Poly(aryleneethynylene)s: Syntheses, Properties, Structures, and Applications

Highly Stable, Nondestructive, and Simple Visualization of Latent Blood Fingerprints Based on Covalent Bonding Between the Fluorescent Conjugated Polymer and Proteins in Blood

Latent blood fingerprints (LBFPs) can provide critical information of foul play and help identify the suspects at violent crime scenes. The current methods for LBFP visualization are still not satisfactory because of the low sensitivity or complicated protocol. This study demonstrates a simple and effective LBFP visualization strategy by integrating a new amphiphilic fluorescent amino-functionalized conjugated polymer with the cotton-pad developing protocol. LBFPs on various substrates are visualized by simply covering them with the polymer solution-soaked cotton pads. The images display clear fingerprint patterns, ridge details, and sweat pores, even on very challenging substrates such as painted wood and multicolored can. The gray value analysis confirms semiquantitatively the enhancement of the contrast between ridges and furrows. Even LBFPs with various contaminations or aged for more than 600 days are effectively developed and visualized. The developed fingerprint images show superior stability over long storage time and against solvent washing. Moreover, the polymer causes no degradation of DNAs in the blood, suggesting the possibility of further DNA profiling and identification after development. The mechanistic investigation suggests that the formation of positive or inverted images can be attributed to the synergistic effects from the affinity between polymer and blood, and the affinity betwen polymer and substrate, as well as the slight quenching of polymer fluorescence by blood. Furthermore, the covalent bonding between the protonated primary amino group and proteins in blood endows the stability of the developed fingerprints. The result rationalizes the molecular design of the fluorescent polymer and sheds new light on the future strategies to effective LBFP visualization in practical applications.

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

Two series of 2,5-di(butoxy)phenyleneethynylenes, one halogenated (nPEC4-X; n=2, 3, or 4) and the other boron-dipyrromethene (BODIPY) terminated (nPEC4-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 (¹ H, ¹³ C-DEPTQ-135, COSY, HSQC, HMBC, ¹¹ B, ¹⁹ F) and MALDI-TOF mass spectrometry. The multiplicity and J-coupling constants of ¹ H, ¹¹ B, and ¹⁹ F/¹¹ B NMR signals revealed, in the nPEC4-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 nPEC4-By are comparable to those of the nPEC4-X oligomers and BODIPY, indicating negligible electron communication between BODIPY and the nPEC4 moieties. Nevertheless, energy transfer (ET) from nPEC4 to BODIPY was rationalized by spectroscopy and theoretical calculations. Its yield decreases with the nPEC4 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.

Periodic Fluorescence Variations of CdSe Quantum Dots Coupled to Aryleneethynylenes with Aggregation-Induced Emission

CdSe nanocrystals and aggregates of an aryleneethynylene derivative are assembled into a hybrid thin film with dual fluorescence from both fluorophores. Under continuous excitation, the nanocrystals and the molecules exhibit anticorrelated fluorescence intensity variations, which become periodic at low temperature. We attribute this to a structure-dependent aggregation-induced emission of the aryleneethynylene derivative, which impacts the rate of excitation energy transfer between the molecules and nanocrystals. This work highlights that combining semiconductor nanocrystals with molecular aggregates, which exhibit aggregation-induced emission, can result in emerging optical properties.

Two Is Better than One? Investigating the Effect of Incorporating Re(CO)3Cl Side Chains into Pt(II) Diynes and Polyynes

