resumo
Temperature-dependent 57Fe Mossbauer effect (ME) spectroscopic studies were carried out on ferrocene (Fc), 1,10-dimethylferrocene (1,10'(CH3)(2)Fc) and ferrocenium hexafluorophosphate (FcPF(6)) guest species in cucurbit[n] uril (n = 7, 8) inclusion complexes. The solid inclusion complexes were isolated by freeze-drying of dilute aqueous solutions and/or microwave-assisted precipitation from concentrated mixtures. The presence of genuine 1 : 1 (host : guest) inclusion complexes in the isolated solids was supported by liquid-state H-1 and solid-state C-13{H-1} MAS NMR, elemental and thermogravimetric analyses, powder X-ray diffraction, FTIR spectroscopy, and diffuse reflectance UV-Vis spectroscopy. The ME spectra of the complexes CB7.Fc and CB7.11'(CH3)(2)Fc consist of well-resolved doublets with hyperfine parameters (isomer shift and quadrupole splitting at 90 K) and temperature-dependent recoil-free fraction data that are very similar to those for the neat parent compounds, Fc and 1,10(CH3)(2)Fc, suggesting that the organometallic guest molecules do not interact significantly with the host environment over the experimental temperature range. The ME spectra for CB7.FcPF(6) and CB8.FcPF(6) consist of a major broad line resonance attributed to a paramagnetic FeIII site. From the temperature-dependence of the recoil-free fraction it is evident that the charged guest species in these systems interact with the host environment significantly more strongly than was observed in the case of the neutral guest species, Fc and 1,10(CH3)(2)Fc. Moreover, the ME data indicate that the vibrational amplitude of the ferrocenium guest molecule is significantly larger in the CB8 host molecule than in the CB7 homologue, as expected on the basis of the different cavity sizes.
palavras-chave
SOLID-STATE; MOLECULAR-REORIENTATION; COMPLEXES; HOST; ORGANOMETALLICS; MACROCYCLES; DERIVATIVES; TRANSITION; ADSORPTION; FRAMEWORKS
categoria
Chemistry; Physics
autores
Magalhaes, CIR; Gomes, AC; Lopes, AD; Goncalves, IS; Pillinger, M; Jin, E; Kim, I; Ko, YH; Kim, K; Nowik, I; Herber, RH
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Clara Isabel Ribeiro Magalhães
Bolseiro de investigação
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principalagradecimentos
This work was developed in the scope of the project CICECO - Aveiro Institute of Materials (POCI-01-0145-FEDER-007679) financed by national funds through the Fundacao para a Ciencia e a Tecnologia (FCT) (ref. UID/CTM/50011/2013) and Ministerio da Educacao e Ciencia (MEC) and when applicable, cofinanced by Fundo Europeu de Desenvolvimento Regional (FEDER) under the PT2020 Partnership Agreement. The FCT and the European Union are acknowledged for a post-doctoral grant to A. C. G. (SFRH/BPD/108541/2015), cofunded by Ministerio da Ciencia, Tecnologia e Ensino Superior (MCTES) and the European Social Fund through the program Programa Operacional Potencial Humano (POPH) of Quadro de Referencia Estrategica Nacional (QREN).