Study of internal structure of meso-tetrakis (4-sulfonatophenyl) porphine J-aggregates in solution by fluorescence microscope imaging in a magnetic field

To determine the internal molecular arrangement of organic dye aggregates, a technique for observing the fluorescence microscope image of a solution consisting of dye aggregates in a magnetic field was developed. Using this technique, the fluorescence image of meso-tetrakis (4-sulfonatophenyl) porphine (TPPS) J-aggregates in a solution in a magnetic field of 10 T was observed. It was observed that individual rod-shaped TPPS aggregates (4-20 microm in length) were aligned parallel to the applied field. The polarized absorption spectra of the sample solution were also measured in the fields of up to 10 T. The spectra show the magnetic field dependence of the J-band intensity, reflecting the magnetic alignment of the aggregates. On the basis of the magnetic and optical properties obtained by the experiments, it was proposed that TPPS J-aggregates have a tube-like structure and are constructed from one-dimensional molecular arrays that are stacked parallel to the long axis of the tube.     

Effects of a magnetic force on surface-enhanced Raman spectra of a cysteamine linking magnetic particle and a silver colloid plate.

The effects of a magnetic force on magnetic particles linked by cysteamine to a silver colloid plate were analyzed with surface-enhanced Raman scattering spectroscopy. Cysteamine molecules were stretched by a force exerted on the magnetic particles with the external magnetic field gradients generated by two Nd-Fe-B magnets. The spectra showed that the relative intensity ratio of C-S (trans) to C-S (gauche) of cysteamine was increased 2 - 3 times within 30 min under the application of magnetic field gradients. Also, the shift of C-S (T) was observed up to 4 cm(-1) to higher frequency. These results suggested that an extension of the distance between a magnetic particle and a silver colloid induced isomerization from the gauche conformation to the trans conformation, accompanied by probable thiolate migration on the silver colloid surface.     

D-和L-丙氨酸的磁手性相变

利用变温直流磁化率测定, 在外加磁场强度为1 T, 磁场平行晶体c轴, 发现在温度270 K, D-和L-丙氨酸发生磁手性相变. 结合中子衍射确定磁手性相变机制为, D-和L-丙氨酸中的(N+H)有类金属氢原子特性, 在相变点270 K, 由(N+H)释放的电子自旋有磁手性. 用变温偏振拉曼光谱进一步证明, D-丙氨酸中的(N+H)的电子自旋(↑), 而L-丙氨酸中的电子自旋(↓), 处于高低不同的能态.磁手性相变(宇称和时间反演都破缺)能差为10^-4-10^-5 eV·molecule^-1.     

四-(对-磺基苯基)卟啉二酸(H_4~(2+)TSPP)分子聚集体的共振喇曼光谱研究

研究了四－（对－磺基苯基）卟啉二酸（Ｈ２＋４ＴＳＰＰ）的Ｊ－聚集体共振喇曼光谱,用氘代法考察了各喇曼谱带的同位素位移．指认３条低波数喇曼带为分子聚集体的晶格模．喇曼光谱退偏比测量表明,聚集体中Ｈ２＋４ＴＳＰＰ的对称性较分子态降低．比较游离碱Ｈ２ＴＳＰＰ和分子态Ｈ２＋４ＴＳＰＰ共振喇曼光谱讨论了聚集体中Ｈ２＋４ＴＳＰＰ的结构变化．Ｈ２＋４ＴＳＰＰ在聚集体中以接近面对面方式排列     

Magnetic Chirality Transitions of D- and L-Alanine

A chiral spin state of (N⁺H) in D- and L-alanine was established by monitoring the temperature dependence of dc-magnetic susceptibility (dc: direct current) under the external magnetic field of 1 T. An intrinsic spin chirality of electrons in the atomic magnetic dipole moment of (N⁺H) was also supported by polarized Raman spectroscopy. Magnetic chirality was associated with a strongly correlated electron system that was related to spin rigidity. Raman vibrational spectra were unrelated to structural chirality but could reflect spin chirality due to the reversal of motion breaking. The spin transition of (N⁺H) occured at 270 K without bond breaking but was assisted by an intermediate hydrogen bond elongation, splitting and reformation with NH₃⁺ torsion. The energy difference of spin chirality transitions between D- and L-alanine was around 10⁻⁴-10⁻⁵ eV·molecule⁻¹.     

