1,4-Phenylenebis(methylidyne)tetrakis(phosphonic acid): a new building block in metal organic framework synthesis

Abstract

Through the use of a synthetic high-throughput approach, 1,4-phenylenebis(methylidyne)-tetrakis(phosphonic acid), H(8)L, 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(H(5)L). The examples of Ln[(PO(3)H)(2)CH-C(6)H(4)-CH(PO(3)H)(PO(3)H(2))].4H(2)O, 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 Ln(2)(H(2)L) and is represented by La(2)[(HO(3)P)(O(3)P)CH-C(6)H(4)-CH(PO(3))(PO(3)H)].8H(2)O, a layered structure with dimeric lanthanum coordination polyhedra. Four compounds of the type NaLn(H(4)L) are in stucture type III, which was solved from LaNa[(PO(3)H)(2)CH-C(6)H(4)-CH(PO(3)H)(2)].4H(2)O. This structure consists of a three-dimensional open framework with La(3+) 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.