Ruthenium(II) complexes containing bidentate Schiff bases and triphenylphosphine or triphenylarsine

Reactions of ruthenium(II) complexes [RuHX(CO)(EPh₃)₂(B)] (X = H or Cl; B = EPh₃, pyridine (py) or piperidine (pip); E = P or As) with bidentate Schiff base ligands derived by condensingo- hydroxyacetophenone with aniline,o- orp-methylaniline have been carried out. The products were characterized by analytical, IR, electronic and¹H-NMR spectral studies and are formulated as [Ru(X)(CO) (L)(EPh₃)(B)] (L = Schiff base anion; X = H or Cl; B = EPh₃, py or pip; E = P or As). An octahedral structure has been tentatively proposed for the new complexes. The new complexes were tested for their catalytic activities in the oxidation of benzyl alcohol to benzaldehyde.     

Synthesis and photophysics properties of novel bipolar copolymers containing quinoline aluminum moieties and carbazole segments

A novel polymerizable 8-hydroxyquinoline aluminum (Alq₃) complex monomer and its copolymers (Alq₃/N-vinylcarbazole (NVK)) with different mole fractions of Alq₃ in feed were designed and synthesized. The structure of the Alq₃-complex monomer was characterized by ¹H NMR, FT-IR and elemental analysis, and the bipolar copolymers with various desired Alq₃ loading were characterized by ¹H NMR, FT-IR, elemental analysis, and gel permeation chromatography (GPC). The results indicate that these copolymers have moderate molecular weight as well as good solubility in common organic solvent. Thermal properties measurement and analysis show that these copolymers possess excellent thermal stability and high glass transition temperature (T_g). The photophysics properties of the copolymers were studied by UV–vis and fluorescence spectra. Nearly monochromatic yellow–green emission from Alq₃ was observed in high concentration solution and solid state, showing effective energy transfer characteristic. The results demonstrate that introduction of carbazole as hole-transporting and energy transfer group is a potential method to improve the luminescent performance of the Alq₃-based polymers.     

Synthesis and characterization of novel Schiff bases containing pyrimidine unit

The work involves synthesis of novel Schiff base derivatives containing a pyrimidine unit starting with chalcones. 4-Aminoacetophenone was reacted with 4-nitrobenzaldehyde or 4-chlorobenzaldehyde in basic medium giving chalcones, [I]_a and [I]_b, respectively, by Claisen-Schemidt reaction. The chalcones [I]_a and [I]_b were reacted with urea in HCl medium giving oxopyrimidines, [II]_a and [II]_b. They were also reacted with thiourea in basic medium to give thioxopyrimidines, [III]_a and [III]_b. The novel mono and bis Schiff bases, [VIII]_na, [VIII]_nb, [IX]_na, [IX]_nb, [X]_na, [X]_nb, [XI]_na, and [XI]_nb were synthesized by the reaction of pyrimidine derivatives; oxopyrimdines, [II]_a and [II]_b and thioxopyrimidines, [III]_a and [III]_b with 4-(4′-n-alkoxybenzoloxy)benzaldehyde [VI] and polymethylene-α,ω-bis-4-oxybenzaldehydes [VII]_m, respectively, in dry benzene using drops of glacial acetic acid as a catalyst. The synthesized compounds were characterized by melting points, elemental analysis, FTIR, and ¹H NMR spectroscopy.     

萘环荧光离子液体合成、表征及光谱性能研究

以1-氯甲基萘和N-烷基咪唑为原料,四氢呋喃为溶剂,合成了5个具有荧光的新型离子液体.采用红外光谱(FT-IR)、核磁共振氢谱(1H NMR)、碳谱(13C NMR)等测试技术对产物进行了结构表征.并对其紫外光谱、荧光光谱等光谱性质进行了初步的研究.实验结果表明咪唑离子液体1,2二甲基-4-甲基萘咪唑氯化盐较咪唑离离子...     

