Dual Emission of meso-Phenyleneethynylene–BODIPY Oligomers: Synthesis,Photophysics, and Theoretical Optoelectronic Study

Two series of 2,5-di(butoxy)phenyleneethynylenes, one halogenated ( n PEC4-X ; n=2, 3, or 4) and the other boron-dipyrromethene (BODIPY) terminated ( n PEC4-By ; n=3, 4, or 5; By=BODIPY), were synthesized monodirectionally by the step-by-step approach and the molecular structure was corroborated by NMR spectroscopy (¹H, ¹³C-DEPTQ-135, COSY, HSQC, HMBC, ¹¹B, ¹⁹F) and MALDI-TOF mass spectrometry. The multiplicity and J-coupling constants of ¹H, ¹¹B, and ¹⁹F/¹¹B NMR signals revealed, in the n PEC4-By series, that the phenyl in the meso position of BODIPY becomes electronically part of the conjugation of the phenyleneethynylene chain, whereas BODIPY is electronically isolated. The photophysical, electrochemical, and theoretical studies confirm this finding because the properties of n PEC4-By are comparable to those of the n PEC4-X oligomers and BODIPY, indicating negligible electron communication between BODIPY and the n PEC4 moieties. Nevertheless, energy transfer (ET) from n PEC4 to BODIPY was rationalized by spectroscopy and theoretical calculations. Its yield decreases with the n PEC4 conjugation length, according to the increase in distance between the two chromophores, resulting in dual emission for the longest oligomer in which ET is quenched.     

Modulation of animal and human hematopoiesis by β-glucans: a review

β-glucans are cell wall constituents of bacteria, yeast, fungi, and plants. They are not expressed in mammalian cells, but they are recognized by mammalian cells as pathogen-associated molecular patterns by pattern recognition receptors and thus act as biological response modifiers. This review summarizes data on the hematopoiesis-stimulating effects of β-glucans, as well as on their ability to enhance bone marrow recovery after an injury. β-glucans have been shown to support murine hematopoiesis suppressed by ionizing radiation or cytotoxic anti-cancer therapy. They also enhance stem cell homing and engraftment. Basically, two forms of β-glucan preparations have been investigated, namely particulate and soluble ones. β-glucans are generally well tolerated, the particulate forms showing a higher incidence of undesirable side effects. Taken together, the hematopoiesis-stimulating properties of β-glucans predetermine these biological response modifiers to ever increasing use in human medicinal practice.     

Color Tunable Emission and Oxygen Sensing from a Discrete Europium−Pyrene Assembly

We report the synthesis of a new pyrene, dipicolinic acid-based ligand ( L₁H ) and its corresponding multi-emissive and multifunctional europium complex [Eu( L₁ )₃] that is capable of single component color switchable emission from red to blue and also white. At high concentration (10 mM) the single component system results in near pure white emission (CIE coordinates x,y=0.329, 0.324). Furthermore, the system showed ratiometric oxygen sensing with oxygen significantly quenching the pyrene centered emission but not the Eu³⁺ emission, resulting in an overall emission color change from blue to red on increasing oxygen content.     

α-Cyano Triaryl[3]radialene: Unsymmetrical Stereo-configuration,Clustering-enhanced Excimer Emission,and Radical-involved Multimodal Information Switching

[3]Radialene has a peculiar topology and cross-conjugation system, representing a unique molecular scaffold in organic materials. Herein, we report a special class of stereoisomeric α-cyano triaryl[3]radialenes ( CTRs ) that show concentration-caused quenching in solution but emit red-shifted and enhanced luminescence in the crystalline state. Clustering of multiple cyano groups and their through-space interactions with the [3]radialene ring significantly extend π-electron communication meanwhile rigidifying the propeller conformation multivalently, thus playing a key role behind the state-dependent luminescence. These radialenes with a substantial electron affinity undergo a reversible electron transfer transition to anionic radicals with good stability, showing switching of photoabsorption, photoluminescence and electron spin resonance (ESR) signal. We also established proof-of-concept applications of CTRs for multimodal information encryption and chemical sensing.     

N-Confused Phlorin-Prodigiosin Chimera: meso-Aryl Oxidation and π-Extension Triggered by Peripheral Coordination

An N-confused phlorin isomer bearing a dipyrrin moiety at the α-position of the confused pyrrole ring ( 1 ) was synthesized. Pd^II and B^III coordination at the peripheral prodigiosin-like moiety of 1 afforded the corresponding complexes 2 and 3 . Reflux of 2 in triethylamine (TEA) converted the meso-phenyl into the Pd^II-coordinating phenoxy group to afford 4 . Under the same reaction conditions, TEA was linked to the α-position of the dipyrrin unit in 3 as an N,N-diethylaminovinyl group to afford 5 . Furthermore, peripheral coordination of B^III in 3 and 5 improved the planarity of the phlorin macrocycle and thus facilitated the coordination of Ag^III at the inner cavity to afford 3-Ag and 5-Ag , respectively. These results provide an effective approach for developing unique porphyrinoids through peripheral coordination.     

