Glyphosate complexation to aluminium(III). An equilibrium and structural study in solution using potentiometry, multinuclear NMR, ATR-FTIR, ESI-MS and DFT calculations.
The stoichiometries and stability constants of a series of Al(3+)-N-phosponomethyl glycine (PMG/H(3)L) complexes have been determined in acidic aqueous solution using a combination of precise potentiometric titration data, quantitative (27)Al and (31)P NMR spectra, ATR-FTIR spectrum and ESI-MS measurements (0.6M NaCl, 25 degrees C). Besides the mononuclear AlH(2)L(2+), Al(H(2)L)(HL), Al(HL)(2)(-) and Al(HL)L(2-), dimeric Al(2)(HL)L(+) and trinuclear Al(3)H(5)L(4)(2+) complexes have been postulated. (1)H and (31)P NMR data show that different isomers co-exist in solution and the isomerization reactions are slow on the (31)P NMR time scale. The geometries of monomeric and dimeric complexes likely double hydroxo bridged and double phosphonate bridged isomers have been optimized using DFT ab initio calculations starting from rational structural proposals. Energy calculations using the PCM solvation method also support the co-existence of isomers in solutions.
Purgel
Mihály
M
Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
Takács
Zoltán
Z
Jonsson
Caroline M
CM
Nagy
Lajos
L
Andersson
Ingegärd
I
Bányai
István
I
Pápai
Imre
I
Persson
Per
P
Sjöberg
Staffan
S
Tóth
Imre
I
D000535:Aluminum / Q000737:chemistry*; D017607:Aluminum Compounds / Q000737:chemistry*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011199:Potentiometry; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D000097797:Glyphosate
D000535:Aluminum; D017607:Aluminum Compounds; D005998:Glycine; D000097797:Glyphosate