Dyes in modern organic chemistry

• Heiko Ihmels

Beilstein J. Org. Chem. 2019, 15, 2798–2800, doi:10.3762/bjoc.15.272

• already in 1856 with Perkin's seminal synthesis of mauveine [1]. Since then, dye chemistry evolved into a highly interdisciplinary research area in organic chemistry. Especially the immediate commercialization of Perkin's discovery in a dye firm demonstrated already at that time the strong relationship

• between research on dyes and industrial chemistry [2][3][4]. As a result, the success and strength of several chemical companies are originally based on dye chemistry. Although the traditional dyeing of textiles, hair, food, cosmetics, photography or printer colors, etc. is still highly relevant, organic

• dyes also contribute as essential components in modern applications such as in OLEDs [5][6], solar cells [7][8], organic semiconductors [9], NLO materials [10], photopolymerization [11], or Chemistry 4.0 [12]. From its very beginning, dye chemistry is strongly connected to the scientific developments

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• tetrazolium dye, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (МТТ) or yellow tetrazole, to give insoluble formazan, which develops purple color particularly in living cells. Thus, the color gradient can serve to determine the degree of cytostatic activity (shift from proliferation to

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

• Nadezhda S. Demina,
• Nikita A. Kazin,
• Nikolay A. Rasputin,
• Roman A. Irgashev and
• Gennady L. Rusinov

Beilstein J. Org. Chem. 2019, 15, 2678–2683, doi:10.3762/bjoc.15.261

• light-harvesting dyes for dye-sensitized solar cells [1], electron-donating materials for bulk heterojunction solar cells [2][3][4], and p-type semiconductors for organic field-effect transistors [5][6][7]. Within the same context of organic semiconductor development, the bicyclic TT subunit has been

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• reliability. Recently, an accurate determination of photochemical quantum yields (QY) [26] was achieved for a commercially available diarylethene 1,2-bis(2,4-dimethyl-5-phenylthien-3-yl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene, labelled 1. Since then, this dye has been used as actinometer in the visible range

• the freshly prepared actinometer 1-c and nanoparticles. Practically, the preparation of the 1-o/c solution was achieved using bench-top UV source (TLC lamp), either on the UCNP-1 mixture or before mixing the dye with the UCNPs. Concentrations were standardized prior the photolysis experiments using

• mimic such a situation, we have designed an experiment with larger nanoparticles (35 nm) and dilute 1-c dye: an absorbance at 540 nm of 0.11 ([1-c] = 1.14 × 105 mol L−1) corresponds to number of dyes of 6800 molecules per femtoliter. The photoswitching of the actinometer 1-c was clearly observed

Plasma membrane imaging with a fluorescent benzothiadiazole derivative

• Pedro H. P. R. Carvalho,
• Jose R. Correa,
• Karen L. R. Paiva,
• Daniel F. S. Machado,
• Jackson D. Scholten and
• Brenno A. D. Neto

Beilstein J. Org. Chem. 2019, 15, 2644–2654, doi:10.3762/bjoc.15.257

• -soluble and selective bioprobe for plasma membrane imaging. The new compound was efficiently synthesized in a two-step procedure with good yields. The photophysical properties were evaluated and the dye proved to have an excellent photostability in several solvents. DFT calculations were found in

• better conjugation with the 4AP substituent at the C4 carbon of the BTD heterocyclic core. The ionic nature of the structure in combination with a hydrophilic anion (MeSO3−, methanesulfonate) and the presence of the hydrophilic domain (triethylene glycol monomethyl ether) make the dye a water-soluble BTD

• agreed well with the experimental data obtained for the newly developed dye. DFT calculations were also employed to forecast the lipophilic character of the dye utilizing several XCFs. Experimentally, lipophilicity can be measured by means of the logarithm of the n-octanol/water partition coefficient

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• , we extended our previously reported arylisoquinoline-derived organoboron dye platform with an additional axially linked aryl residue (see structures 16–19 in Figure 1) in the expectation to modulate the fluorescence properties and fluoride response of these dyes. The additional aryl residues allow

• * transition bands in the wavelength range of 330–400 nm with characteristic vibronic fine structure were observed. Further, the dyes have a sharp peak at 322 nm that is assigned to the isoquinoline chromophore. The only exception is dye 18 where this peak is hidden under a strong absorption band corresponding

• -containing substituent. This follows from the observation that the corresponding arylisoquinolines without boron substitution feature only one blue-shifted emission band that is very similar to the SW band of the borylated dye, e.g., the non-borylated analogues of the dyes 17, 18, and 19 feature a single

