Unsubstituted Analogues Research Articles

PyrrolylBODIPYs: Syntheses, Properties, and Application as Environment-Sensitive Fluorescence Probes.

Four pyrrole B-ring-functionalized pyrrolylBODIPYs and their B-ring unsubstituted analogues were synthesized from easily accessible starting 5-halo-2-formylpyrroles and were characterized by nuclear magnetic resonance, high-resolution mass spectrometry, X-ray analysis, and optical/electronic properties. In great contrast to the substitution(s) at the other two pyrrolic units, electron-donating substituent(s) at pyrrole B-ring bring significant blue shift of the absorption and emission bands. Cyclic voltammetry and density functional theory calculations indicate that this blue shift may be attributed to the increased highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels and the overall increase in the energy band gaps. These pyrrolylBODIPYs generally show intense absorption (centered at 570–624 nm) and fluorescence emission (582–654 nm) in nonpolar solvents. A gradual decrease in the fluorescence intensity was observed for these dyes with the increase in solvent dipolar moment, which combines with the red to far-red absorption/emission, rendering these pyrrolylBODIPYs potential applications as environment-sensitive fluorescence probes as demonstrated in this work for bovine serum albumin.

Thermodynamics, kinetics and microstructural evolution of Ti0.43Zr0.07Cr0.25V0.25 alloy upon hydrogenation

Zr substituted Ti2CrV alloy with Ti0.43Zr0.07Cr0.25V0.25 composition was synthesized by arc melting method and its crystal structure, microstructure and hydrogen storage performance were investigated. XRD and microstructural analyses confirmed that the alloy forms Laves phase related BCC solid solution. The enthalpy of hydride formation as derived from pressure composition absorption isotherms is −56.33 kJ/mol H2. The desorption temperature of the hydride is significantly lower (by ∼50 K) than that of Ti2CrV hydride indicating lower thermal stability of the hydride compared to its unsubstituted analogue. The alloy shows better cyclic stability over the unsubstituted one. This work also offers mechanistic insight into hydrogen absorption reaction of Ti0.43Zr0.07Cr0.25V0.25 alloy by analyzing the hydriding kinetics data with standard kinetic models. The rate-determining steps of hydrogen absorption reaction were identified as random nucleation and growth of hydride followed by 1D and 3D diffusion of hydrogen atoms through the hydride layer. The present study is expected to provide valuable information for the better development of Ti–Cr–V based hydrogen storage alloys.

Dyes derived from benzo[ a ]phenoxazine – synthesis, spectroscopic properties, and potential application as sensors for l ‐cysteine

Several benzo[a]phenoxazine dyes containing a maleimide moiety have been synthesised and characterised by proton nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic properties, such as absorption and emission spectra, of these dyes – 9-maleimido-5H-benzo[a]phenoxazin-5-one (7a), 6-chloro-9-maleimido-5H-benzo[a]phenoxazin-5-one (7b), and 6-bromo-9-maleimido-5H-benzo[a]phenoxazin-5-one (7c) – were examined. These compounds were evaluated as potential fluorescent and colorimetric probes for the detection of biothiols. Results show that the studied compounds exhibit colorimetric and fluorescent responses to l-cysteine at pH 7.4. In the presence of l-cysteine, the fluorescence intensity of synthesised dyes is greatly enhanced. The addition of l-cysteine to solutions of dyes 7a to 7c also results in red shifts of their absorption bands. The cytotoxic effect of tested dyes 7a to 7c against human neuroblastoma cells (SH-SY5Y) was determined by MTT assay. The fluorescent response of these compounds to thiols SH-SY5Y was examined. The results show that the tested compounds exhibit fluorescent response in this cell line, and the benzo[a]phenoxazine dyes substituted in the 6-position with a halogen (7b and 7c) are less toxic against cells under experimental conditions than their unsubstituted analogue (7a).