Pt(II) diynes and polyynes incorporating 5,5'- and 6,6'-disubstituted 2,2'-bipyridines were prepared following conventional Sonogashira and Hagihara dehydrohalogenation reaction protocols. Using Pt(II) dimers and polymers as a rigid-rod backbone, four new heterobimetallic compounds incorporating Re(CO)₃Cl as a pendant functionality in the 2,2'-bipyridine core were obtained. The new heterobimetallic Pt-Re compounds were characterized by analytical and spectroscopic techniques. The solid-state structures of a Re(I)-coordinated diterminal alkynyl ligand and a representative model compound were determined by single-crystal X-ray diffraction. Detailed photophysical characterization of the heterobimetallic Pt(II) diynes and polyynes was carried out. We find that the incorporation of the Re(CO)₃Cl pendant functionality in the 2,2'-bipyridine-containing main-chain Pt(II) diynes and polyynes has a synergistic effect on the optical properties, red shifting the absorption profile and introducing strong long-wavelength absorptions. The Re(I) moiety also introduces strong emission into the monomeric Pt(II) diyne compounds, whereas this is suppressed in the polyynes. The extent of the synergy depends on the topology of the ligands. Computational modeling was performed to compare the energetic stabilities of the positional isomers and to understand the microscopic nature of the major optical transitions. We find that 5,5'-disubstituted 2,2'-bipyridine systems are better candidates in terms of yield, photophysical properties, and stability than their 6,6'-substituted counterparts. Overall, this work provides an additional synthetic route to control the photophysical properties of metallaynes for a variety of optoelectronic applications.

Al-Balushi R, Rather JA, Munam A, Ilmi R, Raithby PR, Zhang Y, Fu Y, Xie Z, Chen S, Islam SM, Wong WY, Skelton JM, Khan MS. Synthesis, characterization, and optoelectronic properties of phenothiazine-based organic co-poly-ynes

We present the synthesis of seven new organic co-poly-ynes P1–P7 incorporating phenothiazine (PTZ) motif and evaluate their optoelectronic properties and performance in polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs).

Advances in deep eutectic solvents and water: applications in metal- and biocatalyzed processes, in the synthesis of APIs, and other biologically active compounds

This review highlights recent advances in metal- and biocatalyzed transformations, in the synthesis of APIs and other biologically active compounds, when employing deep eutectic solvents and water as environmentally responsible solvents.

Electronic conductance and thermopower of single-molecule junctions of oligo(phenyleneethynylene) derivatives

We report the synthesis and the single-molecule transport properties of three new oligo(phenyleneethynylene) (OPE3) derivatives possessing terminal dihydrobenzo[b]thiophene (DHBT) anchoring groups and various core substituents (phenylene, 2,5-dimethoxyphenylene and 9,10-anthracenyl). Their electronic conductance and their Seebeck coefficient have been determined using scanning tunneling microscopy-based break junction (STM-BJ) experiments between gold electrodes. The transport properties of the molecular junctions have been modelled using DFT-based computational methods which reveal a specific binding of the sulfur atom of the DHBT anchor to the electrodes. The experimentally determined Seebeck coefficient varies between -7.9 and -11.4 μV K^-1 in the series and the negative sign is consistent with charge transport through the LUMO levels of the molecules.

Chiroptical Properties in Thin Films of π-Conjugated Systems

Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g_abs and g_lum) and on the application of ECD and CPL to derive structural information on aggregated states.

Aggregation-Induced Emission (AIE): A Historical Perspective

Aggregation-induced emission (AIE) has attracted considerable interest over the last twenty years. In contrast to the large number of available reviews focusing specifically on AIE, this Essay discusses the AIE phenomenon from a broader perspective, with an emphasis on early observations related to AIE made long before the term was coined. Illustrative examples are highlighted from the 20th century where fluorescence enhancement upon rigidification of dyes in viscous or solid environments or J-aggregate formation was studied. It is shown that these examples already include typical AIE luminogens such as tetraphenylethylene (TPE) as well as stilbenes and oligo- or polyphenylenevinylenes and -ethynylenes, which became important fluorescent solid-state materials in OLED research in the 1990s. Further examples include cyanine dyes such as thiazole orange (TO) or its dimers (TOTOs), which have been widely applied as molecular probes in nucleic acid research. The up to 10 000-fold fluorescence enhancement of such dyes upon intercalation into double-stranded DNA, attributable to the restricted intramolecular motion (RIM) concept, afforded commercial products for bioimaging and fluorescence sensing applications already in the early 1990s.

