Chiral magnetic-nanobiofluids for rapid electrochemical screening of enantiomers at a magneto nanocomposite graphene-paste electrode

The development of highly sensitive and selective enantiomeric platforms towards the rapid screening of active pharmaceutical ingredients (APIs) is nowadays a crucial challenge in several fields related to pharmacology, biomedicine, biotechnology and (bio)sensors. Herein, it is presented a novel, facile and generic methodology focused on exploiting the synergistically and electrocatalytic properties of chiral magnetic-nanobiofluids (mNBFs) with electrochemical enantiobiosensing at a magneto nanocomposite graphene paste electrode (mNC-GPE). The feasibility of this approach has been validated by chirally recognizing tryptophan (TRP) enantiomers as a proof-of-concept. For this aim, a specific chiral mNBF based on an aqueous dispersion of cobalt ferrite loaded with gold nanoparticles carrying a thiolated β-cyclodextrin (β-CD-SH/Au/CoFe₂O₄-NPs) has been synthesized and used towards the supramolecular discrimination of TRP enantiomers at an advanced graphene-paste transducer via cyclic voltammetry. This strategy, which is the first demonstration of applicability of chiral mNBFs for electrochemical enantiorecognition, opens up new approaches into enantio(bio)sensing.

A four-state capacitance molecular switch based on a redox active tetrathiafulvalene self-assembled monolayer

A tetrathiafulvalene self-assembled monolayer has been successfully exploited as a 4-state electrochemical switch using the capacitance as output signal.

Direct covalent grafting of an organic radical core on gold and silver

A newly designed radical–anchor (R–A) molecule was synthesized and covalently grafted on Ag and Au surface at one atom distance preserving the molecular spin.

Study of the E–Z stilbene isomerisation in perchlorotriphenyl-methane (PTM) derivatives

No reversibility in the E → Z isomerization of two vinylidene derivatives due to steric effects on the Z isomer is demonstrated.

A surface confined yttrium(iii) bis-phthalocyaninato complex: a colourful switch controlled by electrons

SAMs of a Y(iii) double-decker complex on ITO have been prepared and their electrical and optical properties explored, exhibiting three accessible stable redox states with characteristic absorption bands in the visible spectra, corresponding to three complementary colors (i.e., green, blue and red). These absorption bands are exploited as output signals of this robust ternary electrochemical switch, behaving hence as an electrochromic molecular-based device.

Surface-confined electroactive molecules for multistate charge storage information

Bi-stable molecular systems with potential for applications in binary memory devices are raising great interest for device miniaturization. Particular appealing are those systems that operate with electrical inputs since they are compatible with existing electronic technologies. The processing of higher memory densities in these devices could be accomplished by increasing the number of memory states in each cell, although this strategy has not been much explored yet. Here we highlight the recent advances devoted to the fabrication of charge-storage molecular surface-confined devices exhibiting multiple states. Mainly, this goal has been realized immobilizing a variety (or a combination) of electroactive molecules on a surface, although alternative approaches employing non-electroactive systems have also been described. Undoubtedly, the use of molecules with chemically tunable properties and nanoscale dimensions are raising great hopes for the devices of the future in which molecules can bring new perspectives such as multistability.

Sub-50 nm positioning of organic compounds onto silicon oxide patterns fabricated by local oxidation nanolithography

We present a process to fabricate molecule-based nanostructures by merging a bottom-up interaction and a top-down nanolithography. Direct nanoscale positioning arises from the attractive electrostatic interactions between the molecules and silicon dioxide nanopatterns. Local oxidation nanolithography is used to fabricate silicon oxide domains with variable gap separations ranging from 40 nm to several microns in length. We demonstrate that an ionic tetrathiafulvalene (TTF) semiconductor can be directed from a macroscopic liquid solution (1 µM) and selectively deposited onto predefined nanoscale regions of a 1 cm(2) silicon chip with an accuracy of 40 nm.

Electrical transport measurements on self-assembled organic molecular wires

The electrical properties of supermolecular assemblies of oligo(p-phenylene vinylene) were studied. These materials self-assemble into well-defined cylindrical structures in solution with lengths in the range of 100 nm-10 microm and diameters between 5 and 200 nm. Atomic force microscopy showed that by adjusting the concentration, either individual molecular wires or a dense film could be deposited. The molecular wires showed poor electrical conduction. Several tests were performed that show that it was the molecular wires themselves, not the contacts, that limit the conductivity.

Bulk Spontaneous Magnetization in the New Radical Cation Salt TM-TTF[Cr(NCS)4(isoquinoline)2] (TM-TTF = Tetramethyltetrathiafulvalene)

A new organic-inorganic hybrid salt [TM-TTF][Cr(NCS)(4)(isoquinoline)(2)] (1) (TM-TTF = Tetramethyltetrathiafulvalene) has been synthesized. Compound 1 crystallizes in the triclinic P space group with a = 8.269(1), b = 10.211(2), and c = 11.176(2) A, alpha = 89.244(9), beta = 88.114(6), and gamma = 74.277(7) degrees, V = 907.6(3) A(3), and Z = 1. The crystal structure was resolved in the temperature range between 223 and 123 K, showing that changes in the crystal structure at low temperature result in stronger interactions between anions and cations. The packing of 1 consists of mixed anion-cation layers in the bc plane containing S.S and pi-pi anion-cation interactions, the layers being connected by very short S.S contacts between anions and cations. Magnetic measurements in a small external field show bulk spontaneous magnetization with a T(c) of 6.6 K consistent with the presence of weakly coupled ferrimagnetic order in compound 1. The EPR measurements also demonstrate the interaction between the d and pi electrons and the presence of an internal magnetic field brought about by the magnetic ordering.

Isolation and characterization of four isomers of a C(60) bisadduct with a TTF derivative. Study of their radical ions

A family of triads composed of C(60) attached by a rigid spacer to two identical TTF moieties has been synthesized, and some of the isomers have been isolated and characterized by UV-vis spectroscopy, LDI-TOF-MS, and HMBC NMR spectroscopy. AM1 semiempirical calculations of the dipolar moments and the heats of formation of the different isomers have been carried out in order to verify their assignments. Oxidation and reduction of the triads affords the derived radical ion systems, TTF(+*)-C(60)-TTF(+*) and TTF-C(60)(-*)-TTF, which were studied by EPR spectroscopy. Spin density distributions of these radical cations and radical anions show that the unpaired electron is located mainly on the TTF and fullerene moieties, respectively. However, while the EPR signals obtained from the radical cations are very similar for all the isomers, the structured signals observed for the radical anions arising from the coupling of the unpaired electron with the hydrogen atoms of the methylene bridges in the spacer show that there is a strong influence of the isomerism on the spin distribution. Importantly, the theoretical calculations of the spin density distributions of the radical anions fit well with the experimental EPR results.