Azomethine Linkages Research Articles

Novel Hydroxy- and Methyl-Terminated Triaromatic Schiff Base Compounds: Synthesis and Mesogenic Properties

A series of Schiff base hydroxy-mesogens and their model compounds have been synthesized. The mesogen is constructed from three-ring-containing mesogens linked through ester and azomethine groups with a terminal hydroxy group. The related model compounds were also synthesized with varying chain length with a terminal methyl group and their properties were compared with that of hydroxy mesogens. Extensive characterization of all mesogenic compounds was carried out by Fourier-transform IR, 1H and 13C NMR and mass spectroscopy. The phase characteristics such as nature of phase, melting and clearing temperatures and phase range were evaluated using a hot-stage optical polarizing microscope and differential scanning calorimetry. The appearance of enantiotropic smectic phases is due to the high molecular polarizability of the triaromatic core with azomethine and ester linkages.

(6E,7E)-N,N′-Bis(2-hydroxy-3-methoxybenzylidene)benzene-1,4-diamine

The title compound, C22H20N2, consists of two hypnone groups attached to a benzene ring via two azomethine linkages and crystallizes with an inversion centre at the mid-point of the central benzene ring. Mol­ecules are linked into a chain by C—H⋯N hydrogen bonds along the b-axis direction. Neighbouring chains are linked by C—H⋯π hydrogen bonds into sheets.

(E,E)-6,6′-Dimethoxy-2,2′-[o-phenylenebis(nitrilomethylidyne)]diphenol

The title compound, C22H20N2O4, consists of two o-vanillin groups connected to a benzene ring via two azomethine linkages. The mol­ecule structure is stabilized by inter­molecular C—H⋯O and C—H⋯N inter­actions.

Synthesis and characterization of mid‐ and end‐chain functional telechelics by controlled polymerization methods and coupling processes

AbstractWell‐defined polystyrene‐ (PSt) or poly(ε‐caprolactone) (PCL)‐based polymers containing mid‐ or end‐chain 2,5 or 3,5‐ dibromobenzene moieties were prepared by controlled polymerization methods, such as atom transfer radical polymerization (ATRP) or ring opening polymerization (ROP). 1,4‐Dibromo‐2‐(bromomethyl)benzene, 1,3‐dibromo‐5‐(bromomethyl)benzene, and 1,4‐dibromo‐2,5‐di(bromomethyl)benzene were used as initiators in ATRP of styrene (St) in conjunction with CuBr/2,2′‐bipyridine as catalyst. 2,5‐Dibromo‐1,4‐(dihydroxymethyl)benzene initiated the ROP of ε‐caprolactone (CL) in the presence of stannous octoate (Sn(Oct)2) catalyst. The reaction of these polymers with amino‐ or aldehyde‐functionalized monoboronic acids, in Suzuki‐type couplings, afforded the corresponding telechelics. Further functionalization with oxidable groups such as 2‐pyrrolyl or 1‐naphthyl was attained by condensation reactions of the amino or aldehyde groups with low molecular weight aldehydes or amines, respectively, with the formation of azomethine linkages. Preliminary attempts for the synthesis of fully conjugated poly(Schiff base) with polymeric segments as substituents, by oxidative polymerization of the macromonomers, are presented. All the starting, intermediate, or final polymers were structurally analyzed by spectral methods (1H NMR, 13C NMR, and IR). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 727–743, 2006

Novel Poly(Succinimide-Ether)s Based on the Reaction of Bismaleimides with Azomethine-Bisphenols

Novel poly(succinimide-ether)s containing azomethine linkages were synthesized by the addition polymerization reaction of bismaleimides, such as N, N′-4,4′-diphenylether bismaleimide and N, N′-4,4′-dibenzylbismaleimide, with various mesogenic azomethine-bisphenols such as: 4-(4-hydroxybenzylideneimino)phenol, 4,4′-oxy-bis(4-hydroxyben-zylideneimino)phenyl or 4,4′-bis(4-hydroxybenzylideneiminophenoxy)biphenyl. The structures of these polymers were identified by infrared and 1H-nuclear magnetic resonance spectroscopy. The polymers were characterized by solution viscometry, solubility and UV-VIS measurements. Their thermal properties were investigated using differential scanning calorimetry, thermogravimetric and thermo-optical analysis and hot-stage polarized light microscopy. The oligomers containing longer mesogenic moieties exhibited thermotropic liquid cristalline behavior.