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• Cancer Consortium (DKTK), Heidelberg, Germany 10.3762/bjoc.15.250 Abstract Background: Silicon rhodamines are of particular interest because of their advantageous dye properties (fluorescence- and biostability, quantum efficiency, tolerance to photobleaching). Therefore, silicon rhodamines find frequent

• could also be successfully applied for optical imaging of a xenograft tumor (human malignant meningioma) in a mouse model [24]. Again, in direct comparison with the cyanine dye Cy5.5, the silicon rhodamine conjugate showed no fading indicating that silicon rhodamine dyes are more suitable for long time

• added the double Grignard reagent 4 to methyl esters 5 [26]. A similar approach was established by Lavis, herein electrophiles (anhydrides or esters) were added to lithium or magnesium organyls 4 [27]. Johnsson and co-workers could establish dye formation by addition of aryllithium 7 to the silicon

Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red

• Aydan Yadigarli,
• Qimeng Song,
• Sergey I. Druzhinin and
• Holger Schönherr

Beilstein J. Org. Chem. 2019, 15, 2552–2562, doi:10.3762/bjoc.15.248

• films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the

• NR molecules in the ground state and slow sub-glass transition (Tg) relaxations in PMMA. Keywords: charge transfer; dipole moment; fluorescence; inhomogeneous broadening; oxazine dye; polarity probe; polymer permittivity; Introduction The chain and segment mobility as well as the permittivity of

• substrate-supported ultrathin films [13], the analysis of the photophysical properties of tracer dye molecules was found to be beneficial. In time-resolved fluorescence measurements and dye diffusion studies, the nanoenvironments in polymersomes could be assigned [1][12], solute transport be characterized

α,ß-Didehydrosuberoylanilide hydroxamic acid (DDSAHA) as precursor and possible analogue of the anticancer drug SAHA

• Shital K. Chattopadhyay,
• Subhankar Ghosh,
• Sarita Sarkar and
• Kakali Bhadra

Beilstein J. Org. Chem. 2019, 15, 2524–2533, doi:10.3762/bjoc.15.245

• with DAPI staining revealed a significant increase in nucleosomal fragmentation and nuclear condensation in 11b treated cells with increasing doses (Figure 6 upper panel) [39]. Furthermore, a cellular functional assay by JC-1 probe, a voltage sensitive fluorescent cationic dye, exhibits membrane

• inhibition) values of SAHA, 11b, 11f, 11g for HeLa cells (cervical carcinoma) were calculated by MTT (1 mg/mL of the tetrazolium dye, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide dissolved in phosphate-buffered saline, pH 7.4) assay [34]. Cells without any drug treatment were considered as

• with a fluorescence microscope [46]. Comet assays consist of mainly the following steps: slide preparation and cell lysis to liberate the DNA, DNA unwinding, electrophoresis, neutralization of the alkali, DNA staining. Dye used for electrophoresis: From 10 mg/mL stock solution of ethidium bromide 5 μL

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• salt (HPTS) dye (i.e., EYPC-LUVsHPTS) [57][58][59][60][61] was monitored by measuring the fluorescence intensity of the dye at λem = 510 nm (λex = 450 nm) with time (Figure S11, Supporting Information File 1). Thus, the addition of 2a (10 µM) resulted in the significant increase in HPTS fluorescence

• 2b. The influx of Cl‒ ion by these transporters were monitored using EYPC-LUVslucigenin. Additionally, compound 9, which has a free amino group and a free carboxylic acid group, was also subjected to the Cl‒ transport study. The Cl– sensitive dye lucigenin, was entrapped within the lipid vesicles and

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• the use in multimodal (PET/OI) medical imaging of mitochondria in cancerous cells. Results: A dihalogenated fluorinatable pyridinyl rhodamine could be successfully synthesized with the high yield of 85% by application of a halogen dance (HD) rearrangement. The near-infrared dye shows a quantum yield

• coefficient >0.8). The dye is suitable for live cell STED nanoscopy imaging and shows a nontoxic profile which makes it an appropriate candidate for medical imaging. Conclusions: We present a biocompatible, nontoxic, small molecule near-infrared dye with the option of subsequent radiolabelling and excellent

• features with their optical properties and control the latter by rational dye design [15][24][25][26]. These investigations led to new silicon rhodamine dyes with enhanced and fine-tuned properties (quantum yield, lifetime, brightness, absorption and emission maxima). A recent review compared the

Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes

• Marco Santella,
• Eduardo Della Pia,
• Jakob Kryger Sørensen and
• Bo W. Laursen