Detection of organic amines using a ratiometric chromophoric fluorescent probe with a significant emission shift

Taking advantages of both the well-known α,β-unsaturated structure and the special nucleophilicity of organic amines toward its acceptor moieties, intramolecular charge transfer as a signaling mechanism is used to design and synthesize a new ratiometric chromophoric fluorescent probe (BI-CA-ID) with large emission shifts toward organic amines. This probe is employed for the detection of organic amines with high selectivity and sensitivity and a “naked-eye” color change (from red to colorless). Ultraviolet–visible and fluorescence spectrometric measurements are used to determine detection limits as low as 0.024 and 0.43 μM. Furthermore, nucleophilic addition of the amine on the α,β-unsaturated of BI-CA-ID indicated that the sensing mechanism occurs via interruption of the π-conjugation.

Twisting and bending photo-excited phenylethynylbenzenes - a theoretical analysis

Oligo(phenylethynyl)benzenes are a family of compounds that exhibit a rich photochemistry changing dramatically with different orientation of a phenyl group in the molecule. Quantum-chemical calculations have been performed to investigate different members of this family of compounds and compared to previous experimental and theoretical studies. 1,4-Bis(phenylethynyl)benzene (BPEB) has different optical properties than its smaller relative diphenylacetylene; however, upon twisting an outer phenyl ring of BPEB, its photochemistry becomes very similar. Fluorine substituents at the central benzene ring are shown to have only small effects on the optical properties of BPEB.

Well-Defined Conjugated Macromolecules Based on Oligo(Arylene Ethynylene)s in Sensing

Macromolecules with well-defined structures in terms of molar mass and monomer sequence became interesting building blocks for modern materials. The precision of the macromolecular structure makes fine-tuning of the properties of resulting materials possible. Conjugated macromolecules exhibit excellent optoelectronic properties that make them exceptional candidates for sensor construction. The importance of chain length and monomer sequence is particularly important in conjugated systems. The oligomer length, monomer sequence, and structural modification often influence the energy bang gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules that reflect in their properties. Moreover, the supramolecular aggregation that is often observed in oligo-conjugated systems is usually strongly affected by even minor structural changes that are used for sensor designs. This review discusses the examples of well-defined conjugated macromolecules based on oligo(arylene ethynylene) skeleton used for sensor applications. Here, exclusively examples of uniform macromolecules are summarized. The sensing mechanisms and importance of uniformity of structure are deliberated.

Two new cadmium(II) coordination polymers based on imidazole-containing ligands: synthesis, structural characterization and fluorescence properties

The judicious selection of suitable ligands is vitally important in the construction of novel metal-organic frameworks (MOFs) with fascinating structures and interesting properties. Recently, imidazole-containing multidentate ligands have received much attention. Two new Cd^II coordination frameworks, namely, poly[tris{μ-1,4-bis[(1H-imidazol-1-yl)methyl]benzene-κ²N³:N^3'}tetrakis(nitrato-κ²O,O')dicadmium], [Cd₂(NO₃)₄(C₁₄H₁₄N₄)₃]_n, (I), and poly[[bis{μ₃-1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene-κ³N³:N^3':N^3''}cadmium] hexafluorosilicate], {[Cd(C₁₈H₁₈N₆)₂](SiF₆)}_n, (II), have been synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. In polymer (I), the 1,4-bis[(1H-imidazol-1-yl)methyl]benzene ligand bridges Cd²⁺ ions with a distorted seven-coordinated pentagonal bipyramidal geometry, forming a one-dimensional ladder chain, and the nitrate anions coordinate to the Cd²⁺ ions in a terminal bidentate fashion. In the crystal, adjacent chains are further connected by C-H...O hydrogen bonds to generate a two-dimensional (2D) supramolecular structure. Polymer (II) exhibits a 2D layered structure in which 1,3,5-tris[(1H-imidazol-1-yl)methyl] benzene ligands join Cd²⁺ centres having a six-coordinated octahedral structure. The layers are connected by hexafluorosilicate anions via C-H...F hydrogen-bond interactions, giving rise to a three-dimensional supramolecular network structure in the solid state. In addition, powder X-ray diffraction (PXRD) patterns were recorded, thermogravimetric analyses (TGA) carried out and fluorescence properties investigated.

