Synthesis and characterization of novel liquidcrystalline polyurethanes

Novel polyurethanes have been synthesized by the condensation of two rigid diols, biphenyl-4,4'-diol (BPH(4,4')D) and 4-hydroxyphenyl-4-hydroxybenzoate (4HPH4'HB), with the flexible hexamethylene diisocyanate (HDI). Their phase diagrams were established by means of differential scanning calorimetry, nuclear magnetic resonance and polarizing optical microscopy. Poly(4HPH4'HB/HDI) was found to display a nematic phase between 140 and 199°C; poly (BPH(4,4')D/HDI) also exhibits a mesomorphic phase, but so far the nature of this phase has not been established.     

3,6-二叠氮基-1,2,4,5-四嗪的合成及理论研究

以3,6-双(3,5-二甲基吡唑基)-1,2,4,5-四嗪为原料, 经过肼解反应和重氮化反应, 制得了3,6-二叠氮基-1,2,4,5-四嗪(DAT). 在DFT-B3LYP/6-31G*水平下求得了DAT的分子几何、IR光谱和热力学性质. 计算模拟IR光谱和实测IR光谱的对比表明DAT在固态下不发生叠氮-四唑互变异构反应. 根据IR光谱计算了DAT的热容、焓、熵等热力学参数, 也给出了这些参数和温度T之间的函数关系. 在不破坏四嗪环和叠氮基的原则下通过构建等键反应求得了DAT的精确生成热为1088 kJ•mol^—1. 爆轰性能计算表明DAT爆速D＝8.45 km•s^－1, 爆压P＝31.3 GPa, 高于TNT和HMX.     

Oxidations of 3,6-diamino-1,2,4,5-tetrazine and 3,6-bis(s,s-dimethylsulfilimino)-1,2,4,5-tetrazine

Oxidation of 3,6-diamino-1,2,4,5-tetrazine ( 1 ) with most peracids gave 3,6-diamino-1,2,4,5-tetrazine 1,4-dioxide ( 3 ) as the major product; however, treatment of 1 with peroxytrifluoroacetic acid (PTFA) gave 3,6-diamino-1,2,4,5-tetrazine 1-oxide ( 4 ) as the major product along with a small amount of 3-amino-6-nitro-1,2,4,5-tetrazine 2,4-dioxide ( 5 ). Oxidation of 3,6-bis(S,S-dimethylsulfilimino)-1,2,4,5-tetrazine ( 6 ) with 3-chloroperoxybenzoic acid (MCPBA) gave 3-S,S-(dimethylsulfilimino)-6-nitroso-1,2,4,5-tetrazine ( 7 ), which was oxidized further with dimethyldioxirane to 3-(S,S-dimethylsulfoximino)-6-nitro-1,2,4,5-tetrazine ( 8 ). All attempts to obtain 3,6-dinitro-1,2,4,5-tetrazine ( 2 ) by further oxidation of 7 or 8 failed.     

Synthesis and characterization of novel biodegradable folate conjugated polyurethanes

In order to obtain targeting polyurethane micelle drug carriers, a series of biodegradable folate conjugated polyurethanes (FPUs) were synthesized using poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) as soft segments, L-lysine ethyl ester diisocyanate (LDI) and 1,3-propanediol (PDO) as hard segments, and folic acid-ethylenediamine conjugate (FA-EDA) as an end-capping reagent. The resultant FPUs were fully characterized by (1)H NMR, Fourier-transform infrared (FTIR) spectroscopy, ultraviolet spectrophotometry (UV), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). These polymers can self-assemble into micelles in aqueous solutions confirmed by dynamic light scattering (DLS), pyrene fluorescence probe techniques, and transmission electron microscopy (TEM). The results indicated that the bulk structures and micellar properties of the prepared polyurethanes could be controlled by varying the PEG content in the soft segments. The present work provides a facile approach to prepare amphiphilic multiblock copolymers with tumor targeting moiety, which is a good candidate as biodegradable carriers for active intracellular drug delivery.     