Bioconversion of 6-(N-methyl-N-phenyl)aminomethyl androstane steroids by Nocardioides simplex

The newly synthesized (α/β)-diastereomers of 6-(N-methyl-N-phenyl)aminomethylandrost-4-ene-3,17-dione (5) and 6-(N-methyl-N-phenyl)aminomethylandrost-4-en-17β-ol-3-one (6) were firstly investigated as substrates for the whole cells of Nocardioides simplex VKM Ac-2033D in comparison with their unsubstituted analogs, – androst-4-ene-3,17-dione (1) and androst-4-en-17β-ol-3-one (2).1(2)-Dehydroderivatives were identified as the major bioconversion products from all the substrates tested. When using the mixtures of (α/β)-stereoisomers of 5 and 6 as the substrates, only β-stereoisomers of the corresponding 1,4-diene-steroids were formed. Along with 1(2)-dehydrogenation, N. simplex VKM Ac-2033D promoted oxidation of the hydroxyl group at C-17 position of 6: both 6(α) and 6(β) were transformed to the corresponding 17-keto derivatives. No steroid core destruction was observed during the conversion of the 6-substituted androstanes 5 and 6, while it was significant when 1 or 2 was used as the substrate.The results suggested high potentials of N. simplex VKM Ac-2033D for the generation of novel 1(2)-dehydroanalogs.

Synthesis of linear and angular aryl-morpholino-naphth-oxazines, their DNA-PK, PI3K, PDE3A and antiplatelet activity

To continue our study of 2-morpholino-benzoxazine based compounds, which show useful activity against PI3K family enzymes or antiplatelet activity, we designed and synthesized a series of linear 6.7-fused, 5,6-angular fused and 7,8-angular fused-aryl-morpholino-naphth-oxazines. The compounds were prepared from substituted 2-hydroxynaphthoic acid to give the corresponding thioxo analogues 8, 9, 15 and 19. The thioxo products were then converted to the morpholino substituted analogue. The aryl group was introduced by Suzuki coupling of bromo precursors. The products were evaluated for activity at PI3K family enzymes and as platelet aggregation inhibitors and compared to reported unsubstituted analogues. The linear 6.7-fused product 13a and 13b were moderated potent but selective PI3Kδ isoform inhibitors (IC50=7.7 and 5.61μM). Good antiplatelet activity was noticed for the angular 7,8-fused compounds 22a, b, k and l with IC50=3.0,14.0, 2.0 and 5.0μM respectively. The antiplatelet activity is independent of PDE3.

Methoxy supported, deep red emitting mono, bis and tris triphenylamine-isophorone based styryl colorants: Synthesis, photophysical properties, ICT, TICT emission and viscosity sensitivity

A novel strategy for the synthesis of triphenylamine based and methoxy supported deep red emitting push-pull chromophores is developed. The methoxy groups though not in conjugation with the acceptor exhibited a red shifted absorption and emissions (670 nm) as compared to the unsubstituted analogues due to the improved donating ability of triphenylamine. The dyes show high molar extinction coefficients (1, 65,800 M−1 cm−1) and as the number of withdrawing groups increases the molar extinction coefficient and emission intensity increase. Positive solvatochromism (96 nm) was observed which is well supported by linear and multi-linear regression. The mono styryl dyes showed enhancement of fluorescence while the di and tri-styryl dyes show quenching of fluorescence in polar solvents, which is correlated with the intramolecular charge transfer and twisted intramolecular charge transfer. Viscosity induced emission enhancement has also been observed. The experimental findings were correlated theoretically by using Density Functional theory computations.

The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

ABSTRACTTwo homologous series of 4-alkoxyphenylazo 4ʹ-(2ʺ- (and 3ʺ-) methyl-) 4ʹ-substituted benzoates (IIna–f and IIIna–f, six series each) were prepared and investigated. Within each series, the length of the terminal alkoxy group varies among 6, 8, 10 and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changes between the electron-donating CH3O, CH3, and the electron-withdrawing Br, NO2 and CN groups, in addition to the un-substituted analogue, X = H, aiming to investigate the effect of the different orientations of the methyl groups substituted on the central benzene ring, on the mesophase behaviour. The mesomorphic properties were discussed in terms of steric and polarisability effects. The mesophase stability was correlated with the polarisability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the prepared isomers with each other and with the previously investigated laterally neat analogues 4-(4ʹ-alkoxyphenylazo) phenyl 4ʺ-substituted benzoates (Ina–f).

