Correlation between the MOH2 Bond Force Constants, Energies, and Lengths and Magnetic Moments of the Metal Atoms in Isostructural Nitrilotris(methylenephosphonic) Complexes [MII(H2O)3-NH(CH2PO3H)3] (MII = Cr-Zn)

The isostructural 3d transition metal complexes [M-II(H2O)(3)-NH(CH2PO3H)(3)] (M-II = Cr-Zn) were studied by X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. In order to gain more in-depth knowledge about the chemical bonds in coordination compounds, correlation analysis was carried out between the force constants and energies of the MOH2 coordination bonds and the magnetic moments of transition metal atoms. The correlation of the force constants of the MOH2 bonds with the M-O(w) interatomic distances was in line with the known empirical Badger's rule. The double linear regression between the bond energy and reciprocal of M-O(w) interatomic distances and atomic magnetic moments shows a close relationship between the MOH2 bond energy and the spin magnetic moment of 3d-metal atoms. The results account for the stability of Fe-containing heterometallic polymeric NTP complexes and high efficiency of NTP complexes as corrosion inhibitors for iron alloys in aqueous media.