Porphyrin as a versatile visible-light-activatable organic/metal hybrid photoremovable protecting group.

Photoremovable protecting groups (PPGs) represent one of the main contemporary implementations of photochemistry in diverse fields of research and practical applications. For the past half century, organic and metal-complex PPGs were considered mutually exclusive classes, each of which provided unique sets of physical and chemical properties thanks to their distinctive structures. Here, we introduce the meso-methylporphyrin group as a prototype hybrid-class PPG that unites traditionally exclusive elements of organic and metal-complex PPGs within a single structure. We show that the porphyrin scaffold allows extensive modularity by functional separation of the metal-binding chromophore and up to four sites of leaving group release. The insertion of metal ions can be used to tune their spectroscopic, photochemical, and biological properties. We provide a detailed description of the photoreaction mechanism studied by steady-state and transient absorption spectroscopies and quantum-chemical calculations. Our approach applied herein could facilitate access to a hitherto untapped chemical space of potential PPG scaffolds.

A cell-permeant small molecule for the super-resolution imaging of the endoplasmic reticulum in live cells.

The endoplasmic reticulum (ER) constitutes about half of the total membrane of a eukaryotic cell, and defects in the ER have been shown to be linked with a variety of diseases. To investigate these underlying mechanisms in detail, the specific labelling of the ER for high-resolution long-term live-imaging can serve as an important tool. Here, we report the identification of a stimulated emission depletion (STED) microscopy-compatible BODIPY derivative (NH2-BODIPY) to selectively image the ER. In contrast to the conventional ER-Tracker™ dye, NH2-BODIPY selectively labels the ER at a much lower concentration with no detectable cytotoxicity. Conventional imaging agents are often unstable under the intense light field used for STED microscopy, but NH2-BODIPY is stable due to its robust structure and therefore it has the potential to be widely exploited for ER imaging.

Zwitterionic BODIPYs with large stokes shift: small molecular biomarkers for live cells.

The two first examples of zwitterionic BODIPYs have been synthesized via a simple SN-Ar methodology. The molecules exhibit excellent optical behavior, such as a large Stokes shift in solution and therefore a very intense emission, and can thus avoid self-quenching. The zwitterionic nature of the molecules was unambiguously elucidated using single crystal XRD studies. The electronic conjugation was investigated by NMR, DFT (NICS (0)) and XRD analysis. Due to their inherent ionic nature, their enhanced solubility in aqueous conditions was exploited for their utility in bio-imaging and cell viability studies. These molecules demonstrate promising localization inside live yeast cells.

Dual-mode chemodosimetric response of dibromo-BODIPY with anions.

Aromatic nucleophilic substitution (Ar-SN) reaction of 3,5-dibromopentafluorophenyl-BODIPY has been explored as a remarkable basis for selective discrimination of anions. The efficient and characteristic ability of anions to modulate the absorption and emission properties of the dye provides an instantaneous distinction through dual-modes. For the first time, a novel platform to achieve dual-modal and promising recognition with discrimination of a series of anions differing in the nucleophilic atoms (F, O, C and N) has been taken into consideration. The behaviour of various anions with dibromo-BODIPY and vivid signal transduction has been fully established with absorption and emission spectroscopy. In addition to this, recognition events have been unambiguously characterized by (1)H, (19)F-NMR and single-crystal XRD.

Aliphatic amine discrimination by pentafluorophenyl dibromo BODIPY.

Two new fluorescent BODIPY dyes have been designed and synthesized. They dyes differ in their meso substituents, which have different electronic properties. Their selective reactivity towards an Ar-S(N)2 reaction has been explored as a potential basis for colorimetric and fluorescent discrimination of primary, secondary and tertiary aliphatic amines. This dual-mode, instantaneous recognition event is unprecedented.