Zinc(II) and Copper(II) Complexes of Pentacoordinating (N4S) Ligands with Flexible Pyrazolyl Arms: Syntheses, Structure, and Redox and Spectroscopic Properties
Abstract:Zinc(II) and copper(II) complexes of two new potentially pentadentate ligands based on methyl 2-aminocyclopent-1-ene-1-dithiocarboxylate with pendent pyrazolyl groups (Me 2 pzCH 2 ) 2 NC 2 H 3 RNHC 5 H 6 CSSCH 3 (R ) H, Hmmecd, and R ) CH 3 , Hmmpcd, both having N 4 S donor atoms set) have been reported. The molecular structures of [Zn(mmpcd)]ClO 4 (1b) and [Cu(mmpcd)]ClO 4 (2b) show a distorted trigonal bipyramidal geometry for the Zn(II) ion and a square pyramidal geometry for the Cu(II) ion. 1b crystallizes… Show more
“…A square pyramidal geometry is proposed for the complex 8 based on the presence of two bands at 455 and 610 nm. These bands may be assigned to the 2 B 1 ← 2 A 1 and the 2 B 1 ← 2 E transitions, respectively, based on assignments published before [56, 57]. The value of the magnetic moment is in accordance with the previous results (1.83 BM).Fig.…”
A hydrazone Schiff base ligand was synthesized by the condensation of 3-formyl-4-hydroxycoumarin and oxalyldihydrazide in the molar ratio 2:1. The Schiff base ligand acts as a mono-, bi-, tri- or even tetradentate ligand with metal cations in the molar ratios 1:1 or 2:1 (M:L) to yield either mono- or binuclear complexes as keto or enol isomers, where M = Co(II), Ni(II), Cu(II), VO(IV), and Fe(III). The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, mass, and UV–Vis spectroscopy. Furthermore, the magnetic moments were calculated from the measured electric conductivities of the complexes. According to the received data, the dihydrazone ligand contains one or two units of ONO domains and can bind to the metal ions via the azomethine nitrogen, the carbonyl oxygen atoms, and/or the phenolic oxygen atoms. Electronic spectra and the magnetic moments of all complexes show that the complexes’ geometries are either octahedral, tetrahedral, square planar, or square pyramidal. Cyclic voltammograms of the mononuclear Co(II) and Ni(II) complexes show quasi-reversible peaks. Tests against two pathogenic bacteria as Gram-positive and Gram-negative bacteria for both, the Schiff base ligand and its metal complexes were carried out. In addition, also one kind of fungi was tested. The synthesized complexes demonstrate mild antibacterial and antifungal activities against these organisms.Graphical abstract
Electronic supplementary materialThe online version of this article (doi:10.1007/s00706-017-2075-9) contains supplementary material, which is available to authorized users.
“…A square pyramidal geometry is proposed for the complex 8 based on the presence of two bands at 455 and 610 nm. These bands may be assigned to the 2 B 1 ← 2 A 1 and the 2 B 1 ← 2 E transitions, respectively, based on assignments published before [56, 57]. The value of the magnetic moment is in accordance with the previous results (1.83 BM).Fig.…”
A hydrazone Schiff base ligand was synthesized by the condensation of 3-formyl-4-hydroxycoumarin and oxalyldihydrazide in the molar ratio 2:1. The Schiff base ligand acts as a mono-, bi-, tri- or even tetradentate ligand with metal cations in the molar ratios 1:1 or 2:1 (M:L) to yield either mono- or binuclear complexes as keto or enol isomers, where M = Co(II), Ni(II), Cu(II), VO(IV), and Fe(III). The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, mass, and UV–Vis spectroscopy. Furthermore, the magnetic moments were calculated from the measured electric conductivities of the complexes. According to the received data, the dihydrazone ligand contains one or two units of ONO domains and can bind to the metal ions via the azomethine nitrogen, the carbonyl oxygen atoms, and/or the phenolic oxygen atoms. Electronic spectra and the magnetic moments of all complexes show that the complexes’ geometries are either octahedral, tetrahedral, square planar, or square pyramidal. Cyclic voltammograms of the mononuclear Co(II) and Ni(II) complexes show quasi-reversible peaks. Tests against two pathogenic bacteria as Gram-positive and Gram-negative bacteria for both, the Schiff base ligand and its metal complexes were carried out. In addition, also one kind of fungi was tested. The synthesized complexes demonstrate mild antibacterial and antifungal activities against these organisms.Graphical abstract
Electronic supplementary materialThe online version of this article (doi:10.1007/s00706-017-2075-9) contains supplementary material, which is available to authorized users.
