Synthesis and different substituent effects on spectral and electrochemical properties of porphyrin nicotinic acid binary compounds

The porphyrin nicotinic acid binary compounds with different substituents in porphine rings (5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-triphenylporhyrin 2a, 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-chlorophenyl)porphyrin 2b and 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-methoxyphenyl)porphyrin 2c) were synthesized. All of them have been characterized, assigned and analyzed by UV–vis, IR, MS and ¹H NMR spectra. Their electrochemical and spectroscopic properties were studied by using cyclic voltammetry, fluorescence spectra and Resonance Raman spectra. Different substituents have a little influence on electrochemical behavior and fluorescence spectra. In the Resonance Raman spectra, the substituent has little influence on the skeleton vibration of porphyrin and has much influence on the vibration of phenyl.     

The synthesis,X-ray crystal structure and optical properties of novel 1,3,5-triaryl pyrazoline derivatives

A series of novel 1,3,5-triaryl pyrazoline derivatives has been synthesized by the reaction of chalcone and 3-chloro-6-hydrazinylpyridazine in 47–82% yields. The structures of compounds obtained were determined by IR, ¹H NMR and HRMS spectra. Representatively, the spatial structure of compound 3d was determined by using X-ray diffraction analysis. Absorption and fluorescence spectral characteristics of the compounds were investigated in CHCl₃ by UV–vis absorption and emission spectra. The results showed that the absorption maxima of the compounds vary from 332 to 342 nm depending on the group bonded to benzene rings. The maximum emission spectra of compounds in CHCl₃ are dependent on groups in benzene ring in which a strong electron-donating group in benzene ring such as methoxyl group on C3 position of pyrazoline made the emission wavelength of 3e, 3f and 3g red shifted than that of compounds 3b, 3c and 3d with chlorine group. The intensity of absorption and fluorescence was also correlated with substituent on two aryl rings. In addition, the absorption spectra of these compounds change very little with increasing solvent polarity.     

Design and characterization of two-dye and three-dye binary fluorescent probes for mRNA detection

We report the design, synthesis, and characterization of binary oligonucleotide probes for mRNA detection. The probes were designed to avoid common problems found in standard binary probes such as direct excitation of the acceptor fluorophore and overlap between the donor and acceptor emission spectra. Two different probes were constructed that contained an array of either two or three dyes and were characterized using steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and fluorescence depolarization measurements. The three-dye binary probe (BP-3d) consists of a Fam fluorophore which acts as a donor, collecting light and transferring it as energy to Tamra, which subsequently transfers energy to Cy5 when the two probes are hybridized to mRNA. This design allows the use of 488 nm excitation, which avoids the direct excitation of Cy5 and at the same time provides a good fluorescence resonance energy transfer (FRET) efficiency. The two-dye binary probe system (BP-2d) was constructed with Alexa488 and Cy5 fluorophores. Although the overlap between the fluorescence of Alexa488 and the absorption of Cy5 is relatively low, FRET still occurs due to their close physical proximity when the probes are hybridized to mRNA. This framework also decreases the direct excitation of Cy5 and reduces the fluorescence overlap between the donor and the acceptor. Picosecond time-resolved spectroscopy showed a reduction in the fluorescence lifetime of donor fluorophores after the formation of the hybrid between the probes and target mRNA. Interestingly, BP-2d in the presence of mRNA shows a slow rise in the fluorescence decay of Cy5 due to a relatively slow FRET rate, which together with the reduction in the Alexa488 lifetime provides a way to improve the signal to background ratio using time-resolved fluorescence spectra (TRES). In addition, fluorescence depolarization measurements showed complete depolarization of the acceptor dyes (Cy5) for both BP-3d (due to sequential FRET steps) and BP-2d (due to the relatively low FRET rate) in the presence of the mRNA target.     

Effects of substituents on silicon atoms upon absorption and fluorescence properties of 1,3,6,8-tetrakis(silylethynyl)pyrenes

Synthesis, UV–vis absorption, and fluorescence spectroscopic properties of 1,3,6,8-tetrakis(silylethynyl)pyrenes 2–10 were studied. Absorption maxima of CH₂Cl₂ solutions of these compounds appeared at 437–445?nm, and molar absorption coefficients (ε) of most of these compounds exceeded 10⁵?L?mol^?1?cm^?1. Fluorescence emissions measured in dilute CH₂Cl₂ solutions are observed in visible region, and their intensities remarkably increased compared with that of pyrene. Fluorescence spectra obtained from concentrated CH₂Cl₂ solutions exhibited broad excimer emissions when steric bulk of substituents on silicon atoms is sufficiently low. Molecular orbital calculations indicated that HOMO-LUMO energy gap decreased with increasing the number of phenyl groups on silicon atoms, and that the silyl groups act as electron-donating groups to tetraethynylpyrene core. Resonances in ²⁹Si NMR spectra shifts to upfield with increasing the number of phenyl groups on silicon atoms due to the shielding effect of phenyl groups.     

