Designing supramolecular liquid-crystalline hybrids from pyrenyl-containing dendrimers and arene ruthenium metallacycles

YesThe association of the arene ruthenium metallacycle [Ru4(p-cymene)4(bpe)2(donq)2][DOS]4 (bpe = 1,2-bis(4-pyridyl)ethylene, donq = 5,8-dioxydo-1,4-naphtoquinonato, DOS = dodecyl sulfate) with pyrenyl-functionalized poly(arylester) dendrimers bearing cyanobiphenyl end-groups is reported. The supramolecular dendritic systems display mesomorphic properties as revealed by polarized optical microscopy, differential scanning calorimetry and small-angle X-ray scattering measurements. The multicomponent nature of the dendrimers and of the corresponding host–guest supramolecules (i.e., end-group mesogens, dendritic core, pyrene unit, aliphatic spacers, and metallacycle) leads to the formation of highly segregated mesophases with a complex multilayered structure due to the tendency of the various constitutive building-blocks to separate in different organized zones. The pyrenyl dendrimers exhibit a multilayered smectic A-like phase, thereafter referred to as LamSmA phase to emphasize this unaccustomed morphology. As for the corresponding Ru4–metallacycle adducts, they self-organize into a multicontinuous thermotropic cubic phase with the Im3̅m space group symmetry. This represents a unique example of liquid-crystalline behavior observed for such large and complex supramolecular host–guest assemblies. Models of their supramolecular organizations within both mesophases are proposed.R.D. thanks the Swiss National Science Foundation (Grant No 200020-140298) for financial support

In quest of a systematic framework for unifying and defining nanoscience

This article proposes a systematic framework for unifying and defining nanoscience based on historic first principles and step logic that led to a “central paradigm” (i.e., unifying framework) for traditional elemental/small-molecule chemistry. As such, a Nanomaterials classification roadmap is proposed, which divides all nanomatter into Category I: discrete, well-defined and Category II: statistical, undefined nanoparticles. We consider only Category I, well-defined nanoparticles which are >90% monodisperse as a function of Critical Nanoscale Design Parameters (CNDPs) defined according to: (a) size, (b) shape, (c) surface chemistry, (d) flexibility, and (e) elemental composition. Classified as either hard (H) (i.e., inorganic-based) or soft (S) (i.e., organic-based) categories, these nanoparticles were found to manifest pervasive atom mimicry features that included: (1) a dominance of zero-dimensional (0D) core–shell nanoarchitectures, (2) the ability to self-assemble or chemically bond as discrete, quantized nanounits, and (3) exhibited well-defined nanoscale valencies and stoichiometries reminiscent of atom-based elements. These discrete nanoparticle categories are referred to as hard or soft particle nanoelements. Many examples describing chemical bonding/assembly of these nanoelements have been reported in the literature. We refer to these hard:hard (H-n:H-n), soft:soft (S-n:S-n), or hard:soft (H-n:S-n) nanoelement combinations as nanocompounds. Due to their quantized features, many nanoelement and nanocompound categories are reported to exhibit well-defined nanoperiodic property patterns. These periodic property patterns are dependent on their quantized nanofeatures (CNDPs) and dramatically influence intrinsic physicochemical properties (i.e., melting points, reactivity/self-assembly, sterics, and nanoencapsulation), as well as important functional/performance properties (i.e., magnetic, photonic, electronic, and toxicologic properties). We propose this perspective as a modest first step toward more clearly defining synthetic nanochemistry as well as providing a systematic framework for unifying nanoscience. With further progress, one should anticipate the evolution of future nanoperiodic table(s) suitable for predicting important risk/benefit boundaries in the field of nanoscience

Observation of microscopic patterning at the air water interface by mixtures of amphiphilic cyclodextrins: a compression isotherm and Brewster angle microscopy study

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