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1.
Effect of the π Bridge and Acceptor on Intramolecular Charge Transfer in Push–Pull Cationic Chromophores: An Ultrafast Spectroscopic and TD‐DFT Computational Study
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Dr. Benedetta Carlotti Dr. Enrico Benassi Prof. Vincenzo Barone Dr. Giuseppe Consiglio Prof. Fausto Elisei Dr. Alessandra Mazzoli Prof. Anna Spalletti 《Chemphyschem》2015,16(7):1440-1450
Three (donor–π–acceptor)+ systems with a methyl pyridinium or quinolinium as the electron‐deficient group, a dimethyl amino as the electron‐donor group, and an ethylene or butadiene group as the spacer have been investigated in a joint spectroscopic and TD‐DFT computational study. A negative solvatochromism has been revealed in the absorption spectra, which implies a solution color change, and interpreted by considering the variation in the permanent dipole moment modulus and orientation upon photoexcitation. The fluorescence efficiency decreases upon increasing solvent polarity, in agreement with the excited‐state optimized geometries (planar in low‐polarity media and twisted in high‐polarity media). Femtosecond transient absorption has revealed the occurrence of a fast photoinduced intramolecular charge transfer (ICT) and the molecular factors that determine an efficient ICT. Considering the crucial role of the ICT in tuning the nonlinear optical (NLO) properties, these compounds can be considered promising NLO materials. 相似文献
2.
Excited‐State Proton Transfer and Intramolecular Charge Transfer in 1,3‐Diketone Molecules
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Dr. Marika Savarese Dr. Éric Brémond Prof. Dr. Carlo Adamo Prof. Dr. Nadia Rega Dr. Ilaria Ciofini 《Chemphyschem》2016,17(10):1530-1538
The photophysical signature of the tautomeric species of the asymmetric (N,N‐dimethylanilino)‐1,3‐diketone molecule are investigated using approaches rooted in density functional theory (DFT) and time‐dependent DFT (TD‐DFT). In particular, since this molecule, in the excited state, can undergo proton transfer reactions coupled to intramolecular charge transfer events, the different radiative and nonradiative channels are investigated by making use of different density‐based indexes. The use of these tools, together with the analysis of both singlet and triplet potential energy surfaces, provide new insights into excited‐state reactivity allowing one to rationalize the experimental findings including different behavior of the molecule as a function of solvent polarity. 相似文献
3.
Dr. Aleksander Rebane Geoffrey Wicks Dr. Mikhail Drobizhev Dr. Thomas Cooper Aleksander Trummal Dr. Merle Uudsemaa 《Angewandte Chemie (International ed. in English)》2015,54(26):7582-7586
We present a new approach for determining the strength of the dipolar solute‐induced reaction field, along with the ground‐ and excited‐state electrostatic dipole moments and polarizability of a solvated chromophore, using exclusively one‐photon and two‐photon absorption measurements. We verify the approach on two benchmark chromophores N,N‐dimethyl‐6‐propionyl‐2‐naphthylamine (prodan) and coumarin 153 (C153) in a series of toluene/dimethyl sulfoxide (DMSO) mixtures and find that the experimental values show good quantitative agreement with literature and our quantum‐chemical calculations. Our results indicate that the reaction field varies in a surprisingly broad range, 0–107 V cm?1, and that at close proximity, on the order of the chromophore radius, the effective dielectric constant of the solute–solvent system displays a unique functional dependence on the bulk dielectric constant, offering new insight into the close‐range molecular interaction. 相似文献
4.
5.
