Spectroscopic determination of binding between human serum albumin and a platinum(II) dimethylsulfoxide complex

We have used electronic absorption and fluorescence spectroscopy to study binding between a platinum(II) dimethylsulfoxide complex (cis-[Pt(DMSO)₂Cl₂]) and human serum albumin (HSA), and the effect of complexation on the structure of the protein. We have calculated the binding parameters for binding between cis-[Pt(DMSO)₂Cl₂] and HSA. We have determined the binding constant K_B = (1.2 ± 0.1)·10³ M⁻¹ and the Hill coefficient h = 1.03 ± 0.1. We have determined that binding between cis-[Pt(DMSO)₂Cl₂] and the protein leads to a change in the internal packing of the macromolecule. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 573–576, July–August, 2008.     

Excited-state absorption in oxidized cytochrome c solution

Nonlinear absorption dynamics of oxidized cytochrome c in water solution was investigated at 532 nm with Z-scan and pump–probe techniques. The optical characterization of this compound is very important owing to its similarity with hematoporphyrin-based drugs commonly used in photodynamic therapy for cancer treatment. We observed a saturable absorption process related to the excited singlet population, followed by a fast decay to the ground state. The optical excitation and subsequent relaxation were interpreted with a three-energy-level diagram, allowing the first singlet excited-state absorption cross section and lifetime determination. PACS 42.65.Sf; 78.66.Qn; 42.62.Be     

Structural determination of a short-lived excited iron(II) complex by picosecond x-ray absorption spectroscopy

Structural changes of the iron(II)-tris-bipyridine ([Fe(II)(bpy)(3)](2+)) complex induced by ultrashort pulse excitation and population of its short-lived (< or =0.6 ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x-ray-absorption near-edge structure and extended x-ray-absorption fine structure spectroscopy features delivers an Fe-N bond elongation of 0.2 A in the quintet state compared to the singlet ground state.     

Hybrid light-emitting devices based on phosphorescent platinum(II) complex sensitized CdSe/ZnS quantum dots

We report on hybrid light-emitting devices based on the emission of phosphorescent sensitized colloidal CdSe/ZnS quantum dots (QDs). Emission lifetime measurements demonstrated that the energy transfer (ET) from square-planar platinum(II) complex [4-CF3-(NC^N^)PtC≡CC6H-4'-F] (NC^HN^=1, 5-bis(2'-pyridyl)benzene) (Pt-2) to QDs is more efficient than that from octahedral iridium(III) complex bis[(4,6-difluorophenyl)pyridinato-N, C2]-(picolinato)iridium (FIrpic). This different ET efficiency might be attributed to the different spatial structures between Pt-2 and FIrpic. Pure red emission with CIE coordinates of (0.66, 0.33) and maximum external quantum efficiency of 2.08% and white emission with power efficiency of 3.15 lm/W were realized at different concentrations of Pt-2 and QDs, respectively.     

Novel near-infrared photoluminescence from platinum(II)-porphyrin (PtOEP) aggregates

We investigated photoluminescence of the phosphorescent molecule platinum(II)-2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin. In neat films prepared by organic molecular beam deposition or precipitation from solution, we observe a near infrared emission feature around 1.65 eV, caused by aggregation effects.     

Investigation of polycrystalline copper(II) chloride-1.5-dimethyltetrazole complex compound with X-ray absorption spectroscopy

The polycrystalline copper(II) chloride-1.5-dimethyltetrazole (CuCl₂L, where L is 1.5-dimethyltetrazole) complex compound is investigated with the methods of extended x-ray absorption fine-structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy at the K absorption edge. The data on the complex structure are compared to the results of x-ray diffraction study.     

Photo-induced phase transitions probed by X-ray absorption spectroscopy: Fe(II) spin crossover complex

Photo-induced phase transitions in spin-crossover complex [Fe(II)(2-pic)₃]Cl₂EtOH were investigated by X-ray absorption spectroscopy (XAS) technique. In situ XAS results showed that the metal-ligand (Fe–N) bond distance expands by ca. 0.20 Å upon photo-induced (S=0→S=2) spin conversion. We find that nearly octahedral (O_h) symmetry of FeN₆ coordination remains in the photo-induced high spin state. The next-nearest neighbor Fe–C radial distribution shows a subtle change due to local distortions of ligand molecules. Inhomogeneous distribution of strains may disturb cooperative photo-induced phase transitions removing centers of inversion symmetry.     

丹参酮ⅡA及丹参酮ⅡA-Cu(Ⅱ)配合物的分子结构和电子吸收光谱研究

用ICCD瞬态光谱探测系统,检测了乙醇溶剂中丹参酮ⅡA及其与Cu(Ⅱ)形成的配合物的紫外-可见吸收光谱。采取密度泛函(DFT)方法优化几何构型,获得了丹参酮ⅡA及丹参酮ⅡA-Cu(Ⅱ)配合物的稳定几何结构。在此基础上,运用含时密度泛函(TD-DFT)方法,计算了丹参酮ⅡA及丹参酮ⅡA-Cu(Ⅱ)配合物的气相和乙醇溶剂(PCM)中的电子吸收光谱。结果表明,乙醇溶剂效应使丹参酮ⅡA的吸收光谱红移,配合物的吸收光谱蓝移。计算得到的溶液相丹参酮ⅡA及丹参酮ⅡA-Cu(Ⅱ)配合物电子吸收光谱与实验测量光谱符合较好。本文首次测量和计算得到了丹参酮ⅡA与Cu(Ⅱ)形成的配合物的电子吸收光谱。     

Electrical performance of a Ni(II) complex polymer

The I–V characteristics taken of thin films of the oxidized and reduced forms of poly[Ni(Salen)] metallopolymer are studied. The data obtained indicate that states localized in the volume may experience thermofield ionization. It is found that the electroactivity of the oxidized form of the polymer is higher. The parameters of the thermally activated mechanism of charge transfer are determined.     