“…Distortion of the coordination sphere around the Zn II metal center from the ideal trigonal bipyramidal geometry, is manifested in: (i) the N(1)–Zn(1)–O(2) angle of 151.28(16)° which reflects the restricted bite angle of the ligand; (ii) the three equatorial angles ranging from 82.80(2)° to 143.00(2)°; and (iii) the axial–Zn(1)–equatorial angles comprised between 73.97(18)° and 113.97(17)° (Table ). Such distorted geometry has already been encountered for pentacoordinate Zn II species . The Zn–N bond lengths of the basal plane [2.005(4) and 2.039(5) Å] are much shorter than the axial one [2.391(5) Å].…”
Dedicated to the memory of our esteemed colleague Dr. Jean-Yves Pivan (ENSC Rennes), an enthusiastic chemist and brilliant supervisor.Abstract: A series of four new homoleptic Co II , Ni II , Cu II and Zn II complexes (1-4) of the type M(HL) 2 , where HLstands for the deprotonated form of the tridentate O,N,N-donor Schiff base ligand obtained by condensation between 8-hidroxy-2quinolinecarboxaldehyde and 2-aminophenol, have been prepared in yields ranging from 70 to 85 %. The five compounds were characterized using elemental analysis, FT-IR, ESI-MS, UV/ Vis, and 1 H and 13 C NMR spectroscopy (for the diamagnetic species H 2 L and Zn II complex 4). The molecular structures of H 2 L and its Ni II and Zn II complexes 2 and 4, respectively, were further confirmed by single-crystal X-ray diffraction methods. Xray crystal structure determination revealed that in complex 2, the six-coordinate Ni II metal ion adopts a N 4 O 2 distorted octa- [a]
“…The complexes exhibit a medium intensity band around 370-395 cm À1 which may be assigned to (Mo-S) [45]. Like most cis-dioxomolybdenum(VI) complexes, two IR bands are observed in the 1000-885 cm À1 region, the higher and the lower frequency bands originating from the anti-symmetric and the symmetric stretching modes of the [MoO 2 ] 2þ moiety [37,46,47]. 1 Similar observation for all types of protons is noted in case of (H 2 L 2 ) and its corresponding complex 2.…”
Several cis-dioxomolybdenum complexes of two tridentate ONS chelating ligands H 2 L 1 and H 2 L 2 (obtained by condensation of S-benzyl and S-methyl dithiocarbazates with 2-hydroxyacetophenone) have been prepared and characterized. Complexes 1 and 2 are found to be of the form MoO 2 (CH 3 OH) L 1 Á CH 3 OH and MoO 2 L, respectively, (where L 2-¼ dianion of H 2 L 1 and H 2 L 2 ). The sixth coordination site of the complexes acts as a binding site for various neutral monodentate Lewis bases, B, forming complexes 3-10 of the type MoO 2 LB (where B ¼ -picoline, imidazole, thiophene, THF). The complexes were characterized by elemental analyses, various spectroscopic techniques, (UV-Vis, IR and 1 H NMR), measurement of magnetic susceptibility at room temperature, molar conductivity in solution and by cyclic voltammetry. Two of the complexes MoO 2 (CH 3 OH) L 1 Á CH 3 OH (1) and MoO 2 L 1 (imz) (5) were structurally characterized by single crystal X-ray diffraction. Oxo abstruction reactions of 1 and 5 led to formation of oxomolybdenum(IV) complex of the MoOL type.
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