Spectrophotometric studies on the thermodynamic properties of charge-transfer complexes between m-DNB (1,3-dinitrobenzene) with aliphatic amines in DMSO and determination of the vertical electron affinity of m-DNB

1,3-Dinitrobenzene formed colored 1:1 complexes with aliphatic amines (chromogenic agents) like isopropylamine,ethylenediamine, tetraethylenepentamine and bis(3-aminopropyl)amine in DMSO having absorption maxima at 563 nm, 584 nm, 580.5 nm and 555 nm respectively. The complexes were stable for more than 24 h. The accurate association constants KAD and other thermodynamic parameters were determined with D and A usually in stoichiometric ratios. But in case of m-DNB and bis(3-aminopropyl)amine, the association constants KAD and the thermodynamic parameters were also determined using Benesi-Hildebrand equation to show the variations of KAD under different conditions. ΔG° values were found to be negative in all cases resulting from exothermic enthalpy changes and favourable entropy changes. The energies of transition for the CT complexes hνCT found experimentally were considerably different from the energies of transition (from HOMO of donor to LUMO of acceptor) calculated using AM1 but the differences were considerably reduced using DFT calculations. The vertical electron affinity of m-DNB was calculated using the method suggested by Mulliken. However, no FTIR measurements of the complexes could be made due to experimental limitations.     

Absorbance change and static quenching of fluorescence of meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) by trinitrotoluene (TNT)

Meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) interacts with trinitrotoluene (TNT) and forms a 1:1 complex with a new absorbance peak at 422 nm. TNT quenches TPPS emission intensity at 645 and 702 nm when excited at 413 nm. The TPPS-TNT complex is formed in the ground state on the basis of a linear Stern-Volmer plot indicative of static quenching. The association constants determined from absorbance and fluorescence studies are in excellent agreement.     

一种环金属铱、铂双核配合物的合成及光电性能

设计合成了一种双核环金属铱,铂配合物二[N,N-2-(2,4-二氟苯基吡啶)C3,N1](吡啶甲酸)合铱(Ⅲ)-C₆-[苯基吡啶-C3,N1](吡啶甲酸)合铂(Ⅱ)(FIrPPyPt)。 通过核磁共振仪、元素分析仪、紫外-可见吸收光谱仪和光致发光光谱仪对其结构和性能进行了表征。 结果表明,配合物FIrPPyPt的紫外-可见吸收位于250~450 nm之间,荧光发射峰位于465和493 nm。 将配合物FIrPPyPt以质量分数1%~8%掺杂到主体材料聚乙烯基咔唑(PVK)+2-(联苯-4-芳基)-5-(4-叔丁基苯)-1,3,4-噁二唑(PBD)(30%)中制作了电致发光器件,在不同电压下电致发光光谱中,显现出铱配合物和铂配合物的特征峰,波峰位于400、500和530 nm蓝绿光区发射区。 该双核配合物用于单掺杂有机白光电致发光器件具有制作简单、色稳定性和重复性好等特点,为单掺杂白光发光器件提供了一种好的思路。     

Selective spectrophotometric determination of TNT using a dicyclohexylamine-based colorimetric sensor

Because of the extremely heterogeneous distribution of explosives in contaminated soils, on-site colorimetric methods are efficient tools to assess the nature and extent of contamination. To meet the need for rapid and low-cost chemical sensing of explosive traces or residues in soil and post-blast debris, a colorimetric absorption-based sensor for trinitrotoluene (TNT) determination has been developed. The charge-transfer (CT) reagent (dicyclohexylamine, DCHA) is entrapped in a polyvinylchloride (PVC) polymer matrix plasticised with dioctylphtalate (DOP), and moulded into a transparent sensor membrane sliced into test strips capable of sensing TNT showing an absorption maximum at 530 nm when placed in a 1-mm spectrophotometer cell. The sensor gave a linear absorption response to 5-50 mg L⁻¹ TNT solutions in 30% aqueous acetone with limit of detection (LOD): 3 mg L⁻¹. The sensor is only affected by tetryl, but not by RDX, pentaerythritoltetranitrate (PETN), dinitrotoluene (DNT), and picric acid. The proposed method was statistically validated for TNT assay against high performance liquid chromatography (HPLC) using a standard sample of Comp B. The developed sensor was relatively resistant to air and water, was of low-cost and high specificity, gave a rapid and reproducible response, and was suitable for field use of TNT determination in both dry and humid soil and groundwater with a portable colorimeter.     

