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A cyanostilbene-based molecule with aggregation-induced emission properties: amplified spontaneous emission, protonation effect and electroluminescence
摘要： A terpyridine-substituted cyanostilbene derivative (Z)-2-(4′-([2,2′:6′,2″-terpyridin]-4′-yl)-[1,1′-biphenyl]-4-yl)-3-phenylacrylonitrile (CNSTPy) was synthesized and characterized. The compound exhibits remarkable aggregation-induced emission phenomenon and its single crystal shows a blue emission with fluorescent efficiency as high as 45%. Based on its aggregation state behavior, multiple applications towards exploring its lasing, fluorescence switching and electroluminescence properties were realized. Amplified spontaneous emission (ASE) was observed from the crystal and verified by the variable pump strip method, with a threshold value of ~1.5 mJ cm?2. The protonation/deprotonation processes accompanied by the formation of different molecular aggregation structure result in the distinct blue and yellow emissions. Additionally, the molecule also shows a moderate electroluminescence performance.
关键词： amplified spontaneous emission,cyanostilbene,aggregation-induced emission,protonation effect
更新于2025-09-23 15:23:52
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Improvement of the ON/OFF Switching Performance of a pH-Activatable Porphyrin Derivative by the Introduction of Phosphorus(V)
摘要： An activatable photosensitizer for singlet oxygen is of significance due to its potential applications for high tumor-specific photodynamic therapy and diagnosis. In this study, a pH-activatable system that enables the specific photosensitization of singlet oxygen at a low pH was developed based on the complexation of a porphyrin–aniline conjugate with phosphorus(V). As a result of complexation with phosphorus, the water solubility of the porphyrin–aniline conjugate was improved by 100 times. Furthermore, this complexation strongly suppressed the singlet-oxygen-generating activity of the porphyrin photosensitizer under basic conditions, and the quantum yield of the singlet oxygen photosensitization markedly increased under acidic conditions. Based on these improvements, an extremely high ON/OFF switching ratio of the quantum yield was obtained (>400 times).
关键词： pH activatable photosensitizer,ON/OFF switching,singlet oxygen,aniline,phosphorous porphyrin,protonation,fluorescence,acid
更新于2025-09-23 15:23:52
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Revisited Dual Luminescence of 2,2′-Dipyridylamine Hydrochloride in Solution and Physical Processes behind It
摘要： Reaction of 2,2’-dipyridylamine (dpa) with hydrochloric acid results in formation of dpa hydrochloride (dpa?HCl), leading to substantial changes in its luminescent properties. Luminescence of dpa?HCl in solution has been previously interpreted as aggregation-induced phenomenon. In this work, the emission properties of dpa?HCl in solution were revisited, focusing on the impact of methanol and chloroform solvents. Luminescence, absorption, and 1H NMR spectroscopy were used to study physical state of the solute molecules and photophysical properties associated with them. The results clearly indicate that the concentration and solvent dependencies of luminescence are due to equilibrium between protonated dpaH + and neutral dpa forms, rather than aggregation in solution. In chloroform, strong emission with λem ? 430 nm is associated with the cationic dpaH + form. Polar and hydrogen bonding methanol not only facilitates dissociation of dpaH + cation, but also seems to quench its luminescence through pyridinium hydrogen bond, and the residual weak emission at λem ? 360 nm is associated with the neutral dpa form. The obtained results can be applied in design of new dpa based materials with desirable luminescent properties in both solution and solid state.
关键词： 2,2’-dipyridylamine,protonation,hydrogen bond,absorption,luminescence
更新于2025-09-23 15:21:21
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Applications of Molecular Spectroscopy to Current Research in the Chemical and Biological Sciences || Geometric and Electronic Properties of Porphyrin and its Derivatives
摘要： In this chapter, we discuss protonation and substitution effects on the absorption spectra of porphyrin molecules based on density functional theory (DFT) and time-dependent DFT calculations. The results of the calculations are compared with experimental data. The calculations show that protonation of core nitrogen atoms of porphyrin and meso-substituted porphyrins produces a substantial shift in Soret and Q-absorption bands, relative to their positions in corresponding nonprotonated and nonsubstituted chromophores. A relaxed potential energy surface (RPES) scan has been utilized to calculate ground and excited state potential energy surface (PES) curves as functions of the rotation of one of the meso-substituted sulfonatophenyl groups about dihedral angles θ (corresponding to Cα─Cm─C?─C) ranging from 40 to 130°, using 10° increments. The ground state RPES curve indicates that when the molecule transitions from the lowest ground state to a local state, the calculated highest potential energy barrier at the dihedral angle of 90° is only 177 cm?1. This finding suggests that the meso-sulfonatophenyl substitution groups are able to rotate around Cm─C? bond at room temperature because the thermal energy (kBT) at 298 K is 207.2 cm?1. Furthermore, the calculations show that the geometric structure of the porphyrin is strongly dependent on protonation and the nature of the meso-substituted functional groups.
关键词： DFT calculation,protonation,PES,porphyrins,absorption
更新于2025-09-23 15:21:21
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Isolation and characterization of a monoprotonated hydroporphyrin
摘要： A simple protocol for the controlled preparation of mono- and diprotonated hydroporphyrins (chlorins) is presented. The chlorins carried 10-aryl groups with electron-neutral (phenyl), electron-donating (p-OMe-C6H4) or electron-withdrawing (pentafluorophenyl) substituents. The protonation reactions were readily followed by UV-Vis absorption spectroscopy, enabling the determination of the first (4.8–5.3) and second pKa’s (1.7–0.5). Both mono- and diprotonated species were fully characterized by 1H NMR spectroscopy, which, in combination with theoretical studies, showed that these macrocycles were significantly distorted in solution. A 10-phenyl-substituted monoprotonated chlorin was characterized by X-ray crystallography. This is the first structurally characterized hydroporphyrin monocation, and the first crystal structure of a sterically unencumbered singly protonated tetrapyrrole. The photostabilities of the mono- and diprotonated 10-phenylchlorins were measured upon irradiation into their Soret bands; protonation yielded increased photostabilities.
