Formazans and their metal complexes

Sigeikin, G. I.; Lipunova, G. N.; Pervova, I. G.

doi:10.1070/rc2006v075n10abeh003612

Cited by 52 publications

(47 citation statements)

References 37 publications

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“…3. 1 The compounds 5a-5g, in accordance with the figures in literature, produced wide bands between l max1 of 494-554 nm in various polarity solvents, which belong to the characteristic p-p* transitions in the formazan skeleton and demonstrated the existence of a six-membered ring in the formazan skeleton due to the inner-molecular hydrogen transfer (Scheme 2). 42,43 Because the formazan skeleton has a structure showing tautomerization, the characteristic bands belong to the p-p* transitions (Fig.…”

Section: Absorption Spectrasupporting

confidence: 83%

“…3a-3h were characterized using FTIR, 1 H NMR, 13 C NMR and elemental analysis (see ESI †). 3a-3h were characterized using FTIR, 1 H NMR, 13 C NMR and elemental analysis (see ESI †).…”

Section: Synthesismentioning

confidence: 99%

“…1 Numerous studies have been undertaken related to their syntheses, structural and spectroscopic properties, 2-5 photochemical transformations, 6,7 tautomer formation, 8,9 the synthesis of crown formazans 10 and the broad spectrum of biological activities. 1 Numerous studies have been undertaken related to their syntheses, structural and spectroscopic properties, 2-5 photochemical transformations, 6,7 tautomer formation, 8,9 the synthesis of crown formazans 10 and the broad spectrum of biological activities.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, crystal structure, optical and electrochemical properties of novel diphenylether-based formazan derivatives

2015

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In this study, formazans 5a-5h were synthesized by coupling the reactions of substituted phenylhydrazone compounds 3a-3h with diazonium salt of 4-chloro-2-phenoxybenzenamine (4). The substituted phenylhydrazones 3a-3h were obtained from the condensation of substituted phenylhydrazines 1a-1h with 4-methoxybenzaldehyde (2). The structures of the formazans were characterized by using elemental analysis, FTIR, 1 H NMR, 13 C NMR, LC-MS and the crystal structure of compound 5e was determined by X-ray crystallography. The absorption spectra of all compounds were investigated in various solvents. Although their absorption bands are only slightly dependent on the polarities of solvents, the significant change was observed by altering the electronic characteristics of the substituents. The fluorescence quantum yield properties and Stokes shifts of compounds 5a-5h in DMSO were also explored. Electrochemical properties of the new products were studied by CV measurements. In addition, computational studies were conducted at the PBE1PBE/6-311g (2d,2p) level to shed light on the structures of possible tautomers and intramolecular H-bonds.Scheme 1 Synthetic route for the formation of formazan derivatives 5a-5h.Scheme 2 Intramolecular hydrogen bonding and tautomerisation of the formazan system. View Article Onlinea Oxidation and reduction potentials from cyclic voltammograms. b Onsets of oxidation and reduction. c HOMO = À(E onset (ox) + 4.4) (eV), LUMO = À(E onset (red) + 4.4).Scheme 4 (a) Schematic representation of the structure of 5c for possible oxidation mechanisms of 5c, 5d, 5g and 5h; (b) structure of 5a for possible oxidation mechanism of 5a, 5b, 5e and 5f.

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Section: Absorption Spectrasupporting

confidence: 83%

“…3a-3h were characterized using FTIR, 1 H NMR, 13 C NMR and elemental analysis (see ESI †). 3a-3h were characterized using FTIR, 1 H NMR, 13 C NMR and elemental analysis (see ESI †).…”

Section: Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis, crystal structure, optical and electrochemical properties of novel diphenylether-based formazan derivatives

2015

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“…Sigiekin et al [154] has designated the configuration of formazan in terms of E and Z instead of cis, trans or syn, anti. …”

Section: World Journal Of Pharmaceutical Researchmentioning

confidence: 99%

“…[160] The C=N stretching band at 1551-1561 cm -1 shows non-chelate structure. [161] The shift of these bands to higher frequencies is attributed to the loss of resonance stabilization of the sixmembered chelate ring due to the rupture of hydrogen bond.…”

Section: Spectral Propertiesmentioning

confidence: 99%

Frontiers of Formazans Chemistry: A Review

Kumar¹

2017

WJPR

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Formazanate Complexes of Hypervalent Group 14 Elements as Precursors to Electronically Stabilized Radicals

et al. 2018

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The stability of molecular radicals containing main‐group elements usually hinges on the presence of bulky substituents that shield the reactive radical center. We describe a family of Group 14 formazanate complexes whose chemical reduction allows access to radicals that are stabilized instead by geometric and electron‐delocalization effects, specifically by the square‐pyramidal coordination geometry adopted by the Group 14 atom (Si, Ge, Sn) within the framework of the heteroatom‐rich formazanate ligands. The reduction potentials of the Si, Ge, and Sn complexes as determined by cyclic voltammetry become more negative in that order. Examination of the solid‐state structures of these complexes suggested that their electron‐accepting ability decreases with increasing size of the Group 14 atom because a larger central atom increases the nonplanarity of the ligand‐based conjugated π‐electron system of the complex. The experimental findings were supported by density‐functional calculations on the parent complexes and the corresponding radical anions.

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Formazans and their metal complexes

Cited by 52 publications

References 37 publications

Synthesis, crystal structure, optical and electrochemical properties of novel diphenylether-based formazan derivatives

Synthesis, crystal structure, optical and electrochemical properties of novel diphenylether-based formazan derivatives

Frontiers of Formazans Chemistry: A Review

Formazanate Complexes of Hypervalent Group 14 Elements as Precursors to Electronically Stabilized Radicals

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