Monthly Archives: January 2024

Near‐infrared Emissive Indolizine Squaraine Fluorophores as Strong Molecular Viscosity Sensors

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Near-infrared Emissive Indolizine Squaraine Fluorophores as Strong Molecular Viscosity Sensors

A series of near-infrared absorbing and emitting indolizine squaraine fluorophores were designed and synthesized. The dyes were probed for their photophysical and electrochemical properties and observed to exhibit very high viscosity sensitivity.


Abstract

Changes in the viscosity of intracellular microenvironments may indicate the onset of diseases like diabetes, blood-based illnesses, hypertension, and Alzheimer's. To date, monitoring viscosity changes in the intracellular environment remains a challenge with prior work focusing primarily on visible light-absorbing viscosity sensing fluorophores. Herein, a series of near-infrared (NIR, 700–1000 nm) absorbing and emitting indolizine squaraine fluorophores (1PhSQ, 2PhSQ, SO3SQ, 1DMASQ, 7DMASQ, and 1,7DMASQ) are synthesized and studied for NIR viscosity sensitivity. 2PhSQ exhibits a very high slope in its Forster-Hoffmann plot at 0.75 which indicates this dye is a potent viscosity sensor. The properties of the squaraine fluorophores are studied computationally via density functional theory (DFT) and time-dependent (TD)-DFT. Experimentally, both steady-state and time-resolved emission spectroscopy, absorption spectroscopy, and electrochemical characterization are conducted on the dyes. Precise photophysical tuning is observed within the series with emission maxima wavelengths as long as 881 nm for 1,7DMASQ and fluorescence quantum yields as high as 39.5 and 72.0 % for 1PhSQ in DCM and THF, respectively. The high tunability of this molecular scaffold renders indolizine squaraine fluorophores excellent prospects as viscosity-sensitive biological imaging agents with 2PhSQ giving a dramatically higher fluorescence quantum yield (from 0.3 to 37.1 %) as viscosity increases.

Tunable Phosphorescence in Metastable CuI Assemblies Prepared by Acid‐Fueled Crystal‐to‐Crystal Conversion

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Tunable Phosphorescence in Metastable CuI Assemblies Prepared by Acid-Fueled Crystal-to-Crystal Conversion

In this work, we report new metastable CuI assemblies prepared by crystal-to-crystal conversion that exhibit temperature-dependent phosphorescence complexity.


Abstract

Acid acts as a “fuel” in driving kinetic self-assembly, with crystals of the CuII complex ([CuIICl2(BH)2], BH=benzothiadiazole helicene derivative) being successfully converted to crystals of 1 ([H2BH][CuBr3]) and 2 ([H2BH][CuBr3⋅2H2O]). The metastable features of 1 and 2 enable CuI guest release, with transformation into a thermodynamically favorable form 3 (H2BH⋅2Br). Compound 1 exhibits dual phosphorescence at 452 nm (3MC) and 709 nm (3CT) at room temperature. At lower temperatures, the 3CT band disappears and the 3MC band weakens, while a new emission band at 621 nm (3ππ*) is enhanced. In 1, the subtle structural change and significant emission change depending on temperature is reversible. In contrast, 2 exhibits only 3MC emission at room temperature, with less efficient triplet-triplet energy transfer (TTET) below 250 K, and with residual 3ππ* emission occurring upon returning to room temperature, even after one week.

Synthesis and characterization of a highly fluorescent benzofuran dimer derived from estradiol

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Synthesis and characterization of a highly fluorescent benzofuran dimer derived from estradiol

A steroid dimer bearing the 1,4-di(benzofuran-2-yl)benzene moiety obtained from estradiol showed an intense blue fluorescence band between 350 and 550 nm with a 18-fold-increased quantum yield compared with that of its synthetic precursor.


Abstract

Pd-catalyzed cyclization of a fluorescent dimer in which two cores of the potent estrogenic estradiol are bridged by the 1,4-diethynil benzene moiety led to a steroid dimer bearing the 1,4-di(benzofuran-2-yl)benzene. The obtained compound showed an intense blue fluorescence characterized by a broad emission band between 350 and 550 nm, with four maxima at 384, 403, 435, and 456 nm. The benzofuran dimer showed an 18-fold increased quantum yield compared with that of its synthetic precursor.

Application of the aza‐Wittig reaction for efficient synthesis of diversely substituted benzo[f]Chromeno[2,3‐d]pyrimidine and benzo[f]chromeno[2,3‐d][1,2,4]triazolopyrimidine derivatives

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Application of the aza-Wittig reaction for efficient synthesis of diversely substituted benzo[f]Chromeno[2,3-d]pyrimidine and benzo[f]chromeno[2,3-d][1,2,4]triazolopyrimidine derivatives

An effective iminophosphorane mediates the synthesis of a fused ring system with potent anticancer relevance via the Aza-Wittig reaction.


Abstract

An efficient synthesis of novel benzo[f]Chromeno[2,3-d]pyrimidine and unknown benzo[f]chromeno[2,3-d][1,2,4]triazolopyrimidine derivatives is described utilizing ethyl-2-amino-4-phenyl-4H-benzo[f]chromene-3-carboxylate as precursor via aza-Wittig reaction. The process proved to be simple, high-yielding, and efficient.

1,3‐Dipolar Cycloaddition of Polycyclic Aromatic Azomethine Ylides and Alkynylbenziodoxoles for Synthesis of Functional Dibenzoullazines

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1,3-Dipolar Cycloaddition of Polycyclic Aromatic Azomethine Ylides and Alkynylbenziodoxoles for Synthesis of Functional Dibenzoullazines†

A new family of dibenzoullazine derivatives was synthesized through 1,3-dipolar cycloaddition of polycyclic aromatic azomethine ylides with alkynylbenziodoxoles followed by oxidation. The benziodoxole moiety in the resulting products was used as a versatile linchpin for the synthesis of structurally diverse functional dibenzoullazines that are difficult to access by other synthetic methods.


Comprehensive Summary

A new family of dibenzoullazine derivatives was synthesized through 1,3-dipolar cycloaddition of polycyclic aromatic azomethine ylides with alkynylbenziodoxoles followed by oxidation. The benziodoxole moiety in the resulting products was used as a versatile linchpin for the synthesis of structurally diverse functional dibenzoullazines that are difficult to access by other synthetic methods.