《Chemphyschem》2003,4(3):249-259
Two‐photon absorption cross sections δ and solvatochromic properties were determined for a series of quadrupolar and dipolar compounds by using femtosecond excitation in the spectral range between 710 and 960 nm. The compounds investigated were distyrylbenzenes and polyenes bearing appropriate π or σ acceptors. The δ values for the centrosymmetric compounds trans,trans‐1,4‐bis[2‐(2′,5′‐dihexyloxy)phenylethenyl]‐2,3,5,6‐tetrafluorobenzene ( 6 ), trans,trans‐1,4‐bis[2‐(4′‐dibutylamino)phenylethenyl]‐2,3,5,6‐tetrafluorobenzene ( 2 ), trans,trans‐1,4‐bis[2‐(4′dimethylamino)phenylbutadienyl]‐2,3,5,6‐tetrafluorobenzene ( 7 ), trans,trans‐1,4‐bis[2‐(4′‐dimethylamino)phenylethenyl]‐2,5‐dicyanobenzene ( 4 ) and trans,trans‐1,4‐bis[2‐(4′‐dimethylamino)phenylethenyl]‐2‐propylsulfonyl‐5‐(2‐ethylhexyl)sulfonylbenzene ( 3 ) are on the order of 600, 1400, 1700, 3000, and 4100×10?50 cm4 s photon?1, respectively. The corresponding dipolar compounds trans‐2‐(4′‐dimethylaminophenyl)ethenyl‐2,3,4,5,6‐pentafluorobenzene ( 8 ), trans‐4‐(4′‐dimethylaminophenyl)butadienyl‐2,3,4,5,6‐pentafluorobenzene ( 9 ), trans‐6‐(4′‐dimethylaminophenyl)hexatrienyl‐2,3,4,5,6‐pentafluorobenzene ( 10 ) were additionally investigated. All centrosymmtric compounds are good fluorescent materials, while the dipolar chromophores 8 – 10 exhibit low fluorescence quantum yields. Solvatochromism was also observed for the fluorophores 2 – 10 as a result of intramolecular charge transfer (ICT). Furthermore, a reasonable correlation was obtained between measured and calculated δ. Quantum chemical calculations were performed by using the INDO Hamiltonian with a MRDCI scheme. The results show that the sum over states (SOS) expression for the second hyperpolarizability γ is appropriate to describe the mechanism of two‐photon absorption. Mechanistic investigations of quadrupolar compounds showed that the energy of the two‐photon excited state is higher than S1. 相似文献
6.
Excited State Intramolecular Proton Transfer in Ethynyl‐Extended Regioisomers of 2‐(2′‐Hydroxyphenyl)benzothiazole: Effects of the Position and Electronic Nature of Substituent Groups
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Dr. Qin Wang Dr. Longfei Xu Dr. Yahui Niu Dr. Yuxiu Wang Dr. Mao‐Sen Yuan Dr. Yanrong Zhang 《化学:亚洲杂志》2016,11(23):3454-3464
Although the organic dyes based on excited state intramolecular proton transfer (ESIPT) mechanism have attracted significant attention, the structure‐property relationship of ESIPT dyes needs to be further exploited. In this paper, three series of ethynyl‐extended regioisomers of 2‐(2′‐hydroxyphenyl)benzothiazole (HBT), at the 3′‐, 4′‐ and 6‐positions, respectively, have been synthesized. Changes in the absorption and emission spectra were correlated with the position and electronic nature of the substituent groups. Although 4′‐ and 6‐substituted HBT derivatives exhibited absorption bands at longer wavelengths, the keto‐emission of 3′‐substituted HBT derivatives was found at a substantially longer wavelength. The gradual red‐shifted fluorescence emission was found for 3′‐substituted HBT derivatives where the electron‐donating nature of substituent group increased, which was opposite to what was observed for 4′‐ and 6‐substituted HBT derivatives. The results derived from the theoretical calculations were in conformity with the experimental observations. Our study could potentially provide experimental and theoretical basis for designing novel ESIPT dyes that possess unique fluorescent properties. 相似文献
7.
