“Dumbbell”‐ and “Clackers”‐Shaped Dimeric Derivatives of Monocarba‐closo‐dodecaborate

We designed, synthesized, and characterized two types of dimeric forms of monocarba‐closo‐dodecaborate, namely, a “dumbbell”‐shaped dianion having a C?C bond and a “clackers”‐shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X‐ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions.     

“Click”‐Triggered Self‐Healing Graphene Nanocomposites

Strategies to compensate material fatigue are among the most challenging issues, being most prominently addressed by the use of nano‐ and microscaled fillers, or via new chemical concepts such as self‐healing materials. A capsule‐based self‐healing material is reported, where the adverse effect of reduced tensile strength due to the embedded capsules is counterbalanced by a graphene‐based filler, the latter additionally acting as a catalyst for the self‐healing reaction. The concept is based on “click”‐based chemistry, a universal methodology to efficiently link components at ambient reaction conditions, thus generating a “reactive glue” at the cracked site. A capsule‐based healing system via a graphene‐based Cu₂O (TRGO‐Cu₂O‐filler) is used, acting as both the catalytic species for crosslinking and the required reinforcement agent within the material, in turn compensating the reduction in tensile strength exerted by the embedded capsules. Room‐temperature self‐healing within 48 h is achieved, with the investigated specimen containing TRGO‐Cu₂O demonstrating significantly faster self‐healing compared to homogeneous (Cu(PPh₃)₃F, Cu(PPh₃)₃Br), and heterogeneous (Cu/C) copper(I) catalysts.

     

“Twin” phosphorous atoms of tetraethyl 2‐methyl‐piperyd‐1‐ylmethylenebisphosphonates

Recently, bisaminophosphonates found applications as therapeutic agents for curing bone disorders. When trying to relate the structures of substituted piperid‐1‐ylmethylenebisphosphonic with their biological properties, non‐typical findings that in ³¹P NMR spectra of 2‐methyl‐piperid‐1‐ylmethylenebisphosphonic and 2‐ethyl‐piperid‐1‐ylmethylenebisphosphonic acids, two separate singlets from each of the phosphonic groups were observed, while their analogues bearing substituent in position 3 exhibit only one signal. Their presence was explained by freezing of the molecular motions by strong hydrogen bonding between NH and P = O atoms. In this work, synthesis as well as spectroscopic and theoretical investigations of the tetraethyl esters of 2‐methyl‐piperid‐1‐ylmethylenebisphosphonic in its racemic and enatiomerically pure forms are reported. Their ³¹P NMR spectra revealed two sets of dublets, which indicate the presence of two non‐equivalent phosphorous atoms. More detailed NMR and theoretical studies indicated that the nonequivalent phosphorous signals in ³¹P NMR spectra may results from the absence of C₂ symmetry of the molecule along with the presence of large ester groups blocking the internal molecular motion around C—N bond, and thus blocking the interchange of ring conformation. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:774–781, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20349     

A highly regioselective synthesis of 1‐n‐methyl‐spiro‐[2,3′“]‐oxindole‐spiro‐[3,2”]indane‐1“, 3”‐dione‐4‐arylpyrrolidines through 1,3‐dipolar cycloaddition protocol

2‐Arylidene‐1,3‐indanediones undergo a regioselective 1,3‐dipolar cycloaddition reaction with the azomethine ylide derived from isatin and sarcosine by decarboxylative route affording a series of 1‐N‐methyl — spiro[2.3′“]oxindole‐spiro[3.2”]indane‐1“,3”‐diones‐4‐aryl pyrrolidines. The structures were established by spectroscopic techniques as well as single crystal X‐ray analysis. Density functional theory at B3L YP/6‐31G^* and the semi empirical AM₁ calculations were employed to rationalize the observed results. The experimental regioselectivity of 1,3‐dipolar cycloadditions could be corroborated nicely with the computed Fukui frontier orbital energies and reaction energies.     

Crystal structures of the “two” 4‐aminofurazan‐3‐carboxylic acids

The crystal structures of the two compounds reported to be 4‐aminofurazan‐3‐carboxylic acid have been determined. The compound reported by Sheremetev et al. (J Heterocycl Chem 2005, 42, 519) is the actual 4‐aminofurazan‐3‐carboxylic acid. The compound reported by Meyer (Org Prep Proced Int 2004, 36, 361) is the interesting complex formed from a molecule of the acid and a molecule of the potassium salt of the acid. J. Heterocyclic Chem., (2012).     

One‐Step Formation of “Chain‐Armor”‐Stabilized DNA Nanostructures

DNA‐based self‐assembled nanostructures are widely used to position organic and inorganic objects with nanoscale precision. A particular promising application of DNA structures is their usage as programmable carrier systems for targeted drug delivery. To provide DNA‐based templates that are robust against degradation at elevated temperatures, low ion concentrations, adverse pH conditions, and DNases, we built 6‐helix DNA tile tubes consisting of 24 oligonucleotides carrying alkyne groups on their 3′‐ends and azides on their 5′‐ends. By a mild click reaction, the two ends of selected oligonucleotides were covalently connected to form rings and interlocked DNA single strands, so‐called DNA catenanes. Strikingly, the structures stayed topologically intact in pure water and even after precipitation from EtOH. The structures even withstood a temperature of 95 °C when all of the 24 strands were chemically interlocked.     

“Helter‐Skelter‐Like” Perylene Polyisocyanopeptides

Exciton migration! Spectroscopic analyses and extensive molecular dynamics studies revealed a well‐defined 4₁ helix in which the perylene molecules (see figure) form four “helter‐skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate.

     

Self‐Assembly of Chiral Propeller‐like Supermolecules with Unusual “Sergeants‐and‐Soldiers” and “Majority‐Rules” Effects

Chiral amplification is an interesting phenomenon in supramolecular chemistry mainly observed in complicated systems in which cooperative effect dominate. Herein, chiral, supramolecular, propeller‐like architectures have been constructed through coassembly of an achiral disk‐shaped molecule and chiral amino acid derivatives driven by intermolecular hydrogen bonding. Both the “sergeants‐and‐soldiers” principle and “majority‐rules” effect are applicable in these discrete four‐component supermolecules, which are the simplest supramolecular system ever reported that exhibit chiral amplification.