Isolation of a Nitromethane Anion in the Calix-Shaped Inorganic Cage.

Yuji Kikukawa,Hiromasa Kitajima,Sho Kuwajima,Yoshihito Hayashi

doi:10.3390/molecules25235670

Yuji Kikukawa, Hiromasa Kitajima + Show 2 more

Open Access

https://doi.org/10.3390/molecules25235670

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Abstract

A calix-shaped polyoxometalate, [V12O32]4− (V12), stabilizes an anion moiety in its central cavity. This molecule-sized container has the potential to control the reactivity of an anion. The highly-reactive cyanate is smoothly trapped by V12 to form [V12O32(CN)]5−. In the CH3NO2 solution, cyanate abstracts protons from CH3NO2, and the resultant CH2NO2− is stabilized in V12 to form [V12O32(CH2NO2)]5− (V12(CH2NO2)). A crystallographic analysis revealed the double-bond characteristic short bond distance of 1.248 Å between the carbon and nitrogen atoms in the nitromethane anion in V12. 1H and 13C NMR studies showed that the nitromethane anion in V12 must not be exchanged with the nitromethane solvent. Thus, the V12 container restrains the reactivity of anionic species.

Highlights

Calixarene possesses a rigid conformation with a broader hydrophobic upper rim, a narrow hydrophilic lower rim, and a central annulus
The host property is finely tuned by the functional modification of the upper rim and/or the lower rim
Calixarene is utilized in various fields of science, such as catalysis, sensors, functional materials, analytical chemistry, electrochemistry, photochemistry, biochemistry, and pharmacy [6,7,8,9,10,11]

Summary

Introduction

Calixarene possesses a rigid conformation with a broader hydrophobic upper rim, a narrow hydrophilic lower rim, and a central annulus Due to this attractive architecture, the host–guest chemistry of calixarene has been developed [1,2,3,4]. Vanadium-based polyoxometalates formed by the condensation of VO5 square pyramids stabilize anionic moiety at the center of their clusters [16,17]. The broader upper rim consists of eight edge-shared VO5 pyramids, with a 4.4 Å cavity entrance and a narrow lower rim consisting of four vertex-shared VO5 pyramids (Figure 1) This attractive structure was first reported by Day et al in 1989 [19]. The crystal structure and 1 H and 13 C NMR spectra are discussed

Reactivity of Cyanide and the Effect of the Addition of V12

Crystal Strucuture and Charactorization

Materials and Methods

Conclusions