Investigations in the benzazole and naphthazole series

1-[4(7)-Benzimidazolyl]-5-phenyl- and 1-[4(7)-benzimidazolyl]-5-(2-benzimidazolyl)formazans, which are isomers of the previously obtained 1-(2-benzimidazolyl)-5-phenyl- and 1,5-di(2-benzimidazolyl)formazans, were synthesized. Structural problems (tautomerism and hydrogen bonding) of the new formazans are discussed.See [1] for communication XXXV.Translated from Khimiya Geterotsiklicheskikh Soedinenii,,No. 8, pp. 1138–1140, August, 1972.     

Transition metal complexes of 3-cyano- and 3-nitroformazans

The synthesis and characterization of six transition metal complexes of 3-cyano- and 3-nitroformazans are described. Three different formazans were reacted with nickel(II) to produce complexes with bidentate formazan ligands. Mononuclear NiL2 (L = deprotonated formazan) or binuclear hydroxo-bridged (LNi)2(mu-OH) 2 species were produced depending on the steric bulk on the formazan N-aromatic substituents. 1,5-Bis(2-methoxyphenyl)-3-cyanoformazan acts as a tetradentate monoanionic ligand in a copper(II) complex, whereas the analogous 1,5-bis(2-hydroxyphenyl)-3-cyanoformazan binds as a trianion in a tetradentate manner to Fe(III) and Co(III). Crystal structures-the first examples of metal complexes of cyano- or nitroformazans-as well as the electronic spectra of the complexes are discussed in relation to each other as well as that of the uncoordinated formazans.     

Synthesis,structure, and tautomerism of formazans that contain 1-aryl-2-benzimidazolyl residues

1,5-Bis(1-aryl-2-benzimidazolyl)-3-methyl- and 1-(p-tolyl)-3-methyl-5-(1-aryl-2-benzimidazolyl)formazans were synthesized. It was shown by IR spectroscopy (from the change in the spectral characteristics of the NH, groups) that the formazans exist in the imino form in solutions in CCl₄, whereas a tautomeric equilibrium between the amino and imino forms of the investigated compounds is observed in solutions in CHCl₃. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 818–821, June, 1980.     

Investigations in the benzazole and naphthazole series

1-Benzazolyl-3-methyl-5-(p- or o-)tolylformazans (benzazolyl residues: 1-benzylbenzimidazole, benzothiazole, benzoxazole) have been synthesized and their structures have been studied by IR and UV spectroscopy. It has been found that in solutions the formazans are present in the open form and do not contain a chelate ring. Formazans containing an o-tolyl residue do not differ in respect of the structure of the formazan chain from their p-tolyl isomers, but in solutions of the complexes with nickel and copper the influence of the ortho methyl group is shown in the higher coloration of the complex of the ortho isomer than of the para isomer.     

Investigations in the benzazole and naphthazole series XXIV

The structure of the chelate ring and the tautomerism of unsymmetrical 1-benzazolylformazans depends on the nature (basicity) of the heterocycle and on the nature of the substituent (methyl, phenyl) in position 3. Analogs of 3-methyl-1, 5-diphenylformazan containing 1-benzylbenzimidazolyl, benzothiazolyl, or benzoxazolyl groups have an open structure of the formazan chain without an intromolecular hydrogen bond (IHB) while in the case of a benzimidazolylformazan the tautomeric form with hydrogen attached to the heterocyclic nitrogen atom predominates in solution. Of the analogs of triphenylformazan, 1-(1-benzylbenzimidazolyl)-3, 5-diphenylformazan also has an open structure, but 1-benzoxazolyl-3, 5-diphenylformazans have a chelate structure with a weak IHB. Conclusions have been drawn from the IR and UV spectra and from determinations of the ionization constants of the formazans. In the formazans of the benzimidazole series, the phenomenon of the photoisomerization of the red form of the formazan into a blue form when solutions in carbon tetrachloride are irradiated with visible light has been found. It has been shown that the blue form produced is a dimer of the formazan.For part XXIII, see [1].     

