2892-62-8Relevant academic research and scientific papers
An efficient general synthesis of squarate esters
Liu, Hiu,Tomooka, Craig S.,Moore, Harold W.
, p. 2177 - 2180 (1997)
An efficient and general method for the synthesis of alkyl squarates is presented. This involves the reactions of squaric acid with the desired alcohol in the presence of an orthoformate. This was applicable for the synthesis of dimethyl-, diethyl-, diisopropyl, di-n-butyl and di-t-butyl squarates in yields ranging from 77-97%. It is a convenient and safe method that can be accomplished on a multigram scale.
Synthesis, characterization and protein-association of dicyanomethylene squaraine dyes
Martins, Tiago D.,Pacheco, Marlene L.,Boto, Renato E.,Almeida, Paulo,Farinha, José Paulo S.,Reis, Lucinda V.
, p. 120 - 129 (2017)
We prepared several new dicyanomethylene squaraine dyes derived from indolenine, benzothiazole and benzoselenazole, with different substituent groups. All the obtained dyes display intense and narrow absorption bands and bright fluorescence emission in the Vis/NIR region (665–716 nm) when dissolved in organic solvents, especially for the unsymmetrical dyes containing sulphur and selenium atoms. The use of synthesized squaraine dyes as fluorescent probes for detection of bovine serum albumin (BSA) and human serum albumin (HSA) was explored in Tris-HCl buffer solutions. We observed that all the dyes are non-emissive in buffer solution but become fluorescent in the presence of BSA or HSA proteins, with the emission intensity increasing proportionally to the protein concentration (0.00–1.22 μM). The most pronounced effect was observed for the symmetrical squaraine having two moieties of indolenine.
Synthesis, spectroscopic characterization and biological evaluation of unsymmetrical aminosquarylium cyanine dyes
Fri?es, Sofia,Silva, Amélia M.,Boto, Renato E.,Ferreira, Diana,Fernandes, José R.,Souto, Eliana B.,Almeida, Paulo,Ferreira, Luis F. Vieira,Reis, Lucinda V.
, p. 3803 - 3814 (2017)
New unsymmetrical aminosquarylium cyanine dyes were synthesized and their potential as photosensitizers evaluated. New dyes, derived from benzothiazole and quinoline, were prepared by nucleophilic substitution of the corresponding O-methylated, the key intermediate that was obtained by methylation with CF3SO3CH3 of the related zwitterionic unsymmetrical dye, with ammonia and methylamine, respectively. All three news dyes herein described displayed intense and narrow bands in the Vis/NIR region (693–714?nm) and their singlet oxygen formation quantum yields ranged from 0.03 to 0.05. In vitro toxicity, in Caco-2 and HepG2 cells, indicated that dark toxicity was absent for concentrations up to 5?μM (for the less active dye) or up to 1?μM (for the two more active dyes). The three dyes present potential as photosensitizers, differing in irradiation conditions and period of incubation in the presence of irradiated dye. The less active dye needs a longer irradiation period to exhibit phototoxicity which is only evident after longer period of contact with cells (24?h). However, the remaining two more active dyes produce higher phototoxicity, even at shorter incubation periods (1?h), with shorter irradiation time (7?min). Although in different extents, these dyes show promising in vitro results as photosensitizers.
Barbiturate squaraine dyes as fluorescent probes for serum albumins detection
Almeida, Paulo,Boto, Renato E. F.,Gomes, Vanessa S. D.,Gon?alves, Helena M. R.,Reis, Lucinda V.
, (2020/07/02)
Three indolenine-based barbiturate squaraine dyes were synthesized, characterized and subjected to photophysical studies, including their affinity with human serum albumin and bovine serum albumin as protein models in phosphate buffer solution. All dyes successfully interact with both proteins with high affinity binding constants. It was found that dyes with hydrophobic substituents had superior binding constants with both proteins. The fluorescence intensity of all dyes increased in the presence of both proteins which allowed the determination of detection and quantifications limits in the tens of nanomolar, using a protein concentration of 0–3.5 μM. Concerning to the study on the binding sites of the synthesized dyes using the warfarin and ibuprofen markers, the results of this study suggest that, one dye binds to both BSA binding sites while the two others dyes binds only to site I, and that all three dyes bind to both HSA binding sites.
Electro-optical Properties of Neutral and Radical Ion Thienosquaraines
Maltese, Vito,Cospito, Sante,Beneduci, Amerigo,De Simone, Bruna Clara,Russo, Nino,Chidichimo, Giuseppe,Janssen, René A. J.
supporting information, p. 10179 - 10186 (2016/07/19)
Thienosquaraines are an interesting class of electroactive dyes that are useful for applications in organic electronics. Herein, the redox chemistry and electrochromic response of a few newly synthesized thienosquaraines are presented. These properties are compared to those of the commercial 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine. The stability of the radical ions formed in electrochemical processes strongly affects these properties, as shown by cyclic voltammetry, in situ spectroelectrochemistry, and quantum chemical calculations. Furthermore, all of the dyes show aggregation tendency resulting in panchromatic absorption covering the whole UV/Vis spectral range.