Synthesis, characterization and quantum chemistry study of 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine

3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)- 1,2,4,5-tetrazine (BTATz) was synthesized by the condensation of triaminoguanidinium nitrate with 2,4-pentanedione, followed by oxidation and substitution reaction. The product was characterized by elemental analysis, IR, NMR spectrometry and DSC analysis. Instead of nitrogen dioxide/N-methylpyrrolidone, acetic acid/sodium nitrite was used as the oxidizer during the oxidation. Thus, the cost was reduced and the process was simplified. The theoretical properties of BTATz were estimated by a B3LYP method based on a 6-31G(d,p) basis set, and the stable geometric configuration and bond order were obtained. The vibrational frequencies, IR spectrum and thermodynamic properties under different temperatures were obtained from vibrational analysis and the relationship between temperature and thermodynamics properties was deduced. Pyrolysis mechanism of BTATz was discussedand the transition state and activation energy of ring opening reaction of the tetrazole were deduced. __________ Translated from Chinese Journal of Organic Chemistry, 2008, 28(3) (in Chinese)     

3,3’-偶氮双(6-氨基-1,2,4,5-四嗪)新法合成、表征与量子化学研究

自行设计了3,3’-偶氮双(6-氨基-1,2,4,5-四嗪)(DAAT)新合成路线、采用3,5-双(3,5-二甲基吡唑-1-基)-1,2,4,5-四嗪(BDT)为原料, 由文献报道的4步反应缩减为2步, 经高压氨解、高锰酸钾氧化合成了DAAT, 总收率大幅提高, 达到58.1%, 并采用元素分析、红外光谱、核磁共振光谱等进行了结构表征. 为了从分子水平探索DAAT的性能, 采用B3LYP法, 在6-31G(d,p)基组水平上对DAAT的结构进行了优化, 计算了其性能, 获得稳定的几何构型、分子轨道及键级; 在振动分析的基础上求得体系的振动频率、IR谱及不同温度下的热力学性质, 并得温度对热力学性能影响的关系式. 结果表明: DAAT分子结构中偶氮基两侧的四嗪环和氨基基本在同一个平面上, 形成一个大的共轭π键; 红外谱计算频率和强度与实验结果整体吻合较好; 热能( )、热容( )和熵( )均随温度的升高而增大.     

3,3''''-偶氮-(6-氨基-1,2,4,5-四嗪)的合成及性能研究

以3,6-对(3,5-二甲基吡唑)-1,2,4,5-四嗪(BT)为起始物,经亲核取代、氧化脱氢、氨解和水解等四步反应,合成了高氮含能化合物3,3'-偶氮-(6-氨基-1,2,4,5-四嗪)(DAAT).对DAAT的热分解性能进行了研究,由DSC、PDSC和TG-DTG技术获得了DAAT的热分解动力学参数和机理函数.结果表明,DAAT的热稳定性好,能量高.在5℃/min升温速率下,DAAT在283℃左右开始分解,放热峰值320℃,分解放热峰的分解焓为1974.33J/g,高于相同条件下硝胺系炸药HMX的分解焓;采用Kissinger法和Ozawa法求得其活化能分别为209.69和208.77kJ/mol;其热分解速率对压强比较敏感,且与环境压强成正比.采用VLW EOS对DAAT的爆轰性能进行了理论计算,结果表明将DAAT与传统含能材料混合,有望制备出高能钝感炸药.     

Synthesis, Crystal Structure Analysis and DFT Calculation of 1-Benzoyl-3,6-diphenyl-1,4-dihydro-1,2,4,5-tetrazine

The new title compound, 1-benzoyl-3,6-diphenyl-1,4-dihydro-1,2,4,5-tetrazine (C21H16N4O, Mr = 340.38), has been prepared and its crystal structure can not be confirmed by the results of MS, elemental analysis, IR spectrum and 1H NMR spectrum, but determined by X-ray diffraction. The title compound crystallizes in an orthorhombic space group P212121 with a = 7.1100(19), b = 12.115(3), c = 19.884(6), V = 1712.7(8)3, Z = 4, Dc = 1.320 g/cm3, F(000) = 712, μ = 0.085 mm-1, MoKa radiation (λ = 0.71073), R = 0.0334 and wR = 0.0845 for 2254 observed reflections with I 2σ(I). X-ray diffraction analysis reveals that the central tetrazine adopts an unsymmetrical boat conformation. According to the bond lengths of tetrazine ring, the molecule should be 1,4-dihydro-1,2,4,5-tetrazine, rather than 1,2-dihydro-1,2,4,5-tetrazine. The crystal structure is stabilized mainly by intermolecular N–H···O hydrogen bonds.     