Orientation change of porphyrin in aggregate caused by counterion

Aggregates of the diacid form of meso-tetraphenylporphyrin (TPP) were formed by evaporating organic solutions on quartz substrate. The effect of counterions on TPP aggregates, which were obtained through adding various kinds of acids HX(X = HSO₄, NO₃, Br and Cl) to TPP dichloromethane solution, has been investigated through the combined use of UV–vis absorption and Raman scattering spectroscopy. The protonated TPP and the resulting aggregates exhibited spectroscopic features that were remarkably influenced by the nature of counterions. For all the aggregates, split of the B state absorptions with components red- and blue-shifted relative to their diacid solution values indicated the J-type arrangement of TPP molecules was formed in the aggregates, and the magnitude of this shift was markedly influenced by the nature of the counterions; the (C_b ? H) in-plane bending vibrational bands in the Raman spectra of the aggregates also showed dependence on counterions. A model for TPP J-aggregates has been proposed on the basis of the angle between transition moment along the chain and the projected line connecting the centers of porphyrins onto the porphyrin plane, and the extended evidence was also obtained by investigation of the Raman spectra of the aggregates from the sulfuric diacid TPP organic (toluene, dichloromethane, acetone and chloroform) solutions, and T(4-NO₂P)P, T(4-MeOP)P dichloromethane solutions.     

Photoassisted magnetization of fullerene C60 with magnetic-field trapped Raman scattering

We report a photoassisted method to magnetize microcrystal fullerene C(60) at room temperature by exciting it to triplet states via a proper laser radiation and then trapping the spin-polarized states under a strong magnetic field. Novel changes on Raman scattering of the C(60) microcrystals were observed in the presence and absence of the magnetic field. In particular, the Raman spectra were found to exhibit a "hysteresis" phenomenon when the external magnetic field was removed. In light of this, we propose magnetic-field-trapped Raman spectroscopy (MFTRS) and employ first-principle calculations to reproduce the Raman activities of C(60) at different states. Further, MFTRS of the fullerene is demonstrated to originate from its photoassisted magnetization (PAM). The PAM strategy enables the magnetization of materials which consist of only light elements; meanwhile, the MFTRS investigation may open a new research field in Raman spectroscopy.     

Dynamics of magnetic-field-induced clustering in ionic ferrofluids from Raman scattering

Using Raman spectroscopy, the authors have investigated the aggregation/disgregation of magnetic nanoparticles in dense ionic ferrofluids (IFF) into clusters due to the action of an inhomogeneous external magnetic field. Evidence for changes in particle density and/or effective cluster size were obtained from the variation of the Raman intensity in a time window from 10 s to 10 min for magnetic fields up to 350 mT and at a temperature of 28 degrees C. Clustering sets in already at very low fields (>15 mT) and the IFF samples exhibit a clear hysteresis in the Raman spectra after releasing the magnetic field, which lasts for many hours at room temperature. The authors determined the characteristic times of the two competing processes, that of field-induced cluster formation and, at room temperature, that of thermal-activated dissociation, to range from 100 to 150 s.     

Merrifield树脂负载咪唑基离子液体磁性微球的制备与表征

制备了Merrifield树脂负载丙酸甲酯基咪唑基离子液体磁性微球。 采用FT-IR和XRD对结构进行了表征,采用TGA和VSM分别进行了热稳定性和磁性测试。 结果表明,丙酸甲酯基咪唑基离子液体成功负载到Merrifield树脂微球上,并通过共沉淀的方法实现了微球的磁性化,其磁组分为FeOOH和γ-Fe2O3混合物。 磁性微球的热稳定性优于无磁性的Merrifield树脂负载丙酸甲酯基咪唑基离子液体微球,在200 ℃以下不发生分解。 磁性微球的磁化强度为11.364 emu/g,显示出超顺磁性,无外磁场存在时不发生团聚。 沉降实验结果表明,在磁感应强度为3.0×10-4 T电磁场作用下,磁性微球10 s内即可从水相中基本分离完全,而没有磁场作用时磁性微球粒子基本不从水相中分离。     

