Duplexiphane: A Polyaromatic Receptor Containing Two Adjoined Δ-Shaped Cavities for an Efficient Hopping of a Single Silver Cation

Structure-Activity Relationships for a Recently Controlled Synthetic Cathinone Dopamine Transporter Reuptake Inhibitor: α-Pyrrolidinohexiophenone (α-PHP)

α-Pyrrolidinohexiophenone (α-PHP) is the one-carbon unit α-extended homolog of the better-known and widely abused synthetic cathinone central stimulant α-PVP ("flakka"); both are now U.S. Schedule I controlled substances. Structurally, α-PVP and α-PHP possess a common terminal N-pyrrolidine moiety and differ only with respect to the length of their α-alkyl chain. Using a synaptosomal assay, we previously reported that α-PHP is at least as potent as α-PVP as a dopamine transporter (DAT) reuptake inhibitor. A systematic structure-activity study of synthetic cathinones (e.g., α-PHP) as DAT reuptake inhibitors (i.e., transport blockers), a mechanism thought responsible for their abuse liability, has yet to be conducted. Here, we examined a series of 4-substituted α-PHP analogues and found that, with one exception, all behaved as relatively (28- to >300-fold) selective DAT versus serotonin transporter (SERT) reuptake inhibitors with DAT inhibition potencies of most falling within a very narrow (i.e., <3-fold) range. The 4-CF3 analogue of α-PHP was a confirmed "outlier" in that it was at least 80-fold less potent than the other analogues and displayed reduced (i.e., no) DAT vs SERT selectivity. Consideration of various physicochemical properties of the CF3 group, relative to that of the other substituents involved here, provided relatively little insight. Unlike with DAT-releasing agents, as previously reported by us, a QSAR study was precluded because of the limited range of empirical results (with the exception of the 4-CF3 analogue) for DAT reuptake inhibition.

P2O5-Promoted Cyclization of Di[aryl(hetaryl)methyl] Malonic Acids as a Pathway to Fused Spiro[4.4]nonane-1,6-Diones

Conventional spiro-linked conjugated materials are attractive for organic optoelectronic applications due to the unique combination of their optical and electronic properties. However, spiro-linked conjugated materials with conjugation extension directed along the main axis of the molecule are still only rare examples among the vast number of spiro-linked conjugated materials. Herein, the synthesis, leading to π-extended spiro-linked conjugated materials─spiro[4.4]nonane-1,6-diones and spiro[5.5]undecane-1,7-diones─has been developed and optimized. The proposed design concept starts from readily available malonic esters and contains several steps: double alkylation of malonic ester with bromomethylaryl(hetaryl)s; conversion of a malonic ester into the corresponding malonic acid; electrophilic spirocyclization of the latter into the annulated spiro[4.4]nonane-1,6-dione or spiro[5.5]undecane-1,7-dione in the presence of phosphorus pentoxide. On the basis of these insights, the developed method yielded spiro-linked conjugated cores fused with benzene, thiophene, and naphthalene, decorated with active halogen atoms. The structures of the synthesized spirocycles were determined by single-crystal X-ray diffraction analysis. Benzene fused spiro[4.4]nonane-1,6-dione decorated with bromine atoms was transformed into V-shape phenylene-thiophene co-oligomer type spirodimers via Stille coupling. The spiro-bis(4-n-dodecylphenyl)-2,2'-bithiophene derivative possessed high photoluminescence properties in both solution and solid state with a photoluminescence quantum yield (PL QY) of 38%.

Synthesis and structural characterisation of bulky heptaaromatic (hetero)aryl o-substituted s-aryltetrazines

Hexaphenylbenzene analogs with an electron-poor tetrazine core are synthesized in two high-yield steps from diphenyl-s-tetrazine. Crystal packing of these unique non-planar heptaaromatics is analyzed in details.

Helicenes as Molecular Tweezers in the Formation of Cation-π Complexes. Bonding and Circular Dichroism Properties from Relativistic DFT Calculations

Helicene ligands possess a unique helicoidal π-conjugated framework providing high optical rotation values. This has stimulated a growing interest in helicene derivatives as building blocks, which has triggered the development of simple strategies to tune their properties. In this context, we evaluated the formation of cation-π complexes derived from [6]- and [7]helicene, involving Sn²⁺ , Cd²⁺ , and In⁺ in addition of Ag⁺ , which appears as a plausible modification of such helicoidal structure. The nature of the cation-π interaction in the studied helicene complexes exhibits a covalent character, accounting for ligand π-donation to 5 s and 5p empty orbitals of the involved cations. Furthermore, the evaluation of their optical activity exhibits notorious modification patterns in the circular dichroism spectrum, suggesting that the modifications of the optical activity are dependent on the nature of the cation and its related charge state. Thus, the plausible formation of new cation-π complexes derived from helicene ligands, as discussed here, may lead to the characterization of novel species expanding the chemistry of helicene metal complexes to even to larger helicene units. We believe that the present study may open new avenues in the formation of cation-π helicene complexes.

Endo or Exo? Structures of Gas-Phase Alkali Metal Cation/Aromatic Half-Belt Complexes

1,1,9,9-Tetramethyl[9](2,11)teropyrenophane (TM9TP), a belt-shaped molecule, has a sizable cavity that molecules or ions could occupy. In this study, the question of whether TM9TP forms gas-phase ion-molecule complexes with metal cations (K⁺ , Rb⁺ , Cs⁺ ) situated inside or outside the TM9TP cavity was addressed using both experimental and computational methods. Complexes were trapped in a Fourier transform ion cyclotron resonance mass spectrometer and their structures were explored by some novel physical chemistry/mass spectrometry methods. Blackbody infrared radiative dissociation kinetics reveal two populations of ions, a fast dissociating fraction and a persistent fraction. Infrared multiphoton dissociation spectra (vibrational spectra) provide very strong evidence that the most abundant population is a complex where the metal cation is inside the TM9TP cavity, endo-TM9TP. Red-shifted C-H stretching bands present in the gas-phase vibrational spectra of these ionic complexes show that there is an interaction between the metal cation and bridge C-H bonds due to the cation sitting inside the cavity of TM9TP. B3LYP/6-31+G(d,p) calculations showed the endo complexes to be the lowest in energy; about 60 kJ mol^-1 more thermodynamically stable and more than 120 kJ mol^-1 kinetically more stable than the exo complex.

Synthesis of biaryls using aryne intermediates

The synthesis of biaryls from benzyne intermediates offers an alternative strategy to conventional metal-catalyzed cross-coupling approaches.