Molecular Design for Tailoring a Single-Source Precursor for Bismuth Ferrite

Abstract

Nearly phase-pure bismuth ferrite particles were formed by thermolysis of the single-source precursor [Cp(CO)2FeBi(OAc)2] (1) in octadecene at 245 °C, followed by subsequent calcination at 600 °C for 3 h. In contrast, the slightly modified compound [Cp(CO)2FeBi(O2C(t)Bu)2] (2) yielded only mixtures of different bismuth oxide phases, revealing the distinctive influence of molecular design in material synthesis. The chemical composition, morphology, and crystallinity of the resulting materials were investigated by X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. In addition, the optical properties were investigated by Fourier transform infrared and UV-vis spectroscopies, showing a strong band gap absorption in the visible range at 590 nm (2.2 eV). The magnetic behavior was probed by vibrating-sample and superconducting quantum interference device magnetometry, as well as (57)Fe Mössbauer spectroscopy.

Creating Iron– and Rhenium–Bismuth Bonds by Reactions with Organometallic Hydrides

“…Having finally fully understood the system [Cp 2 ReH] / [Bi(O t Bu) 3 ] it is clear, that the “hydride–alkoxide approach” can be utilized to create a large variety of organometallic compounds not only with Mo–Bi bonds but also such featuring Re–Bi bonds via reactions of rhenocene hydride with bismuth alkoxides . Bearing in mind the unique interplay between iron and bismuth in multiferroic bismuth ferrite (BiFeO 3 , BFO) an extension of this protocol also to the synthesis of complexes with Fe–Bi entities via reactions of bismuth alkoxides with iron hydrides was the obvious to test next, as potentially resulting molecular compounds may serve as single source precursors for BFO , . Compounds containing Fe–Bi bonds, have been accessed in the past by different routes, which are briefly exemplified here focussing on bismuthanes bearing a bismuth atom linked via a Fe–Bi bond to organoiron fragments, such as the well‐known η 5 ‐cyclopentadienyl dicarbonyl iron anion [Fp – = ( η 5 ‐C 5 H 5 )(CO) 2 Fe – ].…”

“…Two routes to compounds like [{( η 5 ‐C 5 H 4 R )(CO) 2 Fe}BiMe 2 ] ( R = H), [{( η 5 ‐C 5 H 4 R)(CO) 2 Fe} 2 Bi X ] ( R = H, X = Cl, Br; R = Me, X = Cl) and [{( η 5 ‐C 5 H 4 R )(CO) 2 Fe} 3 Bi] ( R = H, Me) have been established so far: (i) salt metathesis reactions treating bismuth halides with alkali metal salts of [Fp] – [27–30] or (ii) cleavage of the Fe–Fe bond in the [Fp 2 ] dimer in reactions with bismuth halides or bismuth dithiocarbamates as first reported by Cullen and co‐workers in 1971 for the synthesis of [FpBiCl 2 ] and later for the synthesis of [FpBi X 2 ] [ X = SC(S)NEt 2 , SC(S)OMe] by Wieber and co‐workers . The latter approach was recently successfully adapted by Mehring and co‐workers to access [Fp R BiBr 2 ] {Fp R = Fp; Fp t Bu [( η 5 ‐C 5 H 3 ‐1,3‐ t Bu 2 )(CO) 2 Fe]; Fp* [( η 5 ‐C 5 Me 5 )(CO) 2 Fe]} starting from [Fp R 2 ] and BiBr 3 (Scheme ) and also by us to synthesize the carboxylates [FpBi(O 2 C R ) 2 ] 2 via reaction of [Fp 2 ] with [Bi(O 2 CR) 3 ] [ R = H ( VII ), CH 3 ( VIII ), t Bu ( IX )] (Scheme ) . Treatment of VIII with [Cp 2 ReH] even allowed to construct a heterotrimetallic compound, which illustrates the value of the availability of a variety of tools to create M–M ′ bonds.…”

“…Synthesis of [Fp‐Bi(O 2 C R ) 2 ] (2 ··· n ) by reaction of [Fp 2 ] with [Bi(O 2 C R ) 3 ] [ R = H ( VII ), CH 3 ( VIII ), t Bu ( IX )] …”

“…Like the Fe‐Bi carboxylates [Fp‐Bi(O 2 C R ) 2 ] 2 [ R = CH 3 ( VIII ), t Bu ( IX )], the alkoxide 5 crystallizes as a dimer with a crystallographic inversion center. Two of the μ ‐OCH(CF 3 ) 2 alkoxide ligands act as bridging units constructing a [Bi–O7 ··· Bi′–O7′ ··· ] diamond motif.…”

“…So far Fe–Bi compounds were not synthesized via this “hydride‐alkoxide” route but recently we were able to show that [Fp‐Bi(O 2 CR) 2 ] 2 representatives can be generated via treatment of [Fp 2 ] [Fp = ( η 5 ‐C 5 H 5 )(CO) 2 Fe] with [Bi(O 2 C R ) 3 ] , . [Fp‐Bi(O 2 CCH 3 ) 2 ] 2 turned out to be a suitable single source precursor (SSP) to generate BFO . In order to enlarge the methodologic tool box to prepare such compounds we were interested in exploring the potential of [FpH] as a precursor compound, and we report the results herein.…”