A photo-induced redox reaction by visible light via a charge transfer complex

The reduction of tropylium cation (Tr⁺) with the concomitant oxidation of O,O′-dialkyldithiophosphate anions (dtp^?) have been achieved by visible irradiation of their acetonitrile solution in presence of a bipyridinium dication ; the later via its charge transfer complex with dtp^? acts as a light-harvest and as an electron relay.     

A rational approach to emission ratio enhancement of chemodosimeters via regulation of intramolecular charge transfer

The sensitivity as well as dynamic range of a ratiometric probe is determined by the ratio of emission intensities at two wavelengths. Thus, it is highly desirable to acquire a large ratiometric fluorescence response at two wavelengths. However, ratiometric fluorescent signals are intrinsic characteristics of the particular probe-analyte interactions. The design for fluorescent probes with a large ratiometric signal remains a challenging task. There is still a lack of a proper approach to enhance the ratiometric fluorescence response for fluorescent chemodosimeters. Herein, we introduced a novel strategy to increase the emission ratios of a chemodosimeter via modulation of intramolecular charge transfer.     

氨基酸-多金属氧酸盐电荷转移配合物的固相法合成及表征

多金属氧酸盐是一类纳米级金属-氧多核配合物,可通过变换抗衡阳离子、杂原子、配原子等方法从原子、分子水平上进行物理或化学修饰,与不同的有机分子结合后可以获得具有特定功能和性质的化合物.     

A study on vinyl polymerization initiated by a charge transfer complex

The mechanism of polymerization of methyl methacrylate initiated by a new charge transfer complex system of N,N-dimethylaniline-p-toluene sulphonyl chloride in acetonitrile medium at 50°C is reported.     

Excited-state charge coupled proton transfer reaction via the dipolar functionality of salicylideneaniline

Based on design and synthesis of salicylideneaniline derivatives(1a-1d),we demonstrate a prototypical system to investigate the excited-state intramolecular charge transfer(ESICT) coupled excited-state intramolecular proton transfer(ESIPT) reaction via the dipolar functionality of the molecular framework. In solid and aprotic solvents 1a-1d exist mainly as E conformers that possess an intramolecular sixmembered -ring hydrogen bond.Compounds 1a-1c exhibit a unique proton-transfer tautomer emission, while compound 1d exhibits remarkable dual emission due to the different solvent-polarity environment between ESICT and ESIPT states.Time-dependent density functional theory(TDDFT) calculations are reported on these Schiff bases in order to rationalize their electronic structure and absorption spectra.     

Metal atom dynamics in a charge transfer complex

Temperature-dependent ⁵⁷Fe Mössbauer spectroscopy over the interval 89 < T < 335 K has been used to study the detailed metal atom dynamics in the charge transfer complex (CT) decamethlferrocene-acenaphthenequinone. The quadrupole splitting, area ratio and recoil-free fraction parameters clearly reflect the phase transition (T_pt) at 257 K. The root-mean-square-amplitude of vibrations of the metal atom in the CT complex have been compared to that determined earlier for decamethyl ferrocene. The vibrational amplitudes are isotropic below T_pt but anisotropic above this temperature.     

A catalyst-and solvent-free multicomponent synthesis of 7-azagramine analogues via a Mannich type reaction

A catalyst-and solvent-free protocol for the synthesis of 7-azagramine analogues is described via a three-component Mannich type reaction between 7-azaindole, aromatic aldehydes and heterocyclic amines in acceptable to excellent yields. Structures of the compounds were confirmed satisfactorily by ¹H NMR, IR, mass, TOCSY, HSQC and HMBC spectral analyses.     

