Synthesis of three-dimensionally arranged porphyrin arrays via intramolecular meso-meso coupling

The synthesis and photophysical properties of three-dimensionally arranged porphyrin arrays with through-space electronic communication are reported. 1,3,5-Trioxamethylphenylene bridged Zn(II) porphyrin trimer 3 was coupled by Ag(I)-promoted oxidative coupling reaction to give porphyrin cage 5 comprising three meso-meso linked diporphyrins, which was then transformed by oxidation with DDQ and Sc(OTf)₃ into porphyrin cage 7 comprising three fused diporphyrins. Intramolecular meso-meso coupling reaction was applied to porphyrin pentamer 11 to provide porphyrin array 12 consisting of a porphyrin core flanked by two meso-meso linked diporphyrins. Further oxidation of 12 with DDQ and Sc(OTf)₃ afforded triply stacked porphyrin array 13 that is comprised of a porphyrin core flanked by two porphyrin tapes. UV-vis-NIR absorption and fluorescence spectra of 5, 7, 12, and 13 showed their distorted conformations and electronic interaction within the stacked porphyrin arrays.     

An improved synthesis of a fluorescent gabapentin-choline conjugate for single molecule detection

Voltage-gated calcium ion channels comprise pore-forming α₁ and auxiliary α₂δ, β, and γ subunits. They are important molecular devices involved in a variety of cell functions. Fluorescently labeled acylcholine analogues are important in studies such as ion channel regulation. Cy3-3-acetylcholine has recently been synthesized for single molecule detection studies; albeit in an extremely low overall yield (0.06%). In this work, an alternative route to that used in the previous Cy3-3-acetylcholine synthesis was developed with a 90% yield at a significantly lower material cost.     

A “turn-on” fluorescent chemosensor for zinc ion with facile synthesis and application in live cell imaging

Compound 1 was facilely synthesized through a one step reaction from commercially available materials. As a sensitive and selective “turn-on” fluorescent chemosensor for Zn(II), 1 exhibits a 40-fold fluorescence enhancement response to Zn(II) over other physiological relevant metal ions in aqueous solution at neutral pH. Furthermore, 1 could be efficiently delivered to live cells for bioimaging of Zn(II).     

Rational design of the benzothiazole-based fluorescent scaffold for tunable emission

The 2-(2-hydroxyphenyl)-benzothiazole (HBT) fluorophore has attracted considerable attention due to its excited-state intramolecular proton transfer (ESIPT) based emission and its large Stokes shift. However, this fluorophore possesses several disadvantages including low quantum yield and short emission in the blue range. In this study, by coupling HBT at the ortho-, meta-, and para-positions to the hydroxyl group with different heterocycles to extend the conjugation system, we have successfully obtained new fluorophores with tunable emissions both in solution and in the solid-state (409–652?nm). Notably, all of the derivatives demonstrated improved quantum yields compared with the parent HBT structure. Moreover, selected compounds have been shown to shine brightly in live cells, indicating promising potential for bioimaging.     

Multistep synthesis of a new tricyclic azaindole-based scaffold

In this Letter the synthetic pathway adopted for the preparation of a new functionalized tricyclic scaffold containing the 7-azaindole moiety is presented. An intramolecular palladium-mediated reaction is described as the crucial step for a condensed seven-membered ring formation.     

Recent Development of SnII,SbIII-based Birefringent Material: Crystal Chemistry and Investigation of Birefringence

The combination of Sn^II or Sb^III with π, non-π-conjugated units has produced birefringent crystals with birefringence ranging from 0.005 to 0.468@1064 nm. It is proven that introducing Sn^II or Sb^III into crystals is a feasible strategy to enlarge the birefringence, which not only promotes the miniaturization of fabricated devices, but also effectively modulates polarized light. Herein, recently discovered Sn^II, Sb^III-based birefringent crystals with birefringence investigated are summarized, including their crystal structure and optical properties, especially birefringence. This review also presents the influence of Sn^II, Sb^III with stereochemically active lone pair on the optical anisotropy. We hope that this work provides a clear perspective on the crystal chemistry of Sn^II, Sb^III-based optical functional crystals and promotes the development of new birefringent crystals with large optical anisotropy.     

Recent progress in small molecule fluorescent probes for nitroreductase

This review aims to provide a summary of the progress in fluorescent probes for nitroreductase (NTR) in recent years and displays the main fluorescent mechanisms that have been applied to design probes.     

A facile synthesis of α-amino-DOTA as a versatile molecular imaging probe

An amino group has been introduced into one ligand of DOTA that can couple to peptidyl carboxylates by coupling α-brominated glycine to DO3A-^tBu (1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid, tert-butylester)). α-Amino-DOTA was coupled to the carboxylate backbone terminus of a peptide to demonstrate the utility for derivatization.     

Aminoalkylferrocenyldichlorophosphanes: facile synthesis of versatile chiral starting materials

A series of racemic and optically pure aminoalkylferrocenyldichlorophosphanes has been prepared by reaction of phosphorus trichloride with the corresponding lithiated aminoalkylferrocene precursors. Crystal structures of racemic 1-dichlorophosphanyl-2-N,N-dimethylaminomethylferrocene, racemic 1-dichlorophosphanyl-2-N,N-dimethylaminomethyl-3-triphenylsilylferrocene and (S)-N,N-dimethyl-1-[(R)-2-(dichlorophosphanyl)ferrocenyl]ethylamine reveal short intramolecular N[dot dot dot]P distances, which are suggestive of weak N --> P dative bonds. The aminoalkylferrocenyldichlorophosphanes can be used for the preparation of the corresponding primary phosphanes, one of which was characterised by X-ray crystallography. Optically pure (R)-N,N-dimethyl-1-[(S)-2-(phosphanyl)ferrocenyl]ethylamine can easily be lithiated twice to give the first enantiomerically pure lithium-phosphorus closo cluster compound, which was also structurally characterised.     

