Diastereoisomerically Pure Fulleropyrrolidines as Chiral Platforms for the Design of Optically Active Liquid Crystals

Click synthesis of dendronized malonates for the preparation of amphiphilic dendro[60]fullerenes

Fullerene C60 and its malonate derivatives, produced via the Bingel-Hirsch reaction, have displayed promising properties against various diseases. These molecules have great therapeutic potential, but their broad use has been limited due to poor aqueous solubility and toxicity caused by accumulation. In this study, we synthesized new malonates and malonamides attached to first- and second-generation polyester dendrons using click chemistry (CuAAC). These dendrons were then linked at C60 through the Bingel-Hirsch reaction, resulting in an amphiphilic system that retains the hydrophobic nature of C60. The dendronized malonate derivatives showed good reaction yields for the Bingel-Hirsch mono-adducts and were easier to work with than the corresponding malonamides. However, the malonamide derivatives, which were obtained through a multistep reaction sequence, showed moderate yields in the Bingel-Hirsch reaction. Surprisingly, removing acetonide protecting groups from dendritic architectures was more challenging than anticipated, likely due to product decomposition. Only the corresponding free malonate derivatives 25 and 26 were obtained, but in a low yield due to decomposition under the reaction conditions. Meanwhile, it was not possible to obtain the corresponding malonamide derivatives 27 and 28. Currently, efforts are being made to improve the production of the desired molecules and to design new synthesis routes that allow direct access to the desired poly-hydroxylated derivatives. These derivatives will be evaluated as multitarget ligands against Alzheimer's disease, through their use as inhibitors of amyloid β-peptide aggregation, acetylcholinesterase modulators, and antioxidants.

Tuning the Liquid Crystallinity of Cholesteryl-o-Carborane Dyads: Synthesis, Structure, Photoluminescence, and Mesomorphic Properties

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired trans-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (M2), Me (M3), or Ph (M4)) to one of the carbon atoms of the o-carborane cluster (Ccluster) enables the tailoring of liquid crystalline properties. Compounds M2 and M3 show the chiral nematic (N*) phase, whereas M4 do not show liquid crystal behavior. Weaker intermolecular interactions in the solid M3 with respect to those in M2 may allow the liquid crystallinity in M3 to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of M2 leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, M3 also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (M5) without an o-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (M2 and M3), the o-carborane cluster can be incorporated without destroying the helical organization of the mesophase.

Supramolecular Arene-Ruthenium Metallacycle with Thermotropic Liquid-Crystalline Properties

Functionalization of 1,4-di(4-pyridinyl)benzene with poly(arylester) dendrimers bearing cyanobiphenyl end-groups gives a bidentate dendromesogenic ligand (L) that exhibits thermotropic liquid-crystalline properties. Combination of the diruthenium complex [Ru₂(p-cymene)₂(donq)][DDS]₂ (M) with L, by coordination-driven self-assembly, affords the discrete and well-defined metallacycle M₂L₂. Like L, this supramolecular dendritic system displays mesomorphic properties above 50 °C. Both compounds L and M₂L₂ show smectic phases, characterized by a multilayered organization of the multiple components.

Controlling the enthalpy–entropy competition in supramolecular fullerene liquid crystals by tuning the flexible chain length

The supramolecular fullerene liquid crystal phase and structure can be regulated by controlling the enthalpy–entropy competition by tuning the flexible chain length.

Synthesis and self-assembly properties of fullerene/porphyrin-phthalocyanine and fullerene/bis-phthalocyanine triads

In this work, we report on the synthesis and characterization of two fulleropyrrolidines bearing porphyrin/phthalocyanine and bis-phthalocyanine tweezers. The self-assembly properties in different solvents have been investigated by AFM and SEM. When deposited on surface from dichloromethane solutions, the fullerene derivatives formed aggregates of ca. 4–8 nm in height while hollow nanospheres with diameters of ca. 300–1000 nm are obtained from crystallization attempts.

