Chiral Spiro-Tetrathiafulvalenes: Synthesis, Chiroptical Properties, Conformational Issues and Charge Transfer Complexes.

Within this work we have investigated spiro-based tetrathiafulvalenes (TTFs) obtained as mixtures of stereoisomers from racemic spiro[5.5]undeca-1,8-dien-3-one. Compared to previously described spiro-TTFs, enantiomeric and diastereoisomeric forms have been here separated by chiral HPLC and fully characterized both experimentally and theoretically.

Active-metal template clipping synthesis of novel [2]rotaxanes.

Mechanically interlocked molecules (MIMs) have been important synthetic targets in supramolecular chemistry due to their beautiful structures and intriguing properties. We present herein a new synthetic strategy to access [2]rotaxanes, namely active-metal template clipping. We discuss the design of the target [2]rotaxanes, synthesis and characterization of the axle, macrocycle precursors and macrocycles as well as preparation of the final [2]rotaxanes by active template copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) as key step of the synthesis.

Planar Chiral -Terphenyl-Based Cyclophanes with Remarkable Enantiomer Stability: Synthesis, Theoretical Investigations, and Complexation Studies.

Design of conformationally stable compounds with planar chirality is a topic of great interest mainly because of their potential applications as enantioselective ligands or other functional materials. Herein, we present the design and synthesis of novel planar chiral cyclophanes, obtained by anchoring of the -terphenyl unit, with bridges of different lengths and rigidities, along with their nuclear magnetic resonance, mass spectrometry, and X-ray characterizations. We investigated the influence of the structural particularities of the bridges over the stability of the enantiomers, by means of nuclear magnetic resonance and chiral high-performance liquid chromatography as well as by density functional theory calculations.

Exploring the Optoelectronic Properties of D-A and A-D-A 2,2'-bi[3,2-]thienothiophene Derivatives.

The synthesis of some novel donor-acceptor and acceptor-donor-acceptor systems containing a 2,2'-bi[3,2-]thienothiophene donor block and various electron-accepting units is described alongside their photophysical properties studied using electrochemistry, optical spectroscopy and theoretical calculations. The obtained results show that the energy levels can be modulated by changing the strength of the acceptor unit. Among the three investigated end-groups, 1,1-dicyanomethylene-3-indanone exhibited the largest bathochromic shift and the lowest band gap suggesting the strongest electron-withdrawing character.

Chiral Bis(tetrathiafulvalene)-1,2-cyclohexane-diamides.

Chiral bis(TTF) diamides have been obtained in good yields (54-74%) from 1,2-cyclohexane-diamine and the corresponding TTF acyl chlorides. The (,)- and (,)- enantiomers have been characterized by circular dichroism and the racemic form by single-crystal X-ray diffraction. The neutral racemic bis(TTF)-diamide shows the formation of a pincer-like framework in the solid state, thanks to the intramolecular SS interactions.

An attempt to synthesize a terthienyl-based analog of indacenedithiophene (IDT): unexpected synthesis of a naphtho[2,3-]thiophene derivative.

We report herein our attempt to synthesize an analog of indacenedithiophene (IDT) based on a tetraphenylhexyl substituted, covalently bridged -terthienyl unit. Instead of the expected compound the adopted synthetic route led to the formation of an unexpected, new naphtho[2,3-]thiophene derivative. The structure of this compound was fully characterized by NMR and HRMS as well as single crystal X-ray diffraction and its electronic properties have been analyzed by UV-vis absorption spectroscopy and cyclic voltammetry.

Effect of the Terminal Acceptor Unit on the Performance of Non-Fullerene Indacenodithiophene Acceptors in Organic Solar Cells.

Four acceptor-donor-acceptor (A-D-A)-type molecules bearing indacenodithiophene as donating central core and various end-capping acceptor units have been designed and synthesised as -type materials suitable for organic solar cells (OSCs). The studied optical and electrochemical properties supported by theoretical calculations revealed that the nature and the strength of the terminal groups exert a decisive influence on the polymer bulk-heterojunction OSC performance.

Sonogashira Synthesis of New Porous Aromatic Framework-Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling.

Palladium nanoparticles entrapped in porous aromatic frameworks (PAFs) or covalent organic frameworks may promote heterogeneous catalytic reactions. However, preparing such materials as active nanocatalysts usually requires additional steps for palladium entrapment and reduction. This paper reports as a new approach, a simple procedure leading to the self-entrapment of Pd nanoparticles within the PAF structure.

