Ionically self-assembled terephthalylidene-bis-4-n-alkylanilines/n-decanesulfonic acid supramolecules: synthesis, mesomorphic behaviour and optical properties

This paper describes the preparation, mesomorphic and photophysical studies of a two type of calamitic molecules derived from azomethines, N,N'-(1,4-phenylenebis(methan-1-yl-1-ylidene)bis(4-pentylbenzenamine) (LCBAZ1) and N,N'-(1,4-phenylenebis(methan-1-yl-1-ylidene)bis(4-decylbenzenamine) (LCBAZ2) before and after protonation with the n-decyl sulfonic acid (DSA). The lengths of the outer spacers are four or nine methylene units connected with the imine group by phenyl ring in the para position. Liquid crystal properties of the undoped and doped azomethines are studied by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Wide-angle X-ray diffraction (WAXD) technique is used to probe the structural properties of the azomethines as well as its complexes. The lengths of the outer flexible spacers have an effect on the mesomorphic properties of the azomethines. The compound LCBAZ2 with nine methylene units exhibit smectic phases (Sm C and Sm X), while the LCBAZ1 with four methylene units exhibit nematic and smectic phases (N and Sm C). The effects of protonation on the phase transitions of the azomethines are investigated. The structure formation of (LCBAZx)(1)(DSA)(2) complexes are discussed on the basis of FTIR spectroscopy. Additionally, the azomethines before and after protonation with DSA are investigated by UV-vis and photoluminescence (PL) spectroscopy. With the exception of LCBAZ1 in its undoped state, the chloroform solution of the doped or undoped azomethines exhibit greenish fluorescence when the solutions are subjected to 400 nm excitation wavelength. It are concluded that the combination of the molecular and supramolecular engineering concepts stabilized the smectic phase.     

A novel class of Cd(II), Hg(II) turn-on and Cu(II), Zn(II) turn-off Schiff base fluorescent probes

N,N'-((5,5'-(quinoxaline-2,3-diyl)bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))bis(4-methoxyaniline) 4 and N,N'-((5,5'-(quinoxaline-2,3-diyl)-bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))dianiline 5 have been prepared and structurally characterized. The X-ray crystal structures of compounds 4 and 4a have been determined. These compounds displayed good sensitivity toward transition metal ions with Cd(II), Zn(II) turn-on and Cu(II), Hg(II) turn-off in fluorescence. It is an elegant example of on/off behavior like a lamp. When Cd(II) or Zn(II) is added into compounds 4 or 5, the lamp will switch on, and then when Cu(II) or Hg(II) is added into the mixture, the lamp will switch off. The binding properties of 4 and 5 for cations were examined by fluorescence spectroscopy. The fluorescence data and crystal structure indicate that a 1:1 stoichiometry complex is formed between compound 4 (or 5) and metal ions, and the binding affinity is very high. The recognition mechanism between compound 4 (or 5) and metal ion was discussed based on the their chemical constructions and the CHEF/CHEQ effect when they interacted with each other.     

对二氨基二苯型芳酰胺类液晶化合物的合成与表征

液晶作为新型材料,在高新技术领域显示出越来越广阔的应用前景,目前科学界对各种类型的液晶,包括主链型,侧链型液晶以及热固性液晶方面的研究非常活跃~([1-4]).含有端烯类双键的液晶化合物,可以通过双键联结到高分子链上,形成高分子液晶化合物,也可与其它烯类单体发生共聚合反应,制备液晶热固性树脂,还可以通过双键氧化,制备液晶环氧树脂,因此有广泛的应用前景~([5,6]).     

Physicochemical properties of the high-field MRI-relevant [Gd(DTTA-Me)(H2O)2]- complex

