Design and synthesis of the first triply twisted Möbius annulene

Non-planar oligoarylene macrocycles from biphenyl

Saddle- and propeller-shaped, partially condensed conjugated macrocycles are synthesized by fourfold Perkin condensation plus fourfold photocyclizations. Their macrocyclic loops are pronouncedly non-planar.

Duality of Orbital-Symmetry-Allowed Transition States for Thermal Sigmatropic Hydrogen Shifts in Transition Metal Compounds

Herein, the Zimmerman Möbius/Hückel concept is extended to pericyclic reactions involving transition metals. While sigmatropic hydrogen shifts in parent hydrocarbons are either uniquely antarafacial or suprafacial, we have shown by theoretical orbital topology considerations and quantum chemical computations at DFT level that both modes of stereoselectivity must become allowed in the same system as a consequence of Craig-Möbius-type orbital arrays, in which a transition metal d orbital induces a phase dislocation in metallacycles. This may have fundamental implications for the understanding of reactivity and bonding in organometallic chemistry.

CCCCC pentadentate chelates with planar Möbius aromaticity and unique properties

The coordinating atoms in polydentate chelates are primarily heteroatoms. We present the first examples of pentadentate chelates with all binding atoms of the chelating agent being carbon atoms, denoted as CCCCC chelates. Having up to five metal-carbon bonds in the equatorial plane has not been previously observed in transition metal chemistry. Density functional theory calculations showed that the planar metallacycle has extended Craig-Möbius aromaticity arising from 12-center-12-electron dπ-pπ π-conjugation. These planar chelates have broad absorption in the ultraviolet-visible-near-infrared region and, thus, notable photothermal performance upon irradiation by an 808-nm laser, indicating that these chelates have potential applications in photothermal therapy. The combination of facile synthesis, high stability, and broad absorption of these complexes could make the polydentate carbon chain a novel building block in coordination chemistry.

Influence of material stretchability on the equilibrium shape of a Möbius band

We use a two-dimensional discrete, lattice-based model to show that Möbius bands made with stretchable materials are less likely to crease or tear. This stems from a delocalization of twisting strain that occurs if stretching is allowed. The associated low-energy configurations provide strategic target shapes for the guided assembly of nanometer and micron scale Möbius bands. To predict macroscopic band shapes for a given material, we establish a connection between stretchability and relevant continuum moduli, leading to insight regarding the practical feasibility of synthesizing Möbius bands from materials with continuum parameters that can be measured experimentally or estimated by upscale averaging.

Understanding the molecular switching properties of octaphyrins

Triggering Hückel–Möbius topological and aromaticity switches in octaphyrins by protonation and redox reactions.

Five-membered cyclic metal carbyne: synthesis of osmapentalynes by the reactions of osmapentalene with allene, alkyne, and alkene

The synthesis of small cyclic metal carbynes is challenging due to the large angle strain associated with the highly distorted nonlinear triple bonds. Herein, we report a general route for the synthesis of five-membered cyclic metal carbyne complexes, osmapentalynes, by the reactions of an osmapentalene derivative with allene, alkyne, and alkene. Experimental observations and theoretical calculations document the aromaticity in the fused five-membered rings of osmapentalynes. The realization of transforming osmapentalene to osmapentalyne through this general route would not only allow further exploration of metallapentalyne chemistry but also show promising applications of this novel aromatic system with broad absorption band and high molar absorption coefficient.

Triply twisted Möbius annulene: a new class of two-photon active material – a computational study

The present study clearly reveals that the triply twisted Möbius annulene molecules decorated with suitable donor–acceptor groups can be used as a potential two-photon active material.