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ABSTRACT: A two-photon fluorescent probe has become a critical tool in biology and medicine owing to its capability of imaging intact tissue for a long period of time, such as in two-photon fluorescence microscopy (TPM). In this context, a series of Salen-based zinc-ion bioimaging reagents that were designed based on an intramolecular charge-transfer mechanism were studied through the quantum-chemical method. The increase of one-photon absorption and fluorescence emission wavelength and the reduction of the oscillator strength upon coordination with a zinc ion reveal that they are fluorescent bioimaging reagents used for ratiometric detection. When the Salen ligand is incorporated with Zn(2+), the value of the two-photon absorption (TPA) cross-section (δmax) will decrease, and most of the ligands and complexes exhibit a TPA peak in the near-infrared spectral region. That is, a substituent at the end of the ligand can influence the luminescence property, besides increasing solubility. In addition, the effect of an end-substituted position on the TPA property was considered, such as ortho and meta substitution. The detailed investigations will provide a theoretical basis to synthesize zinc-ion-responsive two-photon fluorescent bioimaging reagents as powerful tools for TPM and biological detection in vivo.
Inorganic Chemistry 05/2013; · 4.60 Impact Factor
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ABSTRACT: The dynamics simulation and quantum chemical calculation are employed to investigate spectrum properties of deprotonation process of coelenteramide and two final states neutral state and phenolate anion. According to the calculation results, theoretical evidence supporting the luminescence mechanism hypothesis is proposed in a significant bioluminescence process. In vivo of marine bioluminescent organisms, if the protein motion provides the conditions for the deprotonation of coelenteramide in some protein molecules, the phenolate anion is completely deprotonated coelenteramide as an emitter in these protein molecules and emits fluorescence assigned to the lower energy peak. And another emitter which the condition of deprotonation does not meet, the fluorescence is produced by the neutral state of coelenteramide and assigned to the higher energy peak. The energy difference decreases gradually when the proton of coelenteramide gradually approaches to His22. For phenolate anion and neutral state, electronic cloud distributions between their each frontier molecular orbitals HOMO and LUMO have high overlapping volume. The molecular electrostatic potential indicates that for phenolate anion, the oxygen atom after deprotonation has greater electron density which is good for formation hydrogen bonds with amino acids in the environment. © 2013 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2013 The American Society of Photobiology.
Photochemistry and Photobiology 03/2013; · 2.41 Impact Factor
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ABSTRACT: The photophysical properties of a series of multifunctional compounds applied in organic light-emitting diode (OLED) materials
have been studied by quantum chemistry. These compounds have been integrated by an electron and hole transporting component
as well as an emitting component into the donor–π–acceptor (D–π–A) structures. To reveal the relationship between the structures
and properties of these multifunctional electroluminescent materials, the ground- and excited-state geometries were optimized
at the B3LYP/6-31G(d), HF/6-31G(d), and CIS/6-31G(d) levels, respectively. The ionization potentials and electron affinities
were computed. The mobilities of hole and electron in these compounds were studied computationally based on the Marcus electron
transfer theory. The maximum absorption and emission wavelengths of compounds 1–4 were calculated by time-dependent density functional theory method. As a result of these calculations, it was concluded that
the electron injections of compounds 2–6 are much easier than Mes2B[p-4,4′-biphenyl-NPh(1-naphthyl)] (BNPB) due to the introduction of the thiophene group, anthracene group, and N=N as a part
of the π-conjugated bridge, compounds 5 and 6 can act as electron transport and hole transport materials, respectively. Compounds 1 and 2 have higher electron mobility and light-emitting efficiency as compared to compounds 3 and 4. Compounds 3 and 4 have quite longer fluorescence lifetimes than compounds 1 and 2 due to the larger Stoke’s shifts.
