Formation of a Eu(iii) borate solid species from a weak Eu(iii) borate complex in aqueous solution

Abstract

In the presence of polyborates (detected by (11)B-NMR) the formation of a weak Eu(III) borate complex (lg β11 ~ 2, estimated) was observed by time-resolved laser-induced fluorescence spectroscopy (TRLFS). This complex is a precursor for the formation of a solid Eu(III) borate species. The formation of this solid in solution was investigated by TRLFS as a function of the total boron concentration: the lower the total boron concentration, the slower is the solid formation. The solid Eu(III) borate was characterized by IR spectroscopy, powder XRD and solid-state TRLFS. The determination of the europium to boron ratio portends the existence of pentaborate units in the amorphous solid.

The interaction of Eu(iii) with organoborates – a further approach to understand the complexation in the An/Ln(iii)–borate system

“…The luminescence lifetime of the Eu-BLac is comparable to that of the Eu(III)-polyborate complex exhibiting a lifetime of ∼150 μs. 9 This is a first support of our hypothesis that borates with the general B(OR) 4 − unit show a comparable complexation behavior concerning trivalent lanthanides (and actinides). The luminescence lifetime of the Eu-BSal complex calculated with PARAFAC is strongly increased in comparison with the Eu-BLac and -polyborate complex.…”

“…It can be assigned to boric acid. 9,51 According to DFT calculations at the B3LYP level, the 11 B chemical shift of boric acid appears at 19.8 ppm (relative to BF 3 etherate), Table S2, † which is in agreement with the NMR experiments. Furthermore 11 B chemical shifts at 2.9, 6.3, and 1.1 ppm for the salicylate-boron, lactate-boron and 3-hydroxybutyrate-boron systems, respectively, were observed ( Fig.…”

“…Though differences in the 11 B NMR signals of both organoborate ligands indicate differences in the electronic structure of the boron atom, both the ring size of the organoborate and the electronic nature of the organic moieties bound to the B(OR) 4 − unit seems to have only a small influence on lg β Eu(BL) . Furthermore, the complexation constants of the Eu(III)organoborate complexes are well comparable to the complexation constant (lg β 0 11 = 2.66 ± 0.16) 9 of Eu(III)-polyborates (i.e., tri-and pentaborate) with one binding site. This is an important corroboration of the initial hypothesis that borates with the general structural unit B(OR) 4 −regardless if R is organic or inorganicshow a comparable complexation behavior concerning trivalent lanthanides (and actinides).…”

Poly(2‐hydroxyethyl methacrylate)/boric acid composite hydrogel as soft contact lens material: Thermal, optical, rheological, and enhanced antibacterial properties

“…The new peaks at 543 and 637 cm −1 are corroborated to characteristic stretching vibrations of OBO and BO 3 , respectively . The broad absorption band at 1444 cm −1 assigned to asymmetric stretching vibration of BO . The band which appears at 2259 cm −1 , corresponds to stretching vibration (OH and BO) and in‐plane bending (OH and BO) .…”

Borate‐Mediated Stereo‐ and Topo‐Selective Methylation of 1,4‐β‐Glucomannan

“…Making use of this phenomenon in chromatography or electrophoresis for the separation of polyhydroxy compounds including carbohydrates is well known . At pH ≥ 12, all boric acid is converted to borate and also polyborate ions should no longer occur . Higher stability of cis ‐ compared to trans ‐1,2‐diols is well known.…”