Effect of fluorine substitution on naphtho[2,1-b:3,4-b′]bis[1]-benzothiophene-derived semiconductors for transistor application

A novel series of air-stable, fluorinated naphtho [2,1-b:3,4-b′]bis [1]-benzothiophenes bearing various lateral alkoxy-substituents, NBBTF-n (n = 8, 10, and 12) and its unsubstituted analogue, NBBT-10 were synthesized and investigated with field-effect transistor properties. Fluorine substitution affords desirable properties including high melting transition, high thermal stability and low-lying highest occupied molecular orbital (HOMO) energy levels for air-stable semiconductors. The OFET devices based on annealed NBBTF-10 films exhibit superior hole transport with mobility up to 0.35 cm2 V−1 s−1 to that of NBBT-10, attributed to the close molecular stacking induced by fluorine substitution.

Synthesis and photophysical characteristics of 2,3,12,13-tetraalkylbacteriochlorins

Tetraalkylbacteriochlorins, available upon acid-mediated self-condensation of α-ester stabilized dihydrodipyrrin-carboxaldehydes, provide valuable models of the naturally occurring bacteriochlorophylls.

CaMoO4:RE3+,Yb3+,M+ phosphor with controlled morphology and color tunable upconversion

CaMoO4:RE3+,Yb3+ (RE=Er, Ho, Tm) phosphors were successfully synthesized by a facile hydrothermal method. XRD patterns confirmed tetragonal structure under different RE3+ and M+ ions doping conditions. Particles shapes and sizes were confirmed by SEM and TEM analyses. Particles shape and size were well tuned by control of solution pH; spherical balls consisting of nano-grains at low pH of ∼2, rice grain shapes at moderate pH of ∼6, and thin flakes at higher pH of ∼12, were observed. Fine tunability of upconversion (UC) emission color was achieved by doping multiple RE3+ ions within a single CaMoO4 host. Blue, green and orange upconverted emission were observed by doping Tm3+, Er3+ and Ho3+ in the CaMoO4, respectively. Further, the emission colors were well tuned by the combination of Tm, Er and Ho ions and their concentrations. CaMoO4:Tm3+,Ho3+,Yb3+ exhibited perfect white emission with well tunability from cool white to warm white colors. Substitution of part of Ca ions by M+ (M=Li, Na, K, Rb) ions affected the crystal field symmetry around RE3+ ions and hence changed the transition probabilities between their f–f transition levels, consequently intensified the UC intensities. The blue (Tm3+), green (Er3+), and orange (Ho3+) upconversion intensities of CaMoO4:RE3+,Yb3+,0.10K+ phosphors increased by 60, 50 and 40 folds compared to the unsubstituted analogues, respectively. The K substituted CaMoO4:RE3+,Yb3+,K+ phosphors exhibited intense UC emissions visible by naked eye even pumped by less than 1mW laser power and can have potential application in displays and variety of other applications.

ChemInform Abstract: Synthesis of 4‐(Dimethylamino)quinazoline via Direct Amination of Quinazolin‐4(3H)‐one Using N,N‐Dimethylformamide as a Nitrogen Source at Room Temperature.

AbstractThe cost‐effective high‐yielding method tolerates a diverse range of 2‐aryl and 2‐hetaryl substituted quinazolin‐4(3H)‐ones, but no alkyl or unsubstituted analogues.

How substitution tunes the electronic and transport properties of oligothiophenes, oligoselenophenes and oligotellurophenes

The geometrical, electronic and charge-transport properties of a series of unsubstituted and dicyanovinyl (DCV)-substituted oligothiophenes (nT), oligoselenophenes (nS) and oligotellurophenes (nTe) where n=3–5 are investigated by means of Density Functional Theory (DFT) and Time-Dependent DFT calculations. The intramolecular reorganization energy is found to decrease upon dicyanovinyl substitution, with a larger decrease for holes than electrons. The ground state HOMO and LUMO energies along with the Time-Dependent DFT calculations show smaller HOMO–LUMO gaps for the DCV-substituted oligomers. Calculations of the intermolecular charge transfer integrals in the crystals have been performed to understand the role of substitution on the charge-transport rate. DCV-substitution changes the packing motifs in the crystal and results in larger transfer integrals for holes along the π-stacking direction, calculated as −63 and −88meV for DCV4T and DCV4S respectively. These results suggest that DCV-substituted oligomers studied here are more promising charge transporting materials than their unsubstituted analogues.