Oxide der 1,2,3-thiadiazole—III : Darstellung und eigenschaften der cycloalkeno-1,2,3-thiadiazole und ihrer mono- und trioxide

Cycloalkeno-1,2,3-thiadiazoles (3a–d) can be prepared from cycloalkanone-tosylhydrazones (2a–d) by treatment with SOCl₂. Oxidation of 3a–d with peracetic acid yields 1,2,3-thiadiazole-2-oxides (4a–d) and 1,2,3-thiadiazole-1,1,2-trioxides (5a–c). A characterisation of these three classes of compounds is performed by discussion of their UV, IR, NMR and mass spectra.     

β to β Terpyridylene-bridged porphyrin nanorings

β β to Terpyridine bridged cyclic porphyrin dimer, trimer, tetramer and pentamer were obtained through one-pot Suzuki-Miyaura crossing coupling reaction in good yields with template free. These porphyrin nanorings possess high fluorescence quantum yields and large extinction coefficients.     

Magnetic circular dichroism and anomalous fluorescence spectra of [2,2] (2,6)azulenophanes

The electronic absorption spectra of syn-[2,2] (2,6) azulenophane (1) and anti-[2,2] (2,6)azulenophane (2) were investigated via magnetic circular dichroism spectra. The anomalous fluorescence spectra were also observed. From the assignment of the absorption spectra, it was concluded that molecules 1 and 2 emitted the fluorescence from the third excited singlet state.     

Characterization of the Excited States of Indigo Derivatives in their Reduced Forms

A comprehensive characterization of the electronic spectral and photophysical properties of the leuco (reduced) form of several indigo derivatives, including indigo and Tyrian Purple, with di‐, tetra‐, and hexa‐substitution, was obtained in solution. The characterization involves absorption, fluorescence, and triplet–triplet absorption spectra, together with quantitative measurements of quantum yields of fluorescence, ?_F (0.46–0.04), intersystem crossing, ?_T (0.013–0.034), internal conversion, ?_IC, and the corresponding lifetimes. The position and degree of substitution promote differences in the spectral and photophysical properties displayed by the investigated leuco derivatives. The ?_F values are about two orders of magnitude higher than those previously obtained for the corresponding keto forms. Also in contrast with the behavior found for the keto forms, the S₁～～→T₁ intersystem crossing is an efficient route for the excited‐state deactivation channel. These findings strengthen the fact that, in contrast to keto indigo where the internal conversion dominates the deactivation of the excited‐state, with leuco indigo (and derivatives), the excited state deactivation involves competition between internal conversion, triplet state formation, and fluorescence. A time‐resolved investigation of one of the compounds in glycerol showed the presence of a photoisomerization process.     

Green synthesis and photophysical properties of novel 1H-imidazo[4,5-f][1,10]phenanthroline derivatives with blue/cyan two-photon excited fluorescence

A simple, rapid, and highly efficient method has been developed for the synthesis of a series of novel 1H-imidazo[4,5-f][1,10]phenanthroline derivatives (1BN, 2Py, 3BI, 4BT, and 5MOBI) via a three–component, one–pot reaction under solvent–free conditions. Their structures were characterized by FT–IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis. Their photophysical properties, including linear absorption, one–photon excited fluorescence, two–photon absorption, and two–photon excited fluorescence, were systematically investigated in various solvents. The results demonstrate that all the compounds emit relatively strong blue/cyan fluorescence. 1BN and 5MOBI exhibit large two–photon absorption cross–sections (471 and 654 GM) in THF. In addition, the relationship between the electronic structures and photophysical properties was investigated using density functional theory.     

