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.

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► (NH4)2S, altered reactant concentrations and reaction temperatures improve dithizone synthesis yield.
► The X-ray structure of the ortho-S-CH3 derivative is presented.
► ADF molecular orbital simulations of the title compound predict expected HOMO to LUMO bond degeneration at the CN axis of rotation.
► Return reaction kinetics of the photochromic species illustrates temperature, solvent and substituent dependence.