Shift Of Absorption Band Research Articles

Anion effect on crystal structure of Zn-complexes of spironaphthopyran and their chromogenic properties in solution

Effect of the anion nature on crystal structure of Zn-complexes of spironaphthopyran and their chromogenic properties in solution were studied. Complexes with zinc chloride and zinc picrate exhibited tertahedral and octahedral coordination environment of the metal ion respectively. The structure of the complex with zinc picrate demonstrates a rare example of the co-crystallization of two types of complexes differing in the number of coordinated picrate anions. The composition, stability, and absorption properties of zinc complexes in acetone essentially depend on the counter anion nature. When the coordinating ability of the counter ion increases in the range BF4−, ClO4−, NO3–, Pic−, I−, Cl−, CH3COO–, (CH3)3CCOO– the complex stability is reduced from logK = 8.7 to 2.96. This is accompanied by the chromogenic effect which is related to the decrease in the spectral shift of the long-wavelength absorption band of the complex relative to the merocyanine ligand from 846 up to 168 cm−1. The complex photo-initiated processes include fluorescence and thermally reversible dissociation. Fluorescence is characterized by band maxima in the 622–637 nm region and normal Stokes shifts of 1087–1454 cm−1 with an efficiency being weakly dependent on the anion nature. In contrast, the negative photochromism of the complexes demonstrates a significant dependence of the photo-bleaching efficiency on the anion nature in the range 0.012–0.17. The presence of a chromogenic photochromic effect along with fluorescence makes it possible to consider the complex as fluorescent switch.

A Bright Surprise: Live‐Cell Labeling with Negatively Charged Fluorescent Probes based on Disulfonated Rhodamines and HaloTag

AbstractDisulfonated rhodamines are photostable and bright dyes widely used in life science and optical microscopy. However, di‐sulfonated dyes were considered cell impermeable and not applicable in living cells. We challenged this assumption with 5 most popular rhodamines (Rho) having two carboxylic acid residues, versatile sulfonation patterns and emitting green (AS488), yellow (Rho530), orange (Rho565) and red (Rho590 and STAR RED) light. The probes comprising one rhodamine entity and a HaloTagTM amine (O2) ligand (x) were prepared and applied for labeling of living, Vimentin‐Halo (VIM‐Halo) expressing U‐2 OS cells. Surprisingly, we observed specific and bright staining with simplest compounds Rho590‐x, Rho565‐x and Rho530‐x bearing two negative charges; they performed well also in stimulated emission depletion (STED) microscopy. Specific staining and red shifts in absorption and emission bands were observed with other probes having one negative charge; they were prepared by native chemical ligation and esterification.

Theoretical study of lithium oxide clusters adsorbed on anatase TiO2 surface

The search for materials that have broad applicability as photocatalysts is growing interest. Titanium dioxide (TiO2) is a semiconductor with demonstrated photocatalytic properties, and its improvement with lithium oxide (LO) adsorption (LO-TiO2) is investigated using density functional theory (DFT). The modeling of the electronic structure of three types of LO as lithium oxide (Li2O)n, lithium peroxide (Li2O2)n, and lithium superoxide radical (LiO2)n (n = 1,2,3) adsorbed on anatase TiO2 shows an increase in their reactivities. The bandgap energy decreases in the range of 3.07–0.33 eV compared to TiO2 (3.2 eV) and conducting states from LO and 2p orbital of O(TiO2) towards 3d orbital of titanium (TiO2) are generated. The Independent Gradient Model and the intrinsic bond strength index are applied to gain insight into the intermolecular interactions between LO and TiO2. These results are coherent with that predicted by the interaction energy of LO-TiO2, which suggests that the more stable systems are (Li2O)2 and (Li2O2)3. Optical properties calculated with TD-DFT show a visible shift of the main absorption band compared to TiO2. The theoretical results show that the adsorption of lithium oxide onto a TiO2 surface would be an excellent strategy to produce a material as a visible light-activated photocatalyst.