Solid-State and Theoretical Investigations of Some Banister-Type Macrocycles with 2,2'-Aldoxime-1,1'-Biphenyl Units.

In the context of helical chirality, bridging of biphenyl units leads to banister-type compounds and the stability of the resulted atropisomers may increase dramatically if suitable changes are performed in the linker unit that coils around the biphenyl moiety. A rigorous density functional theory (DFT) study was conducted for macrocycles containing rigid oxime ether segments connected to the biphenyl backbone in order to determine how the rotation barriers are influenced by the presence of either a flexible oligoethyleneoxide or a more rigid -xylylene component in the macrocycle. The calculated values for the racemization barrier were in good agreement with those obtained experimentally and confirm the benefit of introducing a more rigid unit in the macrocycle on the stability of atropisomers.

Synthesis, Structure and Supramolecular Properties of a Novel C3 Cryptand with Pyridine Units in the Bridges.

The high-yield synthesis and the structural investigation of a new cryptand with C3 symmetry, exhibiting 2,4,6-triphenyl-1,3,5-triazine central units and pyridine-based bridges, are reported. The structure of the compound was investigated by single crystal X-ray diffractometry, NMR (nuclear magnetic resonance), HRMS (high resolution mass spectrometry) measurements, and theoretical calculations. The study of supramolecular behavior in solid state revealed the association of cryptand molecules by C-H---π and π---π contacts.

The Dawn of Single Material Organic Solar Cells.

Single material organic solar cells (SMOSCs) are based on ambivalent materials containing electron donor (D) and acceptor (A) units capable to ensure the basic functions of light absorption, exciton dissociation, and charge transport. Compared to bicomponent bulk heterojunctions, SMOSCs present several major advantages such as considerable simplification of cell fabrication and a strong stabilization of the morphology of the D/A interface, and thus of the cell lifetime. In addition to these technical issues, SMOSCs pose fundamental questions regarding the possible formation, and dissociation of excitons on the same molecular D-A architecture.

A three-armed cryptand with triazine and pyridine units: synthesis, structure and complexation with polycyclic aromatic compounds.

The aromatic nucleophilic substitution reaction based synthesis of a three-armed cryptand displaying 2,4,6-triphenyl-1,3,5-triazine units as caps and pyridine rings in the bridges, along with NMR, MS and molecular modelling-based structural analysis of this compound are reported. Appropriate NMR and molecular modelling investigations proved the formation of 1:1 host-guest assemblies between the investigated cryptand and some polynuclear aromatic hydrocarbons or their derivatives.

"Click" access to multilayer functionalized Au surface: A terpyridine patterning example.

This work is focused on self-assembled monolayers (SAMs) fabrication, using two types of Au surfaces, by subsequent attachment of different layers in order to develop a stable platform consisting of covalent multilayer functionalized gold surfaces. The key step in the construction of SAMs is the covalent linkage to the gold surface, via an amino-thiol derivative, of a cyclooctyne unit exhibiting strained triple bonds which react fast (catalysts are not needed) and quantitatively with organic azides and enable the introduction of various chemical functionalized entities on the gold surface. The versatility of the system is demonstrated by the reaction of the cyclooctyne decorated gold surface with an azide functionalized terpyridine followed by step by step complexation with Fe(II) and another terpyridine unit resulting into a multilayer covered gold surface.

Modulating short tryptophan- and arginine-rich peptides activity by substitution with histidine.

Background: High antimicrobial efficacy of short tryptophan-and arginine-rich peptides makes them good candidates in the fight against pathogens. Substitution of tryptophan and arginine by histidine could be used to modulate the peptides efficacy by optimizing their structures.

Methods: The peptide (RRWWRWWRR), reported to showed good antimicrobial efficacy, was used as template, seven new analogs being designed substituting tryptophan or arginine with histidine.

Supramolecular anion recognition by β-HCH.

The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion contacts between β-HCH and various anions (Cl, Br, I and HSO) was investigated by single crystal X-ray diffractometry, molecular modelling, ESI-MS and H-NMR titrations.

Indenopyrans - synthesis and photoluminescence properties.

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

Supramolecular rulers enabling selective detection of pure short ssDNA via chiral self-assembly.

