A Near InfraRed Emissive Chemosensor for Zn2+ and Phosphate Derivatives Based on a Di-(2-picolyl)amine-styrylflavylium Push-Pull Fluorophore

Abstract

A new Near InfraRed (NIR) fluorescent chemosensor for metal ions and anions is herein presented. The fluorophore is based on a styrylflavylium dye, a synthetic analogue of the natural anthocyanin family, with a di-(2-picolyl)amine (DPA) moiety as the metal chelating unit. The substitution pattern of the styrylflavylium core (with tertiary amines on positions 7 and 4′) shifts the optical properties of the dye towards the NIR region of the electronic spectra, due to a strong push-pull character over the π-conjugated system. The NIR chemosensor is highly sensitive to the presence of Zn2+, which induces a strong CHelation Enhanced Fluorescence (CHEF) effect upon binding to the DPA unit (2.7 fold increase). The strongest competing ion is Cu2+, with a complete fluorescence quenching, while other metals induce lower responses on the optical properties of the chemosensor. Subsequent anion screening of the Zn2+-chemosensor coordination compound has demonstrated a distinct selectivity towards adenosine 5′-triphosphate (ATP) and adenosine 5′-diphosphate (ADP), with high association constants (K ~ 106 M−1) and a strong CHEF effect (2.4 and 2.9 fold fluorescence increase for ATP and ADP, respectively). Intracellular studies with the Zn2+-complexed sensor showed strong luminescence in the cellular membrane of Gram– bacteria (E. coli) and mitochondrial membrane of mammalian cells (A659), which highlights its possible application for intracellular labelling.

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

“…Compound 2 was then converted to the boronic ester intermediate 3 in 41% yield over two steps: monobromination at the carbazole unit of 2 with NBS/ THF at low temperature giving the unisolated mixed brominated product followed by borylation with bis(pinacolato)diboron catalyzed by Pd(dpf)Cl 2 /KOAc. Finally, TPECNz was obtained as red solid in a reasonable yield by a Suzuki-type crosscoupling reaction between 3 and 4,9-dibromonaphtho [2,3c] [1,2,5]thiadiazole. The chemical structure and purity of com- pound 3 were verified by 1 H NMR, 13 C NMR, and high-resolution MALDI-TOF-MS techniques.…”

“…Recently, organic fluorophores with efficient deep-red/near-infrared (DR/NIR) emission properties (λ em = 650-900 nm) have received much attention due to their potential applications in several different fields such as chemosensing [1][2][3], bioimaging/ biosensing [4][5][6][7][8], photodynamic therapy [9], optical communication [10], NLO materials [11], laser dyes [12], and DR/NIR electroluminescent devices [13][14][15][16][17][18]. However, DR/NIR chromophores typically suffer from low photoluminescent quantum yields (PLQY) because of their intrinsic small band-gap energy causing larger vibronic coupling between the ground and excited states, particularly when they are applied as emitters in organic light-emitting diodes (OLEDs) [19].…”