KeywordsBifunctional and multifunctional OLEDs-Optical properties-Electronic structures
Theoretical Chemistry Accounts 05/2012; 126(5):361-369. · 2.16 Impact Factor
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ABSTRACT: AbstractAn extensive series of pyrazabole chromophores containing pseudo-conjugated systems have been theoretically constructed and
investigated on the one-photon absorption (OPA) and two-photon absorption (TPA) properties by using density functional theory
and Zerner’s intermediate neglect of differential overlap methods. The results indicated that all the pyrazabole chromophores
show strong OPA at around 400nm and intense TPA properties in the range of 500–600nm with TPA cross sections (δ
max) as large as 540–3,560 GM, which are excellent candidates for optical power limiting materials. It is noteworthy that the
δ
max values of the two constructed pyrazaboles, PA3 and PAF2, are 308.8GM at 772.0nm and 157.8 GM at 834.4nm, respectively, which may be particularly attractive as probes for two-photon
fluorescence imaging. The influence of incorporating electron acceptors in the central core, π-conjugated bridge and terminal
groups on OPA and TPA properties was analyzed in detail to derive structure–property relationships and to lay the guidelines
for both spectral tuning and amplification of molecular TPA in the target region. Meanwhile, the solvent effects on these
properties were taken into account within the PCM model. The solvent has a significant impact on the TPA properties for chromophore
PA3 and leads to the two-photon absorption spectra (λ
max
T
) red-shift and δ
max enhancing relative to those in gas phase. In addition, from the calculations of molecule AlA2, we can draw the conclusion that the compounds with the Al2N4 center behave similarly to pyrazabole chromophores in the linear optical and TPA properties and increase TPA cross sections
to some extent.
KeywordsPyrazabole chromophores–Two-photon absorption–Electronic structure–Density functional theory–Non-linear optical property
Theoretical Chemistry Accounts 04/2012; 130(1):37-50. · 2.16 Impact Factor
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ABSTRACT: The photophysical properties of organoboron quinolate derivatives can be modified readily by manipulating the coordination
environment around the central boron atom. This class of compounds applied in organic light-emitting diodes (OLEDs) materials
has been studied by quantum chemistry. To reveal the relationship between the structures and properties of these electroluminescent
materials, the ground- and excited-state geometries were optimized at the B3LYP/6-31G(d) and CIS/6-31G(d) levels, respectively.
The ionization potentials and electron affinities were computed. The mobilities of hole and electron in these compounds were
studied computationally based on the Marcus electron transfer theory. The maximum absorption and emission wavelengths of these
compounds were calculated using the time-dependent density functional theory method. The solvent effect on the absorption
and emission wavelengths of these compounds was also considered by a polarizable continuum model. These results show that
boron compounds which containing both the hydroxyquinoline/hydroxybenzoquinoline as ligand and O/S in position X follow the
rule, that is, the emission shifts to longer wavelength as covalent nature of the boron–ligand bonding is increased. Meanwhile,
the negative HOMO and IPs decrease but the negative LUMO and EAs increase by substitution of O with S in position X. It was
deduced that both the hole- and electron-injection abilities are improved by substituting S in place of O in position X. After
chemical modification in position R
2 with electron-donating properties of NH2 or 1,4-diethynyl-2,5-dihexyloxybenzene, introduced 1,4-diethynyl-2,5-dihexyloxybenzene improves both the hole- and electron-transfer
rate, which leads to better equilibrium property. It can be concluded that the better equilibrium property depends on the
conjugated length of side chain in position R
2. Moreover, exchanging the substituents R
1 and R
2 in BNO1a and BNO1’a can slightly change the hole-transfer rate by 0.04eV. According to these calculations, series BNO and BNS can be applied as electron transport and hole transport materials at the same time. Specially, series BNO2 and BNS have better performance than Mes2B[p-4,4’-biphenyl-NPh(1-naphthyl)] (BNPB) in both the hole- and electron-injection ability.
KeywordsElectronic structures–IP–EA–Optical properties
Theoretical Chemistry Accounts 04/2012; 129(1):63-71. · 2.16 Impact Factor
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ABSTRACT: The electronic structures, charge injection and transport, absorption and emission spectra, properties of two series of fluorene-based
oligomers {2-[2-{2-[5-(9H-Fluoren-3-yl)-thiophen-2-yl]-vinyl}-6-(2-thiophen-2-yl-vinyl)-pyran- 4-ylidene]-malononitrile}
n
(FTPM)
n
and {2-{2-{2-[5-(9H-Fluoren-2-yl)-2-hydroxy- 3-methoxy-phenyl]-vinyl}-6-[2-(2-hydroxy-3-methoxy-phenyl)-vinyl]-pyran-4- ylidene}-malononitrile}
n
(FOOPM)
n
(n=1–4) have been investigated by the density functional theory (DFT) approach. The ground-state geometries of (FTPM)4 and (FOOPM)4 optimized at B3LYP/6-31G(d) level exhibited zigzag arrangements. The energies of HOMO and LUMO, HOMO–LUMO energy gaps (ΔE
H–L
) of (FTPM)
n
and (FOOPM)
n
(n=∞) were obtained by linear extrapolation method. Moreover, the calculations of ionization potential (IP), electronic affinity
(EA), and reorganization energy (λ) were used to evaluate the charge injection and transport abilities. For (FTPM)4 and (FOOPM)4, the TDDFT calculations revealed that the absorption peaks can be characterized as π–π* transition and couple with the location
of electron density distribution changes in different repeat units. All the earlier theoretical investigations are intended
to establish the structure–property relationships, which can provide guidance to design the organic light-emitting diodes
(OLEDs) with high performance.
