Interactions of Cationic and Neutral Molybdenum Complexes with β-Cyclodextrin Host Molecules

Abstract

The inclusion compounds formed between -cyclodextrin ( -CD) and the tetrafluoroborate salts [Cp′Mo(η 4 -C 6 H 8 )(CO) 2 ][BF 4 ] and the neutral derivatives Cp′Mo(η 3 -C 6 H 7 )(CO) 2 [Cp′ ) Cp (η 5 -C 5 H 5 ), Ind (η 5 -C 9 H 7 )] were studied by means of elemental analysis, FTIR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and magic-angle spinning (MAS) NMR ( 13 C, 11 B). Additional information concerning the possible structure of the inclusion compounds was obtained from ab initio calculations using a two-layer approximation. The cationic and neutral η 5 -cyclopentadienyl analogues form stable two-to-one (hostto-guest) channel-type inclusion compounds in a crystalline state. By contrast, the η 5 -indenyl analogues form only weak complexes with -CD and it is evident that the organometallic guests are easily liberated from the host cavities. The ab initio calculations revealed that the steric hindrance arising from the presence of the indenyl ligand is a possible explanation for the experimentally observed lower stability of these compounds.

FeBr3–cyclodextrin complexes as efficient and chemoselective catalysts for sulfoxidation reactions

“…These studies show that the thermal stability of cyclodextrins is less in the presence of the guest. Similar results were obtained for the complex of ␤-CD with FeBr 3 [47] and other metal cyclodextrin complexes [49][50][51][52][53][54]. The data are summarized in Table 1 and are shown in Figs.…”

Review: Cyclodextrin Inclusion Complexes Probed by NMR Techniques

“…The appearance of multiple resonances for atoms C2, C3, C5, C4, and C6 of the glucopyranose units indicates the coexistence of different structural arrangements (Lima, 2001). Usually, the multiple resonances of the carbons of the glucose monomers tends to converge to a single peak in the inclusion compound, suggesting that the glucose units adopt a more symmetrical conformation in the complex (Lai et al, 2003).…”

13C‐CPMAS and 1H‐NMR Study of the Inclusion Complexes of β‐Cyclodextrin with Carvacrol, Thymol, and Eugenol Prepared in Supercritical Carbon Dioxide

“…As can be observed in the spectra of b-CDÀ1 and b-CDÀ3, the signals of the guest molecules were not detected probably because of their molecular mobility inside the b-CD cavity. The b-CD resonances were assigned according to a previous NMR investigation [27], while the resonances of 2 were attributed from the analysis of the coupled and decoupled 13 C-NMR-spectra in CDCl 3 (see Table 3). …”

“…It is worth noting that the spectrum of the free b-CD is relatively poorly resolved due to the presence of multiple resonances for the C-atoms of the glucose units (C(2), C(3), C(4), C(5), and C(6)), which can be ascribed to the co-existence of different structural arrangements [27] induced by partial hydration of the sample [28]. Such a set of arrangements are also observed in the inclusion complexes, clearly suggesting that only weak interactions are established between the b-CD and the guest molecules.…”