Chemistry and applications of organotin(IV) complexes of Schiff bases

Schiff bases are the most widely used versatile ligands, able to coordinate many elements and to stabilize them in various oxidation states. Recently, this class of compounds has been employed as models for biological systems, and in control of stereochemistry in six-coordinate transition metal complexes. Recently, the chemistry of organotin(IV) complexes of Schiff bases has also stemmed from their antitumour, antimicrobial, antinematicidal, anti-insecticidal and anti-inflammatory activities. Furthermore, organotin(IV) complexes of Schiff bases present a wide variety of interesting structural possibilities. Both aliphatic and aromatic Schiff bases in their neutral and deprotonated forms have been used to yield adducts and chelates with variable stoichiometry and different modes of coordination. This critical review (>155 references) focuses upon the chemistry and biological applications of organotin(IV) complexes of Schiff bases reported in the past 15 years. Thermal behavior of these complexes is also discussed.     

Synthesis and structures of three isoxazole‐containing Schiff bases

The synthesis and structures of three isoxazole‐containing Schiff bases are reported, namely, (E)‐2‐{[(isoxazol‐3‐yl)imino]methyl}phenol, C₁₀H₈N₂O₂, (E)‐2‐{[(5‐methylisoxazol‐3‐yl)imino]methyl}phenol, C₁₁H₁₀N₂O₂, and (E)‐2,4‐di‐tert‐butyl‐6‐{[(isoxazol‐3‐yl)imino]methyl}phenol, C₁₈H₂₄N₂O₂. All three structures contain an intramolecular O—H…N hydrogen bond, alongside weaker intermolecular C—H…N and C—H…O contacts. The C—O(H) and imine C=N bond lengths were consistent with structures existing in the enol rather than the keto form. Despite having dihedral angles <25°, none of the compounds were observed to be strongly thermochromic, unlike their anil counterparts; however, all three compounds showed a visible colour change upon irradiation with UV light.     

Influence of Schiff base and lanthanide metals on the synthesis, stability, and reactivity of monoamido lanthanide complexes bearing two Schiff bases

The monoamido lanthanide complexes stabilized by Schiff base ligand L(2)LnN(TMS)(2) (L = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-8-C(9)H(6)N, Ln = Yb (1), Y (2), Eu (3), Nd (4), and La (5)) were synthesized in good yields by the reactions of Ln[N(TMS)(2)](3) with 1.8 equiv of HL in hexane at room temperature. It was found that the stability of 1-5 depends greatly on the size of the lanthanide metals with the increasing trend of Yb ≈ Y < Nd < La. The amine elimination of Ln[N(TMS)(2)](3) with the bulky bidentate Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Pr(i)(2)-C(6)H(3)) afforded the monoamido lanthanide complexes L'(2)LnN(TMS)(2) (Ln = Yb (9), Y (10), Nd (11), and La (12)). While the amine elimination with the less bulky Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Me(2)-C(6)H(3)) yielded the desired monoamido complexes with the small metals of Y and Yb, L'(2)LnN(TMS)(2) (Ln = Yb (13) and Y (14)), and the more stable tris-Schiff base complexes with the large metals of La and Nd, yielded L'(3)Ln as the only product. Complexes 1-14 were fully characterized including X-ray crystal structural analysis. Complexes 1-5, 10, and 14 can serve as the efficient catalysts for addition of amines to carbodiimides, and the catalytic activity is greatly affected by the lanthanide metals with the active sequence of Yb < Y < Eu ≈ Nd ≈ La.     

Structures,luminescence, and antibacterial studies of two transition metal complexes involving Schiff bases

Two new transition metal complexes of Schiff bases, [Pd₂(L1)₂Cl₂] (1) and [Zn(L2)₂] (2), [L1?=?N-(4-fluorobenzylidene)-2,6-diisopropylbenzenamine and L2?=?2,4-dibromo-6-((E)(mesitylimino)methyl)phenol], have been synthesized solvothermally and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV-vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a μ-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas 2 is mononuclear with the Zn^II tetrahedrally coordinated by two L2. Both 1 and 2 display photoluminescence in the solid state at 298?K (fluorescence lifetimes τ?=?22.516?ns at 468?nm for 1, τ?=?3.697?μs at 490?nm for 2). These Schiff bases and their metal compounds have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of penicillin.     

