Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• series of new styryl-based organic chromophores containing a free amino group and the corresponding Schiff base derivatives. The photophysical, pH sensitivity, NLO properties, and thermal stabilities of all synthesized dyes were investigated. Density Functional Theory (DFT) calculations were also

• employed to gain insight into the experimental data. Results and Discussion Synthesis As depicted in Scheme 1, dye 2 was obtained in good yield by reacting malononitrile and 4-aminoacetophenone (compound 1) according to our previous published procedure [31][32]. The styryl-based organic chromophores 3–7

• substantial delocalization of charges in this direction (Tables S2 and S3, Supporting Information File 1). Thermal properties The thermal stability is quite important for NLO chromophores when using them in electro-optic materials. Therefore, we conducted a thermogravimetric analysis to understand whether the

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• molecules in water. The absorption maxima and corresponding molar extinction coefficients (ε) are given in Table S1 (Supporting Information File 1). Heating of the aqueous solution of 4 up to 90 °C did not yield any significant changes in its UV–vis spectrum, suggesting that the chromophores are not

• for reaching thermodynamic equilibrium. It should be stressed that all changes in the 330–400 nm range could be attributed dominantly to the NDI chromophore, since absorbance of GCPs in this range is negligible. Absorbance changes of large aromatic chromophores upon DNA or RNA addition can happen for

• chromophores, the intrinsic CD spectrum of compound 4 at the 220–400 nm range is negligible. Further, for the analysis of the CD results we compared our data with those published for a close NDI-monomer analogue [26][27], whereby the strong positive ICD band at 270–280 nm was attributed to the intercalation of

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• [9]). One of the approaches relies on amino acids conjugated with various DNA/RNA-binding chromophores, thereby yielding effective spectrometric sensing systems due to their interactions with DNA. In this approach, chromophores can be combined with peptide sequences in various ways, thus giving

• access to large libraries of close analogues. Further, in such peptide-based chromophore systems, a multitude of different chromophores/fluorophores [10] could allow fine tuning of spectroscopic responses to various DNA/RNA sequences. With this concept in mind, Piantanida and co-workers recently

• predominantly a parallel orientation for all dyes as shown in Figure 8 for the DNA–3b complex. The absence of any measurable ICD signal for poly(A)-poly(U) (ds-RNA) (Supporting Information File 1, Figure S26) supports the intercalation of all NDI chromophores at approximately 45° with respect to the base pair

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• bind specifically to multistranded β-sheets [62][63]. PEP-1 is nonemissive due to the absence of chromophores in its molecular structure, whereas ThT shows a low fluorescence in PBS (pH 7.4) upon excitation at 440 nm. Interestingly, the fluorescence intensity of ThT significantly increases upon mixing

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• . The quantum yields were calculated based on Equation 1. where R means reference and S sample, respectively. Generally weak fluorescence emissions were observed for the thiophene-based chromophores due to a remarkable spin–orbit coupling which is originating from the heavy atom effect of sulfur [73][74

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• up to 67%, while their bandgaps and chiroptical responses could be tuned by twisting the bipyrrole chromophore. The solvatochromism and apparent superradiance of these chromophores indicated a potential involvement of solvent-induced symmetry-breaking charge transfer in the excited state [34]. Here

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• directly to the periphery of triptycene or via various linkers; arrays with six chromophores 3 have thus far eluded us [26][27]. While much work has been done on the functionalization of the aromatic rings of triptycene as in 2 or 3 [24][25][26][27][28][29][30], the attachment of chromophores at the

• Information File 1 for full experimental data). Instead we focused on the synthesis of systems with ethynyl spacers between the triptycene bridgehead positions and chromophores. To allow for the generation of symmetric and unsymmetric dyads 9,10-diethynyltriptycene 5 and its anthracene precursor were

• bridgehead positions of triptycenes in 5 (Scheme 1) and 12 (Scheme 2), efforts were made to attach various chromophores in order to investigate the effects of triptycene as a linker for electron transfer properties. With the goal of synthesizing various new triptycene-linked porphyrin and BODIPY dimers

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• the differential absorption of linearly polarized light, which was polarized parallel and perpendicular to a reference axis, respectively, thus indicating the orientation of the transition moment of the chromophores relative to the electric field vector of the light [75]. The LD spectrum of DNA-bound

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

• Sabrina Müller,
• Jannik Paulus,
• Jochen Mattay,
• Heiko Ihmels,
• Veronica I. Dodero and
• Norbert Sewald

Beilstein J. Org. Chem. 2020, 16, 60–70, doi:10.3762/bjoc.16.8

• did not induce ICD assigned to the polyamide chromophores, possibly because of the formation of small soluble aggregates. Z-P3, with a higher number of heterocyclic units, displayed some sequence specificity, albeit not in a range that was reported for other nonphotoswitchable polyamides. The (Z

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• ). The striking absence of exciton Cotton effects is in complete agreement with the high degree of parallelism between the chromophores, as observed in the crystal packing (Figure 5). Two chromophores can only be coupled under an exciton interaction if the angle between the 1La transitions is different

• from 0° or 180°, since this interaction is governed by an equation with a vectorial product. The lack of exciton pairwise interactions between the two chromophores in positions 1 and 2 of each molecule could be due to the intercalation of a third chromophore between the two former in a parallel