Multivalent self-assembly of trifunctional aromatic propellers and ssDNA results in the formation of chiral supramolecular assemblies that can be used for the detection of small fragments of ssDNA with different lengths and compositions.

Exclusive Hydrophobic Self-Assembly of Adaptive Solid-State Networks of Octasubstituted 9,9'-Spirobifluorenes.

An easy and powerful access to 3,3',6,6'-tetrasubstituted 9,9'-spirobifluorene derivatives with tetrahedral orientation of the peripheral groups (i.e., -I, -CN, -NO2, -CH═O, -COOH, -C≡CH, -4-Py) was developed.

Simple and versatile molecular donors for organic photovoltaics prepared by metal-free synthesis.

Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers (1-5) were synthesized from mono- or dialdehydes by a simple metal-free procedure. Cyclic voltammetry and UV/Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3 show a broadening and red shift of the absorption bands, consistent with the formation of J-aggregates.

Small molecular donors for organic solar cells obtained by simple and clean synthesis.

A small donor-acceptor molecule is synthesized in a two-step procedure involving reaction of N,N-diphenylhydrazine on 2,5-diformylthiophene and Knoevenagel condensation. Results of UV/Vis absorption spectroscopy and cyclic voltammetry show that replacement of the phenyl ring bridge of a reference compound 2 by an azo group produces a slight red-shift of λmax, an enhancement of the molecular absorption coefficient, and a decrease of the energy level of the frontier orbitals. A preliminary evaluation of the potentialities of compound 1 as donor material in a basic bilayer planar heterojunction cell of 28 mm(2) active area using C60 as acceptor gave a short-circuit current density of 6.

Self-sorting of dynamic metallosupramolecular libraries (DMLs) via metal-driven selection.

"Metal-driven" selection between finite mononuclear and polymeric metallosupramolecular species can be quantitatively achieved in solution and in a crystalline state via coupled coordination/stacking interactional algorithms within dynamic metallosupramolecular libraries - DMLs.

Cryptands with 1,3,5-tris(1',3'-dioxan-2'-yl)-benzene units: synthesis and structural investigations.

Various cryptands based on 1,3-dioxane decorated 1,3,5-trisubstituted-benzene building blocks, connected by different chains (exhibiting ester, ether, or triazol groups) to several units with C3 symmetry, are reported. The structure of the compounds was investigated by single crystal X-ray diffraction, NMR, and MS. The role of the 1,3-dioxane units was targeted to ensure the preorganization of the substrate for the macrocyclization reactions on one side, and for easier NMR assignment of the structure of the cryptands on the other side.

(3-Chloro-phen-yl){2-eth-oxy-5-[(Z)-hydroxy(phen-yl)methyl-idene]cyclo-penta-1,3-dien-1-yl}methanone.

The title compound, C(21)H(17)ClO(3), which crystallizes as one of two possible oxo/hy-droxy-fulvene prototropic tautomers, possesses a strong intra-molecular O-H⋯O hydrogen bond that closes a seven-membered ring. The dihedral angles between the central five-membered ring and two pendant rings are 55.05 (9) and 44.

Regioselective orthopalladation of (Z)-2-aryl-4-arylidene-5(4H)-oxazolones: scope, kinetico-mechanistic, and density functional theory studies of the C-H bond activation.

Orthopalladated complexes derived from (Z)-2-aryl-4-arylidene-5(4H)-oxazolones have been prepared by reaction of the oxazolone with palladium acetate in acidic medium. The reaction is regioselective, only the ortho C-H bond of the arylidene ring being activated, producing a six-membered ring. The scope and reaction conditions of the orthopalladation are dependent on the acidity of the solvent.

Molecular modeling of phenothiazine derivatives: self-assembling properties.

This study aims to present a detailed theoretical investigation of noncovalent intermolecular interactions between different π-π stacking phenothiazine derivatives and between different alkane chains varying from propane to decane. Second-order Møller-Plesset perturbation (MP2), coupled cluster (CC), and density functional (DFT) theories were the quantum chemistry methods used in our calculation. For MP2 and CC methods, the density-fitting and local approximations were taken into account, while in the case of DFT, the M06 and M06-2x hybrid meta-GGA exchange-correlation functionals as well as the semiempirical correction to the DFT functional for dispersion (BLYP-D) was considered.