To study the physicochemical properties of the DTTA chelating moiety (H4DTTA = diethylenetriaminetetraacetic acid = N,N'-[iminobis(ethane-2,1-diyl)]bis[N-(carboxymethyl)glycine]), used in several compounds proposed as magnetic resonance imaging (MRI) contrast agents, the methylated derivative H4DTTA-Me (N,N'-[(methylimino)bis(ethane-2,1-diyl)]bis[N-(carboxymethyl)glycine]) was synthesized. Protonation constants of the ligand were determined in an aqueous solution by potentimetry and (1)H NMR pH titration and compared to various DTTA derivatives. Stability constants were measured for the chelates formed with Gd(3+) (log K(GdL) = 18.60 +/- 0.10) and Zn(2+) (log K(ZnL) = 17.69 +/- 0.10). A novel approach of determining the relative conditional stability constant of two paramagnetic complexes in a direct way by (1)H NMR relaxometry is presented and was used for the Gd(3+) complexes [Gd(DTTA-Me)(H2O)2](-) (L1) and [Gd(DTPA-BMA)(H2O)] (L2) [K(L1/L2)*(at pH 8.3, 25 degrees C) = 6.4 +/- 0.3]. The transmetalation reaction of the Gd(3+) complex with Zn(2+) in a phosphate buffer solution (pH 7.0) was measured to be twice as fast for [Gd(DTTA-Me)(H2O)2](-) in comparison to that for [Gd(DTPA-BMA)(H2O)]. This can be rationalized by the higher affinity of Zn(2+) toward DTTA-Me(4-) if compared to DTPA-BMA(3-). The formation of a ternary complex with L-lactate, which is common for DO3A-based heptadentate complexes, has not been observed for [Gd(DTTA-Me)(H2O)2](-) as monitored by (1)H NMR relaxometric titrations. From the results, it was concluded that the heptadentate DTTA-Me(4-) behaves similarly to the commercial octadentate DTPA-BMA(3-) with respect to stability. The use of [Gd(DTTA-Me)(H2O)2](-) as an MRI contrast agent in vitro and in animal studies is conceivable, mainly at high magnetic fields, where an increase of the inner-sphere-coordination water actually seems to be the most certain way to increase the relaxivity.     

双（呋喃甲醛）缩二胺钴（II）配合物的合成及其氧合和催化氧化性能研究

合成和表征了氯化双（呋喃甲醛）缩邻苯二胺合钴（II）（1）、氯化双（呋 喃甲醛）缩乙二胺合钴（II）（2）、氯化双（呋喃甲醛）缩1,2-丙二胺合钴（ II）（3）和氯化双（呋喃甲醛）缩1,3-丙二胺合钴（II）（4）。在吡啶溶液中 和不同温度下,测定了配合物的饱和吸氧量,求出了氧加合常数和热力学参数ΔH °,ΔS°。并以这些配合物为催化剂,活化分子氧氧化环已烯得到高选择性的烯 丙位氧化产物。讨论了温度、配体结构对配合物氧合性能的影响和配体结构以及添 加NHPI（N-羟基邻苯二甲酰亚胺）对环已烯氧化反应的影响。     

A NEW ACTIVE DIESTER FOR SELECTIVE POLYMERIZATION TO FORM FUNCTIONAL POLYAMIDES

A new synthetic route to polyamides and hydroxyl polyamides was established, based on the selecting (?)-acylation of three novel typical active diesters: the active diester of N-hydroxy- (?) 4-epoxy-5-cyclohexene-2, 3-dicarboximide( HOEC), such as N, N'-(temphthaloyldioxy) bis(1, 4- epoxy - 5 - cyclohexene- 2, 3 - dicarboximide.) ( PBOEC), N, N'- ( isophthaloyl - dioxy) bis (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide)(IPBOEC) and N, N' -(adipoyldioxy) his (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide) ( ADOEC)with aliphatic diamines and 1,3-diamino-2-hydroxypropane. The polycondensation occurs at room temperature in solution without added catalyst. Dipolar aprotic solvents which include dimethyl sulfoxide, N- methyl - 2- pyrrolidone and dimethylformamide were used as solvents for polymerization. The selective N-acylation of two active diesters was performed as a model reaction study.     

Synthesis and characterization of complexes of UO2(II) and Th(IV) of bis-schiff bases derived from furoylpyrazolone

Four new complexes of UO₂(II) and Th(IV) with bis-Schiff bases, derived from N,N'-bis[(l-phenyl-3-methyl-5-oxo-4-pyrazolinyl)-a-furylmethylidyne]-1,2-propylenediimine [1,2-BPMOPFP-H₂] and N,N'- bis[(l-phenyl-3-methyl-5-oxo-4-pyrazolinyl)-a-furylmethylidyne]-1,3-propylenediimine [1,3-BPMOPFP-H₂], were synthesized and characterized by elemental analysis, IR, UV, ¹HNMR spectroscopy, and molar conductivity. The general formula of the complexes was confirmed to be [UO₂(BPMOPFP)], [Th(BPMOPFP)(NO₃)]NO₃. A possible structure for the complexes have been proposed.     

