Supramolecular assembly of a new squaraine and β-cyclodextrin for detection of thiol-containing amino acids in water

Abstract

2011) Supramolecular assembly of a new squaraine and β-cyclodextrin for detection of thiol-containing amino acids in water, Supramolecular Chemistry, 23:9, 657-662, A new unsymmetrical aniline-based squaraine (SQ2) bearing binding unit of Hg 2þ ion was designed and synthesised. SQ2 can form 1:2 inclusion complex with b-cyclodextrin, and the resulting complex, which undergoes absorption and fluorescence bleaching upon binding Hg 2þ , can serve as a turn-on colorimetric or fluorescent chemosensor in organic solvent-free aqueous solution for thiol-containing amino acids with high selectivity and tunable measuring range.

Tuning thiol addition to squaraines by ortho-substitution and the use of serum albumin

“…Squaraines have been shown to be selective probes for thiols at physiological pH. [17][18][19][20][21][22][23][24][25][26][27][28] While the addition of thiols to squaraines do not undergo nucleophilic attack and are stable in solution. Phenol-derived squaraines can be electrophilic if the phenol ring is substituted with electron withdrawing groups such as halogens.…”

Squaraine-Based Optical Sensors: Designer Toolbox for Exploring Ionic and Molecular Recognitions

“…In contrast, SQS22, SQS23, and SQS24, which feature thio-ether-containing binding motifs, provided "turn-OFF" responses upon interaction with metal ions (Figure 4) [80][81][82]. Specifically, in CH 3 CN, SQS22 exhibited the following spectral characteristics that were consistent with monomeric species: a strong, narrow absorption band (λ ab max = 636 nm) and intense emission (λ em max = 670 nm) [80].…”

“…The observed cross-sensitivity of SQS22-Hg towards both SH-containing analytes and His prompted further studies that led to SQS23 [81], which was synthesized following the general routes utilized for non-symmetric squaraines (Scheme 2). Similarly to SQS22, in aqueous media, SQS23 was present in the form of non-emissive aggregates, which exhibited a broad absorption band in the 480-780 nm range.…”

“…In addition, the SQS23-β-CD-Hg assembly showed ca. three-fold selectivity towards SH-containing analytes (e.g., Cys, Hcys, and GSH) over His [81].…”

Assembly and functionalization of supramolecular polymers from DNA-conjugated squaraine oligomers

“…[30][31][32] Squarainebased systems therefore represent ideal candidates for the creation of such "long-wavelength" supramolecular materials. [33][34][35] Squaraine dyes exhibit molar absorptivities of up to 260 000 M À1 cm À1 , 36 they absorb and emit light in the longwavelength region of the visible spectrum and possess the well-documented property of forming aggregates in aqueous solutions. 37,38 Squaraine assemblies designed for biomedical applications are primarily based on copolymer systems.…”