Spectral and kinetic properties of an immunoactive 8-azasteroid and a product of its photochemical transformation in aqueous solutions

The spectral and kinetic properties of an immunoactive 8-azasteroid and a product of its photochemical transformation are studied by the methods of steady-state and transient spectroscopy. It is found that the spectral features of the studied compounds in solvents of different nature are determined by a high sensitivity of the electronic structure of the aminovinyldicarbonyl fragment to intermolecular interactions of the donor-acceptor type. This leads to the existence in solutions of several mesomeric-tautomeric forms that are in a dynamic equilibrium controlled by the experimental conditions. Based on the analysis of the dynamics of the transient spectra of induced absorption and of the spectral and luminescent properties of the extracted photoproduct, the conclusion is made on the direction of the photochemical transformation of 2,3-dimethoxy-8-azagona-1,3,5(10),13-tetraene-12,17-dione and the final product is identified as 6,7-dehydroderivative of the parent compound.     

1-氯甲基-6,7-二甲氧基-1,2,3,4-四氢异喹啉盐酸盐的合成和结构表征

以3,4-二甲氧基苯乙胺为原料,经酰化,比西勒-纳皮拉尔斯基（Bischler-Napieralski）反应,还原,盐酸成盐合成1-氯甲基-6,7-二甲氧基-1,2,3,4-四氢异喹啉盐酸盐,总收率41.1%。目标物及中间体经IR,1H NMR进行结构表征。     

Elementary sequential spectral line and statistical properties of the thermal reservoir of free polyatomic molecules

The formation of vibronic spectra of free polyatomic molecules is studied by taking the concept of sequences as constituent elements of vibronic bands. Statistical properties of the thermal reservoir of oscillators, which randomly perturbs optically active transitions in a polyatomic molecule, are considered. The spectral shape, position, and width of the elementary sequential lines (ESL) are determined. It is shown that the ESLs have a Lorentzian shape if the perturbations are short-term and the pulse shape is symmetric about its origin. The position of the ESLs depends on the total vibrational energy of the thermal reservoir of oscillators in the initial electronic state of a molecule. The analysis of the statistical properties of the thermal reservoir of polyatomic molecules shows that one should distinguish between the ESL linewidth of individual molecules and the ESL linewidth averaged over the entire thermal ensemble. It is shown that individual molecules of the thermal ensemble that have different total vibrational energies are characterized by different widths of the ESLs. Consequently, the exchange and redistribution dynamics of the vibrational energy stored in the initial electronic state should manifest itself in the difference between the single-molecule ESL widths measured at different instants in time.     

1-氨甲基-6,7-二甲氧基-1,2,3,4-四氢异喹啉盐酸盐的合成及表征

以3,4-二甲氧基苯乙胺为原料,经氯乙酰氯酰化得到N-氯乙酰基-3,4-二甲氧基苯乙胺,通过与邻苯二甲酰亚胺钾烃化,在P2O5的作用下经Bischler-Napieralski环合后,用水合肼肼解,硼氢化钾还原后与盐酸作用得1-氨甲基-6,7-二甲氧基-1,2,3,4-四氢异喹啉盐酸盐。产品结构经IR、1H NMR、MS确证。     

Spectral and luminescent properties of 2,3-dimethoxy-8-aza-D-homogona-1,3,5(10),13-tetraene-12,17a-dione and its Δ9,11 derivative

The spectral and luminescent properties of compounds from the class of immunoactive 8-azaster-oids, 2,3-dimethoxy-8-aza-D-homogona-1,3,5(10),13-tetraene-12,17a-dione and its 9,11 dehydroderivative, are studied by the methods of steady-state spectroscopy. It is found that the specific features of the fluorescent properties of the compounds under investigation in different solvents are determined by a high sensitivity of their electronic structure to intermolecular interactions of the donor-acceptor type. This leads to the existence in solutions of several mesomeric-tautomeric forms that are in a dynamic equilibrium controlled by the experimental conditions. A photoproduct that is responsible to a large extent for the fluorescent properties of solutions of aminovinyldicarbonyl 8-azasteroids is not a 9,11 dehydroderivative of the initial compounds.     