Influence of fluoro substituents on the mesophase behaviour of banana-shaped molecules

Three new series of bent-shaped five-ring liquid crystals, based on the ester of isophthalic acid as the central core and azomethine linkages, are presented. They differ by the number and the position of halogeno substituents on the outer rings. This lateral substitution strongly influences the type of mesophases formed. Calculations were performed to determine the modification of the distribution of charge along the different molecules.

Synthesis, Characterization and Electrical Conductivity of Polyesters Containing Azomethine Linkages

The synthesis and characterization of some polyesters containing azomethine linkages are reported here. The electrical conductivity of these polyesters is measured and the results are explained with simple Pariser-Parr-Pople calculations. The polymers are doped with Ag and the electrical conductivity of most of the doped polymers is found to register significant increase. Attempts are made to explain this increase in electrical conductivity.

Synthesis and Characterization of Polyphosphonates having Azomethine Linkages

Two bishydroxy azomethine monomers were synthesized and reacted with dichloro-phenyl phosphine oxide by the interfacial polycondensation method using a phase transfer catalyst at 0°C. The polymers were characterized by IR, 1H-NMR, 31P-NMR, elemental analyses and X-ray diffraction study. These polymers are soluble in chlorinated aliphatic hydrocarbon solvents, such as CH2Cl2, CHCl3 as well as polar aprotic solvents such as DMF, DMAC, NMP, DMSO. Thermal and flammability studies were carried out by TGA, DTA and limiting oxygen index (LOI) measurements. The polymers are self-extinguishing and begin to lose weight at around 290°C in air.

New Vistas in Synthesis of Optically Active Polymers

A rational approach has been developed for unequivocally establishing asymmetric induction in the back bone of vinyl polymers based on 1,2-disubstituted and 1-substituted olefins. Towards this end, the principle of protecting group chemistry has been utilized to connect chiral auxiliaries to functional monomers in the form of boronate esters and azomethine linkages. This approach enables to remove the auxiliaries quantitatively after polymerization. For 1,2-disubstituted olefin based systems, the role of the type of chiral auxiliary used, nature of comonomers and the location of the chiral auxiliaries with respect to the polymerizable group on enantioselectivity has been elucidated. A divinyl functional monomer bearing chiral auxiliary in the form of azomethine protecting group has been synthesized from readily accessible precursors. This monomer was found to undergo asymmetric cyclopolymerization-tion. An overview of the results obtained from these investigations is presented.

Synthesis and characterization of polyurethanes containing azomethine linkages in the polymer backbone

Polyurethanes [OCONHPhCH=NPhNHCOOR] n (R = CH 2 CH(CH 3 ), (CH 2 ) m m = 2,4,6) aree prepared in good yields. They are amorphous or semicrystalline, soluble in aprotic polar solvents and insoluble in nonpolar solvents. Their inherent viscosity increases with m. The polymers start to decompose under air at 220-240°C.

Synthesis and characterization of polyimides and polyamide‐imides containing azomethine linkages

AbstractPolyimides and polyamide‐imides containing azomethine linkages in the polymer backbone have been synthesized from 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenylether (ODAI), 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenyl‐methane (MADI), 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenylsulphone (SDAI), pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and trimellitic anhydride (TMA), by a one‐step process. The diisocyanates ODAI, MDAI and SDAI were prepared from the corresponding diacids, namely, 4,4′‐bis(4‐carboxybenzylidene)‐diaminodiphenylether (ODAA), 4,4′‐bis(4‐carboxybenzylidene)‐diaminodiphenylmethane (MDAA) and 4,4′‐bis‐(4‐carboxybenzylidene)‐diaminodiphenylsulphone (SDAA) by a Weinstock‐modified Curtius rearrangement method. All the polycondensation reactions were conducted in N‐methyl‐2‐pyrrolidone (NMP) under identical conditions and the polymers obtained were characterized by IR spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry and X‐ray diffraction.

