Tuning the organization of the interlayer organic moiety in a hybrid layered perovskite

The insertion of phenylbutylamine into a layered perovskite of formula H₂Bi_0.1Sr_0.85Ta₂O₇ (HST) has been investigated as a function of the synthesis conditions. For short reactions times (1.5 h), achieved using microwave assisted reactions, a short interlayer distance (2.2 nm) is obtained (PBA1-HST) whereas for long reaction times (18 h) achieved using classical solvothermal reaction, a much larger interlayer distance is obtained (3.0 nm) (PBA3-HST). The compounds are well crystallized despite a more pronounced disorder of the organic moiety for PBA1-HST, evidenced by IR spectroscopy. The organic loading is very similar for both phases, and no difference in the ¹³C CP/MAS solid state NMR spectra could be evidenced. 1D electron density profiles established from XRD patterns allow to precise the organization of the molecules within the interlayer space. More subtle variations of the reaction parameters tend to show that there is a gradual evolution from the kinetic product, PBA1-HST, to the thermodynamic one, PBA3-HST, but it has not been possible to isolate a monophasic intermediate phase. Yet a compound with an intermediate interlayer distance could be isolated as a pure phase, using a prefunctionalized precursor as starting material (PBA2-HST, 2.7 nm). It was finally shown that it is possible to realize a mutual conversion of PBA2-HST and PBA3-HST by post-synthesis solvent treatment. This work completes the emerging studies on microwave-assisted functionalization of layered oxides and paves the way to a fine tailoring of hybrid materials with specific structures and properties.