Spin-Resolved Band Structure of Hoffman Clathrate [Fe(pz)2Pt(CN)4] as an Essential Tool to Predict Optical Spectra of Metal–Organic Frameworks

Paramount spin-crossover properties of the 3D-Hoffman metalorganic framework (MOF) [Fe(pz)2Pt(CN)4] are generally described on the basis of the ligand field theory, which provides adequate insight into theoretical and simulation analysis of spintronic complexes. However, the ligand field approximation does not take into account the 3D periodicity of the actual complex lattice and surface effects and therefore cannot predict a full-scale periodic structure without utilizing more advanced methods. Therefore, in this paper, the electronic properties of the exemplar MOF were analyzed from the band structure perspective in low-spin (LS) and high-spin (HS) states. The density-of-states spectra determined for both spin-up and spin-down electrons of Fe d6 orbitals indicate spin-orbital splitting and delocalization for HS due to spin polarization in the iron atom ligand field. Presence of the surface states in the real crystal causes a red shift of the metal-metal charge transfer (MMCT) and metal-ligand charge transfer (MLCT) peaks for both HS and LS states. The addition of residual water molecules and disorder among the pyrazine rings reveal additional influences on the positions of the pyrazine band and, therefore, on the absorption spectra of the crystal. The results show a magnification of the peak correlated with the MLCT in the HS state and a significant red shift of the LS characteristic absorption band. The presented approach involving band structure analysis delivers a more complete image of the electronic properties of the [Fe(pz)2Pt(CN)4] crystalline network and can be a landmark for insightful studies of other MOFs.

Tuning the UV absorbing ability of CeO2 nanoparticles with F− doping

Ultraviolet (UV) absorbing material is the key to achieving high performance UV shielding device. Because of the large absorption ability on UV light and excellent long-term stability under UV irradiation, CeO2 nanoparticle is considered potential UV absorber for practical applications. However, the CeO2 related materials still face challenges since its UV absorbing capability is non-adjustable, which is unable to meet the changing requirement. In this work, we obtain serial CeO2 nanoparticles with tunable UV absorbing ability through F− doping. Using un-doped CeO2 nanoparticles with size of about 6 nm as starting material and trifluoroacetic acid as F− source, serial F− doped CeO2 marked as CeO2:F1, CeO2:F2, CeO2:F3 and CeO2:F4 are obtained through a post- fluorination strategy. The F− doping rarely changes the size of CeO2, but obviously changes the optical absorbing ability. As the F− content increases, the optical absorption band of the F− doped nanoparticles gradually shifts to short wavelength. Because of the highest F− content, CeO2:F4 sample displays the greatest blue shift with an absorption band of 345 nm. Calculation result reveals that the introduction of F− enlarges the energy band gap of CeO2, leading to the blue shift of the UV absorption band. Finally, serial coated glasses with tunable UV shielding ability are prepared. Using CeO2 nanoparticles or F− doped CeO2 nanoparticles as UV absorber, the optical absorption band of coated glasses could be tuned between 380 nm and 345 nm.

PHYSICOCHEMICAL PROPERTIES AND COMPOSITION OF LIPID COMPONENT FROM WINTER GARLIC BULBS (ALLIUM SATIVUM L.)

The lipid composition, presence of the biologically active substances and ability of lipids to the spontaneous aggregation in the water medium of the winter garlic (Allium sativum L.) was studied by TLC, UV-spectrometry with the Gauss mathematic analysis of spectra and dynamic light scattering methods It is shown that share of the more easily oxidizable fractions in the garlic phospholipids is 2.45 times greater than that for the more poorly oxidizable fractions. Mathematic analysis of the UV-spectra of the lipids solution in chloroform revealed the presence of compounds with a conjugated couple bonds and ketodienes and confirmed the literature data about absence of flavonoids. The hydrophilic biologically active compounds are found in a polar phase during extraction of lipids. Analysis of UV-spectrum of 20-hydroxyekdizone in chloroform which is detected in the garlic lipids was done. It was determined the substantial maximum absorption band shift of sterols in UV-spectra of the garlic lipids testifies to their participation with sphigolipids in the raft formation that is due to form of particles with the average diameters 160 nm and the low absolute value of ξ-potential from the garlic lipids in the water medium.