Synthesis and Transformations of Ethyl (Z)-2-(2,3-dihydro-1,3-dioxo-1H-isoindol-2-yl)-3-(dimethylamino)propenoate

Ethyl (Z)-2-(2,3-dihydro-1,3-dioxo-1H-isoindol-2-yl)-3-(dimethylamino)propenoate was prepared in one step from ethyl (2,3-dihydro-1,3-dioxo-1H-isoindol-2-yl)acetate and bis(dimethylamino)-tert-butoxymethane and treated with various amines and hydrazines to afford the corresponding amino substituted products. Reactions of the titled compound with N,N'-, C,N-, and C,O'-ambident nucleophiles in refluxing acetic acid furnished the corresponding fused pyrimidinones, quinolizinones, and pyranones.     

Rational assembly of soluble copper(II) phosphonates: synthesis, structure and magnetism of molecular tetranuclear copper(II) phosphonates

The reactions of the dinuclear copper complexes [Cu(2)(L)(OAc)] [H(3)L = N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) or [Cu(2)(L')(OAc)] (H(3)L' = N,N'-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)] with various phosphonic acids, RPO(3)H(2) (R = t-Bu, Ph, c-C(5)H(9), c-C(6)H(11) or 2,4,6-i-Pr(3)-C(6)H(2)), leads to the replacement of the acetate bridge affording tetranuclear copper(II) phosphonates, [Cu(4)(L)(2)(t-BuPO(3))](CH(3)OH)(2)(C(6)H(6)) (1), [Cu(4)(L)(2)(PhPO(3))(H(2)O)(2)(NMe(2)CHO)](H(2)O)(2) (2), [Cu(4)(L')(2)(C(5)H(9)PO(3))](CH(3)OH)(2) (3), [Cu(4)(L')(2)(C(6)H(11)PO(3)](MeOH)(4)(H(2)O)(2) (4) and [Cu(4)(L')(2)(C(30)H(46)P(2)O(5))](PhCH(3)) (5). The molecular structures of 1-4 reveal that a [RPO(3)](2-) ligand is involved in holding the four copper atoms together by a 4.211 coordination mode. In 5, an in situ formed [(RPO(2))(2)O](4-) ligand bridges two pairs of the dinuclear subunits. Magnetic studies on these complexes reveal that the phosphonate ligand is an effective conduit for magnetic interaction among the four copper centers present; a predominantly antiferromagnetic interaction is observed at low temperatures.     

Chiral cyanide-bridged Cr(III)-Mn(III) heterobimetallic chains based on [(Tp)Cr(CN)3]-: synthesis, structures, and magnetic properties

By the reactions of Mn(III) Schiff-base complexes with the tricyanometalate building block, [(Tp)Cr(CN)(3)](-) (Tp = Tris(pyrazolyl) hydroborate), two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes, [Mn((R,R)-Salcy)Cr(Tp)(CN)(3)·1/4H(2)O·1/2CH(2)Cl(2)](n) (1) and [Mn((S,S)-Salcy)Cr(Tp)(CN)(3)·1/4H(2)O·1/2CH(2)Cl(2)](n) (2) (Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [Mn((R,R)-Salphen)Cr(Tp)(CN)(3)](n) (3) and [Mn((S,S)-Salphen)Cr(Tp)(CN)(3)](n) (4) (Salphen = N,N'-1,2-diphenylethylene-bis(salicylideneiminato) dianion), have been successfully synthesized. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes. Structural analyses reveal the formation of neutral cyano-bridged zigzag single chains in 1 and 2, and neutral cyano-bridged zigzag double chains in 3 and 4. Magnetic studies show that antiferromagnetic couplings are operative between Cr(III) and Mn(III) centers bridged by cyanide. Complexes 1 and 2 are the rare examples of chiral ferrimagnets; while complexes 3 and 4 exhibit a coexistence of chirality and spin-glass behavior in a 1D chain.     

