Synthesis, spectral and structural studies of novel binuclear Ni(II) complex of salicylaldehyde 3-azacyclothiosemicarbazone

Latheef, Leji; Seena, E.B.; Kurup, M.R. Prathapachandra

doi:10.1016/j.ica.2008.10.012

Cited by 13 publications

(5 citation statements)

References 23 publications

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“…The intense bands in the range 352–401 nm are assigned to metal‐to‐ligand charge transfer (LMCT) transitions (S → Ni). The other medium‐intensity bands in the range 416–430 nm are assigned to L → M (O → Ni) and ν 3 (d–d) bands 46. Complexes 11 and 12 showed π → π* and n → π* transitions at 279, 293, 307 nm.…”

Section: Resultsmentioning

confidence: 96%

The Effect of C‐2 Substituents of Salicylaldehyde‐Based Thiosemicarbazones on the Synthesis, Spectroscopy, Structures, and Fluorescence of Nickel(II) Complexes

et al. 2013

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The aim of this investigation was to study the bonding patterns, geometry, and fluorescence properties of nickel(II) complexes with salicylaldehyde‐based thiosemicarbazones [(2‐OH‐5‐R1‐C6H3)C(R2)=NNHC(=S)NHR3, LH2] by invoking the effect of substituents at the C‐2 and N‐1 atoms of the thio ligands and by using bipyridines/phenanthrolines as auxiliary ligands. The methodology used for the preparation of complexes involved initial binding of NiII with a thio ligand in an organic solvent to yield an insoluble solid of empirical composition [NiL], which was reacted further with a N,N‐donor ligand. In this way, we have prepared a series of dinuclear complexes and two mononuclear complexes with stoichiometries [Ni2L2(bipy)(D)] [bipy = 2,2′‐bipyridine, L = L1 (R1, R2, R3 = H), D = H2O 1; L = L2 (R1, R2 = H, R3 = Me), D = CH3OH 2; L =L3 (R1, R2 = H, R3 = Et), D = CH3OH 4; L = L3, D = H2O 5; L = L4 (R1 = Me, R2 = H, R3 = Me), D = CH3OH 6], [Ni2L32(bipy)] (3), [Ni2L32(dmbipy)(H2O)] (7, dmbipy = 4,4′‐dimethyl‐2,2′‐bipyridine), [Ni2L52(bipy)2] (8, R1 = NO2, R2 = H, R3 = Me), [NiL6(bipy)] (9, R1 = NO2, R2 = H, R3 = Et), [NiL7(bipy)(H2O)] (10, R1 = H, R2 = Me, R3 = Et), [Ni2L32(4,4′‐bipy)] (11, 4,4′‐bipy = 4,4′‐bipyridine), and [Ni2L72(4,4′‐bipy)] (12). The dinuclear complexes involve (i) O,N3,S chelation with bridging N2 atoms to form trigonal‐bipyramidal/square‐planar complexes with a five‐coordinate and a four‐coordinate Ni center (3, 5:4‐coordination) and octahedral/square‐planar complexes (1, 2, 4–7, 6:4‐coordination), (ii) O,N3,S chelation with S bridges to form octahedral/octahedral complexes (8, 6:6‐coordination), and (iii) O,N3,S chelation to form square‐planar/square‐planar complexes (11, 12, 4:4‐coordiantion). The mononuclear complexes involve O, N3,S chelation and have square‐pyramidal (9) and octahedral (10) geometries. Complexes 1–10 are paramagnetic with μeff value in the range 2.97–3.38 μB. Complexes 2 and 3 exhibit fluorescence emission.

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Section: Resultsmentioning

confidence: 96%

The Effect of C‐2 Substituents of Salicylaldehyde‐Based Thiosemicarbazones on the Synthesis, Spectroscopy, Structures, and Fluorescence of Nickel(II) Complexes

et al. 2013

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“…It has been proposed that this conjugation system enhances the biological activity of these compounds. 58 High-resolution X-ray diffraction experiments currently ongoing support this hypothesis (data not shown). These findings would suggest that the interaction of highly hydrophobic aromatic rings of TSCs is the primary arrangement.…”