Benzazoles and naphthazoles XXXV. Autooxidative coupling of 1-benzyl-2-hydrazinobenzmidazole with nitroformaldehyde arylhydrazones

1-Benzyl-2-hydrazinobenzimidazole undergoes autooxidative coupling with nitroformaldehyde arylhydrazones to give meso-carbon-unsubstituted 1-(1-benzyl-2-benzimidazolyl)-5-arylformazans (instead of the expected formazans with a nitro group in the meso position). Data on the structures and complexing abilities of the new unsymmetrical formazans of the benzimidazole series are presented.See [1] for communication XXXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 393–395, March, 1972.     

Benzazoles and naphthazoles

1-Benzothiazolyl-5-(p-nitrophenyl)formazans, which have thermochromic properties, were synthesized. The structure of the compounds was studied by means of IR and UV spectroscopy and quantum-mechanical calculations, the state of the tautomeric equilibrium was established, and the most probable planar conformations of the formazans as a function of the character of the substituent in the 3-position of the formazan chain were found. It is shown that the thermochromism of these compounds in solution is related to dissociation of the hydrogen of the NH bond of the formazan grouping and that the deeply-colored thermally induced form is the anionic aci form.     

Structural and spectral properties of 3-substitutedphenyl-1,5-diphenylformazans: A quantum chemical study

The structural and optical properties of 3-substitutedphenyl-1,5-diphenylformazans are studied by quantum chemical methods. The density functional theory (DFT) is employed to optimize the ground state geometries of formazans substituted with different electron donating and withdrawing groups in both gas and solvent phases. The absorption spectra of formazan derivatives are calculated using time dependent density functional theory (TD-DFT). The polarizable continuum model (PCM) calculations of 3-substitutedphenyl-1,5-diphenylformazans are performed for bulk solvent effects. The geometrical parameters, vibrational frequencies, and relative stabilities of isomers of 3-substitutedphenyl-1,5-diphenylformazans are studied. The results obtained by TD-DFT calculations reveal that the substitution of electron withdrawing and donating substituents affects the absorption spectra of 3-substitutedphenyl-1,5-diphenylformazans. The calculated maximum absorption wavelengths (λ_max) are highly consistent with the experimental values as found from UV-vis spectra.     

Structure of 1-aryl-3-alkyl-5-(2-benzothiazolyl)formazans

The isomeric and tautomeric structures of 1-aryl-3-alkyl-5-(2-benzothiazolyl)formazans in solutions were investigated by means of NMR, IR, and electronic spectroscopy. It is shown that the nature of the solvent and the alkyl substituent in the 3 position affects the ratio of the Z and E isomers relative to the C=N bond of the azohydrazone chain. An increase in the length of the alkyl substituent in the 3 position leads to preponderance of the Z isomer in solution, while branching stabilizes the Z configuration with an N²...HN⁵ intramolecular hydrogen bond (IMHB), regardless of the solvent. The nature of the solvent has a significant effect on the ratio of the amino and imino tautomeric forms of the E isomers. The benzothiazolylhydrazone form predominates in CHCl₃, while the tautomer with a benzothiazolidene fragment is the major form in DMSO.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 834–839, June, 1993.     

Synthesis and characterization of 3-cyano- and 3-nitroformazans, nitrogen-rich analogues of beta-diketimine ligands

The synthesis and characterization of several formazans containing strong electron-withdrawing substituents (cyano and nitro) in the 3 position of the ligand backbone are described. Reactions of aryldiazonium cations with the conjugated bases of either cyanoacetic acid or nitromethane lead to 1,5-diaryl-3-cyano- or 3-nitroformazans, respectively. When these reactions are carried out in aqueous conditions, the range of aromatic groups is limited by the stability of the diazonium salt. However, 3-nitroformazans containing bulky substituents on the nitrogen atoms (2,6-dimethylphenyl, 2,4,6-trimetyhlphenyl, 2,6-diisopropylphenyl, and 3,5-ditert-butylphenyl) could be made by performing the reactions under nonaqueous and anhydrous conditions. NMR and electronic spectroscopic studies indicate that the 3-nitroformazans exist exclusively as closed ( trans-syn, s-cis) isomers whereas the 3-cyanoformazans exist as mixtures of isomers which are substrate-dependent. The crystal structures of five of the formazans are presented: two 3-nitroformazans, both of which are closed, and three 3-cyanoformazans, two of which are closed and one of which adopts an open ( trans-syn, s-trans) structure. Solid state (diffuse reflectance) spectroscopy has been employed to ascertain the isomeric preferences of the other formazans which could not be crystallographically characterized.     