Planar-chiral metal complexes comprised of square-planar metal and achiral tetradentate ligands: design, optical resolution, and thermodynamics

Planar-chiral palladium complexes {[[N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamidato)](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(4)) and [[2,2'-[1,4-butanediylbis[[(oxy-7,1-naphthalenediyl)imino]methyl]]dipyrrolato](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(5))} were synthesized from achiral tetradentate ligands N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamide) (H(2)L(4)) and N,N'-bis[(1H-pyrrol-2-yl)methylidene]-7,7'-(1,4-butanediyldioxy)bis(1-naphthalenamine) (H(2)L(5)) bearing two dissymmetric bidentate units at both ends and a Pd(II) ion, respectively. The palladium complexes were crystallized in the monoclinic space group P2(1)/n with the unit cell parameters a = 16.5464(6) ?, b = 11.3534(4) ?, c = 17.6697(7) ?, β = 115.5300(10)°, and Z = 4 for PdL(4) and a = 17.2271(8) ?, b = 10.1016(5) ?, c = 17.9361(9) ?, β = 105.6310(10)°, and Z = 4 for PdL(5). The planar-chiral structures of PdL(4) and PdL(5) were confirmed by single-crystal X-ray analyses, resulting in the fact that the crystals were racemic mixtures. The racemic mixtures were successfully resolved by using chiral high-performance liquid-chromatography techniques. Racemizations of the complexes were found to be drastically dependent on the arrangement of the charged or uncharged metal-binding N atoms of the ligands.     

Thermal behaviour and electrochemical properties of bis(trifluoromethanesulfonyl)amide and dodecatungstosilicate viologen dimers

We report the synthesis and characterization of dimeric viologen salts (1',1'-(alkane-1,n-diyl)bis(1-ethyl-4,4'-bipyridinium) with n = 4-10) with bis(trifluoromethanesulfonyl)amide (bistriflimide, Tf(2)N(-)) as a counteranion. For n = 4, 5 and 6, and for the nonylviologen cation (1,1'-dinonyl-4,4'-bipyridinium) we also prepared salts with the totally inorganic dodecatungstosilicate anion, SiW(12)O(40)(4-), featuring a poly-charged surface and nanosized dimensions. The materials have been characterized by means of calorimetric techniques, X-ray diffraction and solid state NMR and a comparison is made with analogous monomeric viologen salts exhibiting smectic mesophases. A strong odd-even effect is observed in the melting points and in the thermal behaviour of the bistriflimide dimeric systems, similar to what was reported for dipolar calamitic liquid crystal dimers, although the studied viologen dimers are not mesomorphic. By increasing the size of the counteranion we have observed a destabilization of the crystal phases and of the mesophases in favour of a glassy amorphous state. Implications on the design of novel ionic liquid crystals are discussed. The electrochemical behaviour in solution has been investigated by cyclic voltammetry measurements: interestingly, the odd-even effect is clearly visible also in the redox potentials. The spin-pairing of the viologen radical cations formed at each end of the dimer is responsible for the observed redox trend. Insights on the structure of the spin-paired dimer have been obtained by DFT calculations.     

Transition metal induced derivatisations resulting in novel coordination behaviour of bis(oxamato) ligands

Two mononuclear bis(oxamato) complexes with the formula [nBu4N]2[M(2,3-acbo)] (M=Ni (), Cu (), with acbo=anthra-9,10-chinone-2,3-bis(oxamato) have been synthesized starting from symmetric diethyl N,N'-anthra-9,10-chinone-2,3-bis(oxamate) (, 2,3-acboH2Et2). The crystal structures of and have been determined, verifying that the transition metal ions are eta4(kappa2N,kappa2O) coordinated by the [2,3-acbo]4- ligands. Using the asymmetric diethyl N,N'-anthra-9,10-chinone-1,2-bis(oxamate) (, 1,2-acboH2Et2) leads, under otherwise identical reaction conditions, to the novel bis(oxamato) complex [(n)Bu4N]2[Ni(1,2-acbo)] () whereby in the case of Cu(II) the derivate [nBu4N]2[Cu(aibo)2] () (aibo=anthra[1,2-d]-(imidazole-2-carboxylato)-6,11-dione) has been obtained. The crystal structures of and have been determined, displaying that the Ni(II) ion of is eta4(kappa2N,kappa2O) coordinated by the [1,2-acbo]4- ligand. The Cu(II) ion of is coordinated by two [aibo]2- ligands, giving rise to an approximately square-planar trans-bis(aibo-N,O) arrangement. Using the symmetric diethyl N,N'-4,5-dinitro-o-phenylene-bis(oxamate) (, niboH2Et2), possessing strongly electron withdrawing NO2-groups, leads under otherwise identical reaction conditions to the bis(oxamato) complex [nBu4N]2[Ni(nibo)] (), whereby in the case of Cu(II) the derivate [nBu4N]2[Cu(niqo)2] () (niqo=7,8-dinitro-2,3-quinoxalinedionato) has been obtained. The crystal structures of and have been determined, ensuring that the Ni(II) ion of is eta(4)(kappa2N,kappa2O) coordinated by the [nibo]4- ligand. The Cu(II) ion of is coordinated by four oxygen atoms of two [niqo]2- ligands, giving rise to an approximately square-planar coordination geometry.     