Section: Aggregation Of Tscsmentioning

confidence: 87%

Self-aggregation behaviour of novel thiosemicarbazone drug candidates with potential antiviral activity

et al. 2010

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The present work aimed to gain further insight into the mechanisms governing the aggregation process of 1-indanone thiosemicarbazone drug candidates. Regardless of the relatively low lipophilicity predicted by theoretical calculations, these compounds were very insoluble in water. This performance was especially notorious for methoxylated (and non-N-allylated) derivatives. Thermal analysis revealed that the introduction of one and two CH 3 O-moieties into the aromatic ring increases the T m pronouncedly from 185 1C to 229 1C and 258 1C, respectively. The formation of nano-aggregates in water was suggested by the appearance of a new strong absorption peak at 233-239 nm in the UV spectra. DLS analysis showed the early formation nanoscopic particles (120-300 nm) that undergo a gradual size growth to generate larger submicron structures; these particles remained invisible to the naked eye. The negatively-charged character of the surface was established by zeta potential measurements. These results suggest the generation of an inner hydrophobic ''core'' due to the interaction of highly hydrophobic aromatic rings that is surface-decorated by CQS groups available in a thiolato anionic form. This aggregation mechanism is supported by the fact that methoxylation of the aromatic ring dramatically strengthens the solute-solute affinity, as expressed by the sharp increase in T m and makes these derivatives much more water-insoluble. Finally, overall findings indicate that for these compounds, solubility predictions based on lipophilicity calculations are not reliable and a more thorough characterization is required.

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“…opens the possibility of a tridentate NPy-N-S coordination with two five-ring chelates on the metal (Scheme 1B) [7][8][9][10]. Bi-or oligonuclear transition metal complexes of thiosemicarbazone ligands have been obtained frequently through S-bridging of the thiosemicarbazone ligands [3,4,8,[12][13][14][15][16][17][18][19][20]. Systematic formation of bi-or oligonuclear complexes through ligand design has successfully used functionalised mono-thiosemicarbazone ligands, such as the 2-(di(pyridyl-2-yl)thiosemicarbazone [13,21] or bis(thiosemicarbazone) ligands [4,5,9,[20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

“…Bi-or oligonuclear transition metal complexes of thiosemicarbazone ligands have been obtained frequently through S-bridging of the thiosemicarbazone ligands [3,4,8,[12][13][14][15][16][17][18][19][20]. Systematic formation of bi-or oligonuclear complexes through ligand design has successfully used functionalised mono-thiosemicarbazone ligands, such as the 2-(di(pyridyl-2-yl)thiosemicarbazone [13,21] or bis(thiosemicarbazone) ligands [4,5,9,[20][21][22][23][24][25][26][27]. For example, pyridine-2,6-bis(thiosemicarb azones) (Scheme 1C) have been synthesised to provide a potential S^N^N^N^S coordination for the metal [4,10,22,28,29] and were found to form binuclear complexes through S-bridging [22,29], but they largely fail to bridge two metal centres due to their preference for multi-dentate binding [4,10,22,28].…”

Section: Introductionmentioning

confidence: 99%

[2 × 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands

et al. 2018

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Tetranuclear complexes [M 4 (L R) 4 ] with M = Ni(II) or Zn(II), with a [2 × 2] grid-type structure, were assembled in good yields and purity from the easily accessible but unprecedented pyrazine-bridged bis(thiosemicarbazone) protoligands (ligand precursors) H 2 L R (1,4-pyrazine-2,5bis(R-carbaldehyde-thiosemicarbazone); R = Me, Et, i Pr, or Ph). The complexes were characterised in solution by NMR, MS, IR, and UV-Vis absorption spectroscopy and (spectro)electrochemical methods. HR-MS spectra unequivocally reveal that the tetranuclear species are very stable in solution and any measurements represent these species. Only at higher temperatures (fragmentation in solution: MS and in the solid: TG-DTA) or upon the addition of protons (acidic UV-Vis titrations) can the tetrameric entities be decomposed. Single crystal XRD measurement remained preliminary. Rapid loss of co-crystallised solvent molecules within the [2 × 2] grid-type structures resulted in crystals of very poor quality, but the results were qualitatively in line with spectroscopy, electrochemistry, and quantum chemical (DFT) calculations. IR and NMR spectroscopy point clearly to a thiolate coordination of dianionic (deprotonated) ligands. The electrochemistry reveals four electronically coupled and reversible one-electron reductions centred largely at the pyrazine bridges. EPR and UV-Vis spectroelectrochemical measurements in combination with DFT calculation support the assignment.

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Synthesis, spectral and structural studies of novel binuclear Ni(II) complex of salicylaldehyde 3-azacyclothiosemicarbazone

Cited by 13 publications

References 23 publications

The Effect of C‐2 Substituents of Salicylaldehyde‐Based Thiosemicarbazones on the Synthesis, Spectroscopy, Structures, and Fluorescence of Nickel(II) Complexes

The Effect of C‐2 Substituents of Salicylaldehyde‐Based Thiosemicarbazones on the Synthesis, Spectroscopy, Structures, and Fluorescence of Nickel(II) Complexes

Self-aggregation behaviour of novel thiosemicarbazone drug candidates with potential antiviral activity

[2 × 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands

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