Photochemical Processes in Aqueous Solutions of Immunoactive 8-Azasteroid

Based on an analysis of the absorption, fluorescence excitation, and fluorescence spectra, and the duration of the excited states of an aqueous solution (pH 7.4) of 2,3-dimethoxy-8-azagona-1,3,5(10),13-tetraen-12,17-dione molecules, the existence of two centers emitting longwave (L centers) and shortwave (S centers) fluorescence has been established. Irradiation of the solution accelerates the accumulation of L centers and considerably reduces the quantity of S centers that represent the initial molecule. Analysis of the induced-absorption spectra and their kinetics with picosecond time resolution shows that ionization of the molecule studied is the initial photochemical act and formation of a dehydro derivative of the initial molecule or protonation of carbonyl groups is the next act.     

Spectral-luminescent and proton-acceptor properties of 9-11-dehydrogenated 8-azasteroid

Methods of quantum chemistry (including the method of intermediate neglect of differential overlap (INDO)) are used to calculate and to interpret the absorption and fluorescence spectra of the 9-11-dehydroderivative 2,3-dimethoxy-8-aza-D-homogon-1,3,5(10),13-tetraene-12,17a-dion (DA-1) molecule in aproton and proton-donor solvents. The electronic structure and spectra of electronically excited states of the isolated molecule and its complexes with water and proton solvates are calculated. It is demonstrated that bands in the absorption spectra are complex; they are formed by two or more electron transitions. It is established that only the charged DA-1 + H ₅ O ₂ ⁺ and DA-1 + 2H ₃ O ⁺ complexes can fluoresce. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 3–9, June, 2006.     

Investigation of photoprocesses in complex molecular systems (macroheterocycles)

Spectral properties and photophysical processes in two macroheterocycles consisting of two pairs of chemically bound fluorophors 1-(3,4-dicyanophenyl)-benzotriazole and 9,10-bis (4-aminophenyl)-anthracene (MI) and 1-(3,4- dicyanophenyl)-benzotriazole and rhodamine (MII) are examined by quantum-chemical and experimental methods. It is demonstrated that macroheterocycles are not bifluorophor molecules in classical understanding by virtue of their unique structure. All processes of electronic excitation energy deactivation in such systems proceed as in a single molecule, and electronic states in them are common with different relative contributions of molecular orbitals belonging to donor and acceptor fragments. The presence of identical fragments results in splitting of electronic states with the forbidden lower state from which the fluorescence is improbable.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 13–18, October, 2004.     

Fabrication of the stable adduct CdS/CTAB/Clay with sandwich-like nanostructures

The ordered multilayer adducts have been synthesized by electrostatic self-assembly between exfoliated sodium montmorillonite nanoplatelets and substituted CdS/CTAB cationic polyelectrolytes, in which sodium montmorillonite particles are exfoliated by means of extensive swelling and CdS/CTAB polyelectrolytes are obtained by sonicating CdS nanoparticles in CTAB water suspension. The build-up of the stable adducts with sandwich-like nanostructures has been demonstrated by X-ray diffraction (XRD) pattern. TEM cross-sectional images indicate that the nanocomposites are aligned parallel to form ordered structures. And UV–Vis and PL spectra show the presence of the inorganic functional components. It may be predicted that this self-assembly technique can be generalized to prepare other sandwich-like nanocomposites with desired optical, electro-optical, electronic, catalytic and magnetic properties.     

Carrier--envelope phase effects for a dipolar molecule interacting with ultrashort laser pulse

In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell--Bloch equations. The electronic properties of dipolar molecule 4-trans-[p-(N, N-Di-n-butylamino)-p -stilbenylvinyl] pyridine (DBASVP) molecule, one-dimensional asymmetric organic molecule, is calculated by density functional theory at \textit{ab initio} level. The numerical results show that the carrier propagation and the spectrum evolution of the pulse are sensitive to its initial phase and the phase sensitivity is more obvious for larger area pulse. The phase-dependent feature is more evident in dipolar molecule because the permanent dipole moment makes the nonlinear effects stronger.     

First-principles study of the electronic transport properties of the anthraquinone-based molecular switch

By applying non-equilibrium Green’s function (NEGF) formalism combined with first-principles density functional theory (DFT), we have investigated the electronic transport properties of the anthraquinone-based molecular switch. The molecule that comprises the switch can be converted between the hydroquinone (HQ) and anthraquinone (AQ) forms via redox reactions. The transmission spectra of these two forms are remarkably distinctive. Our results show that the current through the HQ form is significantly larger than that through the AQ form, which suggests that this system has attractive potential application in future molecular switch technology.     

