Alkaline Earth Metal Organotriphosphonates:  Inorganic−Organic Polymeric Hybrids from Dication−Dianion Association

Abstract

Mg2+ (1), Ca2+ (2), Sr2+ (3), or Ba2+ (4) salts react with amino-tris(methylenephosphonic acid) (H6AMP) in a 1:1 ratio at low pH by replacing two of the six phosphonic acid protons, while the amino N maintains its proton, thus forming a zwitterion (H4AMP2-). All four structures are polymeric and substantially different from one another. In all structures, each phosphonate group is singly deprotonated, whereas the N atom is protonated. 1 consists of {Mg[HN(CH2PO3H)3(H2O)3]} n units. Mg2+ ions form zigzag chains bridged by two of the three phosphonate groups. The third phosphonate group is noncoordinated and involved in hydrogen bonding. 3 is a three-dimensional (3D) polymer with the composition [Sr(H4AMP)] n . The Sr-atoms are seven-coordinate, with five monohapto and one chelating AMP ligands. In the 3D polymer 4, {Ba(H4AMP)(H2O)} n , the two crystallographically independent Ba2+ centers are 9- and 10-coordinated by phosphonate and H2O oxygen atoms. All bridging oxygen atoms belong to phosphonate moieties that act as chelates for one Ba2+ and form 4-membered rings. The crystal structure of {Ba(H4AMP)(H2O)} n is characterized by the complete absence of hydrogen bonds.

Syntheses, structures, thermal stabilities and luminescence of two new 3D zinc phosphonates

“…It is worth to mention that the nitrogen atom is not protonated and takes part in coordination. This is different from those in the reported compounds [40][41][42][43][44][45][46][47]. In addition, there are four hydrogen bondings in this structure: (1) the protonated 1,4-butanediamine provides three hydrogen atoms to form hydrogen bondings with adjacent phosphonate groups (N2 Á Á Á O5, 2.816(6)Å; N3 Á Á Á O3, 2.816(6)Å; N3 Á Á Á O8d, 2.892(7)Å); (2) the protonated phosphonate oxygen atom (O7) interacts with the neighboring phosphonate oxygen atom (O2e) through a strong hydrogen bonding (O7 Á Á Á O2e, 2.460(6)Å).…”

Coordination polymer networks with s-block metal ions

“…Also, polyphosphonic acids have attracted significant attention in recent years due to their utility in supramolecular chemistry and crystal engineering [77]. Polyphosphonates are also used extensively in an array of industrial applications such as chemical water treatment, oilfield drilling, minerals processing, corrosion control, and metal complexation and sequestration.…”

Synthesis and structural investigation of two metal-organic frameworks constructed from alkaline earth metal cations and organic ligand 5-nitroisophthalic acid (5-NO2-H2BDC)

“…In fact, alkaline earth metal ions with high co-ordination numbers [2] are favored to the reaction of hard base which has stronger ability to present electrons like oxygen of carboxylate group based on the soft and hard acid and base theory. So many works about alkaline earth complexes and patents on the use of these complexes have been studied during the last decade [3][4][5][6][7][8][9][10][11][12][13]. We select one of symmetric 5-substituted forms of benzenedicarboxylic acid organic ligand 5-NO 2 -H 2 BDC in which the carboxylate groups has flexible co-ordination modes [14][15][16][17][18][19] and sensitivity to pH values resulting in the variety of the structure while the nitro-group can act as a hydrogen bond acceptor and take on some spatial effects in the formation of polymeric networks.…”