Structures and spectroscopic properties of meso-tetrasubstituted porphyrin complexes: Meso-substitutional and central metallic effect study based on density functional theory calculations

Effects of the meso-substituents and central metals on the molecular structures, atomic charges, molecular orbital energy gaps, electronic absorption spectra, and infrared (IR) spectra of 12 meso-tetrasubstituted porphyrin complexes including metal-free porphyrins H₂P or (Por = TPP, TFPP, TClPP, TPyP) (1–4) and their metal complexes MPor (M = Mg, Zn; Por = TPP, TFPP, TClPP, TPyP) (5–12) [TPP = meso-tetrakis(phenyl)porphyrinate; TFPP = meso-tetrakis(4-fluorophenyl)porphyrinate; TClPP = meso-tetrakis(4-chlorophenyl)porphyrinate; TPyP = meso-tetrakis(4-pyridyl) porphyrinate] are systematically studied by density functional theory calculations at the B3LYP/6-31G(d) level. Good consistency was found between the calculated molecular structures and the experimental X-ray crystallography ones for 1, 3, and 4, and between the simulated electronic absorption and IR spectra and the experimental ones for 1 and 4. The calculation results reveal that introducing substituents at the meso positions of porphyrin induces increasing change in the molecular structures, atomic charges distribution, HOMO and LUMO energy, electronic absorption spectra, and IR spectra along with the increase in the electron-withdrawing ability of substituents in the order of phenyl, 4-fluorophenyl, 4-chlorophenyl, and pyridyl group. Furthermore, the central metal in porphyrins displays much significant influence on the structure and spectroscopic properties of meso-substituted porphyrin complexes. The electronic absorption and IR spectra of 1–12 are compared and assigned in detail. The present work should be not only helpful towards understanding the meso-substitutional and central metallic effects on the structure and spectroscopic properties of meso-substituted porphyrin complexes, but also useful in correctly assigning electronic absorption and IR spectra for porphyrin complexes.     

Syntheses and spectroscopic properties of substituted diazaborepins with large stokes shift

The substituted diazaborepins (DABs) with halogen (Cl, Br), methoxyl and ethyl ester group on the fifth position of indole unit have large stokes shift, high fluorescence quantum yields and would be used in biomedicine. Their absorption and emission properties were studied in different solvents. Electron-withdrawing group tended to a bathochromic shift of the absorption and fluorescence probably due to its D-π-A structure. Solvatochromic effects were also studied based on Lippert-Mataga equation. DAB-5 with ethyl ester group exhibits more pronounced fluorescence solvatochromic effects than DAB-3 with Br group. The energy gap and simulated stick spectra of DABs based on Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT) calculation was obtained.     

Mass spectrometry as a diagnostic tool for 5-hydroxysteroids

The mass spectra of twelve 5-hydroxysteroids (1–12), indicate that a common feature is the formation of the ion a by loss of the four ring A C atoms 1, 2, 3, and 4, with the H atoms and other substituents attached.     

Synthesis of 3-methyl- and 3,4-dimethylfurans using alkoxide,thiolate, and phenoxide-mediated cyclization of 4-oxahepta-1,6-diynes bearing sulfur and selenium functional groups

We have reported sodium alkoxide- or aryloxide-mediated cyclization of 4-oxahepta-1,6-diynes bearing the phenylsulfanyl group 1a–d. The reactions with diverse sodium alkoxides and aryloxide produced 4-alkoxymethyl- and 4-aryloxymethylfurans 2aa–2db in good to high yields. Although reactions with sodium benzenethiolate yielded 3,4-bis(phenylsulfanylmethyl)furans 5a–g, they readily desulfanylated in the presence of tributyltin hydride/AIBN to give the 3-methyl- and 3,4-dimethylfuran derivatives 6a–g. This method’s utility was demonstrated by the synthesis of tetrahydronaphthalenyl furan derivatives bearing alkoxy- and aryloxymethyl substituents.     

Furan derivatives—III : Synthesis and properties of β-ketosulphides and sulphur derivatives of chalcones of 5-nitrofuran series

A series of 2-(5-nitro-2-furyl)-2-oxoethylarylsulphides 3a–3h has been prepared by the reaction of 5-nitro-2-furylbromomethylketone 1 with 4-substituted thiophenols 2a–2h. The determined rates of carbanion formation (log k'), pK values as well as ¹H NMR data show that in these compounds transmission of polar effects by the substituents through the -S- group occurs. Compounds 3a–3h react with aromatic aldehydes affording sulphur chalcone derivativěs of the 5-nitrofuran series 4a–4h. ¹H NMR, IR and UV spectra of prepared compounds are discussed.     

Artemisinin-isatin hybrids with potential antiproliferative activity against breast cancer

Three series of artemisinin-isatin hybrids 8a-i, 10a-c and 11a-e were designed, synthesized and evaluated for their antiproliferative activity against breast cancer cells (MCF-7, MDA-MB-231 and doxorubicin-resistant MCF-7 (MCF-7/DOX)), as well as the cytotoxicity towards normal MCF-10A breast cells. The preliminary results showed that a significant part of the synthesized hybrids (IC₅₀: 20.7–99.9 µM) were active against both drug-sensitive and doxorubicin-resistant breast cancer cell lines. The structure–activity relationship illustrated that the linker between artemisinin and isatin moieties as well as the substituents on C-3 and C-5 position of isatin motif had great influence on the activity. In particular, hybrids 11c,d were found to be most active against all tested breast cancer cell lines, and their activity was not inferior to that of doxorubicin. Therefore, hybrids 11c,d could serve as useful templates for the development of novel anti-breast cancer agents.     

