work was to evaluate the capacity of curcumin and its derivatives (bisdemethoxycurcumin and bisdemethylcurcumin) in preventing the irritant effects of topically applied xylol and to assess the intrinsic capacity of curcuminoids in permeating human skin by ex vivo permeation tests. Its secondary goal was to validate an HPLC method to simultaneously determine the curcuminoids in the samples from the ex vivo permeation studies and drug extraction from the skin.

Dielectric behavior of curcuminoid polymorphs on different substrates by direct soft vacuum deposition.

Our work examines the structural-electronic correlation of a new curcuminoid, AlkCCMoid, as a dielectric material on different substrates. For this purpose, we show a homemade sublimation method that allows the direct deposition of molecules on any type of matrix. The electronic properties of AlkCCMoid have been evaluated by measurements on single crystals, microcrystalline powder, and sublimated samples, respectively.

Luminescence of Macrocyclic Mononuclear Dy Complexes and Their Immobilization on Functionalized Silicon-Based Surfaces.

Two mononuclear Dy complexes, [Dy(L)(NCS)] () and [Dy(L)(NCS)] (), where L ( = 1-2) corresponds to a macrocyclic ligand derived from 2,6-pyridinedicarboxaldehyde and ethylenediamine (L) and 1,3-diaminepropane (L) were immobilized on functionalized silicon-based surfaces. This was achieved by the microcontact printing (μCP) technique, generating patterns on a functionalized surface via covalent bond formation through the auxiliary -NCS ligands present in the macrocyclic complex species. With this strategy, it was possible to control the position of the immobilized molecules on the surface.

Emergent Insulator-Metal Transition with Tunable Optical and Electrical Gap in Thin Films of a Molecular Conducting Composite.

Composites exhibit unique synergistic properties emerging when components with different properties are combined. The tuning of the energy bandgap in the electronic structure of the material allows designing tailor-made systems with desirable mechanical, electrical, optical, and/or thermal properties. Here, we study an emergent insulator-metal transition at room temperature in bilayered (BL) thin-films comprised of polycarbonate/molecular-metal composites.

Room-Temperature Spin-Dependent Transport in Metalloporphyrin-Based Supramolecular Wires.

Here we present room-temperature spin-dependent charge transport measurements in single-molecule junctions made of metalloporphyrin-based supramolecular assemblies. They display large conductance switching for magnetoresistance in a single-molecule junction. The magnetoresistance depends acutely on the probed electron pathway through the supramolecular wire: those involving the metal center showed marked magnetoresistance effects as opposed to those exclusively involving the porphyrin ring which present nearly complete absence of spin-dependent charge transport.

Spin-Phonon Coupling and Slow-Magnetic Relaxation in Pristine Ferrocenium.

We report the spin dynamic properties of non-substituted ferrocenium complexes. Ferrocenium shows a field-induced single-molecule magnet behaviour in DMF solution while cobaltocene lacks slow spin relaxation neither in powder nor in solution. Multireference quantum mechanical calculations give a non-Aufbau orbital occupation for ferrocenium with small first excitation energy that agrees with the relatively large measured magnetic anisotropy for a transition metal S=1/2 system.

Broadening the scope of high structural dimensionality nanomaterials using pyridine-based curcuminoids.

We present a new heteroditopic ligand (3pyCCMoid) that contains the typical skeleton of a curcuminoid (CCMoid) decorated with two 3-pyridyl groups. The coordination of 3pyCCMoid with ZnII centres results in a set of novel coordination polymers (CPs) that display different architectures and dimensionalities (from 1D to 3D). Our work analyses how synthetic methods and slight changes in the reaction conditions affect the formation of the final materials.

Tuning Single-Molecule Conductance in Metalloporphyrin-Based Wires via Supramolecular Interactions.

Nature has developed supramolecular constructs to deliver outstanding charge-transport capabilities using metalloporphyrin-based supramolecular arrays. Herein we incorporate simple, naturally inspired supramolecular interactions via the axial complexation of metalloporphyrins into the formation of a single-molecule wire in a nanoscale gap. Small structural changes in the axial coordinating linkers result in dramatic changes in the transport properties of the metalloporphyrin-based wire.