COMBINATION OF METHODS FOR DETERMINE THE AUTHENTICITY OF HERBS THYMUS SERPYLLUM AND THYMUS MARSHALLIANUS

Relevance. Authentication of crushed medicinal plant raw materials (RM) is an actual issue because there are species similar in morphology or there is a possibility of interspecific hybridization. The characteristics of the absorption spectra of extracts and their chromatographic profile are significant indicators of the authenticity of RS. The aim of the study was a comparative analysis by TLC and spectrophotometry of water-alcohol extracts from the herb Thymus marshallianus Willd. (TM) and Thymus serpyllum L. (TP). Material and methods. Water-alcohol extracts were obtained from 1.0 g of RS (exact suspension) in two ways (extractant – 70% ethanol, heating in a boiling water bath; extractant – 50% ethanol, 20–22 °C). Absorption spectra were recorded in the range of 200–500 nm. Eluent – ethyl acetate : formic acid anhydrous : water (70:15:15) was used for chromatography. Detection of adsorption zones was carried out after treatment with a 5% alcohol solution of AlCl3 at 365 nm. Rutin, quercetin and cinaroside were used as standard samples. Results. Microscopic analysis revealed diagnostic signs of the TM and TP leaf – trichomes of various types. The absorption spectra of water-alcohol extracts from TM and TP (obtained with 50% and 70% ethanol) have two pronounced maxima. When AlCl3 is added, a bathochromic shift of the long-wavelength absorption bands is observed. The chromatograms of these extracts revealed a yellow zone at the level of cinaroside, and differences in the number and color of the adsorption zones of TM and TP extracts. Conclusion. The absorption spectra of water-alcohol extracts have two pronounced maxima for TP of the same intensity, for TM – different. The intensity of differential absorption spectra of water-alcohol extracts of TM is higher, which indicates a higher content of flavonoids in its extracts. Cinaroside was detected in TM and TP extracts by TLC, while 11 adsorption zones are distinguishable on the chromatogram of extracts from TM herb, and 9 from TP.

A water-soluble colorimetric and ratiometric fluorescent probe based on phenothiazine for the detection of hypochlorite ion

A new water-soluble colorimetric and ratiometric fluorescent probe for detecting hypochlorite ion (ClO−) based on a phenothiazzine group was designed and synthesized. As ratiometric fluorescent probe, LD-Lyso showed rapid, accuracy, and selective fluorescence sensing effect for ClO− in PBS buffer solution with a large Stokes shift (195 nm), it displayed a significant blue-shift phenomenon and a 25-fold enhancement of the fluorescence intensity ratio (I550/I635) toward ClO−, fluorescence notably changing from red to green, the detection limit as low as 8.74 μM; As colorimetric probe, LD-Lyso also showed a significant shift in absorption band (from 450 to 395 nm) upon treatment with ClO− along with the visible color changed from faint yellow to colorless, the detection limit as low as 0.01 μM. In addition, the detecting mechanism of LD-Lyso towards ClO− via the intramolecular charge transfer (ICT) mechanism was proved by ESI-MS and DFT calculation, and the application as testing strips for detecting ClO− was realized.

Tamed synthesis of AgNPs for photodegradation and anti-bacterial activity: Effect of size and morphology

Organic dyes present in the effluents of paints, and textile industries are posing major environmental threats. Rapid decomposition of these dyes using non-toxic, renewable and cost-effective silver nanoparticles (AgNPs) is a pragmatic strategy. Therefore, in current research work, AgNPs with different size ranges have been prepared following the polyol reduction method by controlled exploitation of substrate/reducing agent molar ratio and pH of reaction media. AgNPs have been characterized by UV–Visible spectroscopy, Scanning Electron Microscope (SEM), Powder X-Ray Diffraction (XRD) and Energy Dispersive X-ray spectroscopy (EDS). Absorption peaks ranging from 420 to 465 nm confirmed the synthesis of AgNPs using surface plasmon resonance (SPR) bands. The increase in molar ratio and pH led to the blue shift in absorption bands which revealed the size reduction of AgNPs. XRD analysis confirmed the crystallite size (16–21 nm) and Face centered cubic (FCC) crystalline structure of AgNPs. EDS was utilized to check the purity of AgNPs. SEM confirmed the spherical morphology of AgNPs with a size range between 70 and 110 nm. The energy band gap was determined using the Tauc plot equation to correlate the catalytic properties of NPs with size. Different-sized AgNPs were utilized as photocatalysts for the degradation of Methylene blue (MB) dye under sunlight irradiation. AgNPs having an average size of 70 nm showed improved photocatalytic potential by 94% degradation of MB in 80 min. The AgNPs were also evaluated for their antibacterial activities against gram-positive and gram-negative strains of bacteria. Small-size AgNPs were found more active against gram-negative strains of bacteria.