Dr. Simon E. Greenough Michael D. Horbury Dr. Nichola A. Smith Prof. Dr. Peter J. Sadler Prof. Martin J. Paterson Dr. Vasilios G. Stavros 《Chemphyschem》2016,17(2):221-224
We present a new approach to investigate how the photodynamics of an octahedral ruthenium(II) complex activated through two‐photon absorption (TPA) differ from the equivalent complex activated through one‐photon absorption (OPA). We photoactivated a RuII polypyridyl complex containing bioactive monodentate ligands in the photodynamic therapy window (620–1000 nm) by using TPA and used transient UV/Vis absorption spectroscopy to elucidate its reaction pathways. Density functional calculations allowed us to identify the nature of the initially populated states and kinetic analysis recovers a photoactivation lifetime of approximately 100 ps. The dynamics displayed following TPA or OPA are identical, showing that TPA prodrug design may use knowledge gathered from the more numerous and easily conducted OPA studies. 相似文献
8.
《Angewandte Chemie (International ed. in English)》2017,56(1):254-259
The emission process of the o ‐carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene‐o ‐carborane dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation‐ and crystallization‐induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual‐emissions assigned to both locally excited (LE) and ICT states in solution. From the mechanistic studies and computer calculations, it was indicated that the emission band from the ICT should be attributable to the TICT emission. Surprisingly, even in the crystalline state, the TICT emission was observed. It was proposed from that the compact sphere shape of o ‐carborane would allow for rotation even in the condensed state. 相似文献
9.
Sensitised LnIII Emission and Excited‐State Dynamics of Cofacial ‘Pacman’ Porphyrin Terpyridine Complexes
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Jane Y. Liew Joshua J. Brown Dr. Evan G. Moore Dr. Matthias Schwalbe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16178-16186
An asymmetric ‘Pacman’ metalloligand, [Zn(PXT)], which features a cofacial ZnII–porphyrin unit (P) covalently attached to a terpyridine (T) chelating group via a rigid xanthene (X) moiety has been prepared, and its interactions with several different trivalent LnIII cations (NdIII, GdIII, YbIII and LuIII) have been examined. The formation of 1:1 metal–ligand complexes was monitored by 1H NMR spectroscopy and corroborated by HRMS data. Solution‐stability constants were determined by UV/Vis titration, and the resulting complexes with NdIII or YbIII demonstrated sensitised emission in the NIR region due to energy transfer from the ZnII–porphyrin donor to LnIII acceptor. The energy transfer was investigated by transient absorption techniques, which provided insight into the kinetics and efficiency of the antenna effect. 相似文献
10.
Long emission wavelengths, high fluorescence quantum yields (FQYs), and large Stokes shifts are highly desirable features for fluorescent probes in biological imaging. However, the current development of many fluorescent probes remains largely trial‐and‐error and lacks efficiency. Moreover, to achieve far‐red/near‐infrared emission, a significant extension in the ‐conjugation is usually adopted but accompanied by other drawbacks such as fluorescence loss. In this review, we discuss an effective red‐shifting strategy built upon the green fluorescent protein chromophore, which enables a synergistic tuning of both the electronic ground and excited states. This approach could shorten the path toward redder emission in comparison to the conventional intramolecular charge transfer (ICT) strategy. We envision that this spectroscopy and computation‐aided strategy may advance the noncanonical fluorescent protein design and be generalized to various fluorophore scaffolds for redder emission while preserving other superior properties such as high FQYs. 相似文献
11.
Conner A. Hoelzel Hang Hu Charles H. Wolstenholme Basel A. Karim Kyle T. Munson Kwan Ho Jung Han Zhang Yu Liu Hemant P. Yennawar John B. Asbury Xiaosong Li Xin Zhang 《Angewandte Chemie (International ed. in English)》2020,59(12):4785-4792
While organic donor‐acceptor (D‐A) molecules are widely employed in multiple areas, the application of more D‐A molecules could be limited because of an inherent polarity sensitivity that inhibits photochemical processes. Presented here is a facile chemical modification to attenuate solvent‐dependent mechanisms of excited‐state quenching through addition of a β‐carbonyl‐based polar substituent. The results reveal a mechanism wherein the β‐carbonyl substituent creates a structural buffer between the donor and the surrounding solvent. Through computational and experimental analyses, it is demonstrated that the β‐carbonyl simultaneously attenuates two distinct solvent‐dependent quenching mechanisms. Using the β‐carbonyl substituent, improvements in the photophysical properties of commonly used D‐A fluorophores and their enhanced performance in biological imaging are shown. 相似文献
12.