Single molecule magnets of cobalt and zinc homo- and heterometallic coordination polymers prepared by a one-step synthetic procedure.

The synthesis of 1D cobalt and zinc monometallic and heterometallic coordination polymers (CPs) was carried out applying one-pot synthetic methods by using either supercritical carbon dioxide or ethanol as the solvent. A collection of four 1D CPs were thus obtained by the combination of a metal (or a mixture of metals) with the linker 1,4-bis(4-pyridylmethyl)benzene. The used metallic complexes were zinc and cobalt hexafluoroacetylacetonate, which can easily incorporate pyridine ligands in the coordination sphere of the metal centre.

Slow-spin relaxation of a low-spin S = 1/2 Fe carborane complex.

In this communication, we report the first evidence of slow-spin relaxation of a low-spin FeIII carborane complex. Iron S = 1/2 complexes showing such behaviour are particularly appealing as qubit candidates because they fulfil some of the main requirements to reach long decoherence times, such as moderate magnetic anisotropy, small spin, metal element mainly with zero-nuclear spin and furthermore, large versatility to introduce chemical modifications.

Correction: A new family of fullerene derivatives: fullerene-curcumin conjugates for biological and photovoltaic applications.

[This corrects the article DOI: 10.1039/C8RA08334G.].

Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds.

We have studied the single-molecule conductance of a family of curcuminoid molecules (CCMs) using the mechanically controlled break junction (MCBJ) technique. The CCMs under study contain methylthio (MeS-) as anchoring groups: MeS-CCM (), the free-ligand organic molecule, and two coordination compounds, MeS-CCM-BF () and MeS-CCM-Cu (), where ligand coordinates to a boron center (BF group) and to a Cu moiety, respectively. We found that the three molecules present stable molecular junctions allowing detailed statistical analysis of their electronic properties.

Boosting Self-Assembly Diversity in the Solid-State by Chiral/Non-Chiral Zn -Porphyrin Crystallization.

A chiral Zn porphyrin derivative 1 and its achiral analogue 2 were studied in the solid state. Considering the rich molecular recognition of designed metalloporphyrins 1 and 2 and their tendency to crystallize, they were recrystallized from two solvent mixtures (CH Cl /CH OH and CH Cl /hexane). As a result, four different crystalline arrangements (1 a,b and 2 a,b, from 0D to 2D) were obtained.

Coumarin Derivative Directly Coordinated to Lanthanides Acts as an Excellent Antenna for UV-Vis and Near-IR Emission.

A chelating coumarin-derived ligand sensitizes all emitting lanthanide ions in the solid state and gives high absolute quantum yields for ethanol solutions of complexes of Sm, Eu, Tb, and Dy, above 20% for the last two. Crystal structures of these four complexes are [Ln(Cum)(HO)(X)]·X where X = MeOH or EtOH.

A new family of fullerene derivatives: Fullerene-curcumin conjugates for biological and photovoltaic applications.

The synthesis and characterization of a family of [60]fullerocurcuminoids obtained via Bingel reactions is reported. The new C derivatives include curcumin and curcuminoids with a variety of end groups. Preliminary biological experiments show the potential activity of the compound containing a curcumin addend, which exhibits moderate anti-HIV-1 and radical scavenger properties, but no anti-cancer activity.

Hetero-bimetallic paddlewheel clusters in coordination polymers formed by a water-induced single-crystal-to-single-crystal transformation.

Herein we report a water-induced single-crystal to single-crystal transformation that involves the formation of hetero-bimetallic paddlewheel clusters in coordination polymers. Through this transformation, which involves the cleavage and formation of different coordination bonds, two different Cu(ii)-Zn(ii) and Cu(ii)-Ni(ii) paddlewheel units exhibiting a 1 : 1 metal ratio were created.

Multiscale Approach to the Study of the Electronic Properties of Two Thiophene Curcuminoid Molecules.

We studied the electronic and conductance properties of two thiophene-curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), in which the only structural difference is the position of the sulfur atoms in the thiophene terminal groups. We used electrochemical techniques as well as UV/Vis absorption studies to obtain the values of the HOMO-LUMO band gap energies, showing that molecule 1 has lower values than 2. Theoretical calculations show the same trend.

