Metal complexes of iminodiacetamide (imda) ligands and metal ions Zn(II), Cu(II), Ni(II) and Co(II) were prepared, using eight imda ligands (L1-L8) substituted with groups of different steric and electronic properties on the central amine nitrogen atom (hydrogen atom, methyl, isopropyl, benzyl) and the para-position of phenyl rings (nitro, dimethylamino). The effect of these substituents on the stoichiometry (ML, ML2), geometry and stereochemistry (mer, transfac, cis-fac) of the complexes was studied in solid state, in solution and by DFT calculations. X-Ray single crystal and powder diffraction, thermogravimetry, and IR spectroscopy showed that in the solid state imda ligands preferentially form transfac ML2 complexes, with the exception of the cis-fac complex 7Zn. NMR spectroscopy of diamagnetic Zn(II) and paramagnetic Co(II) complexes revealed the formation of both ML and ML2 complexes in solution. Variable temperature NMR was used to study the effect of the substituent on the central amine nitrogen on the Zn─N bond strength and nitrogen inversion. Relative stabilities of isomers were rationalized by computations and the optimized structures used for the geometry analysis.
A variety of structurally
different complexes of the isopropyl-bis(2-picolyl)amine
(
i
Pr-bpa) ligand were prepared
with ZnA2 and CuA2 salts (A = Br–, Br–/PF6
–, BF4
–/F–, ClO4
–). The choice of different counterion affected the
stoichiometry, coordination number, geometry, and formation of geometrical
isomers. Crystal structures of four Zn(II) complexes, namely, two
monomers (
mer
-[Zn(
i
Pr-bpa)Br
2
] and
fac
-[Zn(
i
Pr-bpa)Br
2
]), one F–-bridged dimer ([Zn
2
(μ-F)
2
(
i
Pr-bpa)
2
](BF
4
)
2
), and one ML
2
complex ([Zn(
i
Pr-bpa)
2
](ClO
4
)
2
) were determined, and their solution structures were
studied by NMR spectroscopy. For the ML
2
complex, relative stabilities of geometrical isomers were
determined using density functional theory calculations. For Cu(II)
complexes, five crystal structures were determined, namely, two monomers
([Cu(
i
Pr-bpa)Br
2
] and [Cu(
i
Pr-bpa)(ClO
4
)
2
(H
2
O)]), a Br–-bridged
dimer ([Cu
2
(μ-Br)(Br)
2
(
i
Pr-bpa)
2
](PF
6
)), a F–-bridged
coordination polymer ([Cu(μ-F)(
i
Pr-bpa)]
n
(BF
4
)
n
× nCH
3
OH), and a cyclic,
CO3
2–-bridged trimer ([Cu
3
(tri-μ-CO
3
)(ClO
4
)
3
(
i
Pr-bpa)
3
](ClO
4
)). The different crystallographic
structures of Cu(II) complexes are reflected in their different magnetic
properties investigated by electron spin resonance spectroscopy and
magnetic susceptibility measurements.
Ferrocene derivatives with mono‐ (8a–c) and bis‐1,2,3‐triazolyl (9 and 10a–13c) chelating groups were synthesized by regioselective copper(I)‐catalysed 1,3‐dipolar cycloaddition of terminal alkynes with ferrocene azides. Metal complexes of the ligands were prepared with Cu(II) and Zn(II) salts. Crystal structures of ligands 9 and 11a were determined, as well as the structures of complexes [Cu(8a)2](CF3SO3)2 (8aCu) and [Cu(8c)2(CH3OH)2](BF4)2 (8cCu). In addition to NMR and UV–Vis spectroscopy, the metal complexes were characterized by cyclic voltammetry. The cytotoxic effect of ferrocene conjugates and their Zn(II) and Cu(II) complexes was explored, and cell cycle analysis was performed. The complex [Cu(8c)2](CF3SO3)2 showed the most prominent and selective cytotoxicity on cervical carcinoma (HeLa), ovarian cancer (MES‐OV), non‐small cell lung cancer (A549) and breast carcinoma (MDA‐MB‐231) cells. This complex increased cell population in the S and G2/M phase of the cell cycle, which was accompanied by an increase of the cells present in the sub‐G0/G1 fraction.
Click chemistry is a simple way of preparing a wide scope of ligands that can coordinate metals such as Cu(ii) and Zn(ii), forming complexes of different stoichiometries, geometries and stereochemistries.
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