N,N′-二(芳磺酰)亚磺酰胺-S-(2-苯并咪唑基)类化合物的合成

本文报道了新化合物N,N＇—二(芳磺酰)亚磺酰胺—S—(2—苯并咪唑基)钠(a～e)以及N,N＇—二(芳磺酰)亚磺酰胺—S—(2—苯并咪唑基)(f～i)的合成。通过在感光乳剂中的应用,我们发现a,b和c具有超增感作用,它们分别使卤化银乳剂的感光度提高62％,22％和45％。 钠—N—氯芳磺酰亚胺化合物既是一类精细化工产品,又是一类重要的反应中间体。由它们     

Synthesis, molecular structure, spectroscopic studies and second-order nonlinear optical behaviour of N,N'-(2-hydroxy-propane-1,3-diyl)-bis(5-nitrosalicylaldiminato-N,O)-copper(II)

N,N'-(2-Hydroxy-propane-1,3-diyl)-bis(5-nitrosalicylaldiminato-N,O)-copper(II) has been synthesized. The crystal structure has been determined by X-ray diffraction analysis, and linear optical characterization has been determined by UV-vis spectroscopy. It was found that the molecule under investigation has solvatochromic behaviour in the UV region, implying non-zero microscopic first hyperpolarizability. To reveal the microscopic nonlinear optical (NLO) properties, the static first hyperpolarizabilities (beta) and the electric dipole moments (mu) were evaluated by using the ab initio finite field (FF) method. According to the results of the FF calculations, the synthesized compound exhibits non-zero beta values, and it might have microscopic NLO behaviour.     

Magnetostructural studies on ferromagnetically coupled copper(II) cubanes of Schiff-base ligands

Three cubane copper(II) clusters, namely [Cu(4)(HL')4] (1), [Cu4L2(OH)2] (2), and [Cu4L2(OMe)2] (3), of two pentadentate Schiff-base ligands N,N'-(2-hydroxypropane-1,3-diyl)bis(acetylacetoneimine) (H3L') and N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) (H3L), are prepared, structurally characterized by X-ray crystallography, and their variable-temperature magnetic properties studied. Complex 1 has a metal-to-ligand stoichiometry of 1:1 and it crystallizes in the cubic space group P43n with a structure that consists of a tetranuclear core with metal centers linked by a mu(3)-alkoxo oxygen atom to form a cubic arrangement of the metal and oxygen atoms. Each ligand displays a tridentate binding mode which means that a total of eight pendant binding sites remain per cubane molecule. Complexes [Cu4L2(OH)2] (2) and [Cu4L2(OMe)2] (3) crystallize in the orthorhombic space group Pccn and have a cubane structure that is formed by the self-assembly of two {Cu2L}+ units. The variable-temperature magnetic susceptibility data in the range 300-18 K show ferromagnetic exchange interactions in the complexes. Along with the ferromagnetic exchange pathway, there is also a weak antiferromagnetic exchange between the copper centers. The theoretical fitting of the magnetic data gives the following parameters: J1 = 38.5 and J2 = -18 cm(-1) for 1 with a triplet (S = 1) ground state and quintet (S = 2) lowest excited state; J1 = 14.7 and J2 = -18.4 cm(-1) for 2 with a triplet ground state and singlet (S = 0) lowest excited state; and J1 = 33.3 and J2 = -15.6 cm(-1) for 3 with a triplet ground state and quintet lowest excited state, where J1 and J2 are two different exchange pathways in the cubane {Cu4O4} core. The crystal structures of 2 * 6 H2O and 3 * 2 H2O * THF show the presence of channels containing the lattice solvent molecules.     