Excitation wavelength dependent surface-enhanced Raman spectra of a dipping film of azobenzene-containing long-chain fatty acid on a silver mirror

Surface-enhanced Raman scattering (SERS) of dipping films of azobenzene-containing long-chain fatty acids, nAmH (n=8, 12, m=3, 5), on silver mirrors measured with a wide range of excitation wavelengths in the 457.9-1064 nm region is reported. The obtained Raman spectra show great SERS effect even with the 1064 nm excitation, and the excitation with 457.9, 476.5, and 488.0 nm gives surface-enhanced resonance Raman scattering (SERRS) due to the resonance effect of the symmetry-forbidden n-pi* transition of the azo group. Of particular note in the present study is that the SERS spectra with the excitation in the 532-1064 nm region yield Raman bands whose frequencies are almost identical to those bands in Raman spectra of nAmH in solid state while the SERRS spectra with the excitation in the 457.9-514.5 nm region show not only a set of bands which correspond to those of nAmH in the solid state but also a set of bands whose frequencies show a significant shift from those of the bands of nAmH in the solid state. These observations lead us to conclude that there are two kinds of molecular aggregates in the dipping films of azobenzene-containing long-chain fatty acid in which azobenzene moieties are condensed to form small bundles.     

Structure and bonding of the vanadium(III) hexa-aqua cation. 2. Manifestation of dynamical Jahn-Teller coupling in axially distorted vanadium(III) complexes

Ground-state spin-Hamiltonian parameters, magnetic data, and electronic Raman spectra of hexacoordinate vanadium(III) complexes are calculated with consideration to the ((3)A (3)E) e vibronic interaction and compared to experimental data. It is shown that the zero-field-splitting of the (3)A(g) (S(6)) ground term may be reduced significantly by the dynamical Jahn-Teller effect, particularly when the pi-anisotropy of the metal-ligand bonding interaction is significant, and the energy of the Jahn-Teller active vibration is comparable to the diagonal axial field. The dynamical Jahn-Teller effect may also give rise to a significant enhancement in the Raman intensity of overtones and higher harmonics of Jahn-Teller active vibrations, when the energies of these transitions fall in the proximity of intra-(3)T(1g) (O(h)) electronic Raman transitions. A simple method of conducting vibronic coupling calculations is described, employing ligand field matrices generated by angular overlap model calculations, which may in principle be applied to any transition metal complex.     

Magnetic field-induced reactions on the surface of chloroaluminum phthalocyanine thin films

The μ-(oxo)bis[phthalocyaninato] aluminum(III) (AlPc)(2)O films, with the crystallites oriented preferably in one direction, were obtained via chemical transformation of chloroaluminum(III) phthalocyanine AlClPc film upon its annealing in magnetic field. A comparative analysis of the influence of postdeposition annealing without and under applied magnetic field of 1 T on composition and morphology of AlClPc films has been carried out. The chemical transformation of AlClPc to (AlPc)(2)O on the substrate surface is studied by the methods of UV-vis and infrared spectroscopies, Raman, x-ray photoelectron spectroscopy as well as atomic force microscopy. Two interesting effects were observed upon heating the AlClPc films in magnetic field of 1 T. First, the temperature of the chemical transformation of AlClPc to (AlPc)(2)O decreased from 300 °C to 200 °C when magnetic field was applied during postdeposition annealing. Second, the formation of (AlPc)(2)O films with elongated crystallites with a preferential orientation was observed. The heating of (AlPc)(2)O films in a magnetic field at the same conditions did not demonstrate any effect on the structure and morphology of these films.     

