Fluorinated squaraine as near-IR label with improved properties for the labeling of oligonucleotides

The Role of Small Molecules Containing Fluorine Atoms in Medicine and Imaging Applications

The fluorine atom possesses many intrinsic properties that can be beneficial when incorporated into small molecules. These properties include the atom's size, electronegativity, and ability to block metabolic oxidation sites. Substituents that feature fluorine and fluorine-containing groups are currently prevalent in drugs that lower cholesterol, relieve asthma, and treat anxiety disorders, as well as improve the chemical properties of various medications and imaging agents. The dye scaffolds (fluorescein/rhodamine, coumarin, BODIPY, carbocyanine, and squaraine dyes) reported will address the incorporation of the fluorine atom in the scaffold and the contribution it provides to its application as an imaging agent. It is also important to recognize radiolabeled fluorine atoms used for PET imaging in the early detection of diseases. This review will discuss the many benefits of incorporating fluorine atoms into small molecules and give examples of fluorinated molecules used in the pharmaceutical industry and imaging techniques.

Near-IR squaraine dye-loaded gated periodic mesoporous organosilica for photo-oxidation of phenol in a continuous-flow device

Periodic mesoporous organosilica (PMO) has been widely used for the fabrication of a variety of catalytically active materials. We report the preparation of novel photo-responsive PMO with azobenzene-gated pores. Upon activation, the azobenzene gate undergoes trans-cis isomerization, which allows an unsymmetrical near-infrared squaraine dye (Sq) to enter into the pores. The gate closure by cis-trans isomerization of the azobenzene unit leads to the safe loading of the monomeric dye inside the pores. The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution. Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light. By using the device, about 23% production of benzoquinone with 100% selectivity was achieved. The current research presents a prototype of transforming heterogeneous catalysts toward practical use.

Symmetrical and asymmetrical cyanine dyes. Synthesis, spectral properties, and BSA association study

New cyanines were prepared by an efficient and practical route with satisfactory overall yield from low-cost starting materials. The photophysical behavior of the cyanines was investigated using UV-vis and steady-state fluorescence in solution, as well as their association with bovine serum albumin (BSA) in phosphate buffer solution (PBS). No cyanine aggregation was observed in organic solvents or in phosphate buffer solution. The alkyl chain length in the quaternized nitrogen was shown to be fundamental for BSA detection in PBS in these dyes.

Solvatochromic behavior of some α-styrylpyridinium dyes

The influences of solvent polarity and substituent on the electronic transition of six different N-butyl-α-styrylpyridinium dyes have been investigated in 21 solvents. Reichardt's E(T)(30) scale has been used to propose a quantitative approach towards the relative stability of the electronic ground and excited state species. The solvents have been classified into three types and the dyes have been classified into four groups based on the contribution of field and inductive effects of the substituents towards the change in their absorption maxima values. Instead of a steady solvatochromism, all the dyes except p-nitro substituted one, suffer reversals in solvatochromism at E(T)(30) values of ~37 and ~48. The extents of contribution of non-polar and polar protic solvents towards the solvation of the excited states of the dye molecules have been determined to be 30-40% more than that towards the stability of their ground states by the dipolar aprotic solvents. The ortho effect shown by this class of dyes in contrast to their corresponding γ-isomers might have been responsible for their better solvent polarity sensing capability.

Synthesis and properties of squaraine-modified DNA

The incorporation of squaraines into DNA via the phosphoramidite approach is described. High molar absorptivity, environment-sensitive fluorescence properties and intense CD effects render squaraines valuable building blocks for DNA-based optical probes and nanostructures.