Shift Of Λmax Research Articles

DFT Study of Structural, Electronic, and Charge-Transfer Properties of 2-Naphthol Azo Derivatives: Geometric, Positional, and Substituent Effects.

This work represents a systematic computational study of structural and optoelectronic properties of 24 phenylazo-2-naphthol derivatives using the DFT-B3LYP/6-31 + G(d,p) method. The positional isomers of azo compounds have been designed by introducing an azophenyl unit (with and without substituents) at three different (1-, 3-, and 4-) positions of 2-naphthols. This result shows that depending on the linking position of the azophenyl unit and substituents (NO2 and maleimide), the cis-azo, trans-azo, and hydrazo forms of our substituted azo derivatives possess distinguished UV-vis absorption and charge-transfer properties compared to unsubstituted Sudan I derivatives. Our MO calculations show that all Sudan-MI azo derivatives exhibit unique intramolecular charge transfer from the 2-naphthol-azo group as a donor to the maleimide (MI) group as an acceptor. Interestingly, whereas the trans-azo and hydrazo forms of Sudan-MI derivatives show ππ*CT and nπ*CT beside the ππ* and nπ* transitions, the cis-azo Sudan-MI derivatives exhibit mixed (nπ* + ππ*)CT along with ππ*CT, ππ*, and mixed (nπ* + ππ*) transitions. The nature and order of the main azo ππ* (S0 → S2) and nπ* (S0 → S1) transitions alter in Sudan-MI derivatives. The respective substitution of NO2 and MI groups in Para Red and Sudan-MI series leads to the bathochromic shift of λmax (due to π → π* transitions) in comparison to unsubstituted Sudan I derivatives, for example, the 4-positional Para Red trans-azo isomer (λmax 516.9 nm) is 93.8 nm and the 4-positional Sudan-MI trans-azo isomer (λmax 447.3 nm) is 24.2 nm red-shifted compared to the 4-positional Sudan I trans-azo isomer (λmax 423.1 nm). The cis-azo forms of all positional isomers having twisted geometries show different UV-vis spectral behaviors. In general, our studies demonstrate how the variation in the structure of azo compounds impacts their optoelectronic properties, which could be useful in electronic devices.

Structural modification of V1274 moiety to red-shift its light absorption for optical and photovoltaic properties: A DFT molecular insight

In this study, we propose a theoretical strategy to enrich the electronic populations at V1274 core to develop new hole-transporting insulators (1–7) to red shift its maximum absorption (λmax). All calculations are performed using Coulomb Attenuated Method- Becke three parameter Lee–Yang-Parr (CAM-B3LYP) method at the Density Functional Theory (DFT) level. The photovoltaic results vary across different parameters as Open Circuit Voltage (Voc) ranges from 0.87 to 0.98 V, Fill factor (FF) ranges from 0.190 to 0.863, Short Circuit (Jsc) ranges from 26.10 to 48.38 mA/cm2, and Maximum Power (Pmax) ranges from −9.38 to 31.85 W. The λmax varies from 372 to 658 nm. This enhanced absorption capability by the push-pull effect indicates their effectiveness of the chromophores in absorbing light in that specific wavelength range. The significant new density of states (DOS) after adsorbing the designed chromophores onto the TiO2 cluster indicates potential changes in the electronic structure and properties of the material. The significant shift of λmax towards the near-infrared region after nitrogen replacement is important because it indicates improved light absorption in that range, which could enhance its suitability for applications such as near-infrared photodetection or solar energy harvesting.

Supramolecular J- and H-Aggregation of Naphthalimide-Conjugated Dipeptide in Mixed-Solvent Systems and its Application in Cell Imaging.

In this work, a core-substituted NMI-conjugated dipeptide (4MNLV) was extensively studied in mixed solvent systems to explore the polarity effect on the self-assembly pattern and their photophysical property. 4MNLV adopted J- or H- type aggregation pattern depending upon the polarity index of the solvent system chosen. The self-assembly process was achieved through the anti-solvent effect. UV-vis study suggested that if the stock solution of 4MNLV was diluted with a relatively more polar solvent (compared to the stock solvent), then the system acquired J- type of aggregation pattern by showing a red-shift in their absorption maxima (λmax). Conversely, when the stock was diluted by a relatively less polar solvent, H-type of aggregation was observed, where blue shift of λmax was noticed. The emission spectra and the lifetime of the self-assembled materials were also influenced by the chosen solvent system. The chirotopic behaviour of these self-assembled materials was studied through CD spectroscopy. Morphological study indicated the formation of helical nanofibrillar structures. The bright green fluorescence of these highly biocompatible naphthalimide-peptide conjugate was used for cell imaging application, indicating its futuristic scope.

