Molecular Recognition Of β-Cyclodextrin To Nitro-compounds And Its Catalysis

Cyclodextrins (CDs) are very important compounds in superamolecular chemistry , and the complexes of cyclodextrins with small molecules have been studied very commonly. While only a few inclusion complexes of cyclodextrins with nitro-compounds have been reported. Nitro-compounds are kinds of thermally unstable materials. When they are analyzed by gas chromatography-mass spectrometry (GC-MS), they will decompose due to the high temperature in the ion source of GC-MS. So the molecular ions of these energetic compounds cann't be obtained especially to energetic compounds containing the -NNO₂ and -ONO₂ groups by GC-MS. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has become a very powerful instrument to analyze large synthetic polymers and biomacromolecules. But for analysis of low-mass analytes, especially for the weights of the mass-to-charge analytes less than 500 Da, it has been a challenge to analyze by MALDI-TOF-MS. Because most of the currently used matrixes have molecular weights less than 300 Da, and during laser irradiation, they also act as their own matrixes, producing a variety of matrix-related ions. These ions of matrix will interfere to verdict the molecular ions of the analytes. Thus it is difficult to analyze low-mass analytes by MALDI-TOF-MS.In this dissertation, five kinds of small molecular weight compounds formed inclusion complexes withβ-cyclodextrin according to characterizing by ¹HNMR, IR, XRD and HPLC. Four kinds of thermally unstable nitro-compounds were also analyzed through the inclusion complexes ofα- orβ-cyclodextrin by ESI-MS. The novel method has resolved the tanglesome problem of determining the energetic molecular weights with low molecular weight (MW) through the complexes ofα- orβ-cyclodextrin with these four containing -ONO₂ and -NNO₂ compounds by ESI-MS. The molecular weights of one composite explosive, one propellant with unknown components and 14 single-compound explosives were measured by MALDI-TOF-MS using CD's inclusion complexes with these small molecular weights of nitro compounds. The novel method has resolved the difficult problem that low molecular weights cann't be measured directly by MALDI-TOF-MS. Using the recognition ofβ-CD to the nitro-compounds and energetic materials, four nanotubes were prepared. A controlled single substituted aniline and its derivatives were achieved withβ-cyclodextrin as catalyst. 2,2'-Bipyridinyl-5,5'-dicarboxylic acid was synthesized by one-step reaction of 2,2'-bipyridinyl (BPY) withβ-cyclodextrin as catalyst.The main contents and the main innovative results are as follows:[1] The development of cyclodextrins and its application in mass spectrometry, nitro-compounds, self-assemble and catalysis are reviewed.[2] The inclusion complexes ofβ-CD with the small molecular weight nitro-compounds, 3,4-dinitro-toluene(3,4-DNT), 2,6-dinitro-toluene(2,6-DNT), 2,5-dinitro-toluene(2,5-DNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octah-ydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX) were prepared in the mixture solution of water and acetone, and characterized by IR, XRD, ¹HNMR and HPLC, showing that the inclusion complexes of 3,4-DNT, 2,5-DNT, 2,6-DNT, RDX and HMX form inclusion complexes withβ-CD. The mechanism of forming inclusion complexes ofβ-CD with low molecular weight nitro-compounds was presumed.[3] LC-ESI mass spectra of the binary mixtures RDX/HMX and 1,2,3-trinitro-propantriol(NG)/1,2,4-trinitro-butanetriol(BTTN) were determined by LC-ESI-MS technique. The binary mixtures NG/BTTN and RDX/HMX were separated by the reversed-phase high performance liquid chromatography on the C₁₈ column. The factors, such as CapEx (capillary exit) voltage which can produce characteristic fragmentation ions through adjusting the voltage called CID, pH values, electron modes and the temperature of drying gas affacting the mass spectra of RDX /HMX and BTTN/NG systems were studied. The molecular ions, characteristic fragmentation ions and adduct ions including [M-H+H₂O]^-, [M-H+2H₂O]^-, [M -H+NO₂]^- and [M-H+62]^- were obtained, so these fragmentation ions and adduct ions disturb to verdict the molecular ions. Noncovalent complexes betweenα-cyclodextrin(α-CD) with