Electrochemiluminescence Detection of TNT by Resonance Energy Transfer through the Formation of a TNT–Amine Complex

2,4,6‐Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)‐based detection of TNT through the formation of a TNT–amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3‐Aminopropyltriethoxysilane (APTES)‐modified [Ru(phen)₃]²⁺ (phen=1,10‐phenanthroline)‐doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES‐modified RuSiNPs through charge transfer from electron‐rich amines in the RuSiNPs to the electron‐deficient aromatic ring of TNT to form a red TNT–amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES‐modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES‐modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT–amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10^?9 to 1×10^?6 M with a fast response time within 1 min. The limit of detection is 0.3 nM . The method exhibits good selectivity towards 2,4‐dinitrotoluene, p‐nitrotoluene, nitrobenzene, phenol, p‐quinone, 8‐hydroxyquinoline, p‐phenylenediamine, K₃[Fe(CN)₆], Fe³⁺, NO₃^?, NO₂^?, Cr³⁺, Fe²⁺, Pb²⁺, SO₃^2?, formaldehyde, oxalate, proline, and glycine.     

Generation and optical properties of monodisperse wurtzite-type ZnS microspheres

Monodisperse wurtzite-type ZnS microspheres have been prepared by using glutathione (GSH) as a sulfur source at low reaction temperatures ranging from 160 to 210 degrees C. The diameter of the ZnS microspheres can be tuned from approximately 254 to approximately 597 nm by changing the reaction parameters such as temperature, molar ratio of reactants (GSH/Zn2+), and reaction medium (ethylenediamine or ammonia). Our results demonstrate that monodentate amines (ammonia) play the same role as that of bidentate amines (ethylenediamine) in the formation of the wurtzite-type ZnS microspheres. The formation process of the monodisperse ZnS microspheres consists of a GSH-dominated nucleation process and an amine-dominated assembly process. The as-synthesized monodisperse ZnS microspheres readily self-assemble into ordered hexagonal patterns and thus have potential applications as colloidal crystalline materials. Blue fluorescence emission peaks at 415 and 466 nm in wavelength, attributed to deep-trap emission, are observed at room temperature.     

Tetraphenylporphine zinc(II) coordination with primary amines and alcohols in chloroform

Changes in the thermodynamic and kinetic parameters of isoequilibrium coordination of tetraphenylporphine zinc(II) (Zn-TPP) with primary amines in chloroform at 283?C308 K follow expanded correlative Taft relation modified for amines. Dependences of stability constants of complexes on shifts of Zn-TPP absorption bands in electronic spectra caused by the reactions with primary amines and the corresponding alcohols are of a linear character, as well as the relations between rate constants of nucleophilic substitution and of complex formation. The formation of molecular complexes with certain amines is accompanied by the appearance of a new absorption band in the electronic spectra near 630 nm.     

Micro structural investigations on TNT and PETN incorporated silica xerogels

Silica xerogels incorporated with trinitrotoluene (TNT) and pentaerythritoltetranitrate (PETN) were synthesized using sol–gel method. Tetramethoxysilane was used as precursor for silica. TNT and PETN content in the resulted explosive/silica xerogel was varied ranging from 50 to 90%. Infra red spectra showed that explosives were retained in the silica xerogel matrix. Transmission electron microscopy (TEM) reveal that explosives particles were uniformly distributed in xerogel matrix and the size of the PETN and TNT particles are in the range 15–18 nm. Small angle x-ray scattering showed that the sizes of the pores in the silica matrix are in the range 25–13 nm. The particles of TNT and PETN occupy the pores in the matrix resulting in gradual reduction of pore-size affecting the surface characteristics of the pore-matrix interface. Understanding of the structure of aggregates of small particles thus produced could be useful to explain the properties shown by the fine explosives. Our study suggests that particle size of explosives in the nanometer range can be achieved using the sol–gel method.     

Thermal behaviour of nickel(II) sulphate,nitrate and halide complexes containing ammine and ethylenediamine as ligands

Thermal behaviour of nickel amine complexes containing SO₄ ²⁻, NO₃ ⁻, Cl⁻ and Br⁻ as counter ions and ammonia and ethylenediamine as ligands have been investigated using simultaneous TG/DTA coupled with mass spectroscopy (TG/DTA–MS). Evolved gas analyses detected various transient intermediates during thermal decomposition. The nickel ammonium sulphate complex produces NH, N, S, O and N₂ species. The nickel ammonium nitrate complex generated fragments like N, N₂, NO, O₂, N₂O, NH₂ and NH. The halide complexes produce NH₂, NH, N₂ and H₂ species during decomposition. The ligand ethylenediamine is fragmented as N₂/C₂H₄, NH₃ and H₂. The residue hexaamminenickel(II) sulphate produces NiO with crystallite size 50 nm. Hexaammine and tris(ethylenediamine)nickel(II) nitrate produce NiO in the range 25.5 nm and 23 nm, respectively. The halide complexes produce nano sized metallic nickel (20 nm) as the residue. Among the complexes studied, the nitrate containing complexes undergo simultaneous oxidation and reduction.     

