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1,4-Phenylenebis(methylidyne)tetrakis(phosphonic acid): A New Building Block in Metal Organic Framework Synthesis

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posted on 18.05.2009, 00:00 by Monika Plabst, Thomas Bein
Through the use of a synthetic high-throughput approach, 1,4-phenylenebis(methylidyne)-tetrakis(phosphonic acid), H8L, was investigated as a molecular building block for the formation of coordination frameworks with lanthanides (Ln = La, Nd, Gd, Dy) under hydrothermal conditions. Thereby, 14 new lanthanide phosphonates were discovered, categorized into three structure types, and their crystallization fields described. Structure type I comprises six compounds with the general formula Ln(H5L). The examples of Ln[(PO3H)2CH−C6H4−CH(PO3H)(PO3H2)]·4H2O, where Ln = La, and Nd, reveal two-dimensional coordination networks having a layered structure but differ in the layer stacking. Structure type II comprises four compounds of the general formula Ln2(H2L) and is represented by La2[(HO3P)(O3P)CH−C6H4−CH(PO3)(PO3H)]·8H2O, a layered structure with dimeric lanthanum coordination polyhedra. Four compounds of the type NaLn(H4L) are in stucture type III, which was solved from LaNa[(PO3H)2CH−C6H4−CH(PO3H)2]·4H2O. This structure consists of a three-dimensional open framework with La3+ coordinated by bisphosphonate units in an exclusively bidentate fashion. It has a one-dimensional rhombic channel system that is occupied by sodium ions and water molecules acting as guests.