Bicyclo[1.1.1]pentanes, [n]Staffanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.0^2,5]pentanes

Abstract

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Silicon Compounds with Inverted Geometry around Silicon Atoms

“…20 The 29 Si resonance due to the central silicon without substituents appeared at ¹124.8 ppm. The most striking structural feature disclosed by X-ray analysis is that the geometry around the central silicon Si5 is very far from a typical tetrahedral geometry (Figure 5a ]pentasilane with symmetric structure similar to that of 5 (5 H ) is predicted to be a transition state of degenerate rearrangement between charge-separated unsymmetric structures (5¤ H ) (Scheme 2), 21 while the transition state is found to turn to the local minimum with increasing steric bulkiness of substituent R on the silicon framework such as 2,6-(i-Pr) 2 Figure 4. Selected bond lengths (¡) and angles (deg, in italic)…”

“…One of the most fascinating organic molecules bearing nonclassical structure is [1.1.1]propellane A ( Figure 1). 2 This molecule has bridgehead carbon atoms with an umbrella-type geometry B 1,3 (shown in boldface) where all bonds point to a hemisphere, which has been often expressed as an inverted (tetrahedral) geometry. The bridgehead CC bond (inverted σ bond) in [1.1.1]propellanes shows considerably high reactivity with biradical (A¤) or ionic (A¤¤) characters compared with normal CC σ bond in normal tetrahedral geometry C because of the poor overlap between orbitals of the bridgehead carbon atoms in the inverted geometry.…”

Artificial tongues and leaves

“…To address this challenge, we often begin with lipid bilayer membranes or, more recently, conducting surfaces as platforms. To direct, control, and stabilize advanced functional architecture, rigid-rod molecules [3][4][5][6][7][8][9][10] have been introduced as shape-persistent scaffolds. Somehow the antithesis to foldamers [11,12], these simple sturdy rods are attractive scaffolds, bypassing all folding problems because they do not fold.…”

“…Somehow the antithesis to foldamers [11,12], these simple sturdy rods are attractive scaffolds, bypassing all folding problems because they do not fold. Unknown in biology, rigid-rod molecules are much appreciated in the materials sciences [3]. Prominent members of this family of oligomeric molecules include oligoacetylene 1, p-oligophenyls 2 [4,5] and their formal mixture, i.e., p-oligophenyleneethynylene (OPE) rods 3 [6,7] (Fig.…”

“…To address this challenge with synthetic pores, the creation of artificial tongues was an obvious choice because also on our own tongues, the sensation of taste is mediated by pores that respond to chemical stimulation [32]. 3 An artificial tongue to illustrate multicomponent sensing in complex matrices with synthetic pores and reactive amplifiers. The shown analyte concentrations are values measured in samples from the supermarket after signal generation with enzymes and cosubstrates (e.g., ATP), eventual signal amplification with CB or DAN hydrazides (Fig.…”