The synthesis of indolo[2,3-b]quinoline derivatives with a guanidine group: Highly selective cytotoxic agents

The synthesis of indolo[2,3-b]quinoline derivatives containing guanidine, amino acid or guanylamino acid substituents as well as their in vitro evaluation for the cytotoxic and antifungal activity are reported. The influence of the guanidine group on the selective cytotoxic and hemolytic properties of indolo[2,3-b]quinoline was investigated. Most of the compounds displayed a high cytotoxic activity in vitro and two of the most promising compounds (3 and 12) exhibited a high selectivity between normal and cancer cell-lines. The cytotoxic activity of compound 3 was about 600-fold lower against normal fibroblasts than against A549 and MCF-7 cancer cell lines. Novel entities acted as the DNA-intercalators when tested using a DNA–methyl green assay but demonstrated zero or low hemolytic activity in comparison to their unsubstituted analogs. The mechanism of action was studied for guanidine derivatives 3 and 12 and both compounds were found to be very effective inducers of apoptosis.

The effect of lateral methyl substitution on the mesophase behaviour of aryl 4-alkoxyphenylazo benzoates

In order to investigate the effect of lateral methyl substitution on the mesophase behaviour of the previously investigated laterally neat 4-substituted phenyl 4ʹ-(4ʺ-alkoxyphenylazo) benzoates (Ina–e), five homologous series of 4-substituted phenyl 4ʹ-(3ʺ-methyl-4ʺ-alkoxyphenylazo) benzoates (IIna–e) were prepared in which, within each homologous series, the length of the terminal alkoxy group varies between 8, 10, 12, 14, and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed between the electron-donating CH3O and CH3 groups, and the electron-withdrawing Br and CN groups, in addition to the unsubstituted analogue. Two other isomeric series (IIIna–e) were also prepared in which the methyl group is laterally attached, this time, to position 2 of the same ring, aiming to investigate the effect of the different orientation of the methyl groups on the mesophase behaviour of the produced isomers. The results were discussed in terms of steric, mesomeric, and polarisability effects.

A Methyl‐Substituted Thiophene–Tetra­thiafulvalene Donor and Its Salts

α-Methyldithiophene–tetrathiafulvalene (α-mDT-TTF), the first alkyl-substituted thiophene–tetrathiafulvalene electronic donor, and some of its charge-transfer salts were explored. The crystal structure of α-mDT-TTF is composed of molecular stacks aligned parallel to each other. Its cyclic voltammetry shows higher electron-donor ability than the unsubstituted analogue. This material was employed as a semiconductor in an organic field-effect transistor and showed a mobility of 4 × 10–4 cm2 V–1 s–1. Two charge-transfer salts of this donor with [M(mnt)2]– anions (mnt = maleonitriledithiolate), M = Co and Au, were obtained by electrocrystallization; they present unusual stoichiometries: (α-mDT-TTF)[Co(mnt)2] and (α-mDT-TTF)3[Au(mnt)2]2. In the cobalt compound, the donor molecules are fully oxidized and the Co complex is dimerized; it presents semiconducting behavior (7 × 10–3 S cm–1). The gold compound is composed of alternating stacks of donor trimers and pairs of anions.

Tuning the LUMO energy of 1,10-phenanthroline in α-diimine–dithiolate Ni(II) complex and enhancement of nonlinear optical properties

The synthesis, characterization, nonlinear optical properties and DFT calculations for a new Ni-diiminedithiolate complex [Ni(Cl4-phen)(mi-5edt)] (Cl4-phen=3,4,7,8-tetrachloro-1,10-phenanthroline; mi-5edt=1-(N-methylindol-5-yl)-ethene-1,2-dithiolate), are reported. The UV–Vis spectrum shows a solvatochromic absorption at 700nm in DMF (ε=5520mol−1dm3cm−1) due to a charge-transfer (CT) highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) transition, typical of push–pull complexes. The CT character of this electronic transition is confirmed by DFT calculations with the HOMO mainly centered on the mi-5edt moiety and the LUMO on the Cl4-phen ligand. By comparison with the unsubstituted analogue compound, computational studies confirm the role of the chlorination enhancing the optical properties of this complex. The second order nonlinear optical properties were measured by EFISH technique (at 1.907μm), giving values of −2030 and −810×10−48esu for μβ1.907 and μβ0, respectively. These values are among the highest reported so far for the class of d8 square-planar push–pull compounds.