(PtI6-2RDG)n缔合纳米微粒体系的共振散射、荧光猝灭和减色效应研究

在0.02mol/L HCl介质中，罗丹明6G（RDG）分别在530nm和550nm处有一个吸收峰和荧光峰，PtI6^2-与RDG^ 主要通过静电引力形成疏水性的PtI6-2RDG缔合物分子。PtI6-2RDG分子间存在较强的分子和和疏水作用力而生成（PtI6-2RDG)n缔合纳米微粒，其粒径为40nm，在400nm、470nm和590nm产生3个共振散射，其中400nm和590nm处的2个峰为其特征共振散射峰，550nm荧光峰和530nm吸收峰的降低是由于纳米微粒形成后，只有裹露在（PtI6-2RDG)n纳米微粒界面的RDG荧光分子才能吸收激发光子跃迁到激发态，进而返回基态产生荧光，而体体相的RDG荧光分子无法与激发光作用产生荧光，即与激发光作用的RDG分子数大为降低。当该纳米微粒体系加入乙醇后，由于乙醇致使（PtI6-2RDG)n纳米微粒分解为PtI6-2RDG分子，体系的红紫色和共振散射峰消失，吸收峰和荧光峰恢复，研究结果表明，红紫色（PtI6-2RDG)n纳米微粒的形成是其共振散射增强、荧光猝灭、减色效应和产生特征共振散射峰的根本原因。     

Molecular complexes of iodine with metal acetylacetonates

The ability of metal acetylacetonates to act as electron donors and form molecular complexes with I₂ was studied by examining the electronic, vibrational, and NMR spectra of the complexes. The specific compounds used in the study were Al(acac)₃ Sc(acac)₃ Zr(acac)₄, and Th(acac)₄. The electronic spectra of mixtures of the metal acetylacetonates with I₂ in CHCl₃ had, in addition to the absorption peaks characteristic of the free components, two peaks that were due to the charge transfer complexes. For each complex, the highest wavelength peak (near 360 nm) was assigned to the blue shifted I₂ band, while the lower peak (between 270 nm and 305 nm) was attributed to the intermolecular charge transfer. In the i.r. spectra of each complex, the major effect of complexation was to cause the I₂ stretching frequency to appear between 145 cm⁻¹ and 160 cm⁻¹. The positions of the absorption peaks in both the electronic and vibrational spectra led to the conclusion that in these complexes, I₂ had received a large amount of charge from the donors. Complex formation had little effect on the NMR spectra of the donors. Association constants of 1:1 complexes were determined from the concentration dependence of the absorbance of the blue shifted I₂ bands. Values of ΔHdg and ΔS°₂₉₈ for the complex formation were obtained from the temperature variation of the association constants. The data indicate that the complexes are extremely stable species. Both the stability of the complexes and the high degree of charge transfer were rationalized by considering a model for the intermolecular interactions that involved two M(acac) rings simultaneously transferring charge from one donor to an I₂ molecule.     

某些蒽环类抗癌药物与刚果红相互作用的吸收、荧光和共振瑞利散射光谱研究

在pH 2.5左右的酸性介质中, 刚果红与表柔比星、柔红霉素和米托蒽醌等蒽环类抗生素反应形成离子缔合物时, 仅能引起吸收光谱和荧光光谱的微小变化, 但却能导致共振瑞利散射(RRS)的显著增强并产生新的RRS光谱, 与此同时也观察到二级散射(SOS)和倍频散射(FDS)的增强. 最大RRS峰位于370 nm附近, 并在280 nm附近有另一散射峰. 而它们的SOS峰均在530 nm附近, 最大FDS峰均位于353 nm处. 其中RRS法灵敏度最高, 它对表柔比星、柔红霉素和米托蒽醌的检出限分别为0.054, 0.058和0.033 μg/mL, 而其线性范围分别为0.05～12.0, 0.05～12.0和0.04～7.5 μg/mL. 文中研究了反应产物的吸收、荧光和RRS光谱特征, 适宜的反应条件及分析化学性质, 据此发展了一种用RRS技术灵敏、简便、快速测定蒽环类抗癌药物的新方法.     