Electrical and optical anomalies in one-dimensional BIS (dimethylglyoximato) platinum (II) at high pressure

The electrical resistivity, the absorption spectrum and the X-ray diffraction for Pt(dmg)₂ have been studied at high pressures. The resistivity decreased rapidly up to about 6.7 Gpa. Above this pressure it slightly increased with increasing pressure. The estimated resistivity at the resistance minimum was 0.05 Ω.cm. A new pressure induced absorption band at around 540 nm was observed at about 6.5 Gpa. The Pt-Pt distance at the pressure is equal to that of KCP. An origin of both anomalies in Pt (dmg)₂ at around 6.5 Gpa will be discussed.     

Interaction with DNA of the novel cationic complex (2, 2′: 6′, 2″-terpyridine)methyl platinum(II)

Summary The planarity and electron delocalization of the 2, 2′:6′, 2″-terpyridine (terpy) moiety in salts of the type [Pt(terpy)Me]X leads to extensive stacking interactions in aqueous solution. UV/VIS,¹H NMR and resonance light scattering spectra provide evidence for the tendency of the complex to form large aggregates even under low ionic strength conditions. The interaction of the cationic complex with calf thymus DNA was investigated by spectroscopic techniques and mobility assays. At highr _f ratios the complex seems to form extended aggregates on the surface of the nucleic acid but at lowerr _f evidence was obtained for intercalation. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Excited-state absorption of Co2+ in MgF2 and KZnF3

We report on measurements of excited-state absorption spectra and absolute cross-sections in Co²⁺-doped KZnF₃ and MgF₂ at room temperature in the near-infrared domain. The data are compared with the predictions of the single-configuration co-ordinate model.     

Electronic states and phosphorescence of dendron functionalized platinum(II) acetylides

The photophysical properties of bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine) platinum(II) with 2,2-bis(methylol)propionic acid (bis-MPA) dendritic substituents were studied. The fluorescence emission decay upon excitation in the UV (typically 350-380 nm) was rapid, in the order of 1 ns or shorter. In oxygen-saturated tetrahydrofuran solvent, the phosphorescence decay time was in the order of 200 ns. Bright phosphorescence at 530 nm was found for dendrimers under certain conditions. The associated phosphorescence decay time considerably increased to above 100-200 μs at higher concentrations (30-100 μM), and in oxygen-evacuated samples. Thus, it was clarified that the strongest triplet quenching was caused by oxygen dissolved in the sample, since it was possible to reversibly go between the bright and quenched phosphorescent state by freeze-thaw pumping cycles. The bright phosphorescence formed spontaneously for the cases with the larger dendritic substituents is implying a chromophore protecting effect. From time-dependent density functional calculations, the electronic structure of a few low-lying singlet and triplet states are discussed. A new mechanism for efficient triplet state formation and phosphorescence of Pt-ethynyls is proposed. Here, a fast relaxation via internal conversion takes the excited population of the dominant π→π* excitation into a lower singlet state of ligand-to-metal charge transfer character of πσ* type. This allows an efficient inter system crossing to the triplet state manifold.     

ESR spectral studies of a Cu(II) salicylidene tyrosine complex

A novel Schiff base derived from salicylidene and tyrosine and its copper(II) complex have been synthesized and characterized. The composition of the complex is K[CuL(Ac)] · H₂O, where L = H₁₃C₁₆NO₄. Electron spin resonance (ESR) spectra of the copper(II) complex were investigated at different temperatures and in various solvents. The second-order effect and the relaxation effect were observed in the solution spectrum at room temperature and satisfactorily explained by the spin Hamiltonian. The bonding parameters of the Cu(II) complex were calculated with spectral parameters from ESR spectra at low temperature. Its bonding characterization and stability were discussed. The result shows that both the in-plane σ-bond and the in-plane π-bond in the complex play an important role.     

Far ultra-violet absorption bands of osmium (IV), iridium (IV), platinum (IV) hexahalides

The gas phase electron resonance spectrum of SeO in its ³Σ and ¹Δ states has been studied. Values of the rotational constant B ₀ and ‘spin-spin’ splitting parameter λ in the ³Σ state, previously determined from the ultraviolet spectrum, are shown to be consistent with the electron resonance results, and we are also able to estimate the spin-rotation interaction constant. In addition, the ³Σ spectrum shows ⁷⁷Se hyperfine structure. The ¹Δ spectrum yields values for the rotational constant (and hence bond length) and rotational g factor.