Knockout of lws1 in zebrafish (Danio rerio) reveals its role in regulating feeding and vision-guided behavior.

Long-wave sensitive (LWS) is a G protein-coupled receptor expressed in the retina, and zebrafish is a better model organism for studying vision, but the role of LWS1 in vision-guided behavior of larvae fish has rarely been reported. In this study, we found that zebrafish lws1 and lws2 are tandemly replicated genes, both with six exons, with lws1 being more evolutionarily conserved. The presence of Y277F in the amino acid sequence of lws2 may have contributed to the shift of λmax to green light. We established a lws1 knockout zebrafish model using CRISPR/Cas9 technology. Lws1-/- larvae showed significantly higher levels of feeding and appetite gene (agrp) expression than WT, and significantly lower levels of anorexia gene (pomc, cart) expression. In addition, green light gene compensation was observed in lws1-/- larvae with significantly increased expression levels of rh2-1. The light-dark movement test showed that lws1-/- larvae were more active under light-dark transitions or vibrational stimuli, and the expression of phototransduction-related genes was significantly up-regulated. This study reveals the important role of lws1 gene in the regulation of vision-guided behavior in larvae.

Synthesis, Characterization, and Photophysical Probing Interaction Studies on Azo‐Sulfonamides Acting as Potent Anti‐Tubercular Agents

AbstractBy utilizing the sulfamethizole component via the diazo‐coupling approach by electrophilic substitution process, an unprecedented series of four mono‐azo sulfonamide molecules were synthesized in good yield. Spectroscopic investigation unambiguously confirmed the structures of the newly synthesized mono‐azo sulfonamide derivatives, including FT‐IR, NMR (1H and 13C), HRMS, Uv‐Vis, and Photoluminescence (PL). In a variety of organic solvents, the 3‐diethylaminophenol coupled azo‐sulfonamide T3 showed a maximum bathochromic shift of λmax in the range 462–479 nm and in the region of 88–142 nm, a derivative of 2‐hydroxy‐1,4‐naphthoquinone T4 coupled azo colourant showed a significant Stokes shift. Conceptual density function theory was also used to build a new family of high energy density energetic mono‐azo sulfonamides. Frontier molecular orbitals (HOMO‐LUMO) and global reactivity descriptors were identified to analyze how molecules interact with one another. Further, the potency of the anti‐tubercular activity of the colorants was examined with the standards such as Isoniazid, Ethambutol, Pyrazinamide, Rifampicin, and Streptomycin. The results indicated that‐ Lawsone pigment (2‐hydroxy‐1,4‐naphthoquinone) incorporated azo molecule T4 displayed the sensitivity at 3.12 μg/mL compared with other the three mono‐azo molecules.

Orange Carotenoid Protein in Mesoporous Silica: A New System towards the Development of Colorimetric and Fluorescent Sensors for pH and Temperature.

