J. Appl. Cryst.の発刊に際して

Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Luminescent chemodosimeters for bioimaging.

During the past decade, fluorescent chemosensors have become an important research field of supramolecular chemistry and have attracted great attention because of their simplicity, high selectivity and sensitivity in fluorescent assays. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Based on different photophysical processes, conventional sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), metal–ligand charge transfer (MLCT), twisted intramolecular charge transfer (TICT), electronic energy transfer (EET), fluorescence resonance energy transfer (FRET), and excimer/exciplex formation have been investigated and reviewed extensively in the literature. This tutorial review will mainly focus on new fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and CN isomerization, which can be ascribed to fluorescence changes via conformational restriction. In addition, excited-state intramolecular proton transfer (ESIPT) has not been well reviewed yet, although a number of chemosensors based on the ESIPT mechanism have been reported. Thus, ESIPT-based chemosensors have been also summarized in this review.

New sensing mechanisms for design of fluorescent chemosensors emerging in recent years

Quantitative determination of specific analytes is essential for a variety of applications ranging from life sciences to environmental monitoring. Optical sensing allows non-invasive measurements within biological milieus, parallel monitoring of multiple samples, and less invasive imaging. Among the optical sensing methods currently being explored, ratiometric fluorescence sensing has received particular attention as a technique with the potential to provide precise and quantitative analyses. Among its advantages are high sensitivity and inherent reliability, which reflect the self-calibration provided by monitoring two (or more) emissions. A wide variety of ratiometric sensing probes using small fluorescent molecules have been developed for sensing, imaging, and biomedical applications. In this research highlight, we provide an overview of the design principles underlying small fluorescent probes that have been applied to the ratiometric detection of various analytes, including cations, anions, and biomolecules in solution and in biological samples. This highlight is designed to be illustrative, not comprehensive.

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Small molecule-based ratiometric fluorescence probes for cations, anions, and biomolecules

Recently, organic fluorescent molecules harnessing the excited-state intramolecular proton transfer (ESIPT) process are drawing great attention due to their unique photophysical properties which facilitate novel optoelectronic applications. After a brief introduction to the ESIPT process and related photo-physical properties, molecular design strategies towards tailored emission are discussed in relation to their theoretical aspects. Subsequently, recent studies on advanced ESIPT molecules and their optoelectronic applications are surveyed, particularly focusing on chemical sensors, fluorescence imaging, proton transfer lasers, and organic light-emitting diodes (OLEDs).

Advanced Organic Optoelectronic Materials: Harnessing Excited-State Intramolecular Proton Transfer (ESIPT) Process

Condensation of 2-(2‘-aminophenyl)benzoxazole with p-toluenesulfonyl chloride and phenyl isocyanate yields two new anion sensors (TABO and PUBO), which can undergo excited-state intramolecular proton transfer (ESIPT) upon excitation. For the acid receptor TABO, the ESIPT process can be readily disturbed by basic anions such as F-, CH3COO-, and H2PO4- by deprotonating the sulfonamide unit, whereas in the case of PUBO, a good hydrogen-bonding donor, the ESIPT process is inhibited either by the fluoride-induced deprotonation of the urea unit or by the formation of a strong CH3COO-−urea intermolecular hydrogen bond complex, and these two types of inhibition mechanisms consequently result in different ratiometric responses. But other anions with less hydrogen-bonding acceptor abilities cannot inhibit the ESIPT. Interestingly, the different inhibition abilities of F-, CH3COO-, and H2PO4- produce different spectral behaviors in PUBO, so this new sensor successfully distinguishes the subtle difference in these th...

Fluorescence sensing of anions based on inhibition of excited-state intramolecular proton transfer

In the title compound, C10H9BF2N2, a boron–dipyrromethene (BODIPY) dye, a network of C—H⋯F inter­actions help to establish the crystal packing The asymmetric unit consists of two molecules

4,4-Difluoro-8-methyl-4-bora-3a,4a-diaza-s-indacene

The title compound, C35H38N4O3, was prepared as a spiro­lactam ring formation of rhodamine dye for comparison with a ring-opened form. The xanthene ring system is approximately planar. The dihedral angles formed by the spiro­lactam and phenol rings with the xanthene ring system are 85.7 and 109.4°, respectively. Each of the mol­ecules in the crystal structure contains one intra­molecular O—H⋯N hydrogen bond, and they form inter­molecular N—H⋯O hydrogen-bonded chains along the [100] direction. Weak inter­molecular C—H⋯O hydrogen-bonding contacts connect the infinite chains via crystallographic inversion centres to form a two-dimensional network.

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[(2-{[3',6'-Bis(ethyl-amino)-2',7'-dimethyl-3-oxospiro-[1H-isoindole-1,9'-9H-xanthen]-2-yl}eth-yl)amino-meth-yl]phenol.

In the crystal structure of the title compound, C31H37N3O2, the dihedral angle between the planes of the xanthene ring system and the spiro­lactam ring is 90.3°.

3′,6′‐Bis(diethylamino)‐2‐propylspiro[isoindoline‐1,9′‐xanthen]‐3‐one

The title compound, [Fe2(C15H11S)2(CO)6], has been prepared as a structural model for the iron hydrogenase active site. The asymmetric unit consists of two mol­ecules. The Fe2S2 units in both mol­ecules exhibit a butterfly conformation.

Shang Gao

Papers

Fluorescence sensing of anions based on inhibition of excited-state intramolecular proton transfer

4,4-Difluoro-8-methyl-4-bora-3a,4a-diaza-s-indacene

[(2-{[3',6'-Bis(ethyl-amino)-2',7'-dimethyl-3-oxospiro-[1H-isoindole-1,9'-9H-xanthen]-2-yl}eth-yl)amino-meth-yl]phenol.

3′,6′‐Bis(diethylamino)‐2‐propylspiro[isoindoline‐1,9′‐xanthen]‐3‐one

Bis(μ‐9‐anthrylmethylthiolato)bis[tricarbonyliron(I)](Fe—Fe)