KeywordsOligomers-DFT-Organic light-emitting diodes (OLEDs)
Theoretical Chemistry Accounts 04/2012; 126(5):305-314. · 2.16 Impact Factor
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ABSTRACT: Ladder-type heterotetracenes possessing fully ring-fused structures are a promising class of optoelectronic materials in terms of the lack of any conformational disorder, intense emission and high carrier mobility. To uncover how dual bridging atoms tune their structural and optoelectronic properties, the heterotetracenes were systematically investigated by theoretical calculations from several aspects, such as (i) the geometrical structures of ground and excited states; (ii) the highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO); (iii) ionization potentials (IP), electron affinities (EA), hole extraction potentials (HEP), electron extraction potentials (EEP), internal reorganization energies (λ(int)) and transfer integrals (V); (iv) the absorption and emission spectra in vacuum and the dichloromethane (CH(2)Cl(2)) solvent, band gaps (E(g)), excitation energies at the lowest singlet (E(S1)) or triplet (E(T1)) states as well as radiative lifetimes (τ). The theoretical investigations may be useful for finding new leading materials and are likely to provide important information for improving their photoelectric performance.
Physical Chemistry Chemical Physics 11/2011; 13(43):19490-8. · 3.57 Impact Factor
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ABSTRACT: Using thiophene (which has a moderate resonance energy) as a spacer rather than benzene permits better π-electron delocalization and leads to a large nonlinear optical response. Thus, the nonlinear optical coefficients of a series of macrocyclic thiophene derivatives (C[3T_DA](n) with C(n) symmetry) were studied, and their electronic structures, UV-Vis spectra and static second-order nonlinear optical susceptibilities (β(0)) were computed. The calculated results showed that ΔE(H-L) increased and the UV-Vis spectrum redshifted as the number of C[3T_DA] units increased (one C[3T_DA] unit consists of trithiophene and diacetylene). The value of β(0) calculated by either the ZINDO-SOS or the FF method showed the same trend: the absolute value of β(0) increased as the number of units increased. The value of β(0) predicted by ZINDO-SOS was an order of magnitude larger than that predicted by the FF method. However, the results suggest that macrocyclic thiophene compounds potentially exhibit large static second-order nonlinear optical susceptibilities.
Journal of Molecular Modeling 05/2011; 18(1):393-404. · 1.80 Impact Factor
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ABSTRACT: The question whether the emitter of yellow-green firefly bioluminescence is the enol or keto-constrained form of oxyluciferin (OxyLH(2)) still has no definitive answer from experiment or theory. In this study, Arg220, His247, adenosine monophosphate (AMP), Water324, Phe249, Gly343, and Ser349, which make the dominant contributions to color tuning of the fluorescence, are selected to simulate the luciferase (Luc) environment and thus elucidate the origin of firefly bioluminescence. Their respective and compositive effects on OxyLH(2) are considered and the electronic absorption and emission spectra are investigated with B3LYP, B3PW91, and PBE1KCIS methods. Comparing the respective effects in the gas and aqueous phases revealed that the emission transition is prohibited in the gas phase but allowed in the aqueous phase. For the compositive effects, the optimized geometry shows that OxyLH(2) exists in the keto(-1) form when Arg220, His247, AMP, Water324, Phe249, Gly343, and Ser349 are all included in the model. Furthermore, the emission maximum wavelength of keto(-1)+Arg+His+AMP+H(2)O+Phe+Gly+Ser is close to the experimental value (560 nm). We conclude that the keto(-1) form of OxyLH(2) is a possible emitter which can produce yellow-green bioluminescence because of the compositive effects of Arg220, His247, AMP, Water324, Phe249, Gly343, and Ser349 in the luciferase environment. Moreover, AMP may be involved in enolization of the keto(-1) form of OxyLH(2). Water324 is indispensable with respect to the environmental factors around luciferin (LH(2)).