Mössbauer study of a tetrakis (pentafluorophenyl) porphyrin iron (III) chloride in comparison with the fluorine unsubstituted analogue

Abstract Mössbauer investigations, in association with density functional theory (DFT) calculations, have been conducted for the molecular and electronic structures of iron (III) [tetrakis (pentafluorophenyl)] porphyrin chloride [(F20TPP)Fe:Cl], as a Fe(III)-tetraphenylporphyrin complex containing chloride axial ligand and substituted hydrogen atoms by fluorine ones in the four phenyl rings, in comparison with its fluorine unsubstituted analogue [(TPP)Fe:Cl]. It was found that the parameters of Mössbauer spectra of both complexes are close to one another, and correspond to the high-spin state of Fe(III) ions, but they show the different temperature dependence and the quadrupole doublets in Mössbauer spectra show different asymmetry at low temperatures. Results of DFT calculations are analyzed in the light of catalytic activity of the halogenated complex.

Intramolecular charge transfer in coumarin based donor-acceptor systems: Formation of a new product through planar intermediate

Abstract Fluorescence behavior and intramolecular charge transfer (ICT) property of N,N′-dimethylamino substituted anil derivative of coumarinyl amine was studied by steady state and time-resolved fluorescence spectroscopy in combination with density functional theory calculation. Quantitative analysis of the effect of solvent hydrogen bonding on several spectral parameters was done using multiple regression analysis based on Kamlet–Taft model. The present system shows an additional long wavelength fluorescence band almost instantaneously in presence of methanol in sharp contrast to the model unsubstituted analogue. This new fluorescence band is believed to be due to the formation of a new isomer (cis-type) through a planar intermediate. While there is a substantial barrier (∼50 kJ mol−1) in the ground state, the isomerization process in the excited state in polar-protic environment proceeds very fast and believed to be catalyzed by hydrogen bond formation at the imine nitrogen atom in combination with stabilization of the resulting species through ICT.

Thermodynamic Properties of the Site-selective Binding of a Bromo-hydrazone and Its Unsubstituted Analogue to Human Serum Albumin

A bromine-substituted hydrazone derivative, named N′-(4-bromobenzylidene)-2-hydroxybenzohydrazide (BBH), and its unsubstituted analogue, named N′-benzylidene-2-hydroxybenzohydrazide (BH), have been synthesized by a simple and effective one-pot synthesis method. Their interactions with human serum albumin (HSA) were comprehensively studied employing spectroscopy, electrochemistry, and molecular docking. Our attention was largely on the thermodynamic properties of their binding to HSA, in order to evaluate the impact of a bromine atom in BBH to its biological activity comparing to BH. BBH is a stronger ligand with a binding constant of 105 L·mol−1 and formed a more stable complex with HSA compared with BH. The binding processes of both BBH and BH are mainly an enthalpy driven process occurring in site I, mainly bound by hydrogen bonding and the van der Waals force.

Comparative analysis of interactions of some lariat crown ethers and their unsubstituted analogues with alkali metal salts in the gas phase by MALDI mass spectrometry

In this work, interactions of some crown ethers, including lariat ethers bearing a side-arm methoxyphenoxymethyl substituent, with alkali metal salts were studied by matrix assisted laser desorption/ionization mass spectrometry. Peaks of cationized molecules [M + Cat]+, sandwich complexes [2M + Cat]+, [3M + Cat]+ ions, and cluster ions [2M + 2Cat + An]+ and [2M + 3Cat + 2An]+ were observed in the mass spectra; herein M is a crown ether molecule, Cat is an alkali metal cation, and An is a monobasic acid anion. The results were compared with previously obtained data for 15-crown-5, [ortho]- and [para]-methoxyphenoxymethyl-15-crown-5 ether mixtures with sodium salts. The conclusions made before, that an increase in the shielding degree of the cation in complexes with lariat ethers led to a significant decrease in the peak intensity of cluster ions [2M + 2Cat + An]+, were confirmed. For potential lariat ethers the absence or only trace amounts of such cluster ions along with the presence of an intense cluster ion peak in the mass spectrum for an unsubstituted analogue can serve a test for the involvement of the lateral fragment of the crown ether in complex formation, i.e., the lariat effect.