Modeling of 1,2,4,5-tetrazine complexes with organic amines

Tetrazine complexes with organic ligands have been modeled. The composition and structure of the model complexes agree with experimental data. The structure and nature of the complexes affect a number of chemical reactions of 1,2,4,5-tetrazines with organic amines. It is shown that the possibility and route of nucleophilic substitution in the 3 and 6 positions of the tetrazine ring are provided by amine localization in the tetrazine complex and also by the orbital characteristics of the reagents. The route and possibility of cycloaddition reactions for tetrazines are dictated by the ability of the latter to form π-complexes with reagents and by the orbital characteristics of the complexes. The route of the cycloaddition reaction is also affected by the solvent.     

Clicking 1,2,4,5-tetrazine and cyclooctynes with tunable reaction rates

Substituted tetrazines have been found to undergo facile inverse electron demand Diels-Alder reactions with "tunable" reaction rates.     

Synthesis and spectral characteristics of a novel heterometallic binuclear complex on the basis of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine

Binuclear bridged complexes [(bpy)₂Ru(μ-bptz)Re(CO)₃·(Hlg)](X)₂ [bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; Hlg = Cl, X = BF₄ or Hlg = Br, X = NO₃]. Were synthesized and studied by mass spectrometry and infrared and electronic spectroscopy. The complexes give a strong long-wave band in the electronic absorption spectrum. The spectra were interpreted on the basis of TD DFT quantum-chemical calculations.     

基于3,6-二肼基-1,2,4,5-四嗪的两种高氮含能离子盐

本文通过3,6-二肼基-1,2,4,5-四嗪(DHT)分别与高氯酸和硝酸反应得到2种高氮含能离子盐,并通过X-射线单晶衍射技术对它们的结构进行了表征。(DHT)(NO₃)₂(1)属于单斜晶系,C2/c空间群,晶胞参数:a=1.3000(6)nm,b=0.8349(3)nm,c=1.0187(5)nm,β=118.89(5)°,Z=4;(DHT)(ClO₄)₂(2)属于正交晶系,P2₁2₁2空间群,晶胞参数:a=0.9804(4)nm,b=1.0747(4)nm,c=0.5325(2)nm,Z=2。采用DSC和TG-DTG技术研究了这两种含能离子盐的热分解机理,并对这两种含能离子盐的非等温动力学、爆热及感度进行了测试分析。研究表明这两种含能离子盐在敏感型含能材料领域具有潜在的应用前景。     

基于3,6-二肼基-1,2,4,5-四嗪的两种高氮含能离子盐

本文通过3,6-二肼基-1,2,4,5-四嗪(DHT)分别与高氯酸和硝酸反应得到2种高氮含能离子盐,并通过X-射线单晶衍射技术对它们的结构进行了表征。(DHT)(NO₃)₂(1)属于单斜晶系,C2/c空间群,晶胞参数：a=1.300 0(6) nm,b=0.834 9(3) nm,c=1.018 7(5) nm,β=118.89(5)°,Z=4;(DHT)(ClO₄)₂(2)属于正交晶系,P2₁2₁2空间群,晶胞参数：a=0.980 4(4) nm,b=1.074 7(4) nm,c=0.532 5(2) nm,Z=2。采用DSC和TG-DTG技术研究了这两种含能离子盐的热分解机理,并对这两种含能离子盐的非等温动力学、爆热及感度进行了测试分析。研究表明这两种含能离子盐在敏感型含能材料领域具有潜在的应用前景。     

