Search

Two thioxanthone-based fluorescent probes exhibited prominent solvatofluorochromism, and they were further found to be useful as fluorescence indicators for the qualitative and quantitative detection of low-level water content in various solvent media. [ABSTRACT FROM AUTHOR]

Herein, we introduce the cyclic 8π‐electron (C8π) molecule N,N′‐diaryl‐dihydrodibenzo[a,c]phenazine (DPAC) as a dual‐functional donor to establish a series of new donor–linker–acceptor (D–L–A) dyads DLA1–DLA5. The excited‐state bent‐to‐planar dynamics of DPAC regulate the energy gap of the donor, while the acceptors A1–A5 are endowed with different energy gaps and HOMO/LUMO levels. As a result, the rate and efficiency of the excited‐state electron transfer vs. energy transfer can be finely harnessed, which is verified via steady‐state spectroscopy and time‐resolved emission measurements. This comprehensive approach demonstrates, for the first time, the manifold of excited‐state properties governed by bifunctional donor‐based D–L–A dyads, including bent‐to‐planar, photoinduced electron transfer (PET) from excited donor to acceptor (oxidative‐PET), fluorescence resonance energy transfer (FRET), bent‐to‐planar followed by electron transfer (PFET), and PET from donor to excited acceptor (reductive‐PET). [ABSTRACT FROM AUTHOR]

Herein, we introduce the cyclic 8π‐electron (C8π) molecule N,N′‐diaryl‐dihydrodibenzo[a,c]phenazine (DPAC) as a dual‐functional donor to establish a series of new donor–linker–acceptor (D–L–A) dyads DLA1–DLA5. The excited‐state bent‐to‐planar dynamics of DPAC regulate the energy gap of the donor, while the acceptors A1–A5 are endowed with different energy gaps and HOMO/LUMO levels. As a result, the rate and efficiency of the excited‐state electron transfer vs. energy transfer can be finely harnessed, which is verified via steady‐state spectroscopy and time‐resolved emission measurements. This comprehensive approach demonstrates, for the first time, the manifold of excited‐state properties governed by bifunctional donor‐based D–L–A dyads, including bent‐to‐planar, photoinduced electron transfer (PET) from excited donor to acceptor (oxidative‐PET), fluorescence resonance energy transfer (FRET), bent‐to‐planar followed by electron transfer (PFET), and PET from donor to excited acceptor (reductive‐PET). [ABSTRACT FROM AUTHOR]

Searching for eight-membered ring π-conjugated hydrogen bonding (8-MR H-bonding) systems with excited-state intramolecular proton transfer (ESIPT) property is seminal and synthetically challenging. In this work, a series of π-conjugated molecules ( 8-HB-1, 8-HB-L1 and 8-HB-2) potentially possessing 8-MR H-bonding are strategically designed, synthesized and characterized. The configurations of these three potential molecules are checked by their X-ray structures, among which 8-HB-L1 (a structurally locked 8-HB-1 core chromophore) is proved to be an 8-MR H-bonding system, whereas 8-HB-1 and 8-HB-2 are too sterically hindered to form the 8-MR intramolecular H-bond. The ESIPT property of 8-HB-L1 is confirmed by the dual fluorescence consisting of normal and proton-transfer tautomer emissions. The insight into the ESIPT process of 8-HB-L1 is provided by femtosecond fluorescence upconversion measurements together with computational simulation. The results demonstrate for the first time a successful synthetic route to attain the 8-MR H-bonding molecule 8-HB-L1 with ESIPT property. [ABSTRACT FROM AUTHOR]

Exploring the conformational evolution of organic molecules is a long-pursuit theme in the field of chemistry. Herein, interests are endeavored to unveil the conformational evolution of conformationally flexible dihydrophenazines with environment-sensitive and continuously-changeable fluorescence in the confined space exerted by the semi-rigid macrocyclic host ExBox4+. Co-crystals of the ExBox4+ and dihydrophenazines are obtained via vapor diffusion, facilitating direct clarification of the structural variations of the host and guests. The adaptive ground-state conformational evolution of the guests is fully deciphered via 1H NMR titration, crystallography analysis as well as systematic theoretical calculations. In contrast to the much smaller structural change of the well-noted conformationally adaptive host, the conformational variation in the central dihedral angle of the guest can be up to 22° in the crystal of the host-guest complex, which is completely different from the cases when ExBox4+ interacting with the rigid guests. Dynamic information encryption has been further achieved by harnessing the distinct fluorescence behaviors before and after host-guest complexation. This work not only provides new insights into the understanding of mutual interactions between a semi-rigid host and conformationally flexible guests, but also offers an alternative scheme for advanced information encryption based on the luminescent host-guest complexes. [Display omitted] • A novel host-guest system has been developed with a type of butterfly-like guests. • These molecular butterflies show conformational self-adaptivity in the confined space. • Mutual interactions between semi-rigid macrocycle and flexible guests are clarified. • Advanced information encryption is achieved based on the fluorescence change associated with the combination and dissociation. [ABSTRACT FROM AUTHOR]

Organic small‐molecule fluorophores with near‐infrared IIa (NIR‐IIa) emission have great potential in pre‐clinical detection and inoperative imaging due to the high‐spatial resolution and deep penetration. However, developments of the NIR‐IIa fluorophores are still facing considerable challenges. In this work, a series of diketopyrrolopyrrole (DPP)‐based fluorophores were designed and synthesized. Subsequently, nanomaterial T25@F127 with significant NIR‐IIa emission properties was rationally prepared by encapsulating DPP‐based fluorophore T25, and was selected for fluorescence angiography and cerebral vascular microscopic imaging with nearly 800 μm penetrating depth and excellent signal‐background ratio of 4.07 and 2.26 (at 250 and 400 μm), respectively. Furthermore, the nanomaterial T25@cRGD with tumor targeting ability can image tiny metastatic tumor on intestine with a small size of 0.3 mm×1.0 mm and high‐spatial resolution (SBR=3.84). This study demonstrates that the nanomaterials which encapsulated T25 behave as excellent NIR‐IIa fluorescence imaging agents and have a great potential for in vivo biological application. [ABSTRACT FROM AUTHOR]

A novel colorimetric and fluorometric probe L1 for detecting CN− with high selectivity was constructed and synthesized based on intramolecular charge transfer (ICT). Remarkably, L1 was found to be exclusively responsive to CN− via nucleophilic attack of dicyanovinyl group via 1H NMR titration experiment. The detection system exhibited "turn-on" fluorescence with the addition of cyanide, which was opposite to previously reported fluorescence quenching probes with the same sensing process. Moreover, the detection limit of L1 for CN− was determined to be 1.1 μM, lower than the standard (1.9 μM) regulated by the World Health Organization (WHO). This work demonstrated that L1 could serve as both a colorimetric and a fluorimetric sensor for cyanide detection in pure water, making it possible for the applications of cyanide detection in water. Image 1 • A novel fluorescence "turn-on" probe for detecting cyanide was constructed based on intramolecular charge transfer.. • The probe can act as a colorimetric and a fluorimetric sensor in nearly pure water with the assistance of CTAB. • The probe possessed high selectivity for the detection of cyanide. [ABSTRACT FROM AUTHOR]