A novel group transfer polymerization of 1-trimethylsiloxy-benzocyclobutene via hetero Diels-Alder reaction

A novel group transfer polymerization via hetero-Diels-Alder reaction is described. When 1-trimethylsiloxybenzocyclobutene ( 1 ) was treated with a catalytic amount of p-anisaldehyde (4-methoxybenzaldehyde) and TASF (tris(dimethylamino)sulfonium difluorotrimethylsilanide) at room temperature for 0.5 h, poly[1,2-phenylene-1-(trimethylsiloxy)ethylene] was obtained quantitatively. The number-average molecular weight of the polymer was M̄_n = 2000 and the molecular weight distribution was narrow (ratio of weight-to number-average molecular weights M̄_w/M̄_n = 1.18). Structural characteristics suggested a polymerization mechanism involving isomerization of 1 to o-quinodimethane and successive hetero-Diels-Alder reaction leading to poly[1,2-phenylene-1-trimethylsiloxy ethylene]. The living-like nature of the polymerization was supported by a monomer addition experiment in which the molecular weight increased according to the increase of the added monomer.     

A one-pot three-component reaction to access 1-alkyl-2-aryl-5-nitrobenzimidazoles under solvent-free conditions

A novel and expeditious method to access 1-alkyl-2-aryl-5-nitrobenzimidazoles has been developed. Enlisting solvent-free conditions, 2-fluoro-5-nitroaniline, a primary amine, and substituted aldehyde were melted together in one-pot to generate a variety of 1-alkyl-2-aryl-5-nitrobenzimidazoles.     

Organic-salt-mediated highly regioselective N3-alkylation of 2-thiophenytoin via Michael reaction under solvent-free conditions

A regioselective N3-alkylation of 5,5-diphenyl-2-thiohydantoin (2-thiophenytoin) using a very efficient mild base K₂CO₃ and α,β-unsaturated esters in the presence of organic salt TBAB (tetrabutylammonium bromide) at room temperature has been reported (3b–3h). The selectivity of this reaction is excellent and products have been produced in good yields under solvent-free conditions. The increase of the reaction temperature to 70°C mostly disappeared this selectivity and afforded only the N1,N3-dialkylated derivatives of 2-thiophenytoin in good yields (4b–4g). We were unable to selectively N3-alkylate 2-thiophenytoin with ethyl acrylate at both room temperature and 70°C under the same conditions (4a). Dimethyl and diethyl fumarates cannot work as Michael acceptors and were hydrolyzed to fumaric acid under reaction conditions.     

荷移分光光度法测定酒石酸美托洛尔

研究了酒石酸美托洛尔与紫色素之间的荷移反应。确定了反应条件,建立了一种测定酒石酸美托洛尔的荷移分光光度法。酒石酸美托洛尔与紫色素在乙醇介质中,室温条件下即可形成稳定的1∶1型荷移络合物,该络合物的最大吸收波长为540 nm,表观摩尔吸光率为6.83×103L.mol-1.cm-1。酒石酸美托洛尔质量浓度在10~80 mg/L范围内服从比耳定律,相关系数为0.9991。相对标准偏差为1.3%(n=11),回收率为99.3%~102.7%。     

Synthesis of five- and six-membered lactams via solvent-free microwave Ugi reaction

Five- and six-membered lactams were synthesized via a 4-center 3-component Ugi reaction by combining amines, isocyanides, and ketoacids under solvent-free microwave conditions. The reaction was carried out in much shorter times and the yields were improved in comparison to classical conditions.     

Synthesis of 3-aminoisoxazolmethylnaphthols via one-pot three-component reaction under solvent-free conditions

A one-pot three-component condensation reaction of 3-amino-5-methylisoxazole, aryl aldehyde and 2-naphthol to afford the corresponding 3-amino isoxazolmethylnaphthols in good to excellent yields. The remarkable features of this new procedure are high conversions, clean reaction condition, short reaction time, nonhazardous and environmentally friendly reaction condition, inexpensive and easily commercially availability of the catalyst and simple work-up procedures.     