Orange carotenoid protein (OCP) is a photochromic carotenoprotein involved in the photoprotection of cyanobacteria. It is activated by blue-green light to a red form OCPR capable of dissipating the excess of energy of the cyanobacterial photosynthetic light-harvesting systems. Activation to OCPR can also be achieved in the dark. In the present work, activation by pH changes of two different OCPs-containing echinenone or canthaxanthin as carotenoids-is investigated in different conditions. A particular emphasis is put on OCP encapsulated in SBA-15 mesoporous silica nanoparticles. It is known that in these hybrid systems, under appropriate conditions, OCP remains photoactive. Here, we show that when immobilised in SBA-15, the OCP visible spectrum is sensitive to pH changes, but such a colorimetric response is very different from the one observed for OCP in solution. In both cases (SBA-15 matrices and solutions), pH-induced colour changes are related either by orange-to-red OCP activation, or by carotenoid loss from the denatured protein. Of particular interest is the response of OCP in SBA-15 matrices, where a sudden change in the Vis absorption spectrum and in colour is observed for pH changing from 2 to 3 (in the case of canthaxanthin-binding OCP in SBA-15: λMAX shifts from 454 to 508 nm) and for pH changing from 3 to 4 (in the case of echinenone-binding OCP in SBA-15: λMAX shifts from 445 to 505 nm). The effect of temperature on OCP absorption spectrum and colour (in SBA-15 matrices) has also been investigated and found to be highly dependent on the properties of the used mesoporous silica matrix. Finally, we also show that simultaneous encapsulation in selected surface-functionalised SBA-15 nanoparticles of appropriate fluorophores makes it possible to develop OCP-based pH-sensitive fluorescent systems. This work therefore represents a proof of principle that OCP immobilised in mesoporous silica is a promising system in the development of colorimetric and fluorometric pH and temperature sensors.

Structural and optical properties of sol-gel synthesized TiO2 nanocrystals: Effect of Ni and Cr (co)doping

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. Powder XRD technique reveals that the modified catalyst majorly contains the anatase polymorph with the transition metal ion either substituting Ti or located as interstitials in the lattice of TiO2. Raman and UV–Vis absorption spectra of the doped and codoped catalyst a show λmax shift towards longer wavelength when in the metal ion concentration is increased from 0.25 to 10 wt%. FTIR patterns show the stretching and vibration patterns of hydroxyl radicals present in the nanocrystals. The BET surface areas of the doped and codoped TiO2 nanocrystals have substantially higher surface areas compared with that of the undoped TiO2. Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5% + 5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the incorporation of transition metal ions in the TiO2 nanocrystals.

Effect of Solvent Polarity on the Spectral Characteristics of 5,10,15,20-Tetrakis(p-hydroxyphenyl)porphyrin.

The electronic absorption and vibrational spectra of deprotonated 5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (THPP) are studied as a function of solvent polarity in H2O-DMF, H2O-acetone, H2O-methanol, and DMF-acetone mixtures. The maximum absorption wavelength (λmax) of the lowest energy electronic absorption band of deprotonated THPP shows an unusual solvatochromism-a bathochromic followed by a hypsochromic shift with reduced polarity. According to the correlation analysis, both specific interactions (H-bonds) and nonspecific interactions affect the spectral changes of this porphyrin. Furthermore, the solvent polarity scale ET(30) can explain both shifts very well. At higher polarity (ET(30) > 48), THPP exists as a hyperporphyrin. The ET(30) is linear with λmax and a decrease in solvent polarity is accompanied by a bathochromic shift of λmax. These results can be rationalized in terms of the cooperative effects of H-bonds and nonspecific interactions on the spectra of hyperporphyrin. At relatively low polarity (45.5 < ET(30) < 48), hyperporphyrin gradually becomes Na2P as ET(30) reaches the critical value of 45.5. The spectrum of the hyperporphyrin turns into the three-band spectrum of the metalloporphyrin, which is accompanied by a hypsochromic shift of λmax.

Electronic Excitation Characteristics and Spectral Behavior of Phosphate Anions.

Absorption spectra are fundamental bases for the qualitative and quantitative analysis of the target chemical, and the development of an analytical model can be improved by studying its characteristics and rules. In the present study, the electronic excitation characteristics of phosphate anions (H2PO4-, HPO42-, and PO43-) were analyzed based on the charge-transfer spectrum. In addition, the absorption spectra of phosphate anions at the energy level of PBE0/6-311+G (d,p) were recorded based on the time-dependent density functional theory (TD-DFT) method. Different (HPO42-)n·(H2O)10-n molecular clusters were theoretically constructed, and the combined TD-DFT method and independent gradient model revealed that red shift of the maximum absorption wavelength (λmax) with the increase of phosphate anion concentration (0-10 mM) may be caused by the decrease of hydrogen bond interaction. In addition, the prominent dispersion in the short-wave region mainly resulted in the red shift of λmax with the increase in optical path length (1-100 mm). Moreover, with the increase in spectral bandwidth (0.4-3.0 nm), λmax slightly blue-shifted because of the increase in energy through the slit, and repeatability of the corresponding absorbance measurement at λmax gradually improved. As the spectral bandwidth increased, light monochromaticity became poor, resulting in the decrease of the linearly fitted correlation coefficient of the concentration-absorbance curve. Finally, the multivariate analysis of variance results showed that the optical path length was the most significant factor that influenced the absorption spectral characteristics of phosphate anions. This study provides a basis for the qualitative and quantitative analysis of phosphate anions by using absorption spectra and also renders a theoretical reference for absorption spectroscopy of other chemicals.