Epoxides bearing azomethine linkages

AbstractSeven structurally different diepoxides, triepoxides or tetraepoxides bearing azomethine linkages were synthesized and characterized. The reactions of 4‐hydroxybenzaldehyde or 3,4‐dihydroxybenzaldehyde with 4‐aminophenol or 4‐aminobenzoic acid afforded azomethines, which reacted subsequently with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide to yield diepoxides or triepoxides. Triepoxides were prepared by reacting 4‐hydroxybenzaldehyde with 5‐aminoisophthalic acid or 4‐amino‐2‐hydroxybenzoic acid again to yield azomethines, which were subsequently reacted with epichlorohydrin. In addition, a tetraepoxide was prepared from the reaction of 1,4‐benzenedicarbaldehyde with a double molar amount of 4‐amino‐2‐hydroxybenzoic acid to afford a bisazomethine followed by reaction with epichlorohydrin. The epoxy compounds were characterized by IR and 1H NMR spectroscopy. Their thermal polymerization in the presence of 4,4‐diaminodiphenylsulfone (DDS) was investigated by DTA. Thermal stabilities of cured resins were ascertained by TGA and isothermal gravimetric analysis (IGA) in N2 or air. The polymer derived from the tetraepoxide was the most heat‐resistant. It was stable in N2 up to 313°C and afforded an anaerobic char yield of 58% at 800°C.

Polycondensation versus metal template condensation of 2,2′‐ethylenedithiodianiline with glyoxal

AbstractA polymer with azomethine linkages is formed upon reaction of 2,2′‐ethylenedithiodianiline (1) with glyoxal. The same reaction in the presence of Ni(II) and Cu(II) ions yields the corresponding metal complexes of the macrocyclic ligand. The driving force for the selectivity of this reaction may be attributed to the template effect of the metal ions. In the case of Co(II) ions, the polymer is formed as a by‐product, together with the macrocyclic complex.

Self‐curing epoxy compounds

AbstractA new series including eight structurally different self‐curing epoxy compounds bearing azomethine linkages were synthesized, characterized and polymerized. 4‐(2,3‐Epoxypropoxy)‐benzaldehyde (EPB) or 2,3‐epoxypropyl glyoxylate monohydrate (EPG), prepared by reacting 4‐hydroxybenzaldehyde or glyoxylic acid monohydrate, respectively, with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide as catalyst, were used as starting materials. EPB or EPG reacted with an equimolar amount of a substituted aromatic amine (4‐aminobenzoic acid, 5‐aminoisophthalic acid, 4‐aminophenol, or 1,4‐phenylene‐diamine) to afford the epoxy compounds. They were characterized by IR and 1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. The thermal stabilities of cured resins were evaluated by dynamic TGA and isothermal gravimetric analysis (IGA). The polymers of the epoxy compounds derived from EPB were stable up to 225–298°C in N2 and afforded anaerobic char yield of 57–62% at 800°C.

Synthesis and characterization of new polyimides and polyamide-imides containing azomethine group in the polymer backbone

New aromatic polyimides and polyamide-imides containing azomethine linkages in the polymer backbone have been synthesized by reacting 4,4′-bis(isocyanato) benzylidene aniline (AZMI) with pyromellitic dianhydride (PMDA), 3,3′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and trimellitic anhydride (TMA) by one-step method. The AZMI was synthesized from 4,4′-bis(carboxy) benzylidene aniline (AZMA) by a Weinstock modified curtius rearrangement. All the polycondensation reactions were carried out in N-methyl-2-pyrrolidone (NMP) and the polymers obtained were characterized by infrared spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction.

ChemInform Abstract: Bicyclization of Unsaturated Hydrazones Mediated by Zirconocene Complexes. A New Anellation Strategy Based on the Reductive Cocyclization of Azomethine Linkages with Carbon‐Carbon Multiple Bonds.

AbstractThe zirconocene‐imine complex (III) derived from the imine (I) undergoes cocyclization with the alkynes (IV) to give the five‐membered cycles (V), which are transformed into the amides (VII).

New heat‐resistant polymers derived from azomethine bismaleimides and maleimide‐terminated azomethine prepolymers

AbstractA novel class of bismaleimides containing azomethine linkages was synthesized by reacting the monomaleamic acid derived from an aromatic diamine with terephthaldehyde (TPA) in a molar ratio 2 : 1 and subsequent cyclodehydration. In addition, a series of maleimide‐terminated azomethine prepolymers (MTAPs) was synthesized. More particularly, 4,4′‐diaminodiphenylsulfone (DDS) reacted with TPA in nonstoichiometric molar quantities (2 : 1 or 5 : 4 or 8 : 7) to prepare amine‐terminated azomethine prepolymers (ATAPs). The latter reacted with maleic anhydride and then cyclodehydrated. Furthermore, a maleimide‐crosslinkable azomethine prepolymer (MCAP) was synthesized by reacting tris(3‐aminophenyl)phosphine oxide with an equimolar amount of maleic anhydride and subsequently with TPA. The polymer precursors were characterized by IR, 1H‐NMR, DTA, and inherent viscosity. The thermal stability of the cured resins was evaluated by TGA and IGA. The thermal properties of the cured resins derived from the MTAPs were compared with those of the ordinary polyazomethine prepared from the reaction of DDS with TPA. It was shown that crosslinking of these polymer precursors during their curing was attained both via the maleimide and azomethine double bonds.