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• maintains the near-ideal chemical properties of Hecht’s 4FAB chromophores [12][13] (see below). The final synthetic challenge was the installation of a maleimide onto chromophore 2. The original AB photoswitchable probes which were cross-linked to cysteine mutants had amides with a reverse orientation [19

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• (Figure S3, Supporting Information File 1). On repeating this cycle, slow decomposition was observed, estimated at 14% after 3 cycles. Calcium binding by hosts 1E and 1Z was investigated by spectrophotometry, specifically monitoring aromatic ring chromophores which give rise to absorption bands observed

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• achieved [4]. Small molecule organic fluorophores are particularly advantageous due to the potential of a tailored fine-tuning of their photophysical properties through synthetic modifications [5]. Based on their structural features, functionalized organic chromophores, containing N-, O- or S-atoms, are

• molecular aggregation in the solid state causes fluorescence quenching [16]. In recent years, we have coined diversity-oriented syntheses of functional chromophores by multicomponent strategies [17][18], opening accesses to substance libraries for systematic studies of structure–property relationships on

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

• couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range

• ratiometric response by the build-up of a hypsochromically shifted emission signal. Keywords: anions; dyes; fluorescence; laser-flash photolysis; organoboron; Introduction Boron-containing tri- and tetra-coordinated chromophores have attracted considerable interest due to their often peculiar and highly

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• the PNAs, UV–vis spectroscopy of 20 μM solutions in phosphate buffer (10 mM NaH2PO4, 150 mM NaCl, pH 7.4) confirmed that PNA incorporation did not significantly affect the photochromism (Figures S24, S20, S30 and S33, Supporting Information File 1). This verifies the integrity of the chromophores

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• , thanks to through-space interactions. Modelling suggested that changing the relative orientation/distance of the chromophores would allow cooperative TPA enhancement to be achieved [51]. Thus, multistilbazole molecular structures of different topologies and number of dipolar chromophores, including small

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• Information File 1). When the electrolysis is performed at E1/22 + 0.15 V, the first band deriving from the π–π* transition of the NAr3•+ moiety increased in intensity (Supporting Information File 1, Figure S10), reflecting the presence of two chromophores in the generated two-electron-oxidized species 1b2

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

• efficiency was observed by Kotaskova et al. for fluorescein derivatives with one alkylthio group in the 3 position replacing an -OH/-O− group [51]. The origin of reduced fluorescence quantum yields in dyes with alkylthio donor groups in their chromophores is not clear at this point. It may result from

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• anti’-6 obtained from the reaction with diarylprolinol silyl ether (R)-18 (Table 1, entry 5) were analyzed using electronic circular dichroism spectroscopy (ECD) and TD-DFT methods. So-called in situ methodology with dimolybdenum tetraacetate (19) acting as auxiliary chromophores which proved a very

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

• solubility. In general, NDIs are electron-poor chromophores. The diamino substituents of cNDIs 2–6 are expected to increase the charge-transfer character of their photoexcited states in order to shift their absorption into the visible light and to improve their photoredox catalytic power. The photoredox

Multicomponent reactions III

• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1974–1975, doi:10.3762/bjoc.15.192

• of synthetic efficiency. Biologically and pharmaceutically relevant scaffolds are likewise tackled as chromophores, methodology development and conceptual design of macro(hetero)cycles go hand in hand with MCR-based heterocyclic chemistry. As in the previous thematic issues also this issue opens the

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• chemical introduction of chromophores onto the rims of pillar[5]arene has been applied to allow its use as receptors for molecular sensing or biological applications [30][31][32][33]. It occurred to us that connecting fluorophores with strong absorptions in the visible range and with a high fluorescence

• quantum yield are beneficial for the application of pillar[5]arene in these fields. Perylene (Py) and 9,10-diphenylanthracene (DPA) are well known for their desirable absorption and high fluorescence quantum yield. These chromophores possess unique photophysical properties and have been widely used as

• . Aggregates with an average diameter of 531 nm are formed in 60% water (Figure S23, Supporting Information File 1) [52]. Exciton coupling CD (ECCD) signals were not observed for both compounds, even when adding more than 90% water, demonstrating that the chromophores DPA or Py units were not asymmetrically

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• ingredients [8][9][10][11], as ligands [12][13], and as chromophores [14][15][16], the partially unsaturated 2H-pyrazolines have particularly attracted attention for instance as antibacterial [17], anti-inflammatory [18], antidiabetic [19], and antidepressive [20] agents. Especially, 1-acylpyrazolines have

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• spectroscopy was not possible due to the low absorption of bambusurils within the UV–vis region. Therefore, we decided to investigate the synthesis of bambusuril derivatives and analogs containing chromophores in their structure. Initially we tested post-macrocyclic functionalization resulting in bambusurils

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

• with their linear glycol chain counterparts, B21C7 shows great potential to be an easy-to-accessed building block to probe the non-covalent interactions and chemical transformations influenced by water molecules. Perylene diimide (PDI) and naphthalene diimide (NDI) are polycyclic aromatic chromophores

• state [93][94]. When more polar solvent MeCN or MeOH were used, merely a broad and very weak absorption band was observed. All the weak and disappearing bands indicate the overlapping of PDI chromophores to form J-type aggregates in polar solvents [84]. The intensities of the characteristic absorption