V. A. Bren

Luminescent complexes with ligands containing C=N bond

Data on luminescent complexes with azomethine ligands are generalized and systematized. The synthesis and luminescent properties of complexes with acyclic and cyclic azomethines are considered.

Benzenoid-quinoid tautomerism of azomethines and their structrual analogues XXX. Molecular structure of gallium and boron organometalic compounds with tautomeric azomethines

Abstract The electronic structure and conformations of a systematic series of dimethylgallium and diphenylboron derivatives of aromatic and heterocyclic hydroxy- and mercaptoazomethines have been studied using the methods of electron absorption and emission spectroscopy and dipole moments. Although their phenyl- and methylmercury analogues tend to undergo tautomeric transformations, organometallic compounds of gallium and boron have in solution a mesomeric intra-complex structure with tetracoordinated gallium and boron. The molecular structure of two gallium chelates, dimethylgallium N-methylsalicylaldiminate and 2-(N-phenylaminomethylene)-3(2H)-benzo(b)furanthionate, have been determined by X-ray diffraction analysis. Structural parameters indicate that chelate formation causes a considerable redistribution of bond lengths in the ligand.

The novel azomethine ligands for binuclear copper(II) complexes with ferro- and antiferromagnetic properties

A series of novel binuclear ferro- and antiferromagnetic Cu(2+) chelates of structurally broadly varied Schiff bases (derived from o-tosylamino(hydroxyl)benzaldehydes and monoalkylated o-phenylenediamine, o-aminophenol, o-aminothiophenol, 1,2-diaminobenzimidazole, 1-aminobenzimidazoline-2-thione) and β-diketimines (derived from 2,6-di-i-Pr-aniline) has been prepared. The tautomerism of the ligands and structureof their copper complexes have been studied with the use of IR, 1H NMR EPR and EXAFS spectroscopy. Molecular and crystal structure of a β-diketimine copper dimer has been determined by X-ray crystallography. The magnetic measurements (2–300 K) performed for all the complexes showed that the ferro- and antiferromagnetic character of the exchange interaction depends both on the structure of the coordination site (origin of the ligating centers) and the structure of the ligands (in particular, on the type of the cycle annelated to the bridging fragment). Whereas S-binding metal chelates 13 (X = NTs, Y = S, R = H) are diamagnetic, the complexes 15 with annelated azole moieties are ferromagnetic.

Transmission of electronic effects in certain ployenes

Abstract The effect of substituent variation in compounds of the general type R(CHCH) n CHO ( 1 ) or p -RC 6 H 4 (CHCH) n CHO ( 2 ) on the stretching vibrations of the CHO group (ν co ), the dipole moments (μ), the long wave maxima (λ max ), and the halfwave potentials (E 1 2 ) for the polarographic reduction of the CHO group have been studied as well as the influence of variation of substituent R on the rate constants (k) of the alkaline hydrolysis of polyenic esters R(CHCH) n COOEt ( 3 ). A linear relationship between the σ + , σ c 0 or σ c + values and the experimental values of ν co , μ, gl max , E 1 2 and k has been established, which indicates the importance of the mesomeric mechanism of the transmission of electronic effects through the chain of conjugated double bonds in compounds 1 , 2 and 3 . Transmission coefficients (π′) for one (π′ 1F ), two (π′ 2F ), three (π′ 2F ), and four (π′ 4F ) double bonds were calculated, and it was found that these values are bound together by the ratio: (π′ 1F ):(π′ 2F ):(π′ 3F ):(π′ 4F ) = (π′ 1F ):(π′ 1F ) 2 :(π′ 1F ) 3 :(π′ 1F 4 , i.e. the influence of substituents R is decreased m a geometrical progression when the number of double bonds increases. The distribution of the electronic density in 1 was calculated by the LCAO SCF method in the Pariser-Parr-Pople approximation, and it was found that the π-electronic density values at the O atoms of the CHO group correlates well with σ c 0 constants and the calculated values of π′ 1F , π′ 2F , and π′ 3F are bound together by the above ratio.

Photochromic Cation Sensors

ABSTRACT Novel photochromic chemosensors for alkali-, alkali-earth and d-metal cations were synthesized and their photochemical and complexing properties investigated with the use of UV/vis, IR, 1H/7Li NMR spectroscopy and quantum chemical calculations – DFT(B3LYP/6-31G).

Synthesis of Novel Iono- and Photochromic Spiropyrans Derived from 6,7-Dihydroxy-8-Formyl-4-Methyl-2H-Chromene-2-One

�-hydroxy group were synthesized and their spectral properties as well as abilities for complexation with metal ions studied. In solutions they exist as equilibrium mixture of spirocyclic (A) and merocyanine (B) isomers. The largest content of merocyanine form was found for the derivative with an electron-donating methyl group in position 5 of hetaryl fragment. The irradiation of SPPs in acetonitrile shifts the equilibrium to the B form. Similar effect causes the addition of metal cations due to formation of colored complexes with merocyanine isomers.

Synthesis and photochromic properties of spiropyrans containing a fused benzopyranone fragment

New spiro compounds of the indole, phthalazine, isobenzofuran, and benzopyran series, containing a fused benzopyranone fragment in the chromene moiety, were synthesized. Indole derivatives were found to exhibit photochromic properties under stationary conditions at 293 K. The thermal stability of merocyanine isomers sharply decreases upon introduction of electron-withdrawing nitro group into the indole fragment and fusion of a benzene ring to the chromene fragment.

Chemosensors based on N -(9-anthrylmethyl)-benzene-1,2-diamine

A number of N-(9-antrylmethyl)-N′-arylmethylidenebenzene-1,2-diamines and 1-(9-anthrylmethyl)-2-aryl-1H-benzimidazoles were synthesized by condensation of N-(9-anthrylmethyl)benzene-1,2-diamine with aromatic and heterocyclic aldehydes. Study on their luminescent properties and complexing ability showed that 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-5-methylphenol, 2-{[2-(9-anthrylmethylamino)phenylimino] methyl}-4-methoxyphenol, and 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-6-methoxy-4-nitrophenol are effective and highly selective chemosensors for H+ and Hg2+ ions.

Complexing properties of ambidentate benzo-15-crown-5-substituted azomethine ligands

Crown-containing azomethines and their zinc complexes were prepared. Examination of their structure by 1H and 7Li NMR and electronic spectroscopy showed that, in accordance with the concept of hard and soft acids and bases, the hard lithium cation coordinates to the crown ether fragment with the formation of mono-(Li) and binuclear (Li, Zn) complexes.

Acylotropic intramolecular rearrangements of keto enamines of benzo[b]-annelated heterocycles

A review is devoted to N → O-acylotropic rearrangements of acylated keto enamines of benzo[b]furan, benzo[b]thiophene, benzo[b]selenophene, and benzo[b]tellurophene series. The mechanism of the photoinitiated migration of the acyl group and effect of the substituents in the migrating group and N-aryl fragment were examined. The compounds studied may be used as light energy accumulators, optical signal molecular switches, fluorescent sensors for measuring pH, and chemosensors for the determination of metal cations.