1,1-二(2-苯并咪唑基)-2-苯基乙烯衍生物荧光受体的合成与阳离子识别

合成了3种新型1,1-二(2-苯并咪唑基)-2-苯基乙烯衍生物——1,1-二(2-苯并咪唑基)-2(4-氰基苯基)乙烯(1)、1,1-二(2-苯并咪唑基)-2(4-甲氧羰基苯基)乙烯(2)和1,1-二(2-苯并咪唑基)-4-苯基-1,3-丁二烯(3),通过核磁共振氢谱和碳谱(1H、13C NMR)、质谱(MS)对它们进行了结构表征。用紫外可见吸收光谱(UV-V is)和荧光发射光谱测定了该阳离子受体与不同金属离子(Zn2 、Cd2 、Hg2 和Cu2 )的络合选择性。结果表明:该荧光受体对Zn2 、Cd2 、Hg2 和Cu2 均具有较高的选择性和荧光响应。     

Laser photolysis study of 1-aryl-3-methyl-5-(benzothiazole-2-yl) formazan phototransformation

Photochromism of 1-aryl-3-methyl-5-(benzothiazole-2-yl)formazans in toluene has been investigated by the laser flash photolysis method. It was established that the photochromic transformations involve the triplet state of the initial chelate form of formazans. The intermediate short-lived products of phototransformation were detected that could be related to one of the conformers or to the tautomers of the formazan molecule.     

Carbene-carbene rearrangements as a route to 1,5-dihydropentalene

1,5-Dihydropentalene (4) is formed as the main product on treatment of trans-1,2-bis(2,2-dibromocyclo-propyl)ethene 3 with methyllithium at −40°. In addition the reaction affords 1- and 2-propadienylcyclopentadienes (5a) and (5b), and trans-1,2,4,6,7-octapentaene (6), new C₈H₈ isomers. Diels-Alder adducts of 4, 5a and 5b were obt in the reaction with perfluorobut-2-yne. The formation of 1,5-dihydropentalene 4 is explained by a double ring expansion sequence involving consecutive carbene-carbene rearrangements with 1,3-carbon and subsequent 1,2-hydrogen shifts, supported by the reaction of double labelled (¹³C-depleted) 3. From readily available 3 at low temperatures formation and fusion of two 5-membered rings are achieved in one step.     

Gas-phase oxidation and reduction of some 1-(2-benzothiazolyl)-3,5-diphenyl formazans. Complex formation with transition metals under laser desorption ionization

Five differently substituted 1-(2-benzothiazolyl)-3,5-diphenyl formazans were studied by laser desorption ionization (LDI) and matrix assisted laser desorption/ionization (MALDI) mass spectrometry. The best explanation of the results is that the formazan molecules are photoionized to molecular radical ions, which then further react by ion-molecule reactions. Supporting this proposal was the abundant formation of [M − H]⁺ ions under LDI. These ions are not observed at all under either electron or chemical ionization. Under MALDI, the extent of the oxidation process is clearly dependent on the ability of the matrix to act as a reducing agent. With transition metals the formazans formed singly charged 1:2 metal:formazan complexes. The most stable electronic configuration of the complex determined the oxidation state of the metal regardless of its initial oxidation state. In some cases, this process also demanded a gas-phase reduction of the formazan. The ionization efficiency and affinity for complex formation depended on the substituent at the 3-phenyl group; both were increased by an electron donating substituent. The formazans were also tested as potential matrices for MALDI. Reasonable results were observed for several groups of compounds; however, only the piperazine ligands produced higher quality spectra with formazans than with common commercial matrices.     