ChemPhysChem 07/2010; 11(10):2199-204. · 3.41 Impact Factor
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ABSTRACT: Is the resonance-based anionic keto form of oxyluciferin the chemical origin of multicolor bioluminescence? Can it modulate green into red luminescence? There is as yet no definitive answer from experiment or theory. The resonance-based anionic keto forms of oxyluciferin have been proposed as a cause of multicolor bioluminescence in the firefly. We model the possible structures by adding sodium or ammonium cations and investigating the ground- and excited-state geometries as well as the electronic absorption and emission spectra. A role for the resonance structures is obvious in the gas phase. The absorption and emission spectra of the two structures are quite different--one in the blue and another in the red. The differences in the spectra of the models are small in aqueous solution, with all the absorption and emission spectra in the yellow-green region. The resonance-based anionic keto form of oxyluciferin may be one origin of the red-shifted luminescence but is not the exclusive explanation for the variation from green (approximately 530 nm) to red (approximately 635 nm). We study the geometries, absorption, and emission spectra of the possible protonated compounds of keto(-1) in the excited states. A new emitter keto(-1)'-H is considered.
ChemPhysChem 11/2009; 11(1):251-9. · 3.41 Impact Factor
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Journal of Physical Organic Chemistry 07/2009; 22(11):1104 - 1113. · 1.96 Impact Factor
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ABSTRACT: The aim of this work is to provide an in-depth interpretation of the optical and electronic properties of a series of spirobifluorene derivatives. These materials show great potential for application in organic light-emitting diodes as efficient blue-light-emitting materials due to the tuning of the optical and electronic properties by the use of different electron donors (D) and electron acceptors (A). The geometric and electronic structures of the molecules in the ground state are studied with density functional theory (DFT) and ab initio HF, whereas the lowest singlet excited states are optimized by ab initio CIS. The energies of the lowest singlet excited states are calculated by employing time-dependent density functional theory (TD-DFT). The results show that the HOMOs, LUMOs, energy gaps, ionization potentials, electron affinities, reorganization energies, and exciton binding energies for these complexes are affected by different D and A moieties. Also, it has obtained that these blue-light-emitting materials have improved charge transport rate and charge transfer balance performance and can be used as efficient ambipolar-transporting materials in organic light-emitting diodes.
The Journal of Physical Chemistry A 07/2009; 113(27):7933-9. · 2.95 Impact Factor
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ABSTRACT: The coordination chemistry of polydentate chelating ligands that contain mixed pyridinephenol donor sets has been a sought-after target of study and is a possible extension to the chemistry of polypyridines. In this article, seven compounds, which are the four-coordinate boron complexes containing the mixed phenol-pyridyl group, have been studied by theoretical calculation. They can function as charge transport materials and emitters, with high efficiency and stability. To reveal the relationship between the structures and properties of these bifunctional or multifunctional electroluminescent materials, the ground and excited state geometries were optimized at the B3LYP/6-31G(d), HF/6-31G(d), and CIS/6-31G(d) levels, respectively. The ionization potentials (IPs) and electron affinities (EAs) were computed. The mobilities of hole and electron in these compounds were studied computationally based on the Marcus electron transfer theory. The lowest excitation energies, and the maximum absorption and emission wavelengths of these compounds were calculated by time-dependent density functional theory method. As a result of these calculations, the values of HOMO, LUMO, energy gaps, IPs, EAs, and the balance between the hole- and electron-transfer are greatly improved with the substitution of carbazole in compound 6. The calculated emission spectra of the seven studied molecules can almost cover the full UV-vis range (from 447.4 to 649.3 nm). Also, the Stokes shifts are unexpectedly large, ranging from 139.4 to 335.1 nm. This will result in the relatively long fluorescence lifetimes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
International Journal of Quantum Chemistry 02/2009; 109(7):1419 - 1429. · 1.36 Impact Factor
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Journal of Physical Organic Chemistry 12/2008; 22(7):680 - 690. · 1.96 Impact Factor
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ABSTRACT: Ambipolar diphenylamino end-capped oligofluorenylthiophenes and fluoroarene-thiophene show great potential for application in organic light-emitting diodes (OLEDs). Here, we provide an in-depth investigation on the optical and electronic properties of OF(2)TP-NPh ( 1a), OF(2)DTP-NPh ( 2a), OF(2)TTP-NPh ( 3a), OF(2)QTP-NPh ( 4a), and 2,5-bis-(2,3,5,6-tetrafluoro-4-trifluoromethyl-phenyl)-2,2':5',2'':5'',2'''-quaterthiophene ( 5a). The geometric and electronic structures of the oligomers in the ground-state are studied with density functional theory (DFT) and ab initio Hartree-Fock, whereas the lowest singlet excited states are optimized by ab initio CIS. The energies of the lowest singlet excited states are calculated by employing time-dependent density functional theory (TDDFT). The results show that the highest occupied molecular orbitals, lowest unoccupied molecular orbitals, energy gaps, ionization potentials, and electron affinities for the oligomers are affected by the thiophene chain length and the different end-caps. The absorption and emission spectra exhibit red shifts to some extent due to the increasing thiophene chain length and the enhancing electron-donating property of the end-caps. Furthermore, the large Stokes shifts ranging from 58 to 80 nm are examined, resulting from a more planar conformation of the excited-state between the two adjacent units in the oligomers. All the calculated data show that the fluoroarene-thiophene has improved electron transport rate and charge transfer balance performance, and all the studied molecules can be used as ambipolar-transporting materials in OLEDs.