Synthesis of Poly(bisisoindigo) Using a Metal-Free Aldol Polymerization for Thin-Film Transistor Applications

Typical syntheses of conjugated polymers rely heavily on organometallic reagents and metal-catalyzed cross-coupling reactions. Here, we show that an environmentally benign aldol polymerization can be used to synthesize poly(bisisoindigo), an analog of polyisoindigo with a ring-fused structural repeat unit. Owing to its extended conjugation length, poly(bisisoindigo) absorbs across the UV/vis/NIR spectrum, with an absorption tail that reaches 1000 nm. Due to the four electron-deficient lactam units on each repeat unit, poly(bisoindigo) possesses a low-lying LUMO, which lies at -3.94 eV relative to vacuum. Incorporation of the ring-fused monomer unit also lowered the overall torsional strain in the polymer backbone (relative to polyisoindigo), and the polymer was successfully used in prototype unipolar n-channel organic thin-film transistors.

A MOF based on a lead(II) 2-oxido-6-methylpyridine-4-carboxylate network

A new metal-organic framework, [Pb(hmpcaH)2] n (1), has been hydrothermally synthesized from Pb(OAc)2 · 3H2O and 2-hydroxy-6-methylpyridine-4-carboxylic acid (hmpcaH2; 2), and characterized by IR spectroscopy, elemental and thermogravimetric analysis, and single-crystal X-ray diffraction. In complex 1, each hmpcaH− ligand represents a three-connected node to combine with the hexacoordinated Pb(II) ions, generating a 3D binodal (3,6)-connected ant network. The crystal structure of 2 was determined. The solid-state fluorescence properties of 1 and 2 were investigated.

Porous Aromatic Frameworks (PAFs)

Porous aromatic frameworks (PAFs) represent an important category of porous solids. PAFs possess rigid frameworks and exceptionally high surface areas, and, uniquely, they are constructed from carbon-carbon-bond-linked aromatic-based building units. Various functionalities can either originate from the intrinsic chemistry of their building units or are achieved by postmodification of the aromatic motifs using established reactions. Specially, the strong carbon-carbon bonding renders PAFs stable under harsh chemical treatments. Therefore, PAFs exhibit specificity in their chemistry and functionalities compared with conventional porous materials such as zeolites and metal organic frameworks. The unique features of PAFs render them being tolerant of severe environments and readily functionalized by harsh chemical treatments. The research field of PAFs has experienced rapid expansion over the past decade, and it is necessary to provide a comprehensive guide to the essential development of the field at this stage. Regarding research into PAFs, the synthesis, functionalization, and applications are the three most important topics. In this thematic review, the three topics are comprehensively explained and aptly exemplified to shed light on developments in the field. Current questions and a perspective outlook will be summarized.

A visible-light-induced “on–off” one-pot synthesis of 3-arylacetylene coumarins with AIE properties

A mild one-pot approach to 3-arylacetylene coumarins with potential AIE activities was developed via photosensitizer-free photocatalysis and thermocatalysis.

Two-dimensional halogen-bonded organic frameworks based on the tetrabromobenzene-1,4-dicarboxylic acid building molecule

2D halogen-bonded organic frameworks were readily engineered by strong and directional effects of the primary Br⋯O and the secondary Br⋯π halogen bonding interactions from the tetrabromobenzene-1,4-dicarboxylic acid building molecule involving 100% supramolecular yields.