Thermo-X-ray-diffraction analysis of dimethylsulfoxide-kaolinite intercalation complexes

DMSO-kaolinite complexes of low- and high-defect Georgia kaolinite (KGa-1 and KGa-2, respectively) were investigated by thermo-XRD-analysis. X-ray patterns showed that DMSO was intercalated in both kaolinites with a d(001)-value of 1.11 nm (type I complex). The samples were gradually heated up to 170°C and diffracted by X-ray at room-temperature. With the rise in temperature, due to the thermal evolution of the guest molecules, the relative intensity of the 1.11 nm peak decreased and that of the 0.72 nm peak (neat kaolinite) increased indicating that the fraction of the non-intercalated tactoids increased. The 1.11 peak disappeared at 130–140°C. During the thermal treatment of both complexes two additional peaks appeared at 110 and 120°C, respectively, with d-values of 0.79–0.94 and 0.61–0.67 nm in DMSO-KGa-1 and 0.81–0.86 and 0.62–0.66 nm in DMSO-KGa-2, indicating the formation of a new phase (type II complex). The new complex was obtained by the dehydration of type I complex and was composed of intercalated DMSO molecules which did not escape. The new peaks disappeared at 150–160°C indicating the complete escape of DMSO.     

Synthesis and photoluminescence of ZnS macrolattice

ZnS macrolattice has been synthesized by an ultrasonication-assisted method. It is a face-centred cubic stucture with a lattice constant of about 5.4 nm. Each basis in one unit cell composes of about 1,400 atoms. The d-spacing of the macrolattice is about 10 times to that of ordinary sphalerite crystalline. The new structure can be confirmed by small angle X-ray diffraction, high-resolve TEM and selected area electron diffraction. The emission spectrum of the ZnS macrolattice consists of two main peaks at about 333 and 349 nm, respectively under 236 nm excitation. However, it consists of only one main peak at about 438 nm under 370 nm excitation and only one main peak at about 530 nm under 473 nm excitation. The near band transition about 349 nm demonstrates that the valence band composed of P-type function on the S atom splits to two bands. The conduct band has also split because of many peaks in the excitation spectra. In addition, some defect energy levels must appear in the band gap because blue and green emissions are observed.     

Characterization of the autofluorescence of polymorphonuclear leukocytes, mononuclear leukocytes and cervical epithelial cancer cells for improved spectroscopic discrimination of inflammation from dysplasia

Fluorescence spectroscopy has the potential to improve the in vivo detection of intraepithelial neoplasias; however, the presence of inflammation can sometimes result in misclassifications. Inflammation is a common and important pathologic condition of epithelial tissues that can exist alone or in combination with neoplasia. It has not only been associated with the presence of cancer but also with the initiation of cancer by damage induced due to the oxidative activity of inflammatory cells. Microscopic examination of cervical biopsies has shown increased numbers of polymorphonuclear and mononuclear leukocytes in inflamed tissues mostly confined to the stroma. The purpose of this study was to characterize the fluorescence properties of human polymorpho- and mononuclear leukocytes and compare their fluorescence to that of cervical cancer cells. Human neutrophils were purified from peripheral blood and their fluorescence characterized over an excitation range of 250-550 nm. There are four notable excitation emission maxima: the tryptophan peak at 290 nm excitation, 330 nm emission; the NAD(P)H peak at 350 nm excitation, 450 nm emission, the FAD peak at 450 nm excitation, 530 nm emission and an unidentified peak at 500 nm excitation, 530 nm emission. Treatment of these peripheral blood neutrophils with 40 nM phorbol myristate acetate or with the chemotactic peptide formyl-Met-Leu Phe (1 M) demonstrated a significant increase in NAD(P)H fluorescence. Isolated mononuclear cells have similar emission peaks for tryptophan and NAD(P)H and a small broad peak at 450 nm excitation, 530 nm emission suggestive of FAD. Comparison of the fluorescence from leukocytes to epithelial cancer cell fluorescence has demonstrated the presence of these fluorophores in different quantities per cell. The most notable difference is the high level of tryptophan in cervical epithelial cancer cells, thus offering the potential for discrimination of inflammation.     

