Complexes Formed between Nitrilotris(methylenephosphonic acid) and M²⁺ Transition Metals:  Isostructural Organic−Inorganic Hybrids

Abstract

Nitrilotris(methylenephosphonic acid) (NTP, [N(CH(2)PO(3)H(2))(3)]) recently has been found to form three-dimensional porous structures with encapsulation of templates as well as layered and linear structures with template intercalation. It was, therefore, of interest to examine the type of organic-inorganic hybrids that would form with metal cations. Mn(II) was found to replace two of the six acid protons, while a third proton bonds to the nitrilo nitrogen, forming a zwitter ion. Two types of compounds were obtained. When the ratio of acid to Mn(II) was less than 10, a trihydrate, Mn[HN(CH(2)PO(3)H)(3)(H(2)O)(3)] (2) formed. Compound 2 is monoclinic P2(1)/c, with a = 9.283(2) A, b = 16.027(3) A, c = 9.7742(2) A, beta = 115.209(3) degrees, V = 1315.0(5) A(3), and Z = 4. The Mn atoms form zigzag chains bridged by two of the three phosphonate groups. The third phosphonate group is only involved in hydrogen bonding. The metal atoms are octahedrally coordinated with three of the sites occupied by water molecules. Adjacent chains are hydrogen-bonded to each other through POH and HN donors, and the additional participation of all the water hydrogens in H-bonding results in a corrugated sheet-like structure. Use of excess NTP at a ratio to metal of 10 to 1 yields an anhydrous compound Mn[HN(CH(2)PO(3)H)(3)] (1), P2(1)/n, a = 9.129(1) A, b = 8.408(1) A, c = 13.453(1) A, beta = 97.830(2) degrees, V = 1023.0(2) A(3), and Z = 4. Manganese is five coordinate forming a distorted square pyramid with oxygens from five different phosphonate groups. The sixth oxygen is 2.85 A from an adjacent Mn, preventing octahedral coordination. All the protonated atoms, three phosphonate oxygens and N, form moderately strong hydrogen bonds in a compact three-dimensional structure. The open-structured trihydrate forms a series of isostructural compounds with other divalent transition metal ions as well as with mixed-metal compositions. This is indicative that the hydrogen bonding controls the type of structure formed irrespective of the cation.

Synthesis, crystal structures and supramolecular architectures of square pyramidal Cu(II) complexes containing aromatic chelating N,N’-donor ligands

“…The distance between two copper metal centers in the dimer is 5.100Å. The assignment of P = O, P − O − , and P − OH bonds are consistent with the literature [54]. The largest angle around the Cu(II) center (β) is considerably different from the second largest one(α).…”

Crystal growth and characterization of zinc–(amino-tris-(methylenephosphonate)) organic–inorganic hybrid networks and their inhibiting effect on metallic corrosion

“…Structurally characterized metal-AMP materials reported in the literature include Mn-AMP (that is isostructural to Zn-AMP reported herein) [15,16], Ca-AMP, [4a,17], Pb-AMP [18], Na-AMP [19], and Al-AMP [20].…”

Nanomaterials for Environmental Remediation

“…Some of these supramolecular structures (e.g., that formed between NTP and 1,7-phenanthroline) have unique chromophoric properties, forming charge-transfer complexes when protonated, suggesting that perhaps these materials might be useful in sensing/detection applications. Metal complexes of NTP have also been prepared [54]. Once again, open, highly hydrogen-bound structures were obtained.…”