3,6-二肼基-1,2,4,5-四嗪的晶体结构及理论研究

通过缓慢蒸发溶剂法培养得到3, 6-二肼基-1, 2, 4, 5-四嗪(DHT)的单晶, 用X-射线单晶衍射仪进行了结构测定. 该晶体属于单斜晶系, P2(1)/c空间群, a=4.032 (4) ?, b=5.649 (6) ?, c=12.074 (14) ?. β=99.32°, Z=2, V=271.4(5) ?3. DHT分子中肼基N原子与四嗪环基本位于同一平面呈现轴对称结构, 分子中的大量氢键使之形成箭尾形排列的三维网络结构. 通过实验测得DHT的燃烧热为1787kJ?mol-1, 5s爆发点为454 K. 在DFT-B3LYP/6-311G*水平下对DHT的电子结构和自然键轨道进行了分析. 通过原子化能的方法计算得到DHT的标准生成热为1075 kJ?mol-1, 与实验值接近. 爆轰性能计算表明, DHT在密度为1.64 g?cm-3时, 爆速和爆压分别为9.27 km?s-1和36.02 GPa, 高于TNT和HMX.     

3,6-二氨基-1,2,4,5-四嗪二聚体分子间相互作用的理论研究

在DFT-B3LYP/6-31G(d)水平下,求得3,6-二氨基-1,2,4,5-四嗪二聚体势能面上3种优化几何构型和电子结构。经基组叠加误差(BSSE)和零点能(ZPE)校正,求得分子间最大相互作用能为-38.88kJ/mol。电荷分布与转移分析表明,二子体系间的电荷转移很少,但接触点上氮原子和氢原子电荷变化比较大。由自然键轨道(NBO)分析揭示了分子间相互作用的本质。对优化构型进行振动分析,并基于统计热力学求得200.0~800.0 K温度范围从单体形成二聚体的热力学性质变化,发现二聚主要由强氢键所贡献,二聚过程在较低温度或常温下能自发进行。     

High-frequency EPR study of reduced diruthenium and dirhenium polypyridine complexes based on the 1,2,4,5-tetrazine radical bridge

The radical complexes [(micro-L)[Ru(bpy)(2)](2)]*(3+), [(micro-bmtz)[Ru(cym)Cl](2)]*(+) and [(micro-L)[Re(CO)(3)Cl](2)]*(-), where L are 3,6-disubstituted 1,2,4,5-tetrazines such as 3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine (bmtz) and cym =p-cymene, were studied by X-band EPR in fluid solution and by 285 GHz EPR in glassy frozen solution. A comparison with other transition metal complexes (Cu, Rh, Os, Ir, Pt) involving tetrazine radical ligands reveals that the g anisotropy reflects (i) the pi acceptor effect of the tetrazine substituents, (ii) the competition from ancillary pi acceptor ligands for back donation from the metal, and (iii) the spin-orbit coupling contributions from the transition metal.     

X-ray shielding polyurethanes: Synthesis and characterization

Synthesis and characterization of X-ray shielding thermoplastic polyurethane elastomers which are capable of blocking harmful radiation emitted by various sources are reported. X-ray shielding capability was generated in the polymer by covalently binding iodine atoms in a monomer and polymerizing it with other monomers such that the resultant polymer has the capability of shielding X-radiation. For rendering X-ray shielding capability to the polyurethane, Bisphenol-A (BPA) was iodinated to 4,4′-isopropylidinedi-(2,6-diiodophenol) (IBPA) and it was used as a chain extender during the synthesis of polyurethane. Polyurethanes were synthesized by reacting 1,6-diisocyanatohexane and IBPA with two different polyols, namely, poly(tetramethylene glycol) and poly(hexamethylene carbonate) diol. X-ray shielding polyurethanes (XPU) were characterized by infrared spectroscopy, thermogravimetry, dynamic mechanical analysis, energy-dispersive X-ray analysis, gel permeation chromatography, and X-radiography. Studies showed that by effectively changing polyol from polyether to polycarbonate, XPUs having different physicomechanical properties could be manufactured. Furthermore, these polyurethanes were also found to be noncytotoxic to L929 fibroblast cell lines. X-ray images revealed that the incorporation of IBPA has rendered X-ray opacity to the polyurethanes which are several times higher than the aluminum wedge of equivalent thickness. The materials are sufficiently flexible and rubbery, so can be used as coatings, films, or sheets for applications in energy sector, power-generating nuclear power plants, defense sector (bunkers for army personnel), medical applications (X-ray diagnostic and CT scanner rooms, gamma radiation therapy of cancer), etc.