Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.

https://iopscience.iop.org/article/10.1088/0034-4885/75/1/016601/pdf

Droplet based microfluidics

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects in the form of non-hexagonal rings in such networks cause distortions away from planarity. Herein we report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chemical methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal X-ray crystallography. An independent synthetic route to a freely soluble derivative of this new type of 'nanocarbon' is also reported. Experimental data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.

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A grossly warped nanographene and the consequences of multiple odd-membered-ring defects

This review summarizes recent advances in the chemistry of curved aromatic molecules. By focusing on the key accomplishments of the last decade, we provide a general overview of synthetic methods capable of efficient induction of internal strain in π-conjugated frameworks. The review is structured according to the topology change involved in the strain-inducing reaction step (cyclizations, eliminations, ring expansions and contractions), and highlights the striking diversity of structures achievable with modern synthetic methodology.

Bowls, Hoops, and Saddles: Synthetic Approaches to Curved Aromatic Molecules

Reported here are two types of curved π-molecules that are π-isoelectronic to planar hexabenzocoronene (HBC) but are forced out of planarity either by an embedded seven-membered ring or by atom crowding at the fjord region. Embedding a heptagon in HBC leads to a novel saddle-shaped molecule 1, whose π-backbone is slightly less curved than the previously reported [7]circulene in terms of the average Gauss curvature, but surprisingly much more rigid than [7]circulene. Overcrowded fjord regions in novel derivatives of hexabenzoperylene (HBP) 2a,b lead to both chiral twisted and antifolded conformers. The successful synthesis of 1 and 2a,b is related to introducing alkoxyl groups to unprecedented positions of hexaphenylbenzenes. It is found that the red twisted isomer of 2b isomerizes at elevated temperature to the yellow anti-folded conformer. This finding along with the study on the thermodynamics and kinetics of the thermal isomerization has improved the early understandings on the conformation of HBP. In ...

Curved Polycyclic Aromatic Molecules That Are π-Isoelectronic to Hexabenzocoronene

The presence of nonhexagonal rings in an otherwise graphitic lattice induces curvature. Pentagons are common—twelve pentagons surrounded by hexagons make up C60. Larger rings are present in Stone–Wales defects, and the polyhedral formula of Euler mandates their existence in carbon nanotube Y-junctions. Except for a single, partially saturated example, four-membered rings in graphitic structures are, however, unknown. The smallest examples of these graphitic structures are the [n]circulenes, wherein a central n-sided polygon is surrounded by n-fused benzenoid rings. [7]Circulene, first prepared by Yamamoto, Nakazaki, and coworkers in 1983, is saddle shaped. [6]Circulene, or coronene, is the trivial, planar case, and it was first synthesized by Scholl andMeyer in 1932 but also occurs naturally. [5]Circulene, or corannulene, comprises 1/3 of the C60 skeleton and has been intensely studied, and it was first prepared by Lawton and Barth in 1971. Whereas a few pioneering attempts have been reported, [4]circulene has never been synthesized before. We report herein the preparation and characterization of a stable [4]circulene. By analogy with Lawton s naming of corannulene (Latin: cor, heart; annula, ring), we suggest the trivial name quadrannulene (Latin: quadra, square; annula, ring) for the [4]circulene parent. Hence, we name this derivative 1,8,9,16-tetrakis(trimethylsilyl)tetra-cata-tetrabenzoquadrannulene, abbreviated TMS4-TBQ. The IUPAC name and atom numbering are given in the Supporting Information. Our unoptimized five-step synthesis (Scheme1) provides TMS4-TBQ in very low yield. Hopf and co-workers recently summarized two synthetic strategies to the quadrannulene core: making the four-membered ring from [2,2]-paracyclo-

/pdf/quadrannulene-a-nonclassical-fullerene-fragment-4h6dqaj7e4.pdf

Stephen M. Spain

Papers

Quadrannulene: A Nonclassical Fullerene Fragment†

Highly efficient conversion of terpenoid biomass to jet-fuel range cycloalkanes in a biphasic tandem catalytic process

Cover Picture: Quadrannulene: A Nonclassical Fullerene Fragment (Angew. Chem. Int. Ed. 2/2010)