Beilstein J. Org. Chem. 2019, 15, 2133–2141, doi:10.3762/bjoc.15.210

• bridges leading to sulfur-functionalized acridinium, xanthenium or triangulenium dyes. For all the dye classes the sulfur functionalities are found to lead to intensely absorbing dyes in the visible range (470 to 515 nm), quite similar to known analogous dye systems with dialkylamino donor groups in place

• , synthesis and studies of organic fluorescent dyes have witnessed a revival in recent years, in particular due to their applications in imaging and biomedical assays and analytical techniques [1][2][3][4][5]. The desire to detect minute amounts of dye, ideally single molecules [6][7], in complex biological

• fluorescence lifetime has been a key point of interest since it enables time-gated detection for suppression of autofluorescence [25][26] and provides attractive advantages in fluorescence polarization assays [13][27][28]. A common characteristic feature of triangulenium dye synthesis is the use of methoxy

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• light range between 520 nm and 640 nm. The irradiation by visible light together with the use of an organic dye instead of a transition metal complex as photoredox catalyst improve the sustainability and make photoredox catalysis “greener”. Keywords: chromophore; dyes; electrochemistry; photochemistry

• but also by their photophysical dynamics. To the best of our knowledge this is the first report on the usage of cNDIs as photoredox catalysts. The irradiation by visible light from LEDs as energy-saving light sources together with the use of an organic dye instead of a transition metal complex as

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

• Silvie Rimpelová,
• Michal Jurášek,
• Lucie Peterková,
• Jiří Bejček,
• Vojtěch Spiwok,
• Miloš Majdl,
• Michal Jirásko,
• Miloš Buděšínský,
• Juraj Harmatha,
• Eva Kmoníčková,
• Pavel Drašar and
• Tomáš Ruml

Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189

• decreased the viability of rat peritoneal macrophages to 67% (*P < 0.05) at 40 µM concentration. It seems that this phenomenon was not related to the fluorescent dye of compound 5, since dansyl amide itself did not change the viability of rat macrophages at both concentrations. A decrease in cell viability

• in section “Cell uptake study”. To assess the intracellular localization of compound 5 in MRC-5 cells, an endoplasmic reticulum marker ER-Tracker™ Red (120 nM, 30 min; ThermoFisher Scientific, USA) and a mitochondria-specific dye (70 nM, 30 min; UCT Prague, CZ) from [20] were used. In U-2 OS cells

• -specific dye from [20] (10 min; image C) or pDNA coding mCherry-ER (image G). D, H) merged images. Cartoon representation of sarco/endoplasmic reticulum Ca2+ ATPase binding pocket with A, C) archangelolide (1) or B, D) trilobolide (2) after molecular dynamic simulations. Depicted are also amino acid

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• solvents. Strong bathochromic and hyperchromic effects in the visible spectra accompany the 1:1 formation of complexes with some alkaline earth metal ions. Keywords: amide group; azo dye; molecular sensor; sidearm; tautomerism; Introduction The design of new organic sensing systems is an undividable part

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• fluorescence intensity in the presence of one or another G4-DNA or RNA structure, while no dye displayed preferential response to double-stranded DNA or single-stranded RNA analytes employed at equivalent nucleotide concentration. Thus, preferential fluorimetric response towards G4 structures appears to be a

• (up to 150 nm) and, in certain cases, structural selectivity with respect to one or another G4 folding topology. These dyes can be considered as promising G4-responsive sensors for in vitro or imaging applications. As a possible application, we implemented a simple two-dye fluorimetric assay allowing

• . Along these lines, we have previously reported that cationic styryl-type dyes, such as distyrylpyridinium derivatives 1a and 2a (Figure 1) represent a promising starting point for the development of fluorescent probes selective for a variety of G4-DNA structures [58]. Another distyryl dye, namely

A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes

• Joza Schmitt and
• Scott T. Handy

Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171

• used yellow dye (tartrazine), the aurones are similar to more toxic. Within the aurone series, though, an interesting pair of trends can be observed. First, all hydroxylated aurones are comparatively more toxic, displaying >50% inhibition at 200 μM. Methyl groups are similarly mostly more toxic. For

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• were computed by density functional theory modelling (DFT) and characterized through UV–vis spectroscopy and cyclic voltammetry (CV) measurements. Finally, we report preliminary results obtained using these functional dyes as photosensitizers in dye-sensitized solar cells (DSSCs). Keywords: boron

• -dipyrromethene; BODIPY; dye-sensitized solar cells; near-infrared absorbers; organic dyes; Introduction The past two decades have witnessed tremendous efforts to develop alternative photovoltaic (PV) technologies. Among them, dye-sensitized solar cells (DSSCs) display numerous advantages compared to its fully