All-Z-hexabenzo[24]annulene with a triangular benzene cluster substructure

All-Z-hexabenzo[24]annulene was synthesized via a poly-cis-stilbene intermediate. The single crystal of the annulene has a chiral C₃-symmetry with a central benzene trimer substructure. Although the compound is highly flexible in solution, the C₃-symmetric structure is stabilized by three concurrent CH/π interactions.     

New pyrrolo[3,2-b]pyrrole derivatives with multiple-acceptor substitution: Efficient fluorescent emission and near-infrared two-photon absorption

Two new D-π-A organic chromophores, 1,2,4,5-tetra(4-cyanophenyl)pyrrolo[3,2-b]pyrrole (4CNPP) and 1,2,3,4,5,6-hexa(4-cyanophenyl)pyrrolo[3,2-b]pyrrole (6CNPP), were developed by modifying the electron-rich pyrrolo[3,2-b]pyrrole (PP) unit with four and six 4-cyanophenyls respectively. The compounds exhibited bright blue emissions in low- to high-polarity solvents, with high Ф_fs of 88–90% in toluene, as well as impressive two-photon absorption cross-sections at the near-infrared (NIR) 700?nm.     

A novel small molecule fluorescent sensor for Zn2+ based on pyridine-pyridone scaffold

The development of a water-soluble and small molecular weight fluorescent probe, 3-(4-methoxyphenyl)-4-(methylsulfanyl)-6-(pyridin-2-yl)pyridin-2(1H)-one (3), for detecting Zn²⁺ based on pyridine-pyridone skeleton is reported. We observed a clear chelation enhanced fluorescence effect of 3 in the presence of Zn²⁺. Other fluorescent properties of 3 are discussed.     

Formation of metal-lustrous organic crystals from 2-aryl-1-(4-methoxyphenyl)-5-(5-tricyanoethenyl-2-thienyl)pyrroles

Various 2-aryl-1-(4-methoxyphenyl)-5-(5-tricyanoethenyl-2-thienyl)pyrroles (3) were synthesized. When the 2-aryl group of 3 is phenyl, 4-tolyl, and 4-methoxyphenyl, organic crystals with greenish yellow metallic luster are formed. In contrast, a 2-(4-fluorophenyl) derivative of 3 gives gold-like lustrous crystals. The relation of their crystal structures with the appearance of metallic color is mentioned.     

A convergent synthesis of the imidazopyridine scaffold of fluorescent alkaloid ageladine A

A convergent synthesis of the imidazopyridine scaffold of fluorescent alkaloid ageladine A (1) has been achieved, employing 3-amino-2-chloropyridine as the staring material. A carboxylic acid was introduced using n-butyllithium and dry ice as the key reaction.     

A versatile scaffold for site-specific modification of cyclic tetrapeptides

A novel scaffold that can be used to prepare conformationally homogeneous cyclic tetrapeptides equipped with a β-amino acid residue is disclosed. It is shown that regioselective structural modification can be accomplished using thiols and azide nucleophiles, commonly associated with rich downstream chemistry. The method should find application in efforts to constrain privileged tripeptide sequences in rigid molecular scaffolds.     

Design and synthesis of fluorescent galactolipid probes

Fluorescent galactolipid analogues (1, 1a, and 2) have been synthesized with a pyrene group attached to the amino-terminal of a hexanoyl chain bound to an otherwise normal galactolipid structure. The synthetic lipids are obtained from peracetyl galactose by a general and versatile procedure based on the trichloroacetimidate methodology. The intense violet fluorescence (376 and 395 nm) and good photostability of pyrene make these compounds highly suitable as probes to study galactolipid metabolism. As proof of concept, we report that compound 2 is a valid tool to detect galactolipase activity in enzymatic preparations of potato tubers.     

A facile route to a versatile synthon for preparation of cis-pyrethroids

$\text{cis}$-2-Cyano-3,3-dimethylcyclopropanecarboxylic acid was obtained in >50% overall yield starting with ethyl 3,3-dimethylacrylate. The key step involved a tandem Michael reaction - intramolecular displacement to afford stereoselectively a cyclopropanoid precursor of $\text{cis}$-pyrethroids.     

Recent progress in two-photon small molecule fluorescent probes for enzymes

This review aims to provide a summary of the progress in TP small molecule fluorescent probes for enzymes in recent years and displays the main fluorescent mechanisms that have been applied to design probes.     

Perylene bisimide as a versatile fluorescent tool for environmental and biological analysis: a review

Perylene bisimide (PBI) is a fluorescent dye which has strong emission and high photostability. Although PBI has been widely used for industrial materials, the application of PBI in analytical fields was limited mainly due to its high hydrophobicity. In recent years, however, unique and useful analytical methods based on PBI platform are being successfully developed by utilizing the characteristic features of this compound including its high hydrophobicity. In this article, the recent trend of environmental and biological analysis using PBI is reviewed.     

Mg(C3O4H2)(H2O)2: A New Ultraviolet Nonlinear Optical Material Derived from KBe2BO3F2 with High Performance and Excellent Water-Resistance

Acquiring high-performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase-matching (PM) wavelength and non-hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe₂BO₃F₂ (KBBF), an excellent UV NLO crystal, Mg(C₃O₄H₂)(H₂O)₂, was successfully synthesized in malonic system. This material possesses a unique 2D NLO-favorable electroneutral [Mg(C₃O₄H₂)₃(H₂O)₂]_∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water-resistant may be originated from its small available cavity volumes, which is similar to the famous LiB₃O₅ (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.