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Synthesis and kinetics of sterically altered photochromic dithizonatomercury complexes
Following a previous study where 12 electronically altered dithizones were synthesized, here we report on attempts to synthesize 26 dithizones. The purpose was to explore the boundaries within which dithizones may be synthesized, explore spectral tuning possibilities, and investigate steric effects on the photochromic reaction of its mercury complexes. Contrary to expectation, large substituents like phenoxy groups increased the rate of the photochromic back-reaction. In the series H-, 2-CH3-, 4-CH3-, 3,4-(CH3)2-, 2-OC6H5-, and 4-OC6H5-dithizonatophenylmercury(II), the lowest rate of 0.0004 s-1 was measured for the 2-CH3 complex, while the rate for the 2-OC6H5 derivative was 20 times higher. A solvent study revealed a direct relationship between dipole moment and the rate of the back-reaction, while the relationship between temperature and rate is exponential, with t1/2 = 2 min 8 s for the 4-phenoxy complex. The crystal structures of two dithizone precursors, 2-phenoxy- and 4-phenoxynitroformazan, are reported. (Figure Presented).
Alabaraoye, Ernestine,Von Eschwege, Karel G.,Loganathan, Nagarajan
p. 10894 - 10901
(2015/02/19)

Synthesis and kinetics of electronically altered photochromic dithizonatophenylmercury(II) complexes
A series of phenyl-substituted dithizones were synthesized, and preparation of the corresponding series of photochromic phenylmercury(II) complexes is for the first time reported. Adaption of previous methods enhanced synthesis convenience and product yields. A single crystal X-ray data collection of the ortho-S-methyl nitroformazan reaction intermediate was done. ADF computed molecular orbitals of the title compound show the HOMO and LUMO orbitals stretching along the entire ligand. The spontaneous back reaction kinetics of dithizonatophenylmercury(II) was studied at varied concentrations, temperatures and in different solvents. An exponential correlation was found between the rate of reverse isomerization and temperature, while increased solvent polarity and decreased molar mass facilitate higher return rates. The kinetic study of the series of twelve electronically altered complexes yielded a lowest rate of 0.0002 s-1 for the ortho-methyl derivative, while the highest rate of 0.0106 s-1 was measured for the meta-methoxy derivative.
Von Eschwege, Karel G.
p. 159 - 166
(2013/03/13)

Chemical and electrochemical oxidation and reduction of dithizone
A non-aqueous electrochemical study of dithizone, H2Dz, 1, is compared with the chemical oxidation and reduction profile of this versatile ligand. Chemical oxidation of 1 by I2 initially leads to an isolatable disulfide-bridged species, (HDz)2, 22, but ultimately monomeric dehydrodithizone, Dz, 3, is formed. Electrochemically, in CH2Cl2/0.1 mol dm-3 [N(nBu)4][B(C6F5)4], two oxidation processes are observed for 1. Evidence of the electrochemical formation of the dimer 22 was found, but on a CV timescale the fully oxidized species, 22 oxidized, did not convert to the chemically stable species 3. Regeneration of 1 during an irreversible electrochemical reduction of the electrochemically generated fully oxidized species, 22 oxidized, was detected. Two further one-electron electrochemical irreversible reduction steps were also identified to ultimately generate H3Dz-, 8, one of the synthetic precursors to 1. In contrast, resolution and identification of the electron transfer steps of 1 in both dimethylsulfoxide, DMSO, or in CH2Cl2/0.1 mol dm-3 [N(nBu)4][PF6] were hampered by solvation and ion paring of [PF6]- especially with the oxidized species of 1. A metathesis of water-soluble potassium dithizonate, KHDz, 4b, led to lipophilic [N(nBu)4][HDz], 4c.
von Eschwege, Karel G.,Swarts, Jannie C.
scheme or table
p. 1727 - 1733
(2010/07/04)

Kinetics of release of dithizone from mercury(II) dithizonate by triphenylphosphine
Reaction of mercury(II) dithizonate with triphenylphosphine releases free dithizone in the presence of acetic acid and follows a pseudo-first order kinetics with rate constant, k=7.38 * 10-5 s-1.
Lobana, Tarlok S,Sidhu, M S,Kumar, Sanjeev,Singh, Randhir
p. 726 - 727
(2007/10/02)

One-Step Conversation of Mesoionic Olate to Thiolate by Lawesson's Reagent
Treatment of mesoionic olates with Lawesson's reagent provides a convenient one-step conversion to mesoionic thiolates.
Araki, Shuki,Goto, Tetsuya,Butsugan, Yasuo
p. 2977 - 2978
(2007/10/02)

Kinetic Studies of the Formation of Dithizone. Part-I. Alkali assisted Conversion of Phenylhydrazinium Phenylhydrazine Dithiocarbamate and Diphenylthiocarbazide
The kinetics of formation of dithizone (3) from phenylhydrazinium phenylhydrazine dithiocarbamate (1) and from phenylthiocarbazide (2) has been studied.The synthetic aspect of the formation of dithizone from phenylhydrazine and carbon disulphide has also been worked out.A mechanism for the formation of dithizone from 1 and 2 has been proposed.
Sarangi, B.,Misra, B. K.,Behera, G. B.
p. 979 - 982
(2007/10/02)

INVESTIGATIONS IN THE SERIES OF DITHIOCARBAMIC ACID DERIVATIVES. IX. ARYLHYDRAZINOTHIOCARBONYLATION OF COMPOUNDS CONTAINING AN ACTIVE HYDROGEN ATOM
The reaction of methyl phenyldithiocarbazate with ethyl cyanoacetate, cyanoacetamide, acetylacetone, and malonic ester leads to the formation of 1,4,5-trisubstituted pyrazoline-3-thiones.The reaction of methyl phenyldithiocarbazate with arylamines and arylhydrazines gave the respective derivatives of thiosemicarbazide and thiocarbohydrazide.
Bazavova, I. M.,Dubenko, R. G.,Pel'kis, P. S.
p. 189 - 193
(2007/10/02)

Substituent effects on the spectral behavior and synthesis of mercury 1,5-diarylthiocarbazonates
Symmetric and unsymmetric substituted 1,5-diarylthiocarbazones, and their mono- and bismercury complexes, were synthesized for spectral analysis.The first singlet-singlet transition of the mercury complexes was determined and the spectral shift produced by trifluoromethyl substitution was compared with that caused by different substituents in similar complexes.The large magnitude of the hypsochromic shift produced by the trifluoromethyl substituent can be explained by concerted steric and inductive effects, while the smaller bathochromic shift induced by the methoxy substituent is a result of opposing steric and electronic effects.In the trifluoromethyl substitution, a hypsochromic shift caused by steric influences was found to be 500 cm-1 in the photochromic unactivated state, and 250 cm-1 in the photochromic activated state.A similar shift caused by inductive influences was found to be 750 cm-1 in the photochromic unactivated state, and 600 cm-1 in the photochromic activated state.The smaller spectral shift observed in the photochromic activated state is consistent with the elucidated structure of the unsymmetric 1,5-diarylthiocarbazone, 6d, which was shown that the trifluoromethyl substitution was on the phenylazo portion of the molecule by chemical and spectral studies.
Chu, Nori Y. C.,Goldstein, Steven A.,Keehn, Philip M.
p. 679 - 687
(2007/10/02)