Small‐Molecule Anion Recognition by a Shape‐Responsive Bowl‐Type Dodecavanadate

Abstract

A dodecavanadate, [V O ] , is an inorganic bowl-type host with a cavity entrance with a diameter of 4.4 Å in the optimized structure. Linear, bent, and trigonal planar anions are tested as guest anions and the formation of host-guest complexes, [V O (X)] (X=CN , OCN , NO , NO , HCO , and CH CO ), were confirmed by X-ray crystallographic analyses and a V NMR spectroscopy study. The degree of distortion of the bowl from a regular to an oval shape depends on the type of guest anion. In V NMR spectroscopy, all chemical shifts of the host-guest complexes are clearly shifted after guest incorporation. The incorporation reaction rates for OCN , NO , HCO , and CH CO are much larger than those of NO and halides. The incorporated nonspherical molecular anions in the dodecavanadate host are easily dissociated or exchanged for other anions, whereas spherical halides in the host are preserved without dissociation, even in the presence of the tested anions.

Synthesis and structural characterization of tube-type tetradecavanadates

“…All reagents and solvents were purchased from commercial sources and were used without further purification unless otherwise noted. The bowl-type dodecavanadates were prepared according to reported procedures (Kuwajima et al, 2017b). IR spectra were measured as KBr pellets on a JASCO FT/IR-4200 spectrometer.…”

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

“…The distance between the central anion and its nearest neighbor vanadium is far from bonding distances, showing that the central anion is floating in the container. Among polyoxometalates composed of VO 5 square pyramids, a 'calix'-shaped dodecavanadate [V 12 O 32 ] 4− (V12) is known [19][20][21][22][23][24][25][26][27][28][29][30]. The broader upper rim consists of eight edge-shared VO 5 pyramids, with a 4.4 Å cavity entrance and a narrow lower rim consisting of four vertex-shared VO 5 pyramids ( Figure 1).…”

“…In the initial stage of the V12 chemistry, the utility is limited to the guest exchange among nitriles because of the strong affinity between the nitrile group and the V12 container [20][21][22]. Recently, we have developed the host-guest chemistry of V12 [23][24][25][26][27][28][29]. By avoiding the usage of the nitrile group in the synthetic procedure by controlling the oxidation state of the vanadium sources, V12 with guest-exchangeability to various electron-rich groups can be prepared [25].…”

“…In the case of Br 2 , Br 2 inserted into V12 is polarized due to the unique charge distribution of the inside of V12, and the peak of the Br−Br vibration is detected in IR at 185 cm −1 [29]. Furthermore, the stabilization of several kinds of anions in V12 has been reported [25][26][27]. The most interesting example is NO − -including V12 [30].…”

Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity

“…[22] The interior of the guest-occupied V12 is relatively cationic owing to high-valent and coordinatively unsaturated vanadium atoms to stabilize an electron-rich group or anion, while the cavity entrance is relatively anionic owing to the eight oxygen atoms. [23][24][25][26] Among the halogen atoms, bromine fits the V12 cavity the best. [26] This specific feature of V12 inspired the idea of preparing an polarized Br 2 by inserting Br 2 into the V12 bowl and using this polarized Br 2 as the electrophilic reagent for alkane bromination.…”