Carving a 1D Co(II)-carboranylcarboxylate system by using organic solvents to create stable trinuclear molecular analogues: complete structural and magnetic studies.

This work presents a straightforward methodology to achieve small linear trinuclear molecules based on the Co(II)-carboranylcarboxylate system obtained by carving a 1D polynuclear analogous system with the use of diethylether. The reaction of the carboranylcarboxylic ligand, 1-CH3-2-CO2H-1,2-closo-C2B10H10 (LH) with different cobalt salts leads to the polynuclear compound [Co2(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)4(THF)4], and the polymeric [Co(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)2]n(H2O)n. This latter 1D chain has been obtained by an unprecedented synthetic strategy for the isolation of cobalt(ii) compounds.

Multiscale study of mononuclear Co SMMs based on curcuminoid ligands.

This work introduces a novel family of Co species having a curcuminoid (CCMoid) ligand, 9Accm, attached, namely [Co(9Accm)(py)] () and [Co(9Accm)(2,2'-bpy)] (), achieved in high yields by the use of a microwave reactor, and exhibiting two different arrangements for the 9Accm ligands, described as ""() and ""(). The study of the similarities/differences of the magnetic, luminescent and surface behaviors of the two new species, and , is the main objective of the present work. The determined single-crystal structures of both compounds are the only Co-CCMoid structures described in the literature so far.

Sequential Electron Transport and Vibrational Excitations in an Organic Molecule Coupled to Few-Layer Graphene Electrodes.

Graphene electrodes are promising candidates to improve reproducibility and stability in molecular electronics through new electrode-molecule anchoring strategies. Here we report sequential electron transport in few-layer graphene transistors containing individual curcuminoid-based molecules anchored to the electrodes via π-π orbital bonding. We show the coexistence of inelastic co-tunneling excitations with single-electron transport physics due to an intermediate molecule-electrode coupling; we argue that an intermediate electron-phonon coupling is the origin of these vibrational-assisted excitations.

Neodymium 1D systems: targeting new sources for field-induced slow magnetization relaxation.

Two non-isostructural homometallic 1D neodymium species displaying field-induced slow magnetization relaxations are presented together with theoretical studies. It is established that both systems are better described as organized 1D single molecule magnets (SMMs). Studies show great potential of Nd(III) ions to provide homometallic chains with slow magnetic relaxation.

Water-soluble manganese inorganic polymers: the role of carborane clusters and producing large structural adjustments from minor molecular changes.

The reaction of two different carboranylcarboxylate ligands, 1-CH3-2-CO2H-1,2-closo-C2B10H10 or 1-CO2H-1,2-closo-C2B10H11, with MnCO3 in water leads to polymeric compounds 1 a and 1 b. Both compounds have been characterized by analytical and spectroscopic techniques. Additionally, electrochemical techniques have also been used for compound 1 a.

Huge magnetic anisotropy in a trigonal-pyramidal nickel(II) complex.

The work presented herein shows the experimental and theoretical studies of a mononuclear nickel(II) complex with the largest magnetic anisotropy ever reported. The zero-field-splitting D parameter, extracted from the fits of the magnetization and susceptibility measurements, shows a large value of -200 cm(-1), in agreement with the theoretical value of -244 cm(-1) obtained with the CASPT2-RASSI method.

A racemic and enantiopure unsymmetric diiron(III) complex with a chiral o-carborane-based pyridylalcohol ligand: combined chiroptical, magnetic, and nonlinear optical properties.

The design of molecule-based systems combining magnetic, chiroptical and second-order optical nonlinear properties is still very rare. We report an unusually unsymmetric diiron(III) complex 1, in which three bulky chiral carboranylpyridinealkoxide ligands (oCBhmp(-)) bridge both metal ions and the complex shows the above-mentioned properties. The introduction of o-carborane into the 2-(hydroxymethyl)pyridine (hmpH) architecture significantly alters the coordination of the simple or aryl-substituted 2-hmpH.