Synthesis, characterization and polymerization of new epoxy compounds containing azomethine linkages

AbstractNew epoxy compounds bearing azomethine linkages were synthesized and characterized. A series of epoxy derivatives of bis(azomethine)s (2a – d) was synthesized by reacting an aromatic diamine with 4‐hydroxybenzaldehyde in a 1:2 mole ratio to afford the corresponding bis(azomethine)s (1a – d), and subsequent reaction with excess 1‐chloro‐2,3‐epoxypropane in presence of a quarternary ammonium bromide as catalyst. In addition, epoxy compounds 4a, b and 5b were synthesized by reacting 1,4‐benzenedicarbaldehyde with 4‐aminophenol, 4‐aminobenzoic acid or 5‐aminoisophthalic acid in a 1:2 mole ratio and then with 1‐chloro‐2,3‐epoxypropane. The epoxy compounds were characterized by elemental analyses as well as by IR and 1H NMR spectroscopy. All epoxy compounds were thermally polymerized in the presence of 4,4′‐sulfonyl dianiline (6). The polymerization was investigated by DTA. The thermal stabilities of the resulting polymers were evaluated by dynamic TG and isothermal gravimetric analysis (IGA). The polymers derived from diepoxy compounds are stable in nitrogen up to 293–340°C and afford an anaerobic char yield of 43–62% at 800°C.

Bicyclization of unsaturated hydrazones mediated by zirconocene complexes. A new annulation strategy based on the reductive cocyclization of azomethine linkages with carbon-carbon multiple bonds

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBicyclization of unsaturated hydrazones mediated by zirconocene complexes. A new annulation strategy based on the reductive cocyclization of azomethine linkages with carbon-carbon multiple bondsMichael Jensen and Tom LivinghouseCite this: J. Am. Chem. Soc. 1989, 111, 12, 4495–4496Publication Date (Print):June 1, 1989Publication History Published online1 May 2002Published inissue 1 June 1989https://doi.org/10.1021/ja00194a053RIGHTS & PERMISSIONSArticle Views243Altmetric-Citations56LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (193 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Studies on phenoxo-bridged macrocyclic dicopper complexes. EPR spectral behaviour of mixed-valence systems [Cu(II)Cu(I)L] + and magnetic exchange interaction in complexes [Cu 2L](ClO 4) 2

EPR spectra of two series of electrochemically generated macrocyclic mixed-valence copper complex species [Cu(II)Cu(I)L] + have been investigated. Complexes belonging to series 1 [Cu 2L](ClO 4) 2 are derived from 6,12,18,24-substituted (H,H,H,H, ( a); Me,Me,Me,Me, ( b); Pr,Pr,Pr,Pr ( c); Ph,Ph,Ph,Ph ( d); H,H,Me,Me ( e)) macrocycle 7,11,19,23-dimetheno-9,21-dimethyl-1,5,13,17-tetra-azacyclotetracosa-5,7, 9,12,17,19,21,14-octaene-25,26-diol (H 2L). Complexes belonging to series 3, [Cu 2L](ClO 4) 2, are related to those of series 1 by replacement of two of the CHN linkages by CH 2NH groups of the segment containing two azomethine linkages having the 6,12-substituents H,H ( a); Me,Me ( b); Me,Ph ( c). In the mixed-valence species derived from 1b–1e and 3a–3c in MeCN or CH 2Cl 2 solutions the single unpaired electron is localized on one of the metal centres at room temperature on the EPR time scale. Only the species derived from 1a gives a seven-line EPR spectrum at room temperature indicating that the unpaired electron is delocalized over both metal centers. Variable temperature magnetic measurements on complexes 1b and 1c indicate strong antiferromagnetic exchange (−2 J = 835 ± 5 cm −1 and 806 ± 9 cm −1, respectively) in both cases.