双[N,N'-亚烃基-2,2'-(芳亚甲基)二(3,4-二甲基吡咯-5-醛缩亚胺)]合双锰(Ⅱ)的合成、光谱特征及拟酶催化性能研究

首次报道了新型Schif碱类配体双[N,N-亚烃基-2,2-(苯亚甲基)二(3,4-二甲基吡咯-5-醛缩亚胺)]和双[N,N-(1,2-亚乙基)-2,2-(4-甲氧基苯亚甲基)二(3,4-二甲基吡咯-5-醛缩亚胺)]及其双锰配合物的合成方法、光谱特征及用配合物催化PhIO单加氧化环己烷反应的研究。     

57Fe Mössbauer spectroscopy predicts superstructure for K0.08[Cu(II)(N,N'app)Cl]2[Fe(III)(CN)6].0.92H3O.3H2O

The compound [Cu(N,N'app)Cl](2)[Fe(CN)(6)].xH(2)O, with N,N'app being bis(N,N'-3-aminopropylpiperazine), was prepared and its structure determined by single crystal X-ray analysis, confirming a ratio of two copper complexes to one iron complex; (57)Fe M?ssbauer spectra showed three quadrupole doublets typical of iron(iii) low spin species which call for the presence of a superstructure.     

Thermotropic poly(azomethine-urethane)s with non linear optical properties: Synthesis and characterization

Two series of the thermotropic main chain poly(azomethine-urethane)s were synthesized by the polyaddition of azadiol, 1,8-octandiol with methylene bis(phenyl isocyanate) (MDI) and tolylene 2,4-diisocyanate (TDI) respectively. The mesomorphic properties and phase transition temperature of the polymers were characterized by differential scanning calorimetry and hot stage polarizing microscopy. These polymers showed nematic messophase. The non linear optical (NLO) activity of the polymers was also investigated.     

OPTICALLY ACTIVE AND FLAME-RETARDANT POLY(AMIDE-IMIDE)S BASED ON PHOSPHINE OXIDE MOIETY AND N,N′-(PYROMELLITOYL)BIS-L-AMINO ACID IN THE MAIN CHAIN:SYNTHESIS AND CHARACTERIZATION

<正>Six new optically active and flame-retardant poly(amide-imide)s PAIs 5a-5f containing phosphine oxide moiety as a flame-retardant unit in the main chain were synthesized from direct polycondensation reaction of six chiral N,N′-(pyromellitoyl)-bis-L-amino acid 3a-3f with bis(3-aminophenyl)phenyl phosphine oxide 4 in a medium consisting of N-methyl-2-pyrrolidone(NMP),triphenyl phosphite(TPP),calcium chloride(CaCl_2) and pyridine.The polymerization reactions produced a series of optically active poly(amide-imide)s with good yield and good inherent viscosity of 0.34-0.70 dLg~(-1).The resulted polymers were fully characterized by means of FTIR and ~1H-NMR spectroscopy,gel permeation chromatography(GPC),elemental analyses,inherent viscosity and solubility tests.Thermal properties and flame-retardant behavior of the PAIs 5a-5f were investigated using thermal gravimetric analysis(TGA and DTG) and limiting oxygen index(LOI).Data obtained by thermal analysis(TGA and DTG) revealed that these polymers showed good thermal stability.Furthermore,high char yield in TGA and good LOI values indicated that the resulting polymers were capable of exhibiting good flame retardant properties.N,N′-(pyromellitoyl)-bis-L-amino acids 3a-3f were prepared in quantitative yields by the condensation reaction of pyromellitic dianhydride(1,2,4,5-benzenetetracarboxylicacid-1,2,4,5-dianhydride) 1 with L-alanine 2a,L-valine 2b,L-leucine 2c,L-isoleucine 2d,L-phenyl alanine 2e and L-2-aminobutyric acid 2f in acetic acid solution.