Spectral and electrochemical behavior of 1-[(NO2, COOH)-substituted phenyl]-3,5-diphenylformazans

Abstract  

1-[(NO₂, COOH)-substituted phenyl]-3,5-diphenylformazans were synthesized. The compounds were characterized by infrared (IR), ultraviolet–visible (UV–vis), ¹H nuclear magnetic resonance (NMR), ¹³C NMR spectra, elemental analysis, and cyclic voltammetry. From the UV–vis spectra of substituted formazans it was seen that λ _max values were shorter than the λ _max value of unsubstituted formazan. It was observed that the shift values were dependent on the type and position of the substituents. A correlation between Hammett substituent coefficients and λ _max values was obtained. The oxidation peak potentials of substituted formazans were found more anodic than that of unsubstituted formazan. The oxidation mechanism was a single step for the NO₂-substituted formazans, and two steps for COOH-substituted formazans.     

Mesogenic behaviour of isomeric bent-core 6-oxoverdazyls: 1,3-vrs 1,5-substitution pattern

Two series of isomeric bent-core derivatives of 6-oxoverdazyl, with alkyl and partially fluorinated alkyl chains, were investigated by thermo-optical, powder X-ray diffraction and electron paramagnetic resonance methods in the pure state and binary mixtures. The results revealed that the substitution position of the arms at the verdazyl ring (1,5 vs. 1,3) strongly affects mesogenic behaviour. Steric (torsion and bending angles) and dipolar factors in both isomers are considered.     

Synthesis and spectral properties of n-alkyl-4-methyl-7(8)-nitro-2,3,4,5-tetrahydro-(1h)-1,5-benzodiazepin-2-ones

Alkylation of 4-methyl-7(8)-nitro-2,3,4,5-tetrahydrobenzodiazepin-2-ones under phase transfer catalytic conditions or in dry acetone occurs only at position 1. The 5-alkyl isomers are obtained by reductive alkylation of 4-methyl-7(8)-nitro-2,3-dihydro-1,5-benzodiazepin-2-ones. The UV, IR, PMR, and mass spectra of the isomeric compounds are reported.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 959–963, July, 1992.     

Semiconducting 2,6,9,10-tetrakis(phenylethynyl)anthracene derivatives: effect of substitution positions on molecular energies

2,6-Bis((4-hexylphenyl)ethynyl)-9,10-bis(phenylethynyl)anthracene, 4, and 9,10-bis((4-hexylphenyl)ethynyl)-2,6-bis (phenyl ethynyl)anthracene, 5, have been synthesized to study their electronic and photophysical properties. It should be noted that the difference between these compounds is the substitution position of 1-ethynyl-4-hexylbenzene groups into an anthracene ring. In particular, substitution in the 9,10-positions of the anthracene ring enhanced J-aggregated intermolecular interactions. Since 5 has a lower bandgap energy and more compact film morphology, it exhibited higher hole mobility (～0.27 cm(2) V(-1) s(-1)) in thin-film transistor devices.     

Discovery of Novel D‐A and D‐π‐A Structured Carbazole‐Based Formazan Dyes: Synthesis,Characterization, and Spectroscopic Studies

In the current study, new carbazole‐based formazan dyes, D‐A and D‐π‐A, were synthesized, and their spectroscopic properties were studied for the first time. For this aim, carbazole aldehyde compounds were modified by the derivatization of carbazole, a natural electron‐donor compound, from 3‐ and 9‐position. Then, hydrazone derivatives were synthesized from these aldehyde derivatives. Finally, D‐A ( 5A–C ) and D‐π‐A ( 6A–C ) carbazole–formazan dyes were obtained by the interaction of the hydrazone compounds with p‐substituted aniline. After characterization of the structures of these compounds, photophysical properties of the carbazole–formazans were studied in the different polarity media (i.e., acetonitrile, toluene, and chloroform) in order to detect the solvent effects. Because of the π‐conjugated bridge and the electron acceptor nitro group at the para position, D‐π‐A structured carbazole–formazan dye 6C showed the highest Stokes shift of 155 nm.     

Structural studies on new diphenyl formazans and their lanthanide(III) complexes

Summary Potentiometric, u.v., i.r., n.m.r. and t.g.a. studies have been carried out on 1,5-bis(o-carboxyphenyl)-3-acetyl-formazan and 1-(o-carboxyphenyl-5-(o-hydroxyphenyl)-3-acetylformazan and their complexes with trivalent lanthanide ions. The ionization constants of formazans and the formation constants of their complexes have been determined potentiometrically by the Bjerrum-Calvin method (Irving and Rossotti modification). Complexation has also been studied by a conductimetric titration method.