The Journal of Physical Chemistry A 11/2008; 112(43):10904-11. · 2.95 Impact Factor
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ABSTRACT: The ground and excited state properties of luciferin (LH2) and oxyluciferin (OxyLH2), the bioluminescent chemicals in the firefly, have been characterized using density functional theory (DFT) and time dependent DFT (TDDFT) methods. The effects of solvation on the electronic absorption and emission spectra of luciferin and oxyluciferin were predicted with a self-consistent isodensity polarized continuum model of the solvent using TDDFT. The S0→S1 vertical excitation energies in the gas phase and in water were obtained. Optimizations of the excited state geometries permitted the first predictions of the fluorescence spectra for these biologically important molecules. Shifts in both of the absorption and emission spectra on proceeding from the gas phase to aqueous solution were also predicted.
Chinese Journal of Chemistry 01/2008; 26(1):55 - 64. · 0.75 Impact Factor
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ABSTRACT: The geometrical structure, electronic structure, one-photon and two-photon absorption properties of a series of macrocyclic thiophene derivatives C[3T_DA]n (n = 2–5) have been studied using density functional theory (DFT) and Zerner’s intermediate neglect of differential overlap (ZINDO) methods theoretically. The results showed that the range of λ(1)maxs is 390–470 nm and λ(2)maxs is 640–670 nm, while, both λ(1)max and λ(2)max gradually enlarge as increasing the number of the C[3T_DA] unit. And C[3T_DA]n compounds exhibited large TPA cross-section (δmax), and the factors influencing on the δmax values were analyzed in detail. Transition dipole moments M0k and Mkn play important roles on δmax. Both π-electron number (Ne) and the product of oscillator strengths from ground state to mediate state (ƒ0k) and from mediate state to final state (ƒkn) are in proportion to δmax. Moreover, δmax linearly depends on the static second-order nonlinear optical susceptibilities (β0).Highlights► The one- and two-photon absorption spectra, TPA transitions and TPA cross-sections of macrocyclic thiophene derivatives C[3T_DA]n (n = 2–5) have been explored in detail on basis of the stable π-conjugated structures using DFT combing with ZINDO and FTRNLO programs. ► Since their one- and two-photon absorption spectra locate at different windows, they will have a potential application in the TPA dynamic therapy. ► Moreover, the TPA cross-section (δmax) of C[3T_DA]5 (8997.2GM) is about 18 times bigger than that of C[3T_DA]2, in which transition dipole moments (M0k, Mkn), π-electron number (Ne), the product of oscillator strengths (ƒ0k × ƒkn), static second-order nonlinear optical coefficient (β0), and the thiophene and acetylene unit in each compound all play important roles on the increasing of δmax. ► It is suggested that this series of macrocyclic thiophene derivatives will be candidates in practical two-photon materials.
Dyes and Pigments 91(2):248-257. · 3.13 Impact Factor
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ABSTRACT: Firefly bioluminescence has attracted great attention for many years. Some details of the mechanism underlying firefly bioluminescence remain elusive. In this study the formation and decomposition reactions of firefly dioxetanone (DO) have been investigated in the gas phase and in a solvent model with an appropriate dielectric constant. Firefly DO is identified as a key intermediate. The formation of DO involves a stepwise reaction mechanism: first the formation of the four-membered ring on the singlet potential surface but not on the triplet and then the departure of the group. For the decomposition of DO, two possible reaction paths are proposed, one of which is reported for the first time.Graphical abstractThe formation and decomposition mechanism of firefly dioxetanone (see figure) are studied by M06 method in the gas phase and PCM solvent model.View high quality image (50K)Research highlights► This work reports the formation mechanism of dioxetanone, firstly. ► For the decomposition, one reaction path is proposed for the first time. ► The solvent effects were considered by using the PCM model.
Chemical Physics Letters 506:269-275. · 2.34 Impact Factor