Naphthalene Phthalimide Derivatives as Model Compounds for Electrochromic Materials.

Electrochromism of organic compounds is a well-known phenomenon; however, nowadays, most research is focused on anodic coloring materials. Development of efficient, cathodic electrochromic materials is challenging due to the worse stability of electron accepting materials compared with electron donating ones. Nevertheless, designing stable cathodic coloring organic materials is highly desired-among other reasons-to increase the coloration performance. Hence, four phthalimide derivatives named 1,5-PhDI, 1,4-PhDI, 2,6-PhDI and 3,3'-PhDI were synthesized and analyzed in depth. In all cases, two imide groups were connected via naphthalene (1,5-PhDI, 1,4-PhDI, 2,6-PhDI) or 3,3'-dimethylnaphtidin (3,3'-PhDI) bridge. To observe the effect of chemical structure on physicochemical properties, various positions of imide bond were considered, namely, 1,5- 1,4- and 2,6-. Additionally, a compound with the pyromellitic diimide unit capped with two 1-naphtalene substituents was obtained. All compounds were studied in terms of their thermal behavior, using differential calorimetry (DSC) and thermogravimetric analysis (TGA). Moreover, electrochemical (CV, DPV) and spectroelectrochemical (UV-Vis and EPR) analyses were performed to evaluate the obtained materials in terms of their application as cathodic electrochromic materials. All obtained materials undergo reversible electrochemical reduction which leads to changes in their optical properties. In the case of imide derivatives, absorption bands related to both reduced and neutral forms are located in the UV region. However, importantly, the introduction of the 3,3'-dimethylnaphtidine bridge leads to a noticeable bathochromic shift of the reduced form absorption band of 3,3'-PhDI. This indicates that optimization of the phthalimide structure allows us to obtain stable, cathodic electrochromic materials.

Light-controlled detection of aromatic carboxylate anions using doubly fused naphthopyran derivative

A photochromic naphthopyran derivative, 2,2,11,11-tetraphenyl-2,11-dihydrobenzo[f]pyrano[3,2-h]chromene has been synthesized and its structure was confirmed using various spectroscopic techniques like NMR, infrared spectroscopy (FT-IR), high-resolution mass spectroscopy (HR-MS) and single crystal X-ray diffraction (SCXRD). The synthesized probe has shown a sensitive signal toward salicylic acid and 3,5-diaminobenzoic acid in acetonitrile: water (50:50(v:v)) solvent system at pH 7.6 (1 mM Tris buffer). UV–vis and fluorescence spectroscopic analyses revealed complex formation between these carboxylate anions and the synthesized photochromic probe, with blue shifts in absorption bands & enhancement in fluorescence intensity. Furthermore, photo-switching for the naphthopyran derivative in presence of both carboxylic acids was performed using 365 nm UV light, and results obtained indicated that the release and binding of these carboxylic acids can be controlled using 365 nm UV light. As expected, the fluorescence analysis provided a better limit of detection value as compared to the UV–Vis analysis. Fluorescence spectroscopy yielded a detection limit of 16.29 nM for salicylate ions using the naphthopyran-based probe.

Rhodobacter sphaeroides as a model to study the ecotoxicity of 1-alkyl-3-methylimidazolium bromide.

The purple non-sulfur bacterium Rhodobacter sphaeroides was selected as a biological model to investigate its response to the toxicity of 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br), a type of ionic liquid (IL), with different alkyl chain lengths (n describes the number of carbon atoms in the alkyl chain). The inhibition of bacterial growth by [Cnmim]Br was positively correlated with n. Morphological characterization revealed that [Cnmim]Br caused cell membrane perforation. The signal amplitude of the electrochromic absorption band shift of endogenous carotenoids showed a negatively linear correlation with n, and the amplitude of the blue-shift of the B850 band in light-harvesting complex 2 showed a positively linear correlation with n. Furthermore, an increase in blocked ATP synthesis and increase in antioxidant enzyme activity were observed in chromatophores treated with ILs containing longer alkyl chains. In summary, the purple bacterium can be developed as a model to monitor ecotoxicity and examine the mechanism of IL toxicity.