Structural and magnetic properties of a novel ferrocenyl-diiodine charge transfer complex

The reaction of 4-ferrocenyl-1,3-dithiole-2-thione with diiodine affords an unprecedented "double" charge-transfer complex; the highly ordered ferrocenium units are held by a supramolecular polyiodide chain, and the material shows evidence of the formation of zigzag magnetic chains below 2 K.     

Tetracycline sensitizes TiO2 for visible light photocatalytic degradation via ligand-to-metal charge transfer

Treatment of antibiotics contaminated water remains a global environmental challenge. In this study, tetracycline (TC) was found to effectively sensitize pure TiO₂ for visible light photocatalytic degradation via a ligand-to-metal charge transfer mechanism. The sensitization was attributed to the formation of TC-TiO₂ complex and the overlap of the molecular orbitals of TC and the conduction band of TiO₂. The intermediate degradation products of TC, however, did not sensitize TiO₂, which was the reason for the low mineralization rate. Nevertheless, our results showed that the intermediate degradation products of TC had significantly reduced bactericidal effects and less induction of antibiotic-resistance genes (ARGs). This study showcases an effective treatment of antibiotics-containing wastewater using the most common photocatalyst TiO₂ with reduced risk in the spread of ARGs.     

A schematic model for energy and charge transfer in the chlorophyll complex

A theory for simultaneous charge and energy transfer in the carotenoid-chlorophyll-a complex is presented here and discussed. The observed charge transfer process in these chloroplast complexes is reasonably explained in terms of this theory. In addition, the process leads to a mechanism to drive an electron in a lower to a higher-energy state, thus providing a mechanism for the ejection of the electron to a nearby molecule (chlorophyll) or into the environment. The observed lifetimes of the electronically excited states are in accord/agreement with the investigations of Sundstr?m et al. and are in the range of pico-seconds and less. The change in electronic charge distribution in internuclear space as the system undergoes an electronic transition to a higher-energy state could, under appropriate physical conditions, lead to oscillating dipoles capable of transmitting energy from the carotenoid-chlorophylls chromophore to the reaction center by sending an electromagnetic wave (a photon) which provides a novel new mechanism for energy production. In the simplest version of the F?rster?CDexter theory, the excitation energy of a donor is transferred to an acceptor and then de-excited to the ground state by fluorescence with no electron being transferred. In the process proposed herein, charge and energy both are transferred from donor to acceptor which can further de-excite by fluorescence. The charge transfer time scale involving an actual transfer of electron is in the pico-second range.     

A solvent-free protocol for the synthesis of 3-formyl-2H-chromenes via domino oxa Michael/aldol reaction

A new solvent-free, TBD-catalyzed protocol for the synthesis of 3-formyl-2H-chromenes is presented. Substituted salicylaldehydes 1 and 3-methyl-2-butenal 2 in the presence of 10 mol % of TBD underwent a domino oxa Michael/aldol reaction to effectively yield the corresponding 2H-chromene derivatives 3. The methodology represents an improvement either in terms of efficiency and sustainability as a small amount of catalyst is required and the work-up procedure is simple and straightforward.     

A novel spectrophotometric determination of trace copper based on charge transfer complex

A new type of colored complex, the charge transfer complex, was used to develop the spectrophotometric determination of copper. The method was based on the formation of a colored product, the charge transfer complex of copper substituted tungstophosphate with 3,3',5,5'-tetramethybenzidine (TMB), which was stabilized and sensitized by the addition of polyvinyl alcohol (PVA) in aqueous solution. The structure of copper substituted tungstophosphate was Keggin-type according to the results of infrared (IR) spectra. The optimum reaction conditions and other important analytic parameters had been investigated. Beer's law was obeyed in the copper(II) concentration range of 0.003-0.1 microg mL(-1), and the molar absorptivity at 660 nm is 2.54 x 10(5) L mol(-1) cm(-1). The proposed method was simple, selective, and sensitive. It was applied to the analytic samples with satisfactory results.