两种溴代水杨醛基单双Schiff碱衍生物的合成及变色发光性能研究

以3,5-二溴-2-羟基苯甲醛和1,2-二氨基乙烷、3-氨基苯甲酸为原料,合成了两种化合物N,N'-双3,5-二溴-2-羟基苯甲醛缩1,2-二氨基乙烷(DBSE)和N-3,5-二溴-2-羟基苯甲醛缩3-氨基苯甲酸(DBSA)。利用核磁共振氢谱、质谱、红外光谱和元素分析对目标化合物的结构进行了表征,通过紫外-可见吸收光谱、荧光光谱测定了其发光性能,另外通过TG-DTG测定了其热稳定性能。结果表明:目标化合物DBSE为蓝绿光发射,DBSA为紫色光发射;目标化合物的热分解温度均达260℃以上,具有良好的热稳定性;在254 nm紫外光照射不同时间下、不同的温度下、不同的极性溶剂中、不同浓度的Co2+离子滴定的情况中,目标化合物均表现出了一定的变色发光性能,整体来看DBSE的光致变色性能优于DBSA,而热致变色性能DBSA优于DBSE。     

Synthesis and crystal structures of two structurally related kryptoracemates

Kryptoracemates are racemic compounds (pairs of enantiomers) that crystallize in Sohnke space groups (space groups that contain neither inversion centres nor mirror or glide planes nor rotoinversion axes). Thus, the two symmetry‐independent molecules cannot be transformed into one another by any symmetry element present in the crystal structure. Usually, the conformation of the two enantiomers is rather similar if not identical. Sometimes, the two enantiomers are related by a pseudosymmetry element, which is often a pseudocentre of inversion, because inversion symmetry is thought to be favourable for crystal packing. We obtained crystals of two kryptoracemates of two very similar compounds differing in just one residue, namely rac‐N‐[(1S ,2R ,3S )‐2‐methyl‐3‐(5‐methylfuran‐2‐yl)‐1‐phenyl‐3‐(pivalamido)propyl]benzamide, C₂₇H₃₂N₂O₃, (I), and rac‐N‐[(1S ,2S ,3R )‐2‐methyl‐3‐(5‐methylfuran‐2‐yl)‐1‐phenyl‐3‐(propionamido)propyl]benzamide dichloromethane hemisolvate, C₂₅H₂₈N₂O₃·0.5CH₂Cl₂, (II). The crystals of both compounds contain both enantiomers of these chiral molecules. However, since the space groups [P 2₁2₁2₁ for (I) and P 1 for (II)] contain neither inversion centres nor mirror or glide planes nor rotoinversion axes, there are both enantiomers in the asymmetric unit, which is a rather uncommon phenomenon. In addition, it is remarkable that (II) contains two pairs of enantiomers in the asymmetric unit. In the crystal, molecules are connected by intermolecular N—H…O hydrogen bonds to form chains or layered structures.     

Geometry and mesomorphic properties of new schiff bases containing thiazole ring

New liquid-crystalline azomethines — 2-(4-alkoxybenzylideneamino)-4-(3-nitrophenylamino)thiazoles —displaying nematic mesomorphism at 42–137°C have been synthesized. The structure of these compounds was studied by the MNDO LCAO MO method. A correlation was found between the geometric parameters and liquid crystal properties.Bashkir State University, 450074 Ufa, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1242–1248, September, 1999.     

Highly effective quenching of the ultrafast radiationless decay of photoexcited pyrimidine bases by covalent modification: photophysics of 5,6-trimethylenecytosine and 5,6-trimethyleneuracil

5,6-Trimethylenecytosine (TMC) and 5,6-trimethyleneuracil (TMU), in which the twist of the C5-C6 bond (or the pyrimidalization of C5) is strongly hindered, do not exhibit the subpicosecond excited-state lifetime characteristic of the naturally occurring pyrimidine bases. This result demonstrates the important role the out-of-plane deformation of the six-membered ring plays in the ultrafast (subpicosecond) internal conversion of photoexcited nucleobases. The dramatically shorter fluorescence lifetime of TMU ( approximately 30 ps) relative to TMC ( approximately 1.2 ns), in aqueous solution at room temperature, is attributed to the presence in TMU of an efficient, secondary nonradiative decay channel of S(1)(pipi*) involving a low-lying (1)npi* state.     