Effects of SbCl5, Ethylamine, Imidazole and 2-Methylimidazole on Redox and Structural Behaviours of Manganese(III) meso-5,10,15,20-tetrakis(4-pyridyl)porphyrin

A porphyrin compound manganese(III) meso-5,10,15,20-tetrakis(4-pyridyl)porphyrin, Mn(Py)4P containing manganese(III) and 4-pyridyl ligands was synthesized. The UV-visible spectrophotometry and cyclic voltammetry were used to investigate the axial ligand and the redox behaviours of Mn(Py)4P. This study investigates the reduction properties of Mn(Py)4P using primary amine, imidazole and 2-methylimidazole as axial ligands. Reduction of Mn(Py)4P leads to a shift in absorption bands, indicating the conversion from manganese(III) to manganese(II) porphyrin. The addition of primary amine results in a square pyramidal structure for Mn(II) porphyrin, while imidazole or 2-methylimidazole leads to the formation of tetragonal complexes. These changes in geometry result in a decrease in π-bonding. The observed spectral patterns support the involvement of axial ligands in the 5th and 6th positions of manganese(III) porphyrin. The cyclic voltammogram confirmed the alteration in geometry, indicating changes in the redox properties of compound. As a whole, the results of this study provide light on the ways where the behaviour of in which Mn(Py)4P can be altered by the presence of other molecules.

A novel and sensitive ratiometric fluorescent quantum dot-based biosensor for alkaline phosphatase detection in biological samples via the inner-filter effect.

Alkaline phosphatase (ALP) is an important biomarker whose abnormal level in activity is associated with hepatobiliary, skeletal, and renal diseases as well as cancer. Herein, we synthesized ZnSe@ZnS quantum dots (ZnSe@ZnS QDs) and Mn-doped ZnS quantum dots (Mn:ZnS QDs) as fluorophores to establish the ratiometric fluorescent assay for ALP activity detection in biological samples. p-Nitrophenyl phosphate (PNPP) was used as a substrate for ALP, and the overlaps between absorption spectra of PNPP and excitation spectra of QDs resulted in sharp fluorescence quenching. Under the catalysis of ALP, PNPP was hydrolyzed into p-nitrophenol (PNP), which caused a red shift of absorption band of PNPP and fluorescence recovery of Mn:ZnS QDs (585 nm). However, the overlaps between absorption spectra of PNP and emission spectra of ZnSe@ZnS QDs led a further quenching of ZnSe@ZnS QDs (405 nm). Therefore, the ratiometric fluorescent signals (F 585/F 405) were associated with activity of ALP based on bidirectional responses of QDs to the concentration of PNPP. Under the optimum conditions, the method exhibited a good linear relationship from 4 to 96 U per L (R 2 = 0.9969) with the detection limit of 0.57 U per L. Moreover, the method was successfully applied for detecting the ALP activity in a complex biological matrix (human serum and HepG2 cells) with impressive specificity. In particular, the complicated chemical modifications of QDs and pretreatments of biological samples were not required in the whole detection procedures. Therefore, it not only provided a sensitive, specific and simple approach to clinical ALP activity detection, but it also provided support for early diagnosis of diseases.

NIR emitting BODIPY dyes for pH sensing

The ease of functionalization of BODIPY dyes provides scope for preparing pH indicators by introducing suitable functional groups. In this work, two dimethylamino substituted BODIPY dyes 3 and 4 with styryl and phenylbuta-1,3-dienyl groups introduced at the 3,5-positions were synthesized, characterized, and studied for use as pH indicators. Incorporation of the electron-rich vinylene substituents yielded dyes that absorb in the NIR region with emission wavelengths of 796 and 797 nm for 3 and 4, respectively, in dimethylsulfoxide (DMSO). Time-dependent density functional theory (TD-DFT) calculations were performed to study the effect of adding an extra alkene bond in 4 on the photophysical properties. The extra alkene bond in 4 resulted in a 3 nm shift in the main NIR region absorption band, lower molar extinction coefficient values, higher emission wavelength, and a decrease in fluorescence quantum yield in all solvents studied. Upon protonation of the amino groups, a large blue shift is observed in both the absorption and emission wavelengths, along with an increase in the fluorescence quantum yields and longer fluorescence lifetimes. The [Formula: see text] values for 3 and 4 were estimated to be 2.9 (± 0.05) and 1.2 (± 0.05), respectively.

