Isocyanurate containing periodic mesoporous organosilicas (ICS-PMO) without any post-modification was used as a novel heterogeneous catalyst for synthesis of tetrahydrobenzo[b]pyran derivatives via one‐pot three‐component condensation of aromatic aldehydes with malononitrile (or ethyl cyanoacetate) and dimedone. The catalyst was characterized by FT-IR Spectroscopy, TEM, SEM and BET techniques. Products were obtained in short reaction times with excellent yields in water under reflux conditions. The catalyst could be recycled and reused for several times without noticeably decreasing the catalytic activity.

Fluorescence imaging is an important tool in the diverse fields of biology, chemistry and medicinal sciences.¹ Fluorescent chemoprobes such as small synthetic molecules interact specifically with the targets of interest to induce the property of fluorescence.² Benzo[a]phenoxazines function as fluorescent probes with high emission maxima, good molar extinction coefficients and photochemical stability. Moreover, these compounds are also used for labeling of amino acids, proteins and also for staining gels in gel electrophoresis experiments.³

In connection with our research findings of benzo[a]phenoxazines along with their synthesis and various applications,^4,5 the current work describes the synthesis of new benzo[a]phenoxazinium chlorides possessing the (4,6-dichloro-1,3,5-triazin-2-yl)amino at 5-position of the polycyclic system. The photophysical studies in anhydrous ethanol and water medium will be discussed along with the determination of fluorescence quantum yield.

Hantzsch reaction is classified as a one-pot, three-component process for the synthesis of 1,4-dihydropyridine(DHP) and polyhydroquinoline(PHQ) derivatives. Typically, it is accomplished using an aldehyde, -dicarbonyls and ammonium acetate or ammonia at high temperature. PHQs are one of the most important classes of heterocyclic scaffolds providing major ligands for biological receptors. PHQs are source of some valuable drugs which have been prepared efficiently. For instance, they demonstrate activity for the treatment of angina pectoris, hypertension .Therefore, developing more efficient methods, working under mild conditions and using more environmentally acceptable catalysts is in high demand.

PEGs are commercially available, non-toxic, used as a green solvent and catalyst, thermally stable and inexpensive compared to conventional phase-transfer catalyst such as crown ethers. PEG helps in maintaining a neutral reaction. Organic synthesis in PEG under solvent-free conditions is significant in modern organic synthesis.

In recent years the research of sensors with good sensitivity and good selectivity in aqueous medium has been of great interest.¹ Chemosensors soluble in aqueous media are very interesting, because of the importance in revealing a number of biological processes, disease states and environmental pollutions.²

2,4,5-Triaryl-imidazoles are versatile compounds with application in medicine, due to their biological activity, and materials sciences, for their interesting optical properties. These properties can be tuned by careful selection of substituents at positions 2, 4 and 5: replacement of the aryl group by a heterocyclic group results in larger π-conjugated systems with improved optical properties for application in nonlinear optics, OLEDs, DNA intercalators, and chemosensors.³

In this communication, we report the synthesis of new phenanthroimidazoles, substituted at position 2 with (hetero)aryl groups of different electronic character, in order to evaluate their photophysical properties and chemosensory ability. The new derivatives were characterized by the usual techniques and a detailed photophysical study was undertaken. The evaluation of the compounds as fluorimetric chemosensors was carried out by performing titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations.

In recent years, remarkable research in photocleavable protecting groups (PPGs) has given rise to a variety of structures suitable for masking a broad range of chemically and biologically relevant molecules. These groups can be easily removed by irradiation at a suitable wavelength, releasing the desired active compound. Notice that for bioapplications the chosen wavelength must be harmless to cells, ideally as close as possible to the visible spectrum.

Among the most interesting PPGs are coumarin derivatives that generally present high molar extinction coefficients at high wavelengths, good stability and fast release rates. Furthermore, these molecules can display fluorescence that allows following the spatial distribution and depletion of the bioactive compound.

With the goal of evaluating the efficiency of 4-chloromethyl-7-bromocoumarin as phototrigger for amino acid neurotransmitters glycine and β-alanine, the corresponding ester conjugates were synthetized. Their irradiation at different wavelengths (254, 300, 350 and 419 nm) in a Rayonet RPR-100 photochemical reactor, in methanol/HEPES buffer (80:20) was carried out. The photolysis process was followed by HPLC with UV detection. Results will be discussed in comparison with those obtained when 4-chloromethyl-coumarin was used in the photorelease of glycine and β-alanine.

An efficient method for the synthesis of GO-chitosan bionanocomposite is demonstrated. Also, GO-chitosan is used as a green nanocatalyst in the synthesis of tetra-substituted imidazoles. This protocol has many advantages such as short reaction time, high yield, easy isolation of the catalyst and solvent-free conditions. We put upon Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analyzes for the confirmation of the nanocomposite production.