1,3-diphenyltriazene as a possible optical molecular switch: A first-principles study

By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of a 1,3-diphenyltriazene-based optical molecular switch. The molecule that comprises the switch can convert between the cis and the trans forms upon photoexcitation. The transmission spectra of two forms are remarkably distinctive. Theoretical results show that the current through the trans form is significantly larger than that through the cis form, which suggests that this system has attractive potential application in future molecular switch technology.     

Investigation of the octaethylporphin cationic forms in a silicate gel matrix by methods of low-temperature site selective spectroscopy

The spectral-luminescent properties of an octaethylporphin-doped inorganic xerogel prepared from tetraethoxysilane by the sol-gel method have been investigated. With the help of selective excitation and selective monitoring of fluorescence, it has been established that the octaethylporphin molecules, on their embedment into the gel matrix, form two cationic forms, dicationic and monocationic; the longest wavelength absorption band of the latter is shifted to the red. The significant influence of the gel matrix on the energy of the excited electronic Q states (S₁ and S₂) is shown. By the fluorescence line narrowing method at 4.2 K, fine-structure fluorescence and fluorescence excitation spectra of both forms have been obtained; the frequencies of the normal modes in the S₀ and S₁ states have been determined. The data on vibrational frequencies are interpreted on the basis of their juxtaposition with those from the fluorescence line narrowing spectrum of octaethylporphin and resonance Raman spectra of its complexes with copper and nickel. Cases of the appearance of out-of-plane vibrations in the fluorescence spectra have been revealed; their activation is explained by the nonplanarity of the porphyrin macrocycle for the cationic forms.     

Synthesis and photoinduced electron transfer characteristic of a bis (zinc porphyrin)‐perylene bisimide array

In this article, a donor–acceptor array consisting of two zinc porphyrin (ZnPOR) units attached to the 1,7‐positions of perylene‐3,4:9,10‐bis(dicarboximide) (PDI) was synthesized and characterized. This double‐wing molecule exhibits very broad absorption in the region from 300 to 900 nm. Especially, its lower energy absorption feature presumably arises from donor–acceptor interactions. The fluorescence emission spectra confirmed that photoinduced electron transfer occurred from POR to perylene bisimide moiety in this triad. In contrast to previously studied systems incorporating POR and PDI groups, this array shows the evidence of a relatively strong ground‐state electronic coupling between the donor and acceptor moieties. Additionally, highest occupied molecular orbital and lowest unoccupied molecular orbital values of the array were acquired by cyclic voltammetry (CV). The results showed that these energy values fulfill the energetic conditions required for the proposed electron transfer. More importantly, the photocurrent measurement showed that this molecule exhibits a high capacity to form a photoinduced charge‐separated state and to produce steady and prompt cathodic photocurrent responses. These results confirmed the role of this new array toward harvesting light energy and generating photocurrent during the operation of a photoelectrochemical cell. Copyright © 2011 John Wiley & Sons, Ltd.     

TEMPO及其衍生物充放电过程中电子得失理论特性

在(U)B3LYP/6-31G(d,p)或6-31+G(d,p)基组水平上用密度泛函方法对2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)及其阳离子衍生物在充放电过程中的电子结构和相关性质进行了理论研究. 结果表明在充放电过程中取代基对物质的电子结构和相关性质变化起着重要作用. TEMPO得电子后以单线态存在形式更稳定而阳离子衍生物却以三线态存在形式更稳定. 对TEMPO而言,无论是充电过程还是放电过程对自由基端的N和O的电子特性都有很大影响;对阳离子衍生物而言,放电过程主要影响吡啶端而充电过程主要影响自由基端的变化. 溶剂作用对自由基端的某些键长与电荷分布具有一定影响. 另外,用TDDFT方法对TEMPO及衍生物的紫外吸收光谱进行了计算和模拟,结果与实验数据吻合.     