Phthalocyanines formed from several precursors: synthesis,characterization, and comparative fluorescence and quinone quenching

Abstract

We have synthesized a new phthalonitrile with different substituents in 4- and 5-positions (1). Cyclotetramerization of 1 yielded phthalocyanines with cobalt(II) (2), zinc(II) (3), gallium(III)chloride (4), and indium(III)chloride (5) containing diethylamino-phenoxy and hexylsulfanyl substituents on each benzene unit. Elemental analyses, Fourier transform infrared spectra, ¹H-nuclear magnetic resonance spectra, mass spectra, and ultraviolet-visible spectra were used for characterization of the phthalocyanines. The aggregation behavior of the zinc phthalocyanine derivative was studied in different concentrations. Also four chloro and four diethyllaminophenoxy substituted zinc phthalocyanine (6) and octa-diethylaminophenoxy substituted zinc phthalocyanine (7) were synthesized. These phthalocyanines (3, 6, and 7) were compared for electronic absorption spectra, fluorescence quantum yields, fluorescent lifetimes, and fluorescence quenching in the presence of benzoquinone. The fluorescence quantum yield gives the efficiency of the fluorescence process. The fluorescence lifetime is an important parameter for practical applications of fluorescence such as fluorescence resonance energy transfer and fluorescence-lifetime imaging microscopy.     

The effect of substituents on the response of 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one derivatives toward binding of Cu2+

A new series of fluorogenic chelating reagents based on phenylethylidene-3,4-dihydro-1H-quinoxalin-2-one with different substituents (attached either to the quinoxaline-2-one (3) or phenyl ring (4)) have been investigated to examine the effect of the substituent (nature/position) on the spectral properties and response toward Cu²⁺ in the presence of other metal cations, in ethanol. It was found that all of the examined ligands exhibit a pronounced response to Cu²⁺ addition resulting in a red-shift in the UV–vis spectra and a strong quenching in the fluorescence spectra. Among the ligands examined, 3a exhibits the highest selectivity toward various metal cations. In general it appears that the best response selectivity of these ligands toward Cu²⁺ ion is obtained by either EDG in 3 or EWG in 4. For example, the fluorescence intensity of 3a (with OMe substituent) increases to about three times that of the unsubstituted derivative.     

The Si-B chromophore: A joint experimental and theoretical investigation

Silylboranes with aromatic substituents linked to boron and silicon exhibit an unexpected absorption band in the UV-Vis spectral region. When polar groups were introduced, a marked solvatochromic effect was observed in their fluorescence emission spectra, revealing a strong excited state dipole moment. Semi-empirical MNDO/d and AM1 calculations showed that, upon UV excitation, the polarity of the Si-B bond increased and the aromatic π-electrons migrated toward the Si-B bond, consistent with experimental observations.     

Synthesis of bis-fused tetrathiafulvalene with mono- and dicarboxylic acids

Bis-fused tetrathiafulvalenes with mono- and dicarboxylic acids, 2-{5-(1,3-dithiol-2-ylidene)-[1,3]dithiolo[4,5-d][1,3]dithiol-2-ylidene}-1,3-dithiole-4-carboxylic acid (1) and 2-{5-(1,3-dithiol-2-ylidene)-[1,3]dithiolo[4,5-d][1,3]dithiol-2-ylidene}-1,3-dithiole-4,5-dicarboxylic acid (2) have been synthesized. The electronic structure of 1 and 2 was examined from their optical absorption spectra and using density-functional calculations.     

Acid catalyzed rearrangements in bicyclo[3.3.1]nonanes : 2-Substituted-6-(1,3-dioxolan-2-yl)-cyclooctanones from 1-substituted-2-hydroxy-9,9-(ethylenedioxy)-bicyclo[3.3.1]-nonanes

Treatment of endo-2 or exo-2-hydroxy-1-substituted ketals 1a–d with p-toluensulfonic acid in dry benzene results in a reversible C₉ bridge cleavage and affords equilibrium mixtures where 2-substituted-6-(1,3-dioxolan-2-yl)cyclooctanones 6a–d are present as main products. Yields in 6a–d are present as the steric hindrance of the substituents at C₁ in the substrate increases as well. Deuterium exchange experiments are in favour of an intramolecular 1,3-hydride shift from C₂ to C₉.