Synthesis and characterization of four new metal 5-phosphonoisophthalates discovered by high-throughput experimentation

A new ligand, 5-diethylphosphonoisophthalic acid ((HOOC)(2)C6H3-PO3(C2H5)(2), H2Et2L), for the hydrothermal synthesis of inorganic-organic hybrid compounds was prepared and characterized by NMR-spectroscopy. Its in situ hydrolysis leads to the corresponding 5-phosphonoisophthalic acid ((HOOC)(2)C6H3-PO3H2, H4L). Applying high-throughput methods, different di- and trivalent metal salts for the synthesis of crystalline metal phosphonates based on H2Et2L have been screened. From the resulting discovery library, single-crystals of four new compounds, [Sm-2(H2O)(4)(H(OOC)(2)C6H3-PO3)(2)] center dot 2H(2)O (1), [Cu-3(H2O)(H(OOC)(2)C6H3-PO3)(2)] center dot 2H(2)O (2), Ca-2(H2O)[H(OOC) 2C(6)H(3)-PO3H](2) (3), and Ba-2(H2O)(3)(OOC)(2)C6H3-PO3 (4), have been isolated. The single-crystal structure determination of the title compounds shows H4L to be a versatile ligand, exhibiting different types of coordination modes between the functional groups and the metal ions. A comparison of the structural features of the title compounds shows a varying degree of M-O-M connectivities. Thus, isolated metal-oxygen clusters (compounds 1 and 2), infinite M-O-M chains (compound 3), and infinite M-O-M layers (compound 4) are observed. The title compounds 1, 2, and 3 were further characterized by IR-spectroscopy, TG-, EDX-, and elemental chemical analysis. (C) 2007 Elsevier Inc. All rights reserved.