Photophysical properties of 1-N-methylamino- and 1-N,N-dimethylamino-9,10-anthraquinone dyes: A comparison with 1-amino-9,10-anthraquinone dye

Synthesis and evaluation of photophysical, electrochemical, and ROS generation properties of new chalcogen-naphthoquinones-1,2,3-triazole hybrids

This study presents a comprehensive analysis encompassing the synthesis, structural elucidation, photophysical behavior, and electrochemical properties of a novel series of chalcogen-naphthoquinone-1,2,3-triazole hybrids. Employing a meticulously designed protocol, the synthesis of these hybrids, denoted as 11a-j, was achieved with remarkable efficiency (yielding up to 81%). This synthesis used a regioselective copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC). Furthermore, a detailed investigation into the photophysical characteristics, TDDFT calculations, electrochemical profiles, and photobiological attributes of compounds 11a-j was conducted. This exploration aimed to unravel insights into the excited state behaviors of these molecules, as well as their redox properties. Such insights are crucial for future applications of these derivatives in diverse biological assays.

Substituent Effects on Photoinitiation Ability of Monoaminoanthraquinone-Based Photoinitiating Systems for Free Radical Photopolymerization under LEDs

Three monoamino-substituted anthraquinone derivatives (AAQs), that is, 1-aminoanthraquinone (AAQ), 1-(methylamino)anthraquinone (MAAQ), and 1-(benzamido)anthraquinone (BAAQ), incorporated with various additives [e.g., triethanolamine (TEAOH) and phenacyl bromide (PhC(═O)CH₂ Br)] are investigated for their roles as photoinitiating systems of free radical photopolymerization of (meth)acrylate monomers upon the exposure to UV to green LEDs. The AAQs-based photoinitiating systems, AAQ/TEAOH/PhC(═O)CH₂ Br and BAAQ/TEAOH/PhC(═O)CH₂ Br photoinitiators exhibit the highest efficiency for the free radical photopolymerization of DPGDA under the irradiation of blue LED and UV LED, respectively, which is consistent with the extent of overlap between their absorption spectra and the emission spectra of the LEDs. AAQ/TEAOH/PhC(═O)CH₂ Br photoinitiator can also initiate the free radical photopolymerization of different (meth)acrylate monomers, with an efficiency dependent on the chemical structures of these monomers.

Design of "Click" Fluorescent Labeled 2'-deoxyuridines via C5-[4-(2-Propynyl(methyl)amino)]phenyl Acetylene as a Universal Linker: Synthesis, Photophysical Properties, and Interaction with BSA

Microenvironment-sensitive fluorescent nucleosides present attractive advantages over single-emitting dyes for sensing inter-biomolecular interactions involving DNA. Herein, we report the rational design and synthesis of triazolyl push-pull fluorophore-labeled uridines via the intermediacy of C5-[4-(2-propynyl(methyl)amino)]phenyl acetylene as a universal linker. The synthesized nucleosides showed interesting solvatochromic characteristic and/or intramolecular charge transfer (ICT) features. A few of them also exhibited dual-emitting characteristics evidencing our designing concept. The HOMO-LUMO distribution showed that the emissive states of these nucleosides were characterized with more significant electron redistribution between the C5-[4-(2-propynyl(methyl)amino)]phenyl triazolyl donor moiety and the aromatic chromophores linked to it, leading to modulated emission property. The solvent polarity sensitivity of these nucleosides was also tested. The synthesized triazolyl benzonitrile (10C), naphthyl (10E), and pyrenyl (10G) nucleosides were found to exhibit interesting ICT and dual (LE/ICT) emission properties. The dual-emitting pyrenyl nucleoside maintained a good ratiometric response in the BSA protein microenvironment, enabling the switch-on ratiometric sensing of BSA as the only protein biomolecule. Thus, it is expected that the new fluorescent nucleoside analogues would be useful in designing DNA probes for nucleic acid analysis or studying DNA-protein interactions via a drastic change in fluorescence response due to a change in micropolarity.

Spectroscopic investigation, photophysical parameters and DFT calculations of 4,4'-(1E,1'E)-2,2'-(pyrazine-2,5-diyl)bis(ethene-2,1-diyl)bis(N,N-dimethylaniline) (PENDA) in different solvents

A comprehensive investigation on the photophysics of a π-conjugated potential push-pull chromophore system 4,4'-(1E,1'E)-2,2'-(Pyrazine-2,5-diyl)bis(ethene-2,1-diyl)bis(N,N-dimethylaniline) (PENDA) has been carried out spectroscopically. The optical absorption and emission properties of this molecule have been studied in different solvents. The molecule PENDA shows strong solvatochromic emission upon changing the solvent polarity from nonpolar to polar; indicating that emission state is of intramolecular charge transfer (ICT) character. The solvent effect on the spectral properties such as singlet absorption, molar absorptivity, oscillator strength, dipole moment and fluorescence quantum yield of PENDA have been studied in detail. Lippert-Mataga and Reichardt correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). Ground and electronic excited states geometric optimizations were performed using density functional theory (DFT) and time-dependent density functional theory (TDDFT), respectively, with the Gaussian 09 package. A solution of (8×10(-5) M) PENDA in THF, dioxane, CH3CN and CHCl3 gives laser emission when pumped by a nitrogen laser pulse (λex=337.1 nm) of 800 ps duration and 1.48 mJ pulse energy. PENDA dye displays fluorescence quenching by colloidal silver nanoparticles (Ag NPs) in ethanol. The fluorescence data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching mechanism.