Molecular Characterization and Bioactivities of a Novel Polysaccharide from Phyllostachys pracecox Bamboo Shoot Residues.

Dietary carbohydrates are unexploited in the by-products of economically valuable Phyllostachys pracecox bamboo shoots. A residue-derived polysaccharide (PBSR1) was aqueously extracted from the processing waste of this bamboo shoot species. Its primary structure and advanced conformation were elucidated by a combined analysis of spectroscopy, chromatography, 2D nuclear magnetic resonance, laser light scattering and atomic microscopy. The results indicated PBSR1 was a triple-helix galactan consisting of →6)-β-D-Galp and →3)-β-D-Galp in linear with an 863 KD molecular weight (Mw). The relationship between the radius of gyration (Rg) and intrinsic viscosity ([η]) on Mw were established as Rg = 1.95 × 10-2Mw0.52±0.03 (nm) and [η] = 9.04 × 10-1Mw0.56±0.02 (mL/g) for PBSR1 in saline solution at 25 °C, which indicated it adopted a triple-helix chain shape with a height of 1.60 ± 0.12 nm supported by a red shift of λmax in Congo red analysis. The thermodynamic test (TG) displayed that it had excellent thermal stability for the food industry. Further, those unique structure features furnish PBSR1 on antioxidation with EC50 of 0.65 mg/mL on DPPH· and an ORAC value of 329.46 ± 12.1 μmol TE/g. It also possessed pronounced immunostimulation by up-regulating pro-inflammatory signals including NO, IL-6, TNF-α and IL-1β in murine cells. Our studies provided substantial data for the high-valued application of residues and a better understanding of the structure-function relationship of polysaccharide.

TADF and X-ray Radioluminescence of New Cu(I) Halide Complexes: Different Halide Effects on These Processes.

A series of complexes [Cu2X2(Pic3PO)2] (X = Cl, Br, I) based on tris(pyridin-2-ylmethyl)phosphine oxide (Pic3PO) has been synthesized. At 298 K, these compounds exhibit thermally activated delayed fluorescence (TADF) of 1(M+X)LCT type with λmax varying from 485 to 545 nm, and quantum efficiency up to 54%. In the TADF process, the halide effect appears as the emission intensification and bathochromic shift of λmax in the following order X = I < Br < Cl. Upon X-ray irradiation, the title compounds emit radioluminescence, the emission bands of which have the same shape as those at TADF, thereby meaning a similar radiative excited state. By contrast to TADF, the halide effect in the radioluminescence is reversed: its intensity grows in the order X = Cl < Br < I, since heavier atoms absorb X-rays more efficiently. These findings essentially contribute to our knowledge about the halide effect in the photo- and radioluminescent Cu(I) halide emitters.

Synthesis of nitrogen mustard-based fluorophores for cell imaging and cytotoxicity studies.

Nitrogen mustards are important alkylating anticancer drugs used for neoplasms treatment. However, little research about the integration of luminophore into nitrogen mustard-based compounds for both imaging and therapeutic application was reported. In this study, we report a series of novel nitrogen mustard-containing 1-furyl-2-en-1-one and 1-thienyl-2-en-1-one derivatives as intramolecular charge transfer-based luminophore for research in both imaging subcellular localization and antiproliferation toward lung cancer cells. The target products were prepared by Knoevenagel condensation and characterized by nuclear magnetic resonance and high-resolution mass spectrometer. The absorption and fluorescence studies were carried out by ultraviolet-visible and fluorescence spectrophotometers, respectively. Cell morphology was observed under an inverted microscope. Cytotoxicity test was detected by MTT assay. Cellular localization was observed by a confocal laser scanning microscope. Colony formation ability was carried out by colony formation assay. Cell migration ability was detected by transwell migration assay. Differences between the two groups were analyzed by two-tailed Student's t-test. The difference with P < 0.05 (*) was considered statistically significant. The compounds were synthesized in high yield. The λmax and Stokes shift of these compounds reach up to 567 and 150 nm, respectively. These compounds exhibited good antiproliferative activity against lung cancer cells, with compound 3h exhibiting the best IC50 of 13.1 ± 2.7 μM. Furthermore, the selected compound 3h is located preferentially in lysosomes and a small amount in nuclei, effectively inhibiting cell colony formation and migration abilities toward A549 cells. These findings suggested that nitrogen mustard-based fluorophores might be a potential effective chemotherapeutic agent in lung cancer therapy.