A DFT Study on Estrone – TNT Interaction

Trinitrotoluene, known as TNT, is a widely used powerful explosive. It is a poisonous material, which injures almost all cells, especially those of liver, bone marrow, and kidney. Estrone is a sex hormone having an electron rich aromatic (phenolic) ring that is capable of forming a π complex with molecules containing an electron deficient π system. This study has focused on investigating the tendency of the complex formation of TNT with estrone. It has been thought that the formation of estrone‐TNT π complex might take place in a human body exposed to acute or prolong period of this hazardous chemical and consequently estrone activities might be impaired. The complex formation reaction was investigated mainly using DFT method with B3LYP/6‐31G(d, p) basis set in gas phase. The existence of π interaction between estrone and TNT was demonstrated by computational spectroscopic analyses (UV/Vis, IR, and ¹H NMR techniques). The frontier molecular orbital (HOMO and LUMO) analyses have shown that the considered π complex is very resistant to oxidation with respect to its components, estrone and TNT.     

Electrochemical and spectroscopic studies of metal cyclam complexes with thiocyanate. Evidence for mixed ligand complex formation

Complexes of Ni^II, Co^II and Cu^II containing the macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane (cyclam), and their ability to form mixed ligand complexes with thiocyanate have been studied. These complexes in a 1:2 mole ratio, exhibit new absorption peaks at 450, 538 and 512 nm respectively. Addition of thiocyanate to the nickel–cyclam complex (1:2:5 mole ratio) led to the formation of a purple complex, exhibiting three distinct new absorption peaks at 330, 455 and 662 nm. A purple complex (1:2:10 mole ratio) separated, having absorption peaks at 352, 503 and 693 nm in CHCl₃. The Co^II–cyclam complex with thiocyanate in the same mole ratio exhibits two absorption peaks at 437 and 519 nm without appearance of any precipitate. The Cu^II–cyclam complex with thiocyanate did not form a mixed ligand complex. Electrochemical studies also confirmed the complex formation of Ni^II–cyclam with the thiocyanate with the appearance of two new oxidation peaks close to 1.25 and 1.60 V versus Ag/AgCl in H₂O and CHCl₃. The Co^II–cyclam complex with thiocyanate exhibited an oxidation peak at 1.2 V versus Ag/AgCl, while no peak was observed for the Cu^II–cyclam complex with thiocyanate. Based on spectroscopic and electrochemical studies the geometry of the complex has been evaluated.     

Simultaneous spectrophotometric analysis of aliphatic amines utilizing thermochromism of charge-transfer complexes with tetrabromophenolphthalein ethyl ester.

Aliphatic amines, such as n-hexylamine (primary), di-n-hexylamine (secondary) and tri-n-hexylamine (tertiary amine), react with tetrabromophenolphthalein ethyl ester molecules (TBPEH) to form reddish or red-violet charge-transfer complexes (CT complexes) in 1,2-dichloroethane (DCE). The absorption maxima of the CT complexes with all primary amines occur at around 560 nm, with secondary amines at 570 nm and, with tertiary amines at 580 nm. The CT complex formation constants with TBPEH in DCE increase in the order of the primary, secondary and tertiary amines, but their constants decrease quantitatively with an increase in temperature. This phenomenon (thermochromism) could be applied to the simultaneous spectrophotometric determination of primary amine and secondary amine, or secondary amine and tertiary amine in a mixed solution utilizing the difference of absorbance with temperature changes.     

Absorption cross section and photolysis of OIO

Pulsed laser photolysis combined with transient absorption spectroscopy and resonance fluorescence was used to examine the photolysis of OIO at a number of wavelengths corresponding to absorption bands in its visible spectrum between approximately 530 and 570 nm. Photolysis at 532 nm was found to result in substantial depopulation of the absorbing ground state, enabling an estimate for the absorption cross section of OIO at 610.2 nm of (6 +/- 2) x 10(-18) cm2 molecule(-1) to be obtained. No evidence was found for I atom formation following photolysis of OIO at 532, 562.3, 567.9 and 573.8 nm, enabling an upper limit to the I atom quantum yield of < 0.05 (560-580 nm) and < 0.24 (532 nm) to be established.     

A Possible Complex between TNT and Epinephrine – A DFT Study

The interaction between TNT and a vitally significant biological molecule, epinephrine, was investigated at the level of density functional theory. Two models are constructed; (i) an intimate pair of TNT and epinephrine and (ii) a π complex of them. The calculations (in vacuo conditions) have showed that these molecules in the intimate pair model orient themselves in an angular arrangement, whereas a π complex formation between these molecules is quite likely in the case of parallel arrangement of aromatic rings. The calculated electrostatic charges, UV and NMR spectra support the idea of a strong interaction between TNT and epinephrine whatever the type of interaction is.