Synthesis, Spectroscopic Characterisation, and Structural Elucidation of Ni(II) and Cu(II) Complexes of a Novel N,N’-Diaminophthalamidoxime Ligand
- 1Department of Chemistry, Faculty of Science
- 2University of Ibadan
Abstract
A new N,N’-diaminophthalamidoxime (NAD) ligand was synthesised by reacting hydrazine hydrate with diethyl phthalate to give phthalic dihydrazide, which was subsequently reacted with hydroxylamine to yield the target ligand. The ligand was reacted with Ni(II) and Cu(II) salts to give [Ni(NAD)2]Cl2 and [Cu(NAD)2(OAc)2], respectively. The ligand and its complexes were characterised by solubility studies, melting point determination, complexometric metal analysis, room-temperature magnetic susceptibility, and infrared and UV–Visible spectroscopy. The free ligand was soluble in DMSO, DMF and hot ethanol, but insoluble in chloroform, ethyl acetate, acetone, methanol, dichloromethane and distilled water, and all three compounds showed high thermal stability (>300 °C). Diagnostic infrared bands at 3572 and 3524 cm-1 (νNH2 and νOH) and UV bands at 48,300, 36,630 and 28,985 cm-1 (n→σ*, π→π* and n→π*, respectively) confirmed the identity of the free ligand. Complexometric titration gave experimental metal contents of 9.92% (Cu) and 9.82% (Ni), in good agreement with the theoretical values of 10.09% and 10.15%, consistent with 1:2 metal-to-ligand stoichiometry in both complexes. Coordination through the azomethine nitrogen was indicated by shifts in ν(C=N) to 1651 cm-1 and 1634 cm-1, together with new ν(M–N) bands at 435 cm-1 and 487 cm-1 for the Cu(II) and Ni(II) complexes, respectively. [Ni(NAD)2]Cl2 displayed an effective magnetic moment of 4.83 BM and a d–d transition at 25,000 cm-1, consistent with a high-spin tetrahedral d8 environment, while [Cu(NAD)2(OAc)2] gave a magnetic moment of 2.27 BM and a d–d transition at 15,267 cm-1, consistent with a Jahn–Teller-distorted octahedral d9 environment. Together, these results establish the NAD ligand as an effective bidentate N-donor for first-row transition metal ions.
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BibTeX
@misc{kolawole2026synthesis,
title = {{Synthesis, Spectroscopic Characterisation, and Structural Elucidation of Ni(II) and Cu(II) Complexes of a Novel N,N’-Diaminophthalamidoxime Ligand}},
author = {Emmanuel Oluwaseyi Kolawole and Oluwafunmilayo F. Adekunle},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008534/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008534/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Synthesis, Spectroscopic Characterisation, and Structural Elucidation of Ni(II) and Cu(II) Complexes of a Novel N,N’-Diaminophthalamidoxime Ligand
AU - Emmanuel Oluwaseyi Kolawole
AU - Oluwafunmilayo F. Adekunle
PY - 2026
DA - 2026/09/09
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008534/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008534/v1
AB - A new N,N’-diaminophthalamidoxime (NAD) ligand was synthesised by reacting hydrazine hydrate with diethyl phthalate to give phthalic dihydrazide, which was subsequently reacted with hydroxylamine to yield the target ligand. The ligand was reacted with Ni(II) and Cu(II) salts to give [Ni(NAD)2]Cl2 and [Cu(NAD)2(OAc)2], respectively. The ligand and its complexes were characterised by solubility studies, melting point determination, complexometric metal analysis, room-temperature magnetic susceptibility, and infrared and UV–Visible spectroscopy. The free ligand was soluble in DMSO, DMF and hot ethanol, but insoluble in chloroform, ethyl acetate, acetone, methanol, dichloromethane and distilled water, and all three compounds showed high thermal stability (>300 °C). Diagnostic infrared bands at 3572 and 3524 cm-1 (νNH2 and νOH) and UV bands at 48,300, 36,630 and 28,985 cm-1 (n→σ*, π→π* and n→π*, respectively) confirmed the identity of the free ligand. Complexometric titration gave experimental metal contents of 9.92% (Cu) and 9.82% (Ni), in good agreement with the theoretical values of 10.09% and 10.15%, consistent with 1:2 metal-to-ligand stoichiometry in both complexes. Coordination through the azomethine nitrogen was indicated by shifts in ν(C=N) to 1651 cm-1 and 1634 cm-1, together with new ν(M–N) bands at 435 cm-1 and 487 cm-1 for the Cu(II) and Ni(II) complexes, respectively. [Ni(NAD)2]Cl2 displayed an effective magnetic moment of 4.83 BM and a d–d transition at 25,000 cm-1, consistent with a high-spin tetrahedral d8 environment, while [Cu(NAD)2(OAc)2] gave a magnetic moment of 2.27 BM and a d–d transition at 15,267 cm-1, consistent with a Jahn–Teller-distorted octahedral d9 environment. Together, these results establish the NAD ligand as an effective bidentate N-donor for first-row transition metal ions.
ER -