关键词： protonation,fluorescence,absorption,chlorin,tetrapyrrole
更新于2025-09-23 15:21:01
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A Strongly Fluorescent Molecular Material Responsive to Physical/Chemical Stimuli and their Coupled Impact
摘要： Molecular materials with weak but extended and pliable supramolecular interactions are versatile candidates for eliciting stimuli-sensitive optical responses. A novel diaminodicyanoquinodimethane (DADQ) molecule, 7,7-bis(2-(2-pyridyl)ethylamino)-8,8-dicyanoquinodimethane (BPEDQ), has been synthesized and structurally characterized; it exhibits enhanced fluorescence emission in the aggregated and solid states, characteristic of DADQs. The pyridine moieties in the molecule, in addition to the amino and cyano groups of the strongly dipolar fluorophore moiety, induce extensive H-bonding interactions which can impart structural integrity to the solid material; this enables reversible crystalline-amorphous transformations triggered by mechanical grinding and solvent fuming. The concomitant fluorescence color and intensity switching are prominent and reversible. Protonation-deprotonation events induced by acidic and basic vapors also produce stark fluorescence response variations; the chemical stimuli also lead to amorphization of the solid. The full cycle of chemical and physical stimuli, and the consequence of their individual and coupled impact on the fluorescence emission, are illustrated using a BPEDQ-doped polymer thin film.
关键词： amorphous-crystalline transformation,stimuli-responsive,molecular crystal,protonation,fluorescence
更新于2025-09-11 14:15:04
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Mechanistic Insight into the Carbon Dots: Protonation induced Photoluminescence
摘要： Although several theories have been proposed, the mechanism of complex photoluminescence in carbon dots (CNDs) is a central quest till date. This report presents pH dependent steady state and time resolved spectroscopy study which identifies a possible origin of the complex photoluminescence in CNDs. The multiple emissive species created by the excited state protonation-deprotonation reaction at certain pH gives rise to inhomogeneous broadening and consequently excitation dependent multicolour emission. The origin of the excited state dynamics is attributed to the significant change of the proton dissociation between ground and excited state. We present a new model on protonation dynamics and show how it affects the emissive states in CNDs.
关键词： time resolved fluorescence,origin of photoluminescence,pH dependence,Carbon dots,Excited state protonation
更新于2025-09-10 09:29:36
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Synthesis and properties of merocyanine dyes derived from N-aryl-substituted pyridinium salts and cyanoacetic acids
摘要： A series of merocyanine dyes were synthesized by two-component condensation of N-aryl-4-picolinium salts and cyanoacetic acid derivatives. Physicochemical properties of the synthesized dyes were studied.
关键词： protonation,4-picolinium salts,merocyanine dyes,spectral properties,heterocycles
更新于2025-09-10 09:29:36
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Thermally Induced Protonation of Conducting Polyaniline Film by Dibutyl Phosphite Conversion to Phosphate
摘要： The blue thin polyaniline base film changes its color to green after immersion of the film into dibutyl phosphonate. The green color of the film converts to a greenish-blue after heating up to 200 °C in air which is characteristic for protonated conducting form of polyaniline. This is in the contrast to the “standard” polyaniline hydrochloride which is transformed into a crosslinked polyaniline base under such conditions. To explain this unexpected observation, the interaction of polyaniline base with dibutyl phosphonate at ambient conditions and after heating to 200 oC was studied using UV–visible, FTIR and Raman spectroscopies. Based on these studies, we propose that dibutyl phosphite tautomeric form of dibutyl phosphonate which interacts with polyaniline base at 20 °C converts to the oxidized form, dibutyl phosphate, at 200 °C and subsequently protonates the film. Quantum-chemical modelling of the interaction of polyaniline base with dibutyl phosphite and dibutyl phosphate supports this explanation.
关键词： Thermally Induced Protonation,Quantum Chemistry,Conducting Polyaniline Film,Dibutyl Phosphite,Molecular Structure,Phosphate Conversion,Spectroscopy
更新于2025-09-10 09:29:36
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Remarkable responsive behaviors of iso-aminobenzopyranoxanthenes: protonation effect, photochromism and piezochromism
摘要： The iso-cis/trans-aminobenzopyranoxanthenes (iso-cis/trans-ABPXs), as one of popular leuco dyes, were investigated in solution or crystal phase. The introduction of benzo-pentacyclic-ester group in iso-cis/trans-ABPXs leads to remarkable multi-stimuli responsive behaviors, including protonation effect, photochromism and piezochromism with notable color changes. The iso-cis/trans-ABPXs show different in the responsive sensitivity and the iso-cis-ABPX is highly sensitive to environmental stimuli relative to the trans-form, which can be explained by their different C-H?O interaction and/or C-O bond length. Interestingly, as the ultraviolet light irradiation time increasing, the iso-cis/trans-ABPXs solution gradually becomes transparent and orange precipitates are achieved, which is identified as iso-ABPXs ±. Multi-stimuli responsive behaviors on the iso-cis/trans-ABPXs provide a comprehensive insight into the chromogenic mechanisms of this type of materials, suggesting that they may be potential candidate materials for sensors and indicators.
关键词： Protonation effect,Piezochromism,Photochromism,Spirolactone ring,Tautomerizm
更新于2025-09-10 09:29:36