两种含硫Schiff碱及其配合物的合成与光谱性质

合成了2-氨基噻唑缩5-溴水杨醛(HBrsatz)和2-乙酰噻吩缩4-羟基苯甲酰腙(Hetphz)两种含硫Schiff碱及其配合物[Cu(Brsatz)2](Ⅰ)和[Cd(H2O)(Hetphz)(phen)](NO3)2(Ⅱ),通过元素分析、红外光谱和紫外光谱对它们的结构进行了表征,并研究了它们在DMF溶液中的发光性质,结果表明HBrsatz和Hetphz及配合物Ⅱ具有较强的荧光发射.     

Thermal stability of structurally related polymers containing carborane and phthalocyanine groups

These studies were undertaken to determine the thermal behavior of structurally related polymers having a carborane nucleus in the recurring unit. Three of these products also contained phthalocyanine rings in their molecules. Results of thermal analysis studies show generally that the relative heat stability of the polymers conforms closely with indications given by similar investigations of structurally related intermediate and model compounds. A polymer with dimethylsiloxane units exhibited more resistance to thermal decomposition than similar products having urethane groups in their molecules. The urethane polymers derived from tolylene diisocyanate were found to be somewhat less heat-stable than analogous materials synthesized from methylenebis-(p-phenyl isocyanate). The relative order of thermal resistance of these materials follows that of more conventional polyurethane elastomers.     

Synthesis and spectroscopic characterization of new Schiff bases containing the benzo-15-crown-5 moiety

New crown ether Schiff base derivatives were prepared by the condensation of 4'-formylbenzo-15-crown-5 or 4'-formyl-5'-hydroxybenzo-15-crown-5 with 1,2-bis(2-aminophenoxy)ethane. The structures of these new compounds were confirmed on the basis of elemental analysis, IR, (1)H- and (13)C-NMR, UV-Vis and mass spectroscopic data.     

Synthesis,photophysics, and photochemistry of peripherally Schiff base-zinc complex substituted zinc phthalocyanine

The content of this work is based on the introduction of the salicylhydrazone-zinc complexes into the phthalocyanine core. The reaction of the salicylhydrazone substituted ZnPc (1) with the related zinc(II) salt in basic conditions in DMF yielded bis[bis(salicyhydrazone)phenoxy)zinc(II)] phthalocyaninato zinc(II) (5) in which two salicylhydrazone-Zn complexes are linked through oxygen bridges to the macrocyclic core as three-nuclear complex. The novel compound synthesized in this study was fully characterized by general spectroscopic techniques such as FT-IR, UV-vis, ¹H NMR, ¹³C NMR, elemental analysis and mass spectroscopy. In addition, spectral, photophysical (fluorescence quantum yields), and photochemical (generation of singlet oxygen and photo stability under light irradiation) properties of newly synthesized phthalocyanine (5) and the starting Pcs molecules used to obtain this molecule were investigated in DMSO solutions, comparatively.     

Synthesis,characterization and biocidal studies of ruthenium(II) carbonyl complexes containing tetradentate Schiff bases

Stable ruthenium(II) complexes of Schiff bases have been prepared by reacting [RuHCl(CO)(PPh₃)₂(B)] (B = PPh₃, pyridine or piperidine) with bis(o-vanillin)ethylenediimine (valen), bis(o-vanillin)propylene-diimine (valpn), bis(o-vanillin)tetramethylenediimine (valtn), bis(o-vanillin)o-phenylenediimine (valphn), bis(salicylaldehyde)tetramethylenediimine (saltn) and bis(salicylaldehyde)o-phenylenediimine (salphn). These complexes have been characterised by elemental analyses, i.r., electronic, ¹H- and ³¹P{¹H}-n.m.r. spectral studies. In all the above reactions, the Schiff bases replace two molecules of Ph₃P, a hydride and a halide ion from the starting complexes, indicating that the Ru–N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru–P bond to Ph₃P. The new complexes of the general formula [Ru(CO)(B)(L)] (B = PPh₃, py or pip; L = tetradentate Schiff bases) have been assigned an octahedral structure. Some of the Schiff bases and the new complexes have been tested against the pathogenic fungus Fusarium sp.