Fullerene–Pyrrolidine Biferrocene Donor–Acceptor Triads: Synthesis and Effects of Fullerene[60] on the Electronic Communication of the Two Ferrocene Units in Biferrocene

A novel nanoscale molecule, fullerene[60]-based biferrocene (C60-ph-Fc-Fc), was prepared via covalent grafting of biferrocene onto C60 using 1,3-dipolar cycloaddition and was fully characterized by mass spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, ultraviolet-visible spectroscopy, and fluorescence spectroscopy. Cyclic voltammetry studies showed that C60-ph-Fc-Fc undergoes four successive quasi-reversible processes in the potential window of –2.0~0.40 V (versus Fc+/Fc). The biferrocene (moiety) exhibited significant electronic communication between the two ferrocenyl groups both before and after grafting onto C60. Grafting of fullerene led to weakening in the electronic interaction, and the comproportionation constant decreased by nearly five orders of magnitude from 1.56 × 106 for Fc-Fc to 88 for C60-ph-Fc-Fc, indicating that the electronic communication between halves of the biferrocene could be effectively modified by grafting of C60. The temperature-dependent magnetic susceptibility (2–300 K) study showed that there was a strong antiferromagnetic interaction between the ferrocene FeII centres.

Self-organisation of dodeca-dendronized fullerene into supramolecular discs and helical columns containing a nanowire-like core

Twelve chiral and achiral self-assembling dendrons have been grafted onto a [60]fullerene hexa-adduct core by copper-catalyzed alkyne azide "click" cycloaddition. The structure adopted by these compounds was determined by the self-assembling peripheral dendrons. These twelve dendrons mediate the self-organisation of the dendronized [60]fullerene into a disc-shaped structure containing the [60]fullerene in the centre. The fullerene-containing discs self-organise into helical supramolecular columns with a fullerene nanowire-like core, forming a 2D columnar hexagonal periodic array. These unprecedented supramolecular structures and their assemblies are expected to provide new developments in chiral complex molecular systems and their application to organic electronics and solar cells.

Synthesis and study of hybrid hydrogen-bonded bent-core liquid crystal complexes containing C60- and Si-based proton donors

Mesophasic and electro-optical properties can be manipulated via the ratio of Si- and C₆₀-based moieties in H-bonded bent-core LC complexes.

A strongly emitting liquid-crystalline derivative of Y(3)N@C(80): bright and long-lived near-IR luminescence from a charge transfer state

Great balls of fire: C60 and Y3 N@C80 were connected to the same oligo(phenyleneethynylene) unit to investigate their structural and photophysical properties. NMR investigations revealed a fulleroid structure for the Y3 N@C80 derivative, and both dyads gave rise to columnar phases with core-shell cylinders. The black and gray spheres represent the fullerene core units of the Y3 N@C80 derivative, which is an ideal candidate to be involved in energy and electron transfer processes.

Self-assembling porphyrins and phthalocyanines for photoinduced charge separation and charge transport

Large π-conjugated compounds are promising building blocks for organic thin-film electronics such as organic light-emitting diodes, organic field-effect transistors, and organic photovoltaics. Utilization of porphyrins and phthalocyanines for this purpose is highly fascinating because of their excellent electric, photophysical, and electrochemical properties as well as intense self-assembling abilities arising from π-π stacking interactions. This paper focuses on fundamental aspects of self-assembled structures that have been obtained from porphyrin and phthalocyanine building blocks and more complex composites for photoinduced charge separation and charge transport toward the potential applications to organic thin-film electronics.

Segregated donor-acceptor columns in liquid crystals that exhibit highly efficient ambipolar charge transport

Liquid crystalline donor (i.e., phthalocyanine) was covalently linked to acceptor (i.e, fullerene) to achieve efficient charge-transport properties in a liquid crystalline phase. The columnar structure exhibited highly efficient ambipolar charge-transport character, demonstrating the potential utility of the strategy in organic electronics.

Accordion-optimized DEPT experiments

In this contribution, a pulse sequence is described for recording accordion-optimized DEPT experiments. The proposed ACCORDEPT experiment detects a wide range of one-bond coupling constants using accordion optimization. As a proof of concept, this strategy has been applied to a mesogen containing a large range of one-bond (1)J(CH) coupling constants associated with the various structural elements. The ACCORDEPT experiment afforded significant enhancements for the resonances with the larger (1)J(CH) couplings, similar SNR for aliphatic resonances, but reduced SNR for aliphatic resonances as compared with the standard DEPT experiment. In addition, the ACCORDEPT is straightforward to implement, does not require any supplementary calibration procedures and can be used under automated conditions without difficulty by inexperienced users.