Bifurcated hydrogen bonding mediated planar 9,10-anthraquinone dyes: synthesis, structure and properties

By acylation of mono- and diamino-9,10-anthraquinones with o-alkoxylbenzene carbonyl chloride or o-alkoxylnaphthalene carbonyl chloride, a series of planar 9,10-anthraquinone dyes were designed and synthesized.

1-Dimethyl-amino-9,10-anthraquinone

In the crystal structure of the title compound, C₁₆H₁₃NO₂, adjacent mol­ecules are linked through C—H⋯π and π–π [centroid–centroid distances = 3.844 (2) Å] contacts. The anthracene ring system and dimethyl­amino group are oriented at a dihedral angle of 38.4 (1)°. In the crystal, the mean planes of adjacent anthracene units are inclined at angles of 59.3 (1), 75.7 (1) and 76.0 (1)°.

Fluorescence enhancement of 1-napthol-5-sulfonate by forming inclusion complex with beta-cyclodextrin in aqueous solution

Fluorescence enhancement of 1-naphthol-5-sulfonate (1N5S) upon inclusion in beta-cyclodextrin is studied by spectrophotometry and spectrofluorimetery techniques. The spectral shifts were only observed in the emission spectra in different solvents and were found to be directly correlated to the solvent's hydrogen-bond donor strength (alpha). Spectral changes in the absorption spectra upon the addition of beta-cyclodextrin to 1N5S in aqueous medium were too small to allow for the determination of the binding constant. On the other hand; fluorescence measurements show that the emission of both the anionic and neutral forms of 1N5S increase upon the addition of beta-cyclodextrin with an increase in the quantum yield by about 60%. Fluorescence measurements show 1:1 inclusion of 1N5S in the beta-cyclodextrin cavity with an association constant of 88+/-10M(-1). (1)H NMR studies are used to confirm the inclusion and to provide information on the geometry of 1N5S inside the cavity of beta-cyclodextrin.

Estimation of first excited singlet-state dipole moments of aminoanthraquinones by solvatochromic method

The ground state (micro(g)) and the excited state (micro(e)) dipole moments of three substituted anthraquinones, namely 1-aminoanthracene-9,10-dione (AAQ), 1-(methylamino)anthracence-9,10-dione (MAQ) and 1,5-diaminoanthracene-9,10-dione (DAQ) were estimated in various solvents. The dipole moments (micro(g) and micro(e)) were estimated from Lippert, Bakhshiev, Kawski-Chamma-Viallet, McRae and Suppan equations by using the variation of Stokes shift with the solvent dielectric constant and refractive index. The excited state dipole moments were also calculated by using the variation of Stokes shift with microscopic solvent polarity parameter (Epsilon(T)(N)). It was observed that dipole moment values of excited states (micro(e)) were higher than corresponding ground state values (micro(g)), indicating a substantial redistribution of the pi-electron densities in a more polar excited state for all the molecules investigated.

Photoreduction of 2-methyl-1-nitro-9,10-anthraquinone in the presence of 1-phenylethanol

The photoreactions of 1-nitro-9,10-anthraquinone (N1) and 2-methyl-1-nitro-9,10-anthraquinone (N2) were studied in benzene and acetonitrile in the presence of 1-phenylethanol. For N2, a short-lived 10 ns transient observed upon flash photolysis is attributed to a triplet state, which can be intercepted by 1-phenylethanol to form a monohydro radical of N2 and a spectroscopically not detectable donor-derived radical. The decay of radicals yields the corresponding nitroso compound and eventually 1-amino-2-methyl-9,10-anthraquinone (A2) as photoproduct. The final reduction step requires participation of the anthraquinone carbonyl groups. The yield of radicals and the quantum yield (Phi(NH(2))) of conversion to A2 are small in inert solvents and increase with the donor concentration, approaching Phi(NH(2)) = 0.2. No triplet state was observed in the flash photolysis of N1, but a N1-derived radical and 1-amino-9,10-anthraquinone (A1) as final products were found. Various mechanistic aspects of complete photoreduction of nitroarenes to aminoarenes are discussed.

Photophysical properties of quinones and their interaction with the photosynthetic reaction centre

Photophysical properties of tetramethyl-1,4-benzoquinone (TMBQ) and 2,6-dimethoxy-1,4-benzoquinone (DMOBQ) in solution and their interactions with the photosynthetic reaction centre (RC) isolated from the photosynthetic bacterium Rhodobacter sphaeroides have been investigated in this work. For these two benzoquinone derivatives an efficient ISC process which leads to the population of the lowest triplet state of the molecules upon direct excitation was observed. The presence of RC does not alter the properties of the triplet state of DMOBQ suggesting that interactions are negligible; on the other side RC efficiently quenched the T1 state of TMBQ. The behavior is rationalized in terms of redox potentials of quinones and kinetic characteristics of their transients.