Synthesis and Studies of Fused Benzo-Benzisapphyrins.

A series of rare examples of fused benzo-benzisapphyrins were synthesized readily by (3 + 2) condensation of benzodipyrrole-derived diol and para-benzitripyrrane in the presence of 0.5 equiv of TFA in CH2Cl2 under inert atmosphere conditions accompanied by DDQ oxidation in open air. The crude compounds were separated by basic alumina column chromatography and afforded pure fused benzo-benzisapphyrins in 20-22% yields. The fused sapphyrins were characterized in detail by high-resolution mass spectrometry (HRMS) and one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy. The 1H NMR spectra recorded at both 298 and at 233 K clearly exhibited the presence of a strong diatropic ring current in benzo-benzisapphyrins, and the macrocycles are of aromatic nature. The DFT-optimized structure of benzo-benzisapphyrin revealed that the macrocycle was planar to a great extent due to the rigid structure of the dibenzopyrrole moiety, and the NICS(0) value of -11.2 ppm supports the aromatic nature of macrocycles. The absorption spectra of benzo-benzisapphyrins showed three weak Q bands approximately in the region of 650-900 nm and a strong Soret band at 480 nm, along with a shoulder band at ∼510 nm. The diprotonated derivative generated by the addition of excess TFA to the benzo-benzisapphyrin macrocycle exhibited bathochromically shifted absorption bands compared to the free base macrocycle.

Selenium-containing bodipy dyes as photosensitizers

“Boron-dipyrromethenes or BF2dipyrrins (BODIPY)“ are high fluorescent dyes and it is applicable in many fields for their attractive photochemical and photophysical properties. BODIPY has different sites of potential for its functional groups, where these groups can be functionalized and introduced. BODIPY can help in building blocks for the synthesization of the desired derivatives of BODIPY. The paper presents a series of existing literature on the given topic to obtain the required information for further studies. It presents that BODIPY could be utilized to wash the living cells for sensing the temperature and fluorescence imaging, in addition to that it also presents an increase of water solubility for increasing the efficiency. Different methods are utilized for the preparation of Selenium BODIPY, 2–1 pot procedure that follows the DDQ oxidation process. One of the most commonly used approaches for synthesis is the pyrrole condensation with aldehydes and the reaction within it is performed with the help of chromatography. BODIPY dyes are able to note their absorption band and stoke shifts for functionalized polymers for systems for light harvesting in solar cells. The dyes holds fluorescence molecules with relevant chemical and physical characteristics for both thermal and chemical stabilities. The substance possess low polarity and pH elements with low sensitivity and PDT as a photosensitizer. The applications of BODIPY hold sharp absorption and visible fluorescence, easy to use synthetization, ”high absorption coefficient“, and stable chemical and thermal properties. Lastly, it can be seen that BODIPY are able to produce dyes quickly and easily.

Elucidating the nanostructure of small interfering RNA-loaded lipidoid-polymer hybrid nanoparticles

We analyzed the structural and material properties of small interfering RNA (siRNA)-loaded lipid-polymer hybrid nanoparticles (LPNs) containing ionizable lipidoid and poly(dl-lactic-co-glycolic acid) (PLGA) using small-angle X-ray scattering, cryogenic transmission electron microscopy, polarized light microscopy, the Langmuir monolayer methodology, differential scanning calorimetry, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Scattering analyses showed that bulk lipidoid self-assemble into lamellar structures with a d-spacing of 38 Å, whereas lipidoid-siRNA lipoplexes display an in-plane lateral organization of siRNA in between lipidoid bilayers with a repeat distance of approximately 55 Å. The siRNA-loaded LPNs adopted a core–shell structure with an interaxial alignment of siRNA between lipidoid shell bilayers. Langmuir monolayer experiments showed a distinct interaction between the lipidoid headgroups and siRNA, which was dependent on buffer subphase pH. Thermal analyses suggested that PLGA and lipidoid interact, which was evident from a shift in the phase transition temperature of lipidoid, and the thermotropic phase behavior of lipidoid was affected by inclusion of siRNA. ATR-FTIR data confirmed the shift or disappearance of characteristic absorption bands of siRNA after lipidoid binding. In conclusion, siRNA-loaded LPNs display a core–shell structure, wherein the polymeric core functions as a colloid matrix support for siRNA-loaded lipidoid shell layers.