NG and BTTN,β-CD with RDX and HMX formed in aqueous solution were investigated. The results obtained by ESI-MS show that there are only the molecular ions of the complexes andα-CD orβ-CD. According to the molecular weights of the complexes andα-CD orβ-CD, the weights of NG, BTTN, RDX and HMX were obtained easily by subtracting theα-CD orβ-CD ions from the complexes ions. The intensive mass-to-charge ratios of the molecular complexes are very strong, showing thatα-CD has a strong recognition ability to NG and BTTN andβ-CD to RDX and HMX. The spectra of NG, BTTN, RDX and HMX are tanglesome, while the spectra of the complexes of NG and BTTN withα-CD, RDX and HMX withβ-CD are very simple, and the molecular weights of NG, BTTN, RDX and HMX are easily obtained.[4] A novel method for determining the molecular weights of low molecular weight (MW) energetic compounds through their complexes ofβ-CD and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in a mass range of 500-1900 Da, avoiding matrix interference was presented. The MWs of one composite explosive composed of 2,6-DNT, TNT and RDX, one propellant with unknown components and 14 single-compound explosives (RDX, HMX, 3,4-DNT, 2,6-DNT, 2,5-DNT, 2,4,6-TNT, TNAZ, DNI, BTTN, NG, TO, NTO, NP and 662) were measured. The molecular recognition and inclusion behaviour ofβ-CD to energetic materials (EMs) were investigated. The results show that (1) the established method is sensitive, accurate and suitable for determining the MWs of low-MW single-compound explosives and energetic components in composite explosives and propellants; and (2)β-CD has good inclusion and modular recognition abilities to the above EMs.[5] Novel nanotubes ofβ-CD with 2-chloro-6-methoxy-3,5-dinitro-pyrazine (CMDPZ), barium 3-nitro-l,2,4-triazol-5-onate ((NTO)₂Ba), lead 3-nitro-1,2,4-triazol-5-onate ((NTO)₂Pb), copper 3-nitro-1,2,4-triazol-5-onate ((NTO)₂Cu), were prepared usingβ-CD recognition. Their morphologies and structures were characterized by IR, ¹H-NMR, ¹³C-NMR, elemental analyses, flame atomic absorption spectrometry and SEM. The inclusion mechanism of the inclusion compound was presumed. The results show that (1) the molar ratio of forming the inclusion complexes byβ-CD with CMDPZ, (NTO)₂Ba, (NTO)₂Pb and (NTO)₂Cu is 1:1; (2) the nanowires are tetragonal lattice with a diameter of about 50 nm and the length of about a few cms, and grew along [001] axis.[6] A controlled single substituted reaction of aniline and its derivatives with benzylchloride was achieved withβ-CD as catalyst. Several benzylaniline and its derivatives o-methyl benzylaniline, p-methyl-benzyl aniline, were synthesized in 90-98% yields. 2,2'-Bipyridinyl-5,5'-dicarboxylic acid was synthesized by one-step reaction of 2,2'-bipyridinyl (bpy), carbon tetrachloride and copper powder in an aqueous alkali solution withβ-CD as catalyst at 80℃under nitrogen of atmospheric pressure, producing 2,2'-bipyridinyl-5,5'-dicarboxylic acid with 87% selectivity in 66 % yield. The mechanism of the reaction was presumed.[7] The chiral molecular recognition of (R or S)-2-butanol withα-CD .β-CDγ-CD was investigated by electro-spray ionization mass spectrometry. Using intensity of the relation between the complexes andα-CDβ-CD orγ-CD of mass spectra, the ratios of recognition and the relative ratios of recognition were obtained. The complex stability constant(K), standard free energy(â–³G⁰/kJ/mol ) were calculated for the 1:1 inclusion of two 2-butanol pairs of guests withα-CDβ-CD andγ-CD at 22℃. The influence of CapEx voltage on the mass spectra of complexes was studied. The results show that (1) the molecular recognition ofα-CDβ-CD andγ-CD to the guests of (R)-2-butanol and (S)-2-butanol decrease in the orderα-CDβ-CDγ-CD, while the strongest molecular ratio recognition isβ-CD; (2) the complex stability constants(K) and the complex standard free energy( Aâ–³G⁰/kJ/mol) are: 24.01 and -7.80 forα-CD with (R)-2-butanol, 25.00 and -7.89 forα-CD with (S)-2-butanol, 12.96 and -7.28 forβ-CD with (R)-2-butanol, 20.25 and -7.38 forβ-CD with (S)-2-butanol, 6.78 and -4.69 forγ-CD with (R)-2-butanol, 8.41 and -5.22 forγ-CD with (S)-2-butanol, respectively; (3)α-CD,β-CD andγ-CD have the recognition to (R or S)-2-butanol under different CapEx voltage.