Indolizino[5,6‐b]quinoxaline Derivatives: Intramolecular Charge Transfer Characters and NIR Fluorescence
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Mitsuru Kojima Dr. Hironobu Hayashi Dr. Tatsuya Aotake Dr. Shinya Ikeda Dr. Mitsuharu Suzuki Prof. Dr. Naoki Aratani Dr. Daiki Kuzuhara Prof. Dr. Hiroko Yamada 《化学:亚洲杂志》2015,10(11):2337-2341
Indolizino[5,6‐b]quinoxaline derivatives ( 1 a and 1 b ) with a push–pull structure were prepared to show intramolecular charge‐transfer properties. Compounds 1 a and 1 b are strongly fluorescent in aprotic solvents while symmetrical derivatives ( 2 a and 2 b ) were non‐fluorescent. The π‐expanded α–α linked dimer ( 10 ) of indolizino[5,6‐b]quinoxaline 1 b was serendipitously obtained to show NIR absorption over 800 nm and the fluorescence edge reached to 1400 nm. 相似文献
13.
Pi‐Tai Chou 《中国化学会会志》2001,48(4):651-682
Contemporary progress regarding guest/host types of excited‐state double proton transfer has been reviewed, among which are the biprotonic transfer within doubly H‐bonded host/guest complexes, the transfer through a solvent bridge relay, the intramolecular double proton transfer and solvation dynamics coupled proton transfer. Of particular emphases are the photophysical and photochemical properties of excited‐state double proton transfer (ESDPT) in 7‐azaindole and its corresponding analogues. From the chemical aspect, two types of ESDPT reaction, namely the catalytic and non‐catalytic types of ESDPT, have been classified and reviewed separately. For the case of static host/guest hydrogen‐bonded complexes both hydrogen‐bonding strength and configuration (i.e. geometry) play key roles in accounting for the reaction dynamics. In addition to the dynamical concern, excited‐state thermodynamics are of importance to fine‐tune the proton transfer reaction in the non‐catalytic host/guest type of ESDPT. The mechanisms of protic solvent assisted ESDPT, depending on host molecules and proton‐transfer models, have been reviewed where the plausible resolution is deduced. Particular attention has been given to the excited‐state proton transfer dynamics in pure water, aiming at its future perspective in biological applications. Finally, the differentiation in mechanism between solvent diffusive reorganization and solvent relaxation to affect the host/guest ESPT dynamics is made and discussed in de tail. 相似文献
14.
Dominik B. Bucher Alexander Schlueter Prof. Dr. Thomas Carell Prof. Dr. Wolfgang Zinth 《Angewandte Chemie (International ed. in English)》2014,53(42):11366-11369
Excited‐state dynamics are essential to understanding the formation of DNA lesions induced by UV light. By using femtosecond IR spectroscopy, it was possible to determine the lifetimes of the excited states of all four bases in the double‐stranded environment of natural DNA. After UV excitation of the DNA duplex, we detected a concerted decay of base pairs connected by Watson–Crick hydrogen bonds. A comparison of single‐ and double‐stranded DNA showed that the reactive charge‐transfer states formed in the single strands are suppressed by base pairing in the duplex. The strong influence of the Watson–Crick hydrogen bonds indicates that proton transfer opens an efficient decay path in the duplex that prohibits the formation or reduces the lifetime of reactive charge‐transfer states. 相似文献
15.