Raman and UV-visible absorption spectra of ion-paired aggregates of copper porphyrins

Raman and UV-visible absorption spectra of ion-paired aggregate constructed from two copper porphyrins, copper tetrakis(4-N-methylpyridyl)porphyrin (CuTMPyP) and copper tetrakis(4-sulfonatophenyl)pophyrin (CuTSPP), are reported in this paper. The absorption bands of the aggregate was found exhibiting obvious shift and broadening, which are attributed to the excitonic coupling between the two paired porphyrin rings. The excitonic coupling in the aggregates also induces evident alteration for Raman intensities compared with monomer spectrum. Aggregation results in only small shifts (2-3 cm(-1)) for Raman lines connecting with the vibrations of porphyrin rings, manifesting only slight structural change of porphyrin skeletons. On the other hand, evident downshift (5 cm(-1)) was observed for the Cm-pyridyl stretch mode (1254 cm(-1)) of CuTMPyP, suggesting weakening of the Cm-pyridyl bonds by aggregation. Raman depolarization ratios of the aggregates are different from those of the monomers, implying a lowering of effective symmetry due to the molecular packing in the aggregates.     

聚苯胺-LiNi铁氧体复合纳米微粒的原位合成及其键合机制

通过原位溶液聚合法制备了聚苯胺-LiNi铁氧体(LiNi_0.5Fe₂O₄)复合纳米微粒, 用X射线衍射(XRD)、红外光谱(FTIR)、拉曼光谱(Raman)、紫外-可见光谱(UV-Vis)、透射电子显微镜(TEM)以及振动样品磁强计(VSM)等技术表征了复合物的结构、形貌和磁性能. 结果表明, 复合物在室温外加磁场下表现出亚铁磁性物质具有的磁滞现象, 铁氧体颗粒对苯胺的聚合起到了核的作用; 复合物中铁氧体与聚苯胺之间存在着比较明显的键合作用, 探讨了铁氧体与聚合物分子链之间的键合机制.     

Raman and infrared spectral study of meso-sulfonatophenyl substituted porphyrins (TPPSn,n = 1, 2A, 2O, 3, 4)

Raman and IR spectra of the free base p-sulfonatophenyl and phenyl meso-substituted porphyrins [5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4); 5,10,15-tris(4-sulfonatophenyl)-20-phenyl-porphyrin (TPPS3); 5,10-bis(4-sulfonatophenyl)-15,20-diphenylporphyrin (TPPS2A); 5,15-bis(4-sulfonatophenyl)-10,20-diphenylporphyrin (TPPS2O); and 5-(4-sulfonatophenyl)-10, 15,20-trisphenylporphyrin (TPPS1)] and their N-diprotonated derivatives (porphyrin diacids) were studied. The Raman spectra of the deuterated analogues of these porphyrins, in which the central hydrogen atoms were substituted with deuterium, were also measured. The observed vibrational bands were assigned on the basis of the deuteration shifts and compared with the structural analogues of these compounds. In IR spectra of the free-base porphyrins, the p-sulfonation of phenyl groups results in evident alteration for the phenyl modes and the porphyrin skeleton modes that are strongly coupled with phenyl vibrations. While the p-sulfonation of phenyl groups causes only slight changes for the high-frequency Raman bands (> 850 cm(-1)), dramatic shifts and band splitting were observed in the low-frequency region (< 500 cm(-1)) of Raman spectra. The observed differences of low-frequency Raman spectra were attributed to the alteration of the structure of the porphyrin ring, especially the CalphaCmCalpha bond-angles, by different meso-sulfonatophenyl substitutions. In addition, different packing style of TPPSn molecules in the aggregates is also responsible for the alteration of the vibrational spectra of the aggregated TPPSn.     

Counterion-dependent excitonic spectra of tetra(p-carboxyphenyl)porphyrin aggregates in acidic aqueous solution

Aggregates of the diacid form of tetra(p-carboxyphenyl)porphyrin (TCPP) are found to be stabilized in aqueous solution at low pH in the presence of poly(vinyl alcohol). At pH values in the range from about 1 to 4, a split Soret band is observed which is independent of counterion and tentatively assigned to a dimer species. As the pH is made lower than 1, the spectra evolve to reveal the presence of porphyrin aggregates. As in the case of the well-known aggregates of the related tetra(p-sulfonatophenyl)porphyrin (TSPP) diacid, the concentration of spectroscopically distinguishable aggregates increases with increasing ionic strength or decreasing pH. Unlike aggregates of TSPP, however, TCPP aggregates below pH 1 have visible absorption spectra which depend on the counterion, which is Cl(-) or NO(3)(-) in this study. In this work, we present visible absorption, light-scattering, and resonance Raman spectra of TCPP diacid in its monomer, dimer, and aggregated forms and attempt to understand the structural basis for counterion-dependent structure and excitonic coupling in the aggregates. Evidence is presented for intercalation of inorganic counterions between porphyrin molecules in the aggregate, an effect which to our knowledge has not been previously reported.     