Modular synthesis and transition metal-free alkynylation/alkenylation of Castagnoli–Cushman-derived N,O- and N,S-heterocyclic vinyl chlorides

A modular and functional group-tolerant protocol for the transition metal-free coupling of novel N,O- and N,S-heterocyclic vinyl chlorides with terminal acetylenes and styrenes has been developed, leading to the epimerization-free synthesis of fully carbofunctionalized dihydro-1,4-oxazines/thiazines. Bicyclic morpholines have also been prepared through the interrogation of newly synthesized cross-conjugated dienes in Diels–Alder reactions. The use of environmentally benign reaction media endows the current strategy with a practical advantage.

A functional group-tolerant and transition metal-free coupling of novel N,O- and N,S-heterocyclic vinyl chlorides, which affords fully carbosubstituted dihydro-1,4-oxazines/thiazines as well as bicyclic morpholines, is described.

A simple D–π–A system of phenanthroimidazole-π-fluorenone for highly efficient non-doped bipolar AIE luminogens: synthesis, and molecular optical, thermal and electrochemical properties

We report the synthesis of phenanthroimidazole based dyes incorporating fluorenone using Suzuki coupling and their aggregation induced emission characterisation.

Recent Innovation of Metal-Organic Frameworks for Carbon Dioxide Photocatalytic Reduction

The accumulation of carbon dioxide (CO2) pollutants in the atmosphere begets global warming, forcing us to face tangible catastrophes worldwide. Environmental affability, affordability, and efficient CO2 metamorphotic capacity are critical factors for photocatalysts; metal-organic frameworks (MOFs) are one of the best candidates. MOFs, as hybrid organic ligand and inorganic nodal metal with tailorable morphological texture and adaptable electronic structure, are contemporary artificial photocatalysts. The semiconducting nature and porous topology of MOFs, respectively, assists with photogenerated multi-exciton injection and adsorption of substrate proximate to void cavities, thereby converting CO2. The vitality of the employment of MOFs in CO2 photolytic reaction has emerged from the fact that they are not only an inherently eco-friendly weapon for pollutant extermination, but also a potential tool for alleviating foreseeable fuel crises. The excellent synergistic interaction between the central metal and organic linker allows decisive implementation for the design, integration, and application of the catalytic bundle. In this review, we presented recent MOF headway focusing on reports of the last three years, exhaustively categorized based on central metal-type, and novel discussion, from material preparation to photocatalytic, simulated performance recordings of respective as-synthesized materials. The selective CO2 reduction capacities into syngas or formate of standalone or composite MOFs with definite photocatalytic reaction conditions was considered and compared.

A Solid-State Fluorescence Sensor for Nitroaromatics and Nitroanilines Based on a Conjugated Calix[4]arene Polymer

A new conjugated polymer possessing calix[4]arene-oxacyclophane units wired-in-series by phenyleneethynylene linkers was synthesized by a Sonogashira-Hagihara cross-coupling method in high yield. The polymer was structurally characterized by FTIR and ¹H/¹³C/HSQC NMR techniques, and its average M_n (38.5 kDa) retrieved from GPC analysis. The polymer is highly emissive (Φ_F = 0.55) and exhibits a longer-than-usual excited-state lifetime (1.80 ns) for a phenyleneethynylene type polymer. Similar photophysical properties (absorption and fluorescence emission) were observed in solution and in solid-state. This stems from the presence of bulky calixarene moieties along the polymer chains which prevent interchain staking and the formation of ground-state aggregates and/or non-emissive exciplexes, both deleterious to solid-state materials envisioned for fluorescence sensing applications. Moreover, the intrinsic molecular recognition capabilities of its two rigid inner cavities (calixarene and cyclophane sub-units), allied with the high three-dimensionality of the macromolecule that creates additional interstitial voids around the molecular receptors, can boost its sensory responses towards specific analytes. A high sensitive response was observed in the detection of nitroaromatics and nitroanilines in neat vapour phases by casted films of the polymer. The largest sensitivities were obtained for 2,4-dinitrotoluene (a taggant for the explosive TNT; > 85% of fluorescence quenching upon 1 min exposure) and ortho-nitroaniline (90% of emission reduction in 30 s). The sensory responses attained in solid-state are discussed on the basis of the electron affinities of the analytes and their electrostatic interactions with polymer films. Graphical Abstract Sensing the threats! A high sensitive response was observed in the detection of explosives and noxious nitroanilines in neat vapour phases by thinfilms of a calixarene-based polymer.