Synthesis, spectroscopic characterization and photophysical study of dicyanomethylene-substituted squaraine dyes
Pisoni, Diego Dos Santos,Petzhold, Cesar Liberato,Abreu, Marluza Pereira De,Rodembusch, Fabiano Severo,Campo, Leandra Franciscato
experimental part, p. 454 - 462 (2012/09/08)
In this work, the synthesis and the photophysical study of novel symmetrical and unsymmetrical squaraine dyes is described. These dyes were prepared by base-catalyzed condensation reaction between 3H-indolium or benzothiazolium salts with dicyanomethylene squarate, derived from squaric acid. The photophysical behavior of the dyes was investigated using UV-Vis absorption and steady-state fluorescence in solution. Additionally, its association with albumin from bovine serum (bovine serum albumin [BSA]) was also investigated. The dyes present strong absorption in the red/infrared regions and fluorescence emission in the infrared region tailored by the electronic structure of the squaraine. Association experiments with bovine serum albumin indicate that the obtained squaraine dyes are suitable for protein detection in solution.
Bis(dicyanomethylene)squarate squaraines in their 1,2- and 1,3-forms: Synthesis, crystal structure and spectroscopic study of compounds containing alkali metals and tetrabutylammonium ions
de Oliveira, Vanessa E.,de Carvalho, Gustavo S.,Yoshida, Maria I.,Donnici, Claudio L.,Speziali, Nivaldo L.,Diniz, Renata,de Oliveira, Luiz Fernando C.
experimental part, p. 239 - 249 (2010/03/30)
In this paper, we describe a new synthetic methodology and the spectroscopic characterization of two squaraines 1,2- and 1,3-substituted, named sodium 1,2-bis(dicyanomethylene)squarate and sodium 1,3-bis(dicyanomethylene)squarate. The squaraine species are derived from 1,2-dihydroxycyclobuten-3,4-dione, also known as squaric acid. A modification in the synthetic route has been developed in order to improve the yield in the synthesis of the 1,3-derivative: the in situ use of the 1,3-dianilinesquarate intermediate. In both cases, an excess basic medium was added to the solution containing all the reactants. These squaraines consist of a cyanine-type chromophore with high thermal stability and several different spectroscopic properties. In addition, it was made a comparative analysis based on the spectroscopic study of the 1,3- and 1,2-compounds, as well as their derivatives with several metal alkalis (K+, Rb+, Mg2+, Ca2+, Sr2+ and Ba2+), besides tetrabutylammonium ion (TBA). The vibrational spectroscopic data demonstrate the centrosymmetric structure in solid state phase of the 1,3-compound due to non-coincidence between the infrared and Raman bands in the vibrational spectra. The crystal structures were also obtained for Ca2+ and Ba2+ ions with the 1,3-isomer. These salts crystallize in different space groups, also showing very distinct coordination properties and intermolecular interactions. This study provides a sound basis for the future expansion of structural and spectroscopic investigations of this interesting group of metal-ligand compounds as building blocks systems in supramolecular chemistry.
Design, synthesis and structure of new chiral squaric acid monoaminoalcohols and diaminoalcohols and their use as catalysts in asymmetric reduction of ketones and diketones
Zhou, Hai-Bing,Zhang, Ji,Lü, Shou-Mao,Xie, Ru-Gang,Zhou, Zhong-Yuan,Choi, Michael C.K,Chan, Albert S.C,Yang, Teng-Kuei
, p. 9325 - 9333 (2007/10/03)
Many chiral squaric acid aminoalcohols and C2-symmetric diaminoalcohols have been synthesized and their in situ formed chiral boron heterocycles have been used as catalysts for the enantioselective reduction of prochiral ketones and diketones by borane to give alcohols with up to 99% enantiomeric excess and 99% yield. The effects of solvent, catalyst-substrate ratio and temperature were also investigated.
Electrochemistry of squarate and thiosquarate dianions
Carre, B.,Paris, J.,Fabre, P. L.,Jourdannaud, S.,Castan, P.,et al.
, p. 367 - 374 (2007/10/02)
Squarate dianion C4O42- and its thiosquarate C4O(4-x)Sx2- (x=1, 2, 4) derivatives have been shown to be ligating agents towards metal ions.Their electrochemical properties in aprotic solvent (acetonitrile) is revisited, with the goal of generating radical-anions by anodic oxidation of the dianions.Among these compounds, only C4O42- leads by anodic oxidation to a radical-anion C4O4.-, stabilized by electron delocalization.The thioderivatives form disulfides by radical condensation which suggests that the electron is localized on the sulfur atoms.
Dithioquadrato-Komplexe von Kupfer(II) und Kupfer(I). Darstellung und Struktur von II(en)2>II(C4O2S2)2> und II(en)2(H2O)>2I4(C4O2S2)4>*2H2O
Krause, Ralf,Mattes, Rainer
, p. 490 - 496 (2007/10/02)
From aqueous solutions of potassium dithiosquarate and bis(ethylenediamino)copper(II) sulfate the following compounds have been obtained: II(en)2>II(C4O2S2)2> (2) and II(en)2(H2O)>2I4(C4O2S2)4>*2H2O (3).Their structures have been determined: Crystal data, 2, monoclinic, space group C2/c, a = 1914.5(6), b = 823.0(1), c = 1669.5(5) pm, β = 133.23(1) deg, Z = 4; 1809 reflections, R = 0.024. 3, triclinic, a = 779.2(3), b = 958.7(4), c = 1478.8(4) pm, α = 82.34(3), β = 82.68(2), γ = 73.47(3) deg, Z = 1; 3376 reflections, R = 0.045. 2 contains infinite chains of centrosymmetrical 2+ cations and bisphenoidal 2- anions. 2 shows ferromagnetic behaviour above 75 K.At lower temperatures antiferromagnetic coupling between the chains dominates. 3 contains isolated 2+ cations and tetrameric - anions.The anion consists of a chain of tetrahedrally and trigonally coordinated Cu(I) atoms with short Cu...Cu distances of 255.2(1) and 257.9(1) pm.The dithiosquarate ligands are stacked in pairs.