As Nice as π: Aromatic Reactions Activated by π-Coordination to Transition Metals

π-Coordination of aromatic molecules to metals dramatically alters their reactivity. For example, coordinated carbons become more electrophilic and C−H bonds of coordinated rings become more acidic. For many years, this change in reactivity has been used to trigger reactions that would not take place for uncoordinated arenes, however, there has been a recent resurgence in use of this technique, in part due to the development of catalytic reactions in which π-coordination is transient. In this Minireview, we describe the key reaction chemistry of arenes coordinated to a range of transition metals, including stereoselective reactions and industrially relevant syntheses. We also summarise outstanding examples of catalytic processes. Finally, we give perspectives on the future direction of the field, with respect to both reactions that are stoichiometric in activating metals and those employing catalytic metal.     

Dipyrrolyldiketone PtII Complexes: Ion-Pairing π-Electronic Systems with Various Anion-Binding Modes

A variety of π-electronic ion-pairing assemblies can be constructed by combining anion complexes of π-electronic systems and countercations. In this study, a series of anion-responsive π-electronic molecules, dipyrrolyldiketone Pt^II complexes containing a phenylpyridine ligand, were synthesized. The resulting Pt^II complexes exhibited phosphorescence emission, with higher emission quantum yields (0.30–0.42) and microsecond-order lifetimes, and solution-state anion binding, as revealed by our spectroscopic analyses. These Pt^II complexes displayed solid-state ion-pairing assemblies, exhibiting various anion-binding modes, which derived from pyrrole-inverted and pyrrole-non-inverted conformations, and packing structures, with the contribution of charge-by-charge assemblies, which were dependent on the substituents in the Pt^II complexes and the geometries and electronic states of their countercations.     

Controlling Energy Gaps of π-Conjugated Polymers by Multi-Fluorinated Boron-Fused Azobenzene Acceptors for Highly Efficient Near-Infrared Emission

We demonstrate that multi-fluorinated boron-fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor-acceptor (D-A) type π-conjugated polymers. Position-dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near-infrared (NIR) emission (λ_PL=758–847 nm) with high absolute photoluminescence quantum yield (Φ_PL=7–23%) originating from low-lying LUMO energy levels of the BAz moieties (−3.94 to −4.25 eV). Owing to inherent solid-state emissive properties of the BAz units, deeper NIR emission (λ_PL=852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D-A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron-accepting unit through fine-tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials.     

Synthesis of planar chiral iridacycles by cationic metal π-coordination: facial selectivity, and conformational and stereochemical consequences

Facial selectivity during the π-coordination of pseudo-tetrahedral iridacycles by neutral (Cr(CO)(3)), monocationic (Cp*Ru(+)), and biscationic (Cp*Ir(2+)) metal centers was directly influenced by the coulombic imbalance in the coordination sphere of the chelated Ir center. We also showed by using theoretical calculations that the feasibility of the related metallacycles that displayed metallocenic planar chirality was dependent to the presence of an electron-donating group, such as NMe(2), which contributed to the overall stability of the complexes. When the π-bonded moiety was the strongly electron-withdrawing Cp*Ir(2+) group, the electron donation from NMe(2) resulted in major conformational changes, with a barrier to rotation of about 17?kcal mol(-1) for this group that became spectroscopically diastereotopic (high-field (1)H?NMR spectroscopy). This peculiar property is proposed as a means to introduce a new type of constitutional chirality at the nitrogen center: planar chirality at tertiary aromatic amines.     

Oxidized isoquinolinoisoindolinone and benzazepinoisoindolinone alkaloids cores by convergent cyclisation processes: π-aromatic attack of thionium and oxonium species

An efficient methodology for synthesis of isoindoloisoquinoline 5a and isoindolobenzazepine 5b in oxidized forms as tetracyclic alkaloids cores are reported from N-bromoethylphthalimide (6) or phthalic anhydride and 2-phenylthioethylamine (8) in a five- or six-step sequence, respectively, in overall very good yields. The key step of this methodology is based on an intramolecular π-cationic cyclization of the thionium ion species. Alternatively, another four-step route was explored and based in an ultimate step on the cyclodehydration of an aldehyde functionality, which used as intermediate in the latest strategy, via the oxonium ion cation.     

Chiral induction by helical neighbour: spectroscopic visualization of macroscopic-interaction among self-sorted donor and acceptor π-stacks

Supramolecular induction of chirality to a π-stacked dialkoxynaphthalene (DAN)-fiber (made of achiral building blocks) from a neighbouring helical naphthalenediimide (NDI)-fiber is reported. CD-studies helped in understanding the nature of co-assembly in the donor-acceptor chromophore mixture from molecular to macroscopic scale.     

