Synthesis, characterization and in situ monitoring of the mechanochemical reaction process of two manganese(II)-phosphonates with N-containing ligands

Abstract

Two divalent manganese aminophosphonates, manganese mono(nitrilotrimethylphosphonate) (MnNP3) and manganese bis(N-(carboxymethyl)iminodi(methylphoshonate)) (Mn(NP2AH)2), have been prepared by mechanochemical synthesis and characterized by powder X-ray diffraction (PXRD). The structure of the novel compound Mn(NP2AH)2 was determined from PXRD data. MnNP3 as well as Mn(NP2AH)2 exhibit a chain-like structure. In both cases, the manganese atom is coordinated by six oxygen atoms in a distorted octahedron. The local coordination around Mn was further characterized by Extended X-Ray Absorption Fine Structure (EXAFS). The synthesis process was followed in situ by synchrotron X-ray diffraction revealing a three-step reaction mechanism. The as-prepared manganese(II) phosphonates were calcined on air. All samples were successfully tested for their suitability as catalyst material in the oxygen evolution reaction (OER).

New Directions in Metal Phosphonate and Phosphinate Chemistry

“…Rietveld refinement proved that a pure compound is obtained. Further work on N-containing phosphonate ligands was carried out on manganese phosphonates [59] More recent additions to the body of work looked at exploiting MPs with N-containing ligands. In 2017, the compound zinc N-(phosphonomethyl)glycinate Zn(O 3 PCH 2 NH 2 CH 2 CO 2 )•H 2 O was reported, displaying a 3D pillared-layered structure (Figure 11a-c) [58].…”

“…Rietveld refinement proved that a pure compound is obtained. Further work on N-containing phosphonate ligands was carried out on manganese phosphonates [59], namely manganese mono(nitrilotrimethylphosphonate) ( Numerous efforts have also been made to combine mechanochemical synthesis and in situ characterisation methods, which are discussed more in detail in Section 3.5, herein.…”

“…These do not include any MPs, but the SynRAC could easily find employment for this class of materials as well. Section 3.2 has already suggested that in situ studies can be very informative for mechanochemical syntheses [56][57][58][59]97]. The two techniques used in each of the in situ studies reported so far were XRD and Raman spectroscopy, which allow the reaction to be monitored at both molecular and crystalline levels [97].…”

Mechanochemical Metathesis between AgNO3 and NaX (X = Cl, Br, I) and Ag2XNO3 Double-Salt Formation

“…It is therefore no surprise that the recent development of in situ techniques for uninterrupted reaction monitoring has been a breakthrough in the study and understanding of milling processes and dynamics . These methods, based on powder X-ray diffraction (PXRD), − Raman spectroscopy, − temperature , and pressure monitoring, − and their simultaneous application, ,− revealed complex milling reaction mechanisms, involving new polymorphic phases, , as well as multistep mechanisms − with crystalline and amorphous intermediates. ,, …”

Preface

“…The next two papers of this collection deal with such in situ studies. Thus, Michalchuk et al [5] examine the effect of different milling parameters in the mechanically induced polymorphic transformation of anhydrous caffeine, whereas Akhmetova et al use the same technique to monitor reaction pathways in the synthesis of two Mn(II) phosphonates, with different N-containing organic ligands [6]. As oxide particles are hard and brittle, mechanochemical reactions in oxide systems require longer milling times and more powerful milling devices making it very difficult to carry out real-time monitoring experiments.…”