François Diederich (1952-2020): 40 Years of Organic Chemistry.

François Diederich, Professor of Organic Chemistry and long-time Chair of the Editorial Board of Angewandte Chemie, sadly passed away on September 23, 2020. He will be remembered for his groundbreaking research in the chemistry of fullerenes and carbon-rich molecules, in supramolecular and medicinal chemistry, as an engaging teacher, and as a generous and fascinating human being.

Evaluation of the Chemistry Knowledge of Students Entering the ETH Zurich with a Moodle Quiz.

The basic chemistry knowledge of first-year students in the disciplines Chemistry, Biology, Pharmaceutical Sciences, and Health Sciences and Technology has been evaluated within the first three weeks of the Fall semester with a Moodle-based quiz at ETH Zurich. It consists of 37 small problems testing the knowledge that ETH students entering the lecture courses General Chemistry 1 (Inorganic Chemistry) (AC1) and Organic Chemistry 1 (OC1) should ideally have. An initial set of questions was developed by Bernhard Jaun (ETH Zurich) in 2007, it was combined with questions from an evaluation created in 2015 by Markus Müller (secondary school II teacher). The results of a total of 925 students who took part in the 2016 and 2017 evaluations are presented. It was found that 80% of the students of Chemistry, Chemical Engineering and Interdisciplinary Natural Sciences (AC1 course) and 70% of the students of Biology, Pharmaceutical Sciences, and Health Sciences and Technology (OC1 course) scored ≥60%. Students who took the focus course (Schwerpunktfach) Biology and Chemistry at the SEK II level (Swiss school system) performed on average 13-18% better and with a smaller standard deviation than other students. No significant differences were observed with regard to gender or the region in which the qualification for university entrance was obtained.

Challenges in Creating Online Exercises and Exams in Organic Chemistry.

e-Learning has become increasingly important in chemical education and online exams can be an attractive alternative to traditional exams written on paper, particularly in classes with a large number of students. Ten years ago, we began to set up an e-course complementing our lecture courses Organic Chemistry I and II within the open-source e-learning environment Moodle. In this article, we retrace a number of decisions we took over time, thereby illustrating the challenges one faces when creating online exercises and exams in (organic) chemistry. Special emphasis is put on the development of MOSFECCS (MOlecular Structural Formula Editor and Calculator of Canonical SMILES), our new editor for drawing structural formulae and converting them to alphanumeric SMILES codes that can be submitted as answers to e-problems. Convinced that the possibility for structure input is essential to set up sensible chemistry quizzes and exams, and realising that existing tools present major flaws in an educational context, we decided to embark on the implementation of MOSFECCS which takes into account a number of didactic aspects.

Adsorbate-Induced Modification of the Confining Barriers in a Quantum Box Array.

Quantum devices depend on addressable elements, which can be modified separately and in their mutual interaction. Self-assembly at surfaces, for example, formation of a porous (metal-) organic network, provides an ideal way to manufacture arrays of identical quantum boxes, arising in this case from the confinement of the electronic (Shockley) surface state within the pores. We show that the electronic quantum box state as well as the interbox coupling can be modified locally to a varying extent by a selective choice of adsorbates, here C60, interacting with the barrier. In view of the wealth of differently acting adsorbates, this approach allows for engineering quantum states in on-surface network architectures.

Heat-induced formation of one-dimensional coordination polymers on Au(111): an STM study.

The formation of one-dimensional coordination polymers of cyano-substituted porphyrin derivatives on Au(111) induced by thermal annealing is demonstrated by means of scanning tunnelling microscopy. The polymer is stabilised by an unusual threefold coordination motif mediated between an Au atom and the cyano groups of the porphyrin derivatives.

Chirality transfer in 1D self-assemblies: influence of H-bonding vs metal coordination between dicyano[7]helicene enantiomers.

Chiral recognition as well as chirality transfer in supramolecular self-assembly and on-surface coordination is studied for the enantiopure 6,13-dicyano[7]helicene building block. It is remarkable that, with this helical molecule, both H-bonded chains and metal-coordinated chains can be formed on the same substrate, thereby allowing for a direct comparison of the chain bonding motifs and their effects on the self-assembly in experiment and theory. Conformational flexure and both adsorbate/adsorbent and intermolecular interactions can be identified as factors influencing the chiral recognition at the binding site. The observed H-bonded chains are chiral, however, the overall appearance of Cu-coordinated chains is no longer chiral. The study was performed via scanning tunneling microscopy, X-ray-photoelectron spectroscopy and density functional theory calculations. We show a significant influence of the molecular flexibility and the type of bonding motif on the chirality transfer in the 1D self-assembly.

Synthesis of geodesic polynuclear arenes and fullerenes by intramolecular aryl-aryl coupling.

Bending over backwards to build buckybowls and -balls? For the last two decades, flash vacuum pyrolysis of chloro- and bromoarenes has been the method of choice for intramolecular aryl-aryl couplings that afford geodesic polynuclear arenes ("buckybowls") including fullerene C(60). Recently, even fluoroarenes were subjected under relatively mild conditions to intramolecular C(Ar)-C(Ar) couplings by combining the cleavage of C(Ar)-F with the formation of very strong Si-F or Al-F bonds (see picture; green C, white H).

Self-assembly and two-dimensional spontaneous resolution of cyano-functionalized [7]helicenes on Cu111.