Comparison of the Optoelectronic Performance of Neutral and Cationic Forms of Riboflavin

The riboflavin dye 2,3,4,5-tetra-O-acetyl-1-[3-(6-bromohexyl)-7,8-dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl]-1-deoxypentitol and its pyridinium salt were synthesized, and studied by absorption and fluorescence spectroscopy in solutions and on thin film states. The first absorption band of riboflavin-pyridinium salt derivative is red-shifted by 10 nm compared to neutral one on film. Cationic riboflavin derivative shows significant wavelength changes on its fluorescence emission spectrum in the excited state depending on the solvent polarity and the electronic environment. The fluorescence quantum yields of cationic riboflavin gave much higher values as compared to that of its neutral form. The fluorescence lifetimes were found to be in the range of 5.5–6.6 ns with mono ? exponential behavior. These dyes possess low-lying HOMO energy levels which are suitable to be able to inject holes to donor polymers so that they can be used as acceptor component in the active layer of bulk heterojunction solar cells (BHJ-SCs). Photovoltaic responses are reported for P3HT:riboflavin active layer wherein the synthesized dyes are used as acceptor component. Also, neutral riboflavin shows greater electron mobility value of 1.3 × 10^?3 cm²/V?s compared to its cationic derivative.     

线性多烯分子的共振拉曼光谱

线性多烯分子是重要的光电材料,它还具有光采集、 光防护、 防癌、 抗癌功能,也是物理学、 化学理论研究的理想分子。 共振拉曼光谱是研究线性多烯分子最有力的工具。 本文总结了线性多烯分子共振拉曼光谱的特征及其与分子结构的关系,包括：电子光谱(紫外-可见吸收光谱)、 拉曼光谱的性质及与外场的关系;电子能隙对碳碳原子振动的调制作用;给出几个实验结果：温度降低、 溶剂密度增加、 溶液浓度降低等会使线性多烯分子结构有序增加,π电子能隙减小,使紫外-可见吸收光谱红移;π电子离域扩展,有效共轭长度增加,拉曼活性提高,拉曼光谱红移,拉曼截面增加。 振幅模型是研究线性多烯分子较理想的模型。     

Solvatochromism and solvatofluorochromism of the intramolecular charge transfer band of 4-dimethylaminochalcone in the electronic spectra of its solutions

The solvatochromic and solvatofluorochromic dependences pertaining to the intense intramolecular charge transfer electronic band of the 4-dimethylaminochalcone molecule, widely used as an efficient spectralluminescent probe in various medical and biological studies, are systematically and quantitatively investigated. The data obtained are interpreted based on the new variant of the semiempirical theory of the influence of the dielectric properties of individual solvents on the shift in the optical spectra of molecules occurring as a result of the gas-solution phase transition that was proposed previously by one of the authors of this study. It is shown that the main contribution (at least 70–80%) to the absolute solvation shift in the absorption and fluorescence spectra of the 4-dimethylaminochalcone molecule is made by universal dipole-dipole interactions of orientation, induction, dispersion, and inductive-resonance nature, as well as by repulsive forces.     

超声分子束中中性态和离子态吡咯烷的红外光谱

本文应用真空紫外光电离结合红外光解离以及飞行时间质谱技术获得超声分子束中吡咯烷单体在中性态和离子态的红外光谱. 研究发现,吡咯烷在中性态和离子态的CH伸缩振动均有不同程度的红移现象. 在中性态吡咯烷中,由于NH的电偶极矩较小,没有观察到NH伸缩振动峰. 而电离后的吡咯烷NH伸缩振动峰有很大的增强,并与其他实验相比出现红移现象. 通过理论计算发现中性态和离子态的CH伸缩振动的红移分别是由反超共轭和正超共轭现象引起的. 而NH峰的增强和红移则是由于N原子上的电子被电离所引起的. 通过计算分子的气态酸碱度发现,在离子态中,CH的酸性比NH的酸性略强.     

Spectroscopic Studies of Intra- and Inter-Molecular Hydrogen Bonding of Some O-Hydroxylbenzenesulfonanilides in Solutions

The effect of solvent on the electronic spectra of some fasciolici-dal o–-hydroxylbenzenesulfonanilides is examined and discussed. It is revealed that in solution these compounds exist in both intramolecular hydrogen bond form and intermolecular hydrogen bond form occurring between solute and solvent molecule. In solutions containing large amount of apolar aprotic solvents such as dioxane, compounds studied are mainly intramolecular hydrogen bond form and exhibit a weak transition band which is presumably attributed to the transition of n-electrons of oxygen atom in the intramolecular hydrogen bonded six-membered ring of the compounds.