Facilitating Gold Redox Catalysis with Electrochemistry: An Efficient Chemical-Oxidant-Free Approach

Due to the high oxidation potential between AuI and AuIII , gold redox catalysis requires at least stoichiometric amounts of a strong oxidant. We herein report the first example of an electrochemical approach in promoting gold-catalyzed oxidative coupling of terminal alkynes. Oxidation of AuI to AuIII was successfully achieved through anode oxidation, which enabled facile access to either symmetrical or unsymmetrical conjugated diynes through homo-coupling or cross-coupling. This report extends the reaction scope of this transformation to substrates that are not compatible with strong chemical oxidants and potentiates the versatility of gold redox chemistry through the utilization of electrochemical oxidative conditions.

Exploring antiaromaticity in single-molecule junctions formed from biphenylene derivatives

We report the synthesis of a series of oligophenylene-ethynylene (OPE) derivatives with biphenylene core units, designed to assess the effects of biphenylene antiaromaticity on charge transport in molecular junctions. Analogues with naphthalene, anthracene, fluorene and biphenyl cores are studied for comparison. The molecules are terminated with pyridyl or methylthio units. Single-molecule conductance data were obtained using the mechanically controllable break junction (MCBJ) technique. It is found that when electrons pass from one electrode to the other via a phenylene ring, the electrical conductance is almost independent of the nature of the pendant π-systems attached to the phenylene ring and is rather insensitive to antiaromaticity. When electrons pass through the cyclobutadiene core of the biphenylene unit, transport is sensitive to the presence of the relatively weak single bonds connecting the two phenylene rings of biphenylene, which arise from partial antiaromaticity within the cyclobutadiene core. This leads to a negligible difference in the molecular conductance compared to the fluorene or biphenyl analogues which have standard single bonds. This ability to tune the conductance of molecular cores has no analogue in junctions formed from artificial quantum dots and reflects the quantum nature of electron transport in molecular junctions, even at room temperature.

Rod-like transition first or chain aggregation first? ordered aggregation of rod-like poly(p-phenyleneethynylene) chains in solution

The rod-like configuration of conjugated polymer chains with its low energetic disorder is the key to utilizing the backbone as a highly electrically-conductive wire. An energetic disorder that is higher than 0.1 eV, coupled with vibronic modes of the chains, leads to the localization of charges. Herein, we have tracked precisely the rod-like transition of poly(p-phenyleneethynylene) (PPE) chains as a function of temperature in diluted solutions, and shown a steep increase in persistence length at 230 K. The resulting rod-like configuration of the PPE chains with its extended electronic conjugation exhibited an extremely small energetic disorder of ∼70 meV, and was stabilized by subsequent polymer aggregate formation.

A macrocyclic oligofuran: synthesis, solid state structure and electronic properties

The first π-conjugated macrocyclic system with an oligofuran backbone display planar conformation and forms large π-aggregates, in contrast to the twisted conformation of small macrocyclic oligothiophenes.

We report the first π-conjugated macrocyclic system with an oligofuran backbone. The calculated HOMO–LUMO gap is similar to that of the corresponding linear polymer, indicating a remarkable electron delocalization. The X-ray structure reveals a planar conformation, in contrast to the twisted conformation of macrocyclic oligothiophenes. The intermolecular π–π stacking distance is extremely small (3.17 Å), indicating very strong interactions. The macrocycle forms large π-aggregates in solution and shows a tendency toward highly ordered multilayer adsorption at the solid–liquid interface. The face-on orientation of molecules explains the higher hole mobility observed in the out-of-plane direction.

