Sadao Arai

A new tripodal anion receptor with CH···X− hydrogen bonding

1,3,5-{Tris(3-n-butylimidazolio)methyl}-2,4,6-trimethybenzene 1, which has three imidazolium groups connected through a 1,3,5-trimethylbenzene spacer, has been synthesized as a novel receptor for halide anions. This tripodal receptor is shown to bind strongly Cl−, Br−, and I− anions in CD3CN through electrostatic interactions and CH···X− hydrogen bonds.

Polycyclic Aromatic Nitrogen Cations

Publisher Summary This chapter presents the synthesis of polycyclic aromatic nitrogen cations, as well as their chemical and physicochemical properties. The chemistry of bicyclic and tricyclic compounds is also discussed from a theoretical standpoint. The chapter discusses that there are two general types of polycyclic aromatic nitrogen cations: N-Alkyl quinolinium salts (Type A) and quinolizinium salts (Type B). Since the prefix azonia designates the cationic nitrogen, which is a part of cyclic structures, these two types of compounds are categorized as the azonia derivatives of polycyclic aromatic hydrocarbons. It reviews that the replacement of a bridgehead carbon of polycyclic aromatic hydrocarbons with nitrogen gives the azonia derivatives. Of the six possible tetracyclic benzenoid aromatic hydrocarbons, one can predict a total of 18 aromatic cations having bridgehead nitrogen. In case of compounds without symmetry, this happens because many isomeric compounds are possible due to the position of quaternary nitrogen.

Solvatochromism of stilbazolium merocyanine-type dyes containing a benzoquinolizinium ring

Abstract The UV/VIS spectra of a series of stilbazolium merocyanine-type dyes containing a benzoquinolizinium ring have been recorded in seven solvents. The dyes with a hydroxyl group showed hypsochromic shifts (less than 50 nm) on changing the solvent from 3-methylbutan-1-ol to water. On the other hand, the azonia betaine-type dyes formed by deprotonation of the hydroxy-substituted dyes exhibited a large hypsochromic shift (about 200 nm) as the solvent polarity increased. The transition energies (ET) of the dyes having a hydroxyl group did not correlate well with solvent polarity scales such as Brookers χR and χB, Kosowers Z, and Dimroth and Reichardts ET(30), while good correlations were observed between ET of the azonia betaine-type dyes and the scales χB, Z, and ET(30). The solvatochromism was analyzed by the linear solvation energy relationship with the multi-parameter proposed by the Kamlet, Abboud, and Taft group and showed excellent correlations for the azonia betaine-type dyes. The inherent wave-number (ν0) and the susceptibility of the absorption maximum (νmax) to solvent polarity-polarizability ( π ∗ ), to solvent hydrogen-bond donating acidity (α), and to solvent hydrogen-bond accepting basicity (β) are discussed.

Synthesis of 6-methylisoquinolino [7,8-a] quinolizinium salt : efficient synthesis of 2-(2-arylvinyl) quinolizinium salts by Knoevenagel condensation using acetonitrile as a solvent and the photocyclization

In the Knoevenagel condensation of 2,3-dimethylquinolizinium salt with a wide variety of aromatic aldehydes in the presence of piperidine, the use of acetonitrile as a solvent gave excellent yields (77-100 %) of 2-(2-arylvinyl)-quinolizinium salts. In the condensation using methanol the yields were low because active bis(1-piperidino)arylmethane derived from aldehyde and piperidine changed to inactive aryl(methoxy)-1-pipe- ridinomethane. The photocyclization of 2-[2-(4-pyridyl)vinyl]quinolizi- nium salt led to 6-methylisoquinolino[7,8-a]quinolizinium salt