A series of boron difluoride complexes of azinylcarbazoles: synthesis and structure-property relationships.

A series of boron difluoride (BF2) complexes of azinylcarbazoles 1b-1h were synthesized, and the effects of the structure of azine moieties on the photophysical and electrochemical properties of the BF2 complexes were clarified. UV-vis analysis of 1b with quinoline, 1c with isoquinoline, and fully fused 1d revealed that fusion with a benzene ring to a pyridylcarbazole BF2 complex (1a) resulted in red shifts of longest-maximum absorption wavelengths (λmax). UV-vis analysis of 1e and 1f with pyrimidine, 1g with pyridazine, and 1h with pyrazine revealed that substitution of a carbon atom to a nitrogen atom in 1a also resulted in red shifts of λmax. The fluorescence quantum yields (Φf) decreased from 1a to 1b-1h, and especially, the fluorescence of 1e, 1g, and 1h was quenched in solution. At 77 K, the emission intensities of 1b-1h were significantly increased compared with those at ambient temperature, and they also exhibited phosphorescence with relatively narrow energy gaps between the singlet and triplet excited states. These results on the emission at 77 K indicate that the quench of fluorescence from 1e, 1g, and 1h at ambient temperature originates from both internal conversions and intersystem crossing. In the solid state, all of the complexes including 1e, 1g, and 1h exhibited emission. Distinctive aggregation-induced emission properties were observed for 1e-1h. Electrochemical measurements revealed that the replacement of the pyridine moiety in 1a with azine moieties reduced electrochemical gaps mainly due to a decrease in the LUMO levels. The effects of azine moieties on electronic structures were also discussed based on theoretical calculations.

Extraction of Anthocyanins from Black Grape By-Products and Improving Their Stability Using Cobalt(II) Complexation.

This study was conducted to investigate the effect of cobalt complexation on the spectral properties of anthocyanins (AC) extracted from black grape pomace (Black Magic) and the effect of complexation on the pH stability of AC during storage. Initially, cobalt acetate tetrahydrate aqueous solution was complexed with AC crude extract and diluted separately in buffer solutions with different pH (3.5, 4.5, 5.5, and 6.5). Afterward, spectral changes were determined spectrophotometrically. pH stability was investigated using the same buffer solutions and stored for 7 days in the dark at room temperature, and the absorbance of each solution was measured daily using a spectrophotometer. Results indicated that complexation caused similar hypsochromic and hyperchromic shifts in λmax at all pH values. With regard to pH stability, the degradation of complexed AC followed first-order reaction kinetics causing half-lives to increase up to 80-fold as compared with noncomplexed AC, which was due to the sharp decrease in K (per day), indicating an improved pH stability as compared with noncomplexed AC. Therefore, Co(II) could be used in the stabilization of grape AC for the coloration of a wide range of foods and food products at near-neutral pH environments considering the health benefits of grape AC and the maximum nontoxic dose of Co(II) salt.

Facile synthesis of CdO-ZnO heterojunction photocatalyst for rapid removal of organic contaminants from water using visible light

The synthesis of an efficient photocatalyst for removing organic contaminants in the water is of major importance for researchers working in heterogeneous photocatalysis. To do this, we provide the co-precipitation approach for synthesizing heterojunction nanocomposite (CdO-ZnO). Standard analytical techniques were used to characterize the synthesized components. According to the XRD and DRS results, a composite of ZnO and CdO was effectively synthesized with a shift of λmax towards the higher wavelength. SEM pictures reveal well-decorated oval-shaped CdO nanoparticles with hexagonal ZnO particle morphology. Under visible light irradiation, the as-prepared CdO-ZnO nanocomposite demonstrated very efficient photocatalytic performance as measured by the decomposition of RhB, MB, paracetamol, and ciprofloxacin in an aqueous solution. The photo-mineralization of MB and RhB over the most active CZ-3 catalyst was also assessed by measuring the decrease in TOC (total organic carbon) content over time when exposed to visible light. The breakdown of paracetamol produces no hazardous by-products, according to high-performance liquid chromatography (HPLC) study. The photocatalytic process appears to be dominated by OH and h+, according to the radical scavenger tests.