Sonogashira coupling reactions: Synthesis of 4-substituted-6-methyl-2-(methylthio)pyrimidines catalyzed by Pd–Cu

An efficient method is developed for the synthesis of 4-(3-arylprop-2-ynyloxy)-6-methyl-2-(methylthio)pyrimidines via palladium-catalyzed Sonogashira reactions of 4-methyl-2-(methylthio)-6-(prop-2-yn-1-yloxy)pyrimidine with electron-poor aryl iodides in acetonitrile at room temperature. Excellent yields of the products were obtained in reaction times of 9–11 h.

Macromolecular Probe Based on a NiII/TbIII Coordination Polymer for Sensitive Recognition of Human Serum Albumin (HSA) and MnO4. ACS OMEGA 2019;4:11949-11959. [PMID: 31460306 PMCID: PMC6682116 DOI: 10.1021/acsomega.8b03326]

Reported here are the design and fluorescence characters of a Ni^II/Tb^III polymer, [Tb₂Ni₃(HCAM)₆(H₂O)₁₂] _n (1) (H₃CAM = chelidamic acid). Under physiological conditions, the binding of biocompatible water soluble 1 to human serum albumin (HSA) was studied by spectroscopy techniques, which revealed that 1 could inherent the fluorescent light of HSA in a static quencher course and change the HSA second-level structure. The marked enhancement in 1 and its fluorescence intensity provide conclusive evidence that 1 can play the role of a "turn-on" sensor for recognition and detection of HSA in other biological interferents with a K _sv value of 7.68 × 10⁴ M^-1 and a detection limit of 0.14 μM. Luminescence experiments show that 1 has high selectivity and sensitivity to MnO₄ ^- in other anions. Its quenching efficiency (K _sv) is 5.54 × 10³ M^-1, and the detection limit is 0.29 μM.

Simply Structured Conjugated Compounds with Cyanoacrylate or Acrylonitrile Groups for Sensing of p-Toluenethiol

Simply structured conjugated compounds with cyanoacrylate (CA 1 - 4) and acrylonitrile (AN 1 - 4) terminal groups were synthesized by a Knoevenagel condensation reaction in one step and investigated for their recognition properties to p-toluenethiol by UV-vis, fluorescence spectra, and FT-IR measurements. When p-toluenethiol was added to CA 1, the FT-IR spectra revealed a cleavage of alkene caused by the addition reaction between p-toluenethiol and CA 1. An increase in p-toluenethiol concentration, a blue-shifted absorption band, and a decrease in the fluorescence intensity of CA 1 were observed because of the decrease in its effective conjugated length. Therefore, the most simply structured CA 1 was found to be the most effective and the most sensitive chemical sensor for p-toluenethiol.

Experimental and theoretical insights on the effect of solvent polarity on the photophysical properties of a benzanthrone dye

Benzanthrone derivatives show interesting solvent dependent photophysical properties. Understanding of their photophysical properties is essential for developing the fluorescence probes based on benzanthrone derivatives. The photophysical properties of 3-(N'-chlorophenyl)piperazino-7H-benzo[de]anthracen-7-one [ClPh-PBA] molecule are reported in different solvents and solvent mixtures. The change in Stokes shift, quantum yield, fluorescence life time and radiative rate constants as a function of solvent polarity shows that the Intermolecular Charge Transfer (ICT) is affected by solvent polarity and hydrogen bonding. The quantum yield and fluorescence life time values decrease and the nonradiative decay rate constant (k_nr) values are observed to be higher in polar solvents. The weak emission of ClPh-PBA in polar solvents is primarily due to the non-radiative torsional motion of the chlorophenyl group around benzanthrone moiety. The torsional motion of chlorophenyl group at the remote nitrogen around benzanthrone moiety is also evident from TDDFT calculations performed using B3LYP/6-311+ G (d, p) basis set. The ground state and excited state dipole moments, absorption and emission maxima (nm) along with other quantum chemical parameters are obtained using B3LYP/6-311+ G (d, p) basis set. The experimental and theoretical results follow the similar trends.