Microwave‐Assisted Dehalogenation of α‐Haloketones by Zinc and Ammonium Chloride in Alcohol

The treatment of α‐haloketones with 1.5 equiv. of Zn and 1 equiv. of NH₄Cl in ethanol for 0.5 min gave the corresponding ketones with excellent yields under microwave irradiation. Vic‐dibromides and 2,2‐dibromoacetophenone can be efficiently debrominated to alkenes and acetophenones, respectively.     

The improvement of π-conjugation by the lateral benzene of anthracene and naphthalene

The 1,4-diarylnaphthalenes, 1,4-diarylanthracenes, and 9,10-diarylanthracenes containing the different side arenes, including phenyl, 2-thienyl, and 2-furyl groups, were synthesized to study the influence of structures on π-conjugation. According to photophysics and computation, the smaller dihedral angles and the lateral benzene of anthracene would increase the π-conjugation in some cases. Compared to 1,4-diarylnaphthalenes, 1,4-di(thien-2-yl)anthracene, 1,4-di(fur-2-yl)anthracene, and 9,10-di(fur-2-yl)anthracene displayed better π-conjugation in both of the ground and fluorescing excited states, but 9,10-di(thien-2-yl)anthracene only showed better π-conjugation in the fluorescing excited state.     

Excimer emission of caffeine with α- and β-cyclodextrins: spectral and molecular modelling studies

Excimer emission of caffeine with α-CD and β-CD were studied by UV-visible, fluorescence, time-resolved fluorescence, FTIR, ¹H NMR and molecular modelling techniques. Changes in the absorbance and fluorescence and lifetime of the caffeine with cyclodextrin (CD) solutions indicate (i) caffeine shows dual emission in the CD solutions, (ii) normal emission originates from a monomer and the longer wavelength emission is due to excimer and (iii) in both CDs caffeine forms 1:2 inclusion complex. Carbonyl stretching frequency moved to higher wave numbers and broadening of the N–H stretching band indicated the formation of inclusion complex. The resonance of the methyl protons of caffeine show remarkable upfield or downfield shift in the ¹H NMR, which indicates imidazole ring of the caffeine entrapped in the CD cavities. Investigations of energetic, thermodynamic and electronic properties of PM3 computational calculations confirmed the stability of the inclusion complex.     

Possibilities of the Determination of Matrix Elements of High-Purity Glasses of As–Se and As–S Systems by Inductively Coupled Plasma Atomic Emission Spectrometry

Possibilities of inductively coupled plasma atomic emission spectrometry (ICP AES) as an alternative to X-ray spectrochemical analysis are estimated in the determination of matrix elements of glasses of As–Se and As–S systems. Standard solutions were prepared from pure elements As, Se and S. It was shown that the matrix elements of glasses can be determined with an expanded uncertainty of 0.05–0.1 mol %. The results of determinations by ICP AES and X-ray fluorescence spectrometry were compared; and it was found that by the attained performance characteristics, the results of ICP AES are highly competitive with the data of X-ray fluorescence spectrometry, but do not require sets of adequate solid reference samples.     

Construction of Helically Stacked π-Electron Systems in Poly(quinolylene-2,3-methylene) Stabilized by Intramolecular Hydrogen Bonds

π-Stacked polymers, which consist of layered π-electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π-stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π-stacked architecture based on poly(quinolylene-2,3-methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo-copolymerization of an o-allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted-tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic-force microscopy.     

Complexation of monosubstituted benzenes and methanes by cyclotetrachromotropylene in aqueous solution: Substituent effects on π-π and Ch-π interactions

The stability constantsK of 11 complexes formed in aqueous solution between several monosubstituted benzenes (C₆H₅X) and methanes (CH₃X) as guests and cyclotetrachromotropylene as host were determined by proton NMR spectroscopy. Variations ofK with the substituent X are attributed to the electronic effect of X and the presence of C–H or aromatic bonds, if any, interacting with the host bonds.     

Enhanced π-conjugation and emission via icosahedral carboranes: synthetic and spectroscopic investigation

The ability of ortho-, meta- and para-carboranes to enhance the emission intensity has been compared. For this purpose a series of carborane-appended 1,3,5-triphenylbenzene (TB) and 1,3,5- tris(biphenyl-4-yl)benzene (TBB) containing three ortho-, meta- and para-carborane clusters directly attached to the conjugated cores have been synthesized employing Suzuki, Heck, and trimerization reactions. The incorporation of the icosahedral carboranes was associated with a red shift in the UV absorption spectrum of up to 13 nm as well as enhancements of the emission intensities of up to 154%. The presence of ortho-carboranes showed the maximum red shift in the UV spectrum whereas the maximum enhancement of the emission intensity was observed in the presence of meta-carborane clusters. The order of π-conjugation extension is found to be ortho > meta ≈ para. A comparative thermal analysis indicated o-carborane-appended trimers to be the most thermally stable in the series. Proton NMR spectra of reported carborane-appended trimers indicated that ortho- and meta-carborane cages have benzenelike characteristics.