Structures of strontium diformate and strontium fumarate. A synchrotron powder diffraction study

Abstract

The crystal structures of strontium diformate in space groups P2(1)2(1)2(1) (alpha form, 295 K), P4(1)2(1)2 (beta form, 334 and 540 K) and I4(1)/amd (delta form, 605 K), and strontium fumarate in space groups Fddd (beta form, 105 K) and I4(1)/amd (alpha form, 293 K) have been determined from synchrotron X-ray powder diffraction data. Except for the alpha-strontium diformate, all the structures are based on a diamond-like Sr-ion arrangement, as in strontium acetylene dicarboxylate. The formate ions are disordered in the delta phase owing to steric hindrance. The fumarate ions are disordered over four (alpha) or two (beta) symmetry-equivalent orientations. alpha-Strontium fumarate crystallizes with a unique 90 degree carboxylate dihedral angle, and is stable up to 773 K.

Binding mechanism of strontium to biopolymer hydrogel composite materials

“…Sr-O distances are consistently 2.57 ± 0.01 Å for the HG, HG-A and OK-A samples. This is marginally shorter than most Sr-O distances reported, yet do fall within the reported range of 2.55-2.64 Å [5,7,22,24]. Sr-C distances reported in this study are intermediate within the range of organic Sr-C distances (3.05-3.8 Å) reported in crystallographic diffraction studies [24][25][26][27].…”

“…This is marginally shorter than most Sr-O distances reported, yet do fall within the reported range of 2.55-2.64 Å [5,7,22,24]. Sr-C distances reported in this study are intermediate within the range of organic Sr-C distances (3.05-3.8 Å) reported in crystallographic diffraction studies [24][25][26][27]. Sr-C distance in a carboxylate bidentate binding can be as short as 3.05 Å [24], while an oxalate bidentate binding mode yields Sr-C distance of around 3.3-3.45 Å [30] and monodentate binding typically yields Sr-C distance above 3.4 Å [24,25,27].…”

“…Well resolved two peaks in the magnitude of Fourier Transformed EXAFS signal could suggest that strontium forms direct bonds with activated oak wood biochar via oxygen and carbon atoms, essentially confirming presence of an inner sphere complexation at pH 7. The system was buffered during uptake since the pHdependent nature of strontium binding is well known [6,7,24]. Oftentimes other strontium adsorbents exhibit little or no second shell signal at circumneutral pH indicating outer sphere complexation [24][25][26] in contrast to the adsorbents in this study.…”

“…The system was buffered during uptake since the pHdependent nature of strontium binding is well known [6,7,24]. Oftentimes other strontium adsorbents exhibit little or no second shell signal at circumneutral pH indicating outer sphere complexation [24][25][26] in contrast to the adsorbents in this study. Derived coordination numbers and atomic distances are displayed in Table 3.…”

Tuning Mixed‐Valent Eu2+/Eu3+ in Strontium Formate Frameworks for Multichannel Photoluminescence

“…The crystal structure of the host lattice Sr(HCOO) 2 was elucidated using single‐crystal X‐ray diffraction, and it is best described as a dense 3D framework crystallizing in a chiral tetragonal space group P 4 1 2 1 2 as shown in Figure . The asymmetric unit contains one six‐coordinated Sr 2+ site and one η 3 ‐formate group.…”