Synthesis and photochromic properties of 4-[2-(anthracen-9-yl)-5-methyloxazolyl] fulgide

New photochromic fulgide, viz., 4-{1-[2-(anthracen-9-yl)-5-methyloxazol-4-yl]ethylidene}-3-isopropylidenetetrahydrofuran-2,5-dione, with fluorescent properties was synthesized. Studies by electronic, IR, and ¹H NMR spectroscopy and X-ray diffraction demonstrated that this fulgide exists in the Z form. Light irradiation of its solutions at a wavelength of 365 nm causes Z/E isomerization giving rise to the thermally stable cyclic form. The latter is transformed into the starting E isomer under light irradiation at λ = 436 nm. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 97–101, January, 2006.     

Structure and photochemical properties of 2-(N-benzoyl-N-phenylaminomethylene)- and 2-(N-p-nitrobenzoyl-N-phenylaminomethylene)-3(2H)-benzo[b]thiophenones

Conclusions It was established by x-ray crystallographic investigation that the inhibition of the photochromism of the nitro derivative (IIb) compared with compounds (I) and (IIa) is due to the difference in the structure of the molecules and to the realization of the low-lying triplet n^* state, due to the presence of the p-nitro group. The flattening of the p-nitrobenzoyl fragment and its rotation from the plane of the molecule evidently promote localization of the photoexcitation energy in this conjugated fragment of the molecule and lead to nonradiative deactivation of the excited S^1* state by intercombination conversion through the n triplet state and, finally, to a marked decrease in the yields of the fluorescence and the phototransformations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1544–1548, July, 1989.The authors are grateful to M. I. Knyazhanskii for assistance in the discussion of the results.     

Benzoid-quinoid tautomerism in azomethines and their structural analogs. 46. Synthesis and reactions of 2-(N-isatinomethylene)-3(2H)-benzo[b]thiophenone

Electronic, IR and UV spectroscopy has shown that 2-(N-isatinomethylene)-3(2H)-benzo[b]thiophenone in solution displays photo- and solvatochromism as a result of reversible E Z isomerization, and it readily undergoes alcoholysis of the lactam bond. The resulting aminovinyl ketones exist as mixtures of the thermodynamically stable E- and Z-isomers.For Communication 45, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1217–1220, September, 1989.     

Structure and photochromism of 2-(<Emphasis Type="Italic">N</Emphasis>-acyl-<Emphasis Type="Italic">N</Emphasis>-arylaminomethylene)benzo[<Emphasis Type="Italic">b</Emphasis>]thiophen-3(2<Emphasis Type="Italic">H</Emphasis>)-ones

It was shown by electron absorption spectroscopy and X-ray diffraction analysis that steric strains in photochromic 2-(N-acyl-N-arylaminomethylene) benzo[b]thiophen-3(2H)-one molecules ortho-substituted in the N-phenyl ring increase the quantum yield of the N→O photoinduced rearrangement in accord with an increase in the steric constant of the ortho-substituent.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2151–2155, October, 2004.     

Photoinduced Acylotropic Rearrangement of Crown-Containing 2-[N-Acetyl-N-(4-aminobenzo-15-crown-5)methylene]-2,3-dihydrobenzo[b]thiophen-3-one

2-N-(4-Aminobenzo-15-crown-5)methylene-2,3-dihydrobenzo[b]thiophen-3-one and its acetyl derivative were synthesized. Their treatment with lithium, sodium, or potassium iodide in acetonitrile solution leads to formation of the corresponding crown-metal complexes. Irradiation of the acylated compounds at 436 nm induces NO migration of the acetyl group to give O-acyl isomer which is characterized by a considerable blue shift of the long-wave absorption band ( = 70 nm). The quantum yields of the photo- induced acylotropic reaction for the free ligand and its complexes with alkali metal cations change in the series: _L > K⁺ > Na⁺ > Li⁺.     

A Voltammetric Study of the Chemosensor Activity of Aminoanthracene Derivatives

The redox activity of potent chemosensors based on anthryl-containing diamines, thioureas, and ureas in the absence and in the presence of complexing metal cations in solution was studied by cyclic and differential pulse voltammetry. The free energy of intramolecular electron transfer was calculated. The experimental conclusions were confirmed by ab initio RHF/6-31G** calculations. A correlation was found between the electrochemical and photophysical data for the compounds studied.     

Synthesis and photochromic properties of N 2-alkyl-5-furyl-4-thienylpyridazinones

New dihetarylethenes containing the six-membered bridging moiety, viz., N ²-alkyl-5-furyl-4-thienylpyridazinones, were synthesized. These compounds have photochromic properties in solution. The hindered rotation of the thiophene and furan rings around the single bonds that link these rings to the double bond of the pyridazinone moiety results in the formation of mixtures of chiral diastereomers in solution, the lifetimes of the diastereomers being no longer than 0.2 s. The photochromic rearrangement of pyridazinones is characterized by the highly efficient photocoloration and the photobleaching, which is an order of magnitude less efficient, in the absence of thermal relaxation processes.     

<Emphasis Type="Italic">N,N′</Emphasis>-Bis(9-anthrylmethyl)diamines as fluorescent chemosensors for transition metal cations

N,N′-Bis(9-anthryl)-substituted diamines, imidazolidines, and hexahydropyrimidines were synthesized, and their luminescence properties and complexing ability were studied. N,N′-Bis(9-anthrylmethyl)ethane-1,2-diamine and N,N′-bis(9-anthrylmethyl)butane-1,4-diamine were found to be effective and selective PET chemosensors for Zn²⁺ and H⁺, respectively. 2-[1,3-Bis(9-anthrylmethyl)hexahydropyrimidin-2-yl]-6-methoxyphenol can be used as fluorescent chemosensor for mercury(II) cations.     

Synthesis and structure of 1-[(3-hydroxybenzo[<Emphasis Type="Italic">b</Emphasis>]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide

Potentially tautomeric azomethine imine, 1-[(3-hydroxybenzo[b]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide has been prepared. According to X-ray diffraction, ¹H, ¹³C, and ¹⁵N NMR and electronic spectroscopy, the compound exists as 3-hydroxybenzothiophene structure containing intermolecular hydrogen bond between the hydroxy group and the carbonyl oxygen of the pyrazolidone ring in crystal state. Quantum chemical calculations predict the possibility of OH and NH tautomeric forms.