Back Cover: Indolizino[5,6‐b]quinoxaline Derivatives: Intramolecular Charge Transfer Characters and NIR Fluorescence (Chem. Asian J. 11/2015)
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Mitsuru Kojima Dr. Hironobu Hayashi Dr. Tatsuya Aotake Dr. Shinya Ikeda Dr. Mitsuharu Suzuki Prof. Dr. Naoki Aratani Dr. Daiki Kuzuhara Prof. Dr. Hiroko Yamada 《化学:亚洲杂志》2015,10(11):2540-2540
16.
Excited‐State Intramolecular Proton Transfer: Photoswitching in Salicylidene Methylamine Derivatives
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Joanna Jankowska Dr. Michał F. Rode Prof. Joanna Sadlej Prof. Andrzej L. Sobolewski 《Chemphyschem》2014,15(8):1643-1652
The effect of chemical substitutions on the photophysical properties of the salicylidene methylamine molecule (SMA) (J. Jankowska, M. F. Rode, J. Sadlej, A. L. Sobolewski, ChemPhysChem, 2012 , 13, 4287–4294) is studied with the aid of ab initio electronic structure methods. It is shown that combining π‐electron‐donating and π‐electron‐withdrawing substituents results in an electron‐density push‐and‐pull effect on the energetic landscape of the ground and the lowest excited ππ* and nπ* singlet states of the system. The presented search for the most appropriate SMA derivatives with respect to their photoswitching functionality offers an efficient prescreening tool for finding chemical structures before real synthetic realization. 相似文献
17.
Ultrafast Twisting Dynamics of Thioflavin‐T: Spectroscopy of the Twisted Intramolecular Charge‐Transfer State
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Understanding the excited‐state properties of thioflavin‐T (ThT) has been of immense importance, because of its efficient amyloid‐sensing ability related to neurodegenerative disorders. The excited‐state dynamics of ThT is studied by using sub‐pico‐ and nanosecond time‐resolved transient absorption techniques as well as density functional theory (DFT)/time‐dependent DFT calculations. Barrierless twisting around the central C?C bond between two aromatic moieties is the dominant process that contributes to the ultrafast dynamics of the S1 state. The spectroscopic properties of the intramolecular charge‐transfer state are characterized for the first time. The energetics of the S0 and S1 states has also been correlated with the experimentally observed spectroscopic parameters and structural dynamics. A longer‐lived transient state populated with a very low yield has been characterized as the triplet state. 相似文献
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Excited‐State Charge Separation in the Photochemical Mechanism of the Light‐Driven Enzyme Protochlorophyllide Oxidoreductase
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Dr. Derren J. Heyes Dr. Samantha J. O. Hardman Tobias M. Hedison Robin Hoeven Dr. Greg M. Greetham Prof. Michael Towrie Prof. Nigel S. Scrutton 《Angewandte Chemie (International ed. in English)》2015,54(5):1512-1515
The unique light‐driven enzyme protochlorophyllide oxidoreductase (POR) is an important model system for understanding how light energy can be harnessed to power enzyme reactions. The ultrafast photochemical processes, essential for capturing the excitation energy to drive the subsequent hydride‐ and proton‐transfer chemistry, have so far proven difficult to detect. We have used a combination of time‐resolved visible and IR spectroscopy, providing complete temporal resolution over the picosecond–microsecond time range, to propose a new mechanism for the photochemistry. Excited‐state interactions between active site residues and a carboxyl group on the Pchlide molecule result in a polarized and highly reactive double bond. This so‐called “reactive” intramolecular charge‐transfer state creates an electron‐deficient site across the double bond to trigger the subsequent nucleophilic attack of NADPH, by the negatively charged hydride from nicotinamide adenine dinucleotide phosphate. This work provides the crucial, missing link between excited‐state processes and chemistry in POR. Moreover, it provides important insight into how light energy can be harnessed to drive enzyme catalysis with implications for the design of light‐activated chemical and biological catalysts. 相似文献