Birds of a feather flock together: STM and DFT studies provide the first example of spontaneous chiral resolution of a helicene on a surface. Racemic 6,13-dicyano[7]helicene forms fully segregated domains of pure enantiomers (2D conglomerate) on Cu(111). The propensity of the system to optimize intermolecular CN⋅⋅⋅HC(Ar) hydrogen bonding and CN⋅⋅⋅CN dipolar interactions translates into chiral recognition with preferential assembly of homochiral molecules.

Supramolecular synthons on surfaces: controlling dimensionality and periodicity of tetraarylporphyrin assemblies by the interplay of cyano and alkoxy substituents.

The self-assembly of three porphyrin derivatives was studied in detail on a Cu(111) substrate by means of scanning tunneling microscopy (STM). All derivatives have two 4-cyanophenyl substituents in diagonally opposed meso-positions of the porphyrin core, but differ in the nature of the other two meso-alkoxyphenyl substituents. At coverages below 0.8 monolayers, two derivatives form molecular chains, which evolve into nanoporous networks at higher coverages. The third derivative self-assembles directly into a nanoporous network without showing a one-dimensional phase. The pore-to-pore distances for the three networks depend on the size and shape of the alkoxy substituents. All observed effects are explained by 1) different steric demands of the alkoxy residues, 2) apolar (mainly dispersion) interactions between the alkoxy chains, 3) polar bonding involving both cyanophenyl and alkoxyphenyl substituents, and 4) the entropy/enthalpy balance of the network formation.

Evidence for the formation of singly bonded dimers during the reductive electrochemistry of methanofullerenes.

Four methanofullerene derivatives, with phosphonate or sulfone groups attached to a C(60) core through a Bingel procedure, were synthesized to probe their stability upon electrolytic reduction. Derivatives 1 and 2 are the most stable upon electroreduction and do not exhibit retro-cyclopropanation reactions until more than three electrons per C(60) derivative are transferred. The cyclopropane ring is then removed and C(60)(>CH(2))(n) (n=1-3) products result from reactions of the trianion of C(60) with the solvent, CH(2)Cl(2). The situation with diphosphonate 3 or phosphonatecarboxylate 4 is dramatically different. For 3, quantitative retro-cyclopropanation occurs when 2.8 e(-) per molecule are transferred. In the case of 4, when more than two electrons per molecule are transferred, there is evidence of the reversible formation of a very stable intermediate, which is oxidized at a potential 500 mV more positive than the first fullerene-based reduction of the parent compound. Electrolysis of a simple C(70)-Bingel monoadduct (5) also exhibits the formation of a similar intermediate. On the basis of cyclic voltammetry, ESR spectroscopy, and MALDI analysis of products, the intermediate observed during the electrolysis of compounds 4 and 5 is assigned to a dimeric structure.

Fullerene anions of different sizes and shapes: a 13C NMR and density-functional study.

A combined experimental and theoretical study was conducted on numerous higher fullerene anions with different sizes and shapes, C76-D2, C78-C2v, C78-D3, C84-D2, and C84-D2d. The corresponding fullerenes were reduced by lithium metal to diamagnetic multiply charged anions. The centers of gravity of the 13C NMR spectra of all the multiply charged anions were deshielded, relative to those of the neutral fullerenes. The results of density functional (DFT) computations of the 13C NMR spectra and the molecular orbitals (MOs) of possible polyanion reduction products suggest that hexaanions were the species formed.

An insight into the aromaticity of fullerene anions: experimental evidence for diamagnetic ring currents in the five-membered rings of C(60)(6-) and C(70)(6-).

Reduction of the two "closed" [6,6] methanofullerenes, [6,6]C(61)H(2) (1) and [6,6]C(71)H(2) (5), to the corresponding hexaanions with lithium metal causes the bridgehead-bridgehead bonds to open, at least partially, and this change gives rise to diamagnetic ring currents in the resulting homoconjugated six-membered rings (6-MRs). These new ring currents shield the overlying hydrogen atoms on the methylene bridge and induce upfield shifts of 1.60 and 0.11 ppm in their (1)H NMR resonances, respectively. Analogous reduction of the already "open" [5,6]methanofullerenes, [5,6]C(61)H(2) (2) and [5,6]C(71)H(2) (3 and 4), only slightly enhances the shielding of the hydrogen atoms over the homoconjugated 6-MRs (upfield shifts of 0.13, 0.68, and 0.14 ppm, respectively) but leads to exceptionally strong diamagnetic ring currents in the homoconjugated five- membered rings (5-MRs), as evidenced by dramatic shielding of the hydrogen atoms situated over them (upfield shift of 5.01, 6.78, and 1.63 ppm, respectively). The strongest shielding is seen for the hydrogen atom sitting over the 5-MR at the pole of C(71)H(2)(6)(-) (delta = -0.255 ppm) indicating that the excess charge density is concentrated at the poles.

Chemistry of C84 : Separation of Three Constitutional Isomers and Optical Resolution of D2 -C84 by Using the "Bingel-Retro-Bingel" Strategy.

The pure enantiomers of D2 -C84 as well as a third constitutional isomer of this higher fullerene were produced by a retro-Bingel reaction on the first organic derivatives of C84 (see scheme). These derivatives were synthesized by Bingel cyclopropenation of C84 , separated, and unambiguously structurally characterized.