Synthesis and Studies of Di(p-Benzi)Decaphyrin and Di(9,10-Anthracenyl)Decaphyrin.

Two novel macrocycles, di(p-benzi)decaphyrin and di(9,10-anthracenyl)decaphyrin have been synthesized by condensing appropriate p-phenylene based pentapyrrane or 9,10-anthracenyl based pentapyrrane with pentafluorobenzaldehyde under acid catalyzed conditions. The pentapyrrane precursors were synthesized over sequence of steps starting with commercially available 1,4-dibromobenzene and 9,10-dibromoanthracene. The decaphyrin macrocycles were freely soluble in common organic solvents and characterized and studied by HR-MS, 1D and 2D NMR, absorption, cyclic voltammetry and computational techniques. The 1 H NMR spectra of both decaphyrins were almost similar with very few resonances, indicating their symmetrical nature in solution and the position of chemical shifts of various protons supports nonaromatic nature of decaphyrins. The DFT optimized structures revealed that both decaphyrins showed a doubly twisted figure of eight conformation and the p-phenylene rings in di(p-benzi)decaphyrin and anthracenyl rings in di(9,10-anthracenyl)decaphyrin did not participate in π-delocalization with rest of the respective decaphyrin macrocycle. Both decaphyrins showed sharp intense band in the region of 400-500 nm and a broad band in the region of 600-900 nm. The absorption bands of di(p-benzi)decaphyrin were significantly red shifted compared to di(9,10-anthracenyl)decaphyrin. The protonated derivatives of decaphyrins generated by addition of TFA to the toluene solution of decaphyrins showed distinct changes in colour and absorption spectral bands. The redox studies indicated that both decaphyrins are electron rich and undergo easier oxidations. The electrochemical and computational studies revealed that HOMO-LUMO energy gap was less in di(p-benzi)decaphyrin compared to di(9,10-anthracenyl)decaphyrin supporting the bathochromic shifts of absorption bands in di(p-benzi)decaphyrin. TD-DFT studies were in agreement with the experimental observations.

π-Expanded pyrazinoporphyrins for photocatalysis: How many rings are required?

A series of π-expanded pyrazinoporphyrins were successfully prepared and tested as sensitizers for photocatalytic aerobic sulfides oxidation. 2,3-Diaminoporphyrin derivative was used as a key intermediate for the preparation of porphyrins fused with naphtho-, phenanthrene-, phenanthroline- and acenaphthoquinone fragments and the structures of the obtained compounds were proved by detailed analysis of NMR. The peculiarities and limitations of the condensation of diaminoporphyrin with a set of corresponding aromatic quinones were investigated. Gradual bathochromic shift of absorption bands was observed in the series of the prepared compounds, correlating with the gradual expansion of the macrocycle aromatic system. The photostability of the obtained photosensitizers was tested prior to their application as photocatalysts. The photocatalytic performance of the obtained π-expanded pyrazinoporphyrins was investigated in the aerobic oxidation of thioanisole and revealed the increase of the activity with the expansion of the π-system of the molecule. Complete conversion of the substrate and over 98% selectivity was achieved with 10−2 mol% catalyst loading, that correspond to turnover number (TON) ca. 10,000. The maximal TON = 89,000 could be reached with 10−3 mol% catalyst loading. The measurements of the singlet oxygen generation quantum yields along with the DFT analysis of perturbation of the molecular orbitals of the photosensitizers was performed. The latter analysis revealed the presence of orbitals with predominant localization either at porphyrin macrocycle or at peripheral polyaromatic part of the molecule, allowing to expect charge separation upon photoexcitation.