Effects of electron beam irradiation pretreatment on the structural and functional properties of okara protein

The structural and functional properties of okara protein pretreated with electron beam irradiation (EBI) at different doses (0–10 kGy) were investigated. The results of Fourier transform infrared spectroscopy spectra and fluorescence spectra indicated that EBI treatment decreased the α-helix and β-sheet proportion, contributing to a less compact tertiary conformation, thereby increased the fluorescence intensity with a red shift of λmax. Scanning electron microscopy images indicated that okara protein was fragmented into smaller pieces and the surface was uneven with pores after EBI treatment. The solubility, thermal stability and emulsification characteristics of okara protein were regulated by modifying its structure by EBI treatment. When the EBI treatment dose was 6 kGy, the protein had the highest solubility, as well as emulsification characteristics. Taken collectively, these results demonstrate that EBI can improve the functional properties of okara protein, which may widen the application of the protein.

Fluorescent chemosensors containing ruthenium(II) bipyridine as fluorogenic unit and modified calix[4]arene as ionophore: Synthesis, characterization, electrochemistry and ion-binding property

A series of metallo-receptors containing ruthenium(II) bipyridine moiety as signaling unit and calix[4]arene coupled with azacrown as ionophore have been synthesized and characterized. These molecules exhibit metal to ligand charge transfer (MLCT) absorption band at 456 nm and 3MLCT luminescence band at 614 nm. Electrochemical study revealed that the Ru(II) of these complexes oxidize in the potential range + 1.23 to + 1.30 V and the ligands exhibit three redox waves in the potential −1.36 to −1.89 V. Ion-binding property of these molecules has been studied using a large number of metal ions and anions with the aid of luminescence spectral change, which revealed that all of the three receptors bind Hg2+ and Pb2+ strongly, as evident from the enhancement in emission intensity with red shift of λmax. Among anions, H2PO4− and F− exhibited substantial quenching in emission intensity, suggesting their strong interaction with the receptors. To evaluate the binding constants (Ks), luminescence titration of the receptor molecules with the strongly interacting ions have been performed and the Ks values have been calculated from the titration data. The Ks values are in the range 4.77 × 104 to 1.20 × 103 M−1 with descending order of Hg2+ > Pb2+ > H2PO4− > F−. For anions, 1H NMR spectral change were recorded with incremental addition of anions, the results obtained are discussed in light of ion-binding property and mechanism of interaction.

Cadmium(II) and copper(II) complexes containing benzoate derivatives and 2-aminopyrimidine ligands: Synthesis, crystal structures and antibacterial activity

The new Cd(II) and Cu(II) complexes namely [Cd2(2-OHbza)4(apm)4] (1), [Cu2(2-OHbza)4(apm)]n•2(2-OHbza) (2) and [Cu2(2-CH3bza)4(apm)]n (3) (2-OHbza = 2-hydroxybenzoate, 2-CH3bza = 2-methylbenzoate and apm = 2-aminopyrimidine) were successfully prepared by using direct one pot synthesis method. All complexes were characterized by using CHN elemental analysis, FT-IR spectroscopy, powder X-ray diffraction and single crystal X-ray diffraction techniques. Compound 1 crystallized in monoclinic space group P21/c, while compound 2 and 3 crystallized in triclinic space group P-1. The dinuclear compound 1 consists of two seven-coordinated Cd(II) centers which are doubly bridged by 2-OHbza bridging ligands, while the rest two 2-OHbza and two apm are terminal ligand. The crystal structure of compound 1 is stabilized by the intermolecular hydrogen bonding and C-H•••π interaction and π•••π interactions. Compounds 2 and 3 present zigzag one-dimensional chainlike-structure which dimer Cu(II) units are linked by apm ligand. The crystal structure of these compounds is stabilized by π•••π and C-H•••π interactions. The photoluminescence properties of compound 1 has been studied comparing to those of 2-OHbza and apm ligands. The solid state PL emission spectrum of compound 1 shows similar intensity of free apm ligand and shape to free 2-OHbza ligand which present a single broad band centered at λem 525 nm (λex = 325 nm), but blue-shift. For solution PL experiment of compound 1 in various solvents, the results showed that compound 1 is selective PL quenching acetone. Electronic spectra for solid state and solution in different solvents of compounds 2 and 3 present the d-d absorption bands centered in the range of 701 – 794 nm. The highest red shifts of λmax are found for compounds 2 and 3 in DMSO. In addition, the antibacterial activity of all compounds are investigated for S.aureus and E.coil by agar diffusion method. The results show that compound 1 exhibits the activity against S.aureus better than E.coil.