• liquids are employed [4][5]. Besides, this technology enables the fabrication of solar panels that can be prepared semi-transparent, colorful, and out of non-toxic constituents [6]. Historically, Ru(II)–polypyridyl complexes were the most used dyes as photosensitizers in DSSCs (N719 or N749 Black Dye) [7

Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)₂A fluorescent dyes

• Keiichi Imato,
• Toshiaki Enoki,
• Koji Uenaka and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2019, 15, 1712–1721, doi:10.3762/bjoc.15.167

• polarity (i.e., positive fluorescence solvatochromism). The Lippert–Mataga plots for OUY-2, OUK-2 and OUJ-2 indicate that the Δμ (= μe − μg) value, which is the difference in the dipole moment of the dye between the excited (μe) and the ground (μg) states, increases in the order of OUY-2 < OUK-2 < OUJ-2

• ][18][19][20][21][22][23][24], and a promising photosensitizer for dye-sensitized solar cells (DSSCs) [25][26][27][28][29][30][31][32][33][34]. Thus, in this work, to gain insight into the photophysical and electrochemical properties of D–π–A fluorescent dyes with an azine ring as electron-withdrawing

• solvents are fairly large (Table 1). Thus, the fact indicates that the (D–π–)2A fluorescent dyes have advantageous characteristics as emitters for OLEDs and fluorescence probes for biological imaging. It is well accepted that the dipole–dipole interactions between the fluorescent dye and the solvent

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• intramolecular charge-transfer dyes. Phosphated tetraphenylethylene was involved as the classical aggregation-induced emission dye. Sulfonated acedan representing one example of two-photon fluorescent probes, was also investigated. A ruthenium(II) complex with carboxylated bipyridyl ligands was included as a

• representative candidate of luminescent transition-metal complexes. We determined the association constants of the GC5A–dye complexes by fluorescence titration and discuss the complexation-induced photophysical changes. In addition, a comparison of the complexation behavior of GC5A with that of other macrocycles

• use and high sensitivity, and has been widely used in fields of chemistry, biomedicine, environment, and so on [1]. Generally, the conversion of a luminescent dye to a chemosensor requires a grafting recognition motif for a particular analyte, whose installation often involves laborious and time

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• selectivities; they have demonstrated excellent complex ability towards inorganic cations, organic ammonium cations, pyridinium guests, neutral molecules (alcohols, ketones, nitriles), dye molecules, etc. [26]. p-Sulfonatocalix[n]arenes are complexing agents for structurally diverse biologically active

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• which a substrate passes through the microreactor without interacting. In some cases, this residence time is measured by the time a dye needs to pass through the reactor. In this work, it was calculated by dividing V0 by the used flow rate (Φ) of 2.5 µL/min. The study of the Michael reaction under

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• widely used in the dye industry and have been applied as advanced materials in the fields of fluorescence labeling [58][59], organic semiconducting devices [60][61], and light harvesting [62][63][64][65]. PDI and NDI units have been extensively incorporated into functional supramolecular architectures

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• . First of all, the azacrown nitrogen atom is linked directly to the dye and it is part of the chromophore system, responsible for the “push–pull” effect and the photophysical properties of the dye. This provides control over the “push–pull” effect in the chromophore by switching on and off states (i.e

• defined their photophysical behavior in neat acetonitrile (ACN) solution and in the presence of barium cations. Figure 1 shows the absorption spectra of dyes 4a–d measured at different concentrations (cM) of Ba(ClO4)2. All dye solutions have similar absorption profiles with a broad long wavelength band in

• chromoionophore and the spectra in Figure 1 were assigned to the formation of the trans-dye–Ba2+ complex [19]. For all dye solutions, a distinct isosbestic point upon titration was observed, indicating only one kind of complex formation even at the highest Ba2+ concentration. To determine the optimal Ba2

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• enables them to be effective hosts for a wide range of guest molecules including organic biscarbonyl derivatives, near-infrared dyes, acenes, precious metal halide complexes, trimethylammonium ion-pairs, and saccharides. Keywords: fluorescent dye; host–guest chemistry; hydrogen bonding; hydrophobic

• acene guests Rotaxane template 18 in Scheme 2 is a squaraine dye whose central core has two oxygen atoms that can form hydrogen bonds with the tetralactam NH residues. Squaraine rotaxanes were first prepared by the Smith group in 2005 using the Leigh-type clipping method [44]. As a general trend the

• photophysical property of a squaraine dye is improved when it is encapsulated by tetralactam A, B, or C, but squaraine fluorescence is quenched when the dye is encapsulated by tetralactam E whose structure has extremely electron-rich sidewalls [34]. The moderate flexibility of tetralactam A is one of the