Vibrational spectra and ab initio analysis of tert-butyl,trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene II. 3,3-Dimethyl-1,2-bis(trimethylsilyl)cyclopropene

The IR and Raman spectra of 3,3-dimethyl-1,2-bis(trimethylsilyl)cyclopropene (I) (synthesised using standard procedures) were measured in the liquid phase. Total geometry optimisation was performed at the HF/6-31G* level. The HF/6-31G*//HF/6-31G* quantum mechanical force field (QMFF) was calculated and used to determine the theoretical fundamental vibrational frequencies, their predicted IR intensities, Raman activities, and Raman depolarisation ratios. Using Pulay's scaling method and the theoretical molecular geometry, the QMFF of I was scaled by a set of scaling factors used previously for 3,3-dimethyl-1,2-bis(tert-butyl)cyclopropene (17 scale factors for a 105-dimensional problem). The scaled QMFF obtained was used to solve the vibrational problem. The quantum mechanical values of the Raman activities were converted to differential Raman cross sections. The figures for the experimental and theoretical Raman and IR spectra are presented. Assignments of the experimental vibrational spectra of I are given. They take into account the calculated potential energy distribution and the correlation between the estimations of the experimental IR and Raman intensities and Raman depolarisation ratios and the corresponding theoretical values (including Raman cross sections) calculated using the unscaled QMFF.     

Deuterium NMR of the TGBA* phase in chiral liquid crystals

A deuterium NMR (DNMR) study of the TGBA* (twist grain boundary smectic A*) phase in an NMR magnetic field of 9.4 T for the chiral compound 4-[4'-(1-methyl heptyloxy)] biphenyl 4-(10-undecenyloxy) benzoate (11EB1M7) is reported. The deuterium two-dimensional (2D) exchange spectra were observed for the first time in this phase. The present study allows us to learn how the helicoidal structures arrange in an external magnetic field. To derive quantitative kinetic parameters of this novel phase, both 1D and 2D experimental spectra were simulated by means of a jump diffusion model. By comparing the experimental and simulated spectra, an accurate determination of the dynamic parameters in the TGBA* phase was obtained. Furthermore, the twist angle between two neighboring smectic A blocks is found as 26 +/- 10 degrees, which is consistent with the X-ray results for similar chiral liquid crystals. The diffusion constant (D(parallel)) is estimated to be 3.2 x 10(-12) m(2)/s at 379.5 K.     

两种卟啉化合物在Ag溶胶表面的紫外-可见吸收光谱和表面增强拉曼散射光谱研究

表面增强拉曼散射(SERS)自1974年被Fleischmann等^[1]发现以来,日益受到人们的重视.通过SERS谱图分析,可以获得物质结构及其与基体作用的信息.由于SERS可使拉曼信号增强10⁵~10⁶倍^[2],并且在某些情况下银胶还能使表面吸附质的荧光猝灭^[3,4], SERS常用来检测一些普通拉曼光谱难以检测的样品和考察界面络合物的形成.     

Evidence of solvent-gelator interaction in sugar-based organogel studied by field-cycling NMR relaxometry

The dynamics of bulk toluene and toluene confined in the 1,2-O-(1-ethylpropylidene)-α-D-glucofuranose gel was studied using (1)H field-cycling nuclear magnetic resonance relaxometry. The proton spin-lattice relaxation time T(1) was measured as a function of the magnetic field strength and temperature. The observed dispersion in the frequency range 10(4)-10(6) Hz for the relaxation rate of toluene in the gel system give evidence of the interaction between the toluene and the gelator aggregates. The data were interpreted in terms of the two-fraction fast-exchange model. Additionally it was also shown that a cooling rate during gel preparation process influences the gel microstructure and leads to different gelator-solvent interactions as reflected in a different behavior of the proton spin-lattice relaxation rate of toluene within the gel observed at the low frequency range.