Tuning optoelectronic properties of carbazole through substituent effect: TD-DFT investigation

π-conjugated organic materials such as carbazoles have attracted much attention because of their applications in electronic devices such as OLED’s, solar cells and sensors. Due to their optoelectronic properties, high charge carrier mobility, suitable band gaps and orbital energies, carbazoles have received immense attention to serve as a potent photosensitizer for obtaining high performance in DSSC. The present QSPR study of substituted carbazole and carbazole anion with electron donor (NH2) and acceptor (NO2) substituents at various positions is done by the density functional theory (DFT) calculations at B3LYP/6-31G(d,p) level. The longest maximum absorption wavelengths (λmax) in vacuum as well as in polar (acetonitrile) and non-polar (benzene) solvents are studied by using the time-dependent density functional theory (TD-DFT). For the singly substitution of NH2 (at C3) and NO2 (at C4) groups to the carbazole and its anion, the λmax values are observed to be shifted to the longest wavelength from 290.56 nm to 325.73 and 375.77 nm than the other respective positions. Whereas, the respective λmax values for carbazole-anion are found at 384.28 and 590.53 nm respectively. For disubstituted carbazole with NH2 and NO2 at C3 and C4 positions, the longest λmax shifts to 477.15 nm and for carbazole-anion the longest λmax obtained at C4 (NH2) and C5 (NO2) positions with λmax value 694.61 nm. Similar observations are also found in acetonitrile and benzene solvents. Further, it is observed that as the λmax increases, the HOMO-LUMO energy gap (EHL) value decreases accordingly which can be attributed to intramolecular charge transfer from NH2 to NO2 groups. A very good correlation of λmaxwith EHL is observed with correlation coefficient between 0.91 to 0.95 in vacuum as well as in acetonitrile and benzene solvents. Present study may provide valuable guidelines for the choice of suitable substituent to design carbazole moieties as efficient photosensitizer in DSSC. Copyright © 2017 VBRI Press.

Introducing Distinct Structural and Optical Properties into Organotin Sulfide Clusters by the Attachment of Perylenyl and Corannulenyl Groups.

We report the introduction of distinct optical properties into organotin sulfide clusters by the attachment of extended polycyclic aromatic organic molecules. This was realized by the reactions of [(RNSn)4S6] (RN = CMe2CH2CMeNNH2) with 3-perylenecarbaldehyde and corannulenecarbaldehyde, respectively. The reaction with the first reactant leads to the formation of two products [(RperylSn)3S4][SnCl3] [1a; Rperyl = CMe2CH2CMeNNCH(C20H11)] and [(RperylSn)3S4Cl] (1b). Structural differences between these two compounds are reflected in their different optical absorption and luminescence behavior, yet in both cases, the main emission is red-shifted relative to 3-perylenecarbaldehyde. The second organic molecule affords the compound [(RcorSn)4Sn2S10] [2; Rcor = CMe2CH2CMeNNCH(C20H9)] with intriguing optical properties, including a broad emission with essentially no shift in λmax compared to corannulenecarbaldehyde. All compounds were obtained as single crystals, and their structures were determined by means of single-crystal X-ray diffraction. The optical properties of the highly luminescent compounds were investigated by means of emission and time-resolved photoluminescence spectroscopy measurements.