An efficient, one-pot multi-component procedure for preparation of 2-amino-3-cyano-4H-chromene-4-carboxylate and 2-amino-3-cyano-5H-pyrano[3,2-c]chromene-4-carboxylate using Fe₃O₄@SiO₂-NH₂ nanoparticles as a facile synthesized, easily recoverable and heterogeneous catalyst was investigated. Our silica-supported magnetic catalyst was characterized successfully by Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) analyses. No significant decrease in catalytic activity is another major point of this reusable nanocatalyst. On the other hand, in continuation of our interest in the application of new catalysts in organic synthesis via multi-component reactions (MCRs), herein, these worthy chromene derivatives were synthesized using ethanol as a green solvent in good to excellent yield by a capable catalyst.

Reactivity of 3-acetyl-4-methylthioquinolin-2(1H)-one (1) towards 1,2- and/or 1,4-diazanucleophiles has been studied under different reaction conditions. Condensation of key compound 1 with hydrazine, phenylhydrazine, hydroxylamine hydrochloride, semicarbazide and thiosemicarbazide was carried out in different media. It was found that the nature of products is extremely dependent on both reactivity of the reagent and the ambient conditions. Accordingly, the reaction regioselectivety led to different [1,2]diazolo and or [1,2,4]triazepino[b or c]quinoline derivatives in addition to open chain condensates which were transformed to either annellated heterocyclo[b or c] quinolines, in good yields. The structure of new products was established on basis of their analytical and spectral data.

The development of organic materials displaying high two-photon absorption (TPA) has attracted much attention in recent years due to a variety of potential applications in photonics and optoelectronics, such as three-dimensional optical data storage, fluorescence imaging, two-photon microscopy, optical limiting, microfabrication, photodynamic therapy, upconverted lasing, etc. The most frequently employed structural motifs for TPA materials are donor–pi bridge–acceptor (D–pi–A) dipoles, donor–pi bridge–donor (D–pi–D) and acceptor–pi bridge-acceptor (A–pi–A) quadrupoles, octupoles, etc. In this work we present the synthesis and photophysical characterization of quadrupolar heterocyclic systems with potential applications in materials and biological sciences as TPA chromophores. Indole is a versatile building block for the synthesis of heterocyclic systems for several optoelectronic applications (chemosensors, nonlinear optical, OLEDs) due to its photophysical properties and donor electron ability and 4H-pyran-4-ylidene fragment is frequently used for the synthesis of red light-emitting materials. On the other hand, 2-(2,6-dimethyl-4H-pyran-4-ylidene)malononitrile (1) and 1,3-diethyl-dihydro-5-(2,6-dimethyl-4H-pyran-4-ylidene)-2-thiobarbituric (2) units are usually used as strong acceptor moieties for the preparation of π-conjugated systems of the push-pull type. These building blocks were prepared by Knoevenagel condensation of the corresponding ketone precursor with malononitrile or 1,3-diethyl-dihydro-2-thiobarbituric acid. The new quadrupolar 4H-pyran-4-ylidene fluorophores (3) derived from indole were prepared through condensation of 5-methyl-1H-indole-3-carbaldehyde with the acceptor precursors 1 and 2, in the presence of a catalytical amount of piperidine. The new compounds were characterized by the usual spectroscopic techniques (UV-vis., FT-IR and multinuclear NMR - ¹H, ¹³C).

Research on renewable energy sources and sustainable development have been expanding considerably in order to decrease the consumption of fossil fuels and therefore reduce global warming and environmental pollution. Solar energy is an excellent source due to its inexhaustibility and cleanness, and can be directly transformed into electric energy through photovoltaics, namely the most promising organic solar cells.

Solar cells based on organic dye sensitizers (DSSCs) adsorbed on monocrystalline TiO₂ electrodes have been extensively studied due to their high incident solar light-to-electricity conversion efficiency, colourful and decorative natures and low cost of production. Wide-ranging research has been conducted on structural modifications of the sensitizing dyes in the interest of achieving chromophores with high performance for DSSCs¹.

One approach for structural tuning consists on adjusting the p-bridge with electron rich and/or electron deficient aromatic rings that can perform as an auxiliary electron donor/acceptor group. Electron-rich thiophene and furan heterocycles linked to the electron-deficient phthalazine ring substituted with appropriate acceptor groups are promising candidates among such push-pull systems^{1b, 2, 3}.

As part of an on-going research to develop efficient donor – π-spacer – acceptor heterocyclic systems for several optoelectronic applications² we report the synthesis and characterization of phthalazine derivatives functionalized with cyanoacetic or rhodanine-3-acetic acid